Mediastinal chest drain clearance for cardiac surgery

Abstract

Background

Cardiac tamponade may occur following cardiac surgery as a result of blood or fluid collecting in the pericardial space compressing the heart and reducing cardiac output. Mediastinal chest drains (including pericardial drains) are inserted as standard postoperative practice following cardiac surgery to assist the clearance of blood from the pericardial space. To prevent chest tubes from blocking and causing tamponade nurses manipulate them to prevent clots. Manipulation methods including milking, stripping, fanfolding and tapping may be applied to the tubes. Evidence is needed regarding the safest and most effective means of preventing chest tube blockage and cardiac tamponade.

Objectives

To compare different methods of chest drain clearance (i.e. varying levels of suction or suction in combination with milking, stripping, fanfolding and tapping of chest drains) in preventing cardiac tamponade in patients following cardiac surgery.

Search methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 3 2009), MEDLINE (1966 to October 2009), EMBASE (1980 to October 2009), CINAHL (1982 to October 2009) and the metaRegister of Controlled Trials (mRCT) (13 October 2009) and reference lists of articles. No language restrictions were applied.

Selection criteria

Randomised, quasi‐randomised or systematically allocated clinical trials of chest tube manipulation methods in adults and children with mediastinal chest drains following cardiac surgery.

Data collection and analysis

Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information where required. Adverse effects information was collected from the trials.

Main results

Three studies with a total of 471 participants were included. There was no data which could be included in a meta‐analysis. This was due to inadequate data provision by two of the studies. Where adequate data were provided there were no common interventions or outcomes to pool. On the basis of single studies there was no evidence of a difference between groups on incidence of chest tube blockage, heart rate, cardiac tamponade or incidence of surgical re‐entry.

Authors' conclusions

There are insufficient studies which compare differing methods of chest drain clearance to support or refute the relative efficacy of the various methods in preventing cardiac tamponade. Nor can the need to manipulate chest drains be supported or refuted by results from RCTs.

Plain language summary

Mediastinal chest drain clearance following cardiac surgery

Chest tubes are required following cardiac surgery to drain blood from around the heart. Blood around the heart can interfere with the function of the heart (cardiac tamponade) and result in more surgery and in extreme cases, death. To prevent chest tubes from blocking and so causing tamponade nurses manipulate them to prevent or remove clots. Manipulation may cause pain and discomfort for cardiac patients and rarely other adverse effects. This review found there was not enough evidence to say if one method of manipulation is better than another, or that manipulation is needed.

Background

Mediastinal chest drains (including pericardial drains) are inserted as standard post‐operative practice following cardiac surgery to assist the clearance of blood from the pericardial space and to prevent cardiac tamponade. Cardiac tamponade is a potentially life threatening complication that may arise after cardiac surgery. Cardiac tamponade results from blood or fluid collecting in the pericardial space compressing the heart and reducing cardiac output (Bloedel Smith 1996; Isaacson 1986; McLaughlin 1996). Drainage tubes, therefore, must remain clear and open to allow free flow of collected fluid. The mediastinal chest drainage system uses under‐water seal and low pressure suction to augment the drainage process. In addition to continuous low suction the tubes may be manipulated to enhance the drainage of fluid and to clear clots which form in the drainage system. Manipulation methods include milking, stripping, fanfolding and tapping. Milking, stripping and fanfolding increases the negative pressure of the system (Duncan 1982), which is believed to enhance drainage and clot clearance capabilities. The increased negative pressure, however, may be harmful. There has been one report of an avulsed coronary vein through the eyelets of a chest tube during stripping (Fishman 1983) and concern has been raised about the effects of increasing the pressure on the myocardium and on haemodynamic variables (Duncan 1987; Pierce 1991). Manipulation of chest tubes may cause pain and discomfort for cardiac patients.

The potential for harm resulting from chest tube manipulation needs to be balanced with the necessity to prevent clot formation in the tube from interfering with the drainage process. Evidence is required as to the safest and most effective means of preventing chest tube blockage and preventing cardiac tamponade. There appears to be no definitive evidence as to whether chest tube manipulation is more effective than suction alone or which form of manipulation should be used. Further there is no evidence as to whether tube manipulation should be applied routinely or only when tubes are blocked (Isaacson 1986; Lim‐Levy 1986; Pierce 1991). There does not even appear to be consensus regarding the definition of the various forms of manipulation. Stripping for instance may be done with the fingers (Isaacson 1986; Lim‐Levy 1986) or a hand held roller (Duncan 1987; Pierce 1991). Milking, on the other hand, is even less well defined and some authors include fanfolding as a milking method (Isaacson 1986; Lim‐Levy 1986) whilst another author refers to fanfolding as a type of stripping method (Duncan 1982). Information about the method involved in tube manipulation, for example the length of the tube which should be used in the manipulation, is not available or is inconsistent between authors (Bloedel Smith 1996; Isaacson 1986; McLaughlin 1996).

A systematic review of the research literature was indicated, given the lack of definitive guidelines for practice in this area of critical care.

Objectives

To compare different methods of chest drain clearance (i.e. varying levels of suction or suction in combination with milking, stripping, fanfolding and tapping of chest drains) in preventing cardiac tamponade in patients following cardiac surgery.

The impetus for this review arose in a children's hospital, so a subgroup analysis was planned for children to determine if there were differences in outcome which were relevant for children.

Methods

Criteria for considering studies for this review

Types of studies

Randomised, quasi‐randomised or systematically allocated clinical trials were included.

Types of participants

Adults and children with mediastinal chest drains following cardiac surgery were eligible for inclusion. A sub‐group analysis for children was to be completed if feasible.

Types of interventions

Studies were included if they compared:

• various levels of low pressure suction; or

• suction with chest tube manipulation methods (milking, tapping, fanfolding, stripping); or

• various means of chest tube manipulation; or

• any of the above with no intervention.

Definitions

There appears to be no consistency in the literature as to the definition of chest tube manipulation methods. For the purposes of this systematic review, the definitions given by the authors of included studies were categorised according to the following:

Stripping involves using either the fingers or a hand‐held roller to compress a length of tubing, moving proximally to distally whilst maintaining the compression. One hand grips the proximal tube with the thumb and forefinger and the other hand grips the tube immediately distally. The distal thumb and finger then apply firm constant pressure whilst moving along a length of tubing. Further lengths of tubing may be stripped by maintaining the pressure of the distal finger and thumb whilst the proximal hand moves immediately proximal and adjacent to the distal hand then the distal hand repeats the stripping action along the tube (Isaacson 1986; Pierce 1991). It is proposed that this action produces negative pressure which draws fluid and clots out of the chest.Milking is defined as compression of the tube using twisting or squeezing (sometimes hand‐over‐hand) to move fluid within the tube. Fanfolding involves folding sections of the tube over each other and squeezing. It is proposed that milking and fan folding produce some positive pressure during the twisting, squeezing or fanfolding/squeezing process followed by negative pressure when the tubing is released (Duncan 1982; Isaacson 1986; Lim‐Levy 1986; Pierce 1991). Tapping is a gentle rhythmical tapping of the chest tube with forceps to facilitate drainage of blood down the narrow section of the chest tube.

Types of outcome measures

Primary outcomes

• Incidence of cardiac tamponade ‐ early (in first eight hours);

• Incidence of cardiac tamponade ‐ late (after eight hours).

Secondary outcomes

• Incidence of chest tube blockage;

• Incidence of successful chest tube clearance;

• Incidence of suspicious alteration in chest tube drainage pattern;

• Incidence of indicators of impending cardiac tamponade e.g. decreasing blood pressure, increased left atrial pressure, increased pulmonary capillary wedge pressure, decreased cardiac output;

• Mortality ‐ all causes;

• Mortality ‐ cardiovascular events;

• Cardiovascular events;

• Incidence of re‐opening the chest for bleeding;

• Incidence of re‐opening the chest for tamponade;

• Incidence of postoperative atrial fibrillation;

• Incidence of significant pericardial effusion;

• Absolute volume of chest tube output;

• Other adverse events not specified above were recorded as was duration of follow up.

Search methods for identification of studies

Electronic searches

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library Issue 3 2009, MEDLINE (1966 to October 2009), EMBASE (1980 to October 2009), CINAHL (1982 to October 2009) and the metaRegister of Controlled Trials (mRCT) including the NIH ClinialTrials.gov register at www.controlled-trials.com/mrct/ (13 October 2009).

The search strategies for these databases can be viewed in Appendix 1, Appendix 2 and Appendix 3.

No language restrictions were applied.

Searching other resources

The reference lists of relevant studies were also searched to identify any other published or unpublished works, conference presentations or personal communication that were relevant to the review topic.

Data collection and analysis

Selection of studies

The above search strategy identified a set of potentially relevant references (title/abstracts). These references were assessed independently by two reviewers (MW, AM) according to the selection criteria to determine which were suitable for data extraction. Full articles were obtained where a judgement was unable to be made from the title/abstract or when consensus could not be reached. The articles were then assessed independently by two reviewers (MW, AM) according to the selection criteria to determine which were to be suitable for data extraction. Differences were resolved by consensus or by referral to a third member of the team (DG). Non‐English language articles were eligible for selection.

A standard data extraction form was devised and piloted. Data were then extracted independently by two reviewers (MW, AM) and results compared. If differences existed they were resolved either by consensus or by referral to a third member of the team (DG). If data were missing or further information required, concerted attempts were made to contact the authors to request the required information.

In addition to extracting data, the reviewers independently allocated each trial into one of three quality categories, based on those described in the Cochrane Reviewers' Handbook (Alderson 2003). That is,
Category A: Low risk of bias ‐ plausible bias unlikely to seriously alter the results; Category B: Moderate risk of bias ‐ plausible bias that raises some doubt about the results;Category C: High risk of bias ‐ plausible bias that seriously weakens confidence in the results. Differences in allocation of studies into quality categories were resolved either by consensus or by referral to a third member of the team.

Dealing with missing data

Where published data from an included study was incomplete and could not be obtained from the author (for example variances not available) the results are given descriptively.

Data synthesis

Analysis was approached as follows :

• Dichotomous outcomes: an odds ratios and its 95% confidence interval were used.

• Continuous data: the weighted mean difference and its 95% confidence interval were estimated.

Subgroup analysis and investigation of heterogeneity

A subgroup analysis on children was not possible as no data for children existed.

Heterogeneity was not an issue as there were no studies with adequate data to pool.

Results

Description of studies

Results of the search

Flow diagram for initial version of the review (2002)

Potentially relevant publications/abstracts identified: 992
Of these, 985 papers were then excluded on the basis of title and abstract (residual = seven)
These seven papers were retrieved for more detailed evaluation.
Of these seven papers, four were excluded (compared ineligible interventions = three; non‐randomised study = one). Thus there were three RCTs which were eligible for inclusion in the 2002 review (Isaacson 1986; Lim‐Levy 1986; Pierce 1991).

Flow diagram for the updated version of the review (2004)

Potentially relevant publications/abstracts identified:1944
Of these 1944 papers all were then excluded on the basis of title and abstract or that they were retrieved in the 2002 review.
A systematic review of the nursing management of chest drains (Charnock 2001) was identified and its reference list checked, one potentially relevant reference was identified, but on retrieving the article it was found to be ineligible for inclusion (Oakes 1993).
No new studies were identified.

Flow diagram for the updated version of the review (2007)

Potentially relevant publications/abstracts identified: 829

456 records were duplicates of previous searches, or between databases. The titles and abstracts of the remaining 373 records were checked and excluded as being not relevant to this review.

Flow diagram for the updated version of the review (2009)

Potentially relevant publications/abstracts identified: 636

453 were duplicates of previous searches or between the databases. The titles and abstracts of the remaining 183 records were checked and excluded as being not relevant to this review. Two ongoing trials have been identified (Demers 2008; Milliken 2006).

Included studies

Three studies (471 participants) were included, see Characteristics of included studies. Of the three studies there was no data which could be included in a meta‐analysis. This was due to inadequate data provision by two of the studies (Isaacson 1986; Lim‐Levy 1986). Contact was made with both these authors but neither were able to provide any additional data. In addition, where adequate data were provided there were no common interventions or outcomes to pool.

Isaacson 1986 studied 211 participants, comparing fanfolding with stripping and measuring volume of drainage and numbers of deaths. The data from this study could not be included in a meta‐analysis because no variance was provided for the continuous variable (amount of drainage) and the mortality data (n=3) was not presented by experimental group. Although the author was contacted, she was unable to provide the missing data.

Lim‐Levy 1986 studied 60 participants comparing routine stripping or fanfolding with a control group which received standard suction pressure but no tube manipulation. This report did not provide variance for variables using continuous data (8‐hour drainage volume and heart rate over study period). There were two other binary outcomes: incidence of tube blockage and incidence of arrhythmias. The data for incidence of arrhythmias was not reported by group and therefore could not be included. Although the author was contacted, she was unable to provide the missing data.

The other included study of 200 adults following myocardial revascularization surgery compared milking and stripping (Pierce 1991). Milking or stripping was instituted once a clot was evident and ceased once the clot was removed. This study measured a number of variables and provided adequate data for these.

Excluded studies

See Characteristics of excluded studies.

Risk of bias in included studies

The included studies were categorised into one of three quality categories, based on those described in the Cochrane Reviewers' handbook version 4.0 (section 6.7.1, page 39). They were as follows:
Pierce 1991 ‐ low risk of bias.
Lim‐Levy 1986 ‐ moderate risk of bias. This was due to a drop out rate of 18.3% (11 of n = 60). In particular group assignment was not adhered to for seven of these 11 participants; the reasons and initial group allocation were not provided.
Isaacson 1986 ‐ moderate risk of bias. Alternate allocation, blinding unclear, each group has unequal proportions of participants who received ‐5 and ‐20 mm H₂O of suction.

Effects of interventions

Incidence of cardiac tamponade

Pierce 1991 was the only study which examined this outcome (stripping vs milking) and follow up was only to 8 hours (Analysis 4.1). There was one participant who was reported to tamponade in the milking group and none in the stripping group (n=100 in both groups). The one occasion of tamponade, however, was referred to as a questionable diagnosis and was not confirmed on X‐ray.

4.1. Analysis.

Comparison 4: Stripping versus Milking, Outcome 1: Incidence of cardiac tamponade

Incidence of chest tube blockage

Lim‐Levy 1986 was the only study measuring this outcome. There was no incidence of chest tube blockage in either of the 3 groups (Analysis 1.1; stripping, fanfolding and control with n=16, 18, 15 respectively).

1.1. Analysis.

Comparison 1: Stripping versus control, Outcome 1: Incidence of chest tube blockage

Heart rate

Pierce 1991 was the only study to collect data for this variable (for 64% of sample; mean change in response to manipulation, measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in heart rate as a response to manipulation (Analysis 4.5; stripping: mean change = 0.6 b/min, SD = 3.12; milking: mean change = 0.2 b/min, SD = 4.06). Lim‐Levy 1986 reported no statistical difference between fanfolding, stripping and control groups (X= 90, 95 and 92 b/min respectively) for overall heart rate but did not report variance nor the statistics for the test of significance.

4.5. Analysis.

Comparison 4: Stripping versus Milking, Outcome 5: Heart rate ‐ mean change in response to manipulation

Systolic pressure

Pierce 1991 was the only study to collect data for this variable (for 64% of sample; mean change in response to manipulation, measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in systolic pressure as a response to manipulation (Analysis 4.6; stripping: mean change = 0.4mmHg, SD = 7.03; milking: mean change = 0.4mmHg, SD = 8.12).

4.6. Analysis.

Comparison 4: Stripping versus Milking, Outcome 6: Systolic pressure ‐ mean change in response to manipulation

Diastolic pressure

Pierce 1991 was the only study to collect data for this variable (for 64% of sample; mean change in response to manipulation, measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in diastolic pressure as a response to manipulation (Analysis 4.7; stripping: mean change = ‐0.1 mmHg, SD = 3.91; milking: mean change = 0.2 mmHg, SD = 4.87).

4.7. Analysis.

Comparison 4: Stripping versus Milking, Outcome 7: Diastolic pressure ‐ mean change in response to manipulation

Mean arterial pressure

Pierce 1991 was the only study to collect data for this variable (for 64% of sample; mean change in response to manipulation (measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in mean arterial pressure as a response to manipulation (Analysis 4.8; stripping: mean change = ‐0.4 mmHg, SD = 7.81; milking: mean change = 1.5 mmHg, SD = 9.75).

4.8. Analysis.

Comparison 4: Stripping versus Milking, Outcome 8: Mean arterial pressure ‐ mean change in response to manipulation

Right atrial pressure

Pierce 1991 was the only study to collect data for this variable (for 13% of sample; mean change in response to manipulation (measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in right atrial pressure as a response to manipulation (Analysis 4.9; stripping: mean change = ‐0.2 mmHg, SD = 0.92; milking: mean change = ‐0.1 mmHg, SD = 0.98). NB: Data from very few participants are presented.

4.9. Analysis.

Comparison 4: Stripping versus Milking, Outcome 9: Right atrial pressure ‐ mean change in response to manipulation

Left atrial pressure

Pierce 1991 was the only study to collect data for this variable (for 61% of sample; mean change in response to manipulation (measured prior to and following each tube manipulation episode). There was no difference between the stripping and milking groups (administered as required) in the amount of change in left atrial pressure as a response to manipulation (Analysis 4.10; stripping: mean change = ‐0.1 mmHg, SD = 0.77; milking: mean change = ‐0.1 mmHg, SD = 0.79).

4.10. Analysis.

Comparison 4: Stripping versus Milking, Outcome 10: Left atrial pressure ‐ mean change in response to manipulation

Chest X‐ray for cardiac tamponade

Pierce 1991 was the only study which examined this outcome (stripping versus milking; duration of follow up = eight hours). There was no incidence of cardiac tamponade in either group, based on radiological examination (Analysis 4.2).

4.2. Analysis.

Comparison 4: Stripping versus Milking, Outcome 2: Chest xray for cardiac tamponade

Incidence of surgical re‐entry

Pierce 1991 was the only study which examined this outcome (stripping versus milking; duration of follow up = eight hours). Each group had three participants who required surgical re‐entry (n=100 in each group; Analysis 4.3).

4.3. Analysis.

Comparison 4: Stripping versus Milking, Outcome 3: Incidence of surgical re‐entry

Volume of chest tube output at eight hours

Pierce 1991 was the only study which included this outcome (stripping versus milking) and also provided enough data to examine. There was no difference between groups (Analysis 4.4; stripping: 515.8ml, SD = 311mL; milking: 541.6mL, SD = 380mL; WMD = ‐25.80; 95%CI fixed = ‐122.04,70.44). Isaacson 1986 reported no statistical difference between fanfolding and stripping groups (898mL and 841mL, respectively) but did not report variance, nor the statistics for the test of significance. Lim‐Levy reported significantly higher drainage in the stripping (vs fanfolding and control) group between four and eight hours graphically but did not report the actual data

4.4. Analysis.

Comparison 4: Stripping versus Milking, Outcome 4: Volume of chest tube output at 8 hours

Two other important variables were recorded but data was not given by group (i.e. death ‐ Isaacson 1986; incidence of arrhythmias ‐ Lim‐Levy 1986).

Discussion

The purpose of this review was to compare different methods of chest drain clearance (i.e. varying levels of suction or suction in combination with milking, stripping, fanfolding and tapping of chest drains) in preventing cardiac tamponade in patients following cardiac surgery. Only three studies were eligible for inclusion, and of these, data were only available from two studies to include in a meta‐analysis. In addition, these studies had no common interventions or outcomes which could be pooled in a meta‐analysis. No significant differences were reported for any of the outcomes across any of the interventions, except Lim‐Levy 1986 who reported (but did not provide data) that the stripping group had a greater drainage volume than the fanfolding or control group.

There is no real evidence, therefore, to make any conclusions regarding the efficacy of one type of chest tube manipulation compared to another. There was no difference in the incidence of chest tube blockage or heart rate when stripping and fanfolding methods were compared (Lim‐Levy 1986) or in the incidence of cardiac tamponade or surgical re‐entry when milking and stripping were compared (Pierce 1991). The strongest of the three included studies by Pierce (Pierce 1991) had a low risk of bias, total subject numbers of 200 and concluded that there is no difference between milking and stripping in benefit or harm to patients. Pierce, however, followed up patients for only eight hours and manipulation was provided as a clot became evident. There is a need for more methodologically rigorous studies to be done in this area.

There is no evidence, in fact, as to whether there is a need to manipulate chest drains at all. Although Lim‐Levy 1986 included a control group, the study was considered to have a moderate risk of bias, it only reported frequency of tube occlusion and gave some information about differences in the amount of drainage between groups. It has been reported that tube manipulation increases negative pressure (Duncan 1982) and that this excessive pressure may be detrimental. Also, chest tube manipulation can be a painful procedure in patients following cardiac surgery. Therefore, as chest tube manipulation is a commonly used practice which may be associated with adverse events there seems an imperative to conduct research which tests the need for chest tube manipulation techniques compared to a control group in large, methodologically rigorous studies.

There are a number of considerations in doing the suggested research. Firstly, the definition of tube manipulation in the studies needs to be explicit and objective. As pointed out in the background to this review there is not a clear and universal definition for the various procedures. This was also evident in the included studies. For example, Isaacson 1986 and Lim‐Levy 1986 reported they used milking as one chest tube manipulation method. In both these studies milking included a description of fanfolding methods. Pierce 1991, however, described their milking intervention as involving a "twisting or squeezing motion" (p126). In addition to comparing various means of tube clearance there is potential to compare routine versus "as needs" intervention. Isaacson 1986 and Lim‐Levy 1986 for instance followed a protocol of routine clearance whereas in Pierce 's study tubes were manipulated when a clot became evident. Finally, future research would benefit by collecting comprehensive, well‐defined, reliable, valid and longer term outcomes. Cardiac tamponade, indicators of impending cardiac tamponade, and the need for surgical re‐entry and other interventions need to be measured. Follow up should extend past the critical phase to ensure adequate collection of outcomes. The value of measuring volume of drainage needs to be carefully considered.

A secondary objective of this review was to analyse the results for children. There were, however, no studies including children. The size of the tubes used with children may necessitate different management strategies in response to clot clearance and the negative pressures generated. The research recommended above (i.e.. comparing different methods of chest drain clearance with each other and with a control, and manipulating tube on an as‐required versus routine basis) is recommended for children also.

Authors' conclusions

Implications for practice.

There are insufficient studies which compare differing methods of chest drain clearance to support or refute the relative efficacy of the various methods in preventing cardiac tamponade. Nor can the need to manipulate chest drains be supported or refuted by results from RCT's.

Implications for research.

Studies are needed that adequately define chest drain manipulation, compare methods applied either routinely or as required, compare methods with each other and with a control and include adequate outcomes followed up past the acute phase. Other forms of drainage could also be compared with standard chest drains in prevention of complications following cardiac surgery, for example redon catheters (Farhat 2003), flexible fluted silicon drains (Akowuah 2002) and phosphatidylcholine‐coated chest tubes (Hunter 1993).

What's new

Date	Event	Description
11 February 2021	Review declared as stable	The review question is no longer considered an area of uncertainty and the editorial decision was taken not to update this review.

History

Protocol first published: Issue 2, 2001
Review first published: Issue 2, 2002

Date	Event	Description
24 May 2010	New search has been performed	Third update. Searches were re‐run in October 2009. No new studies were identified. The conclusion remains unchanged.
17 March 2008	New search has been performed	Second update. Searches were carried out in June 2007.  Three hundred and seventy‐three citations were screened but no new studies were identified for inclusion. The reviewers’ conclusions remain unchanged.
14 February 2008	Amended	Converted to new review format.
8 November 2003	New search has been performed	First update (published issue 4, 2004). 1944 potentially relevant papers were found, all were excluded and conclusions were unchanged.

Appendices

Appendix 1. Search strategies 2009

CENTRAL on THE Cochrane Library

#1 MeSH descriptor Chest Tubes this term only
#2 MeSH descriptor Drainage this term only
#3 (mediasti* in All Text near/6 drain* in All Text)
#4 (mediasti* in All Text near/6 tub* in All Text)
#5 (drain* in All Text near/6 tub* in All Text)
#6 (drain* in All Text near/6 chest* in All Text)
#7 (chest in All Text near/6 tub* in All Text)
#8 thorax next drain* in All Text
#9 surgical next drainage in All Text
#10 (#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 or #9)
#11 MeSH descriptor Cardiac Surgical Procedures explode all trees
#12 MeSH descriptor Thoracic Surgery this term only
#13 myocard* in All Text
#14 heart* in All Text
#15 pericard* in All Text
#16 cardiac in All Text
#17 coronary in All Text
#18 (#11 or #12 or #13 or #14 or #15 or #16 or #17)
#19 (#10 and #18)

MEDLINE on Ovid

1 Chest tubes/
2 Drainage/
3 (mediasti$ adj25 drain$).mp.
4 (mediasti$ adj25 tub$).mp.
5 (drain$ adj25 tub$).mp.
6 (chest adj25 drain$).mp.
7 (chest adj25 tub$).mp.
8 (thoracic adj5 (drain$ or tub$)).tw.
9 or/1‐8
10 exp Cardiac surgical procedures/
11 myocard$.tw.
12 pericard$.tw.
13 cardiac.tw.
14 heart.tw.
15 coronary.tw.
16 or/10‐15
17 9 and 16
18 randomized controlled trial.pt.
19 controlled clinical trial.pt.
20 Randomized controlled trials/
21 random allocation/
22 double blind method/
23 single‐blind method/
24 or/18‐23
25 exp animal/ not humans/
26 24 not 25
27 clinical trial.pt.
28 exp Clinical Trials as Topic/
29 (clin$ adj25 trial$).ti,ab.
30 ((singl$ or doubl$ or trebl$ or tripl$) adj (blind$ or mask$)).ti,ab.
31 placebos/
32 placebo$.ti,ab.
33 random$.ti,ab.
34 research design/
35 or/27‐34
36 35 not 25
37 36 not 26
38 comparative study.pt.
39 exp evaluation studies/
40 follow up studies/
41 prospective studies/
42 (control$ or prospectiv$ or volunteer$).ti,ab.
43 or/38‐42
44 43 not 25
45 44 not (26 or 37)
46 26 or 37 or 45
47 17 and 46
48 (2007$ or 2008$ or 2009$).em.
49 47 and 48

EMBASE on Ovid

1 tube/
2 thorax drainage/
3 (mediastin$ adj25 drain$).tw.
4 (mediastin$ adj25 tub$).tw.
5 (drain$ adj25 tub$).tw.
6 (chest$ adj25 drain$).tw.
7 (chest$ adj25 tub$).tw.
8 (thoracic adj5 (drain$ or tub$)).tw.
9 or/1‐8
10 exp heart surgery/
11 thorax surgery/
12 myocard$.tw.
13 pericard$.tw.
14 cardiac.tw.
15 heart.tw.
16 coronary.tw.
17 or/10‐16
18 9 and 17
19 controlled clinical trial/
20 random$.tw.
21 randomized controlled trial/
22 follow‐up.tw.
23 double blind procedure/
24 placebo$.tw.
25 placebo/
26 factorial$.ti,ab.
27 (crossover$ or cross‐over$).ti,ab.
28 (double$ adj blind$).ti,ab.
29 (singl$ adj blind$).ti,ab.
30 assign$.ti,ab.
31 allocat$.ti,ab.
32 volunteer$.ti,ab.
33 Crossover Procedure/
34 Single Blind Procedure/
35 or/19‐34
36 (exp animals/ or nonhuman/) not human/
37 35 not 36
38 37 and 18
39 (2007$ or 2008$ or 2009$).em.
40 38 and 39

CINAHL on EBSCO

S3 (S1 and S2)
S2 ( (MH "Heart Surgery+") or (MH "Thoracic Surgery") or myocard* or pericard* or cardiac or heart or coronary ) and ( (MH "Chest Tubes") or (MH "Closed Drainage") or (thoracic* N25 tub* or thoracic* N25 drain*or mediastin* N25 drain or mediastin* N25 tub* or drain* N25 tub* or chest N25 drain* or chest N25 tub*) )
S1 (MH "Clinical Trials+") or random* or trial or clinical study or groups or double blind or single blind or triple blind

Appendix 2. Search strategies 2007

CENTRAL on The Cochrane Library

#1 MeSH descriptor CHEST TUBES explode all trees  
#2 MeSH descriptor DRAINAGE explode all trees
#3 (mediasti*  near/6 drain* ) 
#4 (mediasti*  near/6 tub* )
#5 (drain*  near/6 tub* ) 
#6 (drain*  near/6 chest* ) 
#7 (chest  near/6 tub* ) 
#8 thorax next drain* 
#9 surgical next drainage 
#10 (#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 or #9) 
#11 MeSH descriptor CARDIAC SURGICAL PROCEDURES explode all trees 
#12 MeSH descriptor THORACIC SURGERY explode all trees 
#13 myocard* 
#14 heart* 
#15 pericard* 
#16 cardiac 
#17 coronary 
#18 (#11 or #12 or #13 or #14 or #15 or #16 or #17)
#19 (#10 and #18)

MEDLINE on Ovid

1     Chest tubes/
2     Drainage/
3     (mediasti$ adj25 drain$).mp.
4     (mediasti$ adj25 tub$).mp.
5     (drain$ adj25 tub$).mp.
6     (chest adj25 drain$).mp.
7     (chest adj25 tub$).mp.
8     (thoracic adj5 (drain$ or tub$)).tw.
9     or/1‐8
10     exp Cardiac surgical procedures/
11     myocard$.tw.
12     pericard$.tw.
13     cardiac.tw.
14     heart.tw.
15     coronary.tw.
16     or/10‐15
17     9 and 16
18     randomized controlled trial.pt.
19     controlled clinical trial.pt.
20     Randomized controlled trials/
21     random allocation/
22     double blind method/
23     single‐blind method/
24     or/18‐23
25     exp animal/ not humans/
26     24 not 25
27     clinical trial.pt.
28     exp Clinical trials/
29     (clin$ adj25 trial$).ti,ab.
30     ((singl$ or doubl$ or trebl$ or tripl$) adj (blind$ or mask$)).ti,ab.
31     placebos/
32     placebo$.ti,ab.
33     random$.ti,ab.
34     research design/
35     or/27‐34
36     35 not 25
37     37 not 27
38     comparative study.pt.
39     exp evaluation studies/
40     follow up studies/
41     prospective studies/
42     (control$ or prospectiv$ or volunteer$).ti,ab.
43     or/38‐42
44     43 not 25
45     44 not (26 or 37)
46     26 or 37 or 45
47     17 and 46
48     limit 47 to yr="2003 ‐ 2007"

EMBASE on Ovid

1     tube/
2     thorax drainage/
3     (mediastin$ adj25 drain$).tw.
4     (mediastin$ adj25 tub$).tw.
5     (drain$ adj25 tub$).tw.
6     (chest$ adj25 drain$).tw.
7     (chest$ adj25 tub$).tw.
8     (thoracic adj5 (drain$ or tub$)).tw.
9     or/1‐8
10     exp heart surgery/
11     thorax surgery/
12     myocard$.tw.
13     pericard$.tw.
14     cardiac.tw.
15     heart.tw.
16     coronary.tw.
17     or/10‐16
18     9 and 17
19     clinical trial/
20     random$.tw.
21     randomized controlled trial/
22     trial$.tw.
23     follow‐up.tw.
24     double blind procedure/
25     placebo$.tw.
26     placebo/
27     factorial$.ti,ab.
28     (crossover$ or cross‐over$).ti,ab.
29     (double$ adj blind$).ti,ab.
30     (singl$ adj blind$).ti,ab.
31     assign$.ti,ab.
32     allocat$.ti,ab.
33     volunteer$.ti,ab.
34     Crossover Procedure/
35     Single Blind Procedure/
36     or/19‐35
37     exp animal/ not exp human/
38    36 not 37
39     18 and 38
40     limit 39 to yr="2003 ‐ 2007"

CINAHL on Ovid

1     Chest tubes/
2     Drainage/
3     Closed Drainage/
4     (mediasti$ adj25 drain$).mp.
5     (mediasti$ adj25 tub$).mp.
6     (drain$ adj25 tub$).mp.
7     (chest adj25 drain$).mp.
8     (chest adj25 tub$).mp.
9     (thoracic adj5 (drain$ or tub$)).tw.
10     or/1‐9
11    exp Heart Surgery/
12     myocard$.tw.
13     pericard$.tw.
14     cardiac.tw.
15     heart.tw.
16     coronary.tw.
17     or/11‐16
18     10 and 17
19     Randomized controlled trials/
20     clinical trial.pt.
21     exp Clinical trials/
22     (clin$ adj25 trial$).ti,ab.
23     ((singl$ or doubl$ or trebl$ or tripl$) adj (blind$ or mask$)).ti,ab.
24     placebos.sh.
25     placebo$.ti,ab.
26     random$.ti,ab.
27     exp evaluation studies/
28     prospective studies.sh.
29     (control$ or prospectiv$ or volunteer$).ti,ab.
30     or/19‐29
31     18 and 30
32     limit 31 to yr="2003 ‐ 2007"

Appendix 3. Search strategies 2003

CENTRAL on The Cochrane Library

#1 CHEST TUBES explode all trees (MeSH)
#2 (chest next tub*)
#3 CHEST TUBES explode all trees (MeSH)
#4 (chest next drain*)
#5 DRAINAGE explode all trees (MeSH)
#6 (mediastin* next tub*)
#7 (mediastin* next drain*)
#8 (drain* next adj25 next tub*)
#9 (#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8)
#10 THORACIC SURGERY explode all trees (MeSH)
#11 THORACIC SURGICAL PROCEDURES explode all trees (MeSH)
#12 myocard*
#13 pericard*
#14 cardiac
#15 heart
#16 coronary
#17 (#8 or #9 or #10 or #11 or #12 or #13 or #14 or #15 or #16)
#18 (#9 and #17)

MEDLINE

1 chest tubes.mp. or exp Chest Tubes/ (634)
2 chest tub$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (1185)
3 exp Chest Tubes/ or chest drain.mp. (562)
4 chest drain$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (259)
5 drainage.mp. or DRAINAGE/ (14091)
6 (mediasti$ adj25 drain$).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (437)
7 (mediasti$ adj25 tub$).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (478)
8 (drain$ adj25 tub$).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (1646)
9 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 (15337)
10 thoracic surgery.mp. or exp Thoracic Surgery/ (1972)
11 cardiac surgery.mp. or exp Thoracic Surgery/ (5902)
12 myocard$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (82868)
13 pericar$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (6879)
14 cardiac.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (79053)
15 heart.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (120134)
16 coronary.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (60799)
17 exp Cardiac Surgical Procedures/ or cardiac surgical techniques.mp. (38250)
18 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 (226556)
19 9 and 18 (1566)
20 randomized controlled trial.mp. or Randomized Controlled Trials/ (25564)
21 exp Randomized Controlled Trials/ or randomised controlled trial.mp. (22761)
22 meta‐analysis.mp. or exp Meta‐Analysis/ (7981)
23 "Controlled Clinical Trial [Publication Type]"/ (0)
24 "Clinical Trial [Publication Type]"/ (0)
25 random$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (161756)
26 (meta‐anal$ or metaanaly$ or meta analy$).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (9206)
27 ((doubl$ or single$) and blind$).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (30393)
28 clinical trials.mp. or exp Clinical Trials/ (70882)
29 crossover.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (8644)
30 clini$ trial$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (39671)
31 (control$ and (trial$ or stud$)).mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (302139)
32 placebo$.mp. [mp=title, abstract, cas registry/ec number word, mesh subject heading] (36448)
33 research design.mp. or exp Research Design/ (78241)
34 Comparative Study/ (341531)
35 20 or 21 or 22 or 25 or 26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 (748894)
36 19 and 35 (365)

EMBASE

1 chest tubes.mp. or exp Tube/ (6239)
2 chest tub$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (886)
3 exp thorax drainage/ or chest drain.mp. (1335)
4 chest drain$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (232)
5 drainage.mp. (12544)
6 (mediasti$ adj25 drain$).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (378)
7 (mediasti$ adj25 tub$).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (456)
8 (drain$ adj25 tub$).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (1549)
9 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 (19835)
10 thoracic surgery.mp. or exp Thorax Surgery/ (64119)
11 cardiac surgery.mp. or exp Heart Surgery/ (43986)
12 myocard$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (54426)
13 pericar$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (6309)
14 cardiac.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (78635)
15 heart.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (110921)
16 coronary.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (60945)
17 10 or 11 or 12 or 13 or 14 or 15 or 16 (234433)
18 9 and 17 (4011)
19 Randomized Controlled Trial/ (66006)
20 Randomized Controlled Trial/ (66006)
21 randomized controlled trial.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (67401)
22 randomised controlled trial.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (1634)
23 Meta Analysis/ (13759)
24 Clinical Trial/ (210296)
25 Clinical Trial/ (210296)
26 clinical trial$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (229974)
27 controlled clinical trial.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (1590)
28 random$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (154467)
29 (meta‐anal$ or metaanaly$ or meta analy$).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (16141)
30 ((doubl$ or single$) and blind$).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (31250)
31 crossover.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (8838)
32 clini$ trial$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (41238)
33 (control$ and (trial$ or stud$)).mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (703157)
34 placebo$.mp. [mp=title, abstract, subject headings, drug trade name, original title, device manufacturer, drug manufacturer name] (48358)
35 research design.mp. or Methodology/ (28998)
36 comparative study.mp. or Comparative Study/ (37022)
37 19 or 20 or 21 or 22 or 23 or 24 or 25 or 26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 or 35 or 36 (913626)
38 18 and 37 (978)

CINAHL

1 chest tubes.mp. or exp Chest Tubes/ (262)
2 chest tub$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (321)
3 exp Chest Tubes/ or chest drain.mp. (252)
4 chest drain$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (73)
5 exp DRAINAGE/ or drainage.mp. (1774)
6 (mediasti$ adj25 drain$).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (15)
7 (mediasti$ adj25 tub$).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (20)
8 (drain$ adj25 tub$).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (150)
9 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 (1988)
10 thoracic surgery.mp. or exp Thoracic Surgery/ (6329)
11 cardiac surgery.mp. or exp Heart Surgery/ (5115)
12 myocard$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (7754)
13 pericar$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (383)
14 cardiac.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (9137)
15 heart.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (14865)
16 coronary.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (6257)
17 exp Heart Surgery/ or cardiac surgical techniques.mp. (4877)
18 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 (31016)
19 9 and 18 (311)
20 randomized controlled trial.mp. or exp Clinical Trials/ (21453)
21 randomised controlled trial.mp. (751)
22 meta‐analysis.mp. or exp Meta Analysis/ (3413)
23 controlled clinical trial.mp. or exp Clinical Trials/ (21240)
24 clinical trial.mp. or exp Clinical Trials/ (21855)
25 random$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (28726)
26 (meta‐anal$ or metaanaly$ or meta analy$).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (3541)
27 ((doubl$ or single$) and blind$).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (3282)
28 crossover.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (1019)
29 clini$ trial$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (4989)
30 (control$ and (trial$ or stud$)).mp. [mp=title, cinahl subject headings, abstract, instrumentation] (28896)
31 placebo$.mp. [mp=title, cinahl subject headings, abstract, instrumentation] (4912)
32 research design.mp. or exp Study Design/ (98261)
33 comparative study.mp. or exp Comparative Studies/ (21429)
34 20 or 21 or 22 or 23 or 24 or 25 or 26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 (129314)
35 19 and 34 (120)

Data and analyses

Comparison 1. Stripping versus control.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Incidence of chest tube blockage	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected

Comparison 2. Fanfolding versus Control.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Incidence of chest tube blockage	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected

2.1. Analysis.

Comparison 2: Fanfolding versus Control, Outcome 1: Incidence of chest tube blockage

Comparison 3. Stripping versus fanfolding.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Incidence of chest tube blockage	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected

3.1. Analysis.

Comparison 3: Stripping versus fanfolding, Outcome 1: Incidence of chest tube blockage

Comparison 4. Stripping versus Milking.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Incidence of cardiac tamponade	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected
4.2 Chest xray for cardiac tamponade	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected
4.3 Incidence of surgical re‐entry	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected
4.4 Volume of chest tube output at 8 hours	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.5 Heart rate ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.6 Systolic pressure ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.7 Diastolic pressure ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.8 Mean arterial pressure ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.9 Right atrial pressure ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
4.10 Left atrial pressure ‐ mean change in response to manipulation	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Isaacson 1986.

Study characteristics
Methods	Alternate allocation trial comparing stripping (by hand; n=100) and fanfolding (n=104). Chest drains: two Argyle No 28 mediastinal tubes at ‐5cm or ‐20cm H2O (allocation according to surgeons' preference). The stripping group had 43% at ‐5 and 57% at ‐20cm H2O, whilst the respective proportions for the milking group were 33% and 67%. Dropouts: 7 (3.3%) groups not specified. Three dropouts due to other interventions incompatible with study protocol, one patient was admitted to a unit other than CVICU and three patients died. Blinding: None
Participants	211 consecutive post‐operative cardiac patients who had open chest procedures requiring cardio‐ pulmonary bypass. 72.5% males, mean age 61 years (range 18 to 84 years). Setting: unspecified cardiovascular intensive care unit in the USA.
Interventions	The definition of milking and stripping met the protocol definitions. Both were done according to a fixed protocol, three times every 15 minutes for an hour, every 30 minutes for an hour, every hour for eight hours, then every two hours and then "as necessary".
Outcomes	Included outcomes: amount of drainage at eight hours, 12 hours and death from any cause. Excluded outcomes: amount of drainage at removal of tube as reason for tube removal is not comparable across studies. Outcome measures at eight hours, 12 hours and removal of tube. Length of follow up: Not specified but total volume was measured so presumably until at least tubes were removed.
Notes	Category B: Moderate risk of bias. The variances were not reported in this study. Contact was made with Isaacson but she was unable to locate the necessary data. Consequently no data from this study is able to be included in a meta‐analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	High risk	Inadequate

Lim‐Levy 1986.

Study characteristics
Methods	RCT comparing three groups: fanfolding (n=18), stripping (by hand; n=16) and no manipulation (control n=15). Chest drains used: Two x 36 French thoracic tubes, 39 participants had tubes into the left and right mediastinum, 14 had one in the right mediastinum and the other into the right pleural space. All were connected to a water seal drainage system with ‐20cm H2O suction. Dropouts: 11 (18.3%) participants were deleted from final analysis, groups not specified: three had incomplete data sets, one had concurrent surgical procedure and seven protocols were not adhered to. Blinding: unblinded.
Participants	60 adult males following CABG. Of 49 who completed the study: mean age was 58.73 (SD=7) years with no difference between groups in numbers of grafts, of length of time tubes were in situ. Exclusions: patients with concurrent procedures e.g. valve replacement and previous CABG. Setting: probably ICU the William S Middleton Memorial Veterans Hospital, Madison, Wisconsin, USA
Interventions	The definition of milking and stripping met those as defined in the protocol. Chest tube manipulation was done every two hours until tube removal.
Outcomes	Outcomes included: total volume (ml), frequency of tube occlusion, incidence of arrhythmias, average heart rate. Excluded outcomes: total volume (ml) drainage at tube removal. Outcomes were measured at 15 min intervals for the first 2 hours and hourly thereafter. Length of follow up: until tubes removed, average 43 hours, variance not given.
Notes	Category B: Moderate risk of bias. The variances were not reported in this study, nor was the data by group for incidence of arrhythmias. The author was unable to provide the necessary data. Consequently no data from this study is able to be included in a meta‐analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	High risk

Pierce 1991.

Study characteristics
Methods	RCT comparing milking (n=100), stripping (using hand held roller; n=100). Chest drains: not specified, suction was ‐25cm H2O. Dropouts: 8 (4%) aborted protocols, groups unspecified. Blinding: unblinded.
Participants	200 adults following myocardial revascularization surgery. Five also had valve replacement, one also had a left ventricular repair. Mean age = 62 years (range 35 to 86 years), 77.5% males Setting: Coronary ICU in hospital medical center probably Virginia Commonwealth University, USA.
Interventions	The definition of milking and stripping met those as defined in the protocol. Chest tubes were manipulated when a clot was evident and ceased when the clot was removed.
Outcomes	Outcomes included: total volume of drainage at 8 hours, number of manipulation episodes, chest x‐ray for tamponade, incidence of cardiac tamponade, surgery re‐entry, HR, RAP, LAP, systolic pressure, diastolic pressure, MAP. The latter 6 outcomes were measured immediately pre and post tube manipulation. Outcomes measurement: The physiologic parameters were measured at the bedside every hour and at five minute intervals from the computer records. Chest x‐ray was done at 0 hours and 4am after surgery. Length of follow up: eight hours.
Notes	Category A: Low risk of bias

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Duncan 1982	Measured different pressures generated by different methods of chest tube stripping not the outcome of clearance or prevention of cardiac tamponade.
Duncan 1987	Intervention did not meet selection criteria as the study did not compare tube manipulation or suction.
Graham 1992	Compared chest drainage systems not means of chest tube clearance.
Muirhead 1984	Groups were not randomly or quasi‐randomly assigned (were assigned according to surgeon).
Oakes 1993	Study of paediatric oncology patients undergoing thoracotomy not cardiac surgery so did not meet inclusion criteria.

Characteristics of ongoing studies [ordered by study ID]

Demers 2008.

Study name	Evaluation of different strategies of pericardial drainage after aortic valvular surgery: a prospective randomized trial
Methods	Allocation: randomized Control: dose comparison Endpoint classification: safety/efficacy study Intervention model: parallel assignment
Participants	Patients aged between 18 and 90 years old, undergoing either surgery of the ascending and/or transverse aorta, or surgery of the mitral and/or aortic valves Availability for follow‐up at the Montreal Heart Institute Exclusion criteria
Interventions	Experimental: Blake Drains (Blake drain, Ethicon USA) 19F Blake drain located in the posterior pericardial cavity Comparator: standard mediastinal drainage
Outcomes	Primary: any pericardial effusion of 15 mm or more as measured on postoperative transthoracic echocardiogram on day five and late cardiac tamponade requiring surgical reintervention. Secondary: total volume of mediastinal drainage. Pain intensity on postoperative days one to five. Incidence of postoperative atrial fibrillation drain‐associated infection or any other drain‐associated adverse event
Starting date	June 2008
Contact information
Notes

Milliken 2006.

Study name	A prospective, randomized, multicenter clinical study on the high vacuum body cavity drainage systems following open heart surgery
Methods	Allocation: randomized Control: active control Endpoint classification: safety/efficacy study Intervention Model: Parallel Assignment
Participants	Male or Female 18 year‐old or older Patients undergoing open heart surgery by means of a standard cardiopulmonary bypass
Interventions	Experimental: NO‐NUMO high vacuum body cavity drainage system Control: classic PVC chest tube
Outcomes	Primary: amount of postoperative bleeding Secondary: incidence of take‐backs for cardiac tamponade/excessive postoperative bleeding
Starting date	September 2006
Contact information
Notes

Contributions of authors

Margaret Wallen: Primary responsibility for coordinating review including preparing drafts of protocol and review, designing search strategy and conducting searches, accessing literature and screening it against selection criteria, managing RevMan and entering data, quality appraisal and data extraction, contacting authors for additional information. Prime responsibility for coordinating the 2004 revision, updating the 2007 version.

Anne Morrison: Conceiving the review, screening literature against selection criteria, quality appraisal and data extraction, primary expert involved in clinical feedback regarding protocol and review. Assisted with 2004 revision, updating the 2007 version.

Donna Gillies: Provided methodological advice and was involved in feedback on protocol and review, collaborated in developing search strategy, providing methodological perspective, data analysis, quality appraisal of papers and data extraction, updating the 2007 version.

Elizabeth O'Riordan: Provided expert methodological and clinical feedback to protocol and review

Catherine Bridge, Francis Stoddart: Provided expert clinical perspective to content of protocol and review.

Sources of support

Internal sources

• The Children's Hospital at Westmead, Australia

• Sydney West Area Health Service, Other

External sources

• No sources of support supplied

Declarations of interest

None known

Stable (no update expected for reasons given in 'What's new')