An assessment of common criteria for awake extubation in infants and young children

Abstract

Background:

Practice patterns surrounding awake extubation of pediatric surgical patients remain largely undocumented. This study assessed the value of commonly used predictors of fitness for extubation to determine which were most salient in predicting successful extubation following emergence from general anesthesia with a volatile anesthetic in young children.

Methods:

This prospective, observational study was performed in 600 children from 0-7 years of age. The presence or absence of 9 commonly used extubation criteria in children were recorded at the time of extubation including: facial grimace, eye opening, low end-tidal anesthetic concentration, spontaneous tidal volume >5 ml/kg, conjugate gaze, purposeful movement, movement other than coughing, laryngeal stimulation test, and oxygen saturation. Extubations were graded as Successful, Intervention Required, or Major Intervention Required using a standard set of criteria. The Intervention Required and Major Intervention Required outcomes were combined as a single outcome for analysis of predictors of success.

Results:

Successful extubation occurred in 92.7% (556/600) of cases. Facial grimace odds ratio (OR) 1.93 ([95%CI:1.03-3.60], p=0.039), purposeful movement OR 2.42 ([95%CI:1.14-5.12], p=0.022), conjugate gaze OR 2.10 ([95%CI:1.14-4.01], p=0.031), eye opening OR 4.44 ([95%CI:1.06-18.64], p=0.042), and tidal volume >5 ml/kg OR 2.66 ([95%CI:1.21-5.86], p=0.015) were univariately associated with the Successful group. A stepwise increase in any one, in any order, of these 5 predictors being present, from 1 out of 5, up to 5 out of 5 yielded an increasing positive predictive value for successful extubation of 88.3% [95%CI:82.4-94.3], 88.4% [95%CI:83.5-93.3], 96.3% [95%CI:93.4-99.2], 97.4% [95%CI:94.4-100], and 100% [95%CI:90-100].

Conclusion:

Conjugate gaze, facial grimace, eye opening, purposeful movement, and tidal volume >5 ml/kg were each individually associated with extubation success in pediatric surgical patients after volatile anesthetic. Further, the use of a multifactorial approach using these predictors, may lead to a more rational and robust approach to successful awake extubation.

Introduction

Induction and emergence remain two of the most critical times when caring for pediatric patients because of the increased risk of adverse events at these points of transition.^1-4 Interestingly, routine practice patterns surrounding awake extubation in children remain largely undocumented, and there exist few, if any studies to guide the clinician in managing awake extubation in pediatric patients following general anesthesia.

Most studies looking at predictors of successful extubation in children, defined as extubation without the need for prompt intervention or reintubation, have been retrospective cohort analyses of patients undergoing high-risk procedures such as cardiac surgery or liver transplantation.^5-7 Typically, these studies have centered around procedure-specific factors such as bypass time and amount of blood products transfused rather than more routine behavioral characteristics like eye opening or inhalation anesthetic level. Numerous other studies have focused on extubation in children in the neonatal or pediatric intensive care unit.^8-10 In all of these studies though, failure is most often a result of ongoing cardiopulmonary embarrassment and not simply a miscalculation of anesthetic depth at extubation. As a consequence, any insights garnered from them is likely to be of limited value in the setting of routine extubation in the operating room.

In more routine settings the extubation criteria used by clinicians can vary significantly and frequently reflect experience and training bias. Some clinicians have attempted to reduce the complexity of evaluating the timing of extubation by either extubating patients deep or deferring this decision to the recovery room. However, the clinician’s ability to correctly judge the optimal time to extubate a pediatric patient awake following inhalational anesthesia still remains essential.^11-13 Commonly used criteria for awake extubation in children include: eye opening, facial grimace, movement other than coughing, purposeful movement, conjugate gaze, and end tidal anesthetic concentration below a predetermined level.^14-16 Other criteria include adequate oxygenation, reversal of neuromuscular blockade, and the laryngeal stimulation test. A positive laryngeal stimulation test is defined as a return to spontaneous ventilation in < 5 s following gentle stimulation of the glottis by cephalad/caudad motion of the endotracheal tube in a patient ventilating spontaneously at emergence and is an indicator that the patient may have passed through Stage 2 and be ready to be extubated.⁴

At this point, most if not all of these criteria have not been validated beyond anecdotal experience, and it is unclear which, if any, is of greater importance as patients transition from deeper to lighter levels of inhalational anesthesia. Therefore, we performed a prospective, observational study to evaluate routine practice and the predictive value of various extubation criteria with the assertion that random overlap and variance in different clinicians’ practice would allow us to determine which factors individually or collectively are most important in the awake extubation of young pediatric patients emerging from inhalational anesthesia.

Methods

After IRB approval, we prospectively observed 600 pediatric awake extubations over the course of 10 months at our institution. Our institution is an academic tertiary care pediatric center where all pediatric surgical subspecialties are represented. All extubations were supervised by an attending anesthesiologist. All attendings except one were pediatric fellowship trained, and hailed from seven different training institutions in the United States creating a diversity of training biases. The one attending not fellowship trained completed a pediatric cardiology fellowship and anesthesia residency but not a pediatric anesthesia fellowship and has routinely cared for pediatric patients for > 20 years. Predictors of successful extubation that were used are summarized in Table 1 and were chosen based on the opinion and routine practice of the 9 pediatric anesthesiologists in our group. Further, we assumed that all 9 attending anesthesiologists present at our institution would potentially use different criteria based on their training bias or experience, with some attendings potentially choosing to use certain criteria in preference to others with attendant differences in successful extubation.

Table 1.

Catalogue of Predictors of Successful extubation in pediatric patients less than 7 years of age observed in this study.

1. Eye Opening

2. Facial Grimace

3. Patient Movement other than coughing

4. Conjugate Gaze

5. Purposeful Movement

6. End tidal anesthetic Less than:    Sevoflurane- 0.2%    Isoflurane – 0.15%    Desflurane 1.0%

7. Oxygen Saturation greater than 97%

8. Positive Laryngeal Stimulation Test

9. Tidal Volume greater than 5 cc/kg

Patients > 7 years of age were excluded, as were patients with a known difficult airway, tracheostomy in situ, patients anticipated to require postoperative mechanical ventilatory support immediately following their surgical procedure, and patients undergoing deep extubation. Deep extubation was defined as any extubation where the intent of the attending clinician was to extubate the patient at a deep plane of inhalational anesthesia where the patient’s airway reflexes have been ablated. Patients who underwent total intravenous anesthesia (TIVA), were maintained on propofol following inhalation induction, or who received a bolus dose of propofol electively prior to extubation were also excluded. Patients intubated with a nasotracheal tube were excluded due to potential issues of nasal bleeding and other known issues associated with a nasal endotracheal tube that might potentially confound or distort the data set. Emergency cases were not excluded so long as they did not meet other exclusionary criteria. To ensure some degree of randomness in age and case selection we attempted to capture as many consecutive cases as were available on a given day, but we were limited in some cases by availability of a research assistant or other demands extant in the continued delivery of care at our institution. All cases observed were performed during the normal operating room day schedule Monday through Friday from 7:00 to 18:00. We recorded demographic information on all patients including age, gender, weight, ASA status, and type of surgery. We also recorded the presence of a upper respiratory infection (URI). A URI was defined as any URI symptom including cough, cold, nasal drainage clear or otherwise, and/or associated fever within the past 7 days by observation on the day of surgery or parental history. The use of midazolam premedication and the presence or absence of asthma were also recorded.

At the time of emergence and extubation, an independent observer not directly involved in the care of the patient recorded the presence or absence of all 9 of the extubation criteria evaluated in the study. Tidal volumes were recorded directly from the anesthesia ventilator. The Aestiva (GE Healthcare, Chicago, IL, USA) and Perseus (Drager, Luebeck, Germany) anesthesia work stations were used for all patients. End tidal anesthetic levels and end tidal carbon dioxide (ETCO2) were measured using the GE gas analyzer module E-CAI0V-00 (GE Healthcare, Chicago, IL, USA) or the gas analysis module on the Perseus anesthesia work station. The highest measurement of ETCO2 within 10 s of extubation was recorded. Following extubation, the patient was assessed and the extubation was graded based on specific criteria and was assigned a value of successful (S), intervention required (IR), or major intervention required (MIR). Criteria for each group are summarized in Table 2. The intervention groups (IR and MIR) were combined for analysis a priori. The criteria chosen for the S, IR, and MIR groups were selected in an attempt to reflect clinically relevant events and outcomes.

Table 2.

Summary of criteria for grading extubation. Patients having any one of the following criteria will be assigned to the greatest intervention outcome based on independent observation of that patient’s extubation.

Successful (S)	Intervention Required (IR)	Major Intervention Required (MIR)
No oxygen desaturation below 92% or if the patient does desaturate it is for less than 30 seconds. Patient requires CPAP with 100% oxygen for less than 30 seconds	Oxygen desaturation below 92% for greater than 30 seconds but less than 1 minute. Patient requires CPAP with 100% oxygen for greater than 30 seconds but less than 2 minutes Patient has Inspiratory stridor but this does not lead to desaturation for greater than 1 minute or intervention beyond CPAP with 100% oxygen for less than 2 minutes	Oxygen desaturation less than 92% for greater than 1 minute. Patient requires CPAP with 100% oxygen for greater than 2 minutes Laryngospasm occurred according to attending clinician Urgent or Emergent administration of Propofol or Succinylcholine following extubation Breath holding or Apnea for greater than 10 seconds Reintubation

SpO2 =oxygen saturation; CPAP = Continuous Positive Airway Pressure.

Statistical Methods and Sample Size

Not knowing what the event rate would be, we chose an initial sample size of 300 patients to create a multivariable logistic regression model with 7 predictors. To ensure sufficient statistical power, we conducted an a priori interim analysis of event rates over the first 4 months of the study. This yielded a combined event rate of 6.9%. Given this event rate, we used the rule of 10 events per predictor variable in a logistic regression to revise the sample size and reduced the number of potential predictor variables to be included in the model to 4. Given this, we estimated that a sample size of 580 would be necessary (40/0.069=580 observations).^17,18 Rounding up we decided on a final sample size of 600.

Descriptive statistics were performed on all data, and between group differences for successful versus “intervention required” extubation were compared using two tailed, two sample, independent t tests for continuous and chi-square tests for categorical variables or Fisher’s exact tests if expected cell counts were less than five. The normality assumption within each group was assessed using both the Shapiro-Wilks test and by visually inspecting histograms or Q-Q plots, and all variables analyzed with t tests were verified to have met this assumption. An initial positive predictive value and odds ratio for success using a chi-square analysis was performed for each of the nine predictors with p < 0.05 considered significant. Variables that had a bivariate significant relationship with successful extubation were then entered into a multiple logistic regression model. The multiple logistic regression model resulted in complete separation of the data points, where the collection of predictors were perfectly able to separate the outcome groups. When complete separation occurs, maximum likelihood estimates do not exist, and thus odds ratios cannot be calculated. As a result, the multiple logistic regression results are not presented. Finally, the number of bivariate significant predictors present was totaled for each individual, and the relationship between the number of positive predictors and successful extubation was assessed.

Univariate chi-square analysis was also performed on the impact of URI, asthma, midazolam premedication in children ≥ 1 year of age, inhalation anesthetic choice, age < 1 year of age, use of nondepolarizing neuromuscular blocker, and airway procedure on unsuccessful extubation. In looking at the association of premedication with midazolam with the IR+MIR group we chose to analyze only patients > 1 year of age as the rate of premedication with midazolam in children < 1 year at our institution is exceedingly small and not comparable to its fairly routine clinical use in children ≥ 1 year of age. Lastly, a separate post-hoc analysis of ETCO2 and its association with the IR+MIR group was performed.

All statistical analyses were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC).

Results

Patients

We observed 600 extubations in children between the ages of 0 and 7 years of age. A summary of the types and prevalence of surgical procedures are presented in Table 3 with the most common cases being general surgery 154/600, (25.6%), airway surgery, 139/600, (23.1%) and urologic cases 116/600, (19.3%). All patients received intravenous intraoperative opioids. The dose and type were administered according to the routine practice of the clinicians caring for a given patient and were not dictated by the study protocol. There were no missing data points for any patient.

Table 3.

Summary of types of procedures and prevalence in patients extubated successfully (S) and those requiring intervention (IR+MIR).

Type of Surgical Procedure N=600	Number of Procedures For Each Type of Surgery (%)	Number of Patients with Successful Extubation (S)(%) N=556	Number of Patients Requiring Intervention (IR+MIR) (%) N=44
Airway procedures	139 (23.1)	130 (23.4)	9 (20.4)
Plastics and Head and Neck Surgery Not Involving the Airway	58 (9.7)	53 (9.7)	5 (9.1)
Orthopedic	61 (10.1)	56 (10.1)	5 (11.4)
General surgery	154 (25.6)	144 (25.9)	10 (22.7)
Urology	116 (19.3)	109 (19.6)	7 (15.9)
Ophthalmology	10 (1.7)	9 (1.6)	1 (2.3)
Neurosurgery	24 (4.0)	23 (4.1)	1 (2.3)
Other	38 (6.3)	32 (5.8)	6 (13.6)

Primary Results

The rate of successful extubation was 92.7% (556/600). The combined rate of extubations requiring intervention was 7.3% (44/600) (IR+MIR): 4.8% (29/600) (IR) plus 2.5% (15/600) (MIR). A univariate, chi-square analysis of 8 predictors and Fisher’s exact analysis of the remaining predictor used in the study yielded 5 predictors which were significantly associated with extubation success (see Table 4). These predictors were facial grimace, odds ratio 1.93 (OR) ([95%CI: 1.03–3.60]; p = 0.039), purposeful movement, OR 2.42 ([95%CI: 1.14–5.12], p = 0.022), conjugate gaze, OR 2.10 ([95%CI: 1.14–4.01], p = 0.031), eye opening, OR 4.44 ([95%CI: 1.06–18.64], p = 0.042), and tidal volume >5 ml/kg OR 2.66 ([95%CI: 1.21–5.86], p = 0.015). Additionally, a stepwise increase in any one of these 5 predictors in any order being present, from 1 out of 5, up to 5 out of 5 yielded an increasing positive predictive value for successful extubation of 88.3% [95%CI: 82.4–94.3], 88.4% [95%CI: 83.5–93.3], 96.3% [95%CI: 93.4–99.2], 97.4% [95%CI: 94.4–100], and 100.0% [95%CI: 90–100] (see Table 5).

Table 4.

Prevalence, positive predictive value, and univariate chi-square or Fisher’s exact analysis of 9 commonly used predictors of extubation success in pediatric surgical patients

Predictor of Successful Extubation	Prevalence of Predictor with Successful Extubation	Positive Predictive Value	95% CI of Positive Predictive Value	Odds Ratio for Successful Extubation	95% CI	P-Value for Chi-square Analysis
Facial grimace	0.56	0.95	0.97-0.92	1.93	1.03-3.60	0.039
Eye opening**	0.17	0.98	0.95-1.00	4.44	1.06-18.64	0.032
Conjugate gaze*	0.63	0.95	0.93-0.97	2.14	1.14-4.01	0.018
Low End Tidal Agent Concentration	0.31	0.93	0.91-0.95	1.07	0.55-2.09	0.848
Purposeful movement	0.37	0.96	0.93-0.99	2.42	1.14-5.12	0.022
Movement Other Than Coughing	0.77	0.92	0.90-0.94	0.85	0.40-1.82	0.677
Positive Laryngeal Stimulation Test†	0.88	0.92	0.90-0.95	0.91	0.47-1.75	0.313
Tidal volume > 5 ml/kg	0.92	0.94	0.91-0.96	2.66	1.21-5.86	0.015
SpO2 > 97%	0.92	0.93	0.91-0.95	2.05	0.87-4.88	0.102

^*N=535 because not all attendings checked for conjugate gaze in all patients

^†N=423 because not all attendings chose to check for a positive laryngeal stimulation test

^**Fisher’s Exact test was used instead of Chi-square because one of the cell counts was less than 5.

Table 5.

Positive predictive value of stepwise increase in number of 5 factors found to be significant using a univariate chi-square analysis for successful extubation.

Number of Univariate Predictors Present at extubation out of a possible 5	N=	Positive Predictive Value (%)	95% CI (%)
1 of 5	112	88.4	82.4-94.3
2 of 5	164	88.4	83.5-93.3
3 of 5	163	96.3	93.4-99.2
4 of 5	114	97.4	94.4-100.0
5 of 5	30	100.0	*90-100

^*The lower bound of the 95% confidence interval was calculated using the 1-(3/N) rule for instances in which the event rate is zero.¹⁷

The most prevalent criteria leading to rating an extubation as MIR was breath-holding or apnea for > 10 s, 12/15, (80.0%). Laryngospasm or CPAP for > 2 min were the next most prevalent with both being present in 11/15, (73.3%) of patients, with these last two overlapping in 7/11, (63.6%) of patients. Of the 29 patients requiring intervention but not requiring a major intervention 28/29 (96.6%) required CPAP longer than 30 s and < 2 min, 17/29, (58.6%) had an SpO2 < 92% for 30 s to 1 min and 7/29, (34.5%) had stridor not progressing to desaturation for > 1 min or requiring intervention beyond CPAP with 100% oxygen for < 2 min. No patients whose extubation was rated as intervention required (IR), had only stridor.

Secondary Results

There was no significant difference observed between those extubations requiring intervention (IR+MIR) and those that were considered successful (S) in terms of age, weight, ASA status, or gender. A univariate analysis found URI and midazolam premedication in children ≥ 1 year of age to be associated with extubations requiring intervention (IR+MIR): OR 2.57 ([95%CI: 1.29–5.13], p = 0.007), and OR 2.83 ([95%CI: 1.06–7.60, p = 0.031]), respectively. URI, as defined by the study, was noted in 15.2% (91/600) of patients. Additionally, an analysis of ETCO2 at extubation revealed an association with the IR+MIR group in patients extubated with an ETCO2 > 55 mmHg, OR 3.06 ([95%CI: 1.60–5.83, p = 0.001]). Asthma, use of nondepolarizing neuromuscular blocker, maintenance potent inhalational anesthetic choice, airway procedures, age <1 year of age, and emergency case status were not found to be significantly associated with extubations requiring intervention. A summary of these findings is presented in Table 6.

Table 6.

Demographics and univariate analysis of risk factors for the IR+MIR group.

Demographic Factors	S N=556	IR+MIR N=44			P-Value for t-test comparison of demographic factors for S versus IR+SIR
Mean Age (years) ±SD	2.5±2.0	2.7±2.1			0.514
Mean Weight (kg) ±SD	13.7±7.1	15.8±11.6			0.250
Factors Potentially Associated with extubation requiring intervention (IR+MIR)	S (n=) (Prevalence%)	IR+MIR (n=) (Prevalence%)	Odds Ratio for IR+MIR	95% CI for Odds Ratio for IR+MIR	P-Value for Chi-square or Fisher’s Exact Analysis of Association of Factor and IR+MIR
ASA Status
1	148 (26.7%)	10 (22.7%)	0.81	0.39-1.68	0.567
2	282 (50.8%)	25 (56.8%)	1.28	0.69-2.38	0.437
3 or 4*	125 (22.5%)	9 (20.5%)	0.89	0.42-1.89	0.754
Male	369 (66.4%)	31 (70.5%)	1.20	0.62-2.36	0.580
Age < 1 year	191 (34.4%)	15 (34.1%)	1.02	0.53-1.95	0.951
Emergency case status***	14 (2.5%)	1 (2.3%)	0.90	0.12-7.00	1.000
Airway procedure	130 (23.4%)	9 (20.4%)	0.83	0.39-1.78	0.639
URI	78 (14.0%)	13 (29.5%)	2.57	1.29-5.13	0.007
Asthma***	35 (6.3%)	4 (9.1%)	1.54	0.52-4.54	0.513
ETCO2 > 55 mmHg	89 (16.0%)	17 (38.6%)	3.06	1.60-5.83	0.001
Use of NMB	191 (34.4%)	19 (43.2%)	1.45	0.78-2.70	0.239
Midazolam**	232 (62.9%)	24 (82.8%)	2.83	1.06-7.60	0.031
Sevoflurane	310 (51.6%)	19 (43.2%)	0.71	0.38-1.32	0.283
Isoflurane	201 (36.2%)	20 (45.5%)	1.47	0.79-2.73	0.220
Desflurane	68 (12.2%)	5 (11.4%)	0.92	0.35-2.42	0.866

^*ASA Status 3 and 4 were collapsed because of a 0% prevalence with extubation requiring intervention ( IR+MIR) outcome for ASA Status = 4;

^**Total N=600 for all risk factors for extubation requiring intervention except for midazolam where N=398 because children < 1 year of age were excluded from this analysis;

^***Fisher Exact test used because IR+MIR cell count was <5. S=Successful; IR=Intervention Required; MIR=Major Intervention Required; NMB=Non-Depolarizing Neuromuscular Blocker.

Discussion

The primary finding of this study was that among the factors studied to assess fitness for awake extubation following an inhalational anesthetic in children < 7 years of age, the most important are facial grimace, eye opening, purposeful movement, tidal volume > 5 ml/kg, and conjugate gaze. Further, because no predictor appears to be far superior to another, a stepwise, multifactorial approach is likely to be more useful to the clinician than using one or two favorites, especially given the difference in prevalence of some of these factors at the time of extubation. To put this in more practical terms, at the time of emergence the clinician, for example, may note that conjugate gaze and tidal volume > 5 ml/kg are present. If the clinician chooses to extubate at this point our study would predict a success rate of 88.4%. If, however, the clinician waits for just one more predictor, such as facial grimace or purposeful movement their probability of success becomes 96.3%. It should be noted, that although the rate of IR+MIR events was zero in patients with 5 out 5 of these predictors present, the number of extubations observed in this group, N = 30, was relatively small and the 0% IR+MIR event rate must be evaluated with some caution in this context. Using the 3/N rule for instances in which an event rate is zero and N is the total number of events, the lower bound of the 95% CI is 90%.¹⁹

One unanticipated finding of this study was that spontaneous tidal volumes of > 5 ml/kg were associated with success in preference to other criteria we assumed would be more important, such as low end tidal inhalational anesthetic concentration. This may have been because end tidal inhalational anesthetic concentration is an imprecise measure of the concentration of inhalational anesthetic within the central nervous system.²⁰ Additionally, anesthetic concentration effects could be altred by a complex synergy with various sedatives (such as midazolam and opioids). The most obvious explanation for small tidal volume being a risk was the potential contribution of residual weakness impacting successful extubation. However, no patient requiring intervention was rescued with additional reversal, and neuromuscular blockade was not associated with patient requiring intervention. We theorize, that this finding may actually be related to the rapid and shallow pattern of breathing typically associated with light levels of inhalational anesthesia.²¹ Thus, inadequate tidal volume may actually be an indicator or surrogate indicator that the patient has not yet passed out of stage 2.

It was also of interest that conjugate gaze achieved significance. In the design phase of the study a majority of attendings felt that conjugate gaze was potentially suggestive of readiness for extubation but was at best a secondary predictor and not something they tended to use as a primary measure of readiness. In fact, in 65/600,(10.8%) of cases attendings chose not to check for it at all. It would appear, however, that conjugate gaze is a fairly specific indicator that a patient has passed through stage 2.

Eye opening, purposeful movement, and facial grimace were less surprising as these predictors are well known to most clinicians. The one critique of these 3 predictors though, would be that they appear to be fairly late signs of fitness for extubation as indicated by their lower prevalence in those extubated successfully when compared to some other predictors, and waiting for one or more of them may prolong emergence and extubation.

It is important to recognize the occurrence of these factors is dependent on time, and an assessment of which predictor is present can also guide the clinician in determining where the patient is in the emergence process. Although we did not specifically record which predictors occurred in which order, we can infer from the prevalence of these predictors in patients that were extubated successfully, that certain predictors such as tidal volume > 5 ml/kg and conjugate gaze are fairly early indicators reflected by their increased prevalence of 92% and 63% in patients extubated successfully. Further, we can infer that purposeful movement or eye opening are likely to be later signs, being present in only 37% and 17% of patients extubated successfully. In situations where one or more criteria are absent, as not all criteria occur in exactly the same order every time, an evaluation of which of these criteria is present, including those that did not achieve significance, may give additional guidance to the clinician in assessing the risk and timing of extubation. For example, a positive laryngeal stimulation test may be reassuring in a patient with tidal volumes > 5 ml/kg and conjugate gaze, with no other criteria present, but by itself, its high prevalence in patients extubated successfully would suggest that it occurs relatively early in the process of emergence and as such the patient may still be at increased risk of laryngospasm.

Now the conservative clinician might suggest that perhaps extubation should be delayed until all 5 of these predictors are present, as with time they will all eventually become present. While this will likely increase the rate of success slightly, it may be impractical and unnecessary, especially as the time to extubation following completion of surgery becomes unwieldy Additionally, there appears to be progressively smaller benefit in terms of predictive value when going from 3–4 or 4–5 predictors as compared to going from 2–3 predictors. In higher risk patients, though, this may represent an appropriate strategy.

Factors that were associated with a lack of success included: URI symptom within 7 days of the surgical procedure, midazolam premedication in children > 1 year of age, and post-hoc an ETCO2 > 55 mmHg. While we cannot say that there is a causal relationship between extubations requiring intervention and these factors, their association with the extubations requiring intervention would suggest that they may alter the predictive value of the 5 criteria identified in this study individually and/or collectively. As a result, the clinician may want to exercise additional caution at the time of extubation in these settings. Of these 3, an ETCO2 > 55 mmHg appeared to have the greatest association with extubations requiring intervention. Obviously, multiple factors, alone and in combination can lead to reduced alveolar ventilation and thus elevations of ETCO2. Thus, it is difficult to make specific recommendations to the practicing clinician, but this may represent an area for future study. At this time, we are aware of only one study by Baijal et al. in children undergoing adenotonsillectomy which specifically mentions the impact of an ETCO2 > 55 mmHg, at the time of extubation, stating that it was only associated with minor respiratory complications in the PACU.¹¹

The limitations of this study include its observational design and the fact that it was conducted at a single center. It is possible that practice patterns between attendings were more similar than first appreciated leading to bias and possible confounding with similar criteria being used by different attendings. Additionally, these results do not apply to “awake” removal of a supraglottic airway devices or “deep” extubation. The results and possible conclusions of this study also, only apply to cases in which an inhalational anesthetic is used for maintenance and not to cases where propofol or total intravenous anesthesia are used for maintenance. This is because potent inhalational anesthetics have different mechanisms of action and different interactions with reactive airway reflexes.²² Also, it may be that certain preexisting factors, such as age, URI, sleep apnea, as well as the variance in the anesthetic prescription for each patient in terms of types, dose, and timing of various opioids, dexmedetomidine, ketamine, and the use of midazolam may have significantly affected the value of any one individual criteria and controlling for this may have led to different findings. Finally, it is also possible that another criterion exists that was not included in the study that may actually be more important in terms of predicting extubation success than any one of the criteria we selected.

In conclusion, a multifactorial approach including conjugate gaze, purposeful movement, eye opening, tidal volume > 5 ml/kg, and facial grimace may lead to increased rates of successful extubation in young children undergoing anesthesia and surgery. Further, this information may allow the clinician to approach awake extubation in a more rational fashion than was available previously. More prospective study is necessary to further clarify the interactions of other comorbidities such as obesity, URI, and sleep disordered breathing on the predictive value of these different criteria.

What we already know about this topic:

• Emergence from anesthesia and extubation is a critical time in pediatric anesthesia when there is an increased risk of adverse events.

• Complications are more likely if extubation occurs prematurely during light anesthesia.

• Predictors of successful extubation have been identified in critically unwell children and in the intensive care environment but these predictors have related to presence of ongoing cardiopulmonary embarrassment rather than judgement of appropriate plane of anesthesia.

What this article tells us that is new:

• For an awake-extubation in a child that has had volatile anesthesia, facial grimace, purposeful movement, conjugate gaze, eye opening and tidal volume > 5ml/kg are all associated with successful extubation

• The chances of successful extubation steadily increase as more of these features are present.