Respiratory and hemodynamic outcomes following exchange extubation with laryngeal mask airway as compared to traditional awake extubation

Abstract

Background:

Traditional awake extubation leads to respiratory complications and hemodynamic response which are detrimental in neurosurgery, ENT surgery and patients with comorbidities.

Aims:

The primary objective was to compare the respiratory complications and hemodynamic stress response between traditional awake extubation of a endotracheal tube (ETT) and that following exchange extubation of ETT by using a laryngeal mask airway (LMA).

Settings and Design:

This prospective randomized study was conducted in a Tertiary Care Centre in 60 American Society of Anesthesiologists I and II patients coming for general surgery.

Materials and Methods:

Patients were randomized by permuted blocks into traditional awake extubation group and exchange extubation group. At the end of surgery in traditional group, awake extubation of ETT was done. In exchange group, 0.3 mg/kg propofol was administered, and the ETT was exchanged for a LMA. Awake extubation of LMA was then performed. Respiratory complications such as bucking, coughing, desaturation and the need for airway maneuvers and hemodynamic response were noted in both groups.

Analysis Tools:

Chi-square test, independent sample t- and paired t-tests were used as applicable.

Results:

Incidence of respiratory complication was 93.3% in traditional extubation while it was only 36.7% in exchange extubation group (P < 0.001). Hemodynamic response measured immediately at extubation in terms of heart rate, systolic blood pressure (BP), diastolic BP, mean arterial pressure, and rate pressure product were all significantly lesser in exchange group when compared to traditional extubation.

Conclusion:

Exchange extubation with LMA decreases respiratory complications and hemodynamic stress response when compared to traditional awake extubation.

INTRODUCTION

Awake extubation of endotracheal tube (ETT) is associated with complications such as bucking, coughing, bronchospasm, hypertension, tachycardia, myocardial ischemia, arrhythmias, and increased intracranial pressure.[1] Deep extubation of ETT leads to upper airway obstruction and hypoventilation. Replacing the ETT with a laryngeal mask airway (LMA) when the patient is deep and performing an awake extubation of the LMA was shown to decrease the above described respiratory and hemodynamic complications. This method of extubation has been described as an advanced technique which requires training and experience.[2] To deepen the plane of anesthesia while replacing the ETT with the LMA, higher concentrations of isoflurane, sevoflurane, and propofol infusion had been used.[3,4,5]

The aim of our study was three-fold. The primary objective was to compare the respiratory complications and hemodynamic stress response between traditional awake extubation of an ETT and that following exchange extubation of ETT by using an LMA and 0.3 mg/kg propofol bolus. The secondary objectives were to determine whether this method was easy to perform, the amount of experience needed to perform the exchange well and to calculate the time delay in extubation caused by adopting this method.

MATERIALS AND METHODS

This prospective randomized study was conducted at a medical university on patients coming for general surgery from August 2013 to May 2015. After Ethical Committee clearance and informed consent, 60 patients were randomized by permuted blocks into two groups – Group T (awake endotracheal extubation group) and Group L (exchange extubation with LMA). American Society of Anesthesiologists (ASA) grades I and II patients, between the age of 18 and 65 years undergoing elective non-oral surgery were included in the study. Patients with upper or lower respiratory infection, bronchial asthma, cardiac diseases, ASA III and above, obesity, gastro-oesophageal reflux disease, and anticipated difficult extubation were excluded from the study.

All patients were orally premedicated with ranitidine 150 mg and metoclopramide 10 mg on the night prior to surgery and morning of surgery. Alprazolam 0.25 mg was given on night prior to surgery. On the day of the surgery, the patient was brought to the operation theatre, and an intravenous (IV) cannula was inserted. The following monitors were then connected: pulse oximeter, electrocardiogram, and noninvasive blood pressure (BP). Patients were preoxygenated for 3 min with 100% oxygen using a face mask. Patients were then given IV midazolam 0.01 mg/kg to a maximum of 2 mg, glycopyrrolate 0.01 mg/kg to a maximum of 0.2 mg, fentanyl 2 μg/kg, and propofol 1–2 mg/kg. Three minutes after vecuronium 0.1 mg/kg was given IV patients were intubated with 7.5 or 8.5 size ETT in males and females, respectively. Anesthesia was maintained with 0.6–1% isoflurane in nitrous oxide-oxygen mixture (2:1) with mechanical ventilation. Fentanyl 0.5 μg/kg was repeated every hourly or as and when required and vecuronium 0.02 mg/kg was repeated every 45 min. Tidal volume was set at 7 ml/kg of ideal weight, and the respiratory rate was adjusted to keep end-tidal carbon dioxide between 32 and 40 mmHg. Intraoperatively paracetemol 1 g was given in both groups IV if there were no contraindications.

In the endotracheal awake extubation group (Group T), at the end of the surgical procedure, isoflurane and nitrous oxide were discontinued. Neostigmine 0.05–0.07 mg/kg and glycopyrrolate 0.01 mg/kg IV were used for reversing the effects of vecuronium. If the patients were spontaneously generating tidal volume of >4 ml/kg, EtCO₂<45 mmHg and was responding to verbal commands, extubation was performed. Supplementary oxygen was then provided with Hudson mask at the rate of 6 L/min.

In the LMA group (Group L), at the end of the surgical procedure, nitrous oxide was discontinued, and a bolus of 0.3 mg/kg propofol was administered. After 1 min, the oropharynx was suctioned, and a deflated LMA was inserted over the ETT [Figure 1]. The ETT was then removed. LMA was inflated and connected to breathing circuit. If we could not ventilate through the LMA, it was repositioned. If it was still unsuccessful, LMA insertion was abandoned, and mask ventilation was resumed. Following successful insertion of LMA, isoflurane was discontinued, 100% oxygen was administered at 6 L/min, neuromuscular blockade was reversed with neostigmine and glycopyrrolate and the patient was monitored. When the patient was able to spontaneously maintain tidal volume of >4 ml/kg, end tidal carbon dioxide <45 mmHg and was responding to verbal commands, extubation was performed.

Figure 1.

Laryngeal mask airway inserted over endotracheal tube

In Group L, all the exchanges were performed by a single anesthetist, in order to determine if a learning curve was present. Patients were observed from the end of surgery (EOS) up to 1 h in the postanesthesia care unit. The occurrence of straining, bucking, coughing, LMA repositioning, desaturation to <95%, chin lift, jaw thrust and need for bag and mask ventilation was noted. The occurrence of any one of the above incidents was considered as an instance of respiratory complication.

The heart rate (HR), systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and rate pressure product (RPP) were recorded at the following times baseline – before induction, EOS, just after exchange (Ex), just after extubation (E0), 5 min after extubation (E5), 10 min after extubation (E10), and 15 min after extubation (E15). The time between placing and extubating the LMA was also recorded.

Study size

Based on previous studies, the incidence of respiratory complications when ETT was removed either deep or awake was about 60–80% and for LMA removal it was 20%. With an enrolment ratio of 1, allowing for an alpha error of 0.05 and power of 80%, the sample size was calculated to be 22 patients in each group, which was rounded off to 30.

Analysis tools

Chi-square test was used to find the association of straining, bucking, coughing, desaturation to <95%, chin lift, jaw thrust and need for bag and mask ventilation, among T Group and L Group. Independent sample t-test was used to compare the mean HR, SBP, DBP, MAP, and RPP between T Group and L Group. The mean changes of these variables at EOS and after placement of LMA in LMA group was compared using paired t-test.

RESULTS

While comparing the distribution of sex, age, height, weight, and ASA grade between the two groups there was no statistically significant difference. On comparing respiratory complications between the two groups, 93.3% patients in Group T had at least one respiratory complication, while it was only 36.7% patients in Group L. The difference was statistically significant (P < 0.001). The incidence of coughing and bucking was also lower in L Group and it was statistically significant (P < 0.001) [Table 1 and Figure 2].

Table 1.

Comparison of respiratory complications

Figure 2.

Incidence of respiratory complications

LMA had to be repositioned in 9 out of 30 patients in the LMA group (30%). Chronologically dividing the patients in Group L into two, among the first 15 patients, LMA has to be repositioned 8 times (53.3%). In the next 15 patients, the LMA had to be repositioned only once (6.6%).

On comparing the baseline and EOS HR, SBP, DBP, and MAP there was no statistically significant variation between the two groups.

Immediately, after extubation Group T had a significantly higher mean HR, SBP, DBP, and MAP as compared to Group L [Tables 2 and 3, Figures 3 and 4]. At 5 min after extubation, all these parameters remained high in Group T except DBP, which showed no significant difference with Group L. However, at 10 min after extubation both the groups were comparable with regard to HR, SBP, DBP, and MAP. At 15 min also all these hemodynamic parameters remained comparable except SBP, which was significantly high in Group T.

Table 2.

Comparison of heart rates after extubation

Table 3.

Change in mean arterial pressure

Figure 3.

Comparison of systolic blood pressure and diastolic blood pressure

Figure 4.

Comparison of heart rate and mean arterial pressure

On comparing the RPP in Groups T and L, RPP was found to be significantly higher in Group T than in Group L immediately, 5, 10, and 15 min after extubation [Table 4]. Immediately after insertion of LMA and removal of ETT, there was a significant increase in HR, SBP, DBP, MAP, and RPP from the values at EOS in Group L [Table 5]. On an average, it took 12.07 ± 3.6 min from exchange of LMA to extubation of LMA in Group L.

Table 4.

Changes in rate pressure product

Table 5.

Changes after insertion of laryngeal mask airway and removal of endotracheal tube

DISCUSSION

The respiratory complications and hemodynamic responses associated with extubation is often overlooked during the conduct of general anesthesia (GA).[6,7,8] As anesthetists, we should extubate our patients ensuring both safety and comfort. Smooth extubation becomes more important when the patient has cardiovascular disease or has undergone neurosurgery, ENT surgery or eye surgery. Anesthetists when pressed upon for a smooth extubation, tend to go for a deep extubation of the ETT, which has the theoretical risk of losing the airway, before the patient is fully conscious and requires airway manipulations, albeit external. Nair and Bailey, Costa e Silva and Brimacombe and Glaisyer et al.[9,10,11] had suggested that the use of the laryngeal mask after tracheal extubation may minimize the stress response while providing a patent airway during emergence from anesthesia. They inserted the laryngeal mask after extubation; however, there is a small theoretical risk of losing a patent airway, if it is not possible to insert the laryngeal mask after the tracheal tube has been removed. The LMA being situated in the hypopharynx eliminates tracheal stimulation at extubation, makes extubation smooth and comfortable for the patient. Asai et al. and Dob et al.[12,13] improvised on this method by inserting the LMA behind the ETT and then removing the ETT, thereby avoiding the loss of airway.

Exchange extubation has been mentioned in the Difficult Airway Society guidelines for the management of tracheal extubation, where the authors have recommended it as an advanced technique requiring training and experience for extubation for “at risk” extubation.[2] An extubation is said to be “at risk” by the authors if the ability to oxygenate is uncertain, the reintubation is potentially difficult, and the patient has cardiovascular, respiratory and neurological comorbidities.

The first question that comes to the mind of any anesthetist, on hearing about exchange extubation is whether it is feasible. Stix et al.[14] had shown that he could successfully place a LMA in the first attempt in 95% of cases. We were able to place the LMA successfully on the first attempt in only 70% of cases (21/30). Stix et al. have got better results because of the following reasons:First, they went through a “learning” phase where they just inserted and removed the LMA in the presence of the ETT just after induction. After the end of the learning phase, they did the actual study. Our study did not have a learning phase, and we attempted it without previous experience. If we consider our 30 patients in the L Group by chronological order, in the first 15 patients we had a higher LMA repositioning rate (8/15), than in the next 15 (1/15). This gives an LMA first attempt successful insertion rate of 93.3% in the second set of 15 patients which is comparable to Stix's results. A learning phase would help decrease the LMA repositioning rate. Second, they performed the exchange 30 min before EOS, where the patient would have been deep and probably under the cover of muscle relaxants. In our study, we had done the exchange after the EOS, where the patient was in a lighter plane, without the maintenance dose of muscle relaxant as the anesthetist was preparing for an extubation. Therefore, it would have been more difficult to insert the LMA.

In Brouillette et al.'s study,[3] the incidence of cough was 94.87% for the ETT group and 17.94% for the LMA group. Their observations were in agreement with our study in which the incidence of a cough was 83.3% for the ETT group and 20% for the LMA group. Keeping the patient in a deeper plane of anesthesia for the exchange of ETT with LMA can be achieved by various techniques. Jain et al.[5] had studied the exchange of ETT with both classic LMA (cLMA) and Ambu laryngeal mask while using a propofol infusion. The incidence of coughing and LMA repositioning in our study was almost similar for exchange extubation with a cLMA in Jain et al.'s study. They had used a propofol infusion to maintain anesthesia and continued the infusion during the exchange and until the patient became spontaneous. Sixty-six percentage nitrous in oxygen along with 10 mg/kg/h propofol infusion was used initially, followed by 5 mg/kg/h, even during the exchange and continued propofol until they could confirm smooth spontaneous respiration through the LMA. It is worthwhile to note that the Ambu laryngeal mask along with a propofol infusion easily outperforms the cLMA.

The mean percentage increase in HR (13%) and MAP (10%) in Jain et al.'s study after exchange extubation are lesser than in our study (19% increase in HR and 11.3% increase in MAP). 5 mg/kg propofol infusion run by Jain et al. throughout the surgery, during the exchange and until confirmation of spontaneous respiration is superior to our single bolus of 0.3 mg/kg of propofol given just before extubation. The difference between the two groups in terms of percentage change in HR and BP could be explained based on the sedative and hypotensive effect of a prolonged propofol infusion. The propofol effect would persist for a longer time because of context sensitive half time. In our study, after the exchange was performed, isoflurane was discontinued, while in Jain's study propofol was continued till the start of spontaneous respiration. Longer duration of administration of the primary anesthetic agent (propofol vs. isoflurane) must have produced the difference.

Another method to keep the patient in deeper plane could be using inhalational agents. When adopting this method, it will be prudent to choose an agent with rapid emergence. Differences in solubility of volatile anesthetic agents in blood has got important implications in awakening following GA. Takita et al.[4] investigated the effective dose 95% in terms of minimum alveolar concentration of end-tidal sevoflurane concentration for the smooth exchange of an ETT for an LMA without coughing, movement or airway obstruction and found it to be 2.97%. Reduction in time spent in operation theater ultimately results in a quicker patient turnover. However, any time delay with exchange extubation can easily be overcome by shifting the patients to postoperative Intensive Care Unit and performing the extubation there.

The present study had demonstrated that hemodynamic response in terms of HR, BP and RPP were significantly lesser in exchange extubation group when compared to awake endotracheal extubation. Similar results were demonstrated by Ma et al.[15] and Ping et al.[16] In Group L there was an increase in the hemodynamic parameters at the time of ETT removal and LMA insertion, from the values at the EOS [Table 5]. But even these values were significantly lower than the values documented at the time of awake extubation in Group T [Figure 5]. So exchange extubation with LMA can be considered as a safe option for those patients in whom hemodynamic stress response of extubation is to be blunted.

Figure 5.

Comparison of hemodynamic variables on removal of endotracheal tube in both groups

There have been studies on postoperative sore throat after the exchange extubation. In the study by Brouillette et al.,[3] 8 out of 39 patients in the ETT group had a sore throat in the recovery room and 11 the day after, compared to 3 and 5 in the LMA group. More patients in ETT group complained of hoarseness (29 in the recovery room, 21 the day after) than in the LMA group (7 and 4, respectively). The difference was statistically significant. In the study by Jain et al.[5] the incidence of a sore throat in both the cLMA exchange group and the Ambu laryngeal mask exchange group recorded 1 h after surgery was 16%.

Our study had shortcomings. There is an obvious bias in the study, as a single anesthetist did all the 30 exchanges. Even though this is a significant limitation, it has a silver lining. It was able to bring out the fact that, a phase of learning is required to have a higher success rate in the first attempt LMA positioning.

As the administration of muscle relaxants and depth of anesthesia was left to individual anesthetists doing the case, we could not ensure a uniform depth of anesthesia to all our patients. The anesthetists were free to maintain isoflurane between 0.6% and 1% and had given muscle relaxants and fentanyl as and when required. A bispectral index and train-of-four monitor would have been useful in ensuring an equal level of depth of anesthesia for all our patients. We did not study the incidence of a postoperative sore throat after the exchange.

CONCLUSION

Exchange extubation of ETT with LMA decreases respiratory complications and hemodynamic stress response when compared to traditional awake extubation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest