A prospective randomized control study comparing classic laryngeal mask airway with Guedel's airway for tracheal tube exchange and smooth extubation.

INTRODUCTION: Extubation in deep plane of anesthesia followed by Guedel's oropharyngeal airway (OPA™) insertion is a routine method to avoid hemodynamic changes associated with tracheal extubation. Exchange of endotracheal tube (ETT) with Classic laryngeal mask airway (LMA™) prior to emergence from anesthesia also serves similar purpose. We had compared the hemodynamic changes involved during this ETT/LMA™ and ETT/OPA™ exchange technique.
MATERIAL AND METHODS: This was a randomized prospective study on ASA I and 2 patients undergoing elective surgery under general anesthesia. These patients were randomly divided into two groups i.e. OPA group and LMA group of 50 patients each. Hemodynamic parameters i.e. systolic blood pressure (SBP) and heart rate (HR) were recorded during exchange of ETT with OPA™ or LMA™. Coughing / bucking during removal of OPA™ and LMA™, and presence of post operative sore throat for both the groups were also graded and recorded. Data within the groups have been analyzed using paired "t" test while those between the groups were analyzed using unpaired "t" test. Chi square test was used to analyze grades of coughing and post operative sore throat.
RESULTS: In both groups, hemodynamic parameters rose significantly as OPA™/LMA™ was placed (P < 0.05) and then started declining. Hemodynamic parameters continued to fall in LMA group after extubation. However in OPA group, hemodynamic parameters continued to rise even after extubation and declined only when OPA™ was removed. There was no statistical significant difference between the LMA and OPA group in respect to coughing and post operative sore throat.
CONCLUSION: LMA™ is superior to OPA™ for exchange of ETT as it provides greater hemodynamic stability.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Significant hemodynamic changes secondary to coughing or bucking on endotracheal tube (ETT) at the end of anesthesia can lead to increased intraocular and intracranial pressure and hypoxia.[1] This can be detrimental in neurosurgical, ophthalmic, otorhinolaryngological cases, and patients with coronary artery diseases.[2]

Pharmacological agents such as opioids and inhalational agents can be used to prevent significant hemodynamic changes, but it leads to prolonged sedation.[34] Lidocaine, β-blocker, calcium channel blocker, and dexmedetomidine are also effective in controlling the hemodynamic response during extubation.[567]

Other strategies to prevent significant hemodynamic changes and avoid coughing over the tube include extubation in deep plane of anesthesia followed by Guedel's oropharyngeal airway (OPA™) insertion to avoid airway obstruction by the tongue.[891011] Exchange of ETT with classic laryngeal mask airway (CLMA™) before emergence from anesthesia is also a technique which besides preventing hemodynamic changes, provides a secure airway following tracheal extubation as well as smooth recovery period.[12121314]

In this study, we had compared the hemodynamic changes involved during the exchange of ETT with either OPA™ or LMA™ to determine which one provides better hemodynamic stability. In addition, coughing/bucking during placement and removal of LMA™/OPA™ and the presence of postoperative sore throat for both the groups were graded and recorded.

MATERIALS AND METHODS

After approval from the Hospital Ethical Committee, patients undergoing elective laparoscopic cholecystectomy were included in the study. The American Society of Anesthesiologists (ASA) I and II patients between age range of 20–50 years and weighing 40–60 kg, who gave informed consent, were included in the study. Patients with predicted difficult airway and those who refused to participate were excluded from the study. Patients were randomly divided into two groups of 50 patients each on the basis of extubation methodology, using random computerized table. The two groups were OPA group, in which OPA™ was placed before extubation and LMA group, in which LMA™ was placed before extubation.

All the patients were premedicated with midazolam 0.025 mg/kg intravenous (i.v.), fentanyl 2 µg/kg i.v., and ondansetron 0.1 mg/kg i.v. 15 min before induction of anesthesia. Anesthesia was induced with propofol 2 mg/kg i.v., and neuromuscular blockade was achieved with vecuronium bromide 0.1 mg/kg i.v. After achieving adequate relaxation, trachea was intubated, and anesthesia was maintained with a step down technique of propofol infusion (10 mg/kg/h for initial 15 min, 8 mg/kg/h for the next 15 min, and thereafter 5 mg/kg/h i.v. via syringe pump, until the conclusion of surgery). In addition, all patients received 66% of N2O in O2 and muscle relaxant top-up doses as per peripheral nerve stimulator. After the conclusion of surgery, N2O was discontinued, but propofol was continued to run at the rate of 5 mg/kg/h. In OPA group, Guedel's OPA™ (size 3) was placed while in LMA group, LMA™ (size 3) was placed, but the cuff remained un-inflated. Residual neuromuscular block was now reversed using a mixture of neostigmine (2.5 mg) and glycopyrrolate (0.4 mg). Adequate reversal of neuromuscular block was confirmed by a train of four ratios >0.9 and return of adequate tidal volume. ETT was now removed keeping OPA™/LMA™ in place. In OPA group, facemask breathing was now commenced with OPA™ in place. In contrast, in patients of LMA group, the cuff of LMA™ was now inflated with 20 mL air and the breathing system connected to laryngeal mask. An adequate and smooth, spontaneous respiration was reconfirmed clinically and by capnography. If inadequate, OPA™/LMA™ was removed and reinserted. Propofol was now discontinued, and the patient continued to breathe 100% of O2. After full awakening, OPA™/LMA™ was removed. During this period of exchange of ETT with OPA™/LMA™, patient's hemodynamic parameters, i.e., heart rate (HR) and systolic blood pressure (SBP) were recorded just before OPA™/LMA™ placement, post-OPA™/LMA™ placement, preextubation, postextubation, and thereafter at 3 and 5 min, immediately after OPA™/LMA™ removal, and after 3 and 5 min. Any episode of coughing/bucking during OPA™/LMA™ placement, ETT and OPA™/LMA™ removal were recorded. Coughing/bucking was graded as - Grade I, if there was no coughing/bucking, Grade II, if there was mild coughing/bucking (<5 cough) and Grade III, if there was severe bout of coughing/bucking/laryngospasm (>5 cough).

Postoperative sore throat was recorded in the immediate postoperative period by an independent observer after 1 h. The absence of sore throat was recorded as Grade I. Sore throat which was less severe than common cold was Grade II, that was similar to common cold was Grade III, and one which was more severe than common cold was Grade IV.

Statistical analysis

The primary outcome measured was change in hemodynamic parameters while secondary outcome included coughing/bucking and postoperative sore throat for both the groups.

We conducted a pilot study with seven patients in each group and presuming the difference in the SBP and effect size obtained to be true, with α error of 0.05 and β error of 0.8, calculated that 41 patients in each group would be required for the study. Fifty patients were taken in each group to compensate for dropouts.

All data in the tables have been presented as mean ± standard deviation. Data within the groups have been analyzed using paired t-test while those between the groups were analyzed using unpaired t-test. The value of P < 0.05 was considered as significant in this study. Chi-square test has been used to identify the difference between two proportions. It was used to analyze the grades of coughing during removal OPA™/LMA™ and postoperative sore throat. The value of Z > 1.96 was considered statistically significant. SPSS 14 program (SPSS Inc., Chicago, USA) was used for statistical analysis.

RESULTS

All the patients in both the study groups were female. The average age of patients in OPA group was 35.6 years (range 25–45.6 years), and LMA group was 36.9 years (range 25.4–44.8 years).

In both the groups, hemodynamic parameters rose significantly as OPA™/LMA™ was placed (P < 0.05) and then started declining. Again, there was an insignificant rise in both the parameters on extubation. Thereafter, in OPA group, hemodynamic parameters continued to rise after extubation and declined only when OPA was removed. However, in LMA group, hemodynamic parameters started declining after extubation and continued to fall thereafter [Tables 1 and 2].

Table 1

Changes in systolic blood pressure during periextubation period

Table 2

Changes in heart rate during periextubation period

None of the patients of both the study groups had coughing or bucking during the placement of OPA™/LMA™ as well as during the removal of ETT. The incidence of smooth removal of OPA™ or LMA™, i.e., with no coughing and bucking (Grade I) was 72% in LMA group as compared to 56% in OPA group, which is statistically insignificant (Z < 1.96) [Table 3].

Table 3

Grades of coughing during removal of OPA™/LMA™

In none of the cases in both the groups’ blood was seen on the surface of OPA™ or LMA™.

After ETT removal, adequate and smooth spontaneous respiration was achieved in all the patients. After extubation, it was never necessary to reinsert the LMA™ or OPA™ or shift to alternative airway in any of the cases.

The majority of patients (>50%) in both the groups showed no postoperative sore throat (Grade 0). The incidence of Grade I sore throat was 44% in OPA group and 32% in LMA group which was statistically insignificant (Z < 1.96) [Table 4]. None of the patients had Grade II or Grade III sore throat.

Table 4

Incidence of postoperative sore throat

DISCUSSION

Extubation is associated with significant hemodynamic changes which may not be well-tolerated by patients of neurosurgical, ophthalmic, otorhinolaryngological, and coronary artery disease.[2]

Extubation may be planned under deep anesthesia to avoid hemodynamic stress and coughing/bucking. This may result in airway obstruction and need for airway support maneuvers such as the use of face mask ventilation or OPA™.[89101112] Another safe technique for smooth extubation is to replace the ETT with LMA™ before emergence from anesthesia.[12121314] Soft tissue airway obstruction is thus avoided, and the patient is then permitted a smooth emergence from anesthesia with LMA.[2]

There was a significant rise in hemodynamic parameters immediately after the placement of OPA™, in OPA group patients. This could be secondary to rigid nature of the device with a relatively blunt end. Hemodynamic parameters continued to rise in these patients even after extubation. This could be attributed to the plastic material and rigid structure of Guedel's OPA™ that gives continuous irritation to the supraglottic structures in an awakening patient. Moreover, the occasional push is needed to maintain the position of the device in place. Fall of hemodynamic parameters started only after the removal of OPA™.

As the LMA™ was inserted in LMA group patients, a significant rise of hemodynamic parameters was seen. This might be attributed to the standard technique of insertion of LMA™ that requires finger support. After extubation, hemodynamic parameters started declining. Minimal changes in SBP and HR following the removal of LMA™, in this study, are in accordance to the previous findings that removal of an LMA™ is associated with significantly reduced hemodynamic responses.[15]

None of the patients of both study groups had coughing or bucking during the placement of LMA™/OPA™ and this might be due to the use of propofol with its known ability to suppress the cough reflex during upper airway manipulation. In contrast, Takita et al.[12] recorded 33.3% of incidence of coughing/bucking during placement of CLMA™, using variable concentration of sevoflurane for maintenance of anesthesia. We did not observe higher incidence of coughing/bucking as fixed dose of propofol was used in present study.

The incidence of smooth removal of CLMA™ was better than OPA™, the difference being insignificant. The findings of this study are in agreement with other studies which reported occasional coughing during removal of laryngeal mask.[114]

The majority of patients (50%) in both the groups had no postoperative sore throat. This might be attributed to the fact that extubation of ETT was done over LMA™ or on OPA™ and thus avoided straining on tube.[16] Postoperative sore throat is also dependent on the duration of insertion[17] and cuff pressure of ETT.[18] In our study, we did not measure the duration of insertion and cuff pressure.

There has been no reported study comparing OPA™ and LMA™ for hemodynamic changes during exchange with ETT. We have shown that between OPA™ and LMA™, latter provides significantly better hemodynamic control.

There is a natural hesitancy to perform ETT/LMA™ exchange as the procedure involves jeopardizing a secure airway. Further, malpositioning of LMA™ may be considered as a risk involved in such exchange. Malpositioning occurs due to the insufficient insertion depth of LMA or epiglottis blocking the glottis even when LMA is fully inserted.[19]

However, studies have reported adequate spontaneous respiration on LMA even in the presence of any malpositioning.[19] Therefore, any concerns due to above are misplaced.

Pharmacological agents though are effective in controlling hemodynamic changes are costly with variable success rate. Shorter acting opioids such as remifentanil, alfentanil, inhalational agents such as desflurane, isoflurane sevoflurane, though prevent hemodynamic changes, are associated with prolonged sedation.[34] Vasodilators such as sodium nitroprusside, nitroglycerine, and hydralazine, are associated with reflexive tachycardia and increase in the plasma renin activity.[20] β-blocker labetalol is low-potency drug[21] while esmolol is associated with bradycardia, hypotension, and conduction defects.[22] Calcium channel blockers have been associated with dose-dependent cerebral vasodilation, inhibition of autoregulation, and hypotension.[23] Dexmedetomidine in infusion can cause bradycardia and prolonged sedation.[24] Moreover, their exact dosage and administration times are still debated.

There are certain limitations of this study. ETT/LMA exchange should always be attempted under adequate anesthesia. Otherwise, this method offers no advantage.[12] Although we could not measure the depth of anesthesia due to nonavailability of bispectral index monitoring in our institute, but we had used propofol infusion to maintain adequate depth of anesthesia. Moreover, we conducted the study on ASA I/II patients who can tolerate the hemodynamic variations associated with extubation. However, this study would be more useful in ASA III/IV, cardiac, or neurosurgical patients. Both LMA™ as well as OPA™ are reusable after autoclaving and carry the risk of infection with prion disease.

CONCLUSION

Placement of LMA™ before tracheal extubation is associated with reduced hemodynamic changes compared to OPA™ and therefore, LMA™ should be considered superior to OPA™ as an exchange device for ETT.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.