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ORIGINAL ARTICLE
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Year : 2005  |  Volume : 51  |  Issue : 4  |  Page : 260-264  

Opioid sparing during endotracheal intubation using mccoy laryngoscope in neurosurgical patients: The comparison of haemodynamic changes with macintosh blade in a randomized trial

Prabhat Tewari1, D Gupta1, A Kumar1, U Singh2,  
1 Department of Anaesthesiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Raibarely Road, Lucknow, India
2 Department of Biostatistics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Raibarely Road, Lucknow, India

Correspondence Address:
Prabhat Tewari
Department of Anaesthesiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Raibarely Road, Lucknow
India

Abstract

Background: There is conflicting data in literature to show that the McCoy laryngoscope is less stressful and opioids can actually be avoided during laryngoscopy and intubation with the use of this laryngoscope. Aim: A comparison of hemodynamic changes with McCoy vs Macintosh laryngoscope.. Settings and Design: 180 ASA I and II neurosurgical patients undergoing elective surgery for space occupying lesions were recruited. The study was was prospective, randomized and blinded in the setting of neurosurgical perioperative services. Methods and Materials: The patients were divided into four groups (Gr.1 McCoy and fentanyl; Gr. 2 McCoy and no fentanyl; Gr. 3 Macintosh and fentanyl; Gr. 4 Macintosh and no fentanyl). In Gr. 2 and 4 equivalent volume of saline was given in place of fentanyl as placebo. Heart rate, systolic and diastolic blood pressure were measured after laryngoscopy, after intubation and subsequently every minute for the next five minutes. The incidence of cough due to fentanyl treatment was observed. Statistical Analysis: Haemodynamic changes were compared between and within groups using oneway ANOVA and repeated measures ANOVA. All analysis included 95% CI at 5% significance. The Mann Whitney U test was used for comparing incidence of cough. Results: No difference was found between McCoy laryngoscopy when done with or without fentanyl pretreatment (HR p =0.848, sys BP p =0.229 and diastolic blood pressure p =0.981). Significant changes in haemodynamic parameters were seen between Macintosh and McCoy laryngoscopy without fentanyl pretreatment ( p <0.001) whereas changes were blunted with fentanyl pretreatment in Macintosh laryngoscopy ( p <0.05). Conclusions: McCoy laryngoscope blade is less stressful and fentanyl pretreatment is not necessary to attenuate haemodynamic responses with its use in ASA I and II patients.



How to cite this article:
Tewari P, Gupta D, Kumar A, Singh U. Opioid sparing during endotracheal intubation using mccoy laryngoscope in neurosurgical patients: The comparison of haemodynamic changes with macintosh blade in a randomized trial.J Postgrad Med 2005;51:260-264


How to cite this URL:
Tewari P, Gupta D, Kumar A, Singh U. Opioid sparing during endotracheal intubation using mccoy laryngoscope in neurosurgical patients: The comparison of haemodynamic changes with macintosh blade in a randomized trial. J Postgrad Med [serial online] 2005 [cited 2022 Aug 7 ];51:260-264
Available from: https://www.jpgmonline.com/text.asp?2005/51/4/260/19231


Full Text

The haemodynamic responses to laryngoscopy and tracheal intubation are well described. Apart from other drugs, opioids seem to be good agents to suppress the enhanced haemodynamic responses to laryngoscopy and intubation.[1] Fentanyl has high potency but a short half-life and thus is a reasonably good agent to suppress these haemodynamic perturbations in patients undergoing surgical procedures.[2],[3] However, fentanyl also has adverse effects, which include inconsistency in obtunding the laryngoscopy and intubation response, hypotension and coughing.[4],[5],[6] In neurosurgical patients, coughing may further increase intracranial pressure, apart from the haemodynamic response of laryngoscopy and intubation, which can compromise the total blood flow to the brain and jeopardize its functions.[7]

Since its introduction in 1993, the McCoy levering laryngoscope has been reported to enable several otherwise difficult intubations.[8] The McCoy laryngoscope incorporates a modification of the Macintosh blade for better viewing of larynx. Use of this blade had been shown to be less stressful as haemodynamic variations are less though the number of patients in this trial were less.[9] We hypothesized that if McCoy laryngoscope is used for endotracheal intubation, then there would be fewer haemodynamic changes and consequently less fentanyl use. This formed the rationale of the study.

 Materials and Methods



After institutional ethical approval and written informed consent out of 200 screened participants 180 elective ASA 1 and 2 prospective patients, in the age range 18-50 years, with intracranial space occupying lesions, reporting to the neurosurgical department were included in this study. The study was carried out from January 2002 to 2003. The trial profile is given in [Figure 1]. Exclusion criteria were patients with airway problems, hypertension, diabetes, any other metabolic disease, cardiovascular disease, preoperative signs of intracranial hypertension or those known to have cerebral aneurysms. A sample size of 40 in each group has a 95% power to detect a difference of 8.14 mmHg blood pressure between means with McCoy and Macintosh laryngoscope with a significance level (alpha) of 0.05 (two tailed) according to a previous trial.[10] The patients were randomly assigned to one of the following four groups according to the computer-generated table of random numbers. The randomization was done by independent statisticians and by people not directly involved with the clinical study in the peri-operative period in the neurosurgical wards.

Group 1: McCoy laryngoscope with fentanyl pretreatment (McC+F).

Group 2: McCoy laryngoscope without fentanyl pretreatment (McC+NF).

Group 3: Macintosh laryngoscope without fentanyl (Mk+NF).

Group 4: Macintosh laryngoscope with fentanyl pretreatment (Mk+F).

Once the patient was wheeled in the operation theatre, two peripheral venous lines, a left radial arterial line and a triple lumen central venous pressure (CVP) line in right internal jugular vein were placed under local anaesthesia. The other intraoperative monitoring included real time ECG, pulse oximetry, capnography, core temperature, urine output and train-of-four ratio for muscle relaxant activity on Myotest (Biometer, Denmark). One of the anesthesiologists, who was blinded to the type of laryngoscope used gave all the drugs. This anesthesiologist was given an unmarked similar volume syringe, which either contained fentanyl or saline. Fentanyl pretreatment was done with 2 mg/kg, intravenously, in designated groups (Group 1 and Group 4) and same volume of saline was given in the no fentanyl group (Group 2 and Group 3). The drug was given 5 min prior to the start of induction. Another anaesthesiologist took note of the heart rate and blood pressure at different point of times (assessor blind). He was blinded for the drug and the device and he marked all the events on the trend graph of the monitor. The third anesthesiologist who was blinded to the drugs and the haemodynamic parameters did the laryngoscopy and intubation. Laryngoscopy technique was standardized with the head lifted on a pillow in all the cases. All the three anaesthesiologists were same for all the cases and followed the same protocol. Induction was done with intravenous midazolam (0.05 mg/kg), priming dose of vecuronium bromide (0.015 mg/kg) followed with thiopentone sodium. At the loss of eyelash reflex rest of vecuronium bromide (total dose 0.1 mg/kg) was given to achieve muscle relaxation. The remaining dose of thiopentone sodium was given to the total dose (5 mg/Kg) according to the protocol. At this point nitrous oxide was added so as to make 60% inhaled mixture in oxygen. The laryngoscopy was done immediately after two minutes once 90% block on Train-of-Four nerve stimulation was achieved. The McCoy laryngoscope was used with full lever on and it was never used as Macintosh laryngoscope. Once the vocal cords were visualized, the intubation was done. The laryngoscopy and intubation was done in single attempt and when ever more than one attempt was used or laryngeal pressure from outside was used, such patients were excluded.. The heart rate (HR), systolic blood pressure (SBP), and the diastolic blood pressure (DBP) were noted at different time points- baseline, after visualization of vocal cords, immediately after intubation, and subsequently at one-minute interval after intubation. These events were marked on the trend graphics on the monitor and the values were noted down afterwards. Thus haemodynamic data was collected for all the patients at eight time points. Provision for rescue by beta blockade using intravenous esmolol 150 mg stat (11) to check unusual haemodynamic responses after laryngoscopy to critical levels (rise of HR > 30%; SBP > 60% of basal value) was kept in the protocol. Once the data was collected the study protocol ended and all the patients were managed as per neurological OT anesthesia services protocol with fentanyl as analgesic. The haemodynamic data, the drugs used, the device used, patient profile and the incidence of cough was sealed in different envelopes by a person not associated with the study and all was sent to the statistician. They were opened for analysis once the trial was over.

For statistical analysis SPSS version 9 (SPSS corporation, USA) was used. The demographic data was compared by one-way anova. The number of females was presented as percentage and the ratio compared with Chi square test. Data for heart rate, systolic and diastolic blood pressure was presented as mean and standard deviation. Within group comparisons were done using repeated measures anova. Differences among the groups were analyzed using a one-way anova. A Tukey's test post hoc test was used when a significant difference seen with anova. Incidence of cough in patients was analysed using non parametric Mann-Whitney test. All analysis were done at 5% significance (degree of freedom 10.8, 95% confidence interval).

 Results



One hundre and sixty patients completed the study. Two patients were found to have difficult intubation. In 10 patients McCoy blade was used in a Macintosh style and outside laryngeal pressure was applied. Four patients in Group 3 needed rescue and other measures to control severe hypertension and in 4 patients there was episode of severe hypotension after fentanyl treatment needing posture change to Trendlenbergh position and other measures. Thus all of them were omitted from the result compilation as they did not confirm to the laid protocol. Demographic details are summarized in [Table 1]. There was no significant difference among the groups in age, weight, and preoperative haemodynamics. The haemodynamic data of the four groups is summarized in [Table 2], [Table 3], [Table 4].

Heart rate showed insignificant change at all points ( P =0.848) in Gr. 1 and Gr. 2 where McCoy laryngoscope was used (maximum attained was 88 beats/min in both the groups). Macintosh laryngoscope significantly increased heart rate in Grs. 3 (maximum 103 bpm/73 bpm baseline) and 4 ( P P =0.048) with Macintosh laryngoscope in Gr. 4 as compared to Gr. 3. This significant change was noted post laryngoscopy, after intubation and after 1 minute. In fact the changes in pulse rate were significantly higher ( P P =0.229). Maximum in Gr. 1 was 124 mmHg/119 mmHg baseline and in Gr. 2 was 129 mmHg/121 mmHg baseline. The comparison of Gr. 1 with Gr. 3 ( P P P P P =0.456) as blood pressure remained significantly high from baseline in both the groups (with in the group significance P =0.04). The blood pressure rise was maximum in Gr. 3 immediately after intubation ( P P =0.981). Similarly with in the group changes were non significant in Gr.1 and 2with maximum rising to 78 and 80 mmHg. It rises significantly in Macintosh groups as compared to McCoy ( P P P P et al . that the laryngoscopic view with McCoy laryngoscope suffers when neck is extended.[18] Though Tuckey et al . have emphatically supported that once the laryngoscopic view with McCoy in neutral position is attained there is no need for further manipulation.[19] These manipulations may add unnecessary haemodynamic upheavals, needing medications. Familiarity and learning of correct use of McCoy laryngoscope is fundamental as even with its lever in "on position" one may get tempted to easily use it as Macintosh laryngoscope. As the study was restricted to the period around laryngoscopy and intubation we could not take into account the total dose of narcotics used in the four groups therefore we can not comment on the total opioid requirement during the surgery. Pin manipulation in neurosurgical patients is always done under local anaesthetics. Other limitations include non measurement of plasma levels of the induction agent. In such study proper blinding of the personnel and procedures poses a real problem.

In conclusion, the present study shows the usefulness of McCoy laryngoscope in maintaining the haemodynamics near baseline and the use of fentanyl can be avoided. This corollary may further be extended to minimize the usages of other drugs to attenuate the haemodynamic responses to laryngoscopy and intubation. The findings of this study need to be confirmed by more prospective studies.

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