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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 4  |  Issue : 1  |  Page : 35-39

Comparison of hemodynamic changes during laryngoscopy with McCoy and Macintosh laryngoscopes


Department of Anaesthesia, Dr. D. Y. Patil Medical College, Pune, Maharashtra, India

Date of Submission24-Nov-2016
Date of Acceptance02-Jan-2017
Date of Web Publication1-Feb-2017

Correspondence Address:
Arnab Paul
Department of Anaesthesia, Dr. D. Y. Patil Medical College, Pimpri, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2394-2010.199325

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  Abstract 

Background: The Macintosh blade is one of the most popular blades with a gently curved tongue which extends to the tip. The McCoy blade laryngoscope has a hinge on the tip to avoid the lifting force in the vallecula reducing the amount of force exerted in the vallecula causing less hemodynamic changes. Aim: An attempt had been made to compare hemodynamic changes during laryngoscopy with Macintosh and McCoy laryngoscopes in adult patients undergoing elective surgeries. Settings and Design: It was a prospective, randomized, observational study conducted between October 1, 2013, and April 10, 2015. Materials and Methods: Institutional Ethics Committee approval was taken before the commencement of the study. An informed and written consent was taken from every patient selected for the study. Sixty adults (18–60 years) of both sexes, American Society of Anesthesiologists Grade I and II, undergoing elective surgery under general anesthesia requiring endotracheal intubation were enrolled in this study. Patients were randomly divided into two groups. Group A – where McCoy laryngoscope blade was used for laryngoscopy and Group B – where Macintosh laryngoscope blade was used for laryngoscopy. After induction of anesthesia, laryngoscopy was performed, and trachea was intubated. The change in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) was observed for 10 min post intubation. Statistical Analysis Used: It was done using SPSS. T-test and Chi-square test were applied according to the requirement. The level of significance was fixed at 95%. P < 0.05 was considered statistically significant. Results: McCoy group showed statistically significant lower values of mean HR, SBP, DBP, and MAP till 5 min after intubation when compared to Macintosh group (P < 0.05). Conclusions: HR, SBP, DBP, and MAP all did rise in both the group following laryngoscopy and intubation but changes with McCoy laryngoscope were less and statistically significant when compared to Macintosh laryngoscopes.

Keywords: Hemodynamics, intubation, laryngoscopes


How to cite this article:
Paul A, Nathroy A. Comparison of hemodynamic changes during laryngoscopy with McCoy and Macintosh laryngoscopes . J Health Res Rev 2017;4:35-9

How to cite this URL:
Paul A, Nathroy A. Comparison of hemodynamic changes during laryngoscopy with McCoy and Macintosh laryngoscopes . J Health Res Rev [serial online] 2017 [cited 2019 Dec 11];4:35-9. Available from: http://www.jhrr.org/text.asp?2017/4/1/35/199325


  Introduction Top


Laryngoscopy and tracheal intubation are the most commonly performed procedures by anesthesiologist to secure airway for general anesthesia. However, still anesthesia and endotracheal intubation are considered as stressful conditions which lead to changes in body parameters.

During laryngoscopy and tracheal intubation, cardiovascular changes occur due to the forces exerted by the laryngoscope blade on the base of the tongue when lifting the epiglottis.[1] The hemodynamic changes in vulnerable patients such as ischemic heart disease, and cerebrovascular disease can be dangerous, and it should be avoided. Even in normotensive patients, it gives surgical field with increased oozing from skin incision. The circulatory response to laryngoscopy and intubation is as a result of reflex stimulation of the sympathetic system or vagus nerve, which leads to increase in the myocardial oxygen demand. Anesthetic literature has focused more on the pharmacological methods for obtundation of the response, and literature related to non-pharmacological methods, specifically laryngoscopy blade design, is limited.[2],[3]

The Macintosh blade is one of the most popular blades with a gently curved tongue which extends to the tip. The McCoy blade laryngoscope was introduced in 1993 has a hinge on the tip to avoid the lifting force in the vallecula.[4] It also reduces the amount of force exerted in the vallecula and facilitates tracheal intubation in the neutral position without causing much hemodynamic changes.[5]

In this study, an attempt had been made to compare hemodynamic changes during laryngoscopy with Macintosh and McCoy laryngoscopes in adult patients undergoing elective surgeries.


  Materials and Methods Top


This randomized prospective study was conducted between October 1, 2013, and April 10, 2015. Institutional Ethics Committee approval was taken before the commencement of the study. An informed and written consent was taken from every patient selected for the study. Sample size was calculated using software package NCAA PASS 2000. Thirty patients in each group were required to reach 80% power and 5% level of alpha error to detect a 20% change in blood pressure. Sixty adults (18–60 years) of both sexes, American Society of Anesthesiologists (ASA) Grade I and II, undergoing elective surgery under general anesthesia requiring endotracheal intubation were enrolled in this study. Patients with anticipated difficult intubation (Mallampati Class III and IV, thyromental distance <6 cm, inter-incisor distance <3 cm, and cervical instability), hemodynamically unstable patients, nil by mouth (NBM) status <8 h, obese patients (body mass index >30), laryngopharyngeal lesion, and oropharyngeal surgery were excluded from the study. Patients were randomly divided into two groups depending on the types of laryngoscope blade were used during intubation.

Group A: Where McCoy laryngoscope blade was used for laryngoscopy.

Group B: Where Macintosh laryngoscope blade was used for laryngoscopy.

Randomization was done by computer-generated random numbers and concealed by sealed envelope technique. This was done by a separate anesthesiologist who was not involved in performing laryngoscopy or data collection during the study. Laryngoscopy and intubation were performed by a single senior anesthesiologist in all cases, who was familiar and experienced in intubation using both Macintosh and McCoy laryngoscopes. Due to the nature of the study, true blinding was not possible. However, the person recorded the hemodynamics was not connected to the study.

A detailed routine preanesthetic checkup was done in the preanesthesia checkup clinic. All the routine laboratory investigations were checked. In the preoperative room, the patient's blood pressure and pulse rate were recorded, with the patient lying comfortably in supine position. All patients were kept NBM for a period of at least 8 h before surgery to avoid the risk of aspiration and other anesthesia-related complications.

In the operation theater, pulse oximeter, electrocardiogram (ECG), capnography, and automated noninvasive blood pressure were attached for monitoring, and intravenous access was secured using 20 G IV cannula, and an infusion of dextrose normal saline was started slowly. Demographic data such as age, sex, weight, and height of the patient were noted. Baseline vital parameters, namely, pulse rate (PR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), ECG, SPO2, and EtCO2 were recorded.

A doughnut-shaped pillow was placed under the head of the patient to obtain classical sniffing position. The patient was premedicated by injection glycopyrrolate (0.2 mg), injection midazolam (1 mg), injection ondansetron (4 mg), and injection pentazocine (0.3 mg/kg). The patient was preoxygenated with 100% oxygen for 3 min. Then anesthesia was induced with 2 mg/kg of propofol. Feasibility of ventilation with a face mask was checked before injection of depolarizing muscle relaxant. After ventilation is confirmed, injection succinylcholine 2 mg/kg was administered, and the patient was ventilated with 100% oxygen. The laryngoscopy and intubation were carried out in classical intubating position by a single, trained anesthesiologist. Heart rate (HR), SBP, DBP, and MAP were recorded 30 s before induction, 30 s, 1, 2, 3, 4, 5, and 10 min after laryngoscopy and tracheal intubation, by an independent observer.

Statistical analysis

Statistical analysis was done using SPSS version 11.0. T-test and Chi-square test were applied according to the requirement. The level of significance was fixed at 95%. P< 0.05 was considered statistically significant.


  Results Top


Both the groups were comparable with regard to demographic data, and there was no statistically significant difference among the two groups (P > 0.05). Mean intubation time in both the groups was statistically insignificant (P > 0.05) [Table 1]. Mean HR raised transiently following laryngoscopy and tracheal intubation in both the groups. However, McCoy group showed statistically significant lower values of mean HR 30 s, 1, 2, 3, 4, 5, and 10 min after intubation when compared to Macintosh group (P< 0.05) [Table 2] and [Figure 1]. There were transient increases in mean SBP, DBP, and MAP following laryngoscopy and tracheal intubation in both the groups. However, McCoy group showed statistically significant lower values of SBP, DBP, and MAP 30 s, 1, 2, 3, 4, and 5 min after intubation. However, DBP and MAP at 10 min of intubation were also at the lower side in the McCoy group (P< 0.05) [Table 3], [Table 4], [Table 5] and [Figure 2], [Figure 3], [Figure 4].
Table 1: Demographic data and baseline parameters in – Group A and Group B

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Table 2: Comparison of mean heart rate of the patients in Group A and Group B

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Figure 1: Line diagram showing comparison of mean heart rate in group “A” and group “B”

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Table 3: Comparison of mean systolic blood pressure of the patients in Group A and Group B

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Table 4: Comparison of mean diastolic blood pressure of the patients in Group A and Group B

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Table 5: Comparison of mean arterial pressure of the patients in Group A and Group B

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Figure 2: Line diagram showing comparison of mean systolic blood pressure in group “A” and group “B”

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Figure 3: Line diagram showing comparison of mean diastolic blood pressure in group “A” and group “B”

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Figure 4: Line diagram showing comparison of mean arterial pressure in group “A” and group “B”

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  Discussion Top


The hemodynamic response to laryngoscopy and tracheal intubation has well been observed and studied for almost 75 years. These transient changes can even result to potentially deleterious effect in susceptible patients, particularly those with systemic hypertension, coronary artery disease, and cerebrovascular disease. About half of the patients with coronary artery disease experience episodes of myocardial ischemia during intubation due to alteration of myocardial oxygen demand and supply if no preventive measures are taken.

Over the years, many researchers have adopted various methods for attenuating the pressor response caused by laryngoscopy and tracheal intubation using various inhalational and other pharmacological agents such as beta blockers,[6] calcium channel blockers, lignocaine,[7] gabapentin,[8] nitroglycerin,[9] clonidine,[10] and dexmedetomidine.[11] Both laryngoscopy as well as endotracheal intubation individually contribute to the hemodynamic pressor response. Intubation results in increase in the MAP and plasma noradrenaline level affecting HR more than laryngoscopy.[1] It has also been shown that the type of laryngoscopic blade influences the degree of hemodynamic response.[12]

McCoy et al. compared HR and BP responses between Macintosh and McCoy laryngoscopes following laryngoscopy in twenty ASA Grade 1 or 2 patients. Intubation was not performed, but catecholamine concentration was measured. HR and BP showed a significant increase in the Macintosh group compared to the baseline values, but no significant difference was observed between the two blades. The study sample, however, was small (ten patients in each group), and no justification was provided for the small sample size.[2]

In a study conducted by Tewari et al. in 2005 compared Macintosh and McCoy blades in 160 neurosurgical patients and showed that there were lesser changes in HR and blood pressure with the use of McCoy laryngoscope blade than Macintosh blade when fentanyl was not used in obtundation of response. However, when fentanyl was given as an analgesic, no difference was seen between two blades.[3]

In a study in 2013, Haidry and Khan compared hemodynamic response to tracheal intubation with Macintosh and McCoy laryngoscopes. They found that maximum change in HR and systolic arterial pressure seen in the Macintosh group and changes lasted for a lesser duration in McCoy group.[13]

Sachidananda et al. conducted a study and found that McCoy blade provides better attenuation of hemodynamic response as compared to intubation using the Macintosh laryngoscope as laryngoscopy and intubation can be performed without the aid of stylets.[14]

Our results support the studies with lesser response seen with the use of McCoy laryngoscope. In our study, all the hemodynamic parameters (HR, SBP, DBP, and MAP) raised after laryngoscopy and intubation, but McCoy laryngoscope showed statistically significant lower values of SBP, DBP, and MAP at 30 s, 1, 2, 3, 4, and 5 min after intubation. In McCoy's study, no change in HR was observed. This could be explained by the fact that McCoy et al. studied only the response to laryngoscopy and not tracheal intubation. Tracheal intubation has been shown to affect HR more than laryngoscopy.[1]

In our study, mean intubation time was 20 ± 3.4 versus 18.5 ± 3.5 with Macintosh and McCoy laryngoscope which is statistically not significant (P > 0.05). Hence, we tried to maintain the intubation time equal for both the group as increase in intubation time can lead to increase in hemodynamic response.

Lesser response with McCoy laryngoscope can be of clinical benefit as lesser dose of drugs will be required to attenuate this response, thereby decreasing the side effects associated with drugs such as potent narcotics.

There are some controversies regarding this study. Han et al. and Shimoda et al. conducted studies on hemodynamic effect during laryngoscopy with McCoy and Macintosh laryngoscopes and concluded no difference in the hemodynamic response with two blades.[15],[16] In a study conducted by Buhari and Selvaraj in 2016 concluded that McCoy and Macintosh laryngoscopies have a similar hemodynamic response to direct laryngoscopy and endotracheal intubation.[17]

The limitation of our study was we did not measure the degree of relaxation at the time of intubation which might affect the response. We also included ASA Grade I and II patients to avoid the potential bias that would happen when ASA Grade III and IV patients were included as these patients could affect the hemodynamic response to intubation. We did not measure invasive BP which was not justified to use in ASA Grade I and II patients. Other limitation was the difficulty in blinding with this study design which could have led to a potential bias in the study. However, we ensured that a separate anesthesiologist not knowing the type of laryngoscopy, was involved in data collection.

In this context, a large prospective study is recommended to find out the hemodynamic response to laryngoscopy and intubation separately in patients with hypertension and heart disease patients.


  Conclusions Top


HR, SBP, DBP, and MAP all did rise in both the groups following laryngoscopy and intubation, but changes with McCoy laryngoscope were less and statistically significant when compared to Macintosh laryngoscopes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Shribman AJ, Smith G, Achola KJ. Cardiovascular and catecholamine responses to laryngoscopy with and without tracheal intubation. Br J Anaesth 1987;59:295-9.  Back to cited text no. 1
    
2.
McCoy EP, Mirakhur RK, McCloskey BV. A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade. Anaesthesia 1995;50:943-6.  Back to cited text no. 2
    
3.
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;51:260-4.  Back to cited text no. 3
[PUBMED]  Medknow Journal  
4.
McCoy EP, Mirakhur RK. The levering laryngoscope. Anaesthesia 1993;48:516-9.  Back to cited text no. 4
    
5.
Evans A, Vaughan RS, Hall JE, Mecklenburgh J, Wilkes AR. A comparison of the forces exerted during laryngoscopy using disposable and non-disposable laryngoscope blades. Anaesthesia 2003;58:869-73.  Back to cited text no. 5
    
6.
Parvez G, Ommid M, Gupta AK, Heena H, Hashia AH. Attenuation of the pressor response to laryngoscopy and tracheal intubation with intravenous diltiazem and esmolol intravenous in controlled hypertensive surgical patients. Rev Colomb Anestesiol 2010;38:457-69.  Back to cited text no. 6
    
7.
Mohan K, Mohana RL. Attenuation of cardiovascular responses to laryngoscopy and intubation by diltiazem and lignocaine: A comparative study. Int J Med Res Health Sci 2013;2:557-63.  Back to cited text no. 7
    
8.
Chari VR, Paul A, Gulati M, Garg V. Comparative study of tablet Gabapentin 600 mg and tablet Gabapentin 1000 mg to attenuate the pressor response to laryngoscopy and tracheal intubation. Int J Sci Res 2015;9:21-6.  Back to cited text no. 8
    
9.
Kumari I, Naithani U, Dadheech VK, Pradeep DS, Meena K, Verma D. Attenuation of pressor response following intubation: Efficacy of nitro-glycerine lingual spray. J Anaesthesiol Clin Pharmacol 2016;32:69-73.  Back to cited text no. 9
[PUBMED]  Medknow Journal  
10.
Arora S, Kulkarni A, Bhargava AK. Attenuation of hemodynamic response to laryngoscopy and orotracheal intubation using intravenous clonidine. J Anaesthesiol Clin Pharmacol 2015;31:110-4.  Back to cited text no. 10
[PUBMED]  Medknow Journal  
11.
Bajwa SJ, Kaur J, Singh A, Parmar S, Singh G, Kulshrestha A, et al. Attenuation of pressor response and dose sparing of opioids and anaesthetics with pre-operative dexmedetomidine. Indian J Anaesth 2012;56:123-8.  Back to cited text no. 11
[PUBMED]  Medknow Journal  
12.
Kaur S, Gupta A, Ranjana R. Intubating conditions and stress response to laryngoscopy: Comparison between Macintosh and levering (McCoy's Type) laryngoscope. J Anaesth Clin Pharmacol 2009;25:333-6.  Back to cited text no. 12
    
13.
Haidry MA, Khan FA. Comparison of hemodynamic response to tracheal intubation with Macintosh and McCoy laryngoscopes. J Anaesthesiol Clin Pharmacol 2013;29:196-9.  Back to cited text no. 13
[PUBMED]  Medknow Journal  
14.
Sachidananda R, Umesh G, Shaikh SI. A review of hemodynamic response to the use of different types of laryngoscopes. Anaesth Pain Intensive Care 2016;20:201-8.  Back to cited text no. 14
    
15.
Han TS, Kin JA, Park NG, Lee SM, Cho HS, Chung IS. A comparison of the effects of different type of laryngoscope on haemodynamics. McCoy versus the Macintosh blade. Korean J Anesthesiol 1999;37:398-41.  Back to cited text no. 15
    
16.
Shimoda O, Ikuta Y, Isayama S, Sakamoto M, Terasaki H. Skin vasomotor reflex induced by laryngoscopy: Comparison of the McCoy and Macintosh blades. Br J Anaesth 1997;79:714-8.  Back to cited text no. 16
    
17.
Buhari FS, Selvaraj V. Randomized controlled study comparing the hemodynamic response to laryngoscopy and endotracheal intubation with McCoy, Macintosh, and C-MAC laryngoscopes in adult patients. J Anaesthesiol Clin Pharmacol 2016;32:505-9.  Back to cited text no. 17
[PUBMED]  Medknow Journal  


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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