Comparing Hemodynamic Responses to Intubation in Hypertensive Patients: Clearvue® Video Laryngoscope Versus Macintosh Direct Laryngoscope

Introduction: The ClearVue^® video-laryngoscope (CVL) is believed to alleviate the stress response associated with intubation by providing superior laryngeal views, minimizing oropharyngo-laryngeal stimulation, and potentially reducing the pressor response.

Objective: This study aims to assess and compare how effective and safe intubation is when using a CVL versus a Macintosh direct laryngoscope (MDL) in patients with high blood pressure who are having surgery.

Methods: This prospective, randomized, interventional study was conducted on 140 hypertensive patients on antihypertensive medication undergoing elective surgery under general anesthesia (GA), who were allocated into two groups, CVL group (n = 70) and MDL group (n = 70). Hemodynamic parameters, including mean arterial pressure (MAP), mean heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP), were monitored at baseline, induction, and at various intervals post-intubation (1, 2, 3, 4, 5, and 10 minutes). Other metrics, such as intubation time, intubation attempts, ease of intubation, and associated complications, were documented.

Results: Significant differences in heart rate were observed between the groups, right at intubation and at 1, 2, and 3 minutes post-intubation (p-values: 0.011; 0.028; 0.002; 0.003). SBP showed significant differences at intubation and during the first four minutes post-intubation (p-values < 0.001 except for the fourth minute, p = 0.001). DBP and MBP also showed significant differences at various intervals post-intubation (p-values < 0.001 to 0.025 and < 0.001 to 0.020, respectively). No significant difference in airway complications was noted.

Conclusion: The CVL offers advantages over MDL in patients with controlled hypertension, specifically in reducing hemodynamic changes during intubation without increasing airway complications. At the same time, MDL offered less intubation time overall than CVL.

INTRODUCTION

Laryngoscopy and endotracheal intubation are critical skills for anesthesiologists, especially for unconscious and critically ill patients. However, these procedures can stimulate the sympathetic nervous system, leading to increased catecholamine levels and adverse cardiovascular effects like arrhythmia, hypertension, and tachycardia. The hemodynamic changes during laryngoscopy and intubation are influenced by factors such as oropharyngo-laryngeal stimulation and the force and duration of laryngoscopy. These responses typically begin within 5 seconds, peak within 1-2 minutes, and return to baseline within 5 minutes.

Hypertensive patients are particularly vulnerable to exaggerated catecholamine release, which can increase myocardial oxygen demand and decrease oxygen supply, potentially causing severe cardiovascular events like cardiac arrhythmias, myocardial infarction, pulmonary edema, and cerebrovascular hemorrhage (¹-³). Patients with high blood pressure often have hardening of the arteries and poor blood flow in the throat nerves, making their airway tissues more likely to get hurt during intubation (⁴).

The Macintosh laryngoscope has long been the gold standard for laryngoscopy and intubation (⁵), requiring precise alignment of the oral, pharyngeal, and laryngeal axes and significant force (about 5.4 kg) to expose the glottis. However, newer devices like video laryngoscopes (VL) require significantly less force (0.5-1.4 kg), offering superior laryngeal visualization without the need for such alignment. This reduces oropharyngo-laryngeal stimulation and mitigates the pressor response.

Laryngoscopy and intubation-related stress response can be minimized by several medications such as beta-blockers, clonidine, lignocaine, propofol, and opioids, but nowadays different intubating skills are available, like video laryngoscopy and fiber-optic intubation.

Drugs such as beta-blockers, clonidine, lignocaine, propofol, and opioids are effective in reducing the stress response associated with laryngoscopy and intubation. Modern intubation techniques, such as video laryngoscopy and fiberoptic intubation, enhance patient safety and comfort by reducing the associated stress response, highlighting the importance of adopting these advanced methods (⁶).

METHODS

This prospective, randomized, interventional study was conducted at Swai Man Singh Medical College, Jaipur, India, from August to October 2023. This research has obtained approval from the office of the ethics committee, Swai Man Singh Medical College and attached hospitals, Jaipur (No. 403/MC/EC/2023, dated April 21 st , 2023) and the trial was registered under the Clinical Trial Registry (CTRI) of India with registration number CTRI/2023/06/053510. Informed written consent was obtained from all patients considered for inclusion in the study.

Inclusion criteria included patients of either sex, aged 30 to 60 years, with controlled hypertension (blood pressure (BP) < 140/90 mmHg) on antihypertensive medications and classified as American Society of Anesthesiologist (ASA) Grade II, planned for scheduled surgery under general anesthesia (GA) involving endotracheal intubation.

Criteria for exclusion included the presence of an anticipated difficult airway or intubation (inter-incisor gap < 2.5 cm, Mallampati Grade (MPG) grading 3 & 4), obesity (body mass index (BMI) > 30 kg/m²), history of coronary artery disease, cervicospinal disease, gastroesophageal reflux, chronic respiratory, kidney, and liver diseases, pregnancy, drug allergy, and patients requiring rapid sequence induction (RSI).

Patients were divided into 2 groups using a computer-generated random number sequence list: CVL group (n = 70), intubated with ClearVue® video laryngoscope, and MDL group (n = 70), intubated with Macintosh direct laryngoscope.

All patients underwent evaluation by a cardio-physician to optimize their medication for hypertension and exclude other cardiovascular conditions. At the pre-anesthetic check (PAC) clinic, selected patients were instructed to fast for 8 hours, continue their antihypertensive medications on the preceding night and the morning of surgery with a small amount of water, and take 0.25 mg of Alprazolam the night before surgery. A comprehensive preanesthetic assessment was conducted, including a detailed airway assessment. Measurements such as Modified Mallampati scores (MMP), thyromental distances, and inter-incisor distances were recorded, along with the patients' antihypertensive medication regimens.

Upon arrival in the operating theatre, the patient's fasting status, written informed consent, pre-anesthetic evaluation, and the antihypertensive medication taken before surgery were verified. Standard monitoring devices, including noninvasive blood pressure (NIBP), SPO₂, and echocardiography (ECG) were applied, and baseline hemodynamic parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and SPO₂were documented. An intravenous cannula was also inserted.

The patients were premedicated with intravenous metoclopramide (0.2 mg/kg), midazolam (0.02 mg/kg), glycopyrrolate (0.01 mg/kg), and fentanyl (2 mcg/kg). Pre-oxygenation was performed with 100% oxygen for 3-5 minutes. Hemodynamic parameters were recorded prior to induction, which began with intravenous propofol (2 mg/kg), and then they used atracurium (0.5 mg/kg) to relax the muscles.

Adequate mask ventilation was assured, and laryngoscopy was performed using either the Macintosh or CVL according to the assigned group. Modified Cormack and Lehane grading, intubation time, number of attempts, need for external laryngeal manipulations, and ease of the intubation score were noted. The correct position of the tube was confirmed by 5-point auscultation and EtCO₂readings. Hemodynamic parameters were recorded at specified intervals: during intubation and at 1, 2, 3, 4, 5, 10 minutes postintubation. Complications, including esophageal intubation, mucosal bleeding, lip and dental injury, episodes of desaturation (SPO₂< 92%), ischemia, and bronchospasm, were also documented.

Anesthesia was maintained with sevoflurane (1.5-2.0%) and a 50:50 mixture of O 2 :N 2 O, along with a maintenance dose of Atracurium injection (0.1 mg/kg). At the conclusion of the surgery, all anesthetic agents were stopped, and reversal was achieved using Injection of Neostigmine (0.06 mg/kg) and Injection of Glycopyrrolate (0.01 mg/kg). Patients were then extubated and

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