Evaluation of intravenous magnesium sulphate on haemodynamic responses to laryngoscopy and tracheal intubation in surgeries of ear, nose and throat

Introduction

Due to the stimulation of the sympathetic-adrenal system, airway manipulation techniques such as laryngoscopy and orotracheal intubation cause a reflexive sympathetic reaction. This reaction may affect the neurohumoral and cardiovascular systems in various manners. The consequences include vasoconstriction, an increase in cardiac workload, a rise in the demand for coronary blood flow, and constricted coronary arteries that are incapable of withstanding this greater flow. As a result, the myocardium may not get enough oxygen in certain areas. Elevated blood pressure, rapid heart rate, and high levels of adrenaline and norepinephrine are the most prominent outcomes of this response.^1–4 This response is usually transient, but elderly individuals and those with specific medical conditions—diabetes, heart failure, systemic arterial hypertension, coronary artery disease, cardiac arrhythmias, cerebrovascular disease, and pulmonary disorders—may be more susceptible to arrhythmias, myocardial ischemia or infarction, and cerebral haemorrhage.⁵

Many strategies are being used to mitigate the hemodynamic reactions secondary to laryngoscopy and intubation. Utilizing various pharmacological techniques, such as topical anesthesia, narcotics, adrenoreceptor blockers, calcium channel blockers, sodium channel blockers, vasodilators like nitroglycerin, intravenous magnesium sulphate, and paracetamol, as well as ensuring deep anesthesia is among them.⁶

Recently, it has been shown that magnesium sulphate, a medication used to prevent seizures in eclamptic patients, may also decrease the stress reactions brought on by tracheal intubation and laryngoscopy when given in small quantities.^7–9 Inhibiting the adrenal glands’ secretion of catecholamines, magnesium sulphate (MgSO₄) lowers the amount of adrenaline in the blood. Consequently, bradycardia, vasodilation, and atrial contractions are reduced.^10–12 Therefore, in cases where other medications might not be appropriate, magnesium sulphate can be considered an alternative to other medicines for reducing the pressor response caused by laryngoscopy and tracheal intubation.

Methods

Study design – A prospective, randomized, double-blind clinical trial.

Study period – Two years.

Study setting – Department of Anaesthesiology in AVBRH and JNMC, Sawangi, Wardha.

Allocation of patients – Patients will be allotted to the study groups by computer-generated randomization.

Study population – The study will be conducted on patients undergoing elective ENT surgeries, fulfilling the following.

Sample size calculation

The website openepi.com was used to calculate the sample size (see Figure 1). Presuming mean arterial pressure immediately after intubation, a sample of 19 patients will be required to detect a minimum of 10% difference in the mean arterial pressure. The study will be conducted on a total of 50 patients to account for any possible dropouts.

Figure 1. Sample size for comparing two means.

Discussion

This research protocol aims to add to the growing body of information on physiological stress response attenuation during tracheal intubation and laryngoscopy. In this discussion, we examine the results from previous studies, drawing similarities and contrasts and determining the potential importance of our research. The effectiveness of intravenous magnesium sulphate in decreasing heart rate and arterial blood pressure to laryngoscopy in patients having head and neck procedures was reported by Sunil et al.¹³ This study established the foundation for magnesium sulfate’s potential usage. According to Misganaw et al.,¹⁴ administering magnesium sulphate and lidocaine pre-emptively effectively reduced the hemodynamic reactions caused by laryngoscopy and intubation. Notably, this study assessed the relative efficaciousness of lidocaine and magnesium sulphate, offering valuable information. In a dose-response investigation, Honarmand et al.¹⁵ discovered that magnesium sulphate, given in varying amounts, significantly reduced fluctuations in arterial pressure after laryngoscopy and intubation. Alterations in heart rate, however, were not significantly impacted. To assess the effectiveness of sublingual nitroglycerin and magnesium sulphate in reducing pressor responses, Kotwani et al. conducted a study.⁷ They discovered that both therapies were successful despite a brief increase in heart rate, highlighting that these responses were dose-dependent. The research conducted by Sen and Sen (2022) presents dexmedetomidine as a viable prophylactic method for reducing hemodynamic reactions to laryngoscopy and intubation during neurosurgery.⁶

If the proposed study’s results are per previous studies, they could have significant therapeutic implications. They might result in the development of consistent regulations for controlling physiological responses to stress during tracheal intubation and laryngoscopy. Physicians could choose interventions, dosage, and patient groups with more excellent knowledge. It is critical to recognize the possible drawbacks demonstrated by the preceding investigations, including individual variability and the setting of the processes. More research needs to be employed to understand the dose-dependent transitory rise in heart rate.

In summary, the study protocol can significantly contribute to the fields of anesthesia and critical care. It broadens previous research findings, provides fresh perspectives on dosage, and presents a novel strategy, giving medical professionals access to a broader range of therapeutic options. With the potential to improve patient outcomes and safety during laryngoscopy and tracheal intubation, the approach holds significant potential to enhance patient safety.