Effect of Preinduction Single-Dose Intravenous Magnesium Sulphate on Haemodynamic Response to Pneumoperitoneum in Patients Undergoing Laparoscopic Cholecystectomy.

Laparoscopic cholecystectomy has become the gold standard treatment for symptomatic gallstone disease owing to reduced postoperative pain, shorter hospital stay, and faster recovery compared to open surgery. Nevertheless, the creation of carbon dioxide pneumoperitoneum is associated with marked cardiovascular changes resulting from increased intra-abdominal pressure and neurohumoral activation.

Pneumoperitoneum causes an increase in systemic vascular resistance, mean arterial pressure, and heart rate through stimulation of the sympathetic nervous system and release of catecholamines and vasopressin. These haemodynamic responses may be well tolerated in healthy individuals but can precipitate myocardial ischemia, arrhythmias, or heart failure in susceptible patients.

Various pharmacological agents including opioids, beta blockers, calcium channel blockers, clonidine, dexmedetomidine, nitroglycerin, and magnesium sulphate have been investigated to attenuate these responses.

Magnesium sulphate acts as a physiological calcium antagonist, inhibits catecholamine release from adrenal medulla and peripheral nerve endings, causes vasodilation, and antagonizes NMDA receptors, thereby reducing nociception and sympathetic stimulation. Although continuous magnesium infusion has shown favourable results, studies evaluating the efficacy of a single preinduction dose remain limited.

The present study was undertaken to evaluate whether a single intravenous dose of magnesium sulphate administered before induction can effectively attenuate haemodynamic responses during pneumoperitoneum.

Aim and Objectives

Primary Objective

To evaluate the effect of preinduction intravenous magnesium sulphate on haemodynamic responses during pneumoperitoneum.

Secondary Objectives

·         To compare heart rate between the groups.

·         To compare SBP, DBP and MAP.

·         To observe adverse effects.

·         To assess postoperative analgesic requirement.

Study Design

Prospective randomized double-blind controlled study.

Study Population

Sixty adult patients posted for elective laparoscopic cholecystectomy.

Inclusion Criteria

·         Age 18–60 years

·         ASA Grade I and II

·         Elective laparoscopic cholecystectomy

Exclusion Criteria

·         Hypertension

·         Ischaemic heart disease

·         Renal dysfunction

·         Hepatic dysfunction

·         Neuromuscular disorders

·         Pregnancy

·         Magnesium allergy

Patients were randomized using computer-generated random numbers into two equal groups.

Group MG (n=30)

Magnesium sulphate 50 mg/kg diluted in 100 mL normal saline infused over 10 minutes before induction.

Group CG (n=30)

100 mL normal saline infused over 10 minutes before induction.

Standard general anaesthesia was administered in both groups.

Haemodynamic variables were recorded:

·         Baseline

·         Before pneumoperitoneum

·         5 minutes

·         10 minutes

·         15 minutes

·         20 minutes

·         End of surgery

Statistical Analysis

Data were analysed using SPSS software.

Continuous variables were expressed as Mean ± Standard Deviation.

Student's t-test was used for comparison between groups.

Repeated measures ANOVA was used for serial haemodynamic measurements.

Categorical variables were analysed using Chi-square test.

P value <0.05 was considered statistically significant.

Table 1. Demographic Characteristics

Table 2. Heart Rate

Table 3. Systolic Blood Pressure

Table 4. Diastolic Blood Pressure

Table 5. Mean Arterial Pressure

Table 6. Adverse Effects

The present study evaluated the efficacy of a single preinduction intravenous dose of magnesium sulphate in attenuating haemodynamic responses to pneumoperitoneum during laparoscopic cholecystectomy. The findings demonstrated significantly lower heart rate and blood pressure values in patients receiving magnesium sulphate compared with the control group, indicating effective attenuation of sympathetic responses.

The demographic characteristics of both groups were comparable, minimizing potential confounding factors.

The observed attenuation of haemodynamic responses can be explained by the pharmacological properties of magnesium. Magnesium inhibits calcium influx into vascular smooth muscle cells, producing vasodilation. It also suppresses catecholamine release from adrenergic nerve terminals and the adrenal medulla and acts as an NMDA receptor antagonist, thereby reducing sympathetic activation and nociceptive transmission.

The findings of the present study are consistent with those reported by Jee et al. (2009), who demonstrated that intravenous magnesium sulphate significantly reduced arterial pressure increases during laparoscopic cholecystectomy compared with placebo. Their study concluded that magnesium provided better haemodynamic stability without significant adverse effects.

Similarly, Junghans et al. (2006) systematically evaluated different methods of minimizing haemodynamic alterations during pneumoperitoneum and emphasized that pharmacological attenuation of sympathetic responses improves intraoperative cardiovascular stability. Magnesium sulphate was identified as one of the promising agents due to its vasodilatory and sympatholytic effects.

Our findings also agree with Telci et al. (2002), who demonstrated that magnesium infusion reduced anaesthetic requirements and improved perioperative haemodynamic stability in patients undergoing major surgery. Koinig et al. (1998) reported reduced postoperative analgesic requirements following perioperative magnesium administration because of NMDA receptor antagonism. Although postoperative analgesia was not the primary outcome of the present study, the analgesic properties of magnesium may provide an additional clinical advantage.

Likewise, Ryu et al. (2008) found that magnesium sulphate attenuated cardiovascular responses during laparoscopic surgery and reduced perioperative opioid consumption. No clinically significant adverse effects such as severe hypotension, bradycardia, respiratory depression, or delayed recovery were observed in the magnesium group, supporting the safety of a single preinduction dose of 50 mg/kg in ASA I and II patients.

The present study therefore reinforces the role of magnesium sulphate as a simple, inexpensive, and effective adjunct for maintaining haemodynamic stability during laparoscopic surgery.

Limitations

·         Small sample size.

·         Single-centre study.

·         Only ASA I and II patients were included.

·         Serum magnesium levels were not measured.

·         Postoperative pain scores and analgesic consumption were not analysed in detail.

Administration of a single intravenous dose of magnesium sulphate (50 mg/kg) before induction significantly attenuated the haemodynamic responses associated with pneumoperitoneum during laparoscopic cholecystectomy. Magnesium sulphate maintained heart rate and arterial blood pressure closer to baseline values without significant adverse effects. Owing to its efficacy, safety, ease of administration, and low cost, magnesium sulphate can be considered a useful adjunct in general anaesthesia for laparoscopic procedures.

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