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| ORIGINAL ARTICLE |
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| Year : 2014 | Volume
: 7
| Issue : 3 | Page : 451-455 |
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The role of intravenous magnesium sulphate in attenuating pressor response to laryngoscopy and intubation in patients undergoing major head and neck surgeries
Rajan Sunil, Shankar Vijay, Paul Jerry
Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, India
| Date of Submission | 29-Mar-2013 |
| Date of Acceptance | 19-May-2014 |
| Date of Web Publication | 27-Aug-2014 |
Correspondence Address:
Rajan Sunil
Additional Professor, Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi 682041, Kerala
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/1687-7934.139595
Background
Elevation in blood pressure and heart rate (HR) following laryngoscopy and tracheal intubation, although brief, may have detrimental effects in high-risk patients.
Aim of the study
To assess the role of intravenous magnesium sulphate in attenuating pressor response to laryngoscopy and intubation in patients undergoing major head and neck surgeries.
Settings and design
This was a randomized, observational, pilot study.
Materials and methods
One hundred patients undergoing major head and neck surgeries were divided into two groups: A and B. Patients in group A received intravenous magnesium sulphate 50 mg/kg body weight 10 min before induction of general anaesthesia and those in group B received intravenous lignocaine 1.5 mg/kg body weight 90 s before intubation. HR, systolic blood pressure, diastolic blood pressure and mean arterial pressures were recorded immediately after starting the intravenous line (baseline), just before induction, 1, 3, 5, 10, 15 and 30 min after intubation.
Statistical analysis
Normal test for means and normal test for significant difference between two proportions were used.
Results
In group A, there was a statistically significant decrease in HR from the preinduction values at 1, 3, 5, 10 and 15 min following intubation. Although there was a decrease in systolic blood pressure, diastolic blood pressure and mean arterial pressures from induction values in both groups, there was no significant difference between the groups.
Conclusion
Intravenous magnesium sulphate effectively attenuated both HR and arterial blood pressure responses to laryngoscopy and intubation compared with intravenous lignocaine. Keywords: intubation, laryngoscopy, lignocaine, magnesium sulphate, pressor response
How to cite this article:
Sunil R, Vijay S, Jerry P. The role of intravenous magnesium sulphate in attenuating pressor response to laryngoscopy and intubation in patients undergoing major head and neck surgeries. Ain-Shams J Anaesthesiol 2014;7:451-5 |
How to cite this URL:
Sunil R, Vijay S, Jerry P. The role of intravenous magnesium sulphate in attenuating pressor response to laryngoscopy and intubation in patients undergoing major head and neck surgeries. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2020 Feb 17];7:451-5. Available from: http://www.asja.eg.net/text.asp?2014/7/3/451/139595 |
| Introduction | |  |
Laryngoscopy and tracheal intubation form an integral part of general anaesthesia. Although the associated elevations in blood pressure (BP) and heart rate (HR) are brief, they may have detrimental effects in high-risk patients.
Aim of the study
To assess the role of intravenous magnesium sulphate in attenuating pressor response to laryngoscopy and intubation in patients undergoing major head and neck surgeries.
| Patients and methods | | |
This was a randomized, observational, pilot study carried out after obtaining the approval of the Hospital Ethical Committee and consent from patients. On the basis of the available data on HR and BP, a total of 800 patients, 400 in each group, were needed for the study to be statistically significant. However, because of the inability to recruit 800 patients undergoing major head and neck procedures, the study was carried out as a pilot study on 100 patients, 50 in each group. Patients undergoing major head and neck surgeries under general anaesthesia with endotracheal intubation, lasting around 8 h, aged 20-50 years, of ASA I and II, were included. Patients in whom difficult airway was anticipated, ASA III or higher and hypertensive patients were excluded.
Patients in group A received intravenous magnesium sulphate 50 mg/kg body weight 10 min before induction and those in group B received intravenous lignocaine at a dose of 1.5 mg/kg body weight 90 s before intubation.
Patients in groups A and B were premedicated with glycopyrrolate 0.2 mg, midazolam 1 mg and morphine 0.1 mg/kg intravenously just before induction using thiopentone sodium 5 mg/kg, followed by suxamethonium 2 mg/kg. The patients were mask ventilated with 1% isoflurane in oxygen. After 1 min, a quick and gentle laryngoscopy, not lasting for more than 15 s, was performed and the trachea was intubated. This was followed by vecuronium 0.08 mg/kg body weight intravenously.
Anaesthesia was maintained in both groups using oxygen and nitrous oxide at a 1 : 3 ratio with isoflurane 1%. The patients were mechanically ventilated to maintain normocarbia with oxygen saturation between 98 and 100%. The study parameters measured were HR, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressures (MAP). They were measured just before securing intravenous access (baseline value), just before induction after administering premedications, 1, 3, 5, 10, 15 and 30 min after intubation.
Magnesium was administered as an infusion over 10 min before induction, whereas lignocaine was administered 90 s before intubation. Thus, in the magnesium group, baseline values and preinduction values were measured 10 min apart as the patients received magnesium during this period. However, in the lignocaine group, preinduction values and baseline values were the same.
Data was analysed using IBM SPSS statistics 20 software. Differences between means were analysed using the normal test for means and the corresponding 'P' values were calculated. The normal test for significant differences between two proportions was also used. The level of statistical significance was a 'P-value' less than 0.05.
| Results | | |
The distribution of patients in both groups was similar with respect to demographics and type of surgery. The HR, SBP, DBP and MAP at the time of insertion of intravenous access were comparable between the two groups [Table 1]. | Table 1: Comparison of heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure at insertion of intravenous access
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When the mean preinduction parameters were compared, the magnesium group showed a significantly increased mean HR (94.81 vs. 86.84) and a significantly decreased mean SBP (125.84 vs. 134.82) from the baseline compared with the lignocaine group. The mean preinduction DBP and MAP were lower in the magnesium group, but the differance was not significant [Table 2].
As the preinduction HR and SBP differed significantly between the two groups, the percentage differences in the values from the preinduction were studied. The mean values of percentage change HR in the magnesium group in 1 min (3.82 ± 24.77) differed significantly from that of the lignocaine group at 1 min (-14.73 ± 24.04, P<0.001). The same observation was made at 3, 5, 10 and 15 min following induction. At 30 min, percentage change in the mean HR in the magnesium group did not differ significantly from the lignocaine group [Table 3], [Figure 1]. | Table 2: Comparison of preinduction heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure
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 | Table 3: Comparison percentage difference in the mean heart rate from preinduction heart rate
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At 1 min following induction, the comparison of percentage change in the mean SBP in the magnesium group (8.47 ± 8.08) differed from the lignocaine group (7.74 ± 9.45), but the difference was not significant statistically (P = 0.679). The same observation was consistent up to 30 min (P > 0.05) [Table 4], [Figure 2]. The comparison of percentage change in the mean DBP at 1, 3, 5, 15 and 30 min showed no significant difference between groups. However, at 10 min, there was a difference in the percentage change of the mean DBP in the magnesium group (16.06 ± 5.78) when compared with the lignocaine group (9.61 ± 11.53) that was statistically significant (P < 0.001) [Table 5], [Figure 3]. The comparison of percentage change in the mean MAP up to 30 min also showed no significant difference between groups [Table 6], [Figure 4]. | Table 4: Comparison of percentage difference in the mean systolic blood pressure from preinduction systolic blood pressure
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 | Table 5: Comparison of percentage difference in the mean diastolic blood pressure from preinduction diastolic blood pressure
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 | Table 6: Comparison of percentage difference in the mean arterial pressure from preinduction mean arterial pressure
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| Discussion | | |
It is well known that laryngoscopy, endotracheal intubation and surgery result in a marked increase in HR and systemic arterial pressures. These effects are mainly because of the release of catecholamines. Magnesium inhibits catecholamine release from the adrenergic nerve endings and from the adrenal medulla. It is also involved in the control of vasomotor tone, cardiac excitability and neurotransmitter release. In many of its actions, it is likened to a physiological calcium antagonist [1].
Administration of magnesium sulphate preoperatively has also been proven to reduce the haemodynamic response to endotracheal intubation [2,3]. The effectiveness of magnesium sulphate in hypotensive anaesthesia and in reducing the requirement of anaesthetics, analgesics and muscle relaxants intraoperatively has been proven [4-11]. It causes a reduction in HR, BP, blood loss and duration of functional endoscopic sinus surgery [12,13].
In this study, we found that the preinduction HR following the administration of magnesium sulphate increased significantly from the baseline values. This finding was similar to that obtained by Kumar et al. [14] and Kothari et al. [15] The increase in HR with magnesium sulphate could be attributed to the inhibition of action of acetylcholine on the heart. Similarly, hypotension following the administration of magnesium sulphate in the preinduction period was also in agreement with previous studies [2,14], which could be attributed to its inhibitory effect on catecholamine release as well as its vasodilatory properties.
The preinduction HR in group A showed a statistically significant increase from the baseline value and preinduction BP showed a significant decrease from the baseline values. These findings can be attributed to the intravenous administration of magnesium sulphate in group A during this period. Kothari et al. [15] also reported an initial increase in HR with the administration of magnesium sulphate in the preinduction period. However, in group B, there was no difference between baseline and preinduction values as the patients in this group did not receive any drugs during this period.
The decrease in SBP from the preinduction value was greater in the magnesium group than the lignocaine group at 1, 3, 5 and 10 min. This was in contrast to other studies in which the SBP seemed to increase from preinduction values with magnesium. However, in the present study, at 15 and 30 min, the decrease in SBP was greater for the lignocaine group. As the surgical stimulus would have been initiated within 15 min of intubation, we could not reliably account for this disparity.
There was a decrease in DBP and MAP in both groups from the preinduction values, with the decrease being greater for magnesium at 1, 3, 5 and 10 min. This result was also in contrast to other studies that showed an insignificant increase in BP from preinduction values with magnesium following intubation.
Our study group included patients undergoing major head and neck surgeries that lasted at least 8 h, who were planned to be electively ventilated postoperatively owing to the long duration of surgery and postoperative airway compromise. Thus, the safety in terms of the use of magnesium sulphate as an agent to blunt haemodynamic response in shorter duration surgeries could not be assessed conclusively. We have not studied whether the prolongation of neuromuscular blockade by magnesium sulphate would limit its use in routine cases as most of the cases in our study underwent elective ventilation postoperatively.
Although not part of our study, we observed that there was a notable reduction in intraoperative requirements for opioids and muscle relaxants. At the same time, as the intraoperative BPs remained on the lower side, there was less demand from the surgeons for induced hypotension during tumour resections.
| Conclusion | | |
It is concluded that intravenous magnesium sulphate effectively attenuated both HR and arterial BP responses to laryngoscopy and intubation compared with intravenous lignocaine. Thus, we recommend the administration of intravenous magnesium sulphate as a safe and effective method for attenuating stress response to laryngoscopy and intubation in patients undergoing major head and neck surgeries until future research indicates any presently unidentified deleterious effects of intravenous magnesium administration.
| Acknowledgements | | |
| References | | |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]
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