Comparative Study between Magnesium Sulfate and Lidocaine for Controlled Hypotension during Functional Endoscopic Sinus Surgery: A Randomized Controlled Study.

BACKGROUND: Intraoperative bleeding impairs surgical field visibility during functional endoscopic sinus surgery (FESS); several methods have been used to decrease blood loss and improve surgical field, one of them is usage of hypotensive anesthetic agents. AIM: We intended to compare magnesium sulfate with lidocaine, regarding their efficiency in inducing controlled hypotension and providing a better surgical field exposure during FESS and the influence of their usage on extubation time. SETTINGS AND
DESIGN: This study design was a prospective randomized controlled double-blinded clinical study. PATIENTS AND METHODS: Eighty adult patients with patients' physical status ASA Classes I and II, aged 20-50 years scheduled for FESS were randomly divided into two study groups; each group contains 40 patients: Group L received lidocaine 2 mg/kg/h with maximum of 200 mg/h starting at induction of anesthesia and continuing until the end of surgery and Group M received an iv bolus of magnesium sulfate 50mg/kg in a total of 100ml saline over 10 min followed by infusion of 15mg/kg/h until the end of surgery; patients were observed for the quality of the surgical field, blood loss, and extubation time. STATISTICAL ANALYSIS USED: Student's t-test or Mann-Whitney's U, Chi-square, or Fisher's exact tests were used.
RESULTS: Group L showed a significant decrease in blood loss (P = 0.01), better surgical field clarity (P = 0.002), and shorter extubation time (P = 0.001) than Group M, but there was no statistically significant difference between the two study groups as regards hemodynamics.
CONCLUSION: We concluded that both magnesium sulfate and lidocaine successfully induced controlled hypotension in patients undergoing FEES, but lidocaine provided better surgical field clarity and shorter extubation time.

INTRODUCTION

Functional endoscopic sinus surgery (FESS) is surgical management for chronic rhinosinusitis. Various methods have been used to improve the surgical field, such as patient positioning in reverse Trendelenburg, decongesting the nose, infiltrating the lateral nasal wall with lidocaine and epinephrine, or using the hypotensive anesthesia technique.[1] FESS is better to be performed under controlled hypotensive technique (mean arterial pressure [MAP] between 60 and 70 mmHg); this can improve surgical field and decrease the operation time.[2] Several medications have been used to provide controlled hypotension such as inhalational volatile agents,[3] remifentanil,[4] clonidine,[5] dexmedetomidine,[6] nitroglycerine,[7] esmolol,[8] intravenous lidocaine,[9] and magnesium sulfate.[101112]

Lidocaine is one of the most commonly used amide anesthetics. It can be safely given systemically to treat ventricular arrhythmias[13] and blunt the pressor response to endotracheal intubation.[14] Hypotension has been observed to occur after submucosal injection of lidocaine.[1516] Systemic lidocaine was effective in producing controlled hypotension.[9]

Magnesium sulfate is a good drug for controlled hypotension, as it stabilizes the cell membrane and intracytoplasmic organelles by mediating the activation of Na+-K+ ATPase and Ca++ ATPase enzymes, which have important role in transmembrane ion exchange during the depolarization and repolarization phases,[41117] and also, Mg++ inhibits the release of norepinephrine by blocking the N-type Ca++ channels at nerve endings which decrease the blood pressure.[18]

The aim in this study was to compare magnesium sulfate with lidocaine, regarding their efficiency in inducing controlled hypotension and providing a better surgical field exposure during FESS and the influence of their usage on extubation time.

PATIENTS AND METHODS

The Ethical Committee of our institute approved this randomized prospective double-blinded controlled study to be executed in Fayoum University Hospital for 2 years (from February 2016 to April 2018) on 80 patients scheduled for FESS after obtaining a written informed consent for anesthesia from each patient after explaining to them the nature of study and complications.

Inclusion criteria included patients aged 18–60 years, weighted 55–85 kg, and with physical status ASA Classes I and II scheduled for FESS.

Exclusion criteria included patients with anemia (hemoglobin concentration <10 gm/dl), systemic hypertension, significant cardiovascular diseases, renal diseases, diabetes mellitus, and hepatic diseases.

The patients were randomly divided into two equal groups, and each group contains 40 patients: Group L received lidocaine 2 mg/kg/h with maximum of 200 mg/h starting at induction of anesthesia and continuing until the end of surgery and Group M received an iv bolus of magnesium sulfate 50 mg/kg in a total of 100ml saline over 10 min followed by infusion of 15 mg/kg/h until the end of surgery.

The following parameters were measured: (i) hemodynamics: Heart rate (HR) and main arterial pressure (MAP) every 10 min interval; (ii) surgical field clarity: bleeding in the surgical field and the quality of the visibility were measured subjectively every 15 min by the surgeon who was blinded to the infused drug using 6 points by Fromme and Boezaart scale[19] [Table 1]; (iii) intraoperative blood loss: The blood aspirated from the surgical area was collected and measured, and nasal tamponades soaked with blood were counted (each tamponade used was assumed to contain approximately 4 ml of blood); and (iv) the extubation time: the time from discontinuation of isoflurane till the removal of the endotracheal tube.

Table 1

Fromme and Boezaart scale

The primary outcomes of this prospective, randomized, and observer-blinded study were to compare the quality of the surgical field between groups. The secondary outcomes of this study were to compare the blood loss and extubation time between groups.

Statistical analysis

Sample size was calculated using G power program 3.1.9.2. Data were analyzed using IBM SPSS advanced statistics (Statistical Package for Social Sciences), version 21 (SPSS Inc., Chicago, IL, USA).

Data were collected, coded, and double entered into Microsoft Excel, and data analysis was performed using SPSS software version 21.0 (IBM Corporation, Armonk, NY, USA) statistics. Simple descriptive analysis in the form of numbers and percentages for qualitative data and arithmetic means as central tendency measurement was used. Standard deviations as measure of dispersion and inferential statistic test were used for quantitative parametric data. For quantitative parametric data, independent Student's t-test used to compare measures of two independent groups of quantitative data. For qualitative data, Chi-square test was used to compare two or more than two qualitative groups. The P < 0.05 was considered significant.

RESULTS

Eighty patients were included in our study and were randomly divided into two groups, and each group has 40 patients.

There was no statistically significant difference between the two study groups as regards the demographic data (sex, age, weight, height, and ASA) as shown in Table 2.

Table 2

Demographic data (age, weight, height, gender, and American Society of Anesthesiologists)

Heart rate

The baseline HR showed no significant difference between two groups. After induction, HR significantly decreased (about 25%) from the baseline measurements in the two groups and then increased again after tracheal intubation. The HR showed almost constant course throughout the intraoperative period in both groups, but Group L showed a lower decrease in HR than Group M, and the difference was statistically significant [Figure 1].

Figure 1

Heart rate changes in both groups

Mean arterial blood pressure

MAP showed no significant difference between both groups preoperatively and after induction of anesthesia. MAP showed a significant decrease in Group L than Group M after intubation. The intraoperative MAP showed no significant difference between the two groups [Figure 2].

Figure 2

Intraoperative mean arterial blood pressure

Operative field clarity

According to Fromme bleeding score, the operative field clarity was significantly better in Group L when compared to Group M [Table 3].

Table 3

Operative field clarity

Blood loss

The amount of blood loss was statistically significant lower in Group L when compared to Group M as shown in Table 4.

Table 4

Blood loss in both groups

Extubation time

There was a statistically significant difference between the two study groups regarding extubation time being longer in the Group M [Table 5].

Table 5

Comparison of the extubation time between the two study groups

DISCUSSION

FESS is better to be done under controlled hypotensive technique (mean arterial blood pressure [MAP] between 60 and 70 mmHg); this can improve surgical field and decrease the operation time.[2] Several medications have been used to provide controlled hypotension such as inhalational volatile agents,[3] remifentanil,[4] clonidine,[5] dexmedetomidine,[6] nitroglycerine,[7] esmolol,[8] intravenous lidocaine,[9] and magnesium sulfate.[101112]

The current study shows the comparison between magnesium sulfate and lidocaine regarding their efficiency in inducing controlled hypotension and providing a better surgical field exposure during FESS and the influence of their usage on postoperative pain and extubation time.

In our study lidocaine provided better control in HR and blood pressure, and operative field clarity and the amount of blood loss were significantly better in the lidocaine group when compared to the magnesium sulfate group.

These results correspond with Omar[9] study that found lidocaine infusion is an effective method in producing deliberate hypotension in patients scheduled for FESS surgery and providing good surgical field.

Moreover, there is evidence that lidocaine can produce vasoconstriction in human. Jorfeldt et al.[20] found that total systemic vascular resistance increased at plasma lidocaine concentrations of 3–6 mcg/kg, and they postulated that vasoconstriction in some parts of the peripheral circulation should have happened. The doses used in our study were used in previous studies and provided serum lidocaine levels <4 mcg/ml.[21] These plasma lidocaine concentrations could have caused mucosal vasoconstriction in the nasal sinuses and consequently produced better surgical fields.

There are two mechanisms of lidocaine to induce hypotension. The first mechanism is local anesthetics ability to produce dose-dependent negative inotropic effect on the heart by affecting calcium influx.[22] This negative inotropic action of lidocaine may be aggravated by a similar effect of volatile anesthetics. The second mechanism is lidocaine ability to blunt the airway's reflexes to endotracheal tube.[23]

On the other hand, Mesbah Kiaee et al.[24] founded that the administration of magnesium sulfate might result in maintaining hemodynamic stability after endotracheal intubation in elective coronary artery bypass grafting in comparison with lidocaine.

Magnesium sulfate is a good option for controlled hypotension, as it stabilizes the cell membrane and intracytoplasmic organelles by mediating the activation of Na+-K+ ATPase and Ca++ ATPase enzymes, which have important role in transmembrane ion exchange during the depolarization and repolarization phases,[41117], and also, Mg++ inhibits the release of norepinephrine by blocking the N-type Ca++ channels at nerve endings which decrease the blood pressure.[18]

Our limitation was a small sample size, and more studies with larger sample sizes will be needed to confirm our results. The second was postoperative magnesium sulfate, and calcium levels were not measured.

We recommend to study the combination of magnesium sulfate and lidocaine as a technique for hypotensive anesthesia.

Lidocaine provided good controlled hypotension, better surgical field quality, less blood loss, and also postoperative analgesia, so it is better than many drugs that provide hypotension with reflex tachycardia and drugs that provide delayed recovery.

CONCLUSION

We concluded that both magnesium sulfate and lidocaine successfully induced controlled hypotension in patients undergoing FEES, but lidocaine provided better surgical field clarity and shorter extubation time.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.