Ain-Shams Journal of Anaesthesiology

: 2017  |  Volume : 10  |  Issue : 1  |  Page : 124--130

Hypotensive anesthesia during functional endoscopic sinus surgery: a comparative study of remifentanil versus magnesium sulfate infusion

Michel B. Zaky, Amir K.E. Saleh 
 Department of Anesthesia, Faculty of Medicine, Ain Shams University, Cairo; Department of Anesthesia, Alsalama Hospital, Abu Dhabi, Egypt

Correspondence Address:
Michel B. Zaky
Department of Anesthesia, Alsalama Hospital, PO Box 46266, Abu Dhabi


Objective The aim of this study was to compare the adequacy and outcome of controlled hypotensive anesthesia using remifentanil or magnesium sulfate during functional endoscopic sinus surgery (FESS). Patients and methods The study included 104 patients with chronic rhinosinusitis assigned for FESS. They were randomly divided into two equal groups: group R received remifentanil loading dose of 1 μg/kg over 60 s, followed by 0.15 μg/kg/min infusion, and group M received magnesium sulfate loading dose of 40 mg/kg over 10 min, followed by 15 mg/kg/h infusion. Hemodynamic variables were noninvasively monitored and expressed every 15 min. Operative field bleeding and subsequently its visibility were graded using a six-point scale. Recovery time was estimated as the time until the patient achieves a modified Aldrete scoring of 11 or more. The degree of sedation was assessed using the Brussels Sedation Scale. Results The mean collective heart rate and mean arterial pressure measures were signifi cantly low in group R compared with group M. The mean amount of collected blood loss and total field visibility scale score were significantly lower with remifentanil than with magnesium sulfate. The frequency of patients who achieved early recovery was significantly higher with remifentanil with significantly shorter time to achieve modified Aldrete scoring of 11 or more compared with magnesium sulfate. Conclusion Controlled hypotensive anesthesia minimized bleeding and provided excellent fi eld visibility during FESS. Remifentanil provided superior outcome manifested as signifi cant reduction in operative field bleeding, better field visibility, and shorter operative time compared with magnesium sulfate. In addition, remifentanil provided early recovery without postoperative sedation and thus allowed FESS to be conducted as a day-case surgery.

How to cite this article:
Zaky MB, Saleh AK. Hypotensive anesthesia during functional endoscopic sinus surgery: a comparative study of remifentanil versus magnesium sulfate infusion.Ain-Shams J Anaesthesiol 2017;10:124-130

How to cite this URL:
Zaky MB, Saleh AK. Hypotensive anesthesia during functional endoscopic sinus surgery: a comparative study of remifentanil versus magnesium sulfate infusion. Ain-Shams J Anaesthesiol [serial online] 2017 [cited 2021 Apr 18 ];10:124-130
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Chronic sinusitis not responding to medical treatment and nasal polyposis are two classical indications for performing functional endoscopic sinus surgery (FESS). FESS provides the advantage of good illumination and clear vision with minimally invasive surgery, and hence it is possible to achieve consistently good results. FESS also offers clear advantages in reducing complications and recurrence rates in frontal sinus disease even in revision cases [1],[2].

Moreover, FESS is advantageous in the recovery of antral mucosa, improvement of mucociliary clearance for both types of antral mucosa, and improved ventilation and drainage. Furthermore, FESS induced marvelous symptomatic outcome in the form of a significant decrease in headache and sinonasal outcome test scores [3],[4].

Operative field visibility is a major determinant for FESS outcome and is related to the amount of operative bleeding, which interferes with operative field visibility and could be a major obstacle for success of FESS. Numerous interventions are performed with general anesthesia for FESS, aiming at reducing intraoperative bleeding and improving field visibility. Hypotensive anesthesia is one modality for the control and reduction of bleeding during surgery. The state of ‘hypotension’ was achieved by reducing the peripheral blood vessel resistance, reducing the heart rate (HR) per minute, and by intercoordinating these two effects.

Most frequently, peripheral vasodilators, β-blockers, and volatile anesthetics are used to cause induced hypotension [5],[6].

Magnesium is a unique calcium antagonist as it can act on most types of calcium channels in vascular smooth muscle. Decreased calcium channel activity lowers intracellular calcium, causing relaxation and vasodilatation. In endothelium, magnesium has been shown to increase the production of prostaglandin I2, which in turn decreases platelet aggregation. Magnesium also increases nitric oxide production causing vasodilatation [7]. Hypotension during the administration of remifentanil could be attributed to the direct effects of remifentanil on regional vascular tone that may play a role in promoting hypotension and/or to reductions in sympathetic outflow [8],[9].

The current study aimed to compare the adequacy and outcome of controlled hypotensive anesthesia using either remifentanil or magnesium sulfate during FESS.

 Patients and methods

After approval of the local ethical committee, this study was conducted from June 2011 to February 2014 in Alsalama Hospital, Abu Dhabi, United Arab Emirates. This prospective, blind, randomized, controlled study included 104 patients of both sexes of American Society of Anesthesiologists (ASA) physical status I and II with chronic rhinosinusitis scheduled for elective FESS surgery.

We obtained informed consent from each patient before the procedure.

After thorough preanesthetic evaluation, patients were randomly assigned to two groups of 52 patients each using a computer-generated random table. Group R received remifentanil infusion and group M received magnesium sulfate infusion. In group R, intravenous administration of remifentanil loading dose of 1 μg/kg over 60 s was followed by remifentanil continuous infusion administered at a rate of 0.15 μg/kg/min. In group M, patients received intravenous magnesium sulfate bolus of 40 mg/kg followed by a 15 mg/kg/h continuous infusion; both infusions were prepared by hospital clinical pharmacist.

All patients were administered premedication with intravenous midazolam 1–2 mg 30 min before surgery. On arrival of the patient to the operation theater, pulse oximeter, noninvasive blood pressure, and ECG leads were attached. Baseline HR, systolic, diastolic, mean blood pressure, and oxygen saturation (SPO2) were recorded. A crystalline intravenous infusion of 6–8 ml/kg was started. After preoxygentaion for 3 min, anesthesia was induced with propofol 2 mg/kg, followed by cis-atracurium (0.15–0.2 mg/kg), to facilitate direct laryngoscopy and tracheal intubation. Anesthesia was maintained with sevoflurane 0.5–1 MAC, with 50% N2O in oxygen. The patients were mechanically ventilated to maintain the normocapnia (ETCO2 between 35 and 40 mmHg). In both groups, surgical stimulation was started 10 min after induction of anesthesia to avoid the effects of early surgical manipulation on HR and blood pressure and to give time space for injection of the loading doses of both drugs completely.

Immediately after tracheal intubation, the head of the operation table was elevated to 30°, and maxillary sinus cavity was packed under endoscopic guidance using adrenaline-soaked pledgets (1: 100 000) to obtain maximum contraction of the mucosa. Thus, better visualization of the main features of the cavity was obtained. After 5 min, the pledgets were removed, and xylocaine (1%) with adrenaline (1: 100 000) (1–1.5 ml) was injected under the mucosa of the uncinate process at the level of the head of the middle turbinate and the inferior part of the bulla. The local anesthetic drug was administered at the point of insertion of the middle turbinate so as to block the branches of the anterior ethmoidal nerve.

HR, systolic, diastolic, and mean arterial blood pressures (MAP) were noninvasively recorded before induction of anesthesia (baseline measures) and were monitored every 5 min, but were expressed collectively every 15 min until the end of surgery. Operative field bleeding and subsequently its visibility were graded using a six-point scale: 0 = no bleeding; 1 = slight bleeding not requiring suction evacuation; 2 = slight bleeding requiring occasional suction; 3 = slight bleeding requiring frequent suction evacuation, bleeding threatens surgical field for a few seconds after suction is removed; 4 = moderate bleeding requiring frequent suction evacuation; bleeding threatens surgical field directly after suction is removed; and 5 = severe bleeding and constant suctioning is required, bleeding appears faster than can be removed by suction, and surgical field is severely threatened and surgery is hardly possible or impossible at all [10]. Total amount of bleeding as judged by the amount of blood collected in clean dry suction container and operative times were also recorded.

Infusion of remifentanil or magnesium sulfate and sevoflurane inhalation were stopped just at the end of surgery. Once respiration and response to verbal command were adequate, patients were extubated. The recovery time was estimated in both groups as the time elapsed since stoppage of inhalational anesthetics and infusions until the time the patient achieved a modified Aldrete scoring (MAS) of 11 or more. The degree of sedation was assessed 30 and 120 min after admission to the recovery room using the Brussels Sedation Scale [11]: 1 = sedated and unarousable, 2 = sedated but responds to painful not auditory stimuli, 3 = sedated but responds to auditory stimuli, 4 = awake and calm, and 5 = agitated.

Statistical analysis

Sample power was calculated as described in the study by Kraemer and Theimann [12] using their proposed figure showing that the sample size for 60% power would require an N of 31/group and 80% power would require an N of 51/group. This hypothesis was documented by Murphy and Myors [13]. Considering that excessive bleeding and frequency of severe hypotension are uncommon events with FESS under hypotensive anesthesia, from a standard nomogram, a sample size of 52 patients per group was determined to be sufficient to give the trial 80% power to detect a difference at the 5% significance level [14]. Obtained data were presented as mean ± SD, ranges, numbers, and ratios. Results were analyzed using a paired t-test for within-group variability; the Wilcoxon ranked test was used for unrelated data (Z-test), and the χ2-test paired t-test for numerical and percentage variability between groups. Statistical analysis was conducted using the SPSS (version 15 for Windows, 2006; SPSS Inc., Chicago, Illinois, USA) statistical package. A P value less than 0.05 was considered statistically significant.


The demographic and preoperative clinical data are shown in [Table 1]. There was a nonsignificant (P > 0.05) difference between the studied groups as regards age, sex, and ASA grade.{Table 1}

The baseline hemodynamic measures were comparable and showed no significant difference (P > 0.05) among the two groups. However, both groups showed significantly reduced HR throughout the duration of surgery compared with baseline HR records, with group R showing significantly (P = 0.0001) lower collective HR readings compared with group M ([Figure 1]).{Figure 1}

The mean blood pressure measure estimated throughout the duration of surgery was significantly lower compared with baseline measures. In group R, the mean MAP measure was significantly (P = 0.0007) low compared with group M ([Figure 2]). Remifentanil allowed properly controlled reduction of HR and blood pressure records, reaching its lowest level at T2 and T3 compared with that in group M ([Table 2]).{Figure 2}{Table 2}

Controlled hypotensive anesthesia with remifentanil and magnesium sulfate improved surgical feasibility, with significantly higher frequency of patients showing lower field visibility scale (FVS) score in group R compared with group M (P = 0.023). Moreover, the mean value of total FVS score was significantly (P = 0.0008) lower in group R compared with group M ([Figure 3]).{Figure 3}

The mean amount of collected blood was significantly (P = 0.001) lower in group R compared with group M ([Figure 4]), and the mean operative time was significantly (P = 0.037) shorter in group R compared with group M ([Table 3] and [Figure 5]).{Figure 4}{Figure 5}{Table 3}

Magnesium infusion provided more significantly longer duration of postoperative sedation; at 30-min after discontinuation of infusions 20 patients were sedated but responded to auditory stimuli, and three patients responded to painful but not to auditory stimuli, and at 120 min nine patients were still sedated but responded to auditory stimuli. In contrast, all patients who received remifentanil infusion were awake and calm, with significantly higher difference compared with magnesium sulfate infusion ([Table 4]). Patients who received remifentanil infusion had reached a MAS of 11 or more within 10 min, whereas patients who received magnesium sulfate infusion were delayed and took significantly longer time (P = 0.0003) reaching a MAS of 11 or more.{Table 4}


The present study evaluated the comparison between remifentanil and magnesium sulfate infusion in terms of adequacy and outcome of controlled hypotension anesthesia during FESS. It shows that hypotensive anesthesia using either remifentanil or magnesium sulfate improves surgical feasibility for FESS, wherein no patient showed bleeding that necessitated abandonment of the procedure; only seven (6.7%) patients showed moderate bleeding and 16 patients showed slight bleeding. These data illustrate the beneficial effect of hypotensive anesthesia as a modality to improve the quality of surgical procedure and its outcome and support previously documented studies that stated that controlled hypotension, irrespective of modality used, is effective in providing ideal surgical field during FESS [6],[15],[16].

These data indicated the effect of controlled hypotension for control of bleeding and thus field visibility and operative time. In line with these data, Wormald et al. [17] found MAP and pulse rate to significantly influence the surgical field independently during FESS under controlled hypotensive anesthesia. Sieśkiewicz et al. [18] also found a significant and strong correlation between operative field conditions and MAP and concluded that, with stable low HR at the minimal physiological values, the bleeding in the operative field depends on MAP.

Magnesium sulfate infusion proved to be effective as a hypotensive agent that can be used for provision of controlled hypotension. These data support that previously reported by Elsharnouby and Elsharnouby [19], who, in a placebo-controlled study, tried to assess the effect of perioperatively administered intravenous magnesium sulfate 40 mg/kg intravenous bolus before induction of anesthesia and 15 mg/kg/h through continuous intravenous infusion during the operation as a technique of hypotensive anesthesia during FESS and found that magnesium sulfate led to a reduction in arterial pressure, HR, blood loss, and duration of surgery. Moreover, Cizmeci and Ozkose [20] in a placebo-controlled study documented that 50 mg/kg of magnesium sulfate in 100 ml of saline followed by 8 mg/kg/h infusion can be used safely as an adjuvant to total intervenous anesthesia (TIVA) for septorhinoplasty that can be managed as day-case surgery.

The reported advantages for remifentanil are in agreement with studies that previously reported superior blood pressure control effect of remifentanil-based TIVA compared with balanced anesthesia alone [17],[21] or using adjuvant such as esmolol [15],[22],[23]. Recently, Yun et al. [24] found both nitroprusside and remifentanil to reduce MAP and total peripheral resistance index without a significant change in cardiac index, but HR was higher and stroke volume index was lower with nitroprusside compared with remifentanil.

Kemmochi et al. [25] and Koshika et al. [26] experimentally found that remifentanil, in addition to reduction of systemic blood pressure measures, significantly reduced local rabbit oral tissue blood supply and attributed the lessened blood loss during manipulations to the combined systemic hypotensive effect and to local decrease in blood supply; these findings could explain the reported significantly lower bleeding with remifentanil in the current study.

In a similar comparative study, Ryu et al. [27] compared remifentanil and magnesium sulfate during middle ear surgery and found that controlled hypotension was well maintained and surgical conditions were not different between the two groups, but postoperative MAP and HR were higher with remifentanil compared with magnesium sulfate and attributed this to the extended duration of action of magnesium sulfate and release of sympatholytic effect of remifentanil once infusion was stopped.

In addition, remifentanil provided early recovery with significantly shorter time to achieve a MAS of 11 or more and significantly lower sedation scores on Brussels Sedation Scale. This could be attributed to the sedative effect of magnesium sulfate. In line with this attribution, Ray et al. [28] found that requirements of propofol and fentanyl were significantly less with intravenous clonidine and magnesium sulfate versus control, but recovery was slower with magnesium sulfate compared with clonidine and placebo. Moreover, Khafagy et al. [29] found that patients who received magnesium sulfate showed a significantly lower muscle relaxant consumption, and delayed recovery and postoperative anethesia care unit (PACU) discharge compared with those who received clonidine during bispectral index-guided TIVA.

Limitation of the study

The doses for both drugs used in this study were based on previous studies, and so we can conclude the results only for the selected doses. In other words, if the dose of magnesium sulfate would be increased, may be it would show different results. Another limitation is that this study was conducted on ASA I and II only. Therefore, we do think that further studies may be needed with different doses and on different ASA class.


In this study, controlled hypotensive anesthesia minimized bleeding and provided excellent field visibility during FESS. Remifentanil provided superior outcome manifested as a significant reduction in operative field bleeding, and hence provided better field visibility and shorter operative time compared with magnesium sulfate. In addition, remifentanil provided early recovery without postoperative sedation and hence allowed FESS to be conducted as a day-case surgery.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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