Background: Bleeding during functional endoscopic sinus surgery (FESS) can compromise surgical field quality. Intraoperative controlled hypotension by various hypotensive agents can reduce blood loss and improves surgical field visibility with less need for intraoperative blood transfusions. This study compared the hypotensive effectiveness and safety of dexmedetomidine and magnesium sulfate in patients undergoing elective FESS. Patients and Methods: Sixty adult patients posted for elective FESS were randomly assigned to two groups. Group A received a loading dose of dexmedetomidine 1 μg/kg, followed by infusion of 1 μg/kg/h, and Group B received a loading dose of magnesium sulfate 40 mg/kg, followed by 15 mg/kg/h infusion. Surgical field quality, emergence time, sedation score, Visual Analog Scale score, recovery profile, and vital signs were recorded. Mean arterial pressure (MAP) was kept above 65 mmHg during induced hypotension. Results: Both the groups achieved the target MAP (65–70 mmHg) and improved the surgical field visibility with reduced blood loss. Hemodynamics was superior in the dexmedetomidine group with the additional advantage of postoperative conscious sedation and analgesia (P < 0.05). None of the groups showed any statically significant adverse effects (P > 0.05).Conclusions: Both dexmedetomidine and magnesium sulfate are safe agents for controlled hypotension for improving surgical field quality. Dexmedetomidine provides an additional benefit of reducing the analgesic requirements and providing postoperative sedation.
Keywords: controlled hypotension, dexmedetomidine, functional endoscopic sinus surgery, magnesium sulfate
|How to cite this URL:|
Bafna U, Gurjar SS, Nagal JB. Dexmedetomidine versus magnesium sulfate for induced hypotension during functional endoscopic sinus surgery: A randomized, double-blind study. Bali J Anaesthesiol [Epub ahead of print] [cited 2021 Apr 22]. Available from: https://www.bjoaonline.com/preprintarticle.asp?id=290528
| Introduction|| |
Functional endoscopic sinus surgery(FESS) is a well-established and frequently used therapeutic technique for nasal sinus pathologies. FESS uses a microdebriding device that removes the pathologic tissue while the surgeon preserves the normal mucosa. Sinus mucosa has got very extensive vascular supply, so capillary bleeding becomes a major problem in FESS, which can impair visibility in the surgical field. Poor surgical field visibility compromises the surgeon's pace, increases the duration of surgery, and may lead to perioperative complications.
The controlled hypotension technique is used to reduce blood loss and to improve surgical field visibility employing drug-induced hypotension. Deliberate hypotension was first introduced in 1917 by Harvey Cushing to provide a bloodless field for neurosurgery. In hypotensive anesthesia, mean arterial pressure (MAP) is reduced by 25%–30% from baseline but not lower than 60 mmHg to maintain adequate perfusion to vital organs. Induced hypotension is contraindicated in high-risk patients having cardiovascular disease, neurological compromise, anemia, and autonomic neuropathy.
Various pharmacological agents such as nitroglycerine, sodium nitroprusside alpha-1 blockers, beta-blockers, nicardipine, and magnesium sulfate have been used for induced hypotension. Recently, the use of alpha-2 agonists such as clonidine and dexmedetomidine is increasing. An ideal hypotensive agent should have faster onset, rapid elimination, nontoxic metabolites, and predictable effect. Physiological response to blood loss may be lost during hypotensive anesthesia. Therefore, blood loss should be carefully estimated.
Dexmedetomidine acts on central α2A and imidazoline-1 receptors, which results in decreased norepinephrine release. This decreased sympathetic outflow leads to decreased blood pressure and heart rate (HR). Magnesium sulfate stabilizes the cell membrane and intracytoplasmic organelles by mediating the activation of Na+-K+-ATPase and Ca++-ATPase enzymes, which play a role in transmembrane ion exchange during the depolarization and repolarization phases. This study was aimed to compare the effectiveness and safety of dexmedetomidine and magnesium sulfate as hypotensive agents in elective FESS.
| Patients and Methods|| |
This is a double-blind, randomized, interventional study conducted in the Department of Anesthesia of SMS Medical College, Jaipur (India). We obtained the approval of the Institutional Ethics Committee and registered it in the Clinical Trials Registry-India with registration number CTRI/2019/11/021910. All patients provided written informed consent to be included in the study.
We employed a simple random technique through a sealed envelope method. For proper double blinding, drug preparation was carried by one anesthetist and administered by a different one. We included 60 patients of either sex, American Society of Anesthesiologists (ASA) physical status I–II, 18–50 years, and weighing 45–65 kg who were scheduled for elective FESS (surgery duration about 60–90 min). Patients with a history of hypertension, coronary arterial disease, renal dysfunction, hepatic dysfunction, cerebral insufficiency, coagulation abnormalities, recurrent sinus surgery, rhinorrhea, and allergy to study drugs were excluded from the study.
They were randomly divided into two groups. Group A received dexmedetomidine 1 μg/kg in 10 ml of saline over 10 min, followed by 1 μg/kg/h infusion. Group B received magnesium sulfate 40 mg/kg in 10 ml of saline over 10 min, followed by 15 mg/kg/h infusion. All other treatments were similar within the two groups.
Intraoperative vital parameters (HR, systolic blood pressure (SBP), diastolic blood pressure, MAP, and oxygen saturation) were recorded at baseline, after the loading dose, after induction, 1 min after intubation, 5 min after intubation, and thereafter every 10 min. The patients were supplemented with an additional dose of fentanyl 1 mcg/kg when the HR increases by more than 20%. The surgical site was observed on the endoscopy display for the severity of bleeding and the need for frequent suctioning. We used the average category score proposed by Fromme and Boezaart to measure this parameter.
At the end of the surgery, the patient was reversed with neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg. We extubated the patients on a fully awake state with adequate breathing. The postoperative sedation was assessed using the Ramsay Sedation Scale. Emergence time in this study was defined as the time from cessation of anesthetic delivery until the patient responds to verbal command by eye opening. Incidence of adverse effects such as nausea, vomiting, shivering, dryness of mouth, hypotension, and bradycardia was also recorded.
We employed the Visual Analog Scale (VAS) to assess postoperative pain severity that was assessed every 15 min postoperatively. Whenever the VAS score is ≥3, the patients were allowed to receive rescue analgesia (Diclofenac Sodium 75 mg). The time to the first administration of rescue analgesia was also recorded.
Statistical analysis was performed with the Statistical Package for the Social Sciences software version 21 (SPSS Inc., Chicago, IL, USA). We used the Student's t-test to evaluate the significance of normally distributed variables, whereas the Mann–Whitney test was used otherwise. P <0.05 was considered statistically significant.
| Results|| |
Sixty patients were enrolled and completed the study. Demographic data such as age, sex and weight distribution, ASA physical status, type of surgery, and duration of surgery were statistically comparable (P > 0.05) in both the groups [Table 1]. Both HR and MAP were significantly decreased (P < 0.05) at all observation time points after giving a loading dose of study drugs in comparison to baseline [Table 2] and [Table 3].
The quality of surgical field visibility was assessed using the average category score at every 10-min interval. A lower score means better visibility. Group A ranges from score 1 to 3, and Group B ranges from score 2 to 3 [Figure 1]. There was no statistically significant difference between the two groups in terms of mean estimated blood loss. The mean estimated blood loss in Group A and Group B was 128.33 ± 6.61 and 130.00 ± 7.19 ml, respectively (P > 0.05).
The mean emergence time was significantly longer in Group A (7.22 ± 0.52 min vs. 6.28 ± 0.70 min, P < 0.001). Sedation lasted longer in the dexmedetomidine group compared to the magnesium sulfate group. Mean sedation scores were higher in Group A at all the time intervals up to 120 min postoperatively (P < 0.001), as displayed in [Figure 2].
Postoperative pain was scaled by VAS score every 15 min until the patient reaches a VAS score of 3, and then, rescue analgesia was given. Time for the need of first rescue analgesia was noted and found significantly longer in Group A (110.00 ± 12.82 vs. 82.89 ± 10.77 min, P < 0.001). Dexmedetomidine showed a good postoperative analgesic effect, which lasted longer than magnesium sulfate. The mean VAS score was lower at every time interval in Group A [Figure 3].
The incidence of nausea, vomiting, shivering, dry mouth, hypotension, and bradycardia was statistically comparable between the two groups (P > 0.05). The most frequent side effect with dexmedetomidine was dry mouth and mild nausea. None of the patients had severe adverse effects [Table 4].
| Discussion|| |
A clearly visible surgical field is always desired by a surgeon. A blood-filled field can drastically reduce the efficacy of an endoscopic surgeon. FESS is an endoscopic surgery that requires proper surgical field visibility. Sinus mucosa has an abundant blood supply and bleeds occurring from its capillaries while doing FESS is a troublesome situation. An important technique to reduce bleeding during the surgery is controlled hypotension to such a level so that bleeding is minimal, but perfusion to vital organs is maintained.
Dexmedetomidine is a more selective α2-adrenoreceptor agonist (α2/α1 = 1620/1. Dexmedetomidine induces sedation by decreasing the activity of noradrenergic neurons in the locus ceruleus in the brain stem, thereby increasing the activity of inhibitory gamma-aminobutyric acid neurons in the ventrolateral preoptic nucleus. Magnesium sulfate limits the outflow of calcium from the sarcoplasmic reticulum and produces a vasodilating effect by increasing the synthesis of prostacyclin and inhibiting angiotensin-converting enzyme activity. Furthermore, Mg++ inhibits the release of norepinephrine by blocking the N-type Ca++ channels at nerve endings and thus decreases the blood pressure.
In this double-blind, randomized interventional study, both the groups were statistically comparable in terms of demographic data, surgical duration and technique, baseline vitals, and preoperative awake status. Both dexmedetomidine and magnesium sulfate drugs achieved the desired target of MAP 65–70 mmHg. After induction of anesthesia, HR and MAP were more effectively reduced by dexmedetomidine.
Magnesium stabilizes the excitable myocardium, slowing the rate of sinoatrial node and prolonging the rate of conduction by controlling the movement of calcium, sodium, and potassium ions across the cell membrane. Khalifa and Awad compared 60 patients between dexmedetomidine, magnesium sulfate, and glyceryl trinitrate and observed a slower and steady HR in the dexmedetomidine group.
Bayram et al. also compared dexmedetomidine and magnesium sulfate in 60 patients and found that there was a significant difference between the groups after induction of anesthesia until extubation, with lower values of MAP in the dexmedetomidine group. Our findings are consistent with a similar study done by Soliman and Fouad in endoscopic transnasal transsphenoidal resection of pituitary adenoma and found that SBP, BBP, and MAP were lower with the dexmedetomidine group as compared to the magnesium sulfate group.
Average category score, proposed by Fromme and Boezaart, was used in our study. As explained earlier, it is a five-point scoring system to assess the severity of bleeding and observing the frequency of suction. We found that dexmedetomidine and magnesium sulfate both provided a good and comparable surgical field visibility, with an average category score of 1–3 and 2–3, respectively. These results are also supported by a similar study done by Bayram et al. who reported an average category score between 1 and 2 in the dexmedetomidine group and between 2 and 3 in the magnesium sulfate group.
Rokhtabnak et al. found an average bleeding category score between 1 and 2 in the dexmedetomidine group and between 2 and 3 in the magnesium sulfate group in their study. None of the patients presented with excessive blood loss. We did not find any statistical difference between both the drugs in terms of intraoperative blood loss.
Emergence time was slightly prolonged by dexmedetomidine. Dexmedetomidine has a unique property of providing conscious sedation. It induces sleep by activating endogenous nonrapid eye movement sleep-promoting pathways. The highest densities of α2-receptors have been detected in the locus ceruleus, and the hypnotic and sedative effects of α2-adrenoceptor activation have been attributed to this site in the central nervous system. Dexmedetomidine produced calmness and very good analgesia postoperatively. The time to first analgesic request was significantly longer in the dexmedetomidine group.
Rokhtabnak et al. found that dexmedetomidine administration decreased the opioid requirements to a greater extent than magnesium sulfate, and dexmedetomidine has stronger analgesic effects than magnesium sulfate. The analgesic effects of dexmedetomidine can be due to the activation of α2B-adrenoceptors at the level of the dorsal horn of the spinal cord and the inhibition of substance P release. The antagonist effect of magnesium at N-methyl-d-aspartate receptors is an explanatory reason for some analgesic property of magnesium sulfate. Similarly, Soliman and Fouad studied the effect of dexmedetomidine and magnesium sulfate in endoscopic transnasal transsphenoidal resection of pituitary adenoma and found that dexmedetomidine provides excellent postoperative analgesia. None of our patients had any severe side effects or any other complication except mild dryness in the dexmedetomidine group.
This study has some limitations. We did not use a control group because it is unethical if we do not control bleeding in such procedures where even small amounts of bleeding can restrict surgical visibility. Postoperative magnesium sulfate and calcium levels were not measured, which can be considered as one limitation of the study. However, the amount of magnesium sulfate administered in this study was approximately half of the dose for the usual treatment of preeclampsia, and no patient exhibited clinical signs of profound neuromuscular blockade.
| Conclusions|| |
Dexmedetomidine and magnesium sulfate both achieved controlled hypotension and provided a good comparable surgical field during FESS. Dexmedetomidine was superior compared to magnesium sulfate in terms of hemodynamic stability, longer duration postoperative analgesia, and good postoperative sedation level.
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Conflicts of interest
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Jahnu Bhoj Nagal,
D7, Meera Marg, Bani Park, Jaipur - 302 016, Rajasthan
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]