European Journal of Cardiovascular Medicine

Functional Endoscopic Sinus Surgery (FESS), a minimally invasive procedure restores sinus ventilation and normal function.¹ However serious complications from profuse bleeding that impair surgical visibility have been documented for FESS under general anaesthesia.² Additionally, there may be peri-operative complications related with this technique such as meningitis, orbital cellulitis, nerve damage etc all of which will increase risk of bleeding during surgery.³

FESS requires bloodless surgical field for proper visualization. Controlled hypotension for FESS has advantages such as less blood loss and enhanced surgical field quality.Intentional lowering of blood pressure, referred to as Controlled hypotension or Hypotensive anaesthesia, should be achieved in accordance with the patient’s baseline blood pressure rather than a predetermined target pressure. It is therapeutically acceptable to lower the mean arterial blood pressure (MAP) by 30% below baseline MAP with a minimum MAP of 60-70mmHg.⁴

Various agents like Magnesium sulfate,⁵ vasodilators (Sodium nitroprusside,⁶ Nitroglycerine,⁷ Hydralazine), high doses of potent inhaled anaesthetics⁸ (Isoflurane, Sevoflurane), intravenous anaesthetics like Propofol,⁹ Adenosine¹⁰ and α-adrenergic agonists like Clonidine,¹¹ Dexmedetomidine¹² and β-adrenergic antagonists like Esmolol¹³ etc have been used to produce controlled hypotension.

Esmolol is an ultra-short acting β-adrenergic antagonist that reduces heart rate and blood pressure.¹⁴ Dexmedetomidine is a highly selective α2 adreno-receptor agonist which acts as a sympatholytic, anxiolytic, sedative, analgesic, anti-inflammatory and causes minimal respiratory depression.¹²

The purpose of this study was to compare Esmolol with Dexmedetomidine to accomplish a favourable surgical field for Functional endoscopic sinus surgery.

Source of Data

40 adults undergoing elective FESS surgery under General anaesthesia at BGS Global Institute of Medical Sciences and Hospital, Bangalore.

Study Design
A randomized, double blinded, prospective, comparative 2 group clinical study.

Sample Size
Based on survey of previous literature for an outcome variable on Mean arterial Pressure (MAP) at 70min assessment and monitoring in a prospective comparative study with minimum difference of 3mmHg and common S.D of 3.12mmHg to attain significance at Type I error(α error) of atleast 5%, Type II error (β error) at 10% and keeping statistical power above 90%, forty is a suitable sample size (20 in each group) for two-group randomized clinical trial after adjusting for lost-to follow up, dropout rates and withdrawal.

Inclusion Criteria

• Patients ready to give informed, written consent.
• Patients planned for an elective FESS operation under general anaesthesia and ranging in age from 18 to 60.
• American Society of Anaesthesiologists (ASA) physical status I and II patients.

Exclusion Criteria

• Patients who belong to ASA physical status III & above.
• Patients who have known hypersensitivity to study drugs.
• Patients who are known case of IHD, Bronchial Asthma, uncontrolled hypertension, on Beta blockers, Pregnant & lactating mothers.

Randomisation & Blinding

Patients were randomly allocated into 2 groups using a systemic random sampling technique.

Group D: Dexmedetomidine 0.5mcg/kg was diluted in Normal Saline to 60ml taken in 60ml syringe.

Group E: Esmolol 0.75mg/kg was diluted in Normal Saline to 60ml taken in a 60ml syringe.

Patients were blinded and an anaesthesiologist who was not participating in the study prepared the trial medications (colourless, equivolume), thus the study was double-blinded.

The study comprised of 40 adult patients who met the inclusion criteria and were prepared to give informed, written consent. Pre-anaesthetic evaluation including detailed history, physical examination, routine & indicated laboratory investigations were conducted prior to the enrolment of the patient for the study and standard NPO guidelines were followed.

On the day of surgery, 18G intravenous access secured and premedication Inj. Pantoprazole 40mg given as slow intravenous injection. Inside the operating room, standard monitors were connected to patients. Baseline values of Systolic & Diastolic blood pressure (SBP & DBP), Mean arterial pressure (MAP), Heart rate (HR) and oxygen saturation (SPO2) were recorded.

Patients were randomly allocated into 2 groups (Group D & Group E) each of 20 using a systemic random sampling technique.

Group D: Dexmedetomidine 0.5mcg/kg was diluted in Normal Saline to 60ml taken in 60ml syringe.

Group E: Esmolol 0.75mg/kg was diluted in Normal Saline to 60ml taken in a 60ml syringe.

The infusion was started 10 minutes before induction of General Anaesthesia at the rate of 1ml/min.

All the patients received Inj.Glycopyrrolate 0.005mg/kg, Inj.Midazolam 0.05mg/kg, Inj.Fentanyl 0.002mg/kg and Inj.Propofol 2mg/kg with muscle relaxant Inj. Vecuronium 0.1mg/kg for general anaesthesia to ensure smooth laryngoscopy and intubation as per our institutional protocol.

For Endotracheal intubation, a sterile single lumen cuffed polyvinyl chloride (PVC) endotracheal tube with a size of 7mm or 7.5mm for females and 8mm or 8.5mm for males were used with Macintosh blade (size 3 or 4). After intubation, the cuff was filled with room air and endotracheal tube was fixed.

Intra-operatively Oxygen, Nitrous oxide, Isoflurane at 1 MAC (minimum alveolar concentration) and muscle relaxation by intravenous Vecuronium 0.01mg/kg in regular bolus doses were used to maintain anaesthesia.

During the infusion, systolic, diastolic, mean arterial blood pressure and heart rate were monitored and Average Category Score (Table 1), a 6 point scale was utilized to gauge the degree of bleeding in the surgical field.

The best surgical conditions were characterised as scores less than or equal to 2.

Heart rate was continuously monitored and blood pressure was checked at every two minutes. The infusion was halted for two minutes (until the next blood pressure reading) if the MAP dropped to less than 60mmHg.

If MAP exceeded 75mmHg, a 0.4mg/kg Propofol bolus was administered and the amount of Propofol utilized and the halt time was recorded. All necessary safety precautions were followed.

Samples are age matched with P=0.900, student t test

P=0.057+, Significant, Chi-Square Test

Patients of the study groups were comparable with respect to demographic data, age (Table 2, Graph 1) & gender (Table 3, Graph 2 &3).

The mean SBP (Systolic blood pressure) (Graph 4) and DBP (Diastolic blood pressure) (Graph 5) in group D were lower than those in group E. They were statistically significant lesser values in group D at all time intervals after 20mins of starting the drug infusion as compared to group E (Table 4 & 5).

At almost all intraoperative intervals it is seen that group D’s mean Heart rate (HR) (Graph 7 & Table 7) and mean arterial pressure (MAP) (Graph 6 & Table 6) were lower than group E’s and they were statistically significant at time intervals after 20mins after the start of drug infusion.

In both groups, the average category score (ACS) for the surgical field remained low (Table 8 & Graph 8). The scores were <= 2 through the hypotensive period (Table 9).

In both groups, there were no significant adverse effects noted. During the course of the trial, no patient had resistant hypotension or hypertension or severe bradycardia.

Dexmedetomidine inhibits central sympathetic outflow and activates pre-synaptic alpha-2 adrenoceptors, which in turn reduces norepinephrine production, thus bringing about reduction in blood pressure.^{15, 16} Its strong sedative and analgesic effects combined with an insignificant respiratory depressive effect provides a significant advantage.¹⁷ Dexmedetomidine acts in the locus coeruleus and dorsal horn of the spinal cord to provide sedative and analgesic sparing actions, respectively.¹⁸ As beta-adrenergic antagonists have negative chronotropic and inotropic effects, Esmolol lowers mean arterial pressure (MAP) by reducing cardiac output.^{6, 19}
The mean heart rate (HR) was found to be considerably lower in the Dexmedetomidine group relative to the Esmolol group in a study conducted by Bajwa et al. In the present study there is similar significant lower mean heart rate (HR) and mean arterial pressure (MAP) in Dexmedetomidine group after 20min time interval than Esmolol group.²⁰

When comparing the effects of Esmolol vs. Dexmedetomidine during hypotensive period after induction, Tarek Shams et al found no significant intergroup variations in heart rate (HR) or mean arterial pressure (MAP). In our study, even though both infusions lowered mean arterial pressure (MAP) and heart rate (HR), after 20min interval of start of drug infusion Dexmedetomidine showed even significantly lower values as compared to Esmolol.¹³

Sham T et al examined the effectiveness of Dedmedetomidine and Esmolol for controlled hypotension in their trial of forty patients who were scheduled for FESS. They found that the median score range of average category scale (ACS) for both groups were 2. In our investigation, both medications improved surgical conditions which was similar.¹³

Dexmedetomidine might affect the pharmacokinetics of neuromuscular blocking agents and thus prolong the duration of neuromuscular blockade.^{21, 22} Dexmedetomidine also reduces opioid requirement intraoperatively and stress response to surgery with stable haemodynamic state.^{23, 24} When it is infused intraoperatively, the need for perioperative analgesics is greatly decreased.^{13, 18}

• Dexmedetomidine and Esmolol both are proven to be safe to use in FESS (Functional Endoscopic Sinus Surgery) for hypotensive anesthesia & both were effective in providing ideal surgical field.
• Dexmedetomidine provided better haemodynamic stability, offered an added advantage of reducing the requirements of analgesics and muscle relaxants intraoperatively and also lesser cost as compared to Esmolol.

Conflict of Interest

No conflict of interest.

Ethical approval

The study was approved by institutional ethics committee

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• Stankiewicz JA. Complication of Endoscopic intranasal Ethmoidectomy. Laryngoscope 1987;97:1270-3.
• Maniglia AJ. Fatal and other major complications of endoscopic sinus surgery. Laryngoscope 1991;101:349-54.
• Rodrigo C. Induced hypotension during anaesthesia with special reference to orthognathic surgery. Anaesth Prog 1995;42:41-58.
• Elsharnouby NM, El Sharnouby MM. Magnesium sulphate as a technique of hypotensive anesthesia. Br J Anaesth 2006;96:727-31.