Dexmedetomidine Versus Nitroglycerin on Surgical Field Quality and Drug Cost in Functional Endoscopic Sinus Surgeries

Impact of Dexmedetomidine Versus Nitroglycerin on Surgical Field Quality and Drug Cost in Functional Endoscopic Sinus Surgeries

Sinus surgery is one of the most prevalent ear, nose, and throat (ENT) surgeries, which is mainly carried out nowadays through functional endoscopic sinus surgery (FESS) and leads to significant improvement in the clinical symptoms of patients with rhinosinusitis. It is necessary to maintain safe conditions for this surgery, and the major problem reported during FESS under general anesthesia (GA) is impaired visibility due to excessive amount of bleeding. This is particularly important for the successful surgery of the ethmoid and sphenoid sinuses because even minimum amount of bleeding might seriously impair the successful completion of the surgery, increase the operational risk, and increase surgery time which are major concerns for both anesthesiologist and ENT specialist.

Controlled hypotension is the commonly used technique to limit blood loss and improve visualization in the surgical field during FESS, various techniques have been adopted to achieve controlled hypotension, one of them is the use of pharmacological drugs in the form of volatile anesthetics, direct-acting vasodilators, autonomic ganglion-blockers, and α-adrenergic receptor blockers.

Alpha-2 (α-2) receptors are found in the peripheral and central nervous systems, platelets and many other organs including the liver, pancreas, kidney, and eye. Stimulation of the receptors in the brain and spinal cord inhibits neuronal firing causing hypotension, bradycardia, sedation, and analgesia. Alpha-2 (α-2) agonist drugs have sympatholytic, sedative, anesthetic, and analgesic sparing effects, as well as vasoconstrictive effects and thereby reduce intraoperative bleeding. Also, the use of α-2 agonists in the perioperative period has been associated with reduced anesthetic requirements, decreased heart rate and blood pressure.

Dexmedetomidine is a highly selective α-2 adrenergic receptor agonist (selectivity ratio for α2: α1 is 1600:1). The sympatholytic effect of dexmedetomidine made it attractive to be used as a hypotensive drug during surgery because of decreasing heart rate (HR) and cardiac output (CO) without decreasing stroke volume unless the plasma concentrates reaches above 5.1 μg/mL. The cardiovascular effects of dexmedetomidine begin with initial hypertension following the administration of a loading dose, due to the activation of α 2B receptors located on vascular smooth muscle, with subsequent hypotension and bradycardia due to centrally mediated decrease in sympathetic tone. Dexmedetomidine also has sedative, amnesic, anxiolytic, hypnotic, and analgesic effects with minimal changes in respiratory variables. Furthermore, it reduces postoperative nausea, vomiting, and shivering. It also reduces delirium in patients after cardiac surgery.

Nitroglycerin is a directly acting vasodilator drug frequently used to produce controlled hypotension because it is easily titratable and having very rapid onset as well as rapid offset of action. However, the disadvantages of nitroglycerin are reflex tachycardia and venous congestion which leads to increased blood loss.

Aim of the work was improving surgical field quality and drug cost in patients undergoing Functional Endoscopic Sinus Surgeries by comparing between dexmedetomidine and nitroglycerin.

This study had been carried out in Anesthesia, Intensive Care and Pain management Department - Faculty of Medicine - Zagazig University Hospitals.

Sample size:

Assuming the average category scale was 73.33% vs 36.67% in group D vs group N, so the sample was 66 adult male and female undergoing FESS , 33 cases in each group (dexmedetomidine and nitroglycerin) using open EPI info with CI 95%, Power of test 80%.

Withdrawal criteria:

The patient has the right to withdraw from the study at any time without any negative consequences or harm on his/her medical treatment plan.

Randomization:

All Patients were randomly allocated into 2 equal groups. Patients were randomized using computer generated randomization table in a 1:1 ratio and allocated either in dexmedetomidine group (group D) or nitroglycerin group (group N).

Randomization assignments were kept in sealed envelopes until the day of surgery, and then they opened by the research anesthesiologist immediately prior to the operation.

Process:

• All participating patients were interviewed preoperatively during their preoperative preparation. The goal and endpoints of the study were discussed. Understanding of the technique was reviewed and emphasized.
• History was taken, clinical examination was done, and informed written consent was obtained.
• Fasting before the operation (8 hours for solid meal and 2 hours for clear fluids).
• IV line was inserted; midazolam (0.02-0.05 mg/kg) was given as a premedication, started IV fluids as ringer lactate (8-10 ml/kg).
• 10 minutes before induction of anesthesia, full monitoring including noninvasive arterial blood pressure, electrocardiogram, pulse oximetry, and capnogram (after induction of anesthesia) were applied and basal readings were recorded.
• Preoxygenation with 100% oxygen for 3 minutes before induction.

Group (D):

Started infusion of a loading dose of dexmedetomidine 1 μg /kg over 10 minutes before induction of anesthesia.

Induction:

• Fentanyl IV (2 μg/kg), Propofol IV (2 mg/kg), and Rocuronium IV (1mg/kg).

Maintenance:

• Maintenance of anesthesia was done with isoflurane inhalation at 1-2 minimum alveolar concentration (MAC) and incremental doses of rocuronium 0.5mg/kg every 45 minutes.
• IV infusion of dexmedetomidine 0.3-0.7 µg/kg/h. Group (N)

Induction:

• Fentanyl IV (2 μg/kg), Propofol IV (2 mg/kg), and Rocuronium IV (1 mg/kg).

Maintenance:

• Maintenance of anesthesia was done with isoflurane inhalation at 1-2 (MAC) and incremental doses of rocuronium 0.5 mg/kg every 45 minutes.
• IV infusion of nitroglycerin at a dose of 0.5-2 µg/kg/min. Both drugs (dexmedetomidine and nitroglycerin) were titrated till mean arterial pressure (MAP) 60-70 mmHg, or a MAP below 30% of baseline.

Operations for both groups were carried out by the same surgical team. All the patients, surgeons, and the attending anesthetist who was assigned to record the patients' parameters were blinded to the infused drugs. The randomization envelopes, the syringe pumps, and their code labels were prepared by an anesthetist independent in the study.

Recovery period:

Patients were recovered with neostigmine (0.05-0.08 mg/kg) and atropine, the standard analgesia (paracetamol) was started at a dose of (15 mg/kg) then patients were transferred to the post anesthesia care unit (PACU) for observation.

Measurements:

• The visibility of the surgical field was assessed by surgeon using Fromme and Boezaart scoring system:-

Fromme and Boezaart scoring system:

Grade Assessment 0 No bleeding (cadaveric conditions) I Slight bleeding, no suctioning required II Slight bleeding, occasional suctioning required III Slight bleeding, frequent suctioning required; bleeding threatens surgical field a few seconds after suction is removed IV Moderate bleeding, frequent suctioning required, and bleeding threatens surgical field directly after suction is removed V Severe bleeding, constant suctioning required; bleeding appears faster than can be removed by suction; surgical field severely threatened and surgery usually not possible Heart rate and MAP basal readings were recorded then at 15 minutes time interval intraoperative.

Emergence time defined as the interval between discontinuation of the anesthetics to response of eye opening to the verbal command.

Recovery time defined as the time from end of surgery (i.e., final wound covered) until the patient left for the hospital ward were recorded.

The postoperative sedation was assessed with Ramsay Sedation Score Observation for any side effects or complications such as nausea, vomiting, shivering, dry mouth, bradycardia, tachycardia, and hypotension.

The cost of both drugs was recorded.

Data collection:

• Patient characteristics: age, sex, BMI, and physical status of patients included in the study.
• MAP, heart rate and assessment score of surgical field intraoperative.
• Emergence and recovery time.
• Sedation score.
• Drug cost.
• Side effects or complications.

Inclusion Criteria:

• Physical status: American Society of Anesthesiologists (ASA) I & II.
• Body Mass Index (BMI): 18.5-30 kg/m2.
• Type of operation: elective bilateral FESS.
• Type of anesthesia: general anesthesia.

Exclusion Criteria:

• Patients with known history of allergy to study drugs.
• Anticipated difficult intubation.
• Advanced hepatic, renal or cardiovascular diseases.
• Central nervous system disorder, metabolic disease, and electrolyte imbalance.
• Coagulopathies or taking drugs affecting coagulation.