Anesthetic technique
hypotensive, hypotension
HYPOTENSIVE, MUSCLE RELAXATION
At the operating room, standard patient monitoring was established (electrocardiography, pulse oximetry, end-tidal carbon dioxide (ET CO2 ), and noninvasive arterial blood pressure monitoring). Two intravenous cannulas were placed; 18 and 20 gauge.Induction of anesthesia was done by injecting 2 mg/kg propofol, 2 µg/kg fentanyl & 0.5 mg/kg atracurium. The patients were ventilated via face mask with 100% oxygen at a rate of 6 L/min and isoflurane 1.2%. After few minutes, the patients were intubated using a cuffed oral tube. Maintenance of anesthesia was done using isoflurane 1.2% in a mixture of 70% oxygen and 30% air. Muscle relaxation was continued with atracurium 0.1 mg/kg every 20 min. All patients were mechanically ventilated to maintain ET CO2 between 35 and 40 mmHg. An intra-arterial canula was inserted in the radial artery for invasive arterial blood pressure monitoring.The patients were randomly allocated to one of the two groups; either Phentolamine or Nitroglycerine groups. In Phentolamine group (40 patients), the patients received deliberate hypotensive anesthesia with phentolamine infusion via syringe pump by adding 20 mg (2ml) of Phentolamine to 48 ml of normal saline, making it to a final concentration of 0.4 mg/ml at the rate of 0.1-2 mg/min according to the patients desired target blood pressure. In Nitroglycerine group (40 patients), the patients received deliberate hypotensive anesthesia with nitroglycerine infusion via syringe pump by adding 10 mg (10ml) of Nitroglycerin to 40ml of normal saline, making it to a final concentration of 200 µg/ml at the rate of 0.5–10 µg/kg/min according to the patients desired target blood pressure.MAP was gradually reduced in both groups to maintain a target MAP of 60–70 mmHg and systolic blood pressure ≥ 85 mmHg. Patients who developed hypotension (MAP less than 55 mmHg) were managed by discontinuation of the hypotensive drug and administration of intravenous fluid. Ephedrine (10 mg) was given IV when the MAP did not improve, and these patients were excluded from the study.Infusion of the hypotensive agent was stopped 10 min before the anticipated end of surgery. Any residual neuromuscular block was antagonized with neostigmine 0.04 mg/kg and atropine 0.02 mg/kg IV. The patients were extubated after fulfilling the criteria of recovery and transferred to the recovery room.