Effect of Phenylephrine versus Mephentermine Treatment on Frontal Lobe Oxygenation during Correction of Hypotension in Supratentorial Cerebral Tumor Patients under General Anesthesia: A Randomized Controlled Study

Background: To evaluate the changes in cerebral oxygenation (ScO2) as measured by near-infrared spectroscopy (NIRS) between bolus doses of phenylephrine and mephentermine when used to treat hypotension in patients undergoing supratentorial tumor surgery under general anesthesia.

Materials and Methods: This was a randomized controlled study including 80 ASA-1 and -2 patients between 18 and 65 years scheduled for supratentorial tumor surgery. Patients were anesthetized with propofol (1.5–2 mg/kg) and fentanyl (1.5–2 µg/kg); and were randomized after hypotension during anesthesia induction to receive bolus dose of either phenylephrine (100 µg) or mephentermine (6 mg). Ipsilateral and contralateral ScO2 using NIRS, cardiac output using NICOM, mean arterial pressure, systemic vascular resistance, and heart rate were recorded at hypotension, at drug administration and every minute for a total duration of 10 minutes after achieving desired MAP level with study drug.

Results: Both ipsilateral and contralateral ScO2 decreased significantly in phenylephrine group after drug administration at all 10-minute time points as compared with hypotension time point (<0.001). While in mephentermine group, ipsilateral and contralateral ScO2 increased significantly at all time points (<0.001). On intergroup comparison, difference of cerebral oxygenation value between two groups was significant at all time points after hypotension for both ipsilateral and contralateral ScO2 (p < 0.001). CO decreased significantly in phenylephrine group (<0.001), while increased significantly in mephentermine group at time points of 3 to 10 minutes (<0.001). Cardiac output had statistically significant effect on ScO2 (p = 0.005).

Conclusions: Associated with changes in cardiac output, ScO2 decreased after phenylephrine treatment while increased after mephentermine treatment.

Publication History

Article published online:
25 March 2020