Norepinephrine reduces arterial compliance less than phenylephrine when treating general anesthesia-induced arterial hypotension.

INTRODUCTION: During general anesthesia, arterial hypotension is frequent and may be an important contributor to perioperative morbidity. We assessed the effect of a 5 µg bolus of Norepinephrine (NA) when compared with 50 µg bolus of Phenylephrine (PE) administered to treat hypotension during maintenance anesthesia, on MAP, derived cardiac output and arterial stiffness parameters. METHODS: Patients scheduled for a neurosurgical procedure under general anesthesia were prospectively included. Monitoring included invasive blood pressure, esophageal Doppler, and arterial tonometer used to estimate central aortic pressure with arterial stiffness parameters, such as augmentation index (Aix). After initial resuscitation, hypotensive episodes were corrected by a bolus administration of NA or PE in a peripheral venous line. RESULTS: There were 269 bolus administrations of vasopressors (149 NA, 120 PE) in 47 patients with no adverse effects detected. A decrease in stroke volume (SV) was observed with PE compared with NA (-18 ± 9% vs. -14 ± 7%, P < 0.001). This decrease was associated with an increase in Aix, which was greater for PE than for NA (+10 ± 8% vs. +6 ± 6%, P < 0.0001), and a decrease in total arterial compliance greater for PE compared to NA (Ctot = SV/Central Pulse Pressure) (-35 ± 9% vs. -29 ± 10%, P < 0.001). DISCUSSION: This study suggests that 5 µg of NA administered as a bolus in a peripheral venous line could treat general anesthesia-induced arterial hypotension with a smaller decrease in SV and arterial compliance when compared to PE.