The effect of the intravenous phenylephrine on the level of spinal anesthesia

BACKGROUND Spinal anesthesia causes hypotension and bradycardia due to sympathetic nerve block and it is difficult to predict the level of sensory block and the duration of blockade. Recent studies have reported that intravenous phenylephrine can reduce the rostral spread of spinal anesthesia in pregnant women. We think a phenylephrine infusion will be useful for maintaining the baseline blood pressure by reducing the rostral spread of spinal anesthesia during the elective surgery of non-obstetric patients. METHODS SIXTY PATIENTS WHO WERE UNDERGOING UROLOGIC SURGERY WERE RANDOMIZED INTO TWO GROUPS: Group C (the control group without phenylephrine) and Group P (with the addition of phenylephrine). After a bolus infusion of 50 µg phenylephrine following the spinal injection, phenylephrine was continuously infused at the rate of 200 µg/hr. We compared the dermatomal spreads of spinal anesthesia, the hemodynamic parameters (blood pressure, heart rate) and the incidences of hypotension between the two groups. RESULTS At 20 minutes, the level of the upper dermatome blocked against cold sensation was a median of T8 (interquartile range: T8-T10) for the phenylephrine group, as compared with T4 (interquartile range: T4-T6) for the control group (P < 0.001). CONCLUSIONS Intravenous phenylephrine can decrease the rostral spread of spinal anesthesia during urologic surgery.