Subarachnoid Block (SAB) or Spinal Anaesthesia (SA) causes Hypotension and Bradycardia due to Sympathetic blockage. It is difficult to predict the height of sensory block. Recent studies have reported that IV Phenylephrine can reduce the rostral spread of SA in pregnant women. So, it is thought that IV phenylephrine infusion can also be helpful in maintaining BP by limiting the rostral spread of SA during elective surgeries in non-obstetric patients.

A Prospective Randomised Experimental Clinical Trial Study. 60 patients , aged 22-55yrs , belonging to ASA grade 1 and 2 , scheduled for elective Urological Surgery under Spinal anaesthesia , were randomised into two groups Group C ( Control group without IV phenylephrine ) n=30 and Group P ( with IV Phenylephrine)n=30 . After an IV bolus of 50 mcg of Phenylephrine following Spinal Anaesthesia , an infusion of phenylephrine @ 200 mcg /hr was started and Dermatomal spread of SA ( Height of Sensory Block) , Hemodynamic Changes and incidences of Hypotension were noted and compared between two groups.

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).

Intravenous phenylephrine can decrease the rostral spread of spinal anesthesia during urologic surgery.