Hypotension and bradycardia are commonly observed after the spinal anesthesia and various mechanisms have been postulated for these hemodynamic changes.
A middle-aged otherwise healthy male Caucasian patient developed several episodes of bradycardia postoperatively after the umbilical hernia repair under subarachnoid block (SAB) while trying to lean forward and move his legs. Episodes were aborted when patient was advised to relax in supine position.
The common mechanism of bradycardia and hypotension under SAB is postulated as sympathetic blockade, decrease venous return, and parasympathetic over-dominance leading to a decrease in right arterial pressure and pressure in the great veins as they enter the right atrium. But over time, the parasympathetic inhibition is usually withdrawn first, leading to the risk of severe bradycardia that is probably favored by the reverse Trendelenburg position as described in our case.
Postoperative severe hemodynamic changes can occur even under stable spinal anesthesia; however, can be prevented by vigilant monitoring and simple maneuver which includes maintenance of relax posture on the bed.