EPIDURAL BLOOD-FLOW DURING PROSTAGLANDIN-E(1) OR TRIMETHAPHAN INDUCEDHYPOTENSION

To evaluate the effect of prostaglandin E1 (PGE1) or trimethaphan (TMP ) induced hypotension on epidural blood flow (EBF) during spinal surge ry, EBF was measured using the heat clearance method in 30 patients wh o underwent postero-lateral interbody fusion under isoflurane anaesthe sia. An initial dose of 0.1 mug.kg-1.min-1 of PGE1 (15 patients), or 1 0 mug.kg-1.min-1 of TMP (15 patients) was administered intravenously a fter the dural opening and the dose was adjusted to maintain the mean arterial blood pressure (MAP) at about 60 mmHg. The hypotensive drug w as discontinued at the completion of the operative procedure. After st arting PGE1 or TMP, MAP and rate pressure product (RPP) decreased sign ificantly compared with preinfusion values (P < 0.01), and the degree of hypotension due to PGE1 remained constant until 60 min after its di scontinuation. Heart rate (HR) did not change in either group. EBF did not change during PGE1 infusion whereas in the TMP group, EBF decreas ed significantly at 30 min and 60 min after the start of TMP (preinfus ion: 45.9 +/- 13.9 ml/100 g/min. 30 min: 32.3 +/- 9.9 ml/100 g/min (P < 0.05). 60 min: 30 +/-7.5 ml/100 g/min (P < 0.05). These results sugg est that PGE1 may be preferable to TMP for hypotensive anaesthesia in spinal surgery because TMP decreased EBF.