Studies of anaesthesia in relation to hypertension. VI: Cardiovascular responses to extradural blockade of treated and untreated hypertensive patients.

The haemodynamic effects of extradural blockade were investigated in 25 hypertensive patients divided into three groups: 11 treated patients receiving lumbar extradural blockade (LT), nine treated hypertensive patients receiving thoracic extradural blockade (TT), and five untreated patients receiving lumbar extradural blockade (LU). Haemodynamic measurements were performed before and after the establishment of the extradural blockade, and repeated with the patients under light general anaesthesia. Mean upper level (T7) and range (T4-S1) of sensory blockade were similar in the two lumbar extradural groups, and mean segmental spread in the TT group was T4-L1. Changes from baseline to lowest arterial pressure showed a 22% (P less than 0.01) decrease in MAP in the LT group, 18% (P less than 0.05) in the TT group, and 42% (P less than 0.05) in the LU group. The decrease in arterial pressure was associated with a decrease in SVR in the LT group, and also with a decrease in cardiac output in the LU group. Three of the five untreated hypertensive patients demonstrated unacceptable decreases of arterial pressure, associated with abrupt and severe bradycardia, and required immediate treatment (head-down tilt, atropine and methoxamine). These complications were not observed in any of the treated hypertensive patients (P = 0.018).