The Use of Ephedrine for Prevention of Arterial Hypotensioi during Epidural Blockade: A Study of the Central Circulation after Subcutaneous Premcdication

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Abstract
The changes in central circulation following high epidural blockade in middle‐aged and elderly patients after subcutaneous premedication with ephedrine were compared with changes in patients not given ephedrine. The study was performed prior to elective surgery, after sedation with morphine and scopolamine. The circulatory effects of ephedrine premedication during epidural blockadc with local anaesthetics containing adrenaline, viz. bupivacaine 0.5% with adrenaline and etidocainc 1% with adrenaline (both with an adrenaline concentration of 5 μg.ml‐1), were compared with those obtaincd with a local anacsthetic agent without adrenaline, ctidocainc plain 1%. Ephedrine prcmcditation prevented marked hypotension following epidural blockade in all groups, the prcssor effcct being most pronounccd when adrenaline was included in the local anacsthetic solution. This adrenaline tended to increase the heart rate and cardiac output during the first 30 min and significantly decreased total peripheral resistance. The cardiac effects of adrenaline were not altered by ephcdrine. Ephedrine also prevented the bradycardia and reduction of cardiac output that tended to occur during epidural blockade of the upper two thoracic segments. The pressor effect of ephedrine premedication during high cpidural analgesia seemed to be due mainly to an increased total peripheral resistance when bupivacainc adrenaline or ctidocaine adrenaline was used, but with the use of ctidocainc plain it see med to be mediated by cardiac factors. The total peripheral resistance, however, was not increased to the preanalgesic value and the left ventricular minute work did not rise above the preanalgesic value.