Circulatory Effects of Peridural Block: III. Effects of Acute Blood Loss


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Abstract

High peridural analgesia was studied in 20 volunteers in whom peridural block was achieved before and after removal of 10 ml/kg blood to simulate mild acute hemorrhage. One group was given 2 per cent lidocaine containing 1:200,000 epinephrine, while in another group lidocainc alone was used. The group which received lidocainc–epinephrine during hypovolemia had a 30 per cent decrease in total peripheral resistance and a 6 per cent increase in cardiac output, resulting in a 23 per cent reduction in mean arterial pressure (MAP). Lidocainc alone was associated with severe cardiovascular depression, necessitating immediate treatment and termination of the study, in five of seven subjects. In the treated subjects, MAP decreased to 41 per cent of control, central venous pressure from 2.0 to —0.7 cm H2O3, and heart rate to 70 per cent of control, with brief periods (6-12 sec) of vagal arrest in two subjects. This severe cardiovascular depression was probably the result of vasomotor blockade and direct depression of the myocardium by lidocainc Therefore, high peridural analgesia with lidocainc alone should not be used for patients with hypovolemia. If peridural block is indicated, epinephrine should be added to the anesthetic solution or a vasoprcssor with myocardial stimulating action should be given to counteract lidocaine-induced cardiac depression.

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