Influence of Anesthetic Agent on Response to Hemorrhagic Hypotension

Survival times and hemodynamic, metabolic, and sympathoadrenal responses to progressive hemorrhagic hypotension were determined in dogs subjected to blood removal of 10 ml/kg/30 min during MAC anesthesia with cyclopropane, isoflurane, and halothane. Mean survival times ranged from 146 minutes (cyclopropane plus succinylcholine) to 247 minutes (halothane). Initially, hemodynamic function was better maintained with cyclopropane, with or without succinylcholine, and arterial epinephrine and lactate concentrations increased earlier than with isoflurane or halothane. However, with further unreplaced blood loss, hemodynamic function, O2 uptake, and acid–base balance were sustained better with either isoflurane or halothane than with cyclopropane. Further studies showed that increased lactate concentration resulted from increased epinephrine concentration. During hemorrhage the initial maintenance of arterial pressure by agents such as cyclopropane, which enhances sympathoadrenal response to hemorrhagic hypotension, is achieved by mechanisms lessening the ability to survive additional blood loss. These augmented responses are, overall, undesirable additives to the anesthetic circumstance.