EFFECTS OF HALOTHANE ON THE IMMATURE LAMB HEART

The choice of anesthesia during pregnancy and fetal operations is cont roversial. Halothane frequently is used, but its direct effects on fet al cardiac performance are unknown. The effects of halothane on fetal cardiac mechanics were studied in 8 fetal lamb hearts (135 days' gesta tion) using a modified Langendorff model connected to a membrane oxyge nator. The perfusate consisted of oxygenated maternal blood at a const ant now temperature, hematocrit value, and glucose level. Coronary blo od now, left ventricular systolic pressure, left ventricular end-diast olic pressure, and the developed left ventricular pressure at a fixed volume were evaluated at baseline and after the addition of incrementa l concentrations of halothane to the perfusate through the oxygenator. Perfusate halothane levels were maintained in a clinical range. Systo lic and diastolic cardiac function were adversely affected by the admi nistration of even low doses of halothane, despite a concomitant incre ase in coronary blood flow. Because of the immaturity of their calcium transport system, fetal hearts may be particularly sensitive to the k nown calcium channel-blocking properties of halothane.