Cardiac Function During Halothane and Fluroxene Anesthesia Expressed by Systolic Time Intervals

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Abstract
A non-invasive method of measuring the systolic time intervals (STI) during anesthesia is described. Using the ratio between the pre-ejection period and the left ventricular ejection time (PEP/LVET-ratio) as an expression of cardiac function, it is shown in 39 patients that thiopentone exerted a marked depression on the heart (increase in PEP/LVET-ratio). This depression was further aggravated by halothane, while fluroxene caused an improvement of PEP/LVET-ratio. In the immediate post-anesthetic period PEP/LVET-ratio almost reached control value after discontinuation of fluroxene in contrast to halothane, where an increased PEP/LVET-ratio (25%) still persisted. The changes were mainly due to a prolongation of PEP without any specific change in LVET. During the study, PEP/LVET-ratio showed a close correlation to the reciprocal value of the square of the pre-ejection period (1/PEP-2). STI form 27 volunteers were measured and compared to the values from the patients before anesthesia was induced. PEP and PEP/LVET-ratio were significantly shorter in the patient group.