The effects of general anaesthesia on heart rate variability during abdominal surgery

We aimed to realized a pilot study that investigated heart rate variability (HRV) during anesthesia to study of alterations in the autonomous function and study the effects of anesthetic drugs with a not invasive test. We studied 15 subjects of both sexes (9 women and 6 men) with a mean age of 53.6 ± 14.3 years. ECG signal recording, lasting 5 minutes each, in three times: First time, the registration before anaesthesia. The second was performed after anaesthesia induction and after 5 minutes after the start of maintenance. The third measurement was performed 24 hours after surgery. The mean heart rate did not show significant alterations during anesthesia and after 24 hours of surgery compared with baseline. On the contrary, the indices of heart rate variability in the frequency domain showed significant variations during general anesthesia. In fact there was a significant decrease in LF, expressed in normalized units and at the same time a significant increase in HF, always expressed in normalized units. It follows that the LF / HF ratio has been significantly reduced during the period of anesthesia. All indices are nearly returned to baseline after 24 hours of surgery. The analysis of anesthetic effects on HRV may provide a more valuable noninvasive tool for investigating alterations in autonomic function. Anesthetics used in general anesthesia suppress the autonomic nervous system and contribute to the safety of general anesthesia not only because suppress the excessive sympathetic activity caused by the operation but also because suppress parasympathetic reactions. The attenuation of sympathetic activity during general anesthesia is usually assessed by measuring changes in blood pressure or heart rate. In all cases, because of these antagonistic effects, evaluation becomes problematic when parasympathetic activity is simultaneously depressed.