Changes in heart rate variability during midazolam sedation with TCI in elderly and young patients / 中华麻醉学杂志

ABSTRACT

Objective To assess the changes in heart rate variability (HRV) during midazolam sedation with TCI in the elderly and young patients. Methods Thirty-eight ASA I - Ⅱ patients scheduled for elective surgery on lower abdomen or lower extremities under epidural or combined epidural-spinal anesthesia were divided into two groups of 19 patients each the young group (18-40 yr) and the elderly group (60-89 yr). Radial artery was cannulated for intra-arterial pressure monitoring and blood sampling. HRV was monitored by HXD-1 monitoring system. HRV parameters included total power (TP), low frequency(LF), high frequency(HF), LF/HF, nuLF(LF/TP ?100%) and NuHF(HF/TP ? 100%) . The height of block was maintained below T5. TCI was used to achieve a rapid induction and maintenance of a stable target blood midazolam concentration. Target blood midazolam concentration was started from 50 ng/ml and gradually increased with increment of 25 ng/ml in elderly group or 50ng/ml in the young group until loss of consciousness (OAA/S =1). Arterial blood samples were taken at each target blood midazolam concentration for determination of blood midazolam concentration. HRV parameters were recorded at different OAA/S scores during both the induction of and recovery from sedation. Results With increasing depth of sedation, most of the HRV parameters (LF, nuLF, LF/HF and TP) decreased progressively, while nuHF increased and HF remained unchanged. During recovery from midazolam-induced sedation, HRV parameters returned gradually to the baseline values. OAA/S scores and HRV parameters were well correlated(r = 0.502-0.719). The trend of changes in HRV was consistent in both groups. At the same OAA/S score, most values of HRV parameters were not significantly different between the two groups. Only during deep sedation (OAA/S=1), values of all HRV parameters were significantly lower in the elderly group than those in the young group, except LF/HF. Conclusions During profound sedation (OAA/S=1) midazolam depresses the activity of the autonomic nervous system more markedly in the elderly than in the young, but the elderly without cardiovascular and autonomic nervous system disorders has the same ability to keep the balance between the sympathetic and parasympathetic nervous system as theyoung.