Key result
Major abdominal or thoracic surgery was associated with significant decreases in heart rate variability, beta-adrenergic receptor number, and cAMP production throughout the first postoperative week.
Why the study?
Does major noncardiac surgery alter autonomic nervous system function and beta-adrenergic receptor activity in the first postoperative week?
Observational (n=28)
Does major noncardiac surgery alter autonomic nervous system function and beta-adrenergic receptor activity in the first postoperative week?
Major noncardiac surgery induces persistent downregulation of the beta-adrenergic receptor system and decreases heart rate variability for at least one week postoperatively, reflecting adaptive autonomic regulatory mechanisms.
May heighten perioperative vulnerability; leaves open whether autonomic-targeted interventions improve outcomes after major noncardiac surgery.
UNLABELLED: BACKGROUND. Changes in the sympathetic nervous system may be a cause of postoperative cardiovascular complications. The authors hypothesized that changes in both beta-adrenergic receptor (betaAR) function (as assessed in lymphocytes) and in sympathetic activity (assessed by plasma catecholamines and by heart rate variability [HRV] measurements obtained from Holter recordings) occur after operation. METHODS: The HRV parameters were measured in 28 patients having thoracotomy (n = 14) or laparotomy (n = 14) before and for as long as 6 days after operation. Transthoracic echocardiography was performed before and on postoperative day 2. Lymphocytes were also isolated from blood obtained before anesthesia and again on postoperative days 1, 2, 3, and 5 (or 6). They were used to examine betaAR number (Bmax) and cyclic adenosine monophosphate (cAMP) production after stimulation with isoproterenol and prostaglandin E1. In addition, plasma epinephrine, norepinephrine, and cortisol concentrations were determined at similar intervals. RESULTS: After abdominal and thoracic surgery, most time and all frequency indices of HRV decreased significantly, as did Bmax and basal and isoproterenol-stimulated cAMP production. The decrements in HRV correlated with those of Bmax and isoproterenol-stimulated cAMP throughout the first postoperative week and inversely correlated with the increase in heart rate. Plasma catecholamine concentrations did not change significantly from baseline values, but plasma cortisol levels did increase after operation in both groups. Left ventricular ejection fraction was normal in both groups and unaffected by surgery. CONCLUSIONS: Persistent downregulation and desensitization of the lymphocyte betaAR/adenylyl cyclase system correlated with decrements in time and frequency domain indices of HRV throughout the first week after major abdominal or thoracic surgery. These physiologic alterations suggest the continued presence of adaptive autonomic regulatory mechanisms and may explain why the at-risk period after major surgery appears to be about 1 week or more.
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Amar et al. (1998) conducted an observational in Noncardiac surgery (thoracotomy or laparotomy) (n=28). Major abdominal or thoracic surgery vs. Baseline (preoperative) was evaluated on Heart rate variability (HRV) parameters, beta-adrenergic receptor number (Bmax), and cyclic AMP production. Major abdominal or thoracic surgery was associated with significant decreases in heart rate variability, beta-adrenergic receptor number, and cAMP production throughout the first postoperative week.
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