Figure 2. Individual values for number of [Greek small letter beta]-adrenergic receptors per cell (B^max, A), isoproterenol-stimulated cyclic adenosine monophosphate (cAMP) production (isoproterenol-stimulated cAMP, B), and heart rate variability data (total frequency amplitude, C). Sampling times were before surgery (preop) and on the mornings of postoperative days (POD) 1, 2, 3, and 5 or 6 for patients undergoing thoracic ([white circle]) or abdominal ([white square]) surgery.