Cardiovascular autonomic response during preoperative stress and postoperative pain.

Heart rate response to physiologic maneuvers was used to evaluate autonomic nervous system (ANS) function in normal control subjects and during the stress and pain experienced by patients before and after surgery. In preoperative patients (stressed without pain) and postoperative patients (stressed with pain), maneuvers which routinely increase activity in the parasympathetic or sympathetic divisions of the ANS produced only 50% of the response seen in control subjects. The heart rate response was not further reduced in patients with pain compared to patients with stress alone. The difference in heart rate response between surgical patients and control subjects was not accompanied by a difference in baseline heart rate. The data suggest that tonic stress impairs the ability of the ANS to respond fully to perturbing influences.