Acceptable ranges for vital signs during general anesthesia.

OBJECTIVE: Define the ranges for normal vital signs during general anesthesia.
METHODS: We studied 50 patients undergoing general anesthesia. We asked residents to state desirable ranges for each patient's systolic and diastolic blood pressure (BP), heart rate (HR), SpO2, and PETCO2 during induction, intubation, maintenance, and emergence from anesthesia. We called these ranges the clinical operating range (COR) and observed the frequency, duration, and magnitude of transgressions of these CORs. We also recorded whether the transgressions were treated or tolerated, or whether the COR values were changed.
RESULTS: Upper COR values in the maintenance phase for systolic BP were 38% +/- 20% above the preoperative values and 30% +/- 20% above the values recorded just before induction of anesthesia. Lower COR values in the maintenance phase for systolic BP were 27% +/- 9% below preoperative, and 31% +/- 11% below preinduction values. For HR, upper and lower COR values in the maintenance phase were 53% +/- 44% above and 38% +/- 17% below preinduction values, respectively. Transgressions of COR values for BP and HR were common, treatment frequent, and redefinition of COR values rare.
CONCLUSION: Clinicians recognize ranges for vital signs during uneventful anesthesia. These CORs may differ from one stage of anesthesia to the next. Transgressions of these ranges are common. Not all transgressions are treated.