Some Observations of Critical Closing Pressures in the Peripheral Circulation of Anaesthetized Patients.

Critical closing pressures have been measured in the hand vessels of anaesthetized patients undergoing elective surgery by a method as close as possible to that used in previous studies on conscious subjects. The critical closing pressure has been found to vary considerably during anaesthesia. In general, the variations are parallel to those of the systolic blood pressure. No correlation has been found between the critical closing pressure and the pre-operative blood pressure. It is therefore suggested that findings in conscious volunteers cannot be used to assess the possibility of critical closure during anaesthesia; it appears necessary to measure the critical closing pressure during anaesthesia.