Leo Strunin

Monitoring Cerebral Function: Clinical Experience with New Device for Continuous Recording of Electrical Activity of Brain

A device, the cerebral function monitor, provides a continuous record of the electrical activity of the brain occurring at frequencies from 2 to 15 Hz. It is relatively cheap, portable, and easy to use and interpret. The apparatus has proved of value in three circumstances: firstly, when the cerebral circulation is likely to be vulnerable during open heart surgery; secondly, as a measure of recovery or deterioration following brain damage or drug overdose; and thirdly, where information about more physiological changes in cerebral function is required, for instance when testing anaesthetic and hypnotic drugs.

The cerebral function monitor. Its value in predicting the neurological outcome in patients undergoing cardiopulmonary by-pass.

Continuous monitoring of cerebral activity by conventional electroencephalography during cardiac surgery with cardiopulmonary by-pass has proved valuable,’ J but such monitoring is costly, both in terms of the experienced staff and the bulky apparatus required. A device, the Cerebral Function Monitor (CFM),* has been claimed to be a suitable alternative, partly because of the ability to reject artefacts encountered in the operating theatre and the provision of continuous monitoring of electrode impedance and of any other malfunctionings in the ~ y s t e r n . ~ , ~ This apparatus has the advantage that quantification is readily made by simple measurements of tracings obtained both during and after surgery. In contrast, the conventional electroencephalogram (EEG) is less readily amenable to quantification by simple measurement. Preliminary studies indicated that the CFM was of value during cardiac surgery,’ and in the present communication we report in more detail a retrospective analysis of 100 patients. The CFM tracings were assessed in the first instance without reference to clinical information to establish whether there were changes in cerebral activity during surgery which could predict neurological outcome. These predictions were compared subsequently with the actual outcome.

Sedation for outpatient conservative dentistry. A trial of pentazocine supplementation to diazepam and local analgesia techniques.

Pentazocine 30 mg. or 15 mg or a placebo, was administered randomly to forty-nine patients undergoing conservative dental treatment in combination with a local analgesic block and intravenous diazepam. Simple cardiorespiratory measurements were made throughout the treatment period. Patients in the 30 mg pentazocine group required some 6 mg diazepam less than the placebo (control) group (P less than 0.05). Patients receiving 15 mg pentazocine also required less diazepam compared to the control group, but this difference was not statistically significant. There were no significant differences between the three groups either in recovery times or the cardiorespiratory measurements.

Assessment of the Von Recklinghausen oscillotonometer

The Von Recklinghausen Scala Alternans Altera oscillotonometer was assessed in order to establish whether any of the disputed points over its use made a significant difference to the readings obtained. Inversion of a new cuff gave significantly higher systolic readings, but a worn cuff gave consistent results whatever its position. Measurements of systolic and diastolic pressures were not significantly affected by the use of the sustained leak lever provided the leak was small. Maintenance and cleaning of the instrument are essential for its proper working.

Blood carbon dioxide tension changes during hysteroscopy.

During hysteroscopy the uterus may be distended with carbon dioxide (CO2), nitrous oxide (N2O), or Hyskon (a high molecular weight dextran). An initial study in 27 patients (group 1) using arterialized venous blood samples demonstrated rises in carbon dioxide tension (PCO2) when N2O was insufflated by using a laparoscopy insufflating device--a constant-pressure, variable-volume gas source. Cardiovascular collapse occurred in one patient in this group, most probably as a result of macropulmonary emboli of N2O. The rise in PCO2 is accounted for by an increase in physiologic dead space. In another 24 patients (group 2) the gaseous media were introduced by using a constant-volume, variable-pressure gas source; this resulted in minimal changes in arterial PCO2. The choice of whether a gaseous or liquid distending medium is used for hysteroscopy is governed by the state of the endometrium. If a gaseous medium is indicated, then CO2 is preferable to N2O and should be introduced with a constant-volume, variable-pressure gas source.