I.M. Corall

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.

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.

A further comment

giving a subarachnoid block for emergency Caesarean section. This reflects an unfortunate gap in their training, which may be related to the fact that many of the present generation of consultants were not trained in subarachnoid analgesia for obstetrirr--the writer included. A controlled trial in the sphere of maternal anaesthetic mortality is impossible but perhaps the basic principles of the problem should be considered. Protective respiratory reflexes exist for a purpose: their preservation must surely be Seen as a fundamental objective, and their abolition as a physiological trespass, the risks of which must be justified for each obstetric patient. These reflexes are abolished during induction of general anaesthesia at a time when the stomach must be assumed to contain highly acid material or possibly equally harmful particles of alkali. Rapid protection of the trachea (by tracheal intubation) cannot be guaranteed. This is a potentially hazardous situation, although it is argued that the anaesthetist with sufficient expertise and skilled assistance will always be able to steer the patient through it without mishap. Unfortunately, the coatinuing Occurrence of deaths, even in teaching hospitals where conditions are supposed to be good, would suggest that this argument is pie-in-the-sky. Effective management of difficulties is commendable; their avoidance is fundamentally more sound. The list of possible causes of death due to regional analgesia for Caesarean section also invites comment. Murphy’s Law states that if something can go wrong it will: sevcre hypotension might thus replace acid aspiration as a leading cause of mortality. However. hypotension of a life-threatening degree (when accompanied by reduced cardiac output) differs a s a hazard from intubation/acid aspiration problems in two important aspects. Firstly, if the basic principles of management of regional block in obstetric patients are observed. severe hypotension need rarely occur. whereas unpredictable tracheal intubation problems will continue to Occur, as will Mendelson’s syndrome pending the advent ofeffective prophylactic measures. Secondly. the treatment of severe hypotension is merely an extension of that of mild hypotension, with which any anaesthetist who practises regional analgesia in obstetncs should be thoroughly familiar. On the other hand failed intubation drill* cannot for ethical reasons be practised in the absence of genuine failure. and remains for many anaesthetists something which is learned for examinations and subsequently taught without ever being practised. Correspondence 287