D. John Doyle

Reflex bradycardia during surgery

Reflex bradycardia and sinus arrest may occur in a variety of surgical procedures, from neurosurgery to general abdominal, laparoscopic, opthalmic and facial surgery and even procedures such as liver biopsies and electroconvulsive therapy. In most cases a vagallymediated reflex has been implicated, although experimental support for this is often lacking. Drugs such as vecuronium, atracurium, halothane, fentanyl and succinylcholine may predispose to this reflex. Premedication with an anticholinergic is usually effective in preventing its occurrence.RésuméUne bradycardie réflexe et/ou un arrêt sinusal peuvent survenir lors de tout un éventail d’interventions allant de la neurochirurgie à la chirurgie abdominale, laparoscopique, ophtalmique et faciale en passant par la biopsie du foie et les électrochocs. Malgré l’absence de confirmation expérimental solide, on a souvent insisté sur le rôle du nerf vague dans cé réflexe. On sait qu’entre autres, le vécuronium, l’atracurium, l’halothane, le fentanyl et la succinylcholine peuvent en favoriser l’apparition, alors qu’un anticholinergique en prémédication pourra habituellement le prévenir.

Analysis of intracranial pressure

Methods for the acquisition and analysis of intracranial pressure (ICP) signals are reviewed from clinical and technical perspectives. The clinical importance of ICP monitoring is presented, and methods for ICP transduction are briefly discussed. These methods include intraventricular catheters, subarachnoid screws, epidural techniques, and the new fiberoptic ICP measurement systems. Approaches to the visual analysis of the ICP waveform are presented, with special emphasis on the relationship between the ICP waveform and the arterial blood pressure signal. Methods of computer-based ICP analysis are also reviewed, including histogram and “systems analysis” methods. Methods to predict ICP pressure rises and to estimate intracranial compliance are also discussed. Finally, ICP monitoring is reviewed from the point of view of patient outcome. It is concluded that advanced ICP waveform analysis methods warrant further clinical evaluation to demonstrate their clinical usefulness.

Ketamine induction and monoamine oxidase inhibitors

A 42-year-old woman taking tranylcypromine, a monoamine oxidase (MAO) inhibitor, was hypovolemic from a ruptured ectopic pregnancy and required an emergency laparotomy. Anesthetic induction with ketamine, an agent with sympathomimetic properties, was used because of her hypovolemia, despite theoretical concerns of precipitating an adrenergic crisis. The patients hemodynamic course remained unchanged with induction and intubation, and with further fluid and blood administration, satisfactory hemodynamic conditions were obtained. This report is believed to be the first to describe the use of ketamine in a patient taking MAO inhibitors.

Respiratory consultant: a hand-held computer-based system for oxygen therapy and critical care medicine

The assessment of respiratory system performance may involve issues such as pulmonary gas exchange, respiratory mechanics, oxygen transport and other factors. This paper describes an MS-DOS program called Respiratory Consultant that was designed for use with a hand-held MS-DOS computer, but can also run under Windows 3.1 and Windows 95 if desired. Respiratory Consultant performs a number of computational tasks potentially appropriate to respiratory care in the ICU and elsewhere. These include: predicted arterial oxygen tension from age, interconversion of oxygen tension and saturation, calculation of gas exchange indices and oxygen transport parameters, dead-space estimation, and pulmonary function test interpretation. Respiratory Consultant is freeware that will run easily on most IBM-compatible PCs and may be downloaded from the Internet.

Continuous measurement of central venous pressure by manometry.

An alternative method is described for measurement of central venous pressure by insertion of a right atrial catheter with a connection to a fluid-column manometer. With this method, the central venous pressure can be monitored by visual inspection of the manometer column; the stopcock does not need turning; the manometer column does not need refilling; and the catheter is always being flushed, eliminating the risk of clotting.An alternative method is described for measurement of central venous pressure by insertion of a right atrial catheter with a connection to a fluid-column manometer. With this method, the central venous pressure can be monitored by visual inspection of the manometer column; the stopcock does not need turning; the manometer column does not need refilling; and the catheter is always being flushed, eliminating the risk of clotting.

Inexpensive temperature monitor for heated humidifiers

A commercially available indoor/outdoor electronic thermometer has been adapted to monitor both airway gas temperature and operating room temperature when heated humidifiers are used. Heated humidifiers that do not have temperature monitoring capabilities pose a risk of dangerously high inspired gas temperatures.A commercially available indoor/outdoor electronic thermometer has been adapted to monitor both airway gas temperature and operating room temperature when heated humidifiers are used. Heated humidifiers that do not have temperature monitoring capabilities pose a risk of dangerously high inspired gas temperatures.