Summary Eight modes of administration of propofol were assessed in order to minimise the pain of injection. An intravenous bolus injection in the antecubital fossa was the only approach that caused no pain. When administered intravenously in the dorsum of the hand the pain score and the number of patients who experienced pain was reduced significantly by mixing the agent with lignocaine when compared with a bolus injection. Slowing the speed of injection caused the greatest discomfort. An indirect biochemical mechanism for the pain is proposed.

SUmmARYThe relation between QT interval and heart rate has been studied in a group of patients undergoing physiological exercise, in a group undergoing atrial pacing without exercise, and in a group with complete heart block undergoing exercise at a fixed ventricular rate controlled by cardiac pacing. The expected shortening in QT interval during physiological exercise is only in part the result of the intrinsic effect of increased rate, since patients undergoing atrial pacing to comparable rates show only a small decrease in measured QT interval and patients exercising at fixed rates in heart block exhibit a decreasing QT interval related to the independent atrial rate. QT interval changes appear mainly to be governed by factors extrinsic to heart rate.The physiological control of QT interval has been used to construct a cardiac pacemaker which senses the interval between the delivered stimulus and the evoked T wave, and uses the stimulusevoked T wave interval to set the subsequent pacemaker escape interval. Thus physiological control of cardiac pacing rate, independent of atrial activity, using conventional unipolar lead systems is possible.The decrease in QT interval which occurs with exercise-induced changes in heart rate has long been recognised and has led to the use of formulae which correct the measured QT to a basic heart rate. The non-linear relation first described by Bazettl has been widely applied to derive this rate corrected QT interval (QTc) though Bazett himself pointed out the wide variation in individual subjects and only a limited amount of post-exercise data was included in his study. We have previously noted that during diagnostic atrial pacing the observed QT interval appeared to shorten less than during exercise at comparable heart rates. We have therefore re-examined the relation between heart rate and QT interval to determine those factors responsible for the change in ventricular repolarisation time. Patients and methods EXERCISE IN SINUS RHYTHMA group of 25 patients undergoing a treadmill exercise test was studied to re-evaluate the relation between QT interval and heart rate. All subjects were being investigated for ischaemic heart disease and were exercised according to the Bruce protocol.Twelve lead electrocardiograph recordings were made at a paper speed of 100 mm/s using a Cambridge automatic three-channel recorder complying with AHA standards. Recordings were made at rest, at 90 s intervals during exercise, immediately after exercise, and at 90 s intervals after exercise until the resting heart rate was reached. Measurements of rate and QT interval were made from the direct recordings. Data were excluded if a change in the QRS-T morphology occurred either because of artefact, ischaemic changes, conduction defects, or ectopic beats. Data were analysed for the group as a whole and subdivided into those patients taking beta-blocking drugs (15)

Pie-oxygenation was studied in I 2 j t volunteers and 20 patients using an oxygenJow of8 litreslminute delivered from a standard anaesthetic machine via a Uagill or Bain breathing attachment. End-tidal nitrogen concentrations of PA or less were achieved within 3 minutes; the fartest times were achieved using rhe Mngill breathing system when the reservoir bag wasfilled with oxygen prior to application to the face. Gas-tight fits of face masks on patients were found to be essential.

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