RESPONSE OF ARTERIAL SEGMENTS FROM GRAVID HUMAN UTERUS TO MULTIPLE CONCENTRATIONS OF LIGNOCAINE

Nine uterine artery segments were obtained during Caesareanhysterotomy. The amount of isometric tension developed by eachsegment when exposed to 3, 6, 10, 20, 50, 100, 1000 and 2000-µg/mlof lignocaine hydrochloride (Xylocaine) was measured. All ninesegments contracted in response to the 1000- and 2000-µg/mlconcentrations. Eight of nine, six of nine, and three of nineresponded to the 100-, 50- and 20-µg/ml concentrations,respectively; one segment contracted in response to all concentrations.A dose-response curve indicated that maximum responses wereobtained at the 1000-µg/ml concentration (0.1%). Althoughlocal anaesthetics are usually considered vasodilators, thisstudy indicates that lignocaine causes the uterine artery toconstrict in concentrations in excess of 20µg/ml. Suchconcentrations might occur after paracervical block or accidentalintravascular injection, but would not be expected in associationwith extradural analgesia.     

PREDICTING THE ROTATIONAL PERFORMANCE OF TORIC SOFT LENSES

The major problems of meridional location in soft toric lens prescribing are examined The use of standard soft lens trial sets in the prescribing of toric lenses has been investigated and found to be of no value in regard to predicting the lens rotation of a prescribed toric lens. Appendices are included dealing with a theoretical interpretation of lens rotation as well as a consideration of methods for the determination of meridional location of soft lenses.     

Postshock Sensing Performance in Transvenous Defibrillation Lead Systems: Analysis of Detection and Redetection of Ventricular Fibrillation

Postshock Sensing in Transvenous Lead Systems. Introduction: The sensing performance of transvenous lead systems may be adversely affected by the delivery of high-energy shocks. This may be due to the proximity of the sensing and energy-delivery electrodes on transvenous leads. Methods and Results: The time required for detection of ventricular fibrillation and redetection after a failed first shock was compared in 93 patients with five different lead system-pulse generator combinations: Cadence^TM - Endotak^TM 60 series, Ventak P^TM - Endotak^TM 60 series, Jewel^TM - Transvene^TM, Cadence^TM - TVL^TM, and Cadence^TM - Transvene^TM. A total of 418 successful and 204 failed first shocks were delivered during induced ventricular fibrillation. Redetection times (RED) were consistently shorter than detection times (DET) in the Jewel-Transvene (RED minus DET: 1.9 ± 0.8 sec, P < 0.0001), the Cadence-TVL (-1.6 ± l.0sec, P < 0.0001), and the Cadence-Transvene combinations (-2.0 ± 0.9 sec, P < 0.0004). Redetection times were not significantly different than detection times in the Cadence-Endotak combination (-0.9 ± 3.1 sec; P = 0.09). Redetection times were significantly longer than detection times in the Ventak-Endotak combination (1.2 ± 2.3 sec; P = 0.034). Prolonged individual redetection episodes (> 8.2 sec) were observed in the Cadence-Endotak (7 [10%] of 73 episodes) and the Ventak-Endotak (4 [10%] of 39 episodes), but not in the Jewel-Transvene, the Cadence-TVL, and the Cadence-Transvene combinations. Conclusions: Redetection of ventricular fibrillation may be delayed in some transvenous lead-pulse generator combinations. Successful redetection of ventricular fibrillation following a failed first shock should be demonstrated prior to hospital discharge of patients with implantable defibrillators.     

The Autogenous Tissue Heart Valve: Current Status

Residual antigenicity of xenograft tissue after glutaraldehyde tanning may be a factor that determines calcification and durability of bioprostheses. We have pursued the concept of a nonantigenic, noncalcifying, more durable bioprosthesis. We previously described a technique for rapid intraoperative fabrication of an autogenous tissue heart valve (ATHV). That technique has been modified to improve reliability and ease of learning. With the modified technique, a geometrically perfect trileaflet valve can be made in 5 minutes. Although any suitable tissue can be used, the pericardial ATHV is the subject of this report. Autogenous pericardium immersed for 5 minutes in glutaraldehyde has proven satisfactory for valve construction. In vitro testing in the pulse duplicator and accelerated life tester has shown that the stent assembly is capable of function beyond 800,000,000 cycles without failure. In vivo testing has been performed in the juvenile sheep model as described by the National Institutes of Health group. Five sheep were maintained for 5 months postimplant before sacrifice. Explanted valves showed no tissue thickening or shrinkage, problems seen with earlier valves made with untreated autogenous tissue, and the leaflets remained pliable, free of the degenerative changes usually seen in the sheep model.     

The prevention of stimulant misuse

The term ‘stimulant’ refers to a class of drugs that increase psychophysiological arousal. From the viewpoint of prevention, it is more useful to look primarily at the social consequences and functions of stimulants. Every society has a documented use of stimulants. When planning interventions the dynamics of use must be placed in the foreground. Stimulant epidemics, like problematic stimulant users, have a natural tendency to burn themselves out. Different types of stimulants may differ in their origins, but their epidemiological consequences and use functions tend to be similar. Implications for prevention can be drawn from the characteristics of stimulant use epidemics. Users at risk for socially unacceptable patterns should be targeted for prevention efforts. Mass media campaigns that single out stimulants should be avoided. Much of the harm associated with stimulants is a consequence of life-styles characterized by polydrug use and unhealthy practices. Prevention should be timed to the appropriate period of the epidemic. Interventions useful at period I will not work at period 2. The recommendations of the WHO Advisory Group on the Adverse Effects of Cocaine and Coca provide a good model for primary, secondary and tertiary prevention for all forms of stimulant misuse. Stimulant prevention must be creative in finding ways of encouraging the movements of the drug to the periphery of users’lives.     

Improved Transesophageal Recording and Stimulation Utilizing a New Quadripolar Lead Configuration

Transesophageal pacing and recording are valuable techniques in the diagnosis and treatment of patients with arrhythmias. Bipolar pacing with bipolar catheters has been effective, but recording from the same electrodes is not possible during and immediately following pacing. We utilized a fine no. 4 French quadripolar catheter in 21 subjects to stimulate the atrium and record atrial electrical activity simultaneously. Pacing characteristics were equivalent to previously used bipolar catheters and recording was markedly enhanced. Bipolar atrial electrograms could be recorded either during pacing or at the first atrial depolarization following pacing in all patients. Thus, this quadripolar pacing lead improves the diagnostic value of studies involving transesophageal atrial pacing and recording.     

INTEGRATION OF HAEMOPHILIC BOYS INTO NORMAL SCHOOLS

Summary Advances in the medical treatment of haemophilia have made it possible for the majority of haemophilic children to attend ordinary rather than special schools. A survey carried out in the Glasgow and Edinburgh regions among families with haemophilic children and the schools which these children attend has drawn attention to certain implications of this new policy.