SPHYGMOMANOMETER BLADDER LENGTH

975 comual rupture of the uterus was inevitable and any resultant surgery would have terminated the intrauterine pregnancy. In an attempt to maintain the intrauterine pregnancy and to remove the need for acute surgery, an 18 gauge spinal needle was passed through the bladder (distended with Hartmann’s solution) and guided free-hand into the comual gestation sac under ultrasound control with the patient under light general anaesthesia. Potassium chloride 0-5 ml (20% w/v solution) was injected into the sac and the contents were aspirated after cessation of cardiac activity. There were no complications. Subsequent ultrasound scan showed resolution of the cornual ectopic pregnancy and continuation of the

intrauterine gestation. The two other patients had left ampullary ectopic pregnancies of 6-8 weeks’ duration and were anxious to avoid further gynaecological surgery. They were treated in exactly the same manner. Although both became free of abdominal discomfort, serial ultrasound scans performed over a further 6 weeks indicated persistence of an adnexal mass and positive 0-hCG values in the low pregnancy range. Ultimately, both underwent laparotomy: the tubal masses measured 10 x 7 and 8 x5 cm and histological examination confirmed the presence of necrotic villous tissue. We feel that this approach, made possible by the developments in imaging techniques and skills gained by ultrasound aspiration of ovarian cysts and oocyte retrieval for in vitro fertilisation, has a place in the management of comual pregnancy, and possibly also of tubal ectopic pregnancy-provided that the agent instilled completely destroys trophoblastic tissue. The report from Feichtinger and Kemeter indicates that methotrexate is preferable to potassium chloride.

Fertility and IVF Unit, Humana Hospital Wellington, London NW8 9LE

D. E. ROBERTSON W. SMITH P. R. BRINSDEN M. AH. MOYE P. M. LEWIS J. N. HANSEN P. SERHAL E. G. SIMONS I. L. CRAFT

SPHYGMOMANOMETER BLADDER LENGTH

SiR,—I agree with Dr Vyse’s conclusion (March 7, p 561) that sphygmomanometer bladders that are too short tend to overestimate blood pressure. However, not only the length of the inflatable bladder, but even more so the design of the covering cloth (for bladder widths under 8 cm) may influence the readings. In fact, systolic blood pressure readings obtained with conventional ’Velcro’ self-adhesive cuffs (bladder dimensions 4 x 20 and 55 x 23 cm) in 40 children aged under 4 years were higher by an average of 13-22 mm Hg than those obtained with the same bladders wrapped around the arm and held by a separate velcro band.1 This error was mainly attributable to the rigid velcro sewn on the cuff. Many blood pressure cuffs that are commonly available for infants and young children are too short23or otherwise inappropriate. An international agreement on recommendations is needed. University Children’s Hospital, 8032

E. LEUMANN

Zurich, Switzerland

1 Leumann EP, Haller V,

Spiess B, Arbenz U. Cuff-associated errors of bloodpressure recording m infants and toddlers. Clin Exp Hyperten 1986; AS: 605-10. 2. Task Force on Blood Pressure Control in Children. Report of the Second Task Force on Blood Pressure in Children-1987. Pediatrics 1987; 79: 1-25. 3 Leumann EP, Spiess B. Requirements for paediatric blood pressure cuffs. Helv Paediatr Acta 1984; 39: 117-22.

SODIUM-CHANNEL INHIBITORS PRODUCED BY ENTEROPATHOGENIC VIBRIO CHOLERAE AND AEROMONAS HYDROPHILA

SIR,- Vibrio cholerae has been extensively studied to determine virulence mechanisms leading to enteropathogenic disease. Potential virulence factors include cholera toxin, cytotoxins, and

haemolysins. However,

all factors

responsible for clinical disease

have not yet been defined. Recently it has been reported that tetrodotoxin (puffer fish toxin) and related sodium-channel inhibitors are produced by bacterial This observation led us to investigate the production of these compounds by V cholerae, an organism considered by us to be

autochthonous to the marine environment. We report the detection of sodium-channel inhibitor(s) in cultures of pathogenic V cholerae (01 and non-01 serotypes) and Aeromonas hydrophila. Concentrations of inhibitor ranged from 100 ng to 5 ng/1 culture: Bacterial species Inhibitor (ngll culture!* V cholerae CVD101 569B 14035 V69 A hydrophila 19570 SSU

100 10 10 5 5 10

’Approximate concentration of inhibitor, measured by inhibition of veratridine stimulation of sodium channels.

Culture extracts inhibited the biological effect of sodium-channel stimulator (01 mmol/1 veratridine), displaced binding of radiolabelled saxitoxin to rabbit brain membrane sodium-channel receptors, and inhibited the compound action potential of frog sciatic nerve. V cholerae strain (CVD 101) produced nearly 10-fold more sodium channel inhibitor than did other strains of V cholerae, including type strain 569B. It has been reported that this recombinant strain does not produce the toxic fragment of cholera toxin, yet causes a mild diarrhoea in volunteers.3 The chemical structure of the V cholerae and A hydrophila sodium-channel inhibitor(s) is being determined. Chromatographic evidence, coupled with activity in the highly selective displacement assay, suggests that the active compound is tetrodotoxin or a group of compounds related to it. This accords with recent reports that tetrodotoxin is produced by marine bacteria. We are currently investigating the role of these sodium-channel inhibitors in the diseases caused by these enteropathogens. Center of Marine Biotechnology, University of Maryland

M. L. TAMPLIN

Department of Microbiology, University of Maryland, College Park, Maryland, USA

R. R. COLWELL

Center for Food Safety and Applied Nutrition, Food and Drug Administration, Washington, DC

S. HALL

Ocean Research Institute, University of Tokyo,

Tokyo, Japan

K. KOGURE

Harvard Medical School, Brigham and Women’s Hospital, Boston, Massachusetts

G. R. STRICHARTZ

1. Noguchi T, Jeon J, Arakawa O, et al. Occurrence of tetrodotoxin and anhydrotetrodotoxin in Vibrio sp isolated from the intestines of a xanthid crab, Atergatis floridus. J Biochem 1986; 99: 311-14. 2. Colwell RR, Seidler RJ, Kaper J, et al. Occurrence of Vibrio cholerae serotype Ol in Maryland and Louisiana estuaries. Appl Environ Microbiol 1981; 41: 555-58. 3. Kaper JB, Levine MM, Lockman HA, et al. Development and testing of a recombinant live oral cholera vaccine. In: Vaccines 85. Molecular and chemical basis of resistance to parasitic, bacterial, and viral disease. Cold Spring Harbor, NY: Cold Spring Harbor Laboratories, 1985: 107-11.

SKULL X-RAYS AFTER HEAD

INJURY

SiR,—I disagree with the conclusions in your editorial (March 21, p 667) about skull X-rays in head-injured patients. The implications of the presence (or absence) of a skull fracture are of undoubted significance to clinicians.1 I have studied 12 395 accident-and-emergency attenders with head injury, whether X-rayed or not. 5484 patients (44 2%) had a plain skull X-ray and 206 (38%) of these had a fracture. Only 0-7% of all attenders had clinical signs of skull fracture and, in almost half of this small group, the skull X-ray was normal. Thus in 99 % of cases the absence of a fracture could only be determined by an X-ray. 11 patients had acute post-traumatic intracranial haematomas. 8 of these had a skull fracture on X-ray, 2 had a fracture clinically, and the remaining patient had no fracture. Thus, there was a significant association between radiologically proven fractures and the development of an acute haematoma. The relative risk of a patient with a skull fracture on X-ray having an acute haematoma was 164 times that of a patient without a fracture. For a patient with a fracture of the skull