PREVENTION OF VENOUS THROMBOSIS

419

whether

residual clots should be removed (or, as is occaa peripheral vein should be ligated). sionally In view of the evidence1 that a mixture of meglumine iothalamate 52% w/v and sodium iothalamate 26% w/v (’ Cardio Conray ’) is less cardiotoxic than other contrast necessary,

we feel that it might have been preferable to use this agent to one containing only the sodium salt. In the editorial comments on this paper we feel that the suggestion that streptokinase should be used alone is unsatisfactory. This means that patients would have to wait without treatment until completion of pulmonary angiography. There must inevitably be a delay before treatment is started, and it is vital during this period to prevent extension of the thrombus and embolus. The phrase " concentrated local attack " is probably not justified because the dosage used by Mr. Kakkar and Dr. Raftery would produce a state of total-body clot lysis. J. H. E. CARMICHAEL AVERIL O. MANSFIELD Broadgreen Hospital, E. W. PARRY. Liverpool 14.

media,

gradually. A brain-scan carried out at the regional neurosurgical unit at Walton Hospital 6 days after admission showed a small, but definite, rather triangular, area of increased uptake in the left parietal lobe in thearea close to the lower end of the sylvian fissure. The patient’s general condition improved steadily and the headache disappeared. She was last seen, apparently completely well and active, on March 25, 1970. She had had no further difficulty with her speech and her powers of calculation had also improved. Examination of the central nervous system was completely negative. Many features of this case resemble closely those described by Dr. Atkinson and his colleagues-notably (1) abrupt onset of headache followed by vomiting; (2) disturbance of consciousness with varying levels of drowsiness; (3) pyrexia without corresponding increase in pulse-rate; (4) minimal neck stiffness; (5) papillcedema, (6) signs of focal brain damage; and (7) red-cells in c.s.F. (up to 4900 per c.mm.). The clinical picture, together with the brain-scan evidence of infarction, strongly favoured the diagnosis of cortical thrombosis. We believe that a brain-scan is of considerable diagnostic value in cases such as this. We thank Dr. R. B. McConnell, consultant physician at the

venous

INTRACRANIAL VENOUS THROMBOSIS COMPLICATING ORAL CONTRACEPTION SIR,-We were interested in the report by Dr. Atkinson and his colleagues2 describing 6 cases of intracranial venous thrombosis occurring in women taking oral contraceptive drugs. We wish to report a similar case with spontaneous recovery. A 22-year-old married hospital on Jan. 23, 1970.

admitted to this Her illness had begun 5 days previously with left-sided frontal headache and pain in the neck of fairly acute onset. This had become steadily worse over the next 3-4 days, when she began to vomit and became drowsy and disorientated; later she complained of hazy vision in the left eye. She had been pyrexial with varying degrees of drowsiness up to the time of admission. She had been taking ’Gynovlar ’ (norethisterone acetate 3 mg., ethinyloestradiol 0-05 mg.) for the previous 2 years. On admission she was conscious and cooperative, but woman

was

drowsy. The oral temperature was 99,soF, pulse-rate 60 per minute, blood-pressure 100/60 mm. Hg. There was slight neck-stiffness, but Kernig’s sign was negative. There was pronounced nominal dysphasia and a dyscalculia. The optic-disc margins were indistinct and the retinal veins engorged. Nervous-system examination was otherwise normal. Lumbar puncture produced slightly turbid cerebrospinal fluid (c.s.F.) at a pressure- of 210 mm. H2o. Manometry was normal. The fluid contained 4950 redcells per c.mm., no white blood-cells, protein 40 mg. per 100 ml., glucose 62 mg. per 100 ml., chloride 730 mg. per 100 ml., and slightly increased globulin. Skull X-rays were normal (no displacement of calcified pineal), as was a chest X-ray. X-rays of the cervical spine were normal apart from reversal of lordosis and partial fusion of C3 and C,. Diagnoses considered at this stage were cortical venous thrombosis, cerebral abscess, viral encephalitis, and cerebral arterial thrombosis. After neurosurgical consultation, it was decided that she should be observed closely and given intramuscular ampicillin, 500 mg. 6-hourly, in addition to analgesics. (Gynovlar was withdrawn.) Over the next 4 days her general condition improved, although she maintained a slight pyrexia just below 99 F and a persistent

bradycardia of

50-60 per minute. The headache lessened and the nominal aphasia and dyscalculia became less obvious. The appearances of the optic fundi improved 1. Somers. K., Patel, A. K., Fowler, J. M., D’Arbela, P. G. Br. J. Radiol. 1968, 41, 678 2. Atkinson, E. A., Fairburn, B., Heathfield, K. W. G. Lancet, 1970, i, 914.

David Lewis Northern Hospital, Liverpool, and Mr. A. K.

Frazer,

consultant neurosurgeon, Regional Neurosurgical Unit, help in producing this report, and Dr. J. V. Occleshaw, consultant radiologist, also of the Regional Neurosurgical Unit, Walton Hospital, for his interpretation and helpful comments on the brain-scan done in his department.

Walton Hospital, for

David Lewis Northern Liverpool 3.

Hospital,

CLIFFORD SISSONS D. R. HALL.

PREVENTION OF VENOUS THROMBOSIS SIR,-Your leader on this subject1 praises several important points. The difficulty of establishing the true incidence of postoperative venous thrombosis by clinical diagnosis alone has been highlighted by several groups using more precise diagnostic procedures such as phlebography and 125l-labelled fibrinogen.2-s Thus, in patients undergoing gynaecological procedures or operations for fractures of the femoral neck the frequency of postoperative venous thrombosis was found to be between 30 and 50%, 1,5,7-10 These high figures emphasise the importance of prophylaxis against thrombosis. The bleeding risk and the difficulties of controlling anticoagulant therapy have focused interest on other forms of prophylaxis; and in this respect, dextran has been shown to reduce the incidence of postoperative venous thrombosis without incurring the problems of anticoagulation. 11 However, whether or not this reduction is accompanied by a reduction in the incidence of fatal pulmonary embolism is not yet clear. Although several series suggest that dextran protects postoperative patients from fatal pulmonary embolism, the number of patients in each is insufficient to permit statistical analysis. It would therefore be of interest 1. 2.

Lancet, 1970, i, 395. Borgstrom, S., Greitz, T., van der Linden, W., Molin, J., Rudies, I. Acta chir. scand. 1965, 129, 500. 3. Flanc, C., Kakkar, V. V , Clarke M. B. Br. J. Surg. 1968, 55, 742. 4. Lambie, J. M , Mahaffy, R. G., Barber, D. C., Karmody, A. M., Scott, M. M., Matheson, N A. Br. med. J. 1970, ii, 142. 5. Myhre, H. O., Holen, A. Nord. Med. 1969, 82, 1534. 6. Sevitt, S. Am. J. Med. 1962, 33, 703 7. Ahlberg, A., Nylander, G., Robertson, B , Cronberg, S., Nilsson, I. M. Acta chir. scand. 1968, suppl 387, p. 83. 8. Ahlberg. A. in Trombos och status posttromboticus Symposium; p. 89. Lund, 1969. 9. Johnsson, S R.. Bygdeman, S., Eliasson, R. Acta chir. scand. 1968, suppl. 387, p. 80. 10. Lambie, J. M., Barber, D. C., Dhall, D. P. Matheson, N. A. Br. med. J. 1970. ii, 144. 11 Bygdeman. S. Prog. Surg. 1969. 7, 114.

420 TRIALS OF DEXTRAN-70

combine the results of all controlled studies in which dextran 70 (’Macrodex’) has been compared with either untreated controls or controls given saline or glucose. Such a comparison is made in the accompanying table. (Dr. Stadil has already discussed his findings in The Lancet.16) It is clear that dextran treatment significantly reduces the frequency of fatal postoperative pulmonary embolism. All studies in which surgical patients had been randomly allotted to control and treatment groups and where the diagnosis of fatal pulmonary embolism was made at necropsy have been included. In most of these investigations the number of patients who had non-fatal pulmonary embolism was also recorded. The overall number of embolic episodes was reduced from 51 in the control group to 15 in the dextran-treated group. These results indicate that prophylactic dextran therapy offers a safe and effective means of reducing the incidence of postoperative thromboembolic complications.

to

Department of Physiology, Faculty of Medicine, Karolinska Institutet, Stockholm, Sweden. Department of Medical Research, Pharmacia AB, Uppsala, Sweden.

STELLAN BYGDEMAN. ERIK SVENSJÖ GUNNAR TOLLERZ.

ANIMAL SOURCES OF ESCHERICHIA COLI IN FOOD SIR,-The report by Professor Shooter and his colleagues (Aug. 1, p. 226) was extremely interesting, not only because the results suggest a possible route for transmission of animal strains of Escherichia coli to man via recontaminated food but also since it shows the necessity for proper training in food hygiene for catering officers and kitchen staff. The fact that E. coli was isolated from washing-up water suggests that suitable concentrations of a detergent-sanitiser were not used, that the temperatures of the washing-up and rinsing waters were too low, and that these waters were not changed at sufficiently frequent intervals. Ideally, washed utensils should be rinsed for a period of not less than 30 seconds in water at a minimum temperature of 77°C. The Barts workers might have drawn additional conclusions from their data. Firstly, certain serotypes of E. coli have been implicated in outbreaks of gastroenteritis, particularly in infants. Although a full serological analysis was not undertaken in the present investigation, certain serotypes isolated are related to known enteropathogenic strains Atik, M., Harkess, J. W., Wichman, H. Surgery Gynec. Obstet. 1970, 130, 403. 13. Elsner-Mackey, P., Ledermair, O., Schastok, H., Vinazzer, H. Wien. med. Wschr. 1969, 119, 149. 14. Jansen, H Lancet, 1970, i, 838. 15. Stadil, F Ugeskr. Lag. (in the press). 16. Stadil, F. Lancet, July 4, 1970, p. 50. 17. Hobbs, B. C. Food Poisoning and Food Hygiene. London, 1968.

12.

of E. coli-e.g., strains 018:K76; 018:K77; and 020.18 Cross-contamination of prepared foods by handlers and/or from utensils is a serious problem which requires attention if serious outbreaks of infantile food-poisoning are to be prevented, and the evidence presented by Professor Shooter and his colleagues suggests that such outbreaks might be expected to happen in hospitals. Secondly, the presence of E. coli is used as an indicator of presumptive focal contamination of foods. In view of the large number of E. coli isolated I am surprised than an investigation for the presence of Salmonella spp. was not undertaken. As is well known, one route for transmission of salmonellx from animals to man is from the raw food to the utensils and handlers and thence to the cooked foods. There have been, and still are, outbreaks of salmonellosis in persons consuming canteen meals. Thirdly, the presence in foods of antibiotic-resistant strains of E. coli originating from animals may give rise to transmission of drug resistance from the coliforms to other more pathogenic members of the family Enterobacteriacea. Such transmission of resistance happens not only in the intestine but also in the food if conditions are suitable for growth of bacteria.l9For this reason, the uncontrolled use of clinical antibiotics, and of antibiotics related chemically to clinical antibiotics, in food and animal feeds is to be deprecated. National College of Food Technology, University of Reading, B. JARVIS. Weybridge, Surrey.

SPOONS AND DIP-SLIDES SIR,-Dr. Maskell and Professor Polak (Aug. 8, p. 309) report that gram-positive cocci did not grow on their ’Uricult’ slides bearing MacConkey agar. This was because the MacConkey medium on the slides had not been tailored to grow these organisms. Some batches of bilesalts are inhibitory to gram-positive cocci, and their use results in MacConkey medium with similar properties to those described. In my laboratory the following formula for MacConkey medium has proved satisfactorv for urine cultures:

It is essential to titrate every new batch of ox-bile to discover the amount needed in the medium. This medium enables staphylococci and fxcal streptococci to be recognised at a glance (using a hand lens). Group-B streptococci, usually contaminants from the vagina, have been grown on the medium although the colonies were admittedly very small. For some years at Winchester we have issued outfits for urine culture containing 2 Universal 1 oz. glass bottles, of which one contains a MacConkey-filled Mackey spoon. 20 Urine is collected in the empty bottle and the spoon is then dipped and returned to its own bottle. Both bottles are sent to the laboratory, where the urine is tested chemically and examined for blood-cells; if polymorphs or many bacteria are seen, a direct sensitivity plate is put up from the urine, which is read and reported only if the dip-spoon shows that there were 100,000 or more organisms per ml. when the urine was passed. The slides in the uricult kit are too wide to dip into a Universal hottle. and urine

must

therefore be collected in

18.

Ewing, W. Serotypes

H. Isolation and Identification of Escherichia coli Associated with Diarrheal Diseases. Atlanta, Georgia,

19. 20.

Jarvis, B., Morisetti, M. D. Int. Biodetn Bull. 1969, 5, 38. Mackey, J. P., Sandys, G. H. Br. med. J. 1965, ii, 1286.

1963.