PREOPERATIVE ANTIBIOTIC PROPHYLAXIS IN ACUTE APPENDICECTOMY

352 DETECTION OF ANEURYSMS BY GAMMA-CAMERA IMAGING AFTER INJECTION OF AUTOLOGOUS LABELLED PLATELETS

Fig 2-Effect of nicardipine aggregation.

and

aspirin

on

whole blood

platelet

Mean±SEM of 5 experiments. a=control; b=5 pg/ml aspirin; c=10 gg/ml nicardipme; d = 5 fig/ml aspirin and 10 fig/ml nicardipine. *p<0’05 compared with control and with aspirin and nicardipine alone.

SiR,-Dr Sinzinger and colleagues (Dec 15, p 1365) recommend that abdominal gamma-camera imaging with background subtraction should be done in all patients investigated by indium-111 platelet labelling to detect aortic aneurysms. Autologous lllIn-labelled platelets have been used extensively to image aneurysmsl,2 without the need for background subtraction. Although in Sinzinger’s series angiography was used to confirm the diagnosis, this investigation is unreliable since the aneurysm lumen may be compromised by thrombus and appear no wider than that of adjacent artery. No reference is made to the false negative rate in their 860 patients. We have investigated 111In-platelet uptake in 11 aneurysms (8 atherosclerotic, 3 false) in an attempt to select those likely to produce peripheral emboli. Background subtraction was not used. Mean counts over the aneurysm were 9910±2924 (SEM) compared with 5193:t 1164 over the same area of normal artery (p<0 05, Wilcoxon). The platelet uptake ratio was 1-74-tO-14 and was higher for atherosclerotic (mean 1-81) than for false aneurysms (mean 1-55).

v/v). Samples were then incubated with labetalol, nicardipine, or their vehicles (controls) for 25 mm at 37°C. Aspirin or its vehicle was then added and incubation continued for a further 5 mm. The concentrations of all three drugs were known from prior assessment to have little effect on aggregation when lI used alone in all subjects studied. Whole blood aggregation was carried out with the Clay Adams ’Ultra Flo 100’ whole blood platelet counter, platelet counts bemg measured 1, 2, 3, and 5 min after addmon of the aggregating agent (0-55 pglml collagen) and expressed as a percentage of the count at time zero. At concentrations of labetalol and aspirin which on their own had little effect on platelet aggregation, a combination of both drugs resulted in a significantly greater inhibition of platelet aggregation (fig 1). Similar findings were seen with nicardipine plus aspirin (fig 2). This synergism may be due to sequential inhibition of the enzymes involved in thromboxane A2 production; adrenergic and calcium-channel-blocking agents can inhibit phospholipase A2 while aspirin irreversibly inhibits cyclo-oxygenase. The concentrations of labetalol and nicardipine were low but it is difficult to correlate these with in-vivo concentrations since such drugs accumulate within platelets in vivo.7 These findings suggest that a combination of low-dose aspirin and an adrenergic or calcium-channel-blocking agent may be of value in the prophylaxis of vascular problems where platelet aggregation is involved in the pathogenesis, and this may represent a major advance in the treatment of vascular disease. I. A. GREER J. J. WALKER A. A. CALDER C. D. FORBES

University Departments of Medicine and

Obstetrics,

Royal Infirmary, Glasgow G31 2ER

G, Cerletti C, Bertel V Pharmacology of antiplatelet drugs and clinical trials on thrombosis prevention: a difficult link. Lancet 1982, ii: 974-77. 2. The Persantine-Aspirin Reinfarction Study Research Group. Persantine and aspirin in coronary heart disease. Circulation 1980, 62: 449-61 3 Canadian Co-operative Study Group. A randomised trial of aspirin and 1978, 299: 53-59 J sulphinpyrazone in threatened stroke. N Engl Med 4 Norwegian Multicentre Study Group. Timolol induced reduction in mortality and 1 DeGaetano

reinfarction

in

patients surviving

acute

Hjalmarson A, Elmfeldt D, Herlitz J, et al. Effect on mortality of metoprolol myocardial infarction Lancet 1981, ii 823-27.

in acute

6. Braunwald E. Mechanism of action 7

of calcium-channel-blocking agents. N EnglJ Med 1982; 307: 1618-27. Weksler BB, Gillick M, Pink J. Effect ofpropranolol on platelet function Blood 1977, 49: 185-96

8. Dale 9.

10 11

J, Landmark KH, Myhre E. The effects of nifedipine, a calcium antagonist, on platelet function Am Heart J 1983, 105: 103-05 Saniabadi AR, Lowe GDO, Barbenel JC, Forbes CD A comparison of spontaneous platelet aggregation in whole blood with platelet rich plasma: additional evidence for the role of ADP. Thromb Haemostas 1984, 51: 115-18. Blackwell GJ, Flower RJ, Russell-Smith N, Salmon JA, Thorogood PB, Vane JR Prostacyclin is produced in whole blood. Br J Pharmacol 1978; 64: 436 Saniabadi AR, Lowe GDO, Forbes CD, Prentice CRM, Barbenel JC. Platelet aggregation studies

in

luIn-labelled platelets will locate thrombus within aneurysms background subtraction (figure) but are not suitable as a diagnostic investigation. Clinical examination and B-mode ultrasound are more reliable, especially when used for population screening. without

Department of Surgery, Charing Cross Hospital Medical School, London W6 8RF

I. F. LANE K. R. POSKITT M. SINCLAIR C. N. MCCOLLUM

A, Hussey JK, Smith FW, Dendy PP, Bennett B, Douglas AS. Diagnosis of aneurysm using autologous platelets labelled with indium-111 oxine Br Med J 1981; 282: 1122 Ritchie JL, Stratton JR, Thiele B, et al Indium-111 platelet imaging for detection of platelet deposition in abdominal aneurysms and prosthetic arterial grafts Am J Cardiol 1981; 47: 882-89.

1 Feneck

aortic

2.

myocardial infarction. N Engl J Med 1981,

304: 801-07 5

image with increased platelet uptake in right groin demonstrating thrombus within false femoral aneurysm.

Gamma-camera

whole human blood Thromb Res

1983, 30: 625-32.

PREOPERATIVE ANTIBIOTIC PROPHYLAXIS IN ACUTE APPENDICECTOMY

SIR,-Metronidazole prophylaxis against wound infection after has been widely used since the 1976 report of Willis et al.1 Arnbjornsson and Mikaelsson2 have again emphasised its importance and we were impressed that the data provided were based on a relevant definition of a wound infection. Bates et al3 cast doubt on the value of metronidazole prophylaxis in appendicectomy because he found that 60% of wound mfecnons developed after patients had left hospital, and the overall infection rate was similar to that in untreated controls. Ljungquist and Lund’ define a wound infection after a "clean operation" as the presence of

appendicectomy

353

recoverable pus in the wound. Ifthis sensitive definition is applied to

appendicectomy then high and rather irrelevant rates of

became alert and said that the nausea had passed. He denied a history of heart disease, diabetes, or allergy. I told him that he had had a vasovagal syncopal episode and suggested that he consult a doctor in Seattle. In the bustle of the last 30 minutes of the flight I lost track of my "patient" and we were ready to land when I made a final effort to see him, but to no avail. I could not tell if the feeling I then had was entirely the excitement of coming home, or a mixture of that and anxiety. Had it been a vasovagal reaction or had I missed a heart attack or even anaphylaxis? As we were disembarking I asked after the man and was told that he had been one of the first off, running as he went, shouting thanks, and adding that he had no intention of seeing a doctor. "Another non-compliant, ungrateful, so and so," I mumbled, greatly relieved. Airlines should justify their carriage of oxygen. Is it an anachronism or do they have evidence that the benefit outweighs the risk? I also suggest that airlines should carry stethoscopes and blood pressure cuffs. This simple equipment might avert many an unnecessary "emergency" landing, preventing inconvenience to passengers and expense to carriers (and sparing physicians embarrassment 2). I would have been greatly distressed to have been responsible for our plane making a landing in the Aleutian Islands for an erroneous diagnosis of heart attack or anaphylaxis. Doctors cannot do anything "stupid" with a blood pressure cuff and stethoscope. Can one say the same for an airline with oxygen? soon

infection

may be recorded. We have prospectively studied 98 patients undergoing appendicectomy. They all received metronidazole by suppository with their premedication and for 48 h postoperatively. Careful postoperative follow-up was done for 3-5 weeks. 2 patients had significant wound problems; staphylococcus was cultured from both. 1 patient was readmitted for a week; he required antibiotics and regular dressings. Another man needed outpatient dressings for 3 weeks. Neither patient had a second operation, so neither were infected according to Arnbjornsson and Mikaelsson’s definition. A further 13 patients noticed a discharge of pus from their wounds from which we grew an organism. 5 patients had a similar discharge which had dried up when they visited us. These last 18 "infections" persisted for 4 days at most, required no treatment, and usually occurred after discharge from inpatient care. We agree that metronidazole provides excellent prophylaxis against serious wound infection after appendicectomy but feel that the definition used by Arbjornsson and Mikaelsson was too insensitive. A widely acceptable definition of a wound infection after a "dirty operation" is needed. A. G. MUIRHEAD I. MACDONALD A. STANFIELD G. GILLESPIE

Department of Surgery, Victoria

Infirmary, Glasgow G42

University Health Services, University, Cambridge, Massachusetts 02138, USA Harvard

1. Willis AT, Ferguson IR, Jones PH, et al. Metronidazole in prevention and treatment of bacteroides infections after appendicectomy. Br Med J 1976; i: 318-21. 2. Arnbjornsson E, Mikaelsson C. Importance of preoperative antibiotic prophylaxis for patients undergoing acute appendicectomy. Lancer 1984; ii: 1279 3. Bates T, Touquet VLR, Tutton MK, Mahmond SE, Reuther JWA Prophylactic metronidazole in appendicetomy: a controlled trial. Br J Surg 1980; 67: 547-50. 4. Ljungquist U, Lund MD wound sepsis after clean operations Lancet 1964; i:

HOWARD S. RUBENSTEIN

FJ, Harding RM. Medical emergencies in the air I: Incidence and legal aspects. Br Med J 1983; 286: 1131-32. Steinweg KK. Shared values JAMA 1984; 252: 3017.

1. Mills 2.

MEDICAL EMERGENCIES IN THE AIR

1095-97.

SIR,—Your Jan 5 editorial (p 28) discusses medical emergencies in STETHOSCOPES ON AIRCRAFT

SIR,—Your Jan 5 editorial emphasised that most "emergencies" passenger flights are trivial syncopal episodes.You also questioned whether doctors on board would necessarily be skilled in emergency techniques and asked "How does the foreign carrier know that a doctor is not going to do anything stupid with the medicines provided?" However, you neglected at least two important points, as the following incident emphasises. In May, 1984, on a flight from Tokyo to Seattle and somewhere between the Bering Sea and the Gulf of Alaska, I was asked to see a young man who had just passed out. On board were at least twenty other doctors, returning home from a visit by allergists and clinical immunologists to the People’s Republic of China. The young man was sitting in the aisle. Having complained of nausea he had taken an antinauseant, collapsed, and then, like a zombie, sat upright. His skin was an alarming green but it was warm, there was no rash, his pulse was strong and regular at about 70/min, and his breathing was regular and easy. Although he was unresponsive to questions, I got him to lie flat. I had just asked the flight attendant for a stethoscope and a blood-pressure cuff, when one of my colleagues whispered "anaphylactic shock", as you might expect from an allergist. on

However, there

was

no

evidence for this, and the

man

had

apparently felt unwell before he took the pill. To my surprise the flight attendant told me that airlines did not generally carry stethoscopes or cuffs. They did, however, have oxygen, and she wondered if that would do. I said "no", wondering if she thought that oxygen was the panacea for all illnesses in the air. I thought of all those demonstrations of the use of oxygen-enriched air for delivery by mask which airline regulations insist on and of the tanks of pure oxygen for the crew. How often is oxygen used for its express purpose (in the event of cabin decompression)? I thought also of the American astronauts who burned to death when a spark of electricity met oxygen in their space capsule and wondered how many people who did not need oxygen have vomited into their oxygen masks and then aspirated. We got the man to lie on his side across spare seats at the rear of the aeroplane, and I agreed to check on him every 15 minutes or so. He

passenger aircraft. A doctor who is a passenger when there is an inemergency would, I assume, automatically want to use every skill he or she has and would worry about the legal aspect some time after the emergency. A first-aid kit is always reassuring, as anyone who has attended a road-traffic accident will immediately recognise. Most doctors would like to have a stethoscope available, not just as a symbol of authority, but because in many emergencies the use of this simple item of equipment will give a clue as to exactly what the problem is. I suggest that all passenger aircraft should carry a stethoscope. I have on a few occasions been involved in such emergencies and know that when the illness is more than trivial the doctor may well be asked by the captain of the aircraft whether the plane should be diverted. A diversion may inconvenience well over three hundred passengers, and is a costly and potentially hazardous undertaking. Every possible simple aid should be available to anyone who may be asked about the need for such a move.

flight medical

Royal Infirmary, Glasgow G31 2ER

R. SCOTT

SIR,-Working in a hospital on the perimeter of London Airport (Heathrow) we see a steady stream of illnesses which have developed in flight. A point not made in your Jan 5 editorial is that the major manifestation of the illness may not occur until after disembarkation. We have seen several patients with thromboembolism presenting in this way, with a near-fatal outcome in

one case.

39-year-old woman collapsed on leaving a 27 h flight from Kuala Lumpur, Malaysia. She had been previously well apart from symptoms suggestive of mild gastroenteritis immediately before and during the flight; she had no risk factors for coronary artery disease and was not taking oral contraceptives. She required resuscitation in A

the ambulance. On arrival in casualty she was unconscious and shortly afterwards arrested. After intensive cardiopulmonary resuscitation she improved, though she was still acidotic; 48 h later she was clinically normal. Subsequent electrocardiographs showed subendocardial ischaemia and cardiac enzymes were elevated. 6 days later a ventilation-perfusion scan at St Peter’s Hospital,