481

consistently shown in classic and not in more likely (though difficult to prove without an artifactual stimulus) that primary spreading neuronal depression (Leao) is the initiating event, and that where present,

Promotion of thrombin activity by thrombolytic therapy without simultaneous

vascular ischaemia and infarction are the consequences of a secondary disorder, probably in the microcirculation.4,5 The neurogenic theory6 receives additional support from Dr Mortimer and colleagues (Jan 13, p 75), who show a sharp division between controls and children with migraine in respect of flash and pattern evoked amplitudes of over 2 [tV in visual evoked responses. Athough we must be wary of inference derived from artifactual stimuli and animal models in human pathophysiology, these observations plainly point to a difference in primary neuronal physiology in the aetiology of migraine.

SIR,-Early thrombolytic therapy has become the treatment of choice for acute myocardial infarction, mainly because of its beneficial effect on mortality, established in large clinical trials. Adjunctive measures, however, and in particular anticoagulation, are still a matter of debate. In the TAMI 3 triall comparing alteplase with alteplase plus heparin, heparin did not improve the coronary patency rate at 90 minutes. With all patients qualifying for heparin at this time, however, the issue of whether anticoagulation protects from reocclusions was not addressed. Experimental data in canine models indicate a striking acceleration of native tissue type plasminogen activator induced thrombolysis by heparin.2 We have quantified the independent affect of alteplase and heparin on thrombin activity in the early hours of myocardial infarction in 50 consecutive patients.3 The principal aim of the study was to evaluate fibrinopeptide A (FPA) plasma concentration as a reocclusion marker. The analysis of FPA allows a very sensitive survey of thrombin activity or fibrin generation in vivo.4,s FPA samples were obtained on admission (FPA 1); 90 min after starting a 3-h infusion of 100 mg alteplase but before heparin administration (FPA 2); 120 min and 30 min after initiation of alteplase and heparin, respectively (FPA 3); 30 min after completion

blood flow has been common

migraine.

It is

Department of Neurology and Headache Clinic, Hull Royal Infirmary,

J. M. S. PEARCE

Hull HU3 2JZ, UK 1. Pearce JMS.

Thomas,

Migraine, mechanisms and management. Springfield, Illinois: Charles 1969.

2. Wolff HG. Headache and other head pains. New York: Oxford University Press, 1963: 227-386. 3. Gowers WR. A manual of diseases of the nervous system. Vol 2. London: Churchill, 1888: 788. 4. Lauritzen M. Regional cerebral blood flow during spreading depression in the rat brain: increased reactive hyperaemia in low-flow states. Acta Neurol Scand 1987; 75: 1-8. 5. Pearce JMS. Is migraine explained by Leao’s spreading depression? Lancet 1985; ii: 763-66. 6. Pearce JMS. Migraine: a cerebral disorder. Lancet 1984; ii: 86-89.

anticoagulation

Searching publication data bases SIR,-Your Jan 6 editorial on acupuncture implies that a quick search in ’Medline CD-ROM’ from 1987 to date did not reveal any meta-analyses on that topic, not even the three Dutch publications you were able to mention. I would like to make some comments about information retrieval, using your search as an example. It is important to use more than one data base in biomedical searches. There are several general and hundreds of specialised data bases available’ (in print, on line, or on disc) and the results from similar data bases can, in my experience, vary greatly, sometimes too much. Reasons for this include differences in indexing policy, literature coverage, and updating time. I found one acupuncture meta-analysis not picked up in your search in ’Embase’2 and one in ’Scisearch’,3 demonstrating that searching multiple data bases can significantly expand information horizons.’ The three Dutch articles were not indexed in Medline CD-ROM or in Scisearch, and Embase was the only one of the three most important biomedical data bases to cover the Dutch journal that published the three articles. Paul Otlet and Henry Lafontaine may have been overoptimistic at the beginning of this century with their ideas about being able to control the complete world output of publications; their attempt at complete bibliographic coverage resulted in a mountain of 15 million catalogue cards. However, this is the age of automation and indexing bodies such as the US National Library of Medicine and the Institute for Scientific Information, Philadelphia, should try harder to expand their coverage. Why is language such a barrier for the ISI; why are not books indexed in-depth any more; and why are new journals not indexed immediately? Better indexing and coverage on the one hand and better searching on the other should improve the quality of medical documentary information. Prof DrJ Mulder

Library,

Academic Hospital Leiden, 2300 RC Leiden, Netherlands

J. W. SCHOONES

1. Anon. Online databases in the medical and life sciences. New York Cuadra/Elsevier, 1987. 2. Patel MS. An introduction to meta-analysis. Health Policy 1989; 11: 79-85. 3 Kubiena G. Considerations on the concept of placebo in acupuncture: reflections on the usefulness, ethical justification, standardization and differentiated application of placebo in acupuncture. Wien Klin Wochenschr 1989; 101: 362-67. 4 Darling L, ed. Handbook of medical library practice: vol I, 4th ed. Chicago: Medical

Library Association, 1982· 209.

Fibrinopeptide A concentrations in acute myocardial infarction and in controls before and after alteplase (rtPA) and heparin. FPA1-6,

see

text.

Searching publication data bases.

481 consistently shown in classic and not in more likely (though difficult to prove without an artifactual stimulus) that primary spreading neuronal...
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