Subarachnoid haemorrhage J. VAN GIJN of
managing patients with subarachnoid haemorrhage (SAH) is deceptively simple: make the diagnosis, locate the aneurysm, and put a clip on it. Yet half the patients still die, and half the survivors remain severely disabled,l the course of the disease being beset by complications and diagnostic pitfalls. The
Diagnosis Clinical features The cardinal feature is sudden headache, often described as like a blow on the head or an explosion inside; the pain is unusually severe, and diffuse rather than local. Typically the patient is over 40, since aneurysms take years to develop; it is a myth that they are mostly congenital. Sexual intercourse or weight-lifting are well-recognised but infrequent precipitating factors. Close questioning of patients with definite SAH suggests that premonitory headaches occurred in the preceding weeks in 25-50%, and that these were overlooked as often by the patient as by the doctors It is exceedingly difficult to think of such a rare disease (an average general practitioner will see one patient with SAH every 5 years) when less ominous headaches are so much more common. The most important safeguard is to inquire about the mode of onset in any patient with severe headache. Loss of consciousness occurs in only half the patients and is often momentary.33 The main difficulty is that SAH cannot be ruled out in a patient with no signs and no symptoms other than sudden and persistent headache. Neck stiffness takes hours to develop, contrary to standard medical school teaching. Sudden manifestations of common varieties of headache such as migraine or tension headache may outnumber SAH, but not by very much. A preliminary study among general practitioners in the Netherlands suggests that the proportion of SAH among patients with sudden headache is about 25 %.
Computed tomography (CT scanning) is the first-line investigation for patients with suspected SAH. Sensitivity depends not only on the interval after the event, but also on the quality of the equipment and the radiologist; under optimum conditions evidence of blood can be detected in 95 % of cases within a day vs only 50% after a week. The site of the ruptured aneurysm can often be inferred from the pattern of bleeding, especially if there is an associated haematoma.6 This information is useful for guiding subsequent angiography, and it can be vital if more than one aneurysm is detected. In some cases an intraparenchymal haematoma is unexpectedly found in the basal ganglia, the cerebral white matter, or the cerebellum, distant from the usual sites of aneurysms; such a finding would suggest another source of haemorrhage such as an arteriovenous malformation, rupture of a small perforating artery, or
amyloid angiopathy (see Caplan, p 656). CLINICAL SPECTRUM OF SUBARACHNOID HAEMORRHAGE
Referral bias in subarachnoid
specialised (A) they do not consult a general practitioner, (B) the diagnosis is missed, (C) they die before reaching hospital, or (D) it is assumed that no treatment is Patients may not reach
Referral bias Selection bias operates in various ways other than by patients not consulting their general practitioner or by doctors failing to make the diagnosis in mild cases (see figure). At least 25% of patients die within 24 h,4 sometimes before reaching hospital. In addition, general physicians or even neurologists without ready access to specialised skills may not refer some patients to the appropriate centre because their condition is thought to be hopeless. The habit of classifying patients with a depressed level of consciousness after SAH only by a grading system without taking account of the underlying condition is to be deplored. For example, haematoma, acute hydrocephalus, and metabolic disorders may not be recognised and patients may be denied the very intervention they need.
Lumbar puncture should be reserved for patients in whom no blood is detected by CT scanning. It is essential to distinguish between a traumatic tap and a true haemorrhage. A widely held but erroneous belief is that this distinction can be reliably made by collecting the cerebrospinal fluid (CSF) in three consecutive test tubes and by comparing the number of red cells.6 The only sound method is to centrifuge the CSF and to examine the supernatant for xanthochromia. The CSF cannot be declared normal unless spectrophotometry has been used. The yellow colour is that of pigments released from disintegrating red cells in the ADDRESS: University Department of Neurology, PO Box 85500, 3508 GA Utrecht, the Netherlands (Prof J. van Gijn, MD)
CSF; they can invariably be found between 12 h and 2 weeks after SAH.7 Lumbar puncture should therefore be deferred until at least 12 h after the onset of the headache. The only legitimate exception is the rare patient with such an incomplete history that meningitis cannot be ruled out. If lumbar puncture is done too soon and the CSF is blood-stained, the patient cannot escape an angiogram and may suffer unnecessary anxiety even when this is normal.
Non-haemorrhagic thunderclap headaches If both the CT scan and the CSF are normal, the episode should be attributed to an unusually explosive bout of "ordinary" headache and not to SAH. A 3-year follow-up study of 71 such patients found identical recurrences in 12, but again without evidence of SAH, whereas almost half went on to have regular episodes of tension headache or migraine.8 Thus the risk of angiography is not justified in patients with thunderclap headache, unless the pain is accompanied by an oculomotor palsy or other relevant signs.
Angiography The timing of angiography depends on the planned date of operation (see below). This procedure will show an aneurysm in about 85%. What about the remaining 15%? They should not be regarded as a single category.Apart from
inadvertently included in some series, patients with a normal angiogram should be distinguished according to whether or not the pattern of haemorrhage on CT suggests an aneurysmal origin. If so, rebleeding and other complications still loom ahead.9 The search for the aneurysm should then be pursued vigorously, with repeated angiography or even
exploratory craniotomy.99 Non-aneurysmal SAH 10% of all patients with SAH (and two-thirds of those with a normal angiogram) show a pattern of bleeding on CT that is very different from that associated with most arterial aneurysms.10 First, the centre of the extravasated blood is not in the region of the circle of Willis but around the midbrain, most often in the interpeduncular fossa. Second, the haemorrhage is very localised, without extension to the brain parenchyma, the ventricular system, or even to the anterior and lateral cisterns.lO,l1 The clinical course is equally dissimilar to that of patients with ruptured aneurysms: rebleeding or ischaemia does not occur, and the long-term outcome is invariably excellent.9 The good prognosis is the very reason that the vessel defect in this so-called perimesencephalic haemorrhage has not yet been
be omitted, because in about 1 in 20 Angiography cases a basilar artery aneurysm is found," but it is unnecessary to repeat a negative study. cannot
Nursing care Continuous observation and an intravenous access are essential. The headache can sometimes be alleviated with mild analgesics such as paracetamol or most cases will respond to codeine. dextropropoxyphene; should be avoided. Distressing anxiety can be Aspirin alleviated with short-acting benzodiazepines. Stools should be kept soft with oral laxatives and also by an adequate intake of fluids other than milk.
Prevention of delayed cerebral ischaemia
Up to 25 % of patients with a ruptured aneurysm go on to have cerebral ischaemia, mainly between day 5 and day 14 after the initial bleed. The pathogenesis is complex, and our understanding of events has been clouded by simplistic notions of "vasospasm" or "clots around vessels". Narrowing of the arteries at the base of the brain is perhaps a necessary but certainly not a sufficient factor. The total amount of subarachnoid blood is a potent risk factor but its distribution does not predict the site of ischaemia," so the blame shifts from the blood itself to the impact of the initial haemorrhage. The calcium antagonist nimodipine, in a dose of 60 mg every 4 h by mouth or nasogastric tube, reduces the incidence of cerebral ischaemia and poor outcome by about
third,13 probably by protecting ischaemic nerve cells against the damaging influx of calcium. Hypertension should usually be left untreated, because it is probably a compensatory reaction to maintain cerebral perfusion. Plasma volume should not be allowed to fall; hyponatraemia is caused by sodium depletion and not, as formerly believed, by dilution as a result of inappropriate secretion of antidiuretic hormone. 14 Fluids should therefore be replaced one
and not restricted. The basic intake should be at least 3 litres day, with intravenous fluids to supplement oral intake; compensation will be necessary for fever or a negative fluid balance. per
Prevention of rebleeding At least 10% of all patients with SAH have another bleed within hours of the initial haemorrhage.11 Without intervention, the risk of rebleeding in the remaining patients is at least 30% over the subsequent 4 weeks. The immediate mortality of rebleeding is 50%. Apart from the first day there is no peak time, and so far it has not been possible to identify patients at special risk. 15 Surgical clipping of the aneurysm is the most effective method of treatment, and it seems logical to carry out the operation as early as possible. In the past this approach was precluded by a greatly increased risk of postoperative brain ischaemia, but with improved techniques of microsurgery and anaesthesia the policy of operating early has come back into fashion. Nevertheless, the benefits of operating within 3 days rather than after 11-14 days have not been convincingly shown in terms of overall outcome, neither in a large but non-randomised comparison,16 nor in a randomised but small trial. 17 What seemed to emerge was the disadvantage of operating in the intermediate period.16 Medical prevention of rebleeding, by means of antifibrinolytic drugs, has theoretical attractions if operation is deferred. In the largest randomised trial, conducted a decade ago, tranexamic acid drastically reduced rebleeding (by two-thirds) but again at the cost of an increased rate of cerebral infarction; overall outcome was similar in treated and untreated patients.3 Now that cerebral ischaemia can be averted to some extent by nimopidine and by adequate maintenance of plasma volume, the possible contribution of antifibrinolytic agents needs to be reassessed.
Management of complications Any episode of clinical deterioration should be rigorously investigated. A sudden decrease in the level of consciousness should not be attributed automatically to rebleeding, since serial CT scanning confirms renewed haemorrhage in only two
in three cases, and various other
may emerge in
deterioration of consciousness can result not only from ischaemia but also from hydrocephalus or metabolic disorders. Cerebral ischaemia Unlike brain infarcts that
disease, cerebral ischaemia after SAH is usually of insidious and is a multifocal or diffuse process. Accordingly, a gradual decrease in the level of consciousness occurs in three-quarters of cases, together with focal signs in half.19 Treatment of cerebral ischaemia is via rapid improvement of cerebral perfusion by expansion of the plasma volume, induced hypertension, or both. The efficacy of these regimens has not been properly studied but is suggested by subsequent reversal of deficits in many cases. Volume expansion (with a solution of macromolecules) should be monitored by means of a central venous catheter (pressure between 8 and 12 mm Hg) or a flow-guided pulmonary artery catheter (pulmonary artery wedge pressure between 14 and 18 mm Hg). If no clinical improvement follows and the aneurysm has been previously clipped, the arterial pressure should be increased by 20-40 mm Hg with dopamine or dobutamine. Transluminal angioplasty of narrowed cerebral vessels has been carried out in only a few centres and is not without complications. onset
does not mean that all is lost. in a third of all episodes of Although apnoea ventilation results in a return of assisted rebleeding, in most cases, usually within 1 h. In spontaneous respiration the immediately fatal rebleeds (50%) brainstem reflexes are mostly lost before apnoea occurS.1S Because 50-75% of the survivors have yet another bleed,ls emergency clipping of the aneurysm seems justified in patients who regain consciousness after rebleeding.
Symptomatic hydrocephalus occurs in 15-20% of patients with SAH, mostly within the first few days. A characteristic history consists of gradual obtundation after a lucid interval of a few hours, but this is elicited in only half of such cases.2° Spontaneous improvement within 24 h can be expected in 50%, except in those with massive intraventricular haemorrhage.21 In the remaining patients, insertion of an external ventricular catheter results in dramatic improvement within 1 or 2 days, but at the cost of a high rate of rebleeding;2021 rebleeding can be prevented by clipping the aneurysm at the same time. Ventriculitis may also complicate ventricular drainage.21 If the presumed level of obstruction is in the subarachnoid space rather than in the ventricular system, lumbar punctures can obviate the need for a shunt in about half the cases.2Z
Although further improvements in the medical and surgical management of SAH can be expected, the most urgent task of the medical community is to extend the available treatment options to more than a fraction of all patients with the disease (see figure). In the past, a bugle-call has often sounded for general practitioners to refer all their patients with sudden and persistent headache and so to improve the chances of early intervention. Although this strategy may certainly help, many specialists should also
alter their policies. It is no longer defensible to care for patients with SAH in hospitals without neurosurgeons or neuroradiologists. Moreover, because not all complications are amenable to surgical treatment, neurosurgeons should team up with neurologists and neuroanaesthetists to provide optimum therapy for all aspects of this complex disorder. Prof Hans van Crevel inspired much of the work cited in this review. During the preparation of the article I enjoyed the hospitality of the University Department of Clinical Neurosciences in Edinburgh. Valuable comments were offered by Dr G. J. Hankey, Ms 1. McDowell, Dr G. J. E. Rinkel (Utrecht), Prof C. A. F. Tulleken (neurosurgeon and team-mate in Utrecht), Prof M. Vermeulen (Amsterdam), and Prof C. P. Warlow.
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