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Vasodilators During Cerebral Aneurysm Surgery 775 Review Article Vasodilators during cerebral aneurysm Kazuo Abe MD surgery The objective of this review is to review the anaesthetic im- the drugs of choice for induced hypotension. Prostaglandin E t, plications of vasoactive compounds particularly with regard to nicardipine and nitroglycerin have the advantage that they do the cerebral circulation and their clinical importance for the not alter carbon dioxide reactivity. Local cerebral blood flow practicing anaesthetist. Material was selected on the basis of is increased with nitroglycerin, decreased with trimetaphan and validity and application to clinical practice and animal studies unchanged with prostaglandin E~ Intraoperative hypertension were selected only if human studies were lacking. Hypotensive is a dangerous complication occurring during cerebral aneu- drugs have been used to induce hypotension and in the treat- rysm surgery, but its treatment in association with subarachnoid ment of intraoperative hypertension during cerebral aneurysm haemorrhage is complicated in cases of cerebral arterial va- surgery. After subarachnoid haemorrhage, cerebral blood flow sospasm because fluctuations in cerebral blood flow may be is reduced and cerebral vasoreactivity is disturbed which may exacerbated. Hypertension should be treated immediately to re- lead to brain ischaemia. Also, cerebral arterial vasospasm de- duce the risk of rebleeding and intraoperative aneurysmal rup- creases cerebral blood flow, and may lead to delayed ischaemic ture and the choice of drugs is discussed. Although the use brain damage which is a major problem after subarachnoid of induced hypotension has declined, the control of arterial haemorrhage. Recently, the use of induced hypotension has de- blood pressure with vasoactive drugs to reduce the risk of in- creased although it is still useful in patients with intraoperative traoperative cerebral aneurysm rupture is a useful technique. aneurysm rupture, giant cerebral aneurysm, fragile aneurysms Intraoperative hypertension should be treated immediately but and multiple cerebral aneurysms. In this review, a variety of the cerebral vascular effects of each vasodilator shouM be un- vasodilating agents, prostaglandin E I, sodium nitroprusside, ni- derstood before their use as hypotensive agents. troglycerin, trimetaphan, adenosine, calcium antagonists, and inhalational anaesthetics, are discussed for their clinical use- L'objectif de cet article est de revoir les implications anesth$- fulness. Sodium nitroprusside, nitroglycerin and isoflurane are siques des compos~s vasoactifs particuli~rement en rapport avec la circulation cdr$brale ainsi que leur importance clinique pour l'anesth~siste. Les agents ont ~t~ choisis sur la base de leur Key words validit~ et de leur application it la pratique clinique et des ~tudes ANAESTHETICS,VOLATILES: isoflurane; animales ont ~td choisies seulement en l'absence d~tude sur ANAESTHETICTECHNIQUES; hypotension; 17~omme. Les agents hypotenseurs ont dt~ utilis~s pour induire BLOOD PRESSURE" hypotension; de 1~ypotension et pour traiter 17~ypertensionpreop~ratoire pen- BRAIN: blood flow, carbon dioxide tension; dant la chirurgie d'andvrisme c&~brale. Apr~s une hdmorragie HORMONES: prostaglandin El sous-arachnoMienne, le d~bit sanguin cdr$brale r$duit et la va- SYMPATHETICNERVOUS SYSTEM: ganglionic blockade, somotriciM c&~brale perturb~e peuvent entrafner une isch~mie trimetaphan; c~r$brale. Ainsi, le vasospasme artdriel cdrdbral diminue le d~bit PHARMACOLOGY; adenosine, nitroglycerin, nitroprusside, sanguin cdr~bral et peut conduire it des dommages c&~braux calcium channel blockers, hydralazine, diazoxide, retardes d'isch~mie, problbme majeur aprbs une h~morragie labetalol, esmolol; sous-arachnoMienne. R~cemment, I'utilisation de 171ypotension COMPLICATIONS" intraoperafive hypertension, brain contr61~e s'est rar~fi~e bien qu'elle soit encore utile chez les ischaemia, rebleeding. patients avec une rupture peropdratoire d'an~vrisme, en cos From the Department of Anaesthesia, Osaka Police Hospital. d'an~vrisme c&$bral g~ant, d'an~vrismes fragiles et d'an- Address correspondence to: Dr.Kazuo Abe, Department of ~vrismes cdr~braux multiples. Dans cet article, une varidtd de Anaesthesia, Osaka Police Hospital, 10-31 Kitayama, Tennouji, vasodilatateurs, le prostaglandine E l, le nitroprussiate de so- Osaka 543, Japan. dium, la nitroglycdrine, le trimdtaphan, l'ad~nosine, les anta- Accepted for publication 17th April, 1993. gonistes calciques et les agents d'inhalation son discut~s pour CAN J ANAESTH 1993 / 40: 8 / pp 775-90 776 CANADIAN JOURNAL OF ANAESTHESIA leur utilit~ cfinique. Le nitroprussiate de sodium, la nitrogly- velop abnormal cerebrovascular reactivity and impaired cerine et l'isoflurane sont les agents de choix pour l~ypotension autoregulation 2,3 and they may be more susceptible to contrrlke. La prostaglandine E t, la nicardipine et la nitrogly- severe flow reductions during hypotension than normal cerine ont ravantage de ne pas alt~rer la rOactivit~ au dioxyde individuals, 4 resulting in global and or focal ischaemia de carbone. Le d~bit sanguin c~r~bral local est augment~ avec of the brain. 5 During the first two weeks after SAH, la nitroglycerine, diminu~ avec le trim~taphan et inchang~ avec several events may make heavy demands on the capacity la prostaglandine E I. L'hypertension perop~ratoire est une com- of the cerebral vasculature to react adequately. Cerebral plication dangereuse aux cours d'une chirurgie d'an~vrisme arterial vasospasm and rebleeding are major problems cOr~bral, mais son traitement lors d'hdmorragie sous- and cerebral aneurysm surgery is often performed within arachnoMienne se complique dans les cas de vasospasme ar- the same period. Another problem during general anaes- t~riel c~r~bral parce que les fluctuations du d~bit sanguin thesia for aneurysm clipping is intraoperative hyperten- c~r~bral peuvent s'exacerber. L'hypertension devrait 6tre traitke sion. Intraoperative hypertension may increase the risk imm~diatement pour r~duire le risque de resaignement et de of rebleeding and intraoperative aneurysm rupture before rupture perop~ratoire de l'anOvrisme. Le choix des agents est its exposure so that intraoperative blood pressure should discut~. Bien que l'utilisation de l'hypotension contrOl~e est be well controlled. moins fr~quente, le contrrle de la pression art~rielle avec des agents vasoactifs dans le but de r~duire le risque de rupture Pathophysiology perop~ratoire d'anOvrisme c~r~bral est une technique courante. L'hypertension perop~ratoire devrait ~tre traitOe imm~diatement Subarachnoid haemorrhage mais les effets vasculaires c~rObraux de chaque vasodilatateurs Ten percent of all strokes result from subarachnoid haem- devraient 6tre compris avant qu'ils soient utilis~s comme agents orrhage (SAH) which is caused most often by the sudden hypotenseurs. rupture of an intracranial saccular aneurysm. Subarach- noid haemorrhage chiefly afflicts patients between 40 and 60 yr of age and women are affected more often than Contents men. Rupture of an intracranial arterial aneurysm pro- Introduction duces severe focal and generalized disturbances in brain Pathophysiology function (Figure 1). Depending on the surgical risk, pa- - Subarachnoid haemorrhage tients may present a broad spectrum of clinical conditions, - Cerebral vasospasm ranging from non-ruptured aneurysm (grade 0) to deep Cerebral haemodynamics coma (Grade V). 6 Delayed cerebral ischaemia is the - Carbon dioxide reactivity major cause of poor outcome or death after SAH. The - Autoregulation risk of delayed ischaemia and cerebral infarction after - Cerebral blood flow SAH is dependent on many factors, the most important - Cerebral arterial blood flow velocity of which are the amount of blood in the basal cisterns, Induced hypotension the presence of intracranial haematoma and the patient's Hypotensive drugs clinical condition. 7 Subarachnoid haemorrhage from rup- - Prostaglandin El ture of an intracranial arterial aneurysm produces severe - Sodium nitroprusside focal and generalized disturbances in brain function. Rup- - Adenosine ture of a cerebral aneurysm with subsequent arterial - Nitroglycerin bleeding may cause dramatic changes in intracranial pres- - Trimetaphan sure (ICP) 8 (Figure 2). In severe haemorrhage, cerebral - Calcium channel blockers perfusion pressure may decrease to low levels with a con- - Isoflurane comitant decrease in cerebral blood flow. Severely ele- - Other vasodilators vated ICP may also lead to brain herniation. Following Clinical implications SAH, dilated ventricles can be seen with computerized tomographic (CT) and scanning at admission can be used During the clipping of cerebral arterial aneurysms, in- to classify the severity of haematoma. Computerized to- duced hypotension is often used to reduce the aneurysmal mographic scanning is valuable in identifying the patient's wall tension to minimize the risk of premature rupture, l risk of brain ischaemia after SAH. 9 A primary concern with the use of hypotension has been Brain damage may be caused by a marked increase that cerebral blood flow (CBF) may decrease to critically in intracranial pressure and mechanical distortion of in- low levels, resulting in ischaemic damage to the brain. tracranial structures resulting from the sudden injection Patients with subarachnoid haemorrhage (SAH) may de- of blood into the subarachnoid space. 10 Some patients Abe: HYPOTENSION AND SAH 777 et al. ~s performed 101 quantitative bedside CBF meas- urements on 40 patients
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