Acute Intraoperative Brain Herniation During Elective Neurosurgery

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58458ournal ofNeurology, Neurosurgery, and Psychiatry 1996;61:584-590 Acute intraoperative brain herniation during J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from elective neurosurgery: pathophysiology and management considerations

Ian R Whittle, Rajaraman Viswanathan

Abstract dure and closure of the cranium may also Objectives-To describe operative proce- have contributed to the often very satis- dures, pathophysiological events, man- factory clinical outcome. agement strategies, and clinical outcomes after acute intraoperative brain hernia- (j Neurol Neurosurg Psychiatry 1996;61:584-590) tion during elective neurosurgery. Methods-Review of clinical diagnoses, operative events, postoperative CT find- Keywords: brain hemiation; intraoperative aneurysm rupture; subarachnoid haemorrhage; intraventricular ings, intracranial pressure, and arterial haemorrhage blood pressure changes and outcomes in a series of patients in whom elective neurosurgery had to be abandoned because of Profound intraoperative brain swelling and severe brain herniation. herniation through an elective craniotomy was Results-Acute intraoperative brain her- in most instances, before modern neuroanaes- niation occurred in seven patients. In thesia, related to either hypercarbia or to high each patient subarachnoid or intraven- venous pressures. Nowadays such an event is tricular haemorrhage preceded the brain uncommon and is only occasionally found herniation. The haemorrhage occurred after evacuation of a post-traumatic acute sub- after intraoperative aneurysm rupture dural haematoma.' In this situation the hernia- either before arachnoidal dissection tion is thought to be related to cerebral (three) or during clip placement (one); vasodilatation and hydrostatic brain oedema after resection of 70% of a recurrent secondary to brain decompression2 4 and to hemispheric astroblastoma; after resec- alterations in the biomechanics of the brain tion of a pineal tumour; and after a after craniotomy. Less commonly it may be stereotactic biopsy of an AIDS lesion. In related to the development of distant intracra- all patients the procedure was abandoned nial haematomata." because of loss of access to the intracra- Because profound brain swelling and hernia- nial operating site, medical measures to tion during elective neurosurgery is infre- control intracranial pressure undertaken quently reported we present seven patients, all

(intravenous thiopentone), an intraven- under the care of the senior author (IRW), in http://jnnp.bmj.com/ tricular catheter or Camino intracranial whom such complications occurred. The aims pressure monitor inserted, and CT per- are to clarify the pathophysiological mecha- formed immediately after scalp closure. nisms underlying such brain swelling and to The patients were transferred to an inten- make certain management recommendations. sive care unit for elective ventilation and Pathophysiological mechanisms are implied multimodality physiological monitoring. from observed intraoperative events, immedi- this strategy all patients recovered ate postoperative neuroimaging studies, and

Using on September 30, 2021 by guest. Protected copyright. from the acute ictus and no patient had recording of multiple systemic and neurophys- intracranial pressure > 35 mm Hg. iological variables. Management strategies Although one patient with an aneurysm were based on the principles of providing an rebled and died three days later the other optimal systemic and intracranial milieu to six patients did well considering the dra- minimise secondary brain insults. matic and apparently catastrophic nature of the open brain herniation. Department of Clinical Conclusions-There are fundamental dif- Methods Neurosciences, ferences in the pathophysiological mecha- The case records of seven patients who all Western General and developed profound brain herniation during Hospital, Edinburgh nisms, neuroradiological findings, EH4 2XU, UK outcomes between open brain herniation elective neurosurgical procedures were thor- I R Whittle occurring in post-traumatic and elective oughly reviewed. This cohort comprised about R Viswanathan neurosurgical patients. The surprisingly 0 7% of all cranial procedures performed by Correspondence to: the senior author over the time of the study. Mr I R Whittle, Department good outcomes in this series may have of Clinical Neurosciences, occurred because the intraoperative brain The clinical and surgical details, preoperative Western General Hospital, observation charts, intraoperative anaesthetic Crewe Road, Edinburgh, herniation was secondary to extra-axial EH4 2X, UK. subarachnoid or intraventricular haem- records, and postoperative intensive care unit Received 2 June 1995 orrhage rather than intraparenchymal records were analysed and all measured physi- and in final revised form ological variables were plotted on appropri- 29 January 1996 haemorrhage or acute brain oedema. Accepted 9 February 1996 Expeditious abandonment of the proce- ately scaled graphs so the time course of Acute intraoperative brain herniation during elective neurosurgery: pathophysiology and management considerations 585 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from changes in these variables could be analysed in Operative details relation to the apparently catastrophic intraop- Patients were positioned supine with the head erative event. Immediate postsurgical CT radi- rotated to one side with the contralateral ographs were compared with preoperative shoulder raised for aneurysm surgery. The studies. patient undergoing stereotactic biopsy was in the supine position. The patient undergoing pineal surgery was prone, with head slightly Clinical details extended and rotated to the right. The patient Three patients had subarachnoid haemorrhage having reoperation for brain tumour was in the from anterior communicating artery aneurysm lateral position. The Mayfield pin headrest rupture and were WFNS grade I or II preoper- was used for all patients except the stereotactic atively (surgery being performed two, seven, biopsy. Head up tilt of 150 was routine. Severe and 11 days after aneurysmal rupture). One brain herniation ocurred within minutes in patient had subarachnoid haemorrhage from a every patient. In three patients (1, 2, and 4) it posterior communicating internal carotid ocurred after pterional craniotomy (with a free artery aneurysm and was WFNS grade I pre- bone flap) and dural opening but before either operatively (surgery performed on day 1). One basal or sylvian fissure arachnoidal dissection. patient had AIDS, toxoplasma retinitis, and In these patients it was assumed to be due to intracerebral lesions unresponsive to two introperative aneurysmal rupture because of weeks of antitoxoplasma treatment. Neuro- the profuse basal arterial bleeding that accom- logically he had profound psychomotor slow- panied the herniation. In each patient the pro- ing but neither features of raised intracranial cedure was abandoned and the scalp was pressure nor focal neurological deficit. Two closed in a single layer over the herniating others had intracerebral tumours (patient 6 a brain. In one patient (4) the free bone flap was pineoblastoma and patient 7 a recurrent left left "floating" subcutaneously whereas in the temporal astroblastoma) with fixed focal neu- other two patients this was physically impossi- rological deficits despite preoperative steroid ble. In another patient (3) rupture of the therapy. Neither had impairment of concious aneurysm ocurred at the time of clip place- state or papilloedema despite hydrocephalus ment and was followed by brain swelling and (patient 6) and a large mass lesion (patient 7). herniation. However, in this patient definitive Table 1 summarised the clinical features of aneurysmal clip placement was possible by these patients. using temporary anterior cerebral artery clipping before obliteration of the surgical field by the swelling brain. The wound was closed Anaesthetic details rapidly in a single layer over the herniating In all patients endotracheal general anaesthe- brain. sia was administered by an experienced con- One patient (5), with AIDS and multiple sultant neuroanaesthetist. Premedication was intracerebral lesions, had an uneventful biopsy with 5 mg droperidol and 0O6 mg atropine. of a parietal lesion. After a second target in the Thiopentone and alcuronium were used for frontal region was biopsied arterial blood was induction and anaesthesia was maintained noted to flow from the biopsy track. It was with phenoperidine and nitrous oxide/oxygen assumed that a small cortical arteriole at the mixture (Fio, 0 3). Neither a nor adrenergic base of a sulcus was avulsed and rapidly there- http://jnnp.bmj.com/ blocking agents were given before or during after cerebral tissue herniated (like toothpaste intubation, induction, or maintanance of coming out of a tube) through the dural open- anaesthesia. Multiple physiological variables ing and burr hole site. In patient 6 brisk including arterial blood pressure (radial artery venous bleeding occurred after a 2X5 cm line), heart rate, central venous pressure, oxy- pineoblastoma had been excised and tumour gen saturation (Sao,), and end tidal CO, were bed haemostasis obtained. The onset of bleed-

continuously monitored throughout the opera- ing followed withdrawal of two microretrac- on September 30, 2021 by guest. Protected copyright. tion. All variables were stable before the acute tors from the deep parafalcine occipital intraoperative brain swelling. lobe-tentorial region. Initially it was consid-

Table 1 Clinical data in seven patients with severe intraoperative brain hernia Patient No AgelSex Diagnosis Preoperative grade Procedure Timing ofhernia 1 52/F L Post Comm A WFNS I Pterional After dural opening, aneurism craniotomy prearachnoid dissection 2 65/F Ant Comm A WFNS I Pterional After dural opening, aneurysm craniotomy prearachnoid dissection 3 39/F Ant Comm A WFNS II Pterional During clip placement aneurysm craniotomy 4 44/M Ant Comm A WFNS II Pterional After dural opening, aneurysm craniotomy prearachnoid dissection 5 41/M AIDS, cerebral GCS 15, Stereotactic After biopsy of frontal toxoplasmosis psychomotor slowing biopsy (second) lesion 6 39/F Pineoblastoma GCS 15, Occipital After near total poor upgaze craniotomy excision of tumour 7 44/M Recurrent GCS 15, Temperoparietal After 70% excision of astroblastoma dysphasia craniotomy tumour L = left; Ant Comm = anterior communicating; Post Comm = posterior communicating; GCS = Glasgow coma score; WFVNS = World Federation of Neurological Surgeons Grading. 58656Whittle, Viswanathan J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from Table 2 Physiological changes and outcome in patients with severe intraoperative brain hernia Acute changes at the time of herniation Postoperativefindings Patient Elective No HR BP ICP control Closure Pupils CT ventilation Outcome 1 60 45 140/90 200/90 Thiopentone SC PER Diffuse 11 days Expressive SAH aphasia monoparesis 2 90 85 140/80 210/100 Thiopentone SC PER Diffuse 24 hours Rebleed and EVD SAH; death IVH 3 100 90 140/80 110/90 Thiopentone BFR PER Diffuse 24 hours Excellent SAH; IVH 4 80 100 110/80 130/100 Thiopentone SC Pinpoint Diffuse 72 hours Excellent SAH 5 90 115 100/70 220/150 Thiopentone SC Small Diffuse 24 hours Death at 10 days unreactive SAH 6 68 65 110/60 - 100/60 EVD SC Pinpoint SAH and 24 hours Good IVH 7 90 100 100/70 130/100 Thiopentone BFR PER SAH and 24 hours Good IVH HR = Heart rate; BP = blood pressure; SC = scalp closure; BFR = bone flap replaced; EVD = external ventricular drain; PER = pupils equal and reactive; SAH = subarachnoid haemorrhage; IVH = intraventricular haemorrhage.

ered that a perigalenic vein had been avulsed. Figure 1 Patterns of changes in arterial blood 200 pV Patiet 1 However, the venous haemorrhage was rapidly pressure (BP) before and 150 _ f i followed by massive swelling of the occipital after acute intraoperative 1500 till' IiI II lobe through the craniotomy. In this patient brain herniation during elective neurosurgery. The 200 Patient 2 the brain swelling was so severe that the occip- arrowheads denote onset of 150sj; ital pole pia ruptured and clot flowed out of swelling. BP range is 100[gtIII 11 the brain. The scalp was closed in a single 50-200 mm Hg. The units I 200 - Patient 3 layer. It was not possible to even replace the of time intervals denoting 150 intraoperative levels are 1P free bone flap in a "floating" fashion. In five minutes and 1i50 I patient 7, during the later stages of excision of postoperatively 30 minutes. o 200 - Patient 4 a very vascular recurrent astroblastoma, pro- Changes in BP are shown in detailfor the first hour : 1500 1ll ''liii fuse bleeding from neoplastic arterioles in the after onset ofswelling. a) 50 periventricular tumour bed resulted in rapid Only patient 5 had an QL200 I Patient 5 and profound cerebral herniation. Haemo- acute hypertensive episode further tumour resection were despite receiving ° 500-lllllllI stasis and thiopentone. m 200 Patient 6 impossible because the herniating peritumor- 150 ous brain completely closed access to the surgi- l 11I1iiiiI111 iIIll cal field. The scalp was closed over a 200 -Pti 7 "floating" bone flap. In none of the seven - patients could the dura be closed and manual 1000 ff¶f4111Iil1 If compression of the scalp flap was required to 50 -1 0 1 3 5 reduce the brain hernia and enable scalp clo-

Time (h) sure. http://jnnp.bmj.com/

Figure 2 Patterns of 50 - Patient 1 postoperative mean 40 - Management intracranial pressure 30 - Immediately the brain herniation became (ICP) in thefirst six hours 20 - after acute intraoperative 10 _ apparent a bolus injection of thiopentone, fol- brain herniation during O _ lowed by intravenous infusion, was given in elective neurosurgery; ICP 50 Patient 2 every Total thiopentone dose range patient. on September 30, 2021 by guest. Protected copyright. range in 0-50 mm Hg and 40 - the units of time intervals was 1-5 g over 0 5 to two hours. There was no 30 - terms of reduc- are 30 minutes. Patients 1, I 20 - obvious immediate benefit in 3, and 4 had Camino ICP 10 _ -~= tion of the brain herniation. Hypotension was monitors and patients 2 E O _ and 6 an intraventricular E not induced in any of our patients nor was catheter. Exceptfor -1 50 - Patient 3 mannitol used. After scalp closure all the patients I and 2 mean ECa) 40 - were returned to the neuro- 30 - patients adjacent ICP remained within 0.a) normal ranges in the early 20 H radiology suite under the same anaesthetic and postoperative period. 10 _ -- a non-contrast CT was performed. Thereafter a O _ Camino intracranial pressure monitor was 50 Patient 4 placed immediately in three patients (1, 3, and 40 - cJ 4) and a ventricular catheter inserted in two 30 - 20 H patients (2 and 6). All patients were electively 10 _ ventilated and medical measures or ventricular O _ drainage was employed to maintain intracra- 50 - Patient 6 nial pressure within normal limits. Mechanical 40 - to be for 11 in 30 - ventilation had continued days 20 - one patient (1) because of pulmonary compli- 10 H cations; the other patients were extubated and 0 _ I 0 1 2 3 4 5 6 returned to the neurosurgical ward within Time (h) three days. Acute intraoperative brain herniation during elective neurosurgery: pathophysiology and management considerations 587 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from Figure 3 Matched axial preoperative (right) and postoperative (left) CT of 4 IN four of the seven patients (1 = A; 2 B; 6 = C; 7 = D). The common features are extensive basal subarachnoid or intraventricular haemorrhage (C, D) and ventricular dilatation. Although both patient 1 andpatient 2 had preoperative hydrocephalus both were in good WFNS grade (A, B). The pineal lesion (C) and astroblastoma (D) are obvious in the preoperative scans (arrows). A

15 http://jnnp.bmj.com/ on September 30, 2021 by guest. Protected copyright.

LI 588 Whittle, Viswanathan J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from Results every patient the intraoperative event was sud- Table 2 and figs 1 and 2 show the immediate den, with the brain hemiating within minutes effects of the acute brain hemiation on the of an observed or occult deep intracranial physiological variables monitored. There was a haemorrhage, and the brain having to be man- transient rise in the blood pressure in five of ually confined to effect scalp closure. Both the seven patients and in these patients the cerebral vasodilatation and brain oedema have blood pressure returned to the pre-event val- been proposed as possible mechanisms for ues within 15-30 minutes (fig 1). Alterations rapid development of brain swelling after cran- in the heart rate were also transient and iocerebral trauma.3 4 7 28 Cerebral hyperaemia involved minor fluctuations in rate. There was and brain oedema are not mutually exclusive an equal incidence of mild tachycardia and and vascular engorgement that is severe and bradycardia. Intracranial pressure findings (fig persistent may result in widespread oedema 2) disclosed a maximal pressure of 35 mm Hg formation.7 8 In these cases of rapid brain her- in one patient (2), whereas in the others the niation during elective neurosurgery we pro- intracranial pressure was either normal or only pose that combinations of acute intracranial marginally raised (range 8-30 mm Hg). After hypertention caused by subarachnoid or intra- removal of the surgical drapes none of the ventricular haemorrhage together with hyper- patients exhibited pupillary dilatation. Three aemia, rather than brain oedema, were the patients (4, 5, and 6) had equal but unreactive primary causes of hemiation. pupils and in the remainder the pupillary reac- The proposed cerebral hyperaemia and tion to light was normal. acute "pressure" wave intracranial pressure The common findings on immediate post- changes in these patients may have occurred surgery CT were subarachnoid or intraventric- directly as a result of either the acute sub- ular haemorrhage with some degree of arachnoid haemorrhage or intraventricular hydrocephalus. There was minimal intra- haemorrhage bolus into the CSF space or parenchymal haematoma, midline shift, or indirectly by the subarachnoid haemorrhage intraparenchymal low density (fig 3). Diffuse activating various neurovascular reflex mecha- basal subarachnoid haemorrhage was found in nisms.9 1' The first hypothesis would invoke three patients (1, 4, and 5), whereas subarach- the subarachnoid haemorrhage or intraventric- noid haemorrhage and intraventricular haem- ular haemorrhage being envisaged as a bolus orrhage were found in four patients (2, 3, 6, injection into the CSF. This would be and 7). In several patients there was a sugges- analagous to performing an acute experimen- tion of either early hydrocephalus (temporal tal WITH, the peak and duration of the horn dilatation) or longer standing hydro- intracranial pressure wave being related to the cephalus (fig 3). Paradoxically in patient 7 the blood volume insult into the CSF, the rate of midline shift was less than preoperatively (fig bleeding, and the underlying lumped cran- 3). iospinal compliance at the time of the sub- The overall outcomes were remarkably arachnoid or intraventricular haemorrhage.'2 good considering the dramatic and apparently Acute intracranial pressure "pressure waves" catastrophic nature of both the open brain her- and increases in the cerebral blood volume niation and the volume of the acute bleeding. with or without significant changes in the Of the four patients with aneurysms, two (1 mean systemic arterial pressure have also been

and 2) had hemipareses postoperatively; the described in several experimental paradigms http://jnnp.bmj.com/ other two had no lateralising neurological that involve electrical stimulation of the deficit. One patient (2) rebled from her medullary and pontine nucli.'3 '5 It is postu- aneurysm and died three days after the intra- lated that excitation of these regions, perhaps operative herniation. One (4) underwent later due to brainstem microcirculatory distur- definitive aneurysmal clipping and excision bances caused by the subarachnoid haemor- before retuming to his previous employment. rhage, results in neurogenic vasodilation and Patient 3 also made a complete recovery hyperaemia.16 This postulate is consistent with before retuming to work. The fourth patient the increases in cerebral blood flow of 46% on September 30, 2021 by guest. Protected copyright. (1) required duraplasty and cranioplasty at the recorded after intraoperative aneurysmal rup- time of her definitive aneurysm surgery and is ture in humans despite a decrease, albeit non- moderately disabled. The patient with AIDS significant, in mean arterial pressure.22 The recovered to his preoperative neurological relative "damping" of any systemic vascular state but died 10 days later from his immun- hypertension and absence of any consistent odeficiency disorder. The woman with the change in mean arterial blood pressure in pineoblastoma had a visual field defect that these patients may be partly attributable to the resolved over two years, and was able to effects of general anaesthesia.'3 17 The gener- resume her previous employment. The patient alised nature of the subarachnoid haemor- with the astroblastoma, which had trans- rhage and absence of midline shift, deep formed to a glioblastoma, underwent further intracerebral haematoma, and either focal or excision of his tumour, duraplasty, and cranio- generalised brain oedema on the postoperative plasty but died three months later. CT (performed within 60 minutes of the ictus), the short lived course of raised intracranial pressure, and the apparent benefit of bar- Discussion biturates lend support to these hypotheses. The most important clinical feature in these The changes in the blood pressure, heart rate, patients of elective neurosurgery was the and intracranial pressure seen in our patients rapidity of onset of the brain hemiation. In are similar to those found by Grote and Acute intraoperative brain herniation during elective neurosurgery: pathophysiology and management considerations 589 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.61.6.584 on 1 December 1996. Downloaded from Hassler,"° Nornes," and Voldby and lishing a "closed cranium" situation is essen- Enevoldsen'8 in patients with subarachnoid tial in tamponading the source of bleeding" haemorrhage although the magnitude of phys- and minimising the risks of secondary venous iological alterations in our series was lower. infarction of the herniating brain. Deleterious This is probably related to the fact that our effects of continuous open ventricular patients had an open craniotomy, thus damping drainage during subarachnoid haemorrhage the peaks of the ictal changes.5 Studies on such as large intracerebral haematomas and experimental subarachnoid haemorrhage have prolonged post-SAH intracranial hypertension shown a similar course of changes in blood have been described.'8 Furthermore rebound pressure and intracranial pressure919 and a intracranial hypertension after brain compres- possible vascular mechanism for the develop- sion is not only related to an absolute decrease ment of swelling and raised pressure has been in the cerebral perfusion pressure below 50 shown in dogs.'6 mm Hg but also to the duration of circulatory The remarkable feature of all these patients compromise.2 '° Although Batjer and Samson' is that despite an apparently catastrophic considered that when faced with profound intraoperative event all the patients not only brain swelling after intraoperative aneursymal survived the acute ictus but-except for the rupture, the potential benefits of abandoning one patient who died in the perioperative the procedure were debatable,20 the results period and patient 7, who had a glioblas- from this, albeit small, series would suggest toma-also recovered to an independent state. that it may represent a pragmatic approach These outcomes suggest that the surgeon when the aneurysm has not been exposed. The faced with intraoperative brain herniation benefits of expeditious closure of the cranium complicating occult or overt deep intracranial would also seem supported by the subsequent haemorrhage during elective neurosurgery clinical course of most patients in this series. should not consider either resection of normal Replacement of the bone flap, which was brain tissue or induction of systemic hypoten- physically impossible in several of these sion. The first option is not only contrary to patients, does not seem essential for this bene- basic principles of neurosurgery, but given the fit, although such patients may develop a fulminant nature of the herniation, it is pseudomeningocele and require later unlikely that any meaningful surgical resection duraplasty and cranioplasty. Multimodality would have been possible without major loss postoperative monitoring is also useful to min- of neural function. Although brain tissue imise secondary brain insults and guide when resection has been performed after rupture of craniospinal dynamics are normalising. aneurysms before or during dural opening the We are indebted to the late Professor JD Miller for his critical results are generally very poor.'0 Farrar et al,20 comments on the manuscript and Ms J Mason for her typing Gardner,2' and Ransohoff and colleagues22 skills. suggested the use of systemic hypotension to 1 Lobato RD, Sarabia R, Cordobes F, et al. Post-traumatic control intraoperative aneurysmal rupture and cerebral hemisheric swelling. J7 Neurosurg 1988;68: 417-23. reported reasonably favourable results despite 2 Ishii R. Regional cerebral blood flow in patients with the regional cerebral blood flow being at the ruptured intracranial aneurysms. J Neurosurg 1979;50: 587-94. threshold levels at some sites. However, using 3 Kobrine AI, Kempe LG. Studies in head injury-Part I. An such a strategy increases the risk of delayed experimental model of closed head injury. Surg Neurol

1973;1:34-7. http://jnnp.bmj.com/ postopertive ischaemia as aneursymal sub- 4 Langfitt TW, Tannanbaum HM, Kassell NF. The etiology arachnoid haemorrhage is generally associated of brain swelling following experimental head injury. Jf Neurosurg 1966;24:47-56. with disordered cerebrovascular reactivity and 5 Hatashita S, HoffJT. The effect of craniectomy on the bio- metabolic activity.22' 242528 Further, in the face mechanics of normal brain. JfNeurosurg 1987;67:573-8. 6 Meguro K, Kobayashi E, Maki Y. Acute brain swelling of acute brain swelling and raised intracranial during evacuation of subdural hematoma caused by pressure both cerebral perfusion pressure and delayed contralateral extradural hematoma: report of two venous drainage may already be compromised cases. Neurosurgery 1987;20:326-8. in 7 Jennett B. Clinical brain swelling: edema or engorgement? the herniating and retracted brain tissue. In: de Vleiger M, de Lange SA, Beks JW, eds. Brain on September 30, 2021 by guest. Protected copyright. edema. New York: John Wiley, 1981:61-5. Tsementzis and Hitchcock26 reported on "res- 8 Miller JD, Corales RL. Brain edema as a result of head cue clipping" using profound hypotension injury: fact or fallacy? In: de Vleiger M, de Lange SA, < Beks JW, eds. Brain edema. New York: John Wiley, 1981; (MABP 60 mm Hg) after aneurysmal rup- 99-115. ture during induction of anaesthesia. 9 Dorsch N, Branston N, Symon L, Jakubowsky J. Intra- cranial pressure in experimental subarachnoid hemor- Operative conditions in these patients were rhage. In: HoffJT, Betz AL, eds. Intracranialpressure VII. poor and 50% died or were left vegetative. Berlin: Springer Verlag, 1989:715-8. Most 10 Grote E, Hassler W. The critical first minutes after sub- surgeons would nowadays generally arachnoid hemorrhage. Neurosurgery 1988;22:654-6 1. avoid such levels of hypotension during 11 Nornes H. The role of intracranial pressure in the arrest of hemorrhage in patients with ruptured intracranial aneurysmal surgery and if rupture occurred aneurysm. J Neurosurg 1973;39:226-34. with an open surgical field prefer to rely on 12 Marmarou A, Shulman K, LaMorgese J. Compartmental 27 analysis of compliance and outflow resistance of the cere- temporary clips to obtain haemostasis.20 brospinal fluid system. J Neurosurg 1975;48;523-34. Certainly in patient 3 temporary occlusion of 13 Maeda M, Matsura S. Increase in ICP produced by electri- the anterior cal stimulation of the brain stem reticular formation in cerebral artery retarded the herni- cats with spinalization and vagotomy. In: Hoff JT, Betz ation and enabled definitive clippnig of an AL, eds. Intracranialpressure VII. Berlin: Springer Verlag, anterior 1989:292-4. communicating artery. 14 Maeda M, Takahashi K, Miyazaki M, et al. 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