title: Deliberate employment of postoperative hypotension for brain arteriovenous malformation surgery and the incidence of delayed postoperative hemorrhage: a prospective cohort study.
abstract: OBJECTIVE The aim of this study was to examine the impact of deliberate employment of postoperative hypotension on delayed postoperative hemorrhage (DPH) for all Spetzler-Ponce Class (SPC) C brain arteriovenous malformations (bAVMs) and SPC B bAVMs ≥ 3.5 cm in diameter (SPC B 3.5+). METHODS A protocol of deliberate employment of postoperative hypotension was introduced in June 1997 for all SPC C and SPC B 3.5+ bAVMs. The aim was to achieve a maximum mean arterial blood pressure (BP) ≤ 70 mm Hg (with cerebral perfusion pressure > 50 mm Hg) for a minimum of 7 days after resection of bAVMs (BP protocol). The authors compared patients who experienced DPH (defined as brain hemorrhage into the resection bed that resulted in a new neurological deficit or that resulted in reoperation during the hospitalization for microsurgical bAVM resection) between 2 periods (prior to adopting the BP protocol and after introduction of the BP protocol) and 4 bAVM categories (SPC A, SPC B 3.5- [that is, SPC B < 3.5 cm maximum diameter], SPC B 3.5+, and SPC C). Patients excluded from treatment by the BP protocol were managed in the intensive care unit to avoid moderate hypertensive episodes. The pooled cases of all bAVM treated by surgery were analyzed to identify characteristics associated with the risk of DPH. These identified characteristics were then examined by multiple logistic regression analysis in both SPC B 3.5+ and SPC C cases. RESULTS From a cohort of 641 bAVMs treated by microsurgery, 32 patients with DPH were identified. Of those, 66% (95% CI 48-80) had a permanent new neurological deficit with a modified Rankin Scale score of 2-6. This included a mortality rate of 13% (95% CI 4.4-29). The BP protocol was used to treat 162 patients with either SPC B 3.5+ or SPC C. For SPC B 3.5+, there was no significant reduction in DPH with the introduction of the BP protocol (p = 0.77). For SPC C, there was a significant (p = 0.035) reduction of DPH from 29% (95% CI 13%-53%) to 8.2% (95% CI 3.2%-18%) associated with the introduction of the BP protocol. Multiple logistic regression analysis found that the absence of the BP protocol (p = 0.011, odds ratio 7.5, 95% CI 1.6-36) remained significant for the development of DPH in patients with SPC C bAVMs. CONCLUSIONS Treating patients with SPC C bAVMs with a protocol that lowers BP immediately after resection seems to reduce the risk of DPH. For SPC A and SPC B 3.5- bAVMs, there is unlikely to be a need to do more than avoid postoperative hypertension. For SPC B 3.5+ bAVMs, a larger number of patients would be required to test the absence of benefit of the BP protocol.
authors.affiliation: Departments of 1 Clinical Medicine and.
authors.forename: Michael Kerin
authors.initials: MK
authors.lastname: Morgan
authors.affiliation: Departments of 1 Clinical Medicine and.
authors.forename: Markus Karl Hermann
authors.initials: MKH
authors.lastname: Wiedmann
authors.affiliation: Departments of 1 Clinical Medicine and.
authors.forename: Nazih N A
authors.initials: NNA
authors.lastname: Assaad
authors.affiliation: Departments of 1 Clinical Medicine and.|Department of Intensive Care, Macquarie University Hospital, Ryde, New South Wales, Australia.
authors.forename: Michael J A
authors.initials: MJA
authors.lastname: Parr
authors.affiliation: Statistics, Macquarie University, Sydney; and.
authors.forename: Gillian Z
authors.initials: GZ
authors.lastname: Heller
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007022:Hypotension; D015994:Incidence; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D008297:Male; D008866:Microsurgery / Q000009:adverse effects; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000009:adverse effects*; D011182:Postoperative Care; D019106:Postoperative Hemorrhage / Q000453:epidemiology* / Q000209:etiology*; D012307:Risk Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: AVM; BP = blood pressure; CPP = cerebral perfusion pressure; CTA = CT angiography; DPH = delayed postoperative hemorrhage; DSA = digital subtraction angiography; ICP = intracranial pressure; ICU = intensive care unit; MABP = mean arterial BP; ROC = receiver operating characteristic; SMG = Spetzler-Martin grade; SPC = Spetzler-Ponce class; arteriovenous malformation; bAVM = brain arteriovenous malformation; blood pressure; brain; cohort study; hemorrhage; intensive care; mRS = modified Rankin Scale; surgery; vascular disorders