title: The Association Between Spontaneous Hyperventilation, Delayed Cerebral Ischemia, and Poor Neurological Outcome in Patients with Subarachnoid Hemorrhage.
abstract: BACKGROUND
  The frequency and associations of spontaneous hyperventilation in subarachnoid hemorrhage (SAH) are unknown. Because hyperventilation decreases cerebral blood flow, it may exacerbate delayed cerebral ischemia (DCI) and worsen neurological outcome.
  
  
  METHODS
  This is a retrospective analysis of data from a prospectively collected cohort of SAH patients at an academic medical center. Spontaneous hyperventilation was defined by PaCO2 <35 mmHg and pH >7.45 and subdivided into moderate and severe groups. Clinical and demographic characteristics of patients with and without spontaneous hyperventilation were compared using χ (2) or t tests. Bivariate and multivariable logistic regression analyses were conducted to examine the association of moderate and severe hyperventilation with DCI and discharge neurological outcome.
  
  
  RESULTS
  Of 207 patients, 113 (55 %) had spontaneous hyperventilation. Spontaneously hyperventilating patients had greater illness severity as measured by the Hunt-Hess, World Federation of Neurosurgical Societies (WFNS), and SAH sum scores. They were also more likely to develop the following complications: pneumonia, neurogenic myocardial injury, systemic inflammatory response syndrome (SIRS), radiographic vasospasm, DCI, and poor neurological outcome. In a multivariable logistic regression model including age, gender, WFNS, SAH sum score, pneumonia, neurogenic myocardial injury, etiology, and SIRS, only moderate [odds ratio (OR) 2.49, 95 % confidence interval (CI) 1.10-5.62] and severe (OR 3.12, 95 % CI 1.30-7.49) spontaneous hyperventilation were associated with DCI. Severe spontaneous hyperventilation (OR 4.52, 95 % CI 1.37-14.89) was also significantly associated with poor discharge outcome in multivariable logistic regression analysis.
  
  
  CONCLUSIONS
  Spontaneous hyperventilation is common in SAH and is associated with DCI and poor neurological outcome.
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA. craigaw@med.umich.edu.|Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA. craigaw@med.umich.edu.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Williamson
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA.|Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Sheehan
authors.affiliation: Robert Wood Johnson Foundation Clinical Scholars Program, University of Michigan, Ann Arbor, MI, 48109, USA.|Division of General Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Renuka
authors.initials: R
authors.lastname: Tipirneni
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Roark
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA.
authors.forename: Aditya S
authors.initials: AS
authors.lastname: Pandey
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA.
authors.forename: B Gregory
authors.initials: BG
authors.lastname: Thompson
authors.affiliation: Department of Neurosurgery, University of Michigan, 3552 Taubman Health Care Center, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109, USA.|Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Venkatakrishna
authors.initials: V
authors.lastname: Rajajee
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000150:complications* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000453:epidemiology
keywords: Brain ischemia; Cerebral vasospasm; Hyperventilation; Hypocapnia; Respiratory alkalosis; Stroke; Subarachnoid hemorrhage
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