title: How large is the typical subarachnoid hemorrhage? A review of current neurosurgical knowledge.
abstract: BACKGROUND
  Despite the morbidity and mortality of subarachnoid hemorrhage (SAH), the average volume of a typical hemorrhage is not well defined. Animal models of SAH often do not accurately mimic the human disease process.
  
  
  OBJECTIVE
  The purpose of this study is to estimate the average SAH volume, allowing standardization of animal models of the disease.
  
  
  METHODS
  We performed a MEDLINE search of SAH volume and erythrocyte counts in human cerebrospinal fluid as well as for volumes of blood used in animal injection models of SAH, from 1956 to 2010. We polled members of the American Association of Neurological Surgeons (AANS) for estimates of typical SAH volume. Using quantitative data from the literature, we calculated the total volume of SAH as equal to the volume of blood clotted in basal cisterns plus the volume of dispersed blood in cerebrospinal fluid. The results of the AANS poll confirmed our estimates.
  
  
  RESULTS
  The human literature yielded 322 publications and animal literature, 237 studies. Four quantitative human studies reported blood clot volumes ranging from 0.2 to 170 mL, with a mean of ∼20 mL. There was only one quantitative study reporting cerebrospinal fluid red blood cell counts from serial lumbar puncture after SAH. Dispersed blood volume ranged from 2.9 to 45.9 mL, and we used the mean of 15 mL for our calculation. Therefore, total volume of SAH equals 35 mL. The AANS poll yielded 176 responses, ranging from 2 to 350 mL, with a mean of 33.9 ± 4.4 mL.
  
  
  CONCLUSIONS
  Based on our estimate of total SAH volume of 35 mL, animal injection models may now become standardized for more accurate portrayal of the human disease process.
authors.affiliation: Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA. robert.whitmore@uphs.upenn.edu
authors.forename: Robert G
authors.initials: RG
authors.lastname: Whitmore
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Grant
authors.forename: Peter
authors.initials: P
authors.lastname: LeRoux
authors.forename: Omar
authors.initials: O
authors.lastname: El-Falaki
authors.forename: Sherman C
authors.initials: SC
authors.lastname: Stein
mesh_terms: D000818:Animals; D001810:Blood Volume; D002555:Cerebrospinal Fluid / Q000166:cytology; D004195:Disease Models, Animal; D004906:Erythrocyte Count; D006801:Humans; D009493:Neurosurgery; D019635:Neurosurgical Procedures; D013345:Subarachnoid Hemorrhage / Q000473:pathology* / Q000601:surgery