The effect of decompressive hemicraniectomy on brain temperature after severe brain injury.
BACKGROUND
Animal studies have shown that even a small temperature elevation of 1°C can cause detrimental effects after brain injury. Since the skull acts as a potential thermal insulator, we hypothesized that decompressive hemicraniectomy facilitates surface cooling and lowers brain temperature.


METHODS
Forty-eight patients with severe brain injury (TBI = 38, ICH = 10) with continuous brain temperature monitoring were retrospectively studied and grouped into "hemicraniectomy" (n = 20) or "no hemicraniectomy" (n = 28) group. The paired measurements of core body (T Core) and brain (T Br) temperature were recorded at 1-min intervals over 12 ± 7 days. As a surrogate measure for the extent of surface heat loss from the brain, ∆T Core-Br was calculated as the difference between T Core and T Br with each recording. In order to accommodate within-patient temperature correlations, mixed-model regression was used to assess the differences in ∆T Core-Br between those with and without hemicraniectomy, adjusted for core body temperature and diagnosis.


RESULTS
A total of 295,883 temperature data pairs were collected (median [IQR] per patient: 5047 [3125-8457]). Baseline characteristics were similar for age, sex, diagnosis, incidence of sepsis, Glasgow Coma Scale score, ICU mortality, and ICU length of stay between the two groups. The mean difference in ∆T Core-Br was 1.29 ± 0.87°C for patients with and 0.80 ± 0.86°C for patients without hemicraniectomy (P < 0.0001). In mixed-model regression, accounting for temperature correlations within patients, hemicraniectomy and higher T Core were associated with greater ∆T Core-Br (hemicraniectomy: estimated effect = 0.60, P = 0.003; T Core: estimated effect = 0.21, P < 0.0001).


CONCLUSIONS
Hemicraniectomy is associated with modestly but significantly lower brain temperature relative to core body temperature.
Department of Neurovascular Service, University of California San Francisco, 505 Parnassus Avenue, M-830, San Francisco, CA 94143-0114, USA. kazuma.nakagawa@ucsfmedctr.org
Kazuma
K
Nakagawa
Nancy K
NK
Hills
Hooman
H
Kamel
Morabito
Diane
Pratik V
PV
Patel
Geoffrey T
GT
Manley
J Claude
JC
Hemphill
D000328:Adult; D000368:Aged; D001831:Body Temperature; D001930:Brain Injuries / Q000150:complications* / Q000601:surgery*; D056424:Decompressive Craniectomy; D005260:Female; D005334:Fever / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult