Temperature changes of ≥ 1°C alter functional neurologic outcome and histopathology in a canine model of complete cerebral ischemia

C. T. Wass, W. L. Lanier, R. E. Hofer, B. W. Scheithauer, Amy Andrews

Research output: Contribution to journalArticle

213 Citations (Scopus)

Abstract

Background: Changes in basal temperature of ≥ 1°C (e.g., fever-induced hyperthermia or anesthesia-related hypothermia) are a common occurrence in neurologically impaired patients. The current study tested the hypothesis that temperature changes as small as 1°C or 2°C would significantly alter post-ischemic functional neurologic outcome and cerebral histopathology. The hypothesis was tested in a canine model of transient, complete cerebral ischemia. Methods: After institutional approval, 21 dogs were randomly assigned to one of three temperature-specific groups: (1) a reference group maintained at 37.0 ± 0.3°C (target temperature ± range); (2) a 38.0 ± 0.3°C group; or (3) a 39.0 ± 0.3°C group (n = 7 per group). Complete cerebral ischemia 12.5 min in duration was produced using an established model of arterial hypotension plus intracranial hypertension. Right atrial and cranial (beneath the temporalis muscles) temperatures were maintained at the target value, beginning 20 min before ischemia and ceasing 1 h postischemia. Thereafter, temperatures were returned to 37.0 ± 0.3°C in all dogs. After discharge from the intensive care environment, all dogs were placed in a temperature-controlled recovery area. Neurologic assessment was performed by a blinded observer at 24, 48, and 72 h postischemia using a 100- point scoring scale. After the 72 h examination (with the dogs anesthetized) or at the time of ischemia-related death, the brains were excised and preserved. The brains subsequently were histologically scored by a neuropathologist who was unaware of the treatment groups. All 21 dogs were included in the analysis of neurologic function, however, only dogs that survived for ≥ 24 h postischemia were included in the histopathology analysis. Results: Dogs were well matched for systemic physiologic variables throughout the study, with the exception of temperature. During the 72 h postischemic examination, dogs maintained at 37°C were either normal or near normal. In contrast, dogs maintained at 39°C were either comatose or died from ischemia-related causes. Dogs maintained at 38°C were intermediate between 37°C and 39°C dogs. When compared with the reference group, both 38°C and 39°C dogs had significantly worse neurologic function scores (P < 0.01 and < 0.001, respectively) and histopathology scores (P < 0.01 for both). There also was a significant correlation between neurologic function and histopathology rank scores (r(s) = 0.96; P < 0.001). Conclusions: Small, clinically relevant changes in temperature (1°C or 2°C) resulted in significant alterations in both postischemic neurologic function and cerebral histopathology. Assuming that our results are transferable to humans, the results suggest that, in patients at imminent risk for ischemic neurologic injury, body temperature should be closely monitored. Further, the clinician should aggressively treat all episodes of hyperthermia until the patient is no longer at risk for ischemic neurologic injury.

Original languageEnglish (US)
Pages (from-to)325-335
Number of pages11
JournalAnesthesiology
Volume83
Issue number2
DOIs
StatePublished - 1995

Fingerprint

Brain Ischemia
Nervous System
Canidae
Dogs
Temperature
Nervous System Trauma
Ischemia
Fever
Malignant Hyperthermia
Induced Hyperthermia
Brain Death
Intracranial Hypertension
Transient Ischemic Attack
Critical Care
Coma
Hypothermia
Body Temperature
Hypotension
Muscles

Keywords

  • Brain: ischemia; protection
  • Temperature: hyperthermia; hypothermia

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Temperature changes of ≥ 1°C alter functional neurologic outcome and histopathology in a canine model of complete cerebral ischemia. / Wass, C. T.; Lanier, W. L.; Hofer, R. E.; Scheithauer, B. W.; Andrews, Amy.

In: Anesthesiology, Vol. 83, No. 2, 1995, p. 325-335.

Research output: Contribution to journalArticle

Wass, C. T. ; Lanier, W. L. ; Hofer, R. E. ; Scheithauer, B. W. ; Andrews, Amy. / Temperature changes of ≥ 1°C alter functional neurologic outcome and histopathology in a canine model of complete cerebral ischemia. In: Anesthesiology. 1995 ; Vol. 83, No. 2. pp. 325-335.
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abstract = "Background: Changes in basal temperature of ≥ 1°C (e.g., fever-induced hyperthermia or anesthesia-related hypothermia) are a common occurrence in neurologically impaired patients. The current study tested the hypothesis that temperature changes as small as 1°C or 2°C would significantly alter post-ischemic functional neurologic outcome and cerebral histopathology. The hypothesis was tested in a canine model of transient, complete cerebral ischemia. Methods: After institutional approval, 21 dogs were randomly assigned to one of three temperature-specific groups: (1) a reference group maintained at 37.0 ± 0.3°C (target temperature ± range); (2) a 38.0 ± 0.3°C group; or (3) a 39.0 ± 0.3°C group (n = 7 per group). Complete cerebral ischemia 12.5 min in duration was produced using an established model of arterial hypotension plus intracranial hypertension. Right atrial and cranial (beneath the temporalis muscles) temperatures were maintained at the target value, beginning 20 min before ischemia and ceasing 1 h postischemia. Thereafter, temperatures were returned to 37.0 ± 0.3°C in all dogs. After discharge from the intensive care environment, all dogs were placed in a temperature-controlled recovery area. Neurologic assessment was performed by a blinded observer at 24, 48, and 72 h postischemia using a 100- point scoring scale. After the 72 h examination (with the dogs anesthetized) or at the time of ischemia-related death, the brains were excised and preserved. The brains subsequently were histologically scored by a neuropathologist who was unaware of the treatment groups. All 21 dogs were included in the analysis of neurologic function, however, only dogs that survived for ≥ 24 h postischemia were included in the histopathology analysis. Results: Dogs were well matched for systemic physiologic variables throughout the study, with the exception of temperature. During the 72 h postischemic examination, dogs maintained at 37°C were either normal or near normal. In contrast, dogs maintained at 39°C were either comatose or died from ischemia-related causes. Dogs maintained at 38°C were intermediate between 37°C and 39°C dogs. When compared with the reference group, both 38°C and 39°C dogs had significantly worse neurologic function scores (P < 0.01 and < 0.001, respectively) and histopathology scores (P < 0.01 for both). There also was a significant correlation between neurologic function and histopathology rank scores (r(s) = 0.96; P < 0.001). Conclusions: Small, clinically relevant changes in temperature (1°C or 2°C) resulted in significant alterations in both postischemic neurologic function and cerebral histopathology. Assuming that our results are transferable to humans, the results suggest that, in patients at imminent risk for ischemic neurologic injury, body temperature should be closely monitored. Further, the clinician should aggressively treat all episodes of hyperthermia until the patient is no longer at risk for ischemic neurologic injury.",
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T1 - Temperature changes of ≥ 1°C alter functional neurologic outcome and histopathology in a canine model of complete cerebral ischemia

AU - Wass, C. T.

AU - Lanier, W. L.

AU - Hofer, R. E.

AU - Scheithauer, B. W.

AU - Andrews, Amy

PY - 1995

Y1 - 1995

N2 - Background: Changes in basal temperature of ≥ 1°C (e.g., fever-induced hyperthermia or anesthesia-related hypothermia) are a common occurrence in neurologically impaired patients. The current study tested the hypothesis that temperature changes as small as 1°C or 2°C would significantly alter post-ischemic functional neurologic outcome and cerebral histopathology. The hypothesis was tested in a canine model of transient, complete cerebral ischemia. Methods: After institutional approval, 21 dogs were randomly assigned to one of three temperature-specific groups: (1) a reference group maintained at 37.0 ± 0.3°C (target temperature ± range); (2) a 38.0 ± 0.3°C group; or (3) a 39.0 ± 0.3°C group (n = 7 per group). Complete cerebral ischemia 12.5 min in duration was produced using an established model of arterial hypotension plus intracranial hypertension. Right atrial and cranial (beneath the temporalis muscles) temperatures were maintained at the target value, beginning 20 min before ischemia and ceasing 1 h postischemia. Thereafter, temperatures were returned to 37.0 ± 0.3°C in all dogs. After discharge from the intensive care environment, all dogs were placed in a temperature-controlled recovery area. Neurologic assessment was performed by a blinded observer at 24, 48, and 72 h postischemia using a 100- point scoring scale. After the 72 h examination (with the dogs anesthetized) or at the time of ischemia-related death, the brains were excised and preserved. The brains subsequently were histologically scored by a neuropathologist who was unaware of the treatment groups. All 21 dogs were included in the analysis of neurologic function, however, only dogs that survived for ≥ 24 h postischemia were included in the histopathology analysis. Results: Dogs were well matched for systemic physiologic variables throughout the study, with the exception of temperature. During the 72 h postischemic examination, dogs maintained at 37°C were either normal or near normal. In contrast, dogs maintained at 39°C were either comatose or died from ischemia-related causes. Dogs maintained at 38°C were intermediate between 37°C and 39°C dogs. When compared with the reference group, both 38°C and 39°C dogs had significantly worse neurologic function scores (P < 0.01 and < 0.001, respectively) and histopathology scores (P < 0.01 for both). There also was a significant correlation between neurologic function and histopathology rank scores (r(s) = 0.96; P < 0.001). Conclusions: Small, clinically relevant changes in temperature (1°C or 2°C) resulted in significant alterations in both postischemic neurologic function and cerebral histopathology. Assuming that our results are transferable to humans, the results suggest that, in patients at imminent risk for ischemic neurologic injury, body temperature should be closely monitored. Further, the clinician should aggressively treat all episodes of hyperthermia until the patient is no longer at risk for ischemic neurologic injury.

AB - Background: Changes in basal temperature of ≥ 1°C (e.g., fever-induced hyperthermia or anesthesia-related hypothermia) are a common occurrence in neurologically impaired patients. The current study tested the hypothesis that temperature changes as small as 1°C or 2°C would significantly alter post-ischemic functional neurologic outcome and cerebral histopathology. The hypothesis was tested in a canine model of transient, complete cerebral ischemia. Methods: After institutional approval, 21 dogs were randomly assigned to one of three temperature-specific groups: (1) a reference group maintained at 37.0 ± 0.3°C (target temperature ± range); (2) a 38.0 ± 0.3°C group; or (3) a 39.0 ± 0.3°C group (n = 7 per group). Complete cerebral ischemia 12.5 min in duration was produced using an established model of arterial hypotension plus intracranial hypertension. Right atrial and cranial (beneath the temporalis muscles) temperatures were maintained at the target value, beginning 20 min before ischemia and ceasing 1 h postischemia. Thereafter, temperatures were returned to 37.0 ± 0.3°C in all dogs. After discharge from the intensive care environment, all dogs were placed in a temperature-controlled recovery area. Neurologic assessment was performed by a blinded observer at 24, 48, and 72 h postischemia using a 100- point scoring scale. After the 72 h examination (with the dogs anesthetized) or at the time of ischemia-related death, the brains were excised and preserved. The brains subsequently were histologically scored by a neuropathologist who was unaware of the treatment groups. All 21 dogs were included in the analysis of neurologic function, however, only dogs that survived for ≥ 24 h postischemia were included in the histopathology analysis. Results: Dogs were well matched for systemic physiologic variables throughout the study, with the exception of temperature. During the 72 h postischemic examination, dogs maintained at 37°C were either normal or near normal. In contrast, dogs maintained at 39°C were either comatose or died from ischemia-related causes. Dogs maintained at 38°C were intermediate between 37°C and 39°C dogs. When compared with the reference group, both 38°C and 39°C dogs had significantly worse neurologic function scores (P < 0.01 and < 0.001, respectively) and histopathology scores (P < 0.01 for both). There also was a significant correlation between neurologic function and histopathology rank scores (r(s) = 0.96; P < 0.001). Conclusions: Small, clinically relevant changes in temperature (1°C or 2°C) resulted in significant alterations in both postischemic neurologic function and cerebral histopathology. Assuming that our results are transferable to humans, the results suggest that, in patients at imminent risk for ischemic neurologic injury, body temperature should be closely monitored. Further, the clinician should aggressively treat all episodes of hyperthermia until the patient is no longer at risk for ischemic neurologic injury.

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