Effects of body position on intracranial and cerebral perfusion pressures in isoflurane-anesthetized horses

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Abstract

Inhalant anesthetics may interfere with normal cerebrovascular autoregulation. It was, therefore, hypothesized that intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in isoflurane-anesthetized horses would be especially sensitive to body and head position because of the potential for large hydrostatic gradients between the brain and heart in this species. Anesthesia was induced and maintained in six clinically healthy, unmedicated geldings with 1.57% isoflurane in O2; mechanical ventilation was used to maintain normocapnia. ICP was measured by using a subarachnoid strain-gauge transducer. Blood gases and carotid arterial, right atrial, and airway pressures were also measured. Five body positions were studied in semirandomized order: dorsal recumbency (DR) with head down (HD), DR with head level (HL), lateral recumbency (LR), sternal recumbency (SR) with HL, and SR with head up (HU). Data were analyzed by using paired t-tests. ICP and CPP values, respectively, are as follows (means ± SD): 36 ± 4 and 55 ± 18 mmHg (DR-HD); 34 ± 6 and 51 ± 32 mmHg (DR-HL); 24 ± 5 and 48 ± 4 mmHg (LR); 19 ± 11 and 87 ± 12 mmHg (SR-HL); and - 14 ± 7 and 71 ± 10 mmHg (SR-HU). Significant differences were found among all positions, except for SR-HL vs. LR. Significant increases in CPP were observed only in sternal positions. In conclusion, ICP in isoflurane-anesthetized horses changes inversely with the brain-to-heart hydrostatic gradient. DR may also cause increases in ICP, irrespective of head position.

Original languageEnglish (US)
Pages (from-to)2542-2546
Number of pages5
JournalJournal of Applied Physiology
Volume92
Issue number6
StatePublished - 2002

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Cerebrovascular Circulation
Isoflurane
Horses
Head
Intracranial Pressure
Atrial Pressure
Intracranial Hypertension
Brain
Transducers
Artificial Respiration

Keywords

  • Equine
  • Posture

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

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title = "Effects of body position on intracranial and cerebral perfusion pressures in isoflurane-anesthetized horses",
abstract = "Inhalant anesthetics may interfere with normal cerebrovascular autoregulation. It was, therefore, hypothesized that intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in isoflurane-anesthetized horses would be especially sensitive to body and head position because of the potential for large hydrostatic gradients between the brain and heart in this species. Anesthesia was induced and maintained in six clinically healthy, unmedicated geldings with 1.57{\%} isoflurane in O2; mechanical ventilation was used to maintain normocapnia. ICP was measured by using a subarachnoid strain-gauge transducer. Blood gases and carotid arterial, right atrial, and airway pressures were also measured. Five body positions were studied in semirandomized order: dorsal recumbency (DR) with head down (HD), DR with head level (HL), lateral recumbency (LR), sternal recumbency (SR) with HL, and SR with head up (HU). Data were analyzed by using paired t-tests. ICP and CPP values, respectively, are as follows (means ± SD): 36 ± 4 and 55 ± 18 mmHg (DR-HD); 34 ± 6 and 51 ± 32 mmHg (DR-HL); 24 ± 5 and 48 ± 4 mmHg (LR); 19 ± 11 and 87 ± 12 mmHg (SR-HL); and - 14 ± 7 and 71 ± 10 mmHg (SR-HU). Significant differences were found among all positions, except for SR-HL vs. LR. Significant increases in CPP were observed only in sternal positions. In conclusion, ICP in isoflurane-anesthetized horses changes inversely with the brain-to-heart hydrostatic gradient. DR may also cause increases in ICP, irrespective of head position.",
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author = "Brosnan, {Robert J} and Eugene Steffey and LeCouteur, {Richard A} and Ayako Imai and Farver, {Thomas B} and Kortz, {Gregg D.}",
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T1 - Effects of body position on intracranial and cerebral perfusion pressures in isoflurane-anesthetized horses

AU - Brosnan, Robert J

AU - Steffey, Eugene

AU - LeCouteur, Richard A

AU - Imai, Ayako

AU - Farver, Thomas B

AU - Kortz, Gregg D.

PY - 2002

Y1 - 2002

N2 - Inhalant anesthetics may interfere with normal cerebrovascular autoregulation. It was, therefore, hypothesized that intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in isoflurane-anesthetized horses would be especially sensitive to body and head position because of the potential for large hydrostatic gradients between the brain and heart in this species. Anesthesia was induced and maintained in six clinically healthy, unmedicated geldings with 1.57% isoflurane in O2; mechanical ventilation was used to maintain normocapnia. ICP was measured by using a subarachnoid strain-gauge transducer. Blood gases and carotid arterial, right atrial, and airway pressures were also measured. Five body positions were studied in semirandomized order: dorsal recumbency (DR) with head down (HD), DR with head level (HL), lateral recumbency (LR), sternal recumbency (SR) with HL, and SR with head up (HU). Data were analyzed by using paired t-tests. ICP and CPP values, respectively, are as follows (means ± SD): 36 ± 4 and 55 ± 18 mmHg (DR-HD); 34 ± 6 and 51 ± 32 mmHg (DR-HL); 24 ± 5 and 48 ± 4 mmHg (LR); 19 ± 11 and 87 ± 12 mmHg (SR-HL); and - 14 ± 7 and 71 ± 10 mmHg (SR-HU). Significant differences were found among all positions, except for SR-HL vs. LR. Significant increases in CPP were observed only in sternal positions. In conclusion, ICP in isoflurane-anesthetized horses changes inversely with the brain-to-heart hydrostatic gradient. DR may also cause increases in ICP, irrespective of head position.

AB - Inhalant anesthetics may interfere with normal cerebrovascular autoregulation. It was, therefore, hypothesized that intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in isoflurane-anesthetized horses would be especially sensitive to body and head position because of the potential for large hydrostatic gradients between the brain and heart in this species. Anesthesia was induced and maintained in six clinically healthy, unmedicated geldings with 1.57% isoflurane in O2; mechanical ventilation was used to maintain normocapnia. ICP was measured by using a subarachnoid strain-gauge transducer. Blood gases and carotid arterial, right atrial, and airway pressures were also measured. Five body positions were studied in semirandomized order: dorsal recumbency (DR) with head down (HD), DR with head level (HL), lateral recumbency (LR), sternal recumbency (SR) with HL, and SR with head up (HU). Data were analyzed by using paired t-tests. ICP and CPP values, respectively, are as follows (means ± SD): 36 ± 4 and 55 ± 18 mmHg (DR-HD); 34 ± 6 and 51 ± 32 mmHg (DR-HL); 24 ± 5 and 48 ± 4 mmHg (LR); 19 ± 11 and 87 ± 12 mmHg (SR-HL); and - 14 ± 7 and 71 ± 10 mmHg (SR-HU). Significant differences were found among all positions, except for SR-HL vs. LR. Significant increases in CPP were observed only in sternal positions. In conclusion, ICP in isoflurane-anesthetized horses changes inversely with the brain-to-heart hydrostatic gradient. DR may also cause increases in ICP, irrespective of head position.

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