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 O(2); 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.
Publication Date: 2002-05-17 PubMed ID: 12015371DOI: 10.1152/japplphysiol.00055.2002Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates the effects of different body positions on brain and heart pressures in horses under the influence of anesthetic isoflurane. It found that the intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are significantly affected by the horse’s body and head alignment due to the significant hydrostatic gradients, or pressure differences, between the heart and brain in horses.
Methods and Procedures
- Anesthesia, containing 1.57% isoflurane in O(2), was introduced and maintained in six healthy, unbred male horses without any medication. The horses were mechanically ventilated to maintain normal carbon dioxide levels (normocapnia).
- ICP was measured using a gauge called a subarachnoid-strain-gauge transducer which measures pressure within the subarachnoid space that surrounds the brain and spinal cord.
- In addition, blood gases and the pressures within the carotid artery, right atrium, and airway were measured.
- The study explored five different body positions of horses in a semi-randomized order: lying on back with head down (DR-HD), lying on back with level head (DR-HL), lying on one side (LR), lying on chest with level head (SR-HL), and lying on chest with head up (SR-HU).
Results
- The study provided averaged ICP and CPP values for the different positions. The highest ICP was observed when horse was laying on its back (both head down and level head positions), and the lowest when on its chest with head up.
- Different body positions resulted in significant differences in ICP and CPP values. The only exception was between the positions of sternal recumbency with head level (SR-HL) and lateral recumbency (LR) where no significant distinction in values was observed.
- There was a significant increase in CPP values in sternal positions (both head level and head up).
Conclusion
- The study concluded that in horses anesthetized with isoflurane, ICP changes inversely with the hydrostatic gradient between the brain and the heart. That means that as the pressure difference between the brain and heart increased, the ICP decreased.
- It was also found that the position of dorsal recumbency (DR) could lead to increase in ICP, irrespective of the head position. So, laying on the back could increase ICP whether the head is level or down.
Cite This Article
APA
Brosnan RJ, Steffey EP, LeCouteur RA, Imai A, Farver TB, Kortz GD.
(2002).
Effects of body position on intracranial and cerebral perfusion pressures in isoflurane-anesthetized horses.
J Appl Physiol (1985), 92(6), 2542-2546.
https://doi.org/10.1152/japplphysiol.00055.2002 Publication
Researcher Affiliations
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA. rjbrosnan@ucdavis.edu
MeSH Terms
- Anesthesia
- Anesthetics, Inhalation
- Animals
- Blood Pressure / physiology
- Cerebrovascular Circulation / physiology
- Heart / physiology
- Horses / physiology
- Intracranial Pressure / physiology
- Isoflurane
- Male
- Posture / physiology
- Respiratory Physiological Phenomena
Citations
This article has been cited 9 times.- Sepehrinezhad A, Stolze Larsen F, Ashayeri Ahmadabad R, Shahbazi A, Sahab Negah S. The Glymphatic System May Play a Vital Role in the Pathogenesis of Hepatic Encephalopathy: A Narrative Review. Cells 2023 Mar 23;12(7).
- Trimmel NE, Podgoršak A, Oertel MF, Jucker S, Arras M, Schmid Daners M, Weisskopf M. The Sheep as a Comprehensive Animal Model to Investigate Interdependent Physiological Pressure Propagation and Multiparameter Influence on Cerebrospinal Fluid Dynamics. Front Neurosci 2022;16:868567.
- Sturges BK, Dickinson PJ, Tripp LD, Udaltsova I, LeCouteur RA. Intracranial pressure monitoring in normal dogs using subdural and intraparenchymal miniature strain-gauge transducers. J Vet Intern Med 2019 Mar;33(2):708-716.
- Lindstrøm EK, Ringstad G, Mardal KA, Eide PK. Cerebrospinal fluid volumetric net flow rate and direction in idiopathic normal pressure hydrocephalus. Neuroimage Clin 2018;20:731-741.
- Lee H, Xie L, Yu M, Kang H, Feng T, Deane R, Logan J, Nedergaard M, Benveniste H. The Effect of Body Posture on Brain Glymphatic Transport. J Neurosci 2015 Aug 5;35(31):11034-44.
- Verdonck P, Kalmar AF, Suy K, Geeraerts T, Vercauteren M, Mottrie A, De Wolf AM, Hendrickx JF. Optic nerve sheath diameter remains constant during robot assisted laparoscopic radical prostatectomy. PLoS One 2014;9(11):e111916.
- Brosnan RJ. Inhaled anesthetics in horses. Vet Clin North Am Equine Pract 2013 Apr;29(1):69-87.
- Peschke T, Feuerecker M, Siegl D, Schicktanz N, Stief C, Zu Eulenburg P, Choukér A, Buchheim JI. Assessing Stress Induced by Fluid Shifts and Reduced Cerebral Clearance during Robotic-Assisted Laparoscopic Radical Prostatectomy under Trendelenburg Positioning (UroTreND Study). Methods Protoc 2024 Apr 1;7(2).
- de Preux M, Precht C, Guevar J, Graubner C, Thenhaus-Schnabel S, Buser L, Lukes A, Koch C. A transmandibular lateral transsphenoidal navigated surgical approach to access a pituitary macroadenoma in a warmblood mare. Vet Q 2024 Dec;44(1):1-10.
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