Direct measurement of intracranial pressure in adult horses

Brosnan, Robert J; Lecouteur, Richard A; Steffey, Eugene; Imai, Ayako; Kortz, Gregg D.

doi:10.2460/ajvr.2002.63.1252

Cited by 33 publications

(34 citation statements)

References 26 publications

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“…55 More invasive diagnostic and monitoring modalities are available (Table 24.3). Methods to measure and monitor intracranial and cerebral perfusion pressures have been described for use in foals 56 and adult horses [57][58][59][60][61] ; however, these techniques have thus far not been scientifically evaluated in clinical cases. In human medicine, development of advanced bedside neuromonitoring devices has been an important focus in neurocritical care.…”

Section: Traumatic Brain Injurymentioning

confidence: 99%

Central Nervous System Trauma

Nout¹

2007

Equine Neurology

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Section: Traumatic Brain Injurymentioning

confidence: 99%

Central Nervous System Trauma

Nout¹

2007

Equine Neurology

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“…Measurements of awake, standing horses revealed ICP values in the range of 2 Ϯ 4 mm Hg, which are consistent with other animals. 5 In contrast, anesthesia and recumbency affects the body's ability to maintain normal CBF, CPP, and ICP. When horses are placed in headdependent positions, both ICP and CPP increase 10-fold over values in awake, standing horses.…”

mentioning

confidence: 99%

“…4,32 Although a method of direct measurement of ICP in horses is possible, it is not feasible in most clinical patients. 5 Elevated ICP can be indirectly inferred from MAP: in order to maintain CPP, MAP will increase in response to increased ICP. This phenomenon is the Cushing's effect.…”

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confidence: 99%

Anesthetic Considerations for Horses with Neurologic Disease

Smith¹

2007

Equine Neurology

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149Neurologic disease can present a variety of challenges for the anesthetist. The unique anatomical features of the brain limit its ability to respond to inflammatory, traumatic, and neoplastic challenges. Horses presenting with spinal cord or peripheral neuropathies can be challenging to the anesthetist due to the increased danger of a large, ataxic patient. The goal of neurologic anesthesia is to maintain adequate nourishment and blood delivery to the brain, minimize the development of seizures, minimize the effects of ataxia on the patient's safety, and prevent further deterioration of neurologic status.An understanding of the anatomy and physiology of the nervous system and how it relates to anesthesia is important in understanding how best to maximize patient safety and minimize morbidity and mortality.The brain is housed entirely within a bony cavity. This rigid structure does not allow for an increase in volume when faced with a traumatic, inflammatory, or neoplastic insult. Minor changes in cerebral blood flow (CBF), cerebrospinal fluid (CSF), or tissue volume (i.e., mass) can quickly result in a moderateto-severe increase in intracranial pressure (ICP). Elevated ICP can cause regional and global cerebral ischemia and hypoxia due to a reduction in cerebral perfusion pressure (CPP) and CBF, and ultimately can lead to potentially fatal displacement of brain and neuronal tissue, including brainstem herniation. 1 CBF is directly proportional to CPP and indirectly proportional to cerebral vascular resistance (CVR). Of these components, only CBF can be easily influenced by the anesthetist and thus is of particular interest.In a normal horse, CBF is under metabolic (chemical), myogenic (autoregulation), and neurogenic factors. 2 This control ensures consistent, high flow of blood to the brain over a range of arterial blood pressures. The mean arterial pressure (MAP) range within which CBF remains under autoregulatory control has not been defined in horses; however, in humans, the CBF remains consistent over 70-140 mm Hg, and animals may have better regulation of flow at lower arterial pressures. 2 Horses, due to their large size, undergo large orthostatic shifts when positioned in lateral or dorsal recumbency for general anesthesia. 3 These fluid shifts can alter MAP and thus have an effect on CPP.Chemical or metabolic factors that influence CBF include cerebral metabolic rate (CMR), the partial pressure of arterial carbon dioxide (P a CO 2 ), the partial pressure of arterial oxygen (P a O 2 ), and temperature. An increase in CMR will lead to an increase in CBF. 2 Anesthetics, both injectable and inhaled, can alter CMR and therefore influence CBF. Likewise, an increase in the temperature of the brain causes an increase in CBF.There is a directly proportionate relationship between CBF and P a CO 2 . These changes are due to intra-and extracellular pH alterations. Hypocapnia and alkalemia lead to a decrease in CBF due to vasoconstriction, resulting in an increase in CVR. Conversely, hypercapnia and acidemia resul...

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“…Although the direct measurement of intracranial pressure has been reported in horses 14 , the invasiveness of this procedure prohibits its use as a routine neuromonitoring tool. As alterations in cerebral haemodynamics may be a contributing factor to the complications associated with postanaesthetic recovery in horses, use of a non-invasive neuromonitoring tool such as NIRS may prove to be beneficial.…”

mentioning

confidence: 99%

“…The direct measurement of intracranial pressure has been reported 14 ; however the invasiveness of this procedure prohibits its use as a routine neuromonitoring tool in horses.…”

mentioning

confidence: 99%

Use of near‐infrared spectroscopy to identify trends in regional cerebral oxygen saturation in horses

McConnell

Rioja

Bester

et al. 2012

Equine Veterinary Journal

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Summary Reasons for performing study Alterations in cerebral haemodynamics may contribute to perianaesthetic complications in horses. Near‐infrared spectroscopy (NIRS) is frequently used intraoperatively in man to provide information regarding cerebral perfusion. Objectives To determine whether NIRS can identify trends in regional cerebral oxygen saturation (rSO2) in horses and whether there is a correlation between rSO2 and venous oxygen tensions. Methods A cerebral oximeter sensor recorded rSO2 from the dorsal sagittal sinus of 6 healthy horses. Values for rSO2, arterial and venous oxygen and carbon dioxide tensions (PaO2, PvO2, PaCO2 and PvCO2 respectively), along with arteriovenous oxygen saturations (SavO2) were recorded in unsedated (recording period [RP] 1), sedated (RP2) and anaesthetised horses (RP3–5) and during recovery (RP6–8). During anaesthesia, horses were ventilated to achieve states of normo‐ (RP3), hyper‐ (RP4) and hypocapnoea (RP5). Data were evaluated descriptively and analysed using linear mixed‐effects models and Pearson's correlation coefficient. Results Overall mean ± s.d. values for rSO2, PaO2, PvO2, PaCO2, SavO2 and mean arterial pressure varied significantly by RP (P<0.001). Significant decreases in rSO2 were identified between RP1 and the post anaesthetic periods (P<0.001). No significant differences in rSO2 values were identified between RP1 and the intra‐anaesthesia periods or between RP3, RP4 and RP5. Significant correlations were identified between rSO2 and PaO2 (r = 0.448, P<0.001), rSO2 and PvO2 (r = 0.512, P<0.001) and rSO2 and SavO2 (r = 0.469, P<0.001). Conclusions This is the first study to identify trends in rSO2 in horses using NIRS. A positive correlation was identified between rSO2 and PvO2, suggesting that alterations in cerebral oxygenation may be reflected in PvO2. Potential relevance Near‐infrared spectroscopy may be used to monitor trends in rSO2 during equine anaesthesia. Decreasing rSO2 values may act as an early warning signal, alerting clinicians to potential cerebral desaturation events and indicating a need for intervention.

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Direct measurement of intracranial pressure in adult horses

Cited by 33 publications

References 26 publications

Central Nervous System Trauma

Central Nervous System Trauma

Anesthetic Considerations for Horses with Neurologic Disease

Use of near‐infrared spectroscopy to identify trends in regional cerebral oxygen saturation in horses

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