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The effect of body position on intracranial and intraocular pressure in cats

Introduction: There are contradictory reports about relationship of intracranial and intraocular pressure (IOP). Intracranial pressure is measured invasively in patients with intracranial hypertension, while IOP is determined by less precise noninvasive methods. For this reason we compared intracranial pressure and IOP measured by invasive tehniques in new experimental model in cats during changes of body position. Material and Methods: Experiments were performed on adult cats anaesthetized with chloralose (100 mg/kg i.p. ; n=10). The stainless steel cannulae (o.d. 0.9 mm) were introduced into lateral ventricle (LV), cortical (CSS) and lumbar (LSS) subarachnoid spaces, and in anterior ocular chamber of right eye. The cannulae were connected to pressure transducers, and intraural line was taken as reference zero (0 cm H2O) pressure. The animals and measuring instruments were fixed on board and pressures were measured in horizontal and vertical position. Results: In horizontal position pressure in eye ( IOP = 18.5 ± 0.6 cm H2O) and pressures in cerebrospinal fluid (LV = 17.4 ± 0.9 ; CSS = 17.2 ± 0.7 ; LSS = 17.8 ± 1.2 cm H2O) were similar and did not differ significantly (p>0, 05). In vertical position lumbar pressure increased (LB = 33.5± 2.3 cm H2O), pressures in cranial cavity fell to subatmospheric value (LV = -4.1± 0.9 cm H2O ; CSS = -4.8± 0.5 cm H2O) while intraocular pressure showed small decrease (IOP =14.3± 0.1 cm H2O). Conclusion: It appears that change of body position from horizontal to upright position causes drastic changes of pressures in different parts of cerebrospinal fluid system, while pressure change in ocular fluid is relatively small. Our results indicate that in animals without intracranial hypertension, the intraocular and intracranial pressures are not importantly interconnected.

body position ; cats ; intracranial pressure ; intraocular pressure

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