Intracranial pressure monitoring in normal dogs using subdural and intraparenchymal miniature strain‐gauge transducers

Abstract

Background Monitoring of intracranial pressure (ICP) is a critical component in the management of intracranial hypertension. Safety, efficacy, and optimal location of microsensor devices have not been defined in dogs. Hypothesis/Objective Assessment of ICP using a microsensor transducer is feasible in anesthetized and conscious animals and is independent of transducer location. Intraparenchymal transducer placement is associated with more adverse effects. Animals Seven adult, bred‐for‐research dogs. Methods In a prospective investigational study, microsensor ICP transducers were inserted into subdural and intraparenchymal locations at defined rostral or caudal locations within the rostrotentorial compartment under general anesthesia. Mean arterial pressure and ICP were measured continuously during physiological maneuvers, and for 20 hours after anesthesia. Results Baseline mean ± SD values for ICP and cerebral perfusion pressure were 7.2 ± 2.3 and 78.9 ± 7.6 mm Hg, respectively. Catheter position did not have a significant effect on ICP measurements. There was significant variation from baseline ICP accompanying physiological maneuvers (P < .001) and with normal activities, especially with changes in head position (P < .001). Pathological sequelae were more evident after intraparenchymal versus subdural placement. Conclusions and Clinical Importance Use of a microsensor ICP transducer was technically straightforward and provided ICP measurements within previously reported reference ranges. Results support the use of an accessible dorsal location and subdural positioning. Transient fluctuations in ICP are normal events in conscious dogs and large variations associated with head position should be accounted for when evaluating animals with intracranial hypertension.

Intraoperative measurement of intraventricular pressure in dogs with communicating internal hydrocephalus

“…Most inhalant anaesthetics cause a minimal-to-moderate increase in ICP [58–60], which may bias its measurement during VPS surgery. However, non‐anaesthetised dogs had mean ICPs in a range consistent with values of previous reports in dogs under general anaesthesia [28], suggesting a minimal effect of these agents. Alteration of cerebral perfusion pressure, which in turn is dependent on mean arterial blood pressure, has a major effect on ICP.…”

“…Consistent values have also been measured in anaesthetised, clinically sound, dogs using ventricular ICP measurements [55] as compared to intraparenchymal-, [28, 56], or cisterna magna measurements [31, 57]. The Codman MicroSensor has been shown to provide reliable and accurate ICP measurements in dogs [28]. We have measured IVP under general anaesthesia.…”

“…Intraparenchymal pressure monitoring provides equivalent measurements when compared to intraventricular assessment, which is in fact the gold-standard for ICP monitoring in humans [51–54]. Consistent values have also been measured in anaesthetised, clinically sound, dogs using ventricular ICP measurements [55] as compared to intraparenchymal-, [28, 56], or cisterna magna measurements [31, 57]. The Codman MicroSensor has been shown to provide reliable and accurate ICP measurements in dogs [28].…”

“…IVP is a dynamic parameter and measurement at one time-point only represents a snapshot. ICP measurements in awake dogs were found to differ depending on head position [28]. Mean values for ICP increased by >100% comparing head elevation to head down positions [28].…”

Spontaneous hemispheric ventricular collapse and subarachnoid haemorrhages in a dog with congenital hydrocephalus internus

“…Another theory regarding sudden change in the intracranial pressure is the head and body position. The effect of the head and body position and changes in the mean ICP have been recently examined using subdural and intraparenchymal miniature strain-gauge transducers in healthy dogs [26]. Head down positioning was correlated with an increase in ICP.…”