Intravascular aggregation after acute intracranial hypertension by epidural balloon compression in cats

Evaluation of intracranial pressure by transcranial Doppler ultrasonography in dogs with intracranial hypertension

Transcranial Doppler ultrasonography (TCD) has been used to confirm changes in cerebral hemodynamics. In this study, we investigated whether the parameters for the basilar artery measured by TCD were correlated with the intracranial and cerebral perfusion pressures in extreme intracranial hypertension. An intracranial hypertension model was produced in seven dogs by inflating a balloon inserted into the epidural space. The resistance index was compared with the corresponding intracranial pressure and cerebral perfusion pressure values during intracranial hypertension. A significant correlation was recognized between the resistance index and cerebral perfusion pressure. Therefore, measurement of the basilar artery by TCD in the dog with intracranial hypertension is useful in estimating the intracranial circulation in cases where the measurement of intracranial pressure is not available or not indicated.

Somatosensory evoked potentials and intracranial pressure during chronic dilatation of an artificial extraparenchymal space-occupying lesion in cats

Somatosensory evoked potentials (SEP) and intracranial pressure (ICP) were studied in cats, suffering from a chronic space-occupying lesion produced by enlargement of an epidural balloon over the left sensomotory cortex. Our study shows that latency alterations of SEP are not dependent on the degree of ICP. Additionally, the results obtained demonstrate that chronic space-occupying lesions cause continuous prolongation of SEP latencies, probably produced by atrophy of the compressed tissue. Regarding the clinical importance of SEP measurements, we concluded that they are not suitable for estimating the degree of ICP. However, they are useful to evaluate tissue damage caused by mass effects in the acute and chronic phase of various space-occupying processes.

Changes of somatosensory evoked potentials with increase of intracranial pressure in the rat's brain

Somatosensory evoked potentials (SEPs) to various combinations of two independent brain compression modalities (localized epidural pressure and intracerebral pressure evoked by an inserted balloon) were investigated in 24 rats. The SEP pattern in response to gradually expanding volume without additional epidural pressure remained unchanged for a certain period. SEP changes occurred only shortly prior to death. On the other hand, remarkable SEP changes were observed in a gradually expanding intracerebral mass, when combined with epidural pressure application at about 50% of the lethal volume. SEP changes in response to intermittent and continuous epidural pressure, in addition to a small intracerebral mass, were investigated too. Intermittent application of minor epidural pressure led to specific P1 changes, which recovered after each pressure step. The same pressure, administered continuously, evoked SEP changes with only partial recovery in some instances. Severe epidural pressure, administered intermittently, gave rise to severe SEP changes with only partial recovery after each step. The same epidural pressure delivered continuously led to SEP changes with very small recovery. SEPs have proved to be a reliable method for signalling brain dysfunction corresponding to various modalities and degrees of intracranial pressure.

A controlled study of Dextran 40: effect on cerebral blood flow and metabolic rates in acute head trauma

A controlled double-blind evaluation of the effects of Dextran 40 at different concentrations on cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2) and cerebral lactate production (CMRLact) was carried out. We studied 40 patients in coma due to recent head injury. Concentrations of Dextran solution were not significantly related to variations in CBF and metabolic rate over the period of infusion. The lack of effect of the Dextran infusion may be explained by the absence of global brain ischemia in these patients at the time of the study. The very low initial CBF values were a consequence of brain metabolic depression and not a sign of global ischaemia. The rheological benefits of treatment with Dextran 40 in head injured patients should preferably be investigated using techniques which permit detection of local changes in CBF and metabolism.