ABSTRACT
Searching for the early warning symptoms of brain ischaemia, transcranial Doppler sonography (TCD) was used in cats during the Cushing response. The study was performed on seven cats. The intracranial pressure was increased by means of different rate lumbar infusions. The TCD changes of middle cerebral artery (MCA) and basilar artery (BA) flows were analyzed at the stage of the slightest but significant systemic blood pressure increase. The first symptoms of Cushing phenomenon were accompanied by BA flow pattern alternations while the MCA flow remained unchanged. The study suggests the necessity of BA TCD monitoring in cases at risk from brain stem ischaemia. It was shown also that in such cases the MCA TCD study can be misleading.
Subject(s)
Adrenergic Fibers/physiology , Blood Pressure/physiology , Brain Damage, Chronic/diagnostic imaging , Brain Ischemia/diagnostic imaging , Brain Stem/blood supply , Intracranial Pressure/physiology , Ultrasonography, Doppler, Transcranial , Animals , Basilar Artery/diagnostic imaging , Blood Flow Velocity/physiology , Cats , Cerebral Arteries/diagnostic imaging , Male , Pulsatile Flow/physiologyABSTRACT
Standardized volume-pressure craniospinal system loadings based on physiological loadings were developed in order to study the CSF outflow route efficiency and to evaluate the intracranial volume-pressure relations. The study was carried out on 10 cats. Standardized abdominal compression was applied in order to produce a central venous pressure increased and subsequently ICP increase to the level of 20 and 30 mmHg for 2 minutes. The abdominal compression test seems to be useful in the CSF outflow route evaluation. The orthostatic changes were studied in control animals and in cats with an epidural balloon. The animal body was evaluated to an angle of 50 degrees and 80 degrees with the head directed upwards and downwards. This test was found suitable for the intracranial volume reserve estimation. Similar application, especially in experimental conditions can be found in the hypercapnia test. PaCO2 concentration was increased by means of respiration with a gas mixture containing 5% CO2. A steady increase of ICP of 9 +/- 1 mmHg was obtained. Vascular dilatation resulted in an intracranial volume loading. The ICP response in subjects with normal CO2 response can be related to the intracranial volume reserve. The studies performed show the usefulness of the standardized volume-pressure loadings. The loadings applied are more physiological than lumbar infusion tests used so far.
Subject(s)
Carbon Dioxide/blood , Central Venous Pressure/physiology , Intracranial Pressure/physiology , Valsalva Maneuver/physiology , Animals , Cats , Homeostasis/physiology , Male , Respiration/physiologyABSTRACT
A new CSF circulation diagnostic procedure is presented. The method is called three-phase infusion test. In phase I the CSF absorption mechanisms were tested within ICP range below 20 mmHg and then the infusion rate of 0.06 ml/min was applied. In phase II the high infusion rate (0.3 ml/min) was used and high ICP increase occurred. This part of the study provided data concerning the ability of alternative CSF outflow routes. In phase III again low infusion rate (0.06 ml/min) was applied. The obtained CSF outflow data in phase III were significantly lower than in phase I. This is the so called persistent outflow facilitation phenomenon. The method described, covering different mechanisms of CSF absorption, enables the complex evaluation of CSF outflow sufficiency.
Subject(s)
Cerebrospinal Fluid/physiology , Animals , Cats , Cerebrospinal Fluid Pressure/physiology , Intracranial PressureABSTRACT
Intracranial pressure (ICP) pulse wave was analysed during infusion tests performed in hospital (hydrocephalus) and in cats. Pulse wave changes were evaluated calculating the high frequency centroid index (HFC) in the HFC, found to be a very valuable parameter in intracranial volume-pressure situation evaluation. The HFC decrease occurred much earlier than the rise of ICP in both clinical and experimental studies. Thus the HCF index should be very usefull in clinical evaluation of intracranial volume-pressure relation disturbances.
Subject(s)
Hydrocephalus/diagnosis , Intracranial Pressure , Adolescent , Animals , Cats , Child , Child, Preschool , HumansABSTRACT
The effects of physiological loadings (venous pressure increase, postural changes, pCO2 increase) on intracranial volume-pressure relations were studied. The standardized increase of venous outflow pressure was found to be a good test for the evaluation of CSF outflow routes. Standardized venous outflow pressure increase in Queckenstedt test seems to be especially useful.
Subject(s)
Brain/physiopathology , Hydrocephalus/physiopathology , Intracranial Pressure , Adult , Cerebrospinal Fluid Pressure , Humans , Hydrocephalus/diagnosis , Middle AgedABSTRACT
ICP waves were analysed in the situation of expanding intracranial mass. The aim of the study was to determine how big the intracranial added volume has to be in order to produce significant changes of harmonic disturbances index (HFC) of ICP pulse waves. The diagnostic value of HFC and other parameters was compared. The following other parameters were studied: intracranial pressure (ICP), CSF outflow resistance (R), volume pressure response (VPR) and visual evoked potentials (VEP). It was found that ICP wave analysis very clearly reflects the intracranial volume-pressure relation changes.
Subject(s)
Intracranial Pressure , Animals , Catheterization , Cats , Cerebrospinal Fluid Pressure , Evoked Potentials, VisualABSTRACT
Intracranial pressure (ICP) was elevated in cats by intrathecal infusions. Middle cerebral artery and basilar artery were studied using Transcranial Doppler (TCD) during the infusion followed by systemic arterial pressure increase (Cushing response). Cushing response was symptomatic for brain stem ischaemia. The earliest TCD changes concerned the basilar artery. The most informative data for the diagnosis were pulsatility index increase and diastolic velocity decrease.
Subject(s)
Brain Ischemia/diagnosis , Brain Stem/physiopathology , Ultrasonography, Doppler, Transcranial/methods , Animals , Basilar Artery , Brain Ischemia/physiopathology , Brain Stem/blood supply , Cats , Cerebral Arteries , Intracranial Pressure , MaleABSTRACT
In experimental studies on cats the pressure and volume loadings corresponding to the physiological situations were used. The following tests were applied: central venous pressure increase, postural changes and increase of CO2 percentage in inspired gas mixture. It was found that the central venous pressure increase test is useful in the evaluation of CSF outflow routes, the postural change test examines the intracranial compensation and the elevation of CO2 level in inspired air tests the intracranial volume reserve.
Subject(s)
Carbon Dioxide , Cerebrospinal Fluid/physiology , Intracranial Pressure , Posture , Respiration , Animals , Carbon Dioxide/pharmacology , Cats , Central Venous Pressure , Cerebrospinal Fluid Pressure , Intracranial Pressure/drug effects , Male , Monitoring, Physiologic/instrumentation , Signal Processing, Computer-AssistedABSTRACT
Lumbar infusion tests (IT) with different infusion rates (0.06 ml/min-1.2 ml/min) were used in order to investigate the intracranial pressure (ICP) and CSF outflow resistance (R) changes. Two groups of animals were studied: control group and animals with an 0.8 ml epidural balloon. In control group (without balloon) significant differences in ICP and R values between the increasing and decreasing IT curve were found. The most pronounced changes were noticed right after the highest infusion rate (40% for ICP value and 49% for R value). The results in the balloon group were very similar and the only difference were delayed ICP and R changes. The results obtained suggest that the determined R values are specific for the applied infusion rate and this phenomenon has to be taken into account in all human studies.
Subject(s)
Cerebrospinal Fluid Pressure/physiology , Cerebrospinal Fluid/physiology , Models, Neurological , Animals , Cats , Cerebrospinal Fluid/drug effects , Cerebrospinal Fluid Pressure/drug effects , Epidural Space/drug effects , Infusions, Parenteral/methods , Sodium Chloride/administration & dosage , Sodium Chloride/pharmacology , Spinal Canal/drug effects , Time FactorsABSTRACT
The Cushing response was produced using the lumbar infusions in cats. The following parameters were recorded and computed: arterial blood pressure (ABP), central venous pressure (CVP), intracranial pressure (ICP), heart rate and ECG. The lactate concentration was studied in brain stem and brain cortex. The analysis of ABP and ICP recordings showed in some cases that the Cushing response was obtained at CPP over 60 mmHg. The role of adrenergic reaction in Cushing phenomenon was confirmed by the increase in blood catecholamine concentration and typical adrenergic changes in ECG pattern.
