Physiological Assessment in Stroke Research - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 80

potent vasodilatory effect of carbon dioxide. Some have suggested
that hypercarbia may have a neuroprotective effect related to the
increase in CBF and angiogenesis ( 36 ). On the other hand,
hypocapnia (increased respiratory rate leading to decrease pCO2)
may have a deleterious effect. The presence of either a respiratory
or metabolic acidosis may suppress normal neuronal function and
inhibit the production of cellular energy needed for metabolism
( 36, 37 ). Blood sampling is necessary for periodic measurement of
arterial blood gases for the above reasons. An alternative measure
of oxygenation, such as pulse oximetry, is widely used in human
stroke care, but it has not been validated in small animal models of
experimental stroke. Blood gas analysis requires a blood gas ana-
lyzer or a point of care device, such as the iSTAT ® .

4.3. Glucose Level
Measurement

Hyperglycemia exacerbates neuronal damage and, therefore, glu-
cose should be routinely monitored in experimental stroke models
( 38 ). In addition, many commonly used anesthetic agents, such as
halothane and isofl urane and those less commonly used, such as
ketamine, can rapidly alter blood glucose values ( 39 ). Laboratory
conditions may limit access to food for prolonged periods of time
leading to hypoglycemia as well. For these reasons, it is necessary to
monitor blood glucose levels before, during and after any experi-
mental stroke model, especially in models causing severe brain dam-
age. Blood glucose values can be obtained from a blood gas analyzer.
We argue that using a standard glucose meter provides very precise
readings, uses much less blood, and the results are instantaneous.

5. Local Cerebral
Blood Flow

Measurement of local cerebral blood fl ow (CBF) is of great impor-
tance to ensure the validity of the stroke model and the effi ciency
of the technique used for stroke induction. It is important, for
example, to show an 80-90% drop in relative local CBF, to be con-
sidered a successful stroke model.
The study of cerebral hemodynamics requires the ability to
measure blood fl ow throughout the vascular system of the brain
and spinal cord. An ideal measurement technique should be repro-
ducible, precise, sensitive to small alterations, and have clinical
applicability. Unfortunately, there is no single modality that offers
all these characteristics at the same time. However, advances in the
fi eld of imaging have provided techniques with high precision and
accuracy.
There are several methods for monitoring cerebral blood fl ow.
Some are more invasive than others and the choice of which modal-
ity to choose depends on the experimental design and outcome.