Physiological Assessment in Stroke Research - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 71

of MK-801, thought to be due to modulation of excitotoxicity,
may have actually been explained by MK-801's ability to lower
body temperature ( 14 ).
Over the last decade, the “classic” physiological techniques,
such as hemodynamic monitoring, blood fl ow analysis, and others
have been challenged by molecular approaches to physiology as
well as large-scale “functional” techniques, such as FDG-PET or
NMR spectroscopic studies of metabolism. We agree that these are
excellent tools and they shed light on important basic and clinical
phenomena. However, although such techniques are being increas-
ingly utilized in both basic and clinical research, the generated data
is not a surrogate for standard physiological variables. Furthermore,
given their limited practicality and limited availability in most clini-
cal and basic research settings, these highly specialized techniques
are usually limited to few specialized academic centers and rarely
impact the standard care of stroke patients. This chapter focuses on
those common physiologic techniques used in both basic science
studies and in the clinical care of ischemic and hemorrhagic stroke.
We cover techniques of blood pressure and heart rate monitoring,
cerebral blood fl ow, temperature monitoring, and a collection of
basic laboratory studies.
2. Blood Pressure
Measurement
Blood pressure monitoring during the induction of experimental
stroke in animal models is critical due to its direct impact on cortical
infarct size, development of edema, and the overall neurologic out-
come. The monitoring and treatment of blood pressure changes are
an area of specifi c focus in the American Heart Association and
American Stroke Association guidelines for both acute ischemic
infarction and intracerebral hemorrhage ( 15, 16 ). Thus, determin-
ing blood pressure throughout an experimental stroke study (before,
during, and after stroke induction) is a key component of reducing
infarct variability and also maintaining ecological validity.
Blood pressure fl uctuates throughout the day in most laboratory
animals due to diurnal variations (Table 2 ). In most nocturnal rodent
species, the peak arterial blood pressure is typically observed both
early and late during the dark period, with nadir occurring mid-way
through the light period ( 17 ). This is likely due to the systemic adjust-
ment to metabolic demands of foraging activity and food intake. The
effect of ambient temperature on cardiovascular parameters, includ-
ing blood pressure, must also be considered. In mice, as the tempera-
ture decreases by 1°C, blood pressure and heart rate increase by
1.6 mmHg and 14.4 bpm, respectively. Rats have a similar response
with an increase in blood pressure and heart rate of 1.2 mmHg and
8.1 bpm for every 1°C decrease in ambient temperature ( 18 ).