TYK87
All of the following are known effects of NITROUS OXIDE administration EXCEPT:
A. Systemic (peripheral) vasoconstriction
B. More severe increase in PVR in the setting of baseline PVR elevation
C. Direct myocardial depression via dose related reductions in intracellular calcium
D. PVR increases blunted by halothane administration
E. Minimal (non-clinically significant) increase in PVR in patients with normal PVR at baseline
Answer
The answer is D.
First of all, if you read this as NITRIC oxide, go ram your head into a wall, because I even capitalized it for you. Enough of the touchy feely stuff.
All of the following are correct except D.
Nitrous oxide is known to cause myocardial depression and systemic vasoconstriction secondary to alpha adrenergic stimulation. Several reports show a greater increase in PVR (greater slope of increase) in patients with a severely elevated PVR at baseline (think of the SEVERE pulmonary hypertension patient). This elevation is not reversed or blunted by volatile anesthetics. Minimal increases in PVR are noted when the patient has a normal to slightly elevated PVR (think of the moderate pulmonary hypertension patient). Bottom line is to avoid it when the patient has severe pulmonary hypertension as it will not only elevate the PVR, but also decrease the RV function (which is probably not so great to begin with).
Many tools in the shed, pick a sharper one...
This, however, may not quite be the case in pediatrics. A study in children with CHD and mild to moderately elevated PVR did not show an increase in shunting or PVRI. However, they did show a decrease in systemic hemodynamics similar to adult studies.