Effect of sodium nitroprusside-induced hypotension on pulmonary deadspace.

Deliberate hypotension with nitroprusside produced a 40% reduction in mean arterial pressure, but it did not cause any change in the pulmonary deadspace to tidal volume ratio ( Vb/ Vr). This was achieved by adequate hydration both before and during hypotension, as indicated by constant filling pressures. Thus we have shown that deliberate hypotension per se does not increase Vb/ VT, and that vasodilataaon may bring about a relatively hypovolaemic state and be responsible for the increase in Vb/ VT observed by previous workers