The influence of hyperoxic ventilation during sodium nitroprusside-induced hypotension on skeletal muscle tissue oxygen tension.
BACKGROUND
Increasing inspired oxygen concentrations might provide a simple and effective intervention to increase oxygen tension in tissues during controlled hypotension. To test this hypothesis, the influence of hyperoxic ventilation (100% O2) on skeletal muscle oxygen partial pressure (Ptio2) in patients receiving sodium nitroprusside-induced controlled hypotension was studied.


METHODS
Forty-two patients undergoing radical prostatectomy were prospectively studied and randomly divided into three groups as follows: (1) Controlled hypotension induced by sodium nitroprusside (mean arterial blood pressure, 50 mmHg) and hyperoxic ventilation (CH-100%; n = 14); (2) controlled hypotension and ventilation with 50% O2 in nitrous oxide (CH-50%; n = 14); and (3) standard normotensive anesthesia with 50% O2 in nitrous oxide (control; n = 14). Ptio2 values were measured continuously in all patients using implantable polarographic microprobes. Arterial blood gases and lactate concentrations were analyzed in 30-min intervals.


RESULTS
Surgical blood loss and transfusion requirements were significantly reduced in both groups receiving hypotensive anesthesia. During surgery, arterial partial pressure of oxy-gen and arterial oxygen content were significantly higher in patients of the CH-100% group. Baseline values of Ptio2 were comparable between the groups (CH-50%: 25.0 +/- 0.7 mmHg; CH-100%: 25.2 +/- 0.2 mmHg; control: 24.5 +/- 0.2 mmHg). After a transient increase in Ptio2 in the CH-100% group during normotension, Ptio2 values returned to baseline and remained unchanged in the control group. Ptio2 decreased significantly during the hypotensive period in the CH-50% group. The lowest mean Ptio2 values were 15.0 +/- 4.1 mmHg in the CH-50% group, 24.2 +/- 4.9 mmHg in the CH-100% group, and 23.5 +/- 3.8 mmHg in the control group. There were no significant changes in lactate plasma concentrations in any group throughout the study period.


CONCLUSIONS
Hyperoxic ventilation improved skeletal muscle tissue oxygenation during sodium nitroprusside-induced hypotension. This improved local tissue oxygenation seems to be most likely due to an increase in convective oxygen transport and the attenuation of hyperoxemia-induced arteriolar vasoconstriction by sodium nitroprusside.
Suttner
Stefan W
SW
Department of Anesthesiology and Intensive Care Medicine, Klinikum der Stadt Ludwigshafen, Ludwigshafen, Germany. sutner@gmx.de
Lang
Katrin
K
Boldt
Joachim
J
Kumle
Bernhard
B
Maleck
Wolfgang H
WH
Piper
Swen N
SN
D000368:Aged; D000758:Anesthesia; D018685:Anesthetics, Inhalation; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001784:Blood Gas Analysis; D000077335:Desflurane; D006801:Humans; D007023:Hypotension, Controlled / Q000009:adverse effects*; D007530:Isoflurane / Q000031:analogs & derivatives; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D010102:Oxygen Inhalation Therapy; D011048:Polarography; D011468:Prostatectomy
D018685:Anesthetics, Inhalation; D000959:Antihypertensive Agents; D009599:Nitroprusside; D000077335:Desflurane; D007530:Isoflurane; D010100:Oxygen