Prolonged hypoxemia and acidemia in anesthetized pigs: a model for research on extracorporeal organ support in an intensive care setting.
OBJECTIVE
Hypoxemia and acidemia (hypoxemia/acidemia) are serious complications in the critically ill and often occur in unstable patients exposed to extracorporeal organ support. Still, little is known about the biocompatibility interactions of hypoxemia/acidemia with extracorporeal circuits (ECC). Existing animal models often include the release of mediator cascades (sepsis-, lung injury models) or are based on small laboratory animals. We established a porcine model of hypoxemia/acidemia without an underlying disease and further challenged the situation with an extracorporeal circuit (ECC).


METHODS
Hypoxemia/acidemia were induced (3.5 h) and maintained (3 h) in anesthetized pigs (40 kg) by a stepwise reduction in oxygenation, infusion of 0.4 mol.l⁻¹ lactic and hydrochloric acid and by low tidal volume ventilation, targeting an PaO₂ < 70 mmHg, SvO₂ < 65%, pH ~ 7.2. Venovenous hemofiltration (CVVH) operated in recirculation mode without volume exchange was chosen to prove the suitability of the model for studies on ECCs under clinical conditions (ECC group, n=6). Another 6 animals underwent the same protocol except for the CVVH (reference group, n=6).


RESULTS
The median PaO₂ during hypoxemia/acidemia was 62 mmHg, the median SvO₂ was 38%, and the median pH was 7.22. Hypoxemia/acidemia was successfully induced and maintained for 6.5 h in all pigs. CVVH could be performed for 3 h with blood flow rates up to 300 ml.min⁻¹ and filtrate rates up to 60 ml.min⁻¹.


CONCLUSIONS
Our model provides hypoxemia/acidemia with blood gas values comparable to critically ill adult patients for several hours, during which it is possible to perform CVVH. Thus, it enables research on the biocompatibility reactions of extracorporeal circuits under intensive care conditions.
Russ
Martin
M
Department of Experimental Medicine (FEM), Charité - Campus Virchow, Humboldt University, Berlin, Germany.
Ott
Sascha
S
Bedarf
Janis R
JR
Haacke
Nadine
N
Keckel
Tobias
T
Unger
Juliane K
JK
D000138:Acidosis / Q000097:blood / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D000768:Anesthesia, General; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D003422:Critical Care; D004195:Disease Models, Animal; D005112:Extracorporeal Circulation; D006439:Hemodynamics; D006440:Hemofiltration; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000097:blood / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D013552:Swine; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen