Accuracy of mucosal pH and mucosal-arterial carbon dioxide tension for detecting mesenteric hypoperfusion in acute canine endotoxemia.
OBJECTIVE
To determine the level of mucosal-arterial Pco2 (Pco2 gap) that is both sensitive and specific for the detection of mesenteric hypoperfusion as defined by either a >50% reduction in portal blood flow or release of lactate by the gut.


METHODS
Animal experiment.


METHODS
Seven anesthetized, intubated, mechanically ventilated, and surgically instrumented mongrel dogs.


METHODS
Escherichia coli endotoxin (1 mg/kg) given intravenously for 5 mins.


RESULTS
Tonometric Pco2, arterial blood gases, arterial and portal venous lactates, and portal and systemic hemodynamic variables were measured. Mucosal pH (pHi) was calculated according to the manufacturers' instructions. From these data, receiver operating characteristics were calculated. Although animals were resuscitated to maintain a constant cardiac output, portal flow decreased from 350+/-101 to 152+/-75 mL/min (p<.01) and the gut released lactate into the portal circulation in all animals. Pco2 gap increased from 13.1+/-3.9 to 40.2+/-39.2 torr (p<.01) and was inversely correlated with portal blood flow (r2 = .20; p<.05). For detection of a >50% reduction in portal blood flow, a Pco2 gap of 20 torr yielded a maximum accuracy of 67% (sensitivity, 55%; specificity, 73%) and was less accurate than a pHi of 7.20, which yielded a maximum accuracy of 76% (sensitivity, 90%; specificity, 70%), although this difference was not significant (p = .24). There was also a correlation between pHi and portal blood flow (r2 = .31; p<.01). For detection of lactate release by the gut, a Pco2 gap of 20 torr was also 67% accurate (sensitivity, 53%; specificity, 78%), whereas a pHi of 7.10 achieved an accuracy of 64% (sensitivity, 40%; specificity, 83%), which was not significantly different.


CONCLUSIONS
Pco2 gap measurements are neither sensitive nor specific for mesenteric hypoperfusion with regard to total gut blood flow reductions of >50% or the release of lactate into the portal circulation.
Kellum
J A
JA
Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh Medical Center, PA, USA.
Rico
P
P
Garuba
A K
AK
Pinsky
M R
MR
D000818:Animals; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000032:analysis*; D004195:Disease Models, Animal; D004285:Dogs; D019446:Endotoxemia / Q000150:complications*; D004927:Escherichia coli Infections / Q000150:complications*; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D007511:Ischemia / Q000175:diagnosis* / Q000378:metabolism* / Q000382:microbiology / Q000503:physiopathology; D019344:Lactic Acid / Q000097:blood; D008102:Liver Circulation; D008297:Male; D008643:Mesentery / Q000098:blood supply*; D009092:Mucous Membrane / Q000737:chemistry*; D010101:Oxygen Consumption; D011168:Portal System; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002245:Carbon Dioxide; D019344:Lactic Acid