Intestinal permeability, gastric intramucosal pH, and systemic endotoxemia in patients undergoing cardiopulmonary bypass.
OBJECTIVE
To examine the relationship between gastric intramucosal pH, intestinal permeability, endotoxemia, and oxygen delivery in patients undergoing cardiopulmonary bypass (CPB).


METHODS
Prospective, observational study.


METHODS
Tertiary care center.


METHODS
Fifty patients undergoing elective cardiac surgery and 10 patients awaiting elective cardiac surgery.


METHODS
Patients received chromium 51-labeled ethylenediaminetetraacetic acid (51Cr-EDTA) as a marker of intestinal permeability; insertion of a nasogastric tonometer to measure intramucosal pH (pHi); insertion of a pulmonary artery catheter to measure systemic oxygen delivery and consumption variables; arterial blood sampling for plasma endotoxin by the Limulus amebocyte lysate assay; and blood and urine sampling for measurement of 51Cr-EDTA.


METHODS
Systemic oxygen delivery, duration of gastric mucosal acidosis, absorption of 51Cr-EDTA, appearance of systemic endotoxemia, renal dysfunction, and duration of hospital stay.


RESULTS
Median (range) 24-hour urinary recovery of 51Cr-EDTA in patients was 10.6% (2.1% to 40.2%) while that in controls was 1.2% (0.7% to 2.0%, P<.001). Intestinal permeability increased during CPB. The median (range) for the lowest pHi after bypass was 6.98 (6.74 to 7.17). The pHi did not decline until CPB was discontinued and the heart took over the load of the circulation. Endotoxin was detectable (>0.2 endotoxin unit per milliliter) in the plasma of 21 patients (42%) during the study, most of whom were endotoxemic by the end of CPB. There was no evident relationship between the degree of gut permeability, endotoxemia, gut ischemia, or systemic oxygen dynamics.


CONCLUSIONS
Cardiopulmonary bypass is associated with increases in gut permeability, which precede gut mucosal ischemia. In cardiac surgical patients, a low pHi is not necessarily indicative of an adverse clinical outcome. Endotoxemia as measured by the Limulus amebocyte lysate assay is common. The increased intestinal absorption of 51Cr-EDTA and gastric mucosal acidosis occur as independent phenomena and are not related in severity or time of onset.
Riddington
D W
DW
Department of Anaesthesia and Intensive Care Medicine, University of Birmingham, United Kingdom.
Venkatesh
B
B
Boivin
C M
CM
Bonser
R S
RS
Elliott
T S
TS
Marshall
T
T
Mountford
P J
PJ
Bion
J F
JF
D000138:Acidosis; D000328:Adult; D000368:Aged; D000771:Anesthesia, Intravenous; D001784:Blood Gas Analysis; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D004492:Edetic Acid; D017558:Elective Surgical Procedures; D004731:Endotoxins / Q000032:analysis*; D005260:Female; D005753:Gastric Mucosa / Q000098:blood supply / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007511:Ischemia; D008033:Limulus Test; D008297:Male; D008875:Middle Aged; D009102:Multiple Organ Failure / Q000209:etiology; D010101:Oxygen Consumption; D010539:Permeability; D011183:Postoperative Complications; D011446:Prospective Studies; D014115:Toxemia / Q000175:diagnosis / Q000209:etiology*
D004731:Endotoxins; D004492:Edetic Acid