A Comparison of Gastric and Rectal CO₂ in Cardiac Surgery Patients

Newer monitoring techniques to determine the risk of necrotizing enterocolitis

Necrotizing enterocolitis affects up to 10% of neonates who are born weighing less than 1500 g. It has a high rate of morbidity and mortality, and predicting infants who will be affected has so far been unsuccessful. In this article, a number of new methods are discussed from the literature to determine if any currently available techniques may allow for the identification of patients who are at increased risk for developing this potentially lethal disease.

Monitoring technologies in the neonatal intensive care unit: implications for the detection of necrotizing enterocolitis

Necrotizing enterocolitis is the most common and fulminant gastrointestinal disease affecting neonates. Its pathogenesis is heterogeneous and not clearly understood. Early detection could prevent some of the devastating consequences of this disease, but currently there is no noninvasive method of reliable early-stage detection. Here, we review various noninvasive monitoring technologies that have already been employed or show promise for early detection. Each method may have an important role after its technical difficulties are resolved. These are discussed in detail as they relate to various aspects of the putative pathophysiology of this devastating disease.

Rectal lactate levels in endoluminal microdialysate during routine coronary surgery

The aim of this prospective study was to determine the feasibility of intestinal endoluminal microdialysis as a new method for clinical monitoring of the adequacy of splanchnic perfusion in the large bowel. A microdialysis catheter for continuous lactate, glycerol, glucose and pyruvate measurements attached to a tonometric catheter was placed into the lumen of the recto-sigmoid junction prior to surgery in 13 patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB). Lactate was also measured in blood and muscle. CPB was associated with a 10-fold increase in luminal lactate from 0.16 (0.01) to 1.67 (0.38) mmol x l(-1) (p < 0.001). Muscular lactate increased from baseline levels 1.20 (0.21) to 1.77 (0.36) mmol x l(-1) during CPB (p = 0.01), but the muscular lactate-pyruvate ratio remained unchanged. Arterial lactate increased only slightly from 0.9 (0.05) to 1.1 (0.06) mmol x l(-1) (p = 0.027) during CPB. Increased lactate concentrations in the large bowel during CPB are suggestive of local lactate production consistent with impaired oxygen delivery. Intestinal endoluminal microdialysis is a potential clinically applicable method for monitoring intestinal metabolism. Combined with tonometry, microdialysis provides the opportunity to monitor both circulation and metabolism in the rectal mucosa.

Gut dysoxia: comparison of sites to detect regional gut dysoxia

Dysoxia, a state in which O2 supply is inadequate to meet tissue metabolic needs, is often first detected in regional organs such as the gut. An increase in PCO2 is believed to reflect the development of gut dysoxia. The stomach is a well-documented clinical site for detecting gut PCO2; however, measurement issues make this a less than ideal monitoring site. Other sites along the GI tract may be equally sensitive to detect changes in PCO2. Rectal CO2 measurement may have the advantage of being less invasive, low risk, and continuous without the limitations associated with gastric monitoring. In this study, we compared PCO2 at two sites (gastric, rectum) at baseline and during a dysoxic challenge, cardiac arrest. We obtained similar values of PCO2 at both sites. Ten male Wistar rats were anesthetized with 1%-2% Isoflurane/50% nitrous oxide/balanced O2 and the tail artery and right atrium were cannulated. Severinghaus-type active tip PCO2 electrodes (Microelectrode Inc, Bedford, NH) were calibrated and one electrode was surgically inserted into the stomach (G-PCO2) and a second electrode was placed in the rectum (R-PCO2). Animals were stabilized following surgery. Cardiac arrest was induced by administering a rapid injection of norcuron (0.1-0.2 mg/kg) and potassium chloride solution (0.5 M/L; 0.12 mL/100 gm of body weight). Animals were monitored for 15 minutes post-arrest. Data were collected at one minute intervals using the software Data Collect. All data are reported as mean +/- SD. Baseline G-PCO2 was 64 +/- 17 torr, not significantly different from R-PCO2, 58 +/- 7 torr. After 15 minutes of cardiac arrest, G-PCO2 rose to 114 +/- 42 torr, again not significantly different from R-PCO2, which reached 112 +/- 35 torr. Monitoring PCO2 in the rectum is less invasive and might provide similar information when compared with gastric monitoring at baseline and during a dysoxic challenge.