Biomedical subjects

T J Vandermeer

Publications and source records attributed to T J Vandermeer.

4 recordsLinked to original sources

PubMed1994

Intraluminal "balloonless" air tonometry: a new method for determination of gastrointestinal mucosal carbon dioxide tension.

OBJECTIVE: To determine if air introduced directly into the lumen of a hollow viscus can be used instead of fluid in a Silastic balloon to estimate gastrointestinal mucosal PCO2. DESIGN: Prospective, unblinded comparison of two methods of mucosal PCO2 measurement. SETTING: Animal surgery suite at a large, university-affiliated medical center. INTERVENTIONS: Standard, commercially available, tonometric catheters were positioned in the ileum (n = 4) or the stomach and ileum (n = 12) of anesthetized, immature Yorkshire swine. Using gas-tight purse-string sutures, plastic cannulas were inserted into the lumen of the stomach (n = 12) and the lumen of a 10-cm isolated segment of ileum (n = 16). Data were collected after equilibration periods of 30 or 60 mins. Before each equilibration period, the "air tonometers" (i.e., the lumens of the stomach and/or the isolated ileal segment) were lavaged with 200 mL (stomach) or 20 mL (ileum) of air. In group 1 (n = 4) and group 2 (n = 3), graded degrees of mesenteric hypoperfusion were achieved by mechanical mesenteric occlusion or pericardial tamponade, respectively. In group 3 (n = 8), graded degrees of respiratory acidosis were induced. At various intervals, PCO2 was determined simultaneously in arterial blood, gastric air, saline from the gastric tonometric balloon, ileal air, and saline from the ileal tonometric balloon. MEASUREMENTS AND MAIN RESULTS: In pigs with ischemia created by mesenteric vascular occlusion (group 1), there was a moderate correlation between PCO2 values in air samples from the ileal lumen and samples of saline from the standard tonometer (r2 = .61, p < .001). In pigs with mesenteric ischemia secondary to pericardial tamponade (group 2), air and saline tonometry were well-correlated in the stomach (r2 = .71, p < .001) and ileum (r2 = .83, p < .001). In pigs with normal mesenteric perfusion (group 3) and PaCO2 > 40 torr (5.3 kPa), PaCO2 correlated with ileal mucosal PCO2, determined using air (r2 = .93, p < .001) or saline (r2 = .91, p < .001) tonometry, or gastric mucosal PCO2, determined using air (r2 = 1.00, p < .001) or saline (r2 = .97, p < .001) tonometry. Values obtained by air tonometry were highly correlated with values obtained using standard saline tonometry in the stomach (r2 = .98, p < .001; bias = -5 +/- 5 torr [-0.65 +/- 0.65 kPa]) or ileum (r2 = .96, p < .001; bias = 1 +/- 9 torr [0.13 +/- 1.17 kPa]). CONCLUSIONS: a) Under stable hemodynamic and respiratory conditions, air tonometry (which, in theory, can be performed using a conventional nasogastric or nasoenteric feeding tube) estimates gastrointestinal mucosal PCO2 as accurately as standard saline tonometry in the stomach or ileum; b) respiratory acidosis leads to tissue hypercarbia, a phenomenon that must be considered when tonometry is used to guide therapy in the clinical setting; c) under stable, nonischemic conditions, gastric or intestinal tonometry can be used to estimate PaCO2.

Acidosis↗

PubMed1994

Endotoxin-induced ileal mucosal hyperpermeability in pigs: role of tissue acidosis.

Administration of lipopolysaccharide (LPS) to experimental animals leads to diminished mesenteric perfusion, increased ileal mucosal [H+] , and increased gut epithelial permeability to hydrophilic solutes. We sought to determine whether these phenomena are causally related. Experiments were performed in anesthetized pigs. Permeability was assessed by measuring the plasma-to-lumen clearance of fluorescein isothiocyanate dextran (4,000 Da; FD-4) by a segment of ileum perfused with Ringer lactate solution. Mucosal perfusion (Qmuc) and [H4+] were estimated using laser-Doppler flowmetry and tonometry, respectively. In an initial series of experiments, we showed that mucosal permeability was linearly correlated with mucosal [H+] in animals subjected to graded degrees of mechanically induced mesenteric ischemia (n = 14, R2 = 0.58, P < 0.002) or injected with graded doses of LPS (n = 11, R2 = 0.93, P < 0.0001). In a second series of experiments, we induced mucosal acidosis in normal pigs by mechanical ventilation with either a hypoxic (n = 7) or a hypercapnic (n = 5) gas mixture. In both groups, ileal mucosal permeability to FD-4 increased significantly (P < 0.05), although transmesenteric release of lactate increased significantly only in the hypoxic group. Qmuc was unchanged in both groups. These data suggest that mucosal acidosis, even in the absence of tissue ischemia or hypoxia, increases intestinal permeability to a macromolecular hydrophilic solute. Tissue acidosis may be an important factor contributing to LPS-induced gut mucosal hyperpermeability.

Acidosis↗

PubMed1994

Bactericidal/permeability-increasing protein ameliorates acute lung injury in porcine endotoxemia.

Bactericidal/permeability-increasing protein (BPI), a cationic protein isolated from human neutrophils, binds lipopolysaccharide (LPS), kills gram-negative bacteria, and neutralizes many of the effects of LPS in vitro and in vivo. We hypothesized that a recombinant 23-kDa NH2-terminal fragment of BPI (BPI23) would reduce acute lung injury in endotoxemic pigs. At -18 h, pigs received an intravenous priming dose of LPS (20 micrograms/kg). Anesthetized ventilated swine were randomized to receive 1) no further treatment (n = 4); 2) LPS (250 micrograms/kg over 50 min) and BPI23 (3-mg/kg bolus and 3 mg/kg over 60 min) (n = 6); or 3) LPS and thaumatin, a cationic protein devoid of LPS neutralizing activity that has a molecular mass and isoelectric point that are similar to that of BPI23 (n = 7). BPI23 treatment significantly ameliorated LPS-induced hypoxemia, functional upregulation of opsonin receptors on circulating phagocytes, and alveolitis but had no effect on the elaboration of tumor necrosis factor-alpha or thromboxane A2. The salutory effects of BPI23 on acute lung injury in endotoxemic pigs may be mediated, at least in part, by inhibition of direct activation of phagocytes by LPS.

Animals↗

PubMed1993

Evaluation of right ventricular function during aortic operations.

The simultaneous measurements of mixed venous oxygen saturation (SvO2) and right ventricular ejection fraction (RVEF) have now made it possible to precisely define and correlate the various hemodynamic changes that occur during abdominal aortic operations. Twenty-five patients undergoing infrarenal abdominal aortic aneurysm repair were examined with a pulmonary artery catheter capable of continuously measuring SvO2 and RVEF. With aortic clamping, significant reductions in cardiac index, stroke volume index, and right ventricular end-diastolic volume index (RVEDVI) were noted, while RVEF remained unchanged. Following unclamping of the aorta, a significant reduction in SvO2 occurred, accompanied by an increase in mean pulmonary artery pressure and in pulmonary vascular resistance. Despite the increase in afterload, RVEDVI and RVEF did not change after unclamping. These preliminary data suggest that right ventricular function is preserved during abdominal aortic aneurysm repair.

Aged↗