Gastric colonization as a consequence of stress ulcer prophylaxis: a prospective, randomized trial.

STUDY OBJECTIVE: To evaluate gastric alkalization and bacterial colonization in critically ill patients receiving stress ulcer prophylaxis with gastric tube feeds, sucralfate, intermittent intravenous cimetidine, or continuous intravenous cimetidine. DESIGN; Prospective, randomized, unblinded trial. SETTING: Medical and surgical intensive care units of a large university-affiliated, tertiary care community hospital. PATIENTS: Fifty-three evaluable critically ill patients with respiratory failure requiring mechanical ventilation. INTERVENTIONS: Patients not receiving nasogastric tube feeds were randomized to sucralfate 1 g every 6 hours, cimetidine 300 mg by intravenous bolus every 8 hours, or cimetidine 900 mg by continuous intravenous infusion/24 hours. Gastric samples were obtained daily for pH and culture. MEASUREMENTS AND MAIN RESULTS: Patients with respiratory failure and a high mortality rate had a mean gastric pH of 1.96 +/- 1.5 at study entry. There were no significant differences in gastric pH or gastric colonization among the three arms. Fourteen patients (26%) developed gastric colonization, which was statistically significant but poorly correlated with gastric alkalinity (r2=0.08, p<0.043). CONCLUSION: Gastric luminal pH was unchanged regardless of which method was used for stress ulcer prophylaxis. Bacterial colonization was increasingly likely in patients with a persistent alkaline gastric environment.

A comparison of four severity-adjusted models to predict mortality after coronary artery bypass graft surgery.

OBJECTIVE: To assess the validity of four severity-adjusted models to predict mortality following coronary artery bypass graft surgery by using an independent surgical database. DESIGN: A prospective observational study wherein predicted mortality for each patient was obtained by using four different published severity-adjusted models. SETTING: A university-affiliated teaching community hospital. PATIENTS: Eight hundred sixty-eight consecutive patients who underwent coronary artery bypass graft surgery without accompanying valve or aneurysm repair during the period from 1991 to 1993. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Predicted mortality rates for each model were obtained by averaging individual patient predictions and were compared with actual morality rates. We assessed the accuracy of overall prediction for the total series, as well as compared individual patient predictions created by each model. The discrimination of models was assessed with receiver operating characteristic curves and the Hosmer-Lemeshow goodness-of-fit statistic. RESULTS: The observed crude mortality rate was 3.7%. The predicted mortality rate ranged from 2.8% to 9.2%, despite relatively good discrimination by the models (area under the receiver operating characteristic curve, 0.70 to 0.74). The individual patient mortality predicted by different models varied by as much as a ninefold difference. CONCLUSIONS: The currently used coronary artery bypass graft predictive models, although generally accurate, have significant shortcomings and should be used with caution. The predicted mortality rate following coronary artery bypass graft surgery varied by a factor of 3.3 from lowest to highest, making the choice of model a critical factor when assessing outcome. The use of these models for individual patient risk estimations is risky because of the marked discrepancies in individual predictions created by each model.

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.

Continuous monitoring of mixed venous oxygen saturation during aortic operations.

OBJECTIVE: To systematically analyze the changes in mixed venous oxygen saturation (delta SvO2) during aortic operations with tube, aortobi-iliac, and aortobifemoral grafts. DESIGN: Survey of consecutive patients. SETTING: Teaching community hospital. PATIENTS: Thirty-one patients (22 male, 9 female, mean age 67 +/- 10 yrs), undergoing elective operations for aortic aneurysms (n = 25) and aortoiliac occlusive disease (n = 6). INTERVENTIONS: SvO2 was recorded throughout the operation. Cardiac output, mean pulmonary arterial pressure, arterial oxygen saturation (SaO2), and arterial pH were measured before and immediately after the unclamping of the aortic graft. RESULTS: In all patients, unclamping the aorta resulted in a marked reduction of mean SvO2, with no change in the cardiac output or SaO2. The unclamping of tube grafts was associated with a significant reduction in arterial pH (p less than .01) and in SvO2 (p less than .001), when compared with unclamping of bifurcation grafts. A significant (p less than .05) increase in mean pulmonary arterial pressure was observed after unclamping the aorta in patients with tube grafts. Despite a longer clamp time, unclamping the second limb of a bifurcation graft resulted in a smaller delta SvO2, when compared with that observed after unclamping the first limb (12% vs. 6%; p less than .01). The delta SvO2 after unclamping limb II was only 2% in aortobifemoral grafts and 9% in aortobi-iliac grafts. CONCLUSIONS: Reperfusion via extensive pelvic and lumbar collaterals in patients with aortoiliac occlusive disease reduces the delta SvO2 after aortic unclamping. Monitoring the changes in SvO2 during different types of aortic reconstruction helps to define precisely the physiologic alterations that occur in the course of these operations.

Nosocomial respiratory tract colonization and infection with aminoglycoside-resistant Acinetobacter calcoaceticus var anitratus: epidemiologic characteristics and clinical significance.

During the period July 1983 through December 1984, aminoglycoside-resistant Acinetobacter calcoaceticus var anitratus (ACA) were isolated from 98 patients in a university hospital. Eighty-seven percent of patients (85/98) acquired aminoglycoside-resistant ACA in the intensive care unit (ICU) and 92% (90/98) of all initial isolates were from sputum. ICU patients with respiratory colonization/infection with aminoglycoside-resistant ACA were compared with matched ICU controls with other gram-negative rods in sputum. Compared with controls, the duration of ICU stay prior to colonization/infection with aminoglycoside-resistant ACA was significantly longer for cases (14.7 days v 5.9 days, P = 0.002). Although exposures to devices and procedures were not significantly different for the two groups, cases received respiratory therapy significantly longer than did controls (14.7 days v 6.6 days, P = 0.006). Prior to isolation of aminoglycoside-resistant ACA in sputum, cases received more cephalosporins than did controls (1.9 v 1.2, P = 0.018); aminoglycoside usage in the two groups was comparable but cases tended to have received aminoglycoside for longer durations before colonization/infection than had controls (9.0 days v 6.1 days, P = 0.08). Following sputum isolation of ACA, 6 of 22 cases developed ACA bacteremia compared with bacteremia in 2 of 22 controls. We conclude that factors predisposing to colonization/infection with aminoglycoside-resistant ACA were extended ICU care, prolonged respiratory therapy, and prior therapy with cephalosporins and aminoglycoside. In addition, ACA may be a more common cause of secondary bacteremia than previously appreciated.

Nosocomial pulmonary infection: possible etiologic significance of bacterial adhesion to endotracheal tubes.

Biomaterials are essential for life support and monitoring of critically ill patients, but their use increases the risk of nosocomial infection. Of the various plastics used for life support and monitoring devices, polyvinylchloride is one to which bacteria most readily adhere. Through the use of qualitative culture techniques and scanning and transmission electron microscopy, we studied the surfaces of polyvinylchloride endotracheal tubes removed from 25 ICU patients, to determine if bacterial adhesion to those tubes was sufficient to provide a possible source for repeated contamination of the tracheobronchial tree. Of the surfaces studied, 16% were partially covered and 84% were completely covered by an amorphous bacteria-containing matrix. Some biofilm-enclosed bacterial aggregates projected from the matrix into the lumen of the tube. The mechanism by which endotracheal tubes repeatedly inoculate the lungs of intubated patients may prove to be dislodgment of such aggregates by suction apparatus.