Cardiac troponin I levels and alveolar-arterial oxygen gradient in patients with community-acquired pneumonia.

BACKGROUND: Patients with community-acquired pneumonia (CAP) appear to have cardiac stress as demonstrated by elevated B-type natriuretic peptide (BNP). We hypothesised that myocardial stress and decrease in oxygenation might also lead to elevations of cardiac troponin I (cTnI) levels in serum. OBJECTIVE: The aim of this study was to see if cTnI was associated with the alveolar-arterial oxygen gradient (DeltaA-a), a marker of severity in CAP. METHODS: Retrospective cohort study of 901 CAP patients with no evidence of acute coronary syndrome presenting to a large, tertiary-care, urban teaching hospital over a 3-year period. RESULTS: A strong linear trend between log(10)cTnI and DeltaA-a was observed (r(2)=0.76) with a statistically significant Spearman correlation coefficient (r(s)=0.75; p<0.0001) between cTnI and DeltaA-a. A cTnI value of 0.5 ng/ml discriminated mild CAP from moderate-severe CAP with an OR=208 (95% CI: 50.5-408; p<0.0001). CONCLUSIONS: These data suggest that decreased blood O(2) levels as suggested by elevated DeltaA-a may lead to acute myocardial damage and that cTnI may be useful as a biomarker to stratify risk in subjects with CAP.

The association of D-dimer levels with clinical outcomes in patients presenting with acute pulmonary embolism.

The D-dimer fragment of fibrin degradation has been a useful adjunct in the diagnosis of venous thromboembolism (VTE). In conjunction with predictive algorithms, the high negative predictive value (NPV) of D-dimer measurements has provided this analyte with a prominent position in the diagnosis of pulmonary embolism (PE). The purpose of this study was to determine if D-dimer levels correlate with ventilation/perfusion (V/Q) derangements as assessed by the alveolar-arterial oxygen tension gradient (DeltaA-a) and to ascertain if quantitative measurements of D-dimer on admission have prognostic value in terms of during-admission mortality and recurrence over a 60-week period. The study utilized a retrospective cohort of 108 subjects admitted to a single institution and studied longitudinally. The cohort was divided into 4 groups representing degree of severity assessed by computed tomographic (CT) angiography: mild, moderate, severe, and very severe. Differences in D-dimer levels among these groups were strongly significant (P < .0001). A strong correlation was observed between D-dimer concentration and DeltaA-a (P < .0001). Logistic methods were used to calculate a "cut-off" level that would distinguish mild-moderate from severe-very severe PE. At a concentration of 12.35 mug/mL, this level yielded an odds ratio (OR) of 12.64 (P = .006) for during-admission mortality and a hazard ratio (HR) of 0.13 (P < .0001) for 60-week recurrence. These data suggest that D-dimer levels have utility beyond their NPV and should be considered as potential prognostic markers in subjects presenting with acute PE.

Alveolar-arterial oxygen gradient, pneumonia severity index and outcomes in patients hospitalized with community acquired pneumonia.

The alveolar-arterial oxygen gradient (DeltaA-a) provides a useful assessment of ventilation/perfusion (V/Q) abnormalities. The objectives of the present study were to: (i) examine the correlation between the DeltaA-a and the pneumonia severity index (PSI); and (ii) determine whether these measures were comparable in predicting clinical outcomes. The present study was conducted at a 750-bed teaching hospital. It examined a retrospective cohort of 255 patients with community acquired pneumonia (CAP) over a 2 year period. Association between the CAP and DeltaA-a was investigated by regression models and correlation, as well as two logistic models for subjects bifurcated by low-risk/moderate-to-high risk. The decision levels (DL) for both PSI and DeltaA-a were then compared as predictors of both length of stay (LOS) and survival. The correlation between PSI and DeltaA-a was strong (rho = 0.76; P < 0.0001) and was best modelled by a curvilinear relationship. Both logistic models indicated a strong association (P < 0.001) between DeltaA-a and PSI and yielded an optimal DL for the DeltaA-a of < 89 mmHg. Inter-test agreement of DeltaA-a with PSI was 76.9% (kappa = 0.60; 95% confidence interval 0.47-0.72; P < 0.0001). At < 89 mmHg, the odds ratios for LOS were similar to those at PSI = 90 in predicting LOS in the range 3-7 days, inclusive. There was no significant difference in the ability of DeltaA-a and PSI to predict survival for either the low- or high-risk group (P = 0.363 and P = 0.951, respectively). The DeltaA-a correlates well with PSI and performs comparably in predicting two major outcomes in subjects hospitalized with CAP.

Pulmonary gas exchange during hemodialysis: a comparison of subjects with and without COPD on bicarbonate hemodialysis.

Little is known about the effect of hemodialysis (HD) on gas exchange in subjects with chronic obstructive pulmonary disease (COPD). The purpose of this study was to examine blood gases and pH in COPD patients undergoing HD with bicarbonate dialysate. We studied thirteen subjects with COPD and thirteen controls (CON). All were dialyzed for 4 hrs against a bicarbonate HD solution. Blood gases, pH and HCO(3) (-) were initially analyzed (t(0)) and, during HD, at 30 min (t(0.5)), 1 hr (t(1)) and 4 hrs (t(4)). At t(0), a statistically significant difference was observed for PO(2) (CON: 84.7±3.60, COPD: 72.19±4.92; p<0.001). For the first hr, PO(2) decreased, and at t(1), oxygen was required for 6 COPD subjects. By t(4), there was no significant difference in PO(2) between groups. The alveolar-arterial gradient (ΔA-a) remained different between groups (P<0.001, all times), with increasing ΔA-a for both groups up to t(1) and decreasing over the remaining 3 hr. For both groups, at t(4), ΔA-a was higher than at t(0) (p<0.001). For PCO(2), both groups demonstrated increases from t(0) to t(1) (p=0.0004), with COPD having PCO(2) higher than CON at t(0.5) and t(1) (p<0.05 for both); by t(4), PCO(2) levels decreased to nearly the same as at t(0). Over the 4 hr treatment, HCO(3) (-) and pH increased significantly for both groups; however no significant difference was observed between COPD and CON. Markedly increased ΔA-a is observed during HD in some COPD patients. COPD patients retain more CO(2). However, the effect of HCO(3) (-) leads to mild metabolic alkalosis at t(4).

Non-anion gap acidosis in asthma: clinical and laboratory features and outcomes for hospitalized patients.

Metabolic acidosis secondary to lactic acidosis may occur in acute, severe asthma and its presence suggests that respiratory muscle fatigue and tissue hypoxia play a major part in the pathogenesis. Non-anion gap metabolic acidosis (NAG acidosis) has also been reported in acute asthma but its impact on the clinical outcome has not been evaluated. The objective of this study was to evaluate the prevalence of NAG acidosis, characterize the laboratory findings, and determine its impact on clinical outcomes. Acid-base and electrolyte status and clinical outcomes were examined over a 1-yr (2005 calendar yr) period in 109 adult patients (38 males, 71 females; age range 21 to 91 yr) hospitalized for asthma exacerbation. The cohort was divided into 3 groups: I. No metabolic acidosis (n = 66), II. Anion gap (AG) acidosis (n = 11), and III. NAG acidosis (n = 32). For each of the groups, laboratory findings were consistent, demonstrating a tendency to hyperchloremia in the NAG acidosis group. One subject in the NAG acidosis group died. NAG acidosis was associated with a statistically significant (p = 0.028) risk of requirement for mechanical ventilation necessitating admission to the Medical Intensive Care Unit (MICU); the odds ratio for intubation for NAG acidosis compared to other groups was 3.92. No difference, however, was detected in overall length of stay (LOS) in hospital for patients with NAG acidosis vs the other groups. NAG metabolic acidosis in acute asthma may be more prevalent than expected and may be associated with more frequent need for mechanical ventilation and admission to an intensive care unit.