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Time course of hemoglobin concentrations in nonbleeding intensive care unit patients

ObjectivesTo evaluate the time course of hemoglobin concentrations in nonbleeding intensive care unit patients. DesignProspective, observational study. SettingMultidisciplinary (medicosurgical) department of intensive care. PatientsNinety-one patients with no evidence of recent or active blood loss, no history of hematologic disease or chronic renal failure, and no need for extracorporeal epuration techniques. InterventionsNone. Measurements and Main ResultsData collection included primary diagnoses, Acute Physiology and Chronic Health Evaluation II and sepsis-related organ failure assessment scores, signs of sepsis, 24-hr fluid balance, and hemoglobin concentrations. For the entire intensive care unit stay, the fall in hemoglobin concentrations (calculated from the mean of individual slopes of hemoglobin concentrations over time) averaged 0.52 ± 0.69 g/dL/day. For the 33 patients who stayed in the intensive care unit for >3 days, this decline was larger for the first 3 days than for subsequent days (0.66 ± 0.84 g/dL/day vs. 0.12 ± 0.29 g/dL/day;p < .01). After the third intensive care unit day, the change in hemoglobin concentrations was inversely related to the severity of the disease, as reflected by the Acute Physiology and Chronic Health Evaluation II and the sepsis-related organ failure assessment scores. Hemoglobin concentrations decreased by 0.44 ± 0.70 g/dL/day in the nonseptic and 0.68 ± 0.66 g/dL/day in the septic patients (p = .13). After the third intensive care unit day, hemoglobin concentrations continued to decrease in the septic patients but not in the nonseptic patients (−0.29 ± 0.19 vs. 0.006 ± 0.3 g/dL/day;p = .0016). The fall in hemoglobin concentrations was not significantly related to the fluid balance. The volume of blood drawn daily for laboratory studies was 40.3 ± 15.4 mL: 49.0 ± 11.3 mL in the septic patients and 36.7 ± 14.9 mL in the nonseptic patients (p = .04). ConclusionsHemoglobin concentrations typically decline by >0.5 g/dL/day during the first days of intensive care unit stay in nonbleeding patients. Beyond the third day, hemoglobin concentrations can remain relatively constant in nonseptic patients but continue to decrease in septic patients, as well as patients with high sepsis-related organ failure assessment or Acute Physiology and Chronic Health Evaluation II scores. These observations may help in the interpretation of hemoglobin concentrations in critically ill patients.

Infection Probability Score (IPS): A method to help assess the probability of infection in critically ill patients*

ObjectiveTo develop a simple score to help assess the presence or absence of infection in critically ill patients using routinely available variables. DesignObservational study of a prospective cohort of patients divided into a developmental set (n = 353) and a validation set (n = 140). SettingDepartment of intensive care at an academic tertiary care center. PatientsFour hundred and ninety-three adult patients admitted to the intensive care unit for ≥24 hrs. InterventionsNone. Measurements and Main ResultsThe presence of infection was defined using the Centers for Disease Control definitions. Body temperature, heart rate, respiratory rate, white blood cell count, and C-reactive protein concentrations were measured, and the Sequential Organ Failure Assessment score was calculated throughout the intensive care unit stay. Infection was documented in 92 of the 353 patients (26%) in the developmental set and in 41 of the 140 patients (29%) in the validation set. Univariate logistic regression was used to select significant predictors for infection. Each continuous predictor was transformed in a categorical variable using a robust locally weighted least square regression between infection and the continuous variable of interest. When more than two cate-gories were created, the variable was separated into iso-weighted dummy variables. A multiple logistic regression model predicting infection was calculated with all the variables coded 1 or 0 allowing for relative scoring of the different predictors. The resulting Infection Probability Score consisted of six different variables and ranged from 0 to 26 points (0–2 for temperature, 0–12 for heart rate, 0–1 for respiratory rate, 0–3 for white blood cell count, 0–6 for C-reactive protein, 0–2 for Sequential Organ Failure Assessment score).The best predictors for infection were heart rate and C-reactive protein, whereas respiratory rate was found to have the poorest predictive value. The cutoff value for the Infection Probability Score was 14 points, with a positive predictive value of 53.6% and a negative predictive value of 89.5%. Model performance was very good (Hosmer-Lemeshow statistic, p = .918), and the areas under receiver operating characteristic curves were 0.820 for the developmental set and 0.873 for the validation set. ConclusionsThe Infection Probability Score is a simple score that can help assess the probability of infection in critically ill patients. The variables used are simple, routinely available, and familiar to clinicians. Patients with a score <14 points have only a 10% risk of infection.

Initial and Delayed Onset of Acute Respiratory Failure: Factors Associated with Development and Outcome

In a prospective observational study of 1038 adult admissions to a 31-bed medical/surgical intensive care unit (ICU), acute respiratory failure (ARF, defined as a Pao2/Fio2 ratio ≤200 mm Hg and the need for respiratory support) occurred in 182 (58%) of the 313 admissions with an ICU stay of more than 48 h. Initial ARF (onset within 48 h of ICU admission) occurred in 133 (42%) patients, and delayed onset ARF (onset >48 h after ICU admission) in 49 (16%). On admission, the cardiovascular sequential organ failure assessment (SOFA) score was higher in initial than in delayed onset ARF (1.1 ± 1.5 vs 0.6 ± 1.2, P < 0.05). High admission serum C-reactive protein concentrations (OR 1.08, 95% CI 1.04–1.12, P = 0.0001) and SOFA scores (OR 1.20, 95% CI 1.08–1.33, P = 0.0007) were the factors independently associated with initial ARF, and a low Glasgow coma scale (GCS) score (OR 1.13, 95% CI 1.04–1.21, P = 0.0018) was associated with delayed onset ARF. In initial ARF, a high SOFA score (OR 1.24, 95% CI 1.12–1.38, P = 0.0001) and a low GCS score (OR 0.89, 95% CI 0.83–0.96, P = 0.0013) on admission, and in delayed onset ARF, a low GCS score at 48 h (OR 0.67, 95% CI 0.54–0.84, P = 0.0011) were independently associated with death. The mortality rate was similar for initial and delayed onset ARF.