Journal Watch: Recent studies of note

Recent studies of note.

Clinical prediction rule developed, validated for pneumonia after CABG

Researchers have developed and validated a clinical prediction rule comprising 13 indicators for nosocomial pneumonia after coronary artery bypass grafting (CABG).

The researchers extracted data from Tenet Healthcare's Quality and Resource Management System on 17,143 individuals undergoing CABG at 32 hospitals in six states. They developed a logistic regression-based rule in half of the subjects (derivation group), and validated it in the other half (validation group). Study subjects underwent CABG from January 1999 through February 2004. The study was published Feb. 15 in Clinical Infectious Diseases.

Three hundred sixty-one (2.11%) subjects developed pneumonia without a known aspiration etiology; 4% died after surgery. Patients with pneumonia had a significantly higher risk of dying after surgery (odds ratio, 4.18; 95% CI, 3.08 to 5.67) and longer lengths of hospital stay (mean stay, 22.0 days vs. 8.07 days, P<0.001). Researchers identified 13 independent predictors of pneumonia in the derivation group:

  • body mass index <18.5 kg/m2
  • smoking history
  • admission from a nonresidential setting (e.g., a long-term care facility)
  • history of cancer
  • chronic obstructive pulmonary disease
  • Canadian Cardiovascular Society score ≥
  • prior internal mammary artery CABG
  • emergency status
  • serum creatinine level >1.2 mg/dL
  • percutaneous transluminal coronary angioplasty during current hospitalization
  • intraoperative blood transfusion
  • preoperative vancomycin administration
  • mechanical ventilation for more than a day

Total risk scores were calculated by adding the individual point values of all risk factors for a patient. The risk of nosocomial pneumonia was approximated from a graph of predicted probability versus calculated score, or by using an equation. The multivariate model significantly predicted pneumonia after CABG (X2=205.6; P<0.001).

In the derivation group, the rule was well calibrated between deciles of observed and expected risk (Hosmer-Lemeshow X2=5.51; P=0.70), and discriminated well between patients who did and didn't develop pneumonia after CABG (area under receiver-operating characteristic [ROC AUC] curve in the derivation group, 0.78; 95% CI, 0.75 to 0.82). The rule also discriminated well in the validation group (ROC AUC, 0.75; P=0.18 for difference in ROC AUC between groups).

Postoperative pneumonia is the third most common infection after surgery in the U.S., and causes significant morbidity and death, the researchers noted. This prediction rule comprises readily available and clinically sensible dichotomous variables that can be used to quantify post-CABG risk, they said. It's likely that the rule is broadly generalizable due to the large sample size and use of data from dozens of teaching and community hospitals in six states, though external validity should be determined before the rule is used routinely, they added. If validated, the rule could help with preventive treatment decisions and resource allocation, they said.

Rapid response teams don't appear to lower mortality for adults

Rapid response teams appear to have little effect on adult hospital mortality, though they are associated with fewer non-ICU-treated cardiopulmonary arrests, a meta-analysis found.

Researchers reviewed studies published from Jan. 1, 1950 through Nov. 31, 2008, including randomized clinical trials and prospective studies of rapid response teams (RRTs) that reported data on changes in hospital mortality (primary outcome) or cardiopulmonary arrests (secondary outcome). They found 18 studies from 17 publications, comprising almost 1.3 million hospital admissions. Results were published in the Jan. 11 Archives of Internal Medicine.

Implementing an RRT outside the ICU wasn't associated with lower mortality rates for adults (relative risk [RR], 0.96; 95% CI, 0.84 to 1.09), though it was associated with a 33.8% reduction in cardiopulmonary arrest rates (RR, 0.66; CI, 0.54 to 0.80). In children, implementing an RRT was associated with a 37.7% reduction in non-ICU-treated cardiopulmonary arrest rates (RR, 0.62; CI, 0.46 to 0.84) and a 21.4% reduction in hospital death rates (RR, 0.79; CI, 0.63 to 0.98)—but the pooled mortality estimates weren't robust to sensitivity analyses in children.

The effect of implementing RRTs on adult hospital deaths has shifted in the last decade toward zero, which the authors said raises questions about how effectively information about RRTs has been disseminated and whether there may have been publication bias in earlier studies. In studies that did report improvements in mortality, there was a disconnect between these improvements and cardiopulmonary arrest rates. As such, it's likely that the mortality benefit of RRTs was overestimated in these studies, with the lower rates due to other factors.

The finding of discordance between mortality and cardiopulmonary arrest rates in adults may be attributed to several factors, including reporting bias because RRTs transfer deteriorating patients to the ICU (which may cause overestimation of the effect of RRTs on cardiopulmonary arrest rates) and the possibility that initial prevention of cardiopulmonary arrest could have a short-term impact (and thus not affect survival). In children, the finding of lower mortality with RRTs may have occurred in part because respiratory conditions are more frequently the cause of cardiopulmonary arrest, and these children have fewer comorbidities than adults.

While the meta-analysis had enough power to detect a moderate drop in hospital mortality, it may have been limited in detecting smaller changes; a larger study may yield a significant reduction, the authors acknowledged. The analysis is also limited in that researchers didn't have patient-level data, and comprehensive information on the hospitals that use RRTs wasn't available.

Of note, the majority of studies took place in academic medical centers and it is possible that the greater presence of medical house staff and hospitalists may have blunted the effects of RRT implementation. Still, given that the primary reason for developing RRTs was to improve survival, this analysis suggests health quality organizations should take a second look at whether they want to promote RRTs, the authors said. An editorialist cautioned, however, that RRTs shouldn't be rejected “with the same haste that we accepted them, without first determining which patients need them and when.”

‘Surviving Sepsis' campaign associated with improved care, lower mortality

Hospitals that participated in a campaign to follow guidelines on managing severe sepsis and sepsis shock saw improved quality of care and lower mortality rates, a study found.

Researchers analyzed data from 15,022 subjects at 165 sites to determine compliance and associated hospital mortality with participation in the Surviving Sepsis Campaign (SSC). The SSC aimed to facilitate compliance with evidence-based sepsis management guidelines in the ICUs, EDs and wards of hospitals in the U.S., South America and Europe.

Data for this study were collected from January 2005 through March 2008. One guideline bundle comprised actions to be completed within six hours of presentation with severe sepsis (resuscitation bundle), and another within 24 hours (management bundle). Results were published in February's Critical Care Medicine.

Compliance with the resuscitation bundle rose from 10.9% in the first site quarter to 31.3% by the end of the second year (P<0.0001), while compliance with the management bundle rose from 18.4% in the first quarter to 36.1% at the end of two years (P=0.008). With the exception of inspiratory plateau pressure (which was high at baseline), compliance with all bundle elements rose significantly. Unadjusted hospital mortality declined to 30.8% from 37% over two years (P=0.001). The adjusted odds ratio for mortality improved the longer a site was in the campaign, with an adjusted absolute decrease of 0.8% per quarter and 5.4% over five years.

Because the efficacy of the SSC was inferred by observing changes over time, and not by randomized, controlled trials, results must be interpreted cautiously, the authors noted. Limitations include the fact that participation in the campaign was voluntary, meaning the hospitals studied may not be representative of all hospitals.

It also isn't known if the patients were a representative sample of all potentially eligible subjects at a given site. In addition, formal illness severity scores were not obtained. The association of bundle targets with outcome doesn't necessarily imply a causal relationship, either, they added. Still, the data are “encouraging,” and should inspire professional societies to disseminate and implement guidelines, not just generate them, the authors said.

ICUs fail to meet guidelines for nutrition therapy in numerous areas

Nutrition therapy provided by ICUs often fails to meet guideline recommendations in a number of areas, a study found.

The observational cohort study was conducted in 158 adult ICUs in 20 countries and involved 2,946 mechanically ventilated patients who were in the ICU for at least 72 hours. The ICUs performed well on some of the guidelines, including use of enteral nutrition in preference to parenteral nutrition, glycemic control, lack of utilization of arginine-enriched enteral formulas, delivery of hypocaloric parenteral nutrition, and the presence of a feeding protocol.

However, the start of enteral nutrition was often delayed; the average time between admission and initiation was 46.5 hours, with a range of 8 to 149 hours. Motility agents and small bowel feeding were underused in patients with high gastric residual volumes (58.7% and 14.7% of patients, respectively). The studied ICUs also often failed to adhere to guidelines calling for formulas enriched with fish oils, glutamine supplementation, timing of supplemental parenteral nutrition, and avoidance of soybean oil-based parenteral lipids. On average, the facilities met only 59% of patients' energy needs and 60.3% of their protein requirements.

Some of the ICUs were significantly more successful at adhering to the guidelines (one site provided nutrition for 100% of patient days, for example). Their success shows that guideline adherence is an achievable goal, the study authors concluded. Other facilities should set these results as the target of quality improvement efforts, with the end goal of reducing the morbidity and mortality of critically ill patients. The authors did acknowledge, however, that 100% adherence may not be achievable in some situations. The study appears in the February issue of Critical Care Medicine.