CV risks of flu, CAUTI protocol, and more

Research summaries from ACP Hospitalist Weekly.

Nearly 12% of inpatients with influenza had acute CV events

Nearly one in eight adults hospitalized with laboratory-confirmed influenza had an acute cardiovascular event, and a high percentage of them experienced in-hospital morbidity and mortality, according to a cross-sectional study conducted by the CDC.

Researchers used the U.S. Influenza Hospitalization Surveillance Network to evaluate and determine risk factors for acute cardiovascular events in adults with a hospitalization associated with lab-confirmed influenza during the 2010-2011 through 2017-2018 influenza seasons. They used ICD-9 and ICD-10 discharge codes to ascertain acute cardiovascular events and estimated risk ratios to describe factors associated with these conditions, adjusting for age, sex, race/ethnicity, tobacco use, chronic conditions, influenza vaccination, influenza antiviral medication, and influenza type or subtype. Results were published online on Aug. 25 by Annals of Internal Medicine.

Of 89,999 adults with lab-confirmed influenza, 80,261 (median age, 69 years [interquartile range, 54 to 81 years]) had complete medical record abstractions and available ICD codes. Of these, 11.7% had an acute cardiovascular event, most commonly acute heart failure (6.2%) and/or acute ischemic heart disease (5.7%). Patients with acute cardiovascular events had a median length of stay of five days, with 31.2% admitted to the ICU, 14.0% requiring mechanical ventilatory support, and 7.3% dying in the hospital (6% excluding those with cardiogenic shock). Among 61,856 patients included in the analysis on potential risk factors, older age, tobacco use, underlying cardiovascular disease, diabetes, and renal disease were all significantly associated with higher risk for acute heart failure and acute ischemic heart disease, whereas those who received the influenza vaccine at least two weeks before hospitalization had lower risk than unvaccinated patients.

The study authors noted that underdetection of influenza cases was likely because testing was based on practitioner orders. In addition, using ICD discharge codes to identify acute cardiovascular events may have introduced misclassification bias, they said.

An accompanying editorial noted that the estimated efficacy of influenza vaccines for secondary prevention of cardiovascular events is 15% to 45%, which is similar to that of statins, antihypertensive agents, and smoking cessation. “We accept the important role of the latter interventions in secondary prevention of cardiovascular disease, but influenza vaccination continues to be overlooked,” the editorialist wrote. “It is time to recognize the significant and preventable cardiovascular morbidity and mortality associated with influenza. It is time to view influenza vaccination as a routine secondary preventive measure for cardiovascular events.”

The CDC issued seasonal influenza vaccination recommendations that address the likelihood that the SARS-CoV-2 and influenza viruses will both be active in the U.S. during the upcoming flu season. The recommendations, issued by the Advisory Committee on Immunization Practices and published by MMWR on Aug. 21, call for flu vaccination of everyone six months of age and older. The article notes that this year's vaccines include updates to the influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria lineage components and that since last year two new vaccines have been licensed for those ages 65 years and older.

Novel protocol may have reduced CAUTI rates

Researchers performed a pre- and postintervention study using a contemporaneous control group at two campuses of an academic medical center to determine whether false-positive catheter-associated urinary tract infection (CAUTI) results could be reduced by a change in sampling and testing protocol.

During the preintervention period, both campuses followed CDC guidelines for CAUTI prevention, including minimizing urinary catheter placement as much as possible, using sterile catheter insertion technique, and performing urinary catheter maintenance. Urine specimens were collected following CDC guidelines via aspiration from a needleless port, after disinfection, using a sterile syringe.

Image by Getty Images
Image by Getty Images

During the postintervention period, both campuses continued to follow CDC guidelines, but the test campus implemented a protocol that required urinary catheters in place at least 24 hours to be removed before urine sampling via a new catheter or sterile straight catheterization, or new urinary catheter placement. Urine was then screened for bacterial load, and a urine culture was done if the screening results were positive. Both the pre- and postintervention periods lasted nine months.

The study's primary outcome was CAUTIs per 1,000 catheter-days at the test campus pre- and postintervention. Secondary outcomes included CAUTI rates per 1,000 patients, catheter-days per patient, and percentage reduction in CAUTI rates between the test campus and a propensity score-matched cohort at the control campus. Results were published Aug. 10 by Clinical Infectious Diseases.

Overall, 7,991 patients from the test campus were included in the primary analysis and 4,264 patients were included in the propensity-score matched secondary analysis. The CAUTI rate per 1,000 patients decreased by 77% in the primary analysis, from 6.6 to 1.5. CAUTIs per 1,000 catheter-days and urinary catheter-days per patient also decreased by 63% (from 5.9 to 2.2) and 37% (from 1.1 to 0.69), respectively (P≤0.001 for all comparisons). In the propensity score-matched analysis, for the test campus versus the control campus, the CAUTI rate per 1,000 patients decreased by 82% versus 57%, CAUTIs per 1,000 catheter-days decreased by 68% versus 57%, and catheter-days per patient decreased by 44% versus 1% (P<0.001 for all comparisons).

The authors noted that their study could not account for all patient-level differences and that no information was available on complications or unintended consequences of the catheterization changes mandated by the protocol, among other limitations. They concluded that their study found an association between their protocol to minimize contamination due to urinary or bladder colonization and lower CAUTI rates and urinary catheter-days. “A reduction in CAUTI rates was observed across all patient populations at the test site including critically ill, neurology, medicine and surgery patients, suggesting that colonization and false positive urine cultures are pervasive occurrences,” the authors wrote. They called for future studies to perform a cost analysis of protocolized urine sampling.

Coding differences may explain mortality at critical access hospitals

Differences in short-term mortality rates at critical access hospitals (CAHs) versus non-CAHs may be related to differences in coding practices, according to a recent study.

Researchers performed a serial cross-sectional study of rural Medicare fee-for-service beneficiaries who were admitted to CAHs and non-CAHs for pneumonia, heart failure, chronic obstructive pulmonary disease, arrhythmia, urinary tract infection, septicemia, and stroke from 2007 to 2017. The goal of the study was to assess serial differences in risk-adjusted mortality rates between CAHs and non-CAHs after accounting for differences in diagnosis coding. (CAHs are reimbursed at cost and may therefore report fewer diagnoses.) The main outcome measures were discharge diagnosis counts (including trends from 2010 to 2011 when Medicare expanded the allowable number of billing codes for hospitalizations) and combined in-hospital and 30-day postdischarge mortality rates adjusted for demographic characteristics, primary diagnosis, and preexisting conditions. Outcomes with and without further adjustment for Hierarchical Condition Category (HCC) score were also compared. The study results were published Aug. 4 by JAMA.

Overall, the study included 4,094,720 hospitalizations, 17% at CAHs and 83% at non-CAHs, for 2,850,194 unique Medicare beneficiaries. The mean age was 76.3 years, and 55.5% were women. Patients in CAHs were older, with a median age of 80.1 years versus 76.8 years, and were more likely to be women (58% vs. 55%) than patients in non-CAHs. The adjusted mean discharge diagnosis count was 7.52 for CAHs versus 8.53 for non-CAHs in 2010 (difference, −0.99; 95% CI, −1.08 to −0.90; P<0.001) and 9.27 versus 12.23 in 2011 (difference, −2.96; 95% CI, −3.19 to −2.73; P<0.001). In the model that adjusted further for HCC score, adjusted mortality rates were 13.52% for CAHs and 11.44% for non-CAHs (difference, 2.08 percentage points; 95% CI, 1.74 to 2.42; P<0001) in 2007 and 15.97% and 12.46% (difference, 3.52 percentage points; 95% CI, 3.09 to 3.94; P<0.001) in 2017 (P<0.001 for the interaction). In the model that did not adjust further for HCC score, adjusted mortality rates did not differ significantly between CAHs and non-CAHs for any years except 2007 (12.19% vs. 11.74%; difference, 0.45 percentage point [95% CI, 0.12 to 0.79]; P=0.008) and 2010 (12.71% vs. 12.28%; difference, 0.42 percentage point [95% CI, 0.07 to 0.77]; P=0.02).

The study included only Medicare fee-for-service beneficiaries and data were lacking on such factors as smoking, obesity, and living environment, among other limitations, the authors noted. They concluded that in their rural study population, CAHs submitted significantly fewer diagnosis codes compared to non-CAHs, and short-term mortality rates usually did not differ by hospital type when adjusted for preexisting conditions that aren't affected by coding for in-hospital comorbidities. “These findings suggest that short-term mortality outcomes at CAHs may not differ from those of non-CAHs after accounting for different coding practices for in-hospital comorbidities,” the authors wrote.