Risk factors for 30-day readmission in adults hospitalized for pulmonary hypertension

Readmissions for pulmonary hypertension are poorly understood and understudied. We sought to determine national estimates and risk factors for 30-day readmission after pulmonary hypertension-related hospitalizations. We utilized the Healthcare Cost and Utilization Project Nationwide Readmission Database, which has weighted estimates of roughly 35 million discharges in the US. Adult patients with primary International Classification of Disease, Ninth Revision, Clinical Modification diagnosis codes of 416.0 and 416.8 for primary and secondary pulmonary hypertension with an index admission between 2012 and 2014 and any readmission within 30 days of the index event were identified. Predictors of 30-day readmission were identified using multivariable logistic regression with adjustment for covariates. Results showed that the national estimate for Primary Pulmonary Hypertension vs Secondary Pulmonary Hypertension-related index events between 2012 and 2014 with 30-day readmission was 247 vs 2550 corresponding to a national readmission risk estimate of 17% vs 18.3%, respectively. The presence of fluid and electrolyte disorders, renal failure, and alcohol abuse were associated with increased risk of readmission in Primary Pulmonary Hypertension, while factors associated with Secondary Pulmonary Hypertension readmissions included anemia, congestive heart failure, lung disease, fluid and electrolyte disorders, renal failure, diabetes, and liver disease. The median cost of Primary Pulmonary Hypertension admissions and readmissions were $46,132 (IQR: $25,384–$85,647) and $41,604.50 (IQR: $22,481.50–$84,420.50), respectively. The median costs of Secondary Pulmonary Hypertension admissions and readmissions were $34,893 (IQR: $19,670–$66,143) and $36,279 (IQR: $19,059–$74,679), respectively. In conclusion, approximately 19% of Primary Pulmonary Hypertension and Secondary Pulmonary Hypertension hospitalizations result in 30-day readmission, with significant costs accrued during the index hospitalization and readmission. With evolving clinical terminology and diagnostic codes, future study will need to better clarify underlying factors associated with readmissions amongst pulmonary hypertension sub-types, and identify methods and procedures to minimize readmission risk.

Abstract 106: Predicting Pulmonary Hypertension Readmission Using Machine Learning Models

Objectives: Pulmonary hypertension (PH) is increasingly recognized but understudied. We sought to determine predictors of 30-day readmission after PH-related hospitalization using Driverless Artificial Intelligence (DAI) algorithm.

Methods: We utilized the 2012-2014 Healthcare Cost and Utilization Project Nationwide Readmission Database (NRD) that accounts for weighted estimates of roughly 35 million discharges in the United States. Adult patients with primary ICD-9-CM diagnosis codes of 416.0 and 416.8 for primary and secondary PH with an index admission and any readmission within 30-days of the index event were identified. We assessed predictors of all cause 30-day readmission from clinical, hospital and 29 AHRQ comorbidity measures using predictive modeling to provide interpretable risk factors globally at population level and locally associated with each discharge. The risk prediction model was developed using DAI algorithm and results compared to models based on LIME GLM, Random Forest, and Decision Tree. Overall model performance was assessed using concordance statistic.

Results: Data from patients with 14,659 admissions and 2797 30-day readmissions were used to train the model. After data processing, the final model included 3674 variables. The Random Forest model had the best performance with c-statistic of 0.70 and surrogate models compared at AUCs of 0.51(Decision Tree), 0.62 (LIME) and (DAI) 0.59. Global features that mainly important to the overall prediction of DAI model were deficiency anemia, APR-DRG severity risk, APR-DRG mortality risk, renal failure and CHF.

Conclusion: Using predictive models with high predictive power, interpretable risk factors and prediction accuracy may enable health care systems to accurately target high-risk PH patients and prevent recurrent readmissions.

Nitric oxide synthase and cGMP activity in the salivary glands of the American dog tick Dermacentor variabilis

We colocalized nitric oxide synthase (NOS) activity in epithelial cells that surround the salivary gland duct in female Dermacentor variabilis with NADPH diaphorase histochemistry and immunohistochemistry using a polyclonal anti-endothelial NOS. Using size-exclusion chromatography, a fraction with a molecular mass of about 185 kDa that had diaphorase activity was eluted from tick salivary gland homogenate. This fraction converted arginine to citrulline with the production of nitric oxide (NO), which was detected by using electron spin resonance spectroscopy. The complete activity of the diaphorase fraction was dependent on NADPH, FAD, tetrahydrobiopterin, calmodulin, (CaM), and Ca(2+), but was not dependent on dithiothreitol. The arginine analog N(G)-monomethyl-L-arginine inhibited the activity of this fraction. NO and arginine activated soluble guanylate cyclase to produce cGMP in dopamine-stimulated isolated salivary glands. Dopamine-stimulated isolated salivary glands treated with tick saline containing either EDTA, the NOS inhibitor N(G)-nitro-L-arginine methyl ester, or the calcium/CaM binding inhibitor W-7 showed no increase in cGMP. The NO donor sodium nitroprusside significantly increased cGMP levels in unstimulated isolated salivary glands. A possible function for NO in salivation by this ixodid tick is discussed.

CS gas--implications for the anaesthetist

Although the use of CS gas is illegal in the UK, an occasional patient exposed to its effects may be seen. We report the problems experienced with the anaesthetic management of such a patient.