Objective. To investigate national trends in hospital admissions for malignant hypertension and hypertensive encephalopathy.
Study design . Retrospective cohort study. The Nation-wide Inpatient Sample  was used to identify all hospitalizations between January 2000 and December 2011 during which a primary diagnosis of malignant hypertension, hypertensive encephalopathy, or essential hypertension occurred. Time series models were estimated for these diagnoses and also for the combined series. A piecewise linear regression analysis was done to investigate whether there were changes in the trends of these series. In addition, the researchers compared patient characteristics.
Results. There was a gradual increase in the number of hypertension-related hospitalizations from 2000 to 2011. However, after 2007, the number of admissions for malignant hypertension and hypertensive encephalopathy increased dramatically, whereas diagnoses for essential hypertension fell ( P < 0.001). Mortality for malignant hypertension significantly fell after the change point of 2007 (–36%, P = 0.02) but there was no significant difference in mortality for hypertensive encephalopathy or essential hypertension. The number of diagnoses and the adjusted average charges significantly increased after the change point for all hypertension series, although the increase in malignant hypertension and hypertensive encephalopathy was higher than in essential hypertension. Length of stay significantly decreased after 2007 for all series. Mean patient age and number of procedures for all series were similar before and after the change point.
Conclusion. Since the dramatic increase in the number of hospital admissions did not result in dramatic increases in morbidity, which would have been expected, the increase was most likely related to a change in coding practices that was implemented in 2007 and not actual changes in disease incidence.
Hypertension is a major public health problem associated with significant morbidity and mortality . In general, hypertension is asymptomatic; however, life-threatening manifestations of hypertension can develop. A hypertensive emergency is a situation in which uncontrolled hypertension is associated with acute end-organ damage. Most patients presenting with hypertensive emergency have chronic hypertension, although the disorder can present in previously normotensive individuals . The 2 major emergency syndromes are malignant hypertension and hypertensive encephalopathy. They usually require hospitalization, and therefore monitoring trends in admissions for these conditions is a reasonable population-based indicator for failures related to hypertension management.
In this epidemiologic study by Polgreen et al, the authors found a increasing trend in admissions for malig-nant hypertension and hypertensive emergencies, with a substantial increase after 2007. Although the authors considered the possibility that their findings represented a true change in the epidemiology of hypertensive emergencies, they concluded that this appears unlikely, as the diagnoses of essential hypertension fell, and in addition, an expected associated increase in morbidity was not seen. They attribute the shift to a change in assignment of administrative billing codes. In 2007, DRG codes were changed to medical severity DRG codes . The authors acknowledge that there was a recession from 2007 to 2009 that led to an increase in the number of uninsured Americans . However, they noted that the uninsured were no more likely to be diagnosed with malignant hypertension or hypertensive encephalopathy than essential hypertension and there is no reason to think that a change provider’s management of hypertension could have been responsible.
Limitations to this study were the use of administrative data only and the lack of data on outpatient medication use.
Applications for Clinical Practice
As the authors suggest, the study raised questions regarding the use of administrative data for monitoring hypertension outcomes. Future studies are needed to examine whether the rise in diagnoses for malignant hypertension and hypertensive encephalopathy are related to coding practices or other variables.
—Paloma Cesar de Sales, BN, RN, MS