Influence of hospital volume and outcomes of adult structural heart procedures

Hospital volume is regarded amongst many in the medical community as an important quality metric. This is especially true in more complicated and less commonly performed procedures such as structural heart disease interventions. Seminal work on hospital volume relationships was done by Luft et al more than 4 decades ago, when they demonstrated that hospitals performing > 200 surgical procedures a year had 25%-41% lower mortality than those performing fewer procedures. Numerous volume-outcome studies have since been done for varied surgical procedures. An old adage "practice makes perfect" indicating superior operator and institutional experience at higher volume hospitals is believed to primarily contribute to the volume outcome relationship. Compelling evidence from a slew of recent publications has also highlighted the role of hospital volume in predicting superior post-procedural outcomes following structural heart disease interventions. These included transcatheter aortic valve repair, transcatheter mitral valve repair, septal ablation and septal myectomy for hypertrophic obstructive cardiomyopathy, left atrial appendage closure and atrial septal defect/patent foramen ovale closure. This is especially important since these structural heart interventions are relatively complex with evolving technology and a steep learning curve. The benefit was demonstrated both in lower mortality and complications as well as better economics in terms of lower length of stay and hospitalization costs seen at high volume centers. We present an overview of the available literature that underscores the importance of hospital volume in complex structural heart disease interventions.     

Comparison between intrathoracic blood volume and cardiac filling pressures in the early phase of hemodynamic instability of patients with sepsis or septic shock

PURPOSE: The purpose of this study was to analyze three different variables of cardiac preload; central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP), and intrathoracic blood volume index (ITBVI) that served as the best indicator of cardiac function, that is, cardiac index (C1) or stroke index (SI). MATERIALS AND METHODS: This was a prospective study in 57 critically ill patients with sepsis or septic shock in whom 581 hemodynamic profiles were analyzed. One patient was included a second time after a period of 6 weeks. All patients were sedated and mechanically ventilated. Each patient had a 7.5-Frfive-lumen pulmonary artery catheter (PAC) and a 4-Fr catheter with an integrated thermistor and fiberoptic that was advanced into the descending aorta via a femoral artery sheath. The study was performed in the surgical intensive care unit of a university hospital. RESULTS: Linear regression analysis of the first profile for each case (n = 58) revealed a significant correlation between ITBVI and SI (r = 0.66). For comparison, correlations for PAOP/SI (r = 0.06) and CVP/SI (r = 0.10) were poor. The analysis of all second profiles showed that only the change in ITBVI reflected the change in SI (r = 0.67), whereas PAOP (r = 0.07) and CVP (r = 0.05) failed. Furthermore, a positive change in SI (n = 265) was most often associated with an increase in ITBVI (n = 189, 71.3%), less for PAOP (n = 122, 46.0%) and CVP (n = 137, 51.7%). A reduction in SI (n = 256) was accompanied by a decrease in ITBVI (n = 176, 68.8%), PAOP (n = 119, 46.5%), and CVP (n = 118, 46.1%). An increase in ITBVI (n = 269) was accompanied by an increase in SI in 189 cases (70.3%). In these, PAOP increased only in 91 (48.1%) and CVP in 101 cases (53.4%), respectively. Accordingly, a positive change in PAOP (n = 218) was associated with an increase in SI in 122 cases (56.0%). ITBVI increased in 91 (74.6%) and CVP in 84 (68.9%) of these cases. A decrease in ITBVI (n = 250) was associated with a decrease in SI in 176 cases (70.4%). Decreases in PAOP (n = 89, 50.6%) and CVP (n = 91, 51.7%) did not reflect these changes. However, when PAOP (n = 229) and SI decreased (n = 119, 52.0%), ITBVI decreased in 89 (74.8%) and CVP in 73 cases (61.3%). CONCLUSIONS: In comparison with cardiac filling pressures, ITBVI seems to be the more reliable indicator of cardiac preload in patients with sepsis or septic shock.     

Statistical combination schemes of repeated diagnostic test data

RATIONALE AND OBJECTIVES: When diagnostic tests are repeated and combined, a number of schemes may be adopted. Guidelines for their interpretations are required. MATERIALS AND METHODS: Three combination schemes, "and" (A), "or" (O), and "majority" (M), are considered. To evaluate these schemes, dependency by specifying kappa values quantifying repeated test agreement was structured. In a pilot study, the combined accuracies of magnetic resonance imaging using six different pulse sequences of medial collateral ligaments of the elbows of 28 cadavers, with eight having lesions artificially created surgically, were examined. Images were evaluated simultaneously by using a five-point ordinal scale. For each pulse sequence, individuals for whom the diagnosis varied from once to three repetitions were considered. RESULTS: Scheme M improves diagnostic accuracy when sensitivity and specificity of a single test exceed 0.5, with maximal improvement at 0.79. Under scheme A, sensitivity decreases to 0.38-0.59. Under scheme O, sensitivity increases to 0.53-0.79. Scheme M yields a small improvement, reaching 0.50-0.71. Under scheme A, specificity increases to 0.95-0.98. Under scheme O, specificity decreases to 0.91-0.98. Scheme M also yields a small improvement, reaching 0.94-0.98. CONCLUSION: Scheme A is recommended for ruling in diagnoses, scheme O is recommended for ruling out diagnoses, and scheme M is neutral. Consequently, different schemes may be used to optimize the target diagnostic accuracy.     

Insulin status differentially affects energy transduction in cerebral mitochondria from male and female rats

Effects of STZ diabetes and treatment with insulin on cerebral mitochondrial metabolism in the male and female rats were examined. Diabetic state resulted in generalized decrease in the state 3 respiration rates in the males with practically all the substrates except glutamate where the opposite effect was seen. Diabetic state had no adverse effect on the respiratory activity in the females. Insulin treatment had no restorative effect in the males. By contrast in the females, adverse effects were noted. The cytochromes contents decreased in STZ diabetes with the effect being more pronounced in the males; treatment with 1 unit of insulin restored the cytochromes contents. STZ diabetes also resulted in decreased dehydrogenases activities with the effect being more pronounced in the females: insulin treatment resulted in hyper-stimulation of glutamate dehydrogenase and succinate DCIP reductase activities; restoration of malate dehydrogenase activity was only partial. The results point out that STZ diabetes and insulin treatments differentially affect cerebral mitochondrial energy metabolism in the male and female rats.     

The effect of methylphenidate on the sleep-wake cycle of brain-injured patients undergoing rehabilitation

BACKGROUND AND PURPOSE: A number of neuro-stimulants are routinely used as part of post-acute care of hospitalized brain-injured patients. To our knowledge, the effect of these stimulants on the sleep-wake cycles of brain-injured patients undergoing rehabilitation has not been addressed. We examined the effect of one of the most commonly used neuro-stimulants, methylphenidate, on the sleep-wake behavior of brain-injured patients undergoing rehabilitation at a dedicated brain injury clinic. PATIENTS AND METHOD: For this study, records of patients admitted between January and December 1999 were scrutinized retrospectively for the data on observationally defined sleep-wake distribution. A total of 30 patients diagnosed with traumatic brain injury were identified as having been observed for a full 24h a day for at least 10 days. Some of these patients (n=17) were administered methylphenidate on clinical grounds. They served as the experimental group, while the unmedicated patients (n=13) served as controls. For the present analysis, the sleep-wake cycles were arbitrarily designated as nighttime and daytime, respectively. A cumulative sleep-wake quantity in a 24-h period was also observed. RESULT: The average number of hours of sleep during a 24-h period was not significantly different for the two cohorts. Similar trends emerged for the nighttime and daytime observations. On the whole, methylphenidate appears not to have unfavorable effects on sleep-wake cycles, presently defined as nighttime, daytime and 24-h, in the traumatic brain injury population. CONCLUSION: This study sought to gain better understanding of the effect of methylphenidate on daytime sleepiness and nighttime sleep, and the data suggest that administration of methylphenidate does not appear to have an adverse effect on sleep-wake quantity.