Interference of antibiotic therapy on blood cultures time-to-positivity: analysis of a 5-year experience in an oncological hospital.

This study performed a retrospective analysis on the relationship between blood culture time-to-positivity (TP) and type of isolated microorganism, antibiotic administration, and immunological status of the patients. We analyzed the data related to 1,218 positive blood cultures. When compared to Gram positive bacteraemia, the percentage of Gram negative growth was higher and the mean TP significantly shorter (p < 0.0001). In patients receiving antibiotics, median and mean TPs of blood culture were different for Gram positive bacteraemia (log-rank p = 0.0022, Wilcoxon p < 0.0001) but not for Gram negative (log-rank p = 0.4011, Wilcoxon p = 0.1585). No statistically significant effect on TP was found for sampling site, interaction between sampling site and antibiotic administration, and immunological status of the patient. In conclusion, TP is independent of antibiotic therapy in cases of Gram negative bacteraemia, while for Gram positive bacteraemia a prolongation of TP occurs.

Laboratory-based management of microbiological alerts: effects of an automated system on the surveillance and treatment of nosocomial infections in an oncology hospital.

BACKGROUND: Prevention and surveillance programs are key to contain Nosocomial Infections (Nis). At the European Institute of Oncology, surveillance based on ex-post data collection has been done since the inception of hospital activity; laboratory-based surveillance of microbiological alert was not standardized. This study describes the issues related to the recent introduction into the hospital routine of a laboratory-based automated surveillance system and its clinical impact on monitoring and treatment of Nis. METHODS: An interdisciplinary team defined the alerts and the actions to be taken in response; recipients of the alert messages were identified and software was programmed. Program features were created so their employment would generate a prompt notification of clinically critical results. After a training period, the program was introduced in the hospital routine. RESULTS: There were a total of 150 generated alerts; the main alert related to microorganisms requiring prompt patient isolation and/or public notification. Clinical use of the program was relevant in detection and immediate notification of Cytomegalovirus active infection in stem cell recipients and central venous catheter related candidemia: the prompt administration of adequate treatment was possible hours earlier compared to the previous approach. CONCLUSIONS: A laboratory-based automated surveillance system is effective in facilitating the management of Nis; its clinical employment also leads to important clinical advantages in patient care.

Initial clinical experience with a fully automatic in-hospital external cardioverter defibrillator.

Sudden cardiac death due to ventricular tachyarrhythmia remains a significant problem in the in-hospital setting. Although the probability of survival is closely correlated with the rapidity of a response by qualified personnel, response times can be prolonged, even in specialized care units. In an effort to decrease response time, a fully automatic external cardioverter defibrillator was recently devised. This device was evaluated in the in-hospital setting to assess safety and efficacy. A total of 79 patients were studied in a multicenter trial. Patients were monitored with fully functional devices in the electrophysiology laboratory (51 patients) and in the cardiac care unit (28 patients). Performance of the device was assessed by comparing automatic responses to any sustained change in cardiac rhythm, either spontaneous or induced, to a retrospective review of stored ECG data and programmed parameters. During a total duration of 964 hours of monitoring, there were 99 episodes of sustained tachycardia. Therapy was appropriately delivered or advised in all episodes. Therapy was advised in one episode of supraventricular tachycardia. There were no episodes of inappropriate therapy delivery. There were no complications or adverse events. The device performed with a sensitivity of 100% and specificity of 98.8% with an average response time of 22 seconds. In conclusion, this automatic external defibrillator was safe, effective, and functioned as designed. Significant improvement in response time to life-threatening ventricular tachyarrhythmia in the in-hospital setting would be expected if this technology was widely adopted.

Chronic rise in defibrillation threshold with a hybrid lead system.

Nonthoracotomy leads have become standard for implantable cardioverter-defibrillators (ICD) because of low perioperative morbidity, mortality, and expense. Reported increases in defibrillation thresholds (DFTs) with these lead systems, however, have raised the possibility of an eventual loss of defibrillation efficacy. The mechanism of this increase is unknown. In contrast, defibrillation efficacy of traditional epicardial lead systems has been demonstrated to remain relatively stable. In the present study, we examined the implantation and chronic DFTs in 45 patients with a hybrid system (a high right atrial coil and an extrapericardial patch) that combines elements from both the thoracotomy and nonthoracotomy approach. The mean threshold increased from 11.7 +/- 3.0 to 15.8 +/- 10.0 J (p < 0.001) and mean impedance increased from 37.0 +/- 7.7 to 48.8 +/- 9.0 ohms (p < 0.0001). There was a marked (> or = 10 J) increase in DFT in 11 patients (24%) including 4 who required reoperation to obtain an adequate safety margin. The increase in DFT was unrelated to any of the analyzed variables. We conclude that the presence of an extrapericardial patch does not prevent the increase in DFT reported with nonthoracotomy lead systems. This increase is unpredictable and occurs in almost 25% of patients.

Acute electrophysiologic effects of amiodarone in patients with congestive heart failure.

Patients with severe congestive heart failure (CHF) are at increased risk for atrial and ventricular arrhythmias and sudden cardiac death. Amiodarone is generally well tolerated by this population and has a low proarrhythmic potential. Because of its peculiar kinetics, amiodarone requires a prolonged loading period, necessitating lengthy hospitalizations in a monitored setting. This study was planned prospectively to assess the electrophysiologic effects of an abbreviated high-dose oral load of amiodarone in patients with severe CHF and known or suspected life-threatening ventricular arrhythmias. Fifteen patients with stable CHF and known or suspected life-threatening ventricular arrhythmias underwent baseline electrophysiologic study. The study was repeated after administration of oral amiodarone, 50 mg/kg/day for 2 days in 8 divided doses (mean dose 6.9 +/- 0.4 g). After amiodarone administration, there was prolongation in virtually all conduction times and refractory periods. The prolongation of refractoriness was most pronounced in the atrium. Ventricular effective refractory periods demonstrated reverse frequency dependence. We conclude that a brief high-dose oral load of amiodarone is well tolerated by patients with CHF. It has marked and diffuse electrophysiologic actions suggestive of class I and III effects in addition to antiadrenergic and calcium blocking action. These effects are especially pronounced in the atrium.

High dose oral amiodarone loading exerts important hemodynamic actions in patients with congestive heart failure.

OBJECTIVES: The purpose of this study was to use invasive monitoring to analyze the hemodynamic effects of both a large single dose and a 48-h loading regimen of amiodarone in patients with severe heart failure. BACKGROUND: Amiodarone is frequently used as an antiarrhythmic agent in patients with congestive heart failure, but the impact of this agent on cardiac function remains controversial. Recent successful experience with a rapid oral load of amiodarone makes invasive testing of the hemodynamic effects of oral amiodarone in such patients now feasible. METHODS: After baseline hemodynamic assessment (using balloon-tipped pulmonary artery catheters) and electrocardiographic measurements, 16 patients received 12.5 mg/kg body weight of amiodarone orally. Hemodynamic measurements were obtained hourly for 4 h. Patients then received this dose an additional seven times over the next 2 days. Hemodynamic variables and QRS, QT and PR intervals were measured after 48 h of treatment. RESULTS: Vasodilation was seen between 1 and 3 h after drug administration. Systemic vascular resistance decreased 326 +/- 135 dynes.s.cm-5, cardiac index increased 0.24 +/- 0.08 liters/min per m2 and mean arterial pressure decreased 6 +/- 3 mm Hg (mean +/- SEM, all p < 0.05). After 48 h of amiodarone administration, heart rate decreased 23 +/- 3 beats/min (p < 0.005), stroke volume increased 9 +/- 3 ml (p < 0.005), cardiac index decreased 0.23 +/- 0.09 ml/min per m2 (p < 0.05), pulmonary capillary wedge pressure increased 4 +/- 1 mm Hg (p < 0.01), right atrial pressure increased 3 +/- 1 mm Hg (p < 0.005) and QT and PR intervals were markedly prolonged (p < 0.01). CONCLUSIONS: Although the first dose caused vasodilation, a complete loading regimen of amiodarone produced a decreased heart rate with elevated filling pressures and decreased cardiac index.

Effects of zinc on hepatic ornithine transcarbamylase (OTC) activity.

The aim of the study was to examine the effects of oral zinc supplementation on liver ornithine transcarbamylase activity (OTC), a key enzyme in the urea cycle, in cirrhotic rats. OTC was studied in two groups of rats treated with carbon tetrachloride (CCl4): the first received zinc in the drinking water during the induction of cirrhosis; the second was the control group. Cirrhotic rats which received zinc supplementation showed an increase in liver OTC activity, positively correlated with serum and hepatic zinc content. The results suggest that zinc dietary supplementation may modify hepatic OTC activity and, therefore, plasma ammonia levels in cirrhotic rats.

Adherence of Candida to corneal surface.

In the pathogenesis of mycotic infections, adherence of the microbes to surface structures prior to invasion appears to be the initial and essential step in a susceptible host. Adherence and inhibition of adherence of Candida albicans to rabbit corneal surface was investigated in vitro by light and scanning electron microscopic examinations. The results indicate that blastospores of Candida albicans rarely bind to intact corneal epithelium, but consistently adhere to stroma denuded of epithelium. Such adherence was inhibited by concanavalin A. With its strong affinity for the yeast cell wall carbohydrate mannan, concanavalin A may block the site of attachment of yeast cells to the corneal surface.