Dynamic Beat-to-Beat QT-RR Relationship During Physiotherapy Effort in Elderly Patients Without Primary Heart Disease

The ECGs from 18 patients hospitalized in a rehabilitation setting, following surgery for hip fracture, were examined to characterize the dynamic behavior of uncorrected QT interval in relation to changing RR interval during physiotherapy effort. ECG waveforms were analyzed to extract beat-to-beat QT and RR intervals using a computerized ECG Analyzer (CEA-1100). The method of defining the QT and RR intervals is based on performing multiple cross-correlations that enable rejection of artifacts from the analysis. The relationship between the RR and QT intervals was found using the following general formula QTi = cRRi-1b. Linear regression was performed on the logarithms of QT and RR measurements obtained to estimate the constant (a = log c) and the slope (b) values, reflecting the dynamic change of QT during physiotherapy effort. Having these two values, the dynamic QT extrapolated to a heart period of 1 second (QTcd) was calculated. The results were compared to the conventional corrected static QT according to the Bazzet formula (QTcs). The mean values of constants (a = log c) and slopes (b) over all patients were found to be 1.61 +/- 0.23 and 0.33 +/- 0.08, respectively, giving a QT (ms) heart-period (ms) dynamic relation of QTi = 41 x RR(i-1)0.33. The correlation between the dynamic QT and the static QT intervals was not significant. The mean values of the QTcd and QTcs intervals were significantly different (392 +/- 25 ms vs 434 +/- 28 ms; P < 0.0001). This dynamic measurement method of QT intervals may provide additional information on normal and abnormal cardiac repolarization in health and disease, helping in the diagnosis of cardiac disorders and arrhythmia risk.     

Cyclosporin Increases the CNS Sensitivity to the Hypnotic Effect of Phenobarbitone but not Ethanol in Rats

Abstract— The purpose of this investigation was to determine whether repetitive administration of cyclosporin affects the pharmacodynamics of phenobarbitone- and ethanol-induced anaesthesia. Sabra male rats received either cyclosporin (50 mg kg^?1 day^?1, i.m.) for four days, or the same volume of the vehicle. Two hours after the last cyclosporin dose, phenobarbitone or ethanol solutions were infused intravenously at a constant rate until the onset of anaesthesia. Repetitive treatment with cyclosporin increased the CNS sensitivity to the hypnotic action of phenobarbitone. This was evidenced by the lower CSF phenobarbitone concentration, at the onset of the hypnotic effect, in the cyclosporin-treated group vs control values (115 ± 4 vs 93 ± 7 mg L^?1, P = 0·01). However, the same pretreatment had no apparent effect on the pharmacodynamics of ethanol-induced sleep. It is suggested that anaesthesiologists must be alert to the possible increase in brain sensitivity when placing cyclosporin patients under anaesthesia with barbiturates.     

MIDAZOLAM ACTS SYNERGISTICALLY WITH FENTANYL FOR INDUCTION OF ANAESTHESIA

The induction dose—response of midazolam was comparedwith the dose—response of its combination with fentanyland with that of fentanyl alone in three groups of 60 unpremedicated,ASA physical status I or II women undergoing minor gynaecologicalsurgery. The end-point of induction of anaesthesia was inabilityto open eyes upon command. Dose—response curves were determinedfor each group with a probit procedure and compared with anisobolographic analysis. Midazolam was found to act in synergismwith fentanyl for induction of anaesthesia. Twenty-five percentof the ED₅₀ of fentanyl was required in combination with 23%of the ED₅₀ for midazolam to achieve the ED₅₀ of the combination.This degree of synergism may explain mutual potentiation betweenopioids and benzodiazepines reported previously