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Summary Analysis of beat-to-beat fluctuations of heart rate and blood pressure is a promising new approach to the clinical diagnosis and management of alterations in cardiovascular regulation. We investigated the effects of three induction agents on beat-to-beat heart rate and blood pressure fluctuations in man. Beat-to-beat fluctuations were analysed by spectral analysis. Two spectral areas are of main interest. One area is centred on the respiratory frequency and shifts with changes in respiratory rate (High Frequency area). These high frequency flucuations in heart rate are caused by respiratory-induced blood pressure fluctuations, mediated by the vagus nerve through the baroreflex mechanism. Variability in the Low Frequency area, which occurs between 0.06 and 0.12 Hz is considered to be related to haemodynamic fluctuations due to the sympathetic baroreflex control loop of vasomotor activity and heart rate. Results from our study indicate that thiopentone, etomidate and propofol show considerable differences in their effects on beat-to-beat variability of heart rate and blood pressure. These differences can be explained by their specific effects on the cardiovascular system.

OBJECTS: A case of a Suriname female occipito-parietal to occipito-parieto-temporal craniopagus twins is described. The girls were transferred to the VU University Medical Center (VUmc) in Amsterdam, the Netherlands, for further diagnostics and to analyze whether surgical separation was feasible and ethically justifiable. The multifactorial aspects of different treatment options are discussed.METHODS: The twins underwent multiple investigations by a multidisciplinary team. Advanced imaging techniques with 3D-CT scan, MRI and MRA scans, image fusion techniques and, most importantly, cerebral angiography with balloon occlusion tests were performed.CONCLUSIONS: Because of a shared venous ring, with preferential drainage to the left child, and which endovascular balloon occlusion showed could not be separated, surgical separation of the twins with a fair chance of survival without additional neurological damage and with prospects of a good quality of life was regarded as impossible. In accordance with the parents' wishes, the twins were not separated and offered optimal integral conservative treatment.

After having monitored haemodynamics during haemodialysis, we examined autonomic nervous function in rest prior to a next dialysis session in 28 patients on chronic intermittent haemodialysis. The aim was to compare intradialytically hypotensive with stable patients to assess whether blood pressure regulating mechanisms were related to basal autonomic function, assessed as heart rate variability (HRV) tested by means of the deep breathing test, the lying-to-standing test, and the Valsalva maneuver. Impedance cardiography was used to determine stroke volume and cardiac output during dialysis. In addition, blood pressure was registered automatically and systemic vascular resistance calculated. Blood volume variation was monitored by an on-line optical device. Intradialytic hypotension was observed in 10 patients (36%). Systemic vascular resistance in hypotensive patients decreased considerably (-14.0+/-5.9%), while it increased in stable patients (+9.9+/-4.6%, p = 0.004). Heart rate rose significantly in hypotensive patients (11.5+/-3.8%) in comparison to stable patients (-0.2+/-2.8%, p = 0.02). However, no significant differences in autonomic function were observed between hypotensive and stable patients. Although both groups showed impaired autonomic function, no significant correlation between changes in haemodynamics during dialysis and autonomic function at rest could be ascertained. In conclusions, hypotension during haemodialysis is not related to a patient's autonomic function at rest. This suggests that structural neuronal differences are not responsible for the severe decrease in systemic vascular resistance in intradialytic hypotension.

In this experimental study we measured the magnetocardiograms (MCGs) of 17 normals at 42 measuring sites in a plane near the chest. The recordings were made in an unshielded environment with a single channel second-order SOUID gradiometer. From these recordings spatial maps were constructed of the atrial depolarisation and repolarisation. The two series of maps were found to be dipolar, but opposite in sign for 14 of the 17 subjects. The relatively small change in the amplitude and pattern of the atrial repolarisation maps built up out confidence in the method of subtracting a computed mean repolarisation map from the maps obtained during the last 40 ms before the QRS-onset. This method of separating His-Purkinje activity from atrial repolarisation led to distinct dipolar patterns in 9 out of the 17 cases. The direction and location of the associated electric current dipole was in good agreement with what can be expected electrophysiologically for His-Purkinje activation.