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Background and purpose:No information is available concerning the effects of anaesthetics in the most frequently used in vivo pro-arrhythmia model. Accordingly, in this study we examined the effect of pentobarbital, propofol or α-chloralose anaesthesia on the pro-arrhythmic activity of the class III anti-arrhythmic dofetilide in α1-adrenoceptor-stimulated rabbits.Experimental approach:Rabbits anaesthetized intravenously with pentobarbital, propofol or α-chloralose were infused simultaneously with the α1-adrenoceptor agonist phenylephrine (15 μg kg−1 min−1, i.v.) and dofetilide (0.04 mg kg−1 min−1, i.v.). The electrocardiographic QT interval, the T peak–T end interval and certain QT variability parameters were measured. The heart rate variability and the baroreflex sensitivity were utilized to assess the vagal nerve activity. The spectral power of the systolic arterial pressure was calculated in the frequency range 0.15–0.5 Hz to assess the sympathetic activity.Key results:Pentobarbital considerably reduced, whereas propofol did not significantly affect the incidence of dofetilide-induced torsades de pointes (TdP) as compared with the results with α-chloralose (40% (P=0.011) and 70% (P=0.211) vs 100%, respectively). In additional experiments, neither doubling of the rate of the dofetilide infusion nor tripling of the rate of phenylephrine infusion elevated the incidence of TdP to the level seen with α-chloralose. None of the repolarization-related parameters predicted TdP. The indices of the parasympathetic and sympathetic activity were significantly depressed in the α-chloralose and propofol anaesthesia groups.Conclusions and implications:In rabbits, anaesthetics may affect drug-induced TdP genesis differently, which must be considered when results of different studies are compared.British Journal of Pharmacology (2008) 153, 75–89; doi:10.1038/sj.bjp.0707536; published online 29 October 2007 [ABSTRACT FROM AUTHOR]

Background: The combination of laser Doppler flowmetry and non-invasive blood pressure monitoring allows the continuous observation of cutaneous vascular resistance (CVR). Continuous recording of unmodulated skin blood flow (SBF) is very sensitive to artefacts, rendering the method unreliable. In contrast, intermittent short lasting challenges of the CVR by cardiovascular autonomic reflexes may provide information about the responsiveness of the sympathetic nervous system in the skin.Methods: Eleven patients with below-wrist hand surgery (six males and five females; aged 35.2+/-7.1 years) performed Valsalva maneuver following axillary blockade. Skin blood flow was continuously monitored on the forearm of the side axillary blockade, as well as on the contra-lateral forearm, which was used as the control. The responses were expressed as changes compared with the baseline level derived from a resting period of 30 s. The maximal change in CVR was determined during the late strain phase of the Valsalva maneuver on both sides. For numerical comparison the change in CVR on the axillary blockade and control sides were simultaneously calculated.Results: During the Valsalva maneuver a significant increase in CVR was observed on the control side with a maximum value during the late strain phase (baseline 0.18+/-0.1 and late strain phase 0.42+/-0.2 relative units; P<0.01). In contrast, only minimal changes were detected on the side of axillary blockade in CVR (baseline 0.17+/-0.8 and late strain 0.16+/-0.2 relative units; P=NS).Conclusions: Our findings support the disputed hypothesis that the human skin microvasculature is involved in baroreflex regulation under thermoneutral conditions. The determination of baroreflex stimulus-induced microvascular responses may serve as a feasible method for monitoring the effectiveness of sympathetic blockade. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the baroreflex sensitivity (BRS) assessed by the new, non-invasive, spontaneous sequence method (BRS-sequence) with the Valsalva manoeuvrebased BRS. Fourteen healthy volunteers were studied in the supine position, during 60° head-up tilt (HUT) and during −30° head-down tilt (HDT). Blood pressure and R-R intervals were continuously and non-invasively recorded using a Finapres device. The BRS-sequence was assessed by analysing the slopes of spontaneously occurring sequences of three or more consecutive beats in which systolic blood pressure and R-R interval of the following beat increased or decreased in the same direction in a linear fashion; it was compared with data obtained during the Valsalva manoeuvre in each position. The time and frequency domain indices of R-R interval variability were also evaluated. The mean difference of BRS between the two non-invasive methods was 3.86 ms/mmHg with a standard deviation of 9.14 ms/mmHg. BRS was decreased during HUT and increased during HDT as assessed by both techniques. The changes in BRS were associated with vagal withdrawal and sympathetic activation during HUT and enhancement in the cardiac vagal tone and reduction in the sympathetic activity during HDT. We conclude that the BRS-sequence technique provides a reliable method to study the neural control of the circulation, although the body position in consecutive measurements needs to be standardized. [ABSTRACT FROM AUTHOR]

: Several studies have shown that heart rate variability plays an anti-oscillatory role in the regulation of blood pressure variability in humans. We tested whether systolic blood pressure variability in patients with a fixed ventricular pacemaker rhythm differs from that in patients with sinus rhythm. : In 18 patients with a fixed ventricular pacemaker rhythm and in ten age-matched patients with sinus rhythm the systolic blood pressure oscillation and the low and high-frequency spectral components of systolic blood pressure were studied in the resting supine position during spontaneous breathing and during forced deep ventilation of 6 cycles. min. Patients with a pacemaker had a higher amplitude of systolic blood pressure oscillation than control subjects during spontaneous breathing (13.5 ± 2.0 mmHg vs 6.4 ± 1.6 mmHg, P=0.035), and a slight but not significant difference also persisted during forced deep ventilation (19.0 ± 2.3 mmHg vs 15.0 ± 2.3 mmHg, P=0.18). The increment in systolic blood pressure fluctuation from spontaneous breathing to forced deep ventilation was less marked in the pacemaker group than in the control subjects (40% vs 130%, P=0.43). Although all the systolic blood pressure spectral components of the pacemaker patients were higher during both spontaneous breathing and forced deep ventilation, the differences between the two groups did not reach statistical significance. : Our observations in patients with a fixed ventricular pacemaker rhythm suggest that the mechanical effects on the intrathoracic vessels and the consecutive stroke volume changes are responsible for respiration-related systolic blood pressure oscillation and reflex systolic blood pressure changes. [ABSTRACT FROM PUBLISHER]

An abstract of the study "Alterations in Autonomic Nervous System Activity in Hypertrophic Cardiomyopathy: Effects of Body Position," by L. Halmai and colleagues is presented.