Cyclic nucleotide modulation of Na and K currents in the isolated node of Ranvier

The application of dibutyryl cyclic adenosine monophosphate (d-cAMP) to an isolated, voltage clamped node of Ranvier resulted in an increase in the peak inward and steady-state outward current amplitudes. Blocking K⁺ channels with TEA abolished the effects of d-cAMP on Na⁺ currents. Blocking Na⁺ channels with TTX revealed an increase in K⁺ current amplitude in response to d-cAMP. Application of a potent phosphodiesterase inhibitor, SQ20009, reproduced the effects of d-cAMP in the intact node, but with a latency in onset. These results suggest a physiological role for cAMP in the modulation of Na⁺ and K⁺ currents in myelinated peripheral nerve.     

Cure of Disseminated Cryptococcal Infection in a Renal Allograft Recipient After Addition of γ-Interferon to Anti-Fungal Therapy

The immunosuppressive regimens that are used in solid organ transplantation are potent inhibitors of Th0 as well as Th1 and Th2 cell-mediated immune responses. This predisposes patients to disseminated cryptococcal infections. Mortality in such patients remains very high despite advances in anti-fungal chemotherapy. We describe a case of disseminated cryptococcal disease in a renal allograft recipient that failed to respond to prolonged treatment with several anti-fungal drugs. However, addition of the immuno-modulator, interferon-gamma, resulted in the formation of granulomas and the resolution of his disease within 4-6 weeks. As we cannot find a similar example of combination therapy for disseminated cryptococcal disease in the solid organ transplant literature, we propose that interferon-gamma could be used in synergy with anti-fungal drugs to cure disseminated cryptococcal infections in solid organ transplant patients.     

The detraining and retraining of an elite rower: a case study

A heavyweight male rower, and current Olympic champion, undertook a laboratory-based incremental rowing test on four separate occasions; eight weeks prior to the Sydney Olympics (Pre OG), after eight weeks of inactivity (Post-IA), after 8 weeks of retraining (Post 8) and after a further 12 weeks of training (Post 20). Following the period of inactivity, peak oxygen uptake (VO2peak) declined by 8%, power at reference blood lactate concentrations declined by approximately 100 W (25%), and power at VO2peak was 20% lower. With eight weeks of retraining, rapid improvements were seen. For most parameters, however, the rate of improvement slowed and after 20 weeks of retraining the individual was approaching pre-Olympic levels. VO2 at lactate threshold as a percentage of VO2peak remained unchanged. These results show that detraining in the elite athlete can be pronounced, with rapid improvements upon retraining which slow, so that retraining takes considerably longer to achieve than detraining did. Complete cessation of training should be limited to short periods only in the preparation of the elite heavyweight rower. Any break should, if possible, include 'maintenance training'. In this way any decrements in those physiological parameters associated with 2000 m rowing performance will be minimised.     

Performance evaluation of a draw-over vaporizer with a nonrebreathing circuit during simulated adverse conditions

Study Objective: Performance evaluation of a draw-over vaporizer with a nonrebreathing circuit during simulated adverse conditions.

Design: Open laboratory study.

Setting: University hospital laboratory.

Materials and Interventions: The output (%) of a temperature-compensated Ohmeda Cyprane PAC (portable anesthesia complete) draw-over vaporizer (Ohmeda, Madison, WI) using isof urane attached to a nonrebreathing circuit was tested in the laboratory during manual ventilation under normal and simulated adverse conditions. The adverse conditions tested were high ambient temperature and static and dynamic positional variation.

Measurements and Main Results: The results show that the output bias of the PAC vaporizer has a generally consistent profile as tested, except when placed in the 180° full-inversion or 90° anterior-tilt position. We also conducted trials with the Penlon ventilator (Ohmeda, Abingdon, Oxford, U.K.) attached to the circuit at each of its input ports. Ventilation at one input port produced dangerously high airway pressures (within the circuit), thus supporting the manufacturer's recommendation against the use of this port for positive-pressure ventilation. Using the recommended port, the test lung was seen to inflate and deflate appropriately, but, surprisingly, no vapor output was detected by the agent monitor at any vaporizer setting when using the ventilator at the recommended port.

Conclusion: Anesthetists should be aware of the pitfalls and possible problems that may be associated with this type of anesthetic delivery system.