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We explore the rate-dependent dynamic response of periodically paced bullfrog (Rana catesbeiana) cardiac muscle. Alternans (2:2 behavior) occur in 35% of animals and 2:1 $ 1:1 bistability in 74% of animals. In addition, we observe 2:2 $ 2:1 bistablility. We discuss the implications of these results for two map-based models of cardiac dynamics. The high(More)
We studied the effects of supplementing nitrous oxide-oxygen anaesthesia with halothane (1 MAC end-tidal concentration) on the motor evoked potential recorded in the extradural space of eight patients before corrective surgery for idiopathic adolescent scoliosis. The motor cortex was stimulated electrically through the scalp. An additional eight patients in(More)
The concept of postoperative fatigue has been developed to explain the feelings of malaise and the reduction in activity during the convalescent period that follows surgery in humans. Fatigue has been assumed to reflect the degree of surgical trauma and to be a consequence of muscle weakness caused by physiological sequelae of the trauma. The evidence is(More)
We studied the effects of supplementing anaesthesia with halothane (up to 1.5%, inspired) on the somatosensory evoked potential recorded in the extradural space of six patients before corrective surgery for idiopathic adolescent scoliosis. A further six patients in whom anaesthesia was supplemented with thiopentone acted as a control group. Halothane 1.5%(More)
Each "20 Questions" publication is designed to be a concise, easy-to-read introduction to an issue of importance to directors.The question format reflects the oversight role of directors which includes asking management – and themselves – tough questions. The questions are not intended to be a precise checklist, but rather a way to provide insight and(More)
OBJECTIVE To test the theory that postoperative fatigue is an aspect of the emotional, not physiological, response to surgery, we examined whether fatigue is a component of subjective experience after surgery and whether it is related to subjective physical or emotional state. METHODS Patients (N=160) undergoing hip or knee arthroplasty were assessed(More)
INTRODUCTION Studies of the electrical dynamics of cardiac tissue are important for understanding the mechanisms of arrhythmias. This study uses high-frequency pacing to investigate the dynamics of sheep atria. METHODS AND RESULTS A 504-electrode mapping plaque was affixed to the right atrium in six sheep. Cathodal pacing stimuli were delivered to the(More)
Fatigue has been widely assumed to increase after major surgery, and possible physical explanations have been intensively investigated. Nevertheless, existing data are almost exclusively from abdominal surgery and are based on the use of a single visual analogue scale. Moreover, no physical basis has been found. The present study used a more homogeneous(More)