The effect of a repeat bout of exercise on muscle injury in persons with spinal cord injury.

Following an initial bout of damaging exercise, a successive bout of similar exercise typically results in less injury, known as the "protective effect". Unloading due to spinal cord injury (SCI) increases the susceptibility to contraction-induced muscle injury. We tested the hypothesis that two bouts of isometric actions would evoke the same damage in the quadriceps femoris (QF) of patients with SCI. Six male subjects [32 (5) years old, 182 (9) cm, 81 (21) kg, injury level C6-T7, 6 (2) years post-injury, mean (SD)] were tested at two time points (Time1, Time2), separated by 8 weeks. Magnetic resonance images were taken of the QF prior to, immediately after, and 3 days after electromyostimulation (EMS) that evoked isometric knee extension. EMS (50 Hz) consisted of five sets of ten contractions (2 s on/6 s off, 1 min b/t sets) followed by three sets of ten contractions (1 s on/1 s off, 30 s b/t sets). Relative cross-sectional area of stimulated and injured skeletal muscle was obtained by quantifying pixels with an elevated T2. Relative area of stimulated QF was the same for both time points [92 (6)% and 89 (7)%] as was torque loss (approximately 55%). Three days post-EMS, the relative area of stimulated QF injured was not different between time points [30 (14)% vs 29 (17)%, P>0.05]. These results indicate an absence of a protective effective for repeat exercise bouts separated by 8 weeks in SCI patients using EMS.

Variable frequency trains enhance torque independent of stimulation amplitude.

AIM: Variable frequency trains have been reported to enhance force of fatigued human skeletal muscle. More rapid calcium turnover and/or enhanced stiffness may be responsible for the augmented torque-time integral during surface stimulation at moderate amplitude. In contrast, it has recently been suggested that variable frequency train enhancement occurs only at low forces as a result of preferential stimulation of fast fibres and/or altered motor unit recruitment. If correct, this would limit the practical benefit of variable frequency trains. Accordingly, we tested the hypothesis that torque augmentation by variable frequency trains in fatigued skeletal muscle was independent of stimulation amplitude. METHODS: The m. quadriceps femoris of six males was stimulated with constant frequency trains (six 200-micros square waves separated by 70 ms) or variable frequency trains (first interpulse interval 5 ms) at an amplitude that initially evoked approximately 25 or approximately 50% of maximal voluntary isometric torque. RESULTS: After 180 constant frequency trains (50% duty cycle), isometric peak torque decreased approximately 63%. In fatigued muscle, variable frequency trains enhanced the torque-time integral by approximately 23% over that for constant frequency trains and this effect was independent of stimulation amplitude. This was due to greater peak torque and less slowing of rise time. CONCLUSION: These responses show that the torque-time integral can be enhanced at both moderate and high stimulation amplitudes. As such, it is suggested that neither recruitment nor preferential activation of fast muscle is responsible for the "catch-like" property that can be demonstrated in fatigued human skeletal muscle.

Management of cutaneous malignant melanoma by dermatologists of the American Academy of Dermatology. II. Definitive surgery for malignant melanoma.

BACKGROUND: During the past few decades there has been increasing interest and training in dermatologic surgery. OBJECTIVE: Our purpose was to determine to what extent members of the American Academy of Dermatology (AAD) are involved in the surgical management of patients with malignant melanomas (MMs), comparing 1982 with 1992. METHODS: Members of the AAD practicing in the United States (N = 7412) were sent a questionnaire that surveyed their role in the definitive treatment of patients with MMs and the surgical margins of normal-appearing skin that they used or recommended for melanomas of various thicknesses. RESULTS: Sixty-four percent of the respondents stated that they performed the definitive surgery for in situ melanoma in 1992, a 14% increase from 1982. Although a significantly greater percentage of dermatologists were performing the definitive surgery for invasive melanoma in 1992 (28%) compared with 1982 (14%), the majority continued to refer their patients to surgical colleagues for definitive treatment. There has been a narrowing of surgical margins recommended or used for melanomas of all thicknesses. In addition, regional differences of the role of the dermatologist in surgical management of patients with MM were observed. CONCLUSION: An increasing proportion of dermatologists are involved in the surgical management of patients with MMs. Most dermatologists appear to be in accord with the guidelines for surgical margins currently recommended in the literature.

An estimate of the incidence of malignant melanoma in the United States. Based on a survey of members of the American Academy of Dermatology.

BACKGROUND: The incidence of malignant melanoma (MM) in the United States (US) must be known to accurately evaluate the costs that MM imposes on the health care system and society in general. Furthermore, knowledge of the incidence is needed to determine the benefit of MM prevention programs. OBJECTIVE: To obtain an estimate of the incidence of MM in the US. METHODS: The data for this study were collected by means of a questionnaire that was sent to all members of the American Academy of Dermatology practicing in the US (N = 7412). RESULTS: Based on the mean number of MMs seen annually per dermatologist in each state and the number of dermatologists per state, the number of new in situ and invasive MMs in the US in 1992 was calculated to be 80,000. This translates to an incidence of 32 MMs per 100,000 persons. CONCLUSIONS: Our estimate of 80,000 new MMs diagnosed in 1992 in the US suggests that MM places much greater burdens on the US health care system and society than that based on current published estimates.

Extradural sufentanil by patient-controlled analgesia or nurse-administered compared with optimal morphine in a high dependency unit: effects on oxygenation and pain relief after abdominal surgery.

The incidence of apnoeic episodes (> 12 s) was measured in 30 surgical patients allocated randomly to one of three analgesic regimens and all nursed in a high dependency unit. Ten patients received i.m. morphine (mean 52 (range 30-80) mg), administered on request. The remaining 20 patients received extradural sufentanil as an initial bolus dose of 50 micrograms followed by a bolus of 10 micrograms, either self-administered using PCA (10 patients: mean 275 (range 130-450) micrograms) or administered by a nurse on request (10 patients: 144 (70-200) micrograms). With i.m. morphine apnoeic episodes were maximal 2-3 h after administration while after extradural sufentanil, apnoeas were maximal within a few minutes.

Epidural bupivacaine for aortic surgery. The effect of dilution on the quality of analgesia.

Twenty patients undergoing elective abdominal aortic aneurysm repair were randomly allocated to two groups and studied for 24 h following surgery. Postoperative analgesia was provided by epidural bupivacaine infusion and intravenous patient-controlled 0.05 mg boluses of alfentanil. One treatment group received 7 ml.h-1 of a 0.25% solution of bupivacaine, the other 25 ml.h-1 of a 0.07% solution. The rate of infusion was thus 17.5 mg.h-1 in both groups. Patients receiving 7 ml.h-1 of epidural infusate required more doses of alfentanil (median 26.5, range 0-50) than the group receiving 25 ml.h-1 of the dilute infusion (median 3.0, range 0-16). It is concluded that 17.5 mg.h-1 of bupivacaine infused into the epidural space produces better analgesia when infused in a volume of 25 ml.h-1 (0.07%) than when given in a volume of 7 ml.h-1 of solution (0.25%).

Bacterial growth in isoflurane vapour.

Pathogenic bacteria were grown on nutrient agar in a mixture of air and isoflurane vapour, and in air alone. The presence of isoflurane vapour in concentrations considerably in excess of those used either for anaesthesia or for sedation in intensive care had no effect either on the rate of bacterial growth or on the viability of colony forming units.

Efficiency of breathing systems A and D in the Carden Ventmasta ventilator.

We have compared the efficiency of the enclosed Magill attachment (System A) and the co-axial System D (Bain) in the Carden Ventmasta ventilator using both systems, each under five different ventilatory conditions, in each of five anaesthetized patients. Efficiency was assessed in terms of the effective alveolar ventilation as a fraction of the fresh gas flow. For System A, efficiency increased from a mean of 0.37 when the total ventilation was only 50% of the fresh gas flow, to a mean of 0.74 when ventilation was 2.3 times the fresh gas flow. The efficiency was substantially and significantly less with System D: 75% of that for System A at the smaller total ventilation (95% CI 65-85%) and 65% at the larger (95% CI 59-71%). A critical examination is made of conflicting definitions and terminology of the efficiency of breathing systems.