Biomedical subjects

Krista Vandenborne

Publications and source records attributed to Krista Vandenborne.

22 records · Page 2Linked to original sources

PubMed2002

Effects of muscle activation on fatigue and metabolism in human skeletal muscle.

Increasing stimulation frequency has been shown to increase fatigue but not when the changes in force associated with changes in frequency have been controlled. An effect of frequency, independent of force, may be associated with the metabolic cost resulting from the additional activations. Here, two separate experiments were performed on human medial gastrocnemius muscles. The first experiment (n = 8) was designed to test the effect of the number of pulses on fatigue. The declines in force during two repetitive, 150-train stimulation protocols that produced equal initial forces, one using 80-Hz trains and the other using 100-Hz trains, were compared. Despite a difference of 600 pulses (23.5%), the protocols produced similar rates and amounts of fatigue. In the second experiment, designed to test the effect of the number of pulses on the metabolic cost of contraction, 31P-NMR spectra were collected (n = 6) during two ischemic, eight-train stimulation protocols (80- and 100-Hz) that produced comparable forces despite a difference of 320 pulses (24.8%). No differences were found in the changes in P(i) concentration, phosphocreatine concentration, and intracellular pH or in the ATP turnover produced by the two trains. These results suggest that the effect of stimulation frequency on fatigue is related to the force produced, rather than to the number of activations. In addition, within the range of frequencies tested, increasing total activations did not increase metabolic cost.

Adenosine Triphosphate↗

PubMed2002

Factors in fatigue during intermittent electrical stimulation of human skeletal muscle.

During an electrically elicited isometric contraction, the metabolic cost of attaining is greater than of maintaining force. Thus fatigue produced during such stimulation may not simply be a function of the force-time integral (FTI), as previously suggested. The goal of the present study was to evaluate fatigue produced in human medial gastrocnemius by intermittent, isometric electrical stimulation with trains of different frequencies (20, 40, or 80 Hz) and durations (300, 600, or 1,200 ms) that produced different peak forces and FTIs. Each subject (n = 10) participated in a total of six sessions. During each session, subjects received a pre- and postfatigue testing protocol and a different, 150-train fatiguing protocol. Each fatiguing protocol used only a single frequency and duration. The fatigue produced by the different protocols was correlated to the initial peak force of the fatiguing protocols (r2= 0.74-0.85) but not to the initial or total FTI. All of the protocols tested produced a proportionately greater impairment of force in response to low- vs. high-frequency stimulation (i.e., low-frequency fatigue). There was no effect of protocol on low-frequency fatigue, suggesting that all the protocols produced comparable levels of impairment in excitation-contraction coupling. These results suggest that, for brief stimulated contractions, peak force is a better predictor of fatigue than FTI, possibly because of the different metabolic demands of attaining and maintaining force.

Adult↗

PubMedDate not supplied

Total hip arthroplasty as an overnight-stay procedure using an ambulatory continuous psoas compartment nerve block: a prospective feasibility study.

OBJECTIVE: Total hip arthroplasty (THA) results in severe postoperative pain requiring hospitalization to provide potent analgesia. Consequently, the average duration of hospitalization after THA in the United States is 4 to 5 days. This prospective study investigated the feasibility of converting THA into an overnight-stay procedure using a continuous psoas compartment nerve block provided at home with a portable infusion pump. CASE REPORT: Preoperatively, patients undergoing THA had a psoas compartment perineural catheter placed. Postoperatively, perineural ropivacaine 0.2% was delivered through postoperative day (POD) 4. Patients were discharged home when they met specific, prospectively defined criteria, as early as POD 3 for the first phase and POD 1 for the second phase. Of the patients in the first phase (n = 7) who remained hospitalized for at least 3 postoperative nights, 5 met discharge criteria on POD 1 and the remainder on POD 2. Of the patients in phase 2 (n = 5), all but 1 met discharge criteria on POD 1 and 3 were discharged directly home on POD 1. Postoperative pain was well controlled, opioid requirements and sleep disturbances were minimal, and patient satisfaction high. CONCLUSIONS: These results suggest that for a subset of patients without major comorbidities, it is feasible to convert THA into an overnight-stay procedure using an ambulatory continuous psoas compartment nerve block as part of a multimodal analgesic regimen provided at home. Additional research is required to replicate these results in a controlled trial, define the appropriate subset of patients, and assess the incidence of complications associated with this practice before its mainstream use.

Aged↗

PubMedDate not supplied

Total elbow arthroplasty as an outpatient procedure using a continuous infraclavicular nerve block at home: a prospective case report.

OBJECTIVE: Total elbow arthroplasty (TEA) often results in severe postoperative pain requiring hospitalization to provide potent analgesia. This prospective series investigated the feasibility of converting TEA into an ambulatory procedure using a continuous infraclavicular nerve block provided at home with a portable infusion pump. CASE REPORT: Preoperatively, patients undergoing TEA had an infraclavicular perineural catheter and peripheral nerve block placed. Postoperatively, perineural ropivacaine was delivered through postoperative day (POD) 3 to 6. Patients were discharged home when they met specific, prospectively defined criteria as early as POD 1 for the first phase and directly from the recovery room for the second phase. Of the 2 patients in the first phase who remained hospitalized for at least 1 postoperative night, both met discharge criteria in the recovery room, required no medical interventions during their admission, and were discharged home the following morning. The patient of phase 2 met discharge criteria in the recovery room and was discharged home at that time. Postoperative pain was well controlled, opioid requirements and sleep disturbances were minimal, and patient satisfaction was high for all patients. CONCLUSIONS: These cases suggest that for a subset of patients without major comorbidities, it is feasible to convert total elbow arthroplasty into an ambulatory procedure using a continuous infraclavicular nerve block as part of a multimodal analgesic regimen provided at home. Additional research is required to replicate these results in a controlled trial, define the appropriate subset of patients, and assess the incidence of complications associated with this practice before its mainstream use.

Aged↗