Longitudinal neurophysiological assessment of intramuscular type-A botulin toxin in healthy humans.

The aim of this study is to assess the neurophysiological abnormalities of type A botulin toxin-infiltrated human muscle, and their evolution over time. Seried cMAP measurements, 3 and 20 Hz repetitive nerve stimulation, EMG, SFEMG over 3 months from toxin injection. Our findings consist in lack of decrement with 3 Hz repetitive nerve stimulation and facilitation with 20 Hz repetitive nerve stimulation; progressive increasing of jitter; early appearance of fibrillations; small and short motor unit action potential in the first 3 weeks, followed by increasing of MUAP amplitude and duration, with polyphasic morphology. Although claimed as highly specific and sensible, neuromuscular junction facilitation is an inconstant finding in human botulism. Therefore, lack of neuromuscular junction facilitation cannot exclude a diagnosis of botulism. Our findings are compatible with a process of acute denervation followed by distal reinnervation, favored by terminal nerve sprouting.

Clinical utilization of near-infrared spectroscopy devices for burn depth assessment.

The diagnosis of burn depth is based on a visual assessment and can be subjective. Near-infrared (NIR) spectroscopic devices were used preclinically with positive results. The purpose of this study was to test the devices in a clinical setting using easily identifiable burn wounds. Adult patients with acute superficial and full-thickness burns were enrolled. NIR point spectroscopy and imaging devices were used to collect hemodynamic data from the burn site and an adjacent unburned control site. Oxy-hemoglobin and deoxy-hemoglobin concentrations were extracted from spectroscopic data and reported as oxygen saturation and total hemoglobin. Sixteen patients (n=16) were included in the study with equal numbers in both burn wound groups. Point spectroscopy data showed an increase in oxygen saturation (p<0.0095) and total hemoglobin (<0.0001) in comparison with the respective control areas for superficial burn wounds. The opposite was true for full-thickness burns, which showed a decrease in oxygenation (p<0.0001) and total hemoglobin (p<0.0147) in comparison with control areas. NIR imaging technology provides an estimate of hemodynamic parameters and could easily distinguish superficial and full-thickness burn wounds. These results confirm that NIR devices can successfully distinguish superficial and full-thickness burn injuries.

Near infrared spectroscopic assessment of hemodynamic changes in the early post-burn period.

Near infrared reflectance spectroscopy and imaging was used to assess non-invasively the hemodynamic changes that occur in the early post-burn period in cutaneous burn injuries of varying depth. An acute porcine model was used to demonstrate the potential of near infrared spectroscopy and imaging to accurately determine the change in tissue oxygenation, blood volume and tissue water content following a thermal injury. Near infrared spectroscopy was used to monitor tissue at discrete locations, while spectroscopic imaging was able to survey large areas of tissue. Both methods were rapid and non-invasive. Tissue hemoglobin oxygen saturation, total hemoglobin and tissue water content were all affected by thermal injury and changed significantly over a 3 h post-burn monitoring period. Burns that ranged in severity between superficial and full thickness displayed a significantly different hemodynamic response. When the early post-burn profiles (1-3 h) of tissue hemoglobin oxygen saturation, total hemoglobin and tissue water content were considered jointly, injuries leading to superficial, intermediate partial thickness, deep partial thickness and full thickness burns could all be differentiated at high statistical significance. These results suggest that non-invasive hemodynamic monitoring in the early post-burn period using near infrared spectroscopy may be of value in the early assessment of burn injury.

Esophageal electrodes allow precise assessment of cardiac output by bioimpedance.

OBJECTIVES: To analyze the impact of the position of the thoracic external electrodes on the values of cardiac output measured by electrical bioimpedance and to compare the results obtained by bioimpedance with those values determined by thermodilution in critically ill patients. DESIGN: Open, prospective, comparative trial. SETTING: ICU of a teaching hospital. PATIENTS: Twenty healthy volunteers and ten critically ill patients. INTERVENTIONS: Measurements of cardiac output by bioimpedance at rest and after physical activity in normal volunteers and after changing the neck or xiphoid electrodes. Comparisons of cardiac output obtained by thermodilution and bioimpedance with internal and external electrodes in patients. MEASUREMENTS AND MAIN RESULTS: Mean +/- SD values are presented. Cardiac output values at rest and after exercise were 6.7 +/- 1.3 and 10.8 +/- 2.6 L/min at rest and after exercise, respectively (p less than .001). Displacement of the xiphoid electrodes 3 cm in the caudal direction was accompanied by a decrease of the mean cardiac output from 7.1 +/- 1.2 to 5.8 +/- 1.3 L/min (p less than .001) and displacement 3 and 6 cm cranially was accompanied by increases in cardiac output from 7.1 +/- 1.2 to 8.1 +/- 1.4 L/min (p less than .001) and 8.6 +/- 1.5 L/min (p less than .001), respectively. In the ten patients, cardiac output measurements were virtually identical when results obtained by thermodilution (6.7 +/- 3.1 L/min) were compared with those results obtained by bioimpedance using internal esophageal (6.6 +/- 3.1 L/min), but not external (4.7 +/- 1.6 L/min) electrodes. CONCLUSIONS: a) The values of cardiac output derived from measurements obtained by bioimpedance using internal electrodes were comparable with those values derived from thermodilution. b) Values of cardiac output from bioimpedance studies with external electrodes were dependent on the position of the xiphoid electrodes.