David H. Lewis

Vasomotion in rat skeletal muscle induced by hemorrhage as recorded by laser Doppler flowmetry

Vasomotion in rat skeletal muscle induced by hemorrhage as recorded by laser Doppler flowmetry

Altered glutathione levels in ischemic and postischemic skeletal muscle : Difference between severe and moderate ischemic insult

The purpose of the present study was to investigate how the duration of ischemia and reperfusion affect the glutathione (GSH) levels in skeletal muscle and to assess the presence of oxidative stress by quantitating oxidized glutathione (GSSG) and the ratio of GSSG/GSH. The amounts of GSH and GSSG were quantitated in the tibialis anterior muscle of the rat hind limb after 2 and 4 hours of tourniquet ischemia and after 1 and 5 hours of reperfusion, and the levels were compared to those in nonischemic control tibialis anterior muscles. In muscles subjected to 2 hours of ischemia, the levels of GSH, GSSG, and the ratio GSSG/GSH did not differ significantly from those of nonischemic controls. After 4 hours of ischemia without reperfusion, the GSH levels were slightly increased, compared to controls (p < 0.05). After 1 hour of reperfusion following 4 hours of ischemia, the levels of GSH decreased by 50% compared to control (p < 0.01), and still after 5 hours of reperfusion the levels of GSH were 50% lower than control levels. The GSSG/ GSH ratio did not change during 1 and 5 hours of reperfusion compared to control. A major finding in this study was that, during reperfusion after severe ischemia of 4 hours, there was a marked depletion of glutathione, which was not seen after a moderate ischemic insult of 2 hours.

INFLUENCE OF PENTOBARBITAL, PROPOFOL AND KETAMINE ON SKELETAL MUSCLE CAPILLARY PERFUSION DURING HEMORRHAGE : A COMPARATIVE STUDY IN THE RABBIT

Anesthetics affect tissue blood flow, which is of importance especially in situations of inadequate perfusion, as in hemorrhage. The present study compared the effect of three commonly used anesthetic agents on skeletal muscle capillary and regional blood flow during and after recovery from hemorrhage. Three groups of rabbits were anesthetized randomly with either pentobarbital, propofol or ketamine, chosen such that the anesthetic level, blood pressure and withdrawn blood volume were comparable in all groups. Capillary blood flow was measured using a local hydrogen clearance technique with a multi-wire microelectrode, placed on the left vastus medialis muscle surface, and the contralateral site served for regional microcirculatory blood flow measurements using laser-Doppler flowmetry. Hemorrhage was induced by withdrawal of blood to a mean arterial pressure of 40 mm Hg and monitoring was continued during the subsequent spontaneous recovery period of 120 min. Both capillary and regional blood flow decreased significantly during hemorrhage in all groups. The flow values in the pentobarbital group were given a mean value of 100% and the other two groups were compared with this. Local hydrogen clearance flow decreased from a relative baseline level of 100 to 64% during hemorrhage with pentobarbital, from 87 to 43% with propofol and from 146 to 70% with ketamine. Laser-Doppler flowmetry flow decreased from relative baseline levels of 100, 96 and 139%, to 71, 77 and 103%, respectively, during hemorrhage, whereas the percentage of zero capillary flow values increased from 4 to 34, 19 to 50 and 5 to 27% in the three groups, respectively. The results of the present study indicate that capillary perfusion is best maintained in the ketamine group followed by pentobarbital and propofol last. Furthermore, the flow distribution shapes for each anesthetic indicate a more pronounced deregulation of capillary blood flow in the propofol group than in the others, even at baseline.

Exogenous Adenosine Induces Flowmotion in Skeletal Muscle Microcirculation of the Anesthetized Rat

The aim of this study was to investigate the characteristics of the microcirculatory blood flow with laser-Doppler flowmetry (LDF) in skeletal muscle during both regional and systemic infusions of adenosine. A laser-Doppler flowmeter probe was placed on the left gastrocnemius muscle in anesthetized rats. Adenosine was given either systemically in the jugular vein (group A) or administered regionally in the iliac artery (group B). The infusion of adenosine was increased stepwise by 50 micrograms/kg/min, every 10 min, up to 400 micrograms/kg/min. In group A there was a dose-dependent decrease in mean arterial pressure as well as in LDF flow; flowmotion of the LDF signal with a frequency of 1.6 cycles/min was seen at a mean adenosine dose of 240 micrograms/kg/min at a blood pressure of 60 mm Hg. In group B there was a dose-dependent decrease of mean arterial blood pressure but not as marked compared to group A, meanwhile the LDF flow was unchanged; flowmotion was seen at a mean adenosine dose of 220 microgram/kg/min at a blood pressure of 72 mm Hg, with a frequency of 1.5 cycles/min. This study demonstrates that adenosine, given either regionally intraarterially with maintained blood flow, or intravenously with reduced blood flow, induces flowmotion in skeletal muscle microcirculation with a frequency of approximately 1.5 cycles/min.

The immediate circulatory response to high-velocity missiles.

The immediate hemodynamic response to a high-velocity missile wound was studied in the hind legs of dogs. A spherical missile of constant mass and velocity was used. The immediate effect after the shot was a marked transient peak flow, which may be due to the effects of the pressure wave on the vascular bed, with a release of constrictor tone. The subsequent more constant increase of blood flow in the traumatized leg is of the same character as that seen following extensive soft-tissue contusion trauma. In addition to these local changes there was also a generalized effect with decreased blood pressure without a compensating increase in hear rate. This may be explained by the specific character of the trauma that a high-velocity missile produces.

A Comparison of Brain, Core and Skin Temperature in Children with Complicated and Uncomplicated Malaria

A prospective study was carried out in which brain, core and skin temperatures were studied in children with cerebral malaria (n = 23), uncomplicated malaria (n = 12) and normal children (n = 9) using the zero heat flow method. Patients with cerebral or uncomplicated malaria were admitted to the paediatric wards (mean age, 6 years 8 months +/- 2 years 8 months). Normal children, children of the investigators, of the same age group, served as controls. Parasitaemia levels were similar in the cerebral and uncomplicated malaria cases. Higher brain than core temperatures would have been expected in cerebral malaria but not in uncomplicated malaria but this was not the case in this study. There was no statistical difference in brain, core and skin temperature between cerebral and uncomplicated malaria patients. However, there was a highly significant difference between normal children and cerebral and uncomplicated malaria patients. Brain temperature was 0.02-0.2 degrees C below core temperature in all the groups with larger differences during the febrile period. Mean differences of brain minus core, brain minus skin and core minus skin between the two groups of patients were not statistically significant. There was no correlation between temperature and the level of coma or parasitaemia for cerebral and uncomplicated malaria patients. There was a positive correlation between brain and core temperature in both groups of patients during the febrile phase. Brain temperature remained lower than core temperature in cerebral and uncomplicated malaria as in normal children. Normal thermoregulation appears to be maintained in cerebral malaria.

Post-ischemic microcirculatory blood flow in skeletal muscle evaluated by laser-Doppler flowmetry

Abstract Laser-Doppler flowmetry (LDF) provides a continuous measurement of tissue microvascular blood flow in different pathophysiological situations. The aim of this study was to compare the perfusion signal (velocity multiplied by the concentration of moving red blood cells) and the CMBC signal (concentration of moving red blood cells) in the reperfusion phase after total ischemia of skeletal muscle. These parameters were recorded simultaneously with a laser-Doppler flowmeter (Periflux PF2b) in anesthetized rats. The flowmeter probe was placed on the left gastrocnemius muscle surface, which was made ischemic for various periods of time (10–180 min). In the control situation, prior to ischemia, the natural resting fluctuations of the perfusion and CMBC signals were parallel. Similarly, after release of ischemia there was an immediate and parallel increase in both the perfusion signal and the CMBC signal. The correlation coefficient between the perfusion signal and CMBC signal was found to be 0.78 ( P

Early changes in capillary flow and transport following missile wounds

Abstract The local hemodynamic response to missile wounds in soft tissue has been studied on 31 mongrel dogs with a double isotope clearance technique using sodium iodide (Na 131 I) and xenon ( 133 Xe). Three different impact velocities with a small spherical projectile were used to vary the amount of energy absorbed by the tissues. The isotope was injected at a constant depth but at varying distances from the wound site. The flow responses (i.e., xenon clearance) were quite variable, but there was a tendency toward greater responses between 35 and 45 mm from the wound channel after high-velocity missile wounds. The same tendency was seen more clearly for iodide clearance values. The size of the damage by missiles hitting with the three velocities used is discussed. Because of irregularities in the volume of tissue absorbing the energy, variations in individual animals could be expected. However, the flow pattern recorded with the isotope clearance technique coincides in both time and localization with the hemodynamic and angiographic findings after wounds caused in a similar way and reported previously.

A comparison of core and skin temperature among normal and febrile children with cerebral malaria, uncomplicated malaria, and measles

Abstract Forty-four children were studied to compare the pathogenesis of fever in cerebral malaria, uncomplicated malaria and measles at the Eldoret District Hospital (EDH). A control group of normal children was used. The three patient groups were studied for three consecutive days measuring skin and core temperature three-times a day using the Liquid Crystal Device (LCD) thermometer. A statistical analysis of the results within and between the groups was carried out for core and skin temperature over the study period. No statistical differences were found between the groups for either the skin or the core temperature, but a significant statistical difference was demonstrated between the core and the skin temperature for all of the groups for each of the three days. No statistical difference was found when the differences between the core and skin temperature were compared between cerebral malaria and uncomplicated malaria. The possible roles of fever in morbidity and mortality are discussed, with special reference to cerebral malaria.

The effect of trauma to the leg on the first-pass uptake of bacteria by the lung.

Our previous studies have shown that the first-pass pulmonary uptake of lidocaine and serotonin were not impaired by bullet wounding of the leg. Since there is decreased resistance to bacterial infection with trauma, it was of interest to study the uptake of bacteria. First-pass pulmonary uptake of 51-chromium-labeled, killed Salmonella typhimurium bacteria was studied in 26 pigs. In 16 controls, four injections at hourly intervals revealed an initial uptake of 84.5% +/- 1.5 (Mean +/- S.E.M.) and a 95% first-pass uptake of 78.6% +/- 2.4, and no significant change with time. In the ten traumatized animals only the values at 5 hours were significantly lower than the controls. It is concluded that repeated injections of killed Salmonella typhimurium bacteria without trauma do not interfere with the ability of the lung to remove these bacteria during their first passage through the lung, but that with trauma to the leg do to a slight degree.