Biomedical subjects
Publications and source records attributed to D H Lewis.
A method of external cranio-maxillary fixation using orthodontic appliances is described, which is particularly suitable for surgical cases where additional vertical stability is required.
The purpose of the present study was to compare fluorescein flowmetry as a technique for measuring changes in intestine blood flow with electromagnetic blood flowmetry and the 133Xenon clearance technique. In eight anaesthetized pigs the blood flow in the superior mesenteric artery was reduced to 20-75% of basal flow as defined by electromagnetic flowmetry. The change in blood flow as calculated by fluorescein flowmetry correlated well with that obtained by electromagnetic blood flowmetry (correlation coefficient 0.86) and 133Xenon clearance technique (correlation coefficient 0.94). These findings indicate that fluorescein flowmetry can be considered a quantitative method for measurements of a relative blood flow.
In the assessment of viability of traumatized muscle tissue clinical signs, including colour, consistency, capillary bleeding and contractility have been commonly used. One of these signs, discolouration, has been shown in earlier studies to be associated with impaired circulation and severe and irreversible changes of muscle electrolytes and energy metabolism. In this study the circulation and tissue oxygen pressure fields were studied on either side of the "demarcation line" between discoloured and normally coloured areas of traumatized muscle tissue. Anaesthetized pigs were injured in one thigh with a high velocity spherical steel missile. The microcirculatory flow of the traumatized muscle was studied by measuring the clearance of 133Xenon from the surface of the muscle and tissue oxygen pressure (PtO2) was measured with an MDO electrode. Measurements were done before and 1, 3 and 5 hours after the trauma. A markedly decreased or absent flow as well as very low PtO2 values were found within areas of discolouration. In the adjacent normally coloured areas no such changes were noted and the values of these areas resembled those of the contralateral untraumatized leg. The results agree with those of earlier studies of circulation and metabolic changes indicating that discolouration is a useful sign in the clinical assessment of muscle viability after high-energy trauma.
A method for measuring regional cerebral blood flow with local application of 133Xenon was used. A polyester film was placed on pig cerebral cortex under which 0.6-1.3 mCi of 133Xenon dissolved in 2-4 microliter of saline was applied atraumatically. The wash-out process was registered with an external detector. The wash-out curves were not contaminated by extra-cerebral tissue and there was no 'looking-through phenomenon' of non-perfused parts of the brain. Regional cerebral blood flow was 142 +/- 14 ml X 100 g-1 X min-1 (mean +/- S.D.) in grey matter and 34 +/- 9 ml X 100 g-1 X min-1 in white matter when PaCO2 was normal (4.92 +/- 0.43 kPa). When PaCO2 was increased to 9.3 +/- 1.39 kPa regional cerebral blood flow was increased to 313 +/- 60 ml X 100 g-1 X min-1 in grey matter and to 46 +/- 20 ml X 100g-1 X min-1 in white matter.
In order to evaluate methods to prevent pressure sores the effect of massage on the local skin blood flow was studied in normal skin and in skin with discolouration (red or reddish blue). In this study massage is defined as small circular movements with the fingertips using liniment. The cutaneous blood flow was measured with a laser Doppler flowmeter. To study the long term effect of massage on normal skin ten patients were measured over a twenty day period with five days before and after a ten day period with massage. Twenty-nine patients with cerebral haemorrhage were measured for two days each to examine the effect immediately after the massage on normal skin. Fifteen patients with discolouration were measured for one day each both on normal skin and injured skin. The difference in blood flow before and after the ten day period of massage was inconsistent and insignificant. The effect of massage which appeared one to two minutes after the stimulus was implemented varies between individuals and within individuals; significantly more women than men increased their skin blood flow bilaterally after massage. In the centre of the injured skin the basal blood flow was higher than in normal skin and it decreased after the massage was implemented. The results stress the importance of continued research to provide an opportunity for individualization in the selection of methods to prevent and treat pressure sores.
The area between ischemic and normal myocardium after acute coronary occlusion-the border zone-is of great interest. It has been proposed that this area contains reversibly damaged myocardium subjectable to myocardial salvage. Twenty Swedish land race pigs were studied, 13 after acute occlusion of the left anterior descending coronary artery (LAD), while seven served as controls. We measured tissue oxygen pressures (ptO2) subepicardially with the MDO electrode. This is a multiwire surface electrode measuring ptO2 with eight individual platinum wires. Hundred and twenty values were collected in each measuring situation. The electrode was positioned on the lateral border zone, measurements were performed before and 5, 30 and 120 min after LAD occlusion. In five cases successful measurements were performed across the border zone. A mixture of normal and ischemic ptO2 values was found 5 min after occlusion. After 30 min of occlusion the number of ischemic values decreased and this was particularly the case after two hours of occlusion. The results support the view that the border zone was very narrow. The reduced number of ischemic values after two hours of permanent LAD occlusion also indicated that the border zone may be narrow but not necessarily fixed but instead dynamic. In this case there was a spontaneous decrease of the ischemic area.
Explore the source record for details and available documents.
The performance in vivo of nafarelin acetate, a potent analogue of luteinizing hormone-releasing hormone, microencapsulated in poly(d,l-lactide-co-glycolide), was evaluated. The influence of polymer composition and molecular weight on the estrus-suppressing activity of the microspheres in female rats was determined. Compound release was shown to be effected by polymer erosion rather than by diffusion. A triphasic release of compound was observed, which was adjusted by altering the critical parameters of the polymer. A mechanism for the release of the compound was proposed. The primary release phase was compound loss by diffusion from the surface of the microspheres. The secondary phase of subeffective rates of release occurred concomitantly with polymer hydrolysis and a decrease in its molecular weight, although it remained insoluble. Dissolution of low-molecular weight fragments and erosion of the bulk of the polymer then initiated the tertiary phase of release of compound.
A case report is presented of an orthodontic patient who suffered internal resorption and a consequent 'pink spot' affecting a maxillary central incisor. Its management is outlined. The aetiology and possible cellular events responsible are discussed.
The aim of this study was to measure skin blood flow in patients with pressure sore in a long-term care unit. For comparison, measurements were also carried out on in-patients at risk of developing pressure sores and on healthy individuals in the same age groups as the in-patients. Skin blood flow was measured in the morning, using a laser-Doppler flowmeter. Measurements were made over the lateral part of the hip and over the lateral part of the upper arm. Measurements were carried out first at ambient temperature. The flow was then followed as the local skin region was heated to 40 degrees C. The results indicate that in healthy individuals the heat stimulus increased skin blood flow over the lateral part of the hip more than in in-patients in the same age group. Individuals below the age of 60 have a greater response than those over the age of 60. This impairment in the ability of the older in-patients to increase skin blood flow in response to thermal stimulus may be a factor in the development of pressure sores.
Blood flow in cancellous bone with varying vascular density was investigated simultaneously with Laser Doppler Flowmetry (LDF) and 133Xe-clearance. The cancellous bone subapical to 2 contralateral incisors in the mandibles of 17 young pigs was used as an experimental model. Light from a 2 mW He-Ne-laser was guided through an optical fibre to a flowmeter probe. Stainless steel probe-holders firmly inserted in the pulpal canals of the two incisors served as the probe entrance to cancellous bone for blood flow recording. Due to the Doppler effect, the light scattered by circulating blood cells undergoes a frequency shift. The back-scattered light picked up by optical fibres in the probe, was guided to a photosensitive device, where it was demodulated. After signal processing, a signal referred to as the Blood Flow Value (BFV) was recorded on a pen recorder. Rhythmical variations (vasomotion) in BFV with frequencies from 2-11 cycles/min were observed in 6% of recordings made initially after probe-holder implantation, and in 34% of the recordings made 5 weeks later. On this occasion, a marked increase in BFV was recorded. Histological examination showed increased vascularity in the bone tissue. The reproducibility error of LDF was 7.4% and temporal changes in BFV, apart from vasomotion, were 8.3%, provided no injections or manipulations of the probe were made. Spatial variations in BFV were found to be related to the vascular density. 2 successive recordings by LDF from the same bone area were highly correlated (r = 0.98). The corresponding figure for 2 logarithmic decay rates of locally injected 133Xe was 0.76. No correlation between BFV and 133Xe-clearance could be demonstrated.
Microcapsules made from a biocompatible, biodegradable polymeric excipient, poly(DL-lactide-co-glycolide) (DL-PLGA) that contained 22 weight percent (wt %) norethisterone (NET), were prepared by a solvent-evaporation microencapsulation process. The effects of changing both the lactide-to-glycolide ratio of the DL-PLGA and the size of the microcapsules on the rate of NET release and the rate of excipient biodegradation were determined in vivo. NET release rates were determined in baboons after injecting the microcapsule formulations intramuscularly. Serum samples obtained at various times following treatment were analyzed for NET, progesterone, and estrogen by radioimmunoassay (RIA). Biodegradation kinetics were determined by injecting NET microcapsules made from radiolabeled DL-PLGA intramuscularly into the hind legs of rats. Residual radioactivity at the injection site was determined at various times after treatment by combustion analysis of the muscle tissue. Changing the ratio of the comonomers to include more glycolide (DL-lactide:glycolide-96:4, 92:8, 87:13, 74:26) increased the rate of NET release and accelerated the biodegradation of the copolymer excipient. Decreasing the size of the microcapsules increased the rate of NET release. On the basis of these studies a NET microcapsule formulation has been identified for clinical testing which releases NET for 3 months and biodegrades completely within 6 months.
Pulmonary uptake of lidocaine was investigated in patients before surgery, and aimed at elucidating the influence of general anaesthesia, the presence of another local anaesthetic agent in the blood, or the possible impact of lung insufficiency. When the lung uptake of lidocaine, injected as a bolus together with indocyanine green dye, was calculated as uptake at 95% pass of the dye, there were no statistically significant differences between the four groups. When the extraction in each of the arterial blood samples was calculated on the basis of the relation between relative concentrations, there were statistically significant differences, with a general tendency towards higher extraction of lidocaine in the awake, healthy volunteers, not given mepivacaine, compared to the other groups. In the group in whom mepivacaine was infused, the arterial concentration of mepivacaine increased transiently after the injection of lidocaine. This probably reflects a displacement of mepivacaine from binding sites for both agents. From this study, it is postulated that the ability of the pulmonary circulation to clear the blood of lidocaine is high, and that it is not affected markedly by those situations studied in the present investigation.
The regional blood flow in skeletal muscle after high-energy trauma was studied. The thigh musculature of anesthetized pigs was wounded with a high-velocity missile. The blood flow was measured with a technique using radioactive microspheres and also with a new laser Doppler flowmeter. Both methods showed very little flow in the discolored, traumatized muscle tissue nearest the missile track, whereas normal flow was found in more distal, normally colored muscle. There was good correlation between the results with the two methods. The laser Doppler flowmeter was shown to be a noninvasive technique permitting flow recordings in small areas of tissue surface. The restriction of flow impairment to the discolored areas of the traumatized muscle implies that discoloration is a useful clinical guide during debridement of traumatized muscle.
Changes in energy metabolism in skeletal muscle tissue after high-energy trauma were studied. Trauma was inflicted to the thigh of anaesthetized pigs with a high-velocity missile. The changes in contents of adenine nucleotides, phosphoryl creatine, creatine, lactate and glycogen were studied within areas of discoloured muscle tissue nearest the wound and were compared with corresponding values in adjacent normally coloured muscle. Severe and presumably irreversible changes in energy metabolism were found in discoloured muscle, with depletion of ATP and phosphoryl creatine and marked increase in lactate levels. No such changes were found in the normally coloured tissue. The progression of the changes during a 10-hour observation period and the magnitude of the metabolic disturbance indicate that such discoloured muscle tissue must be regarded as non-viable. Discolouration can therefore be regarded as a useful clinical sign during debridement of traumatized muscle tissue.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.