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Biomedical subjects

R C Kester

Publications and source records attributed to R C Kester.

At least 73 records · Page 4Linked to original sources
PubMed1991

Altered sensitivity of digital blood flow to acute vibration in patients with vasospastic disease.

Fifteen patients with primary Raynaud's, 18 patients with vibration induced white finger (VWF) and 15 controls were exposed to sine wave vibration, with an amplitude of 0.15 mm and frequencies of 40, 80 and 120 Hz. Baseline digital blood flow was measured using venous occlusion strain gauge plethysmography. A digit was vibrated for 1 min and subsequent blood flow measurements were taken from both vibrated and non-vibrated digits. Vibration at 40 Hz causes a significant decrease in flow in the vibrated digits of the control group only (P less than 0.05, Wilcoxon test). Vibration at 80 Hz shows a significant decrease in blood flow in the vibrated digits of both the control and the VWF groups (P less than 0.005) and also in the non-vibrated digits of the VWF group (P less than 0.05). Vibration at 120 Hz significantly decreases blood flow in the vibrated digits of normal control, VWF and Raynauds group (P less than 0.001). The Raynaud's non-vibrated digits also had decreased flow (P less than 0.005). These results imply that patients with established vasospastic disease are less sensitive to the direct effects of acute vibration than controls. The results also imply that vibration at 40, 80 and 120Hz affect digital blood flow in controls through local mechanism. Vibration at certain frequencies, appears to modulate blood flow in patients with vasospastic disease by acting through central mechanisms.

Adult↗
PubMed1991

Radionuclide limb blood flow in peripheral vascular disease: a review of 1100 measurements.

Radionuclide limb blood flow measurements using 99Tcm-labelled human serum albumin and a gamma camera have been performed on normal volunteers and on patients with suspected or confirmed peripheral arterial disease. The normal range of flow was found to be 10.0-22.3 ml per 100 ml tissue per min. Flow in the symptomatic legs of patients with arterial disease varied from 9.0 ml per 100 ml tissue per min in mild claudication to less than 1.0 ml per 100 ml tissue per min in rest pain. The technique has been used as an initial screening procedure, to resolve diagnostic problems, to measure objectively the treatment response and to assess patients with critical ischaemia. The results of 1100 measurements are reported and the clinical utility in routine vascular surgical practice is discussed.

Adult↗
PubMed1990

Thermal characteristics of sapphire contact probe delivery systems for laser angioplasty.

Contact probes made from synthetic sapphire crystal, designed for general laser surgery, are currently being evaluated for use in laser angioplasty. Their mode of action and safety in the context of arterial recanalisation is unknown, particularly with respect to the degree of probe and catheter heating. Infrared thermal imaging was used to investigate the surface temperature rise of various rounded sapphire probes during emission of continuous wave Nd-YAG (1,064 nm) laser energy. Catheter safety was addressed by analyzing the temperature of the metal interface between the optical fiber and sapphire, as well as the catheter proximal to this junction. Transmission of Nd-YAG energy through each probe was also measured. Five rounded probes of 1.8-3.0 mm diameter (three supplied by Surgical Laser Technologies [SLT], two by Living Technology [LT]), along with their respective optical catheters, were compared. There was a large temperature gradient between the front and rim of the probes. The maximum surface temperature rise of the sapphire (at 20 W, 5-second exposure) was 314-339 degrees C (SLT) and 90-108 degrees C (LT) [P less than 0.001, 3-way ANOVA]. The reason for this difference may be related to "crazing" of the front surface of the SLT sapphires. At all energy levels sapphire temperatures were considerably lower than attained by metal laser thermal angioplasty probes. Forward transmission was slightly higher in the SLT probes (75-85%) than the LT sapphires (54-69%). With fiber perfusion at 2 ml/minute, a minor degree of heating of the metal sapphire holders was recorded (maximum rise 35 degrees C), but heating of the catheter proximal to this was negligible. Therefore, it would appear that the risk of tip detachment or arterial injury due to heating of the connecting metal interface is extremely low. Without perfusion, however, there was a greater degree of interface heating in the LT delivery system suggestive of more laser backscattering by these sapphires compared with the SLT probes [P less than 0.001, one-way ANOVA]. The SLT system is, therefore, potentially safer in this respect. These results suggest that some degree of surface heating of contact probes due to energy absorption within the sapphire does occur, but is localised to the front of the probe. This effect may contribute to the process of arterial recanalisation with this device. However, variation in the thermal and optical properties of sapphires from different sources has been demonstrated. The influence of these properties on plaque ablation, and ultimately the clinical performance of different contact probe systems, requires further investigation.

Humans↗
PubMed1990

Aneurysm formation after dynamic catheter assisted balloon angioplasty.

A male patient underwent recanalisation of a symptomatic popliteal artery occlusion using a dynamic angioplasty catheter, followed by balloon dilatation. A small subintimal dissection lead to an acute reocclusion. Repeat balloon angioplasty reopened the occlusion but was complicated by a distal embolus which was successfully treated by thrombolytic therapy followed by oral anticoagulation. Angiography 9 months later, demonstrated an aneurysm at the site of initial dissection. The artery remained patent and the patient free of claudication. A causal relationship between dynamic angioplasty and subsequent aneurysm formation is suggested and the possible predisposing factors discussed.

Aneurysm↗
PubMed1990

Dual tracer technique to measure salvaged red cell survival following autotransfusion in aortic surgery.

The survival of autotransfused red cells was measured for two salvage devices used in 12 elective aortic reconstructions. Six patients underwent cell salvage with the Solco-trans device and six with the Haemonetics cell saver. A double tracer technique was used to take account of post-operative blood loss and fluid replacement. Comparison was made with the results of a group of normal volunteers. A comparison was made of the labelling efficiency of damaged and undamaged red cells using chromium to check that red cells damaged during autotransfusion can be labelled. No significant difference was seen. There was no significant difference in red cell survival between the volunteer group and either of the two salvage device groups. These results suggest that red cell survival is not compromised by the autotransfusion process using these two devices.

Aortic Diseases↗
PubMed1990

Experimental analysis of sapphire contact probes for Nd-YAG laser angioplasty.

Laser angioplasty may offer percutaneous recanalization of occluded vessels where conventional guidewire and balloon techniques fail. Metal laser thermal angioplasty probes may, however, cause excessive thermal damage due to high tip temperatures (greater than 400.C). Therefore, contact probes made from artificial sapphire crystal designed for general laser surgery are currently being evaluated for use in laser angioplasty with continuous wave Nd-YAG energy. The sapphire modifies the laser energy in various ways, and this paper examines the physical characteristics of five types of rounded sapphire probe (SMTR, MTR, MTRL, OS, LT) and how these properties are affected by clinical usage. The laser beam profile emitted by these probes demonstrates a focal spot 1-2 mm in front of the tip. However, the forward transmission of Nd-YAG energy through the sapphires varied (SMTR, 85%; MTR, 83%; MTRL, 75%; OS, 54%; LT, 69%). Probe heating occurs owing to energy absorption within the sapphire. The surface temperature of the sapphires was measured in air by infrared thermography and the hottest region within the probes localized by an isothermographic technique. At energy settings used clinically (20 J, 10 watts for 2 s) the SMTR, MTR, and MTRL probes exhibited higher temperature rises (94-112.C) than the OS and LT probes (30.C), and heating was localized to the front surface of the former probes. Peak sapphire temperatures remained lower than those of metal probes even at higher energies. After clinical use, the MTR probe demonstrated reduced transmission, beam defocusing, and increased heating, due to surface pitting. Thus, recanalization with sapphire probes occurs by a combination of photothermal and contact thermal effects that are localized to the probe tip and may reduce the degree of thermal injury associated with metal probes. Understanding these basic properties is important to the application and development of contact probes for laser recanalization.

Aluminum↗
PubMed1990

The application of isotope limb blood flow measurement to diagnostic problems in vascular surgery.

A new method of limb blood flow measurement has been developed; normal flow is 10-22 ml/100 ml of tissue/min and flow to limbs with claudication is 1.8-2.3. Does this technique help to deal with diagnostic problems in vascular surgery? Twenty-five patients presented with exercise-induced leg pain. Twelve had a convincing history of claudication but seven of these had palpable pedal pulses, the other five had normal Doppler ratios. Of 13 with a poor history six had absent pulses; of the other seven with palpable pulses, two had abnormal and five had normal Doppler ratios. All 25 patients have had blood flow to both legs measured. For the five with a poor history, palpable pulses and normal Doppler ratios: (Table: see text). Twelve had reduced flows consistent with claudication (less than 8 ml/100 ml of tissue/min); 10 of these have undergone arteriography which demonstrated significant vascular disease, one had surgery to rheumatoid toes deferred and one refused further investigation. Of 13 with normal flows nine have been found to have significant orthopaedic problems affecting spine, hips or knees, the other four have all had normal arteriograms. In every case the history, signs or Doppler ratios were potentially misleading, but all cases of significant arterial disease were detected. It is cheap, readily available and effectively selected cases for referral or arteriography.

Gamma Cameras↗
PubMed1989

Plasma eicosanoids, platelet function and cold sensitivity.

As abnormal eicosanoid (prostaglandin) metabolism has been suggested as a factor in the aetiology of vasospastic diseases we have measured levels of stable eicosanoid metabolites using a radioimmunoassay in 30 normal subjects and 31 patients with Raynaud's phenomenon. There were 13 patients with primary Raynaud's, ten with Raynaud's secondary to scleroderma and eight men with vibration white finger (VWF) disease. We have also measured platelet aggregation to adenosine diphosphate (ADP), collagen and adrenaline in 19 normal subjects, 22 patients with primary Raynaud's, 12 with Raynaud's secondary to scleroderma and 14 men with VWF. When compared with our normal subjects, patients with VWF have an elevated thromboxane B2 level, with a normal 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) level. Their platelets are less sensitive to ADP and collagen. Patients with primary and secondary Raynaud's have elevated thromboxane B2 levels but this is much more marked in the secondary group. Patients with primary Raynaud's have a normal 6-keto-PGF1 alpha level but in patients with secondary Raynaud's the 6-keto-PGF1 alpha level is markedly raised. The platelets from both groups are more sensitive to ADP and collagen and this is more marked in the secondary group. Whether these phenomena are a cause or an effect of vasospasm remains unknown.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Effect of preclotting on the porosity and thrombogenicity of knitted Dacron grafts.

The effects of single- and four-stage preclotting methods on graft porosity and thrombogenicity were compared in two types of Dacron prosthesis. The single-stage method significantly reduced leakage of blood (P less than 0.001), but did not seal the grafts. The four-stage method rendered the grafts impermeable at the second step. Thrombogenicity was compared by perfusing preclotted grafts with fresh heparinized blood (containing 111In-labelled platelets) in an artificial circulation. Platelet deposition and consumption were significantly less in the four-stage method whilst platelet function remained unchanged during perfusion. We conclude that the four-stage technique is superior to standard preclotting methods by rendering knitted Dacron grafts impermeable and hypothrombogenic.

Blood Coagulation↗
PubMed1989

Foot strike and the properties of the human heel pad.

Many force-plate records of human locomotion show an impulse (the foot strike) shortly after ground contact. The authors' hypothesis is that this results from the rapid deceleration of a mass (the 'effective foot') under forces which compress the heel pad. The quantitative implications are investigated through an illustrative calculation. The observations used are (a) the peak force reached in foot strike (b) the vertical velocity of the foot immediately before ground contact and (c) the properties of the heel pad in compression. Data for (a) and (b) are available in the literature; measurements for (c) are presented here. The deductions are: (a) the time taken to reach peak force is about 5.4 ms, which agrees with published measurements; (b) the mass of the effective foot is about 3.6 kg. The effective foot thus includes a substantial portion of the leg: this seems reasonable. The models used for the calculations clarify the relationship between the foot strike and the shock wave, which it generates.

Biomechanical Phenomena↗
PubMed1989

Teicoplanin: Part 1. An evaluation of the concentrations seen in serum and the subcutaneous fat of the relatively ischaemic lower limb following a single intravenous bolus.

Teicoplanin is a new antibiotic currently undergoing clinical evaluation. Consecutive patients undergoing elective vascular surgery (n = 28) were randomised to receive a single intravenous bolus of 400 mg teicoplanin 1, 3, 6 or 12 h prior to surgery as prophylaxis against Gram-positive infection. Serum and fat antibiotic levels were measured and found to exceed the established MICs for common staphylococcal and streptococcal infections for at least 12 h following administration. This suggests that teicoplanin would be a useful choice of antibiotic in the prophylaxis and treatment of appropriate infections in elective surgery. By extrapolation, teicoplanin would also be of use in the prophylaxis and treatment of suitable infections seen in traumatised patients.

Adipose Tissue↗
PubMed1989

Teicoplanin: Part 2. Evaluation of its use in the biliary system.

Teicoplanin is a new antibiotic currently undergoing extensive investigation to evaluate its potential use in the prophylaxis and treatment of appropriate infection. To ascertain its penetration into the biliary system, 24 patients undergoing elective cholecystectomy were randomised to receive an intravenous bolus of 400 mg teicoplanin 1, 3, 6 or 12 h prior to surgery. During the operation, blood, gall bladder bile and tissue and common bile duct bile were removed for teicoplanin estimation. The results show that teicoplanin penetrates well into the gall bladder wall and bile, though less well into common bile duct bile. These results show that teicoplanin would seem to be a suitable antibiotic for the treatment of biliary infections that are known to be sensitive to the antibiotic.

Anti-Bacterial Agents↗
PubMed1989

Controlled trial of cephradine versus cefuroxime in vascular surgery.

Two hundred and three consecutive patients undergoing acute or elective vascular reconstructions (N = 162) or amputations (N = 41) were randomized to receive either a single dose of cephradine 2 g intravenously or cefuroxime 1.5 g intravenously at induction of anaesthesia. Infective morbidity in both groups was assessed post-operatively as was therapeutic antibiotic prescribing. No significant differences in septic complications were found between patients receiving cefuroxime or cephradine. In addition, tissue penetration of each antibiotic was assessed by assay of serum and tissue specimens. Serum levels of cefuroxime were significantly less than cephradine 10 min after injection (median concentrations 115 micrograms/ml versus 182 micrograms/ml, p less than 0.01 Wilcoxon), but there were no differences in tissue penetration.

Amputation, Surgical↗