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Biomedical subjects

M H Thomas

Publications and source records attributed to M H Thomas.

At least 19 recordsLinked to original sources
PubMed1991

Light reflection rheography: an effective non-invasive technique for screening patients with suspected deep venous thrombosis.

Light reflection rheography is a simple non-invasive technique for assessing venous function in the leg. One hundred and twenty-four patients referred for venography with a clinically suspected deep venous thrombosis were investigated by light reflection rheography to determine the accuracy of the technique in diagnosing acute thrombosis. In half of the patients venography confirmed a deep venous thrombosis. Light reflection rheography had a sensitivity of 92 per cent and a specificity of 84 per cent in detecting acute thrombosis. The technique had a negative predictive value of 92 per cent in selecting those patients with no thrombosis. Light reflection rheography can be performed at the bedside or in the radiography department which makes it a suitable technique for screening patients with suspected deep venous thrombosis.

Female↗
PubMed1991

Retrograde femoral angioplasty: a new technique.

Percutaneous transluminal angioplasty cannot be used for lesions of the superficial femoral artery when the origin of the vessel is occluded. A new technique, retrograde femoral angioplasty, is described in which angioplasty is performed from below via the exposed popliteal artery. In four out of six patients retrograde femoral angioplasty was successfully completed, and three of the four vessels remain patent up to 1 year later. The method provides an alternative to the femoropopliteal bypass graft in some patients.

Angioplasty, Balloon↗
PubMed1991

Confirmation of oxytetracycline, tetracycline and chlortetracycline residues in milk by particle beam liquid chromatography/mass spectrometry.

A method using particle beam liquid chromatography/mass spectrometry was developed for the confirmation of oxytetracycline, tetracycline and chlortetracycline residues in bovine milk. This method is one of the first to apply particle beam technology to the confirmation of animal drug residues in food products for regulatory purposes. The milk is centrifuged, using molecular weight cut-off filters to remove components of 25,000 daltons and above from the milk. The filtrate is passed through a C-18 sample preparation cartridge which retains the tetracyclines. After the columns are washed with water, the tetracyclines are eluted with 0.1 M oxalic acid in methanol and concentrated. The compounds are separated on a Novapak C-18 column with a methanol-oxalic acid-acetonitrile mobile phase. Negative chemical ionization with selective ion monitoring is used to identify the tetracyclines. The procedure was used to confirm the presence of each tetracycline at 100 ng ml-1 in fortified and incurred milk samples.

Animals↗
PubMed1991

Cardiac sympathetic tone in anaesthetized diabetics.

To assess cardiac sympathetic nervous function in diabetics, the heart rates attained following a pharmacological dose of intravenous atropine, 23 micrograms.kg-1, were studied under N2O, isoflurane anaesthesia in diabetics (n = 21) and nondiabetics (n = 30). Atropine-induced heart rate in diabetics was significantly lower than that in nondiabetics (95 +/- 14 (SD) bpm vs 109 +/- 12 bpm, P less than 0.001) and were closely related to preoperative orthostatic diastolic blood pressure change (r = 0.60, P less than 0.01). There was some correlation between the atropine-induced heart rate and preoperative RR-variation in diabetics (r = 0.50, P less than 0.05). The findings suggest that cardiac sympathetic function may also be impaired in diabetics with orthostatic hypotension.

Adolescent↗
PubMed1991

Small bowel function after aortic surgery.

One cause of post-operative morbidity in the elective repair of abdominal aortic aneurysms is the development of a paralytic or 'adynamic' ileus. In a series of 20 consecutive patients undergoing such a procedure, the maintenance of small bowel motility and absorptive capacity in the immediate post-operative period was assessed using barium sulphate and xylose passed down a naso-duodenal tube sited at the time of surgery. This simple study demonstrated that small bowel function was preserved in all cases, and hence that patients could be fed enterally via naso-duodenal tube (in particular using very low residue formulae) rather than using costly parenteral regimens, should an ileus persist.

Aorta, Abdominal↗
PubMed1990

Self protection in surgery: the use of double gloves.

This study assesses the perforation rate of single and double gloves and thus the extent to which double gloving protects the surgeon from diseases transmissible from the patient. We have also investigated whether double gloving offers the patient extra protection by reducing wound sepsis. Two hundred adult hernia repairs were performed, the first 100 single gloved and the second 100 double gloved. Glove perforation rates were not significantly different between single gloves and the outer of the double gloves. Although 46 of 400 outer gloves were perforated there were only 15 inner glove perforations and only eight of these matched the outer perforations. The percentage of operations in which the latex protective barrier was breached was reduced from 31 per cent when the surgeon wore single gloves to 8 per cent with double gloves. Wound sepsis was not increased by glove perforation nor reduced by double gloving. While careful technique remains mandatory we conclude that double gloving offers increased protection to the surgeon operating on high risk infectious cases.

General Surgery↗
PubMed1990

Pseudomembranous colitis after abdominal aortic aneurysm repair.

We report three patients who developed pseudomembranous colitis following aortic aneurysm resection. Colonic ischaemia can occur after such surgery and ischaemic colonic mucosa is known to be more susceptible to damage by bacteria and their toxins. This colonic ischaemia together with the antibiotic prophylaxis used may render aortic aneurysm patients susceptible to pseudomembranous colitis. It is important to distinguish pseudomembranous from ischaemic colitis in these patients as specific and effective drug therapy can be given to those with the pseudomembranous type.

Aged↗
PubMed1990

Stroke volume measurements by electrical bioimpedance and echocardiography in healthy volunteers.

To evaluate the validity of three equations for estimation of thoracic electrical field size in a new bioimpedance algorithm, stroke volume (SV) as calculated by these equations was compared with that calculated by Doppler echocardiography in 48 healthy volunteers, both lean and obese. When the volume of electrically participating tissue was estimated from body height (modified Sramek) or body height corrected for body habitus (Sramek-Bernstein), there was considerable variation between bioimpedance and Doppler stroke volumes. When the volume of electrically participating tissue was estimated from the actual measurement of the height of the thorax and the circumference at the base of the thorax, the variation in SV differences decreased substantially (Sramek equation), although still considerable for clinical use, and there was no relationship between SV thus obtained and body habitus. Analysis of calculated stroke indices derived by our Doppler echocardiographic standard, as compared with values in the literature, revealed a systematic underestimation. We conclude that the original Sramek equation systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically overestimate SV in females by about 15%, but provide SV values in males in the predicted range. Further studies on the current assumption that the electrical field size is a truncated cone may improve precision of the bioimpedance method.

Adult↗
PubMed1989

Bile leaks after simple cholecystectomy.

Drains after cholecystectomy are used commonly to avoid biliary leaks and subsequent peritonitis. Thirty-five patients who had had cholecystectomy without drainage underwent 99mTc-labelled dimethylphenylcarbamoylmethyliminodiacetic acid (HIDA) and ultrasound scans the morning after surgery. Biliary leaks detected by positive HIDA scans occurred in 11 patients. Subhepatic fluid collections were seen on 20 ultrasound scans. There was no relation between biliary leaks and subhepatic collections. Many of the collections were not seen on the HIDA scan, suggesting that they contained blood and not bile. Many of the patients with bile leaks showed no fluid collection. Clinical complications were few and evenly distributed between those with positive and negative scans. We conclude that bile leaks are not an occasional event but occur after 31 per cent of undrained cholecystectomies and that these bile leaks remain clinically unimportant.

Bile↗
PubMed1989

Peripheral somatic sensory neuropathy and skin galvanic response in the feet of patients with diabetes.

The relationship between abnormality in the peripheral sympathetic nervous system (skin galvanic response) and in the peripheral somatic sensory nerve fibers was studied in the lower extremities of 51 patients with diabetes. Deficits in temperature and pain sensations (the small sensory nerve fibers) were related to abnormal sympathetic nervous function (temperature sensation, p less than 0.001; pain sensation, p less than 0.05). The deficits in temperature sensation, in particular, predicted abnormal sympathetic nervous function reliably and vice versa. There was no relationship between deficits in touch and vibration sensations (the large sensory nerve fibers) and abnormal sympathetic nervous function. There was a relationship between skin galvanic response and RR-variation (p less than 0.01). However, abnormality in RR-variation was not related to the deficits in any of the four sensory modalities.

Adult↗
PubMed1988

Cholecystectomy: safe or not safe to drain?

The aim of this study was to determine whether drains influenced the size of subhepatic collections following cholecystectomy, and if these had any affect on complications. Eighty-five patients undergoing cholecystectomy had either no drain, a narrow bore suction drain or an open corrugated drain. Subhepatic fluid collections were measured by real time ultrasound on the first and fifth postoperative days, and thereafter if necessary. The volumes of fluid drained were also measured and clinical complications recorded. The subhepatic collections were, on average, the same whether a drain was used or not. Drains produced volumes considerably in excess of any subhepatic collection measured, but they did not appear to warn of biliary leakage. More complications (28%) were seen in the drained group compared with the undrained group (10.5%), and furthermore, the complications did not seem to occur in relation to the larger collections. One patient who had had a corrugated drain correctly placed developed biliary peritonitis. We suggest that drainage of simple cholecystectomy is unnecessary and, if an open drain is used, potentially dangerous.

Adult↗
PubMed1977

Doppler ultrasound in the functional assessment of extended deep femoral angioplasty.

Twelve patients who have had an extended deep femoral angioplasty (EFDA) for severe lower limb ischaemia have been assessed. The patients underwent a standard exercise ankle pressure test before operation and 6 months after operation. The test included the measurement of resting brachial and ankle pressures, walking distance on a treadmill and the post-exercise pressure response. A limb ischaemic score was derived from these measurements; 8 patients showed an improved score, 3 patients exhibited no change and 1 was worse. The mean improvement in walking distance of the successful cases was 182 per cent (s.d. 96 per cent). There were no amputation during the period of study.

Adult↗
PubMed1977

Urolithiasis after intestinal bypass for morbid obesity.

Urinary calculi, predominantly of oxalate composition, have been noted in 10 to 14% of a large series of morbidly obese patients after jejunoileal intestinal bypass at this institution. Physical and metabolic changes after bypass surgery, including the presence of hyderoxaluria, hyperuricemia, and fluid and electrolyte disturbances are reviewed in their possible relationship to this increased incidence of urolithiasis.

Adolescent↗