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Biomedical subjects

R C Keniston

Publications and source records attributed to R C Keniston.

At least 37 records · Page 2Linked to original sources
PubMed1993

Predictive value of nerve conduction measurements at the carpal tunnel.

We compared the predictive values of three measurements of sensory conduction of the median nerve at the carpal tunnel (maximum latency difference [MLD], 8-cm latency [S8], and 14-cm latency [S14]) in 2334 hands of industrial workers, workers' compensation patients, and students. The MLD was determined by the centimetric technique. The MLD was the most sensitive and efficient measurement for predicting carpal tunnel syndrome (CTS). An MLD > or = 0.40 ms correctly identified 86.3% of 753 hands with CTS. The MLD correlated best with CTS and with the primary diagnostic category (CAT). MLD was the second factor selected in stepwise regression analysis for CAT (numbness was first and S8 was third). The MLD was the most important factor for predicting persistent or de novo CTS in a 5-year follow-up of 630 hands. Thus, the MLD was the most reliable nerve conduction study measurement for predicting current or future CTS in these subjects' hands.

Adult↗
PubMed1993

Rehabilitation of carpal tunnel surgery patients using a short surgical incision and an early program of physical therapy.

One goal of surgery for carpal tunnel syndrome is to return the patient to work or full-time activities in the shortest possible period of time. The authors evaluated the effectiveness of two incisions, a short incision less than 2.5 cm and an incision greater than 2.5 cm, both combined with a program of active postoperative hand-therapy in a group of 216 patients (293 release). When compared to other techniques with or without active physical therapy, our combined program achieved as short a median return-to-work interval as any other method, both for workers' compensation patients (21 days) and for private/Medicare/welfare patients (10 days). The operating time averaged 7 minutes, and postoperative complications were few. The findings suggest that early hand therapy is more important than the short incision for minimizing the interval for regaining normal function and for decreasing the time-loss cost.

Adolescent↗
PubMed1993

Validation of occupational hand use categories.

As part of a study of the etiology of carpal tunnel syndrome in industry, we developed a measure of occupational hand use activities, "Occupational Hand Use" (OHU), using 471 workers from four industries. This categorization has five categories based primarily upon observed relative force and secondarily upon observed relative repetitions. Because the validity of this OHU categorization has been questioned, we devised a study to validate this variable by demonstrating its reliability. Using discriminant analysis, we show that the OHU categorization accurately reflects the subjective impressions of other industrial workers (605 workers from four other industries in the United States and Japan). Within each validation industry, 68 to 88% of all workers were classified precisely to the correct OHU category, and an additional 10 to 25% were classified to within one OHU category, for a hit or near-miss rate of 87 to 98%. The major classification error was due to some workers overestimating the repetitiousness of their jobs. An equation for calculating OHU from subjective or objective data is provided.

Adult↗
PubMed1993

Carpal tunnel syndrome and its relation to general physical condition.

Risk for carpal tunnel syndrome is closely related to general physical condition. Our findings confirm that healthy people are less likely to develop median nerve conduction abnormalities at the carpal tunnel than are unhealthy people. Being overweight, older, and physically inactive are major risk factors for slowing and clinical CTS. Workers' compensation patients with CTS, as a group, are identifiable by being overweight and physically inactive. Individual factors, such as body mass index, age, wrist dimensions, and physical activity, are far more important for determining who develops clinical CTS than are job-related factors, such as specific job, force or repetitions, duration of employment, or industry.

Adolescent↗
PubMed1992

Simple decompression of the ulnar nerve: an alternative to anterior transposition.

Anterior transposition and/or medial epicondylectomy are often considered procedures of choice for ulnar neuropathy at the elbow. Much experience suggests simple decompression to be a comparably effective alternative which involves less trauma, morbidity, and rehabilitation time. The post-operative clinical and electrophysiological results of 52 cases of simple decompression (41 patients) are summarized. Excellent or good clinical results were found in 75% of the nerves. Mean ulnar motor conduction velocities were significantly improved post-operatively, although nerve conduction parameters did not consistently correlate with clinical outcome. The average return-to-work time was 5.1 weeks. The advantages of simple decompression make it the procedure of choice for most cases of ulnar neuropathy.

Adult↗
PubMed1992

Longitudinal study of median nerve sensory conduction in industry: relationship to age, gender, hand dominance, occupational hand use, and clinical diagnosis.

As part of a longitudinal study of the cause of carpal tunnel syndrome in industry, we evaluated sensory conduction of the median nerve in relation to age, gender, hand dominance, occupational hand use, and clinical diagnosis. The original 1984 study group consisted of 942 hands of 471 industrial workers, and the follow-up study group in 1989 consisted of 630 hands of 316 (67%) of these same workers. The palmar segmental stimulation technique was employed, and slowing was defined as a maximum latency difference of 0.4 msec or more after adjustment for temperature variation. There was no significant change in the prevalence of slowing between 1984 and 1989 (23% in 1984, 22% in 1989), and slowing was still strongly correlated with increased age but not with gender. Slowing continued to be more prevalent in the dominant hand. Slowing was no longer correlated in any fashion with occupational hand use. The prevalence of probable carpal tunnel syndrome was still strongly correlated with the degree of slowing. Age and hand dominance were more important than any job-related factor in the prediction of slowing after 5 years.

Adolescent↗
PubMed1992

Obesity as a risk factor for slowing of sensory conduction of the median nerve in industry. A cross-sectional and longitudinal study involving 429 workers.

As part of a longitudinal study of the etiology of carpal tunnel syndrome in industry, we evaluated weight and body mass index (BMI) as risk factors for slowing of sensory conduction of the median nerve. Using nerve conduction studies, we evaluated 858 hands of 429 industrial workers in 1984 and reevaluated 630 hands of 316 of these same workers in 1989. Weight and BMI were strongly and positively correlated with the maximum latency difference (MLD). In 1984 and 1989 the risk for abnormal nerve conduction averaged 3.5-fold and 4.1-fold greater, respectively, in the obese workers than in the slender workers. In stepwise regression analysis for 1989 MLD based on 1984 factors, the BMI was the number one factor selected, followed by age, wrist depth/width ratio, hand dominance, and exercise level. None of three 1984 job-related factors (occupational hand use, duration of employment, or industry) was an independent predictor of 1989 MLD. This study suggests that individual characteristics, not job-related factors, are the primary determinants of slowing of sensory conduction of the median nerve and carpal tunnel syndrome.

Adult↗
PubMed1992

Effect of vitamin B6 supplementation on gentamicin nephrotoxicity in rabbits.

Therapeutic use of gentamicin (GM) in a clinical setting may result in nephrotoxicity, most commonly presenting as acute tubular necrosis (ATN). We have previously observed decreased plasma pyridoxal 5'-phosphate (PLP) levels in rabbits given therapeutic doses of GM and endeavor in this study to determine if vitamin B6 supplementation (B6S) could protect against the nephrotoxicity of GM. Twenty-one rabbits were randomly assigned to 1 of 7 treatment groups of 3 rabbits each. Three of the groups received 10 mg GM/kg with either 10 mg B6S, 100 mg B6S or 0.9% saline. Three of the groups received 40 mg GM/kg with either 10 mg B6S, 100 mg B6S, or normal saline. The control group only received 100 mg B6S. All treatments were administered im once daily for 5 d. Blood was drawn for chemical assays on day 0 prior to any treatments and 2 h after each respective treatment on days 1, 3 and 5. After 5 d, the rabbits were euthanatized and kidneys were excised for histological evaluation by light microscopy. At the 40 mg GM/kg/d dose, significant mild to moderate ATN was observed in the saline controls, which was prevented by either dose of B6S. Only a few animals given 10 mg GM/kg/d showed any renal pathology and that was minimal. Unexpectedly, 1 rabbit given only 100 mg B6S/d but no GM had interstitial nephritis with focal ATN. We conclude that vitamin B6 can protect against the nephrotoxicity of GM in rabbits, but that further study is needed on the possible nephrotoxicity of high doses of B6S.

Animals↗
PubMed1991

Depression of vitamin B6 levels due to dopamine.

Dopamine is a commonly used pressor agent. Frequently recognized side effects other than occasional reports of pedal gangrene respond to reduction of dose. Because a number of compounds interfere with vitamin B6 and dopamine toxicity in animals is modified by B6, we studied the dopamine-vitamin B6 interaction in rabbits. Six animals received 40 mg dopamine/kg and 10 mg pyridoxine injections; 6 received dopamine and saline. Dopamine administration led to an average fall of 20% (p = 0.04) in plasma pyridoxal 5'-phosphate (PLP) levels, which declined 42% by day 5. Three days later, a 25% decrease persisted (p = 0.03). Dopamine with pyridoxine caused a PLP rise of 65% (p = 0.007), but the post-study level was 28% lower than baseline (p = 0.04). We interpret our data to mean that dopamine reduced PLP levels during and 3 days after the study, and that dopamine appeared to increase the requirements for B6. We worry that dopamine given with other drugs, ie gentamicin, digoxin and theophylline which are frequently used in critical care settings, could aggravate alterations of requirements for or body stores of vitamin B6, creating B6 deficiency.

Animals↗
PubMed1990

Depression of vitamin B6 levels due to gentamicin.

The renal toxicity of gentamicin is altered by dietary protein modifications, bicarbonate and acetazolamide administration, magnesium supplementation, polyaspartic acid, piperacillin, hypercalcemia and calcium channel blockers. Renal tissue gentamicin levels have an undetermined role. Reduction of renal pyridoxal 5'-phosphate (PLP- by gentamicin has been shown, as has protection from nephrotoxicity by administration of vitamin B6. To explore an interaction between gentamicin and vitamin B6, gentamicin (5 mg/kg) was given to rabbits by ip injection, with either pyridoxine (10 mg) or isovolemic saline for 3 weeks. There was not a difference between gentamicin levels for animals given gentamicin and pyridoxine versus those given gentamicin and saline. Gentamicin administration led to a 47% fall (p = .0001) in plasma PLP levels. Three days after the last gentamicin administration, the animals maintained a 32% decrease from the pre-gentamicin baseline values (p = 0.02). When pyridoxine was administered concurrently with gentamicin, the PLP rise of 49% was significant (p = 0.001). The mean level after the study (6%) was not significantly lower than baseline (p = .6). We believe that gentamicin interfers with vitamin B6 metabolism, but that vitamin B6 status does not affect levels of gentamicin. A number of drugs affect B6 levels, creating the potential for hypovitaminosis B6 to be an important mechanism of drug-drug interaction in seriously ill patients, particularly in sick newborns or the elderly with lower average PLP levels.

Animals↗
PubMed1990

Depression of vitamin B6 levels due to theophylline.

Theophylline overdosage can cause life-threatening symptoms, that include seizures and cardiac arrhythmias, and can be fatal. Neither the onset of toxicity nor the severity of symptoms is well predicted by serum theophylline concentrations. Since depressed vitamin B6 plasma levels can occur in patients receiving theophylline, we explored a B6-theophylline interaction in a rabbit model. Administration of theophylline preparations intraperitoneally (aminophylline) or orally (sustained release anhydrous theophylline) resulted in a 47% depression of plasma pyridoxal 5'-phosphate (PLP) levels. The 87% increase in PLP with pyridoxine administration was only 18% when aminophylline was also given. The mechanism of the theophylline-B6 interaction is obscure. Ethylenediamine in some theophylline preparations binds directly to PLP, potentially increasing the less direct theophylline effect. Pyridoxine supplementation resulted in higher average PLP levels but did not prevent death in animals with profoundly low PLP levels. If these data apply to humans, B6 deficiency may contribute to chronic theophylline toxicity; however, pyridoxine administration in the dosage used may not prevent toxicity. Larger doses may prove beneficial after further investigation.

Administration, Oral↗
PubMed1987

Pyridoxal 5'-phosphate as an antidote for cyanide, spermine, gentamicin, and dopamine toxicity: an in vivo rat study.

Pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, readily forms complexes with a wide variety of potentially toxic substances, including cyanide (KCN), spermine (SPM), gentamicin (GM), and dopamine (DOP). The role of PLP as an antidote for these toxicants in vivo was studied. Rats were given intraperitoneal injections of the toxicant, followed by injections of either saline or PLP. For KCN, PLP increased the LD50 from 0.088 to 0.188 mmol/kg and extended the survival time at the highest dose employed from a median of 3 min to a median of 60 min. For SPM, PLP increased the LD50 from 0.162 to 0.262 mmol/kg and prevented death from renal failure at all doses employed except the highest. PLP protected against GM-induced neuromuscular paralysis and death. In the case of DOP, results were equivocal, but no deaths were seen in the PLP-treated rats. The combination of individually nontoxic doses of GM, DOP, and SPM caused death with renal tubular necrosis, pulmonary edema and hemorrhages, congestion of the viscera, and a diffuse coagulopathy. Because many seriously ill patients have elevated SPM levels and are given GM and/or DOP, we suggest that further investigation of the potential protective role of PLP in serious illness be undertaken.

Animals↗