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Biomedical subjects

M D Smith

Publications and source records attributed to M D Smith.

At least 325 records · Page 18Linked to original sources
PubMed1993

Occipitocervical arthrodesis using contoured plate fixation. An early report on a versatile fixation technique.

A simple, inexpensive, and rigid technique for occipitocervical fixation was evaluated in 14 patients with occipitocervical instability. Posterior arthrodeses of the occipitocervical region were performed using pelvic reconstruction plates and screws as internal fixation devices. At follow-up, which averaged 11.7 months, all patients had fused with minimal complications. This versatile technique, readily adapted to complex deformities and extensible for subaxial fixation, was reviewed.

Adult↗
PubMed1993

Synovial fluid macrophages and blood monocytes differ in their response to IL-4.

IL-4 has been described as a potential anti-inflammatory molecule because of its ability in vitro to down-regulate human monocyte production of proinflammatory mediators. In this study, the activity of IL-4 on mononuclear cells and CD14+ macrophages from a site of chronic inflammation, namely, the joints of patients with rheumatoid and psoriatic arthritis, was investigated and compared directly with its activity on PBMC and monocytes from the same patients. In contrast to the response by blood monocytes, the response to IL-4 by synovial fluid cells was selective; IL-4 did not significantly suppress LPS-induced TNF-alpha production, but decreased CD14 expression to a similar extent in the two cell populations. IL-4 induction of monocyte/macrophage CD23 expression was investigated as a stimulatory response to IL-4, and although significantly increased on synovial fluid CD14+ cells by IL-4, the induction was considerably reduced compared with that measured for blood cells. Activation and differentiation in vitro of blood monocytes reduced their response to IL-4 for decreased TNF-alpha production and induction of CD23 and suggested that these biologic phenomena may contribute to the decreased responsiveness to IL-4 by synovial fluid monocytes/macrophages. Thus, IL-4 does not have the same anti-inflammatory properties in vitro on synovial fluid cells as on blood monocytes.

Antigens, CD↗
PubMed1993

Omental lipoblastoma.

Lipoblastoma is a rare benign neoplasm of fetal fat tissue. To our knowledge, only 73 cases have been reported in the English literature. This is an unusual case of an omental lipoblastoma in a 7-month-old girl.

Female↗
PubMed1993

Management of splenic abscess in immunocompromised children.

Splenic abscess is an infrequent complication in the immunocompromised patient. Six patients underwent splenectomy for presumed splenic abscess from 1987 to 1991. Chemotherapy altered the immune system of four patients; the human immunodeficiency virus (HIV) rendered the other two vulnerable to infection. Five presented with fever but none had leukocytosis; only one exhibited palpable splenomegaly; three had abdominal pain. Cultures documented systemic infection in all but one, an HIV-positive individual. Respiratory embarrassment was the indication for surgery in one patient. In five cases the decision for surgical intervention was made after computed tomography (CT) indicated the presence of multiple splenic lesions and systemic antibiotics failed to resolve the fevers. CT additionally showed hepatic and/or renal microabscesses in four patients. Signs and symptoms experienced preoperatively resolved with splenectomy in all six patients. No additional surgery was required for the patients with extrasplenic abscesses. Surgical pathology determined that three spleens had fungal and two had mycobacterial abscesses. The other was shown to be a spindle cell sarcoma; no abscess was present. This patient had preoperative blood cultures positive for mycobacteria, and the same organism was recovered from retroperitoneal nodes sampled at the time of splenectomy for the sarcoma. Follow-up indicates that no patients experienced surgical complications or sequelae related to their splenic pathology. Splenectomy is necessary and effective in treating splenic abscesses in immunocompromised patients and is appropriate for diagnosis as well as therapy.

Abscess↗
PubMed1993

Serology and carriage of Pseudomonas pseudomallei: a prospective study in 1000 hospitalized children in northeast Thailand.

Throat swab cultures and indirect hemagglutination assay (IHA) for Pseudomonas pseudomallei were done in 1000 randomly selected children at a large hospital in northeast Thailand. During 18 months, 17 children with melioidosis were admitted (0.46% of pediatric admissions excluding neonates born in the hospital). Throat swab was positive for P. pseudomallei in 8 of these but in none of 1000 control children. IHA seroprevalence rose at a conversion rate of 24% per year, from 12% in those 1-6 months old to a plateau at approximately 80% after age 4 years. No control child < 4 had an IHA titer > 1:160. The median titer in children with melioidosis was 1:80 (range, negative [in3]-1:5120). Specificity of IHA declined with age, but high titers (> or = 1:640) remained diagnostically useful. Thus, throat carriage of P. pseudomallei indicates active melioidosis. There is no evidence for an asymptomatic carrier state in children. Environmental exposure to P. pseudomallei in endemic areas begins when the child becomes mobile.

Adolescent↗
PubMed1993

Effects of isoflurane and enflurane on intracellular Ca2+ mobilization in isolated cardiac myocytes.

BACKGROUND: Enflurane and isoflurane may reduce cardiac contractility by altering mobilization and clearance of intracellular Ca2+ (Ca2+i). It was hypothesized that the negative inotropic actions of these agents involve limiting both membrane Ca2+ entry and altering intracellular Ca2+ release. METHODS: The Ca2+i transients in rat ventricular myocytes loaded with fura-2 were recorded from a fluorescence microscope. Transients stimulated by membrane depolarization (suction electrode or elevated [K+]o) or 15 mM caffeine to release Ca2+ from the sarcoplasmic reticulum (SR) were analyzed for net amplitude, maximal rate of rise (VR), average rate of decline (VR) in [Ca2+]i, and duration. RESULTS: Enflurane and isoflurane reduced electrically stimulated Ca2+i transients in a dose-dependent manner. Enflurane depressed the Ca2+i transient amplitude more than isoflurane. Enflurane was more effective than isoflurane in reducing VR and VF in a concentration-dependent manner. At similar concentrations, both enflurane and isoflurane reduced the steady state elevation of [Ca2+]i by 50 mM K+o. Similarly, enflurane and isoflurane depressed caffeine-sensitive release of Ca2+ from the SR. The reduction in the Ca2+i transient because of SR Ca2+ release was greater in enflurane than in equal concentrations of isoflurane. Rates of elevation and decline in [Ca2+]i were also reduced in enflurane and isoflurane. CONCLUSIONS: The negative inotropic actions of enflurane and isoflurane involve a depression of Ca2+ influx during membrane excitation, as well as a reduction in SR Ca2+ release. Slowed rates of elevation in [Ca2+]i indicate that the latter mechanism may, in part, be caused by alterations in the kinetics of SR Ca2+ release.

Animals↗
PubMed1993

Selective management of gastroschisis according to the degree of visceroabdominal disproportion.

OBJECTIVE: This study analyzed the factors influencing the postoperative results after the repair of gastroschisis defects during the past 27 years. SUMMARY BACKGROUND DATA: The clinical results after the repair of gastroschisis abdominal defects have improved appreciably during the past 25 years, with the long-term survival rate in most large children's centers currently being approximately 90%. The improvement in survival has been largely attributed to advances in perioperative care, frequent use of parenteral nutrition, and better techniques of surgical repair. METHODS: Between 1965 and 1992, 84 infants with gastroschisis underwent surgical repair. The management of 52 infants after 1979 was compared with that of 32 during the previous 14 years. Associated anomalies were present in 29%. The average birth weight was 2412 g. In 31%, primary fascial closure was performed. In another 31% with moderate visceroabdominal disproportion (VAD), a silastic chimney was used initially, and complete repair was performed at a second operation. For 25% who had severe VAD, more than two operative reconstructions were necessary. Seven of 52 infants with moderate VAD underwent initial skin-flap closure and secondary repair within 12 days. RESULTS: Almost all complications (27%) and deaths (4%) occurred in infants with severe VAD and were largely unrelated to associated malformations or birth weight. The length of postoperative mechanical ventilation, need for parenteral nutrition, need for multiple operations, and length of hospitalization were all directly related to the severity of the VAD. CONCLUSIONS: Complete repair of gastroschisis at the initial operation is the optimal goal; however, the severity of VAD has permitted this approach in only one third of patients in this study. Delayed repair with a silastic chimney and one or more reconstructive procedures has provided excellent long-term survival with low morbidity and mortality rates. Although skin-flap closure is no longer used initially, this technique has been helpful for the residual defect in infants with severe VAD who have had multiple silon chimney repairs (Applied Biomaterial, Silverdale, WA).

Abdominal Muscles↗
PubMed1993

Anterior occipital cervical reconstruction with a free vascularized osteocutaneous graft: a case report.

Free vascularized osteocutaneous bone grafts are an unusual but effective method to reconstruct complex and extensive defects of skin and bone of the extremities due to trauma, tumor, or infections. Many recent publications support their utility in these situations. In distinction, little literature exists to document the use of free vascularized osteocutaneous flaps in the spine. This is likely due to the infrequent occurrence of concomitant skin and osseous defects that are not manageable by routine spinal and plastic surgical approaches. We recently managed a particularly challenging patient in whom six prior operations--three anterior and three posterior--to decompress and stabilize the occipital-cervical junction had failed. We used a free vascularized distal radius osteocutaneous flap for three purposes: to provide the patient with an optimal chance to obtain an extensive and critically important anterior occipital-cervical arthrodesis, to supply a stable soft tissue envelope for protection of a tenuous dural repair, and to reconstruct an atrophic and scarred posterior pharyngeal wall. We are unaware of any report to date that documents the use of a graft of this type in the spine. We wrote this brief article to document the indications for this operation, to illustrate the problems we encountered in this difficult reconstructive situation, and to report on the progress of our patient to date.

Adolescent↗
PubMed1993

Use of transesophageal echocardiography in the evaluation of traumatic aortic injury.

Indications for aortography following blunt chest trauma are broad and ill-defined. This study prospectively assessed the role of transesophageal echocardiography (TEE) in the evaluation of suspected aortic injury. We used both TEE and aortography to evaluate 69 patients with suspected thoracic aortic injury. The studies were performed and interpreted by staff radiologists and cardiologists. The mean study time for TEE was 27 minutes, whereas the mean study time for aortography was 76 minutes (p < 0.05). No complications occurred with either procedure. Both TEE and aortography revealed no evidence of aortic injury in 61 patients. There was one false-positive aortogram. TEE identified seven aortic injuries; four were confirmed by aortography. One patient underwent thoracotomy and aortic repair based on TEE findings alone. Aortograms yielded false-negative results for two patients; one injury was confirmed at thoracotomy, the other at autopsy. TEE accurately predicted the presence or absence of aortic injury in each case, for a diagnostic sensitivity and specificity of 100%. TEE can be performed safely and efficiently on the multiple-injury patient. We conclude that TEE is useful in the evaluation of suspected aortic injury.

Adult↗
PubMed1993

The influence of renal function on the enantioselective pharmacokinetics and pharmacodynamics of ketoprofen in patients with rheumatoid arthritis.

1. Single oral doses of 100 mg racemic ketoprofen were given to 15 patients (age range: 51-79 years) with rheumatoid arthritis and a range of creatinine clearances (CLCR) from 26 to 159 ml min-1. 2. The fractions unbound of (R)- and (S)-ketoprofen in plasma were determined for each subject after in vitro addition of rac-ketoprofen (enantiomer range: 1.00-6.00 micrograms ml-1) to pre-dose plasma. 3. An index of the antiplatelet effect of ketoprofen in vitro was measured as inhibition of platelet thromboxane B2 (TXB2) generation during the controlled clotting of whole blood (pre-dose) spiked with rac-ketoprofen. 4. In vivo studies revealed significant associations (P < 0.05) between the reciprocal of AUC for both unbound and total (bound plus unbound) (S)-ketoprofen and CLCR. Corresponding relationships were also observed for the (R)-enantiomer of ketoprofen. In addition, the half-life of each enantiomer was negatively correlated with CLCR. There was a positive relationship between the 24 h urinary recovery of combined non-conjugated and conjugated (R)-ketoprofen and CLCR while that for the (S)-stereoisomer failed to reach statistical significance (P > 0.05). 5. There was no difference between AUC for (R)- and (S)-ketoprofen for either unbound or total drug. 6. The mean +/- s.d. percentage unbound of (S)-ketoprofen in plasma (0.801 +/- 0.194%) exceeded (P < 0.05) the corresponding value for its optical antipode (0.724 +/- 0.149%). The percentage unbound of the (S)-enantiomer was higher at 6.00 micrograms ml-1 than that at enantiomer concentrations of 3.50 micrograms ml-1 and below, where it was invariant. The percentage unbound of (R)-ketoprofen was independent of plasma concentration up to 6.00 micrograms ml-1. There were no correlations between the percentage unbound of each enantiomer and either serum albumin concentration or CLCR. 7. The relationship between the serum concentration of unbound (S)-ketoprofen and the percentage inhibition of platelet TXB2 generation was described by a sigmoidal Emax equation for each patient. There was no correlation between the unbound concentration of (S)-ketoprofen in serum required to inhibit platelet TXB2 generation by 50% (EC50) and CLCR. The mean +/- s.d. EC50 was 0.216 +/- 0.143 ng ml-1. 8. These data indicate that diminished renal function is associated with an increased exposure to unbound (S)-ketoprofen, presumably due to regeneration of parent aglycone arising from the hydrolysis of accumulated acyl-glucuronide conjugates. The apparent sensitivity of platelet cyclo-oxygenase to the inhibitory effect of (S)-ketoprofen was not influenced by renal function.

Administration, Oral↗
PubMed1993

Cholangiocarcinoma and familial adenomatous polyposis.

A case of cholangiocarcinoma occurring in a patient with familial adenomatous polyposis--only the fourth such case reported--is presented. Evidence suggests that tumours of the extrahepatic biliary tree may also be an extra-colonic manifestation of familial adenomatous polyposis.

Adenomatous Polyposis Coli↗
PubMed1993

Latex agglutination test for identification of Pseudomonas pseudomallei.

A latex agglutination test was developed and evaluated for the rapid presumptive identification of Pseudomonas pseudomallei, the causative organism of melioidosis. The test was 100% sensitive for 52 isolates of Ps pseudomallei and 100% specific when tested with other medically important Pseudomonas species and Enterobacteriaceae. A subsequent field trial, with clinical specimens from patients with suspected melioidosis, confirmed the sensitivity and specificity of the test.

Burkholderia pseudomallei↗
PubMed1993

Vertebral artery injury during anterior decompression of the cervical spine. A retrospective review of ten patients.

Ten patients who suffered iatrogenic injury to a vertebral artery during anterior cervical decompression were reviewed to assess the mechanisms of injury, their operative management, and the subsequent outcome. All had been undergoing a partial vertebral body resection for spondylitic radiculopathy or myelopathy (4), tumour (2), ossification of the posterior longitudinal ligament (1), nonunion of a fracture (2), or osteomyelitis (1). The use of an air drill had been responsible for most injuries. The final control of haemorrhage had been by tamponade (3), direct exposure and electrocoagulation (1), transosseous suture (2), open suture (1), or open placement of a haemostatic clip (3). Five patients had postoperative neurological deficits, but most of them resolved. We found direct arterial exposure and control to be safe, quick and reliable. Careful use of the air drill, particularly in pathologically weakened bone, as in infection or tumour, is essential. Arterial injury is best avoided by a thorough knowledge of the anatomical relationships of the artery, the spinal canal, and the vertebral body.

Adult↗
PubMed1993

Load-bearing capacity of corticocancellous bone grafts in the spine.

We investigated the relationship between the densities and areas of commonly used autogenous tricortical bone grafts from the iliac crest and the fibula and their mechanical load-bearing abilities. Intact corticocancellous grafts, seven millimeters thick, were obtained during elective spinal arthrodeses from fifty-six patients: from the anterior part of the pelvis in twenty-four patients, the posterior part of the pelvis in twenty-nine patients, and the fibula in three patients. The apparent densities and cross-sectional areas of the cortical and cancellous bone were measured with use of a specific computed-tomographic technique before the specimens were mechanically tested to failure in uniaxial compression. Specimens from the anterior superior iliac spine were able to bear significantly higher axial loads (average, 3230 newtons; range, 430 to 8112 newtons) than were those from the posterior superior iliac spine (average, 1458 newtons; range, 350 to 4639 newtons) (p < 0.001). The cancellous density was the most significant single factor in the prediction of the load to failure of the grafts from the iliac crest (adjusted r2 = 0.58; p < 0.0001). When all of the physical variables (the cancellous and cortical densities and areas) were entered into a multiple-regression model, the combination of the cortical and cancellous densities and the cortical area was a good predictor (adjusted r2 = 0.68; p < 0.001) of the load to failure. The fibular grafts were stronger than those from the other two sites, but they had the least over-all cross-sectional area and cancellous bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Hepatocyte aggregate culture technique for bioreactors in hybrid liver support systems.

Utilizing a modified culture technique for hepatocytes, a high performance suspension culture is possible in which hepatocytes spontaneously form cell aggregates. The aggregates of 20-100 cells have been histologically confirmed to hold a three-dimensional structure, they show a long-term external metabolism and a survival time comparable with standard adhesion cultures. This technique has several advantages in the construction of large scale bioreactors for hybrid liver support systems.

Animals↗