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Biomedical subjects

R F Wilson

Publications and source records attributed to R F Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1993

Efficacy of a beta-lactamase inhibitor combination for serious intraabdominal infections.

A double-blind trial was conducted in 385 patients with suspected bacterial intra-abdominal infections to compare the efficacy and safety of ampicillin-sulbactam with cefoxitin. Patients were randomized to receive either 3 g ampicillin-sulbactam (2 g ampicillin-1 g sulbactam), or 2 g cefoxitin, every 6 hours. To be evaluable, patients had to demonstrate positive culture evidence of peritoneal infection at the time of operation. A total of 197 patients were evaluable for clinical efficacy. The two treatment groups were comparable in demographic features and in the presence of risk factors for infection. Clinical success (absence of infection and of adverse drug reaction) was observed in 86% of patients in the ampicillin-sulbactam group and 78% in the cefoxitin group. Eradication of infection occurred in 88% of the ampicillin-sulbactam group and 79% of the cefoxitin group. There were no differences in the nature or frequency of side effects observed in the two groups. Ampicillin-sulbactam demonstrated no difference in safety or efficacy when compared with cefoxitin in the treatment of serious intra-abdominal infections of bacterial origin.

Abdomen, Acute↗
PubMed1993

Concentrations of thiocyanate, hypothiocyanite, 'free' and 'total' lysozyme, lactoferrin and secretory IgA in resting and stimulated whole saliva of children aged 12-14 years and the relationship with plaque accumulation and gingivitis.

Resting and stimulated whole saliva was collected from 94 children aged 12-14 years and analyzed for thiocyanate, hypothiocyanite, 'free' and 'total' lysozyme, lactoferrin and secretory IgA. Clinical assessments of the amounts of plaque and gingival inflammation were made, and plaque was collected for determination of dry weight. An inverse relationship was observed between salivary thiocyanate concentrations in both resting and stimulated saliva and the amounts of plaque and gingival inflammation in these subjects (p < 0.05). Lactoferrin concentration in stimulated saliva was directly related to the amounts of plaque and gingivitis (p < 0.05). 'Total' lysozyme concentration in stimulated saliva was directly related to the amount of plaque (p < 0.05), and the 'free' lysozyme concentration in the same saliva was directly related to the amount of gingivitis (p < 0.05). The direct relationship observed between clinical measurements and both lysozyme and lactoferrin concentrations in saliva may have been due to contributions from gingival crevicular fluid. Cluster analysis identified three groups of subjects with different profiles in resting whole saliva, and in particular with different levels of secretory IgA. A statistically significant difference was observed in the quantity of plaque collected from subjects in two of these groups (p < 0.05). These results from cluster analysis using resting whole saliva from children confirmed the findings of a previous study with young adults.

Adolescent↗
PubMed1993

Efficacy of chlorhexidine in disinfecting dentinal tubules in vitro.

Solutions of 0.2% and 2% chlorhexidine, 0.2% and 2% sodium hypochlorite (NaOCl) and normal saline were tested for their efficacy in disinfecting dentinal tubules following root canal irrigation in vitro. Freshly extracted bovine incisor roots were prepared as cylindrical shapes, 4 mm high and 5 mm wide with a lumen 2.1 mm wide. After mechanical removal of the cementum and elimination of the smear layer on the dentine surface with EDTA and NaOCl, the root sections were autoclaved and the dentinal tubules infected with E. faecalis (NCTC 775) by incubating in yeast extract glucose broth for 1 week. The root canals were irrigated with 20 ml of an irrigant solution using a syringe. Each irrigant was used in six specimens. Dentine was removed from the canal wall by sterile burs of increasing diameter to give samples 100, 100-300 and 300-500 microns deep. The dentine samples were then cultured to determine the presence and quantity of remaining micro-organisms. The results indicated that chlorhexidine and NaOCl were equally effective antibacterial agents at similar concentrations against the test microorganism. They significantly reduced the bacterial counts in the first 100 microns of dentinal tubules, however up to 50% of dentine samples remained infected following use of both agents.

Analysis of Variance↗
PubMed1993

Regional differences in sympathetic reinnervation after human orthotopic cardiac transplantation.

BACKGROUND: In the majority of humans > or = 1 year after cardiac transplantation, cardiac norepinephrine (NE) stores reappear, suggesting late sympathetic reinnervation. METHODS AND RESULTS: To determine whether there are regional differences in reinnervation, we measured markers of sympathetic reinnervation of the sinus node (SN) and left ventricle (LV) in five early transplant recipients (< or = 4 months after cardiac transplantation), 45 late transplant recipients (> or = 1 year after cardiac transplantation), and seven normally innervated control patients. SN reinnervation was defined as an increase in heart rate by more than five beats per minute after injection of tyramine into the artery supplying the SN. LV reinnervation was defined as a measurable LV NE release after left main coronary injection of 8 micrograms/kg tyramine. In 13 patients with previously known LV reinnervation, regional LV reinnervation was assessed by NE release after subselective injection of tyramine (4 micrograms/kg) into the proximal left anterior descending and circumflex arteries. Five of five patients < or = 4 months after cardiac transplantation had no change in heart rate and no LV NE release, confirming early, total denervation. In contrast, > or = 1 year after cardiac transplantation, tyramine caused a heart rate increase (eight to 49 beats per minute) in 32 of 45 patients and LV NE release in 33 of 45. Although LV NE release was correlated with the change in heart rate in late cardiac transplantation recipients (r = .61), eight of 45 had only heart rate response, nine had only LV NE release, and four had neither. In late cardiac transplantation recipients with LV reinnervation, tyramine caused NE release from both the anterior descending and circumflex perfusion fields in 10 of 14, but one of 14 patients released NE only after circumflex tyramine and three of 14 only after left anterior descending tyramine stimulation. Tyramine caused a marked heart rate increase and LV NE release in all control patients. CONCLUSIONS: Sympathetic reinnervation after cardiac transplantation is regionally heterogeneous. SN reinnervation is not associated necessarily with LV reinnervation, and LV reinnervation can involve the anterior and posterior walls together or separately.

Cardiac Catheterization↗
PubMed1993

Experimental atrial septal defect closure with a new, transcatheter, self-centering device.

BACKGROUND: Despite two decades of research, a transcatheter atrial septal defect closure device is not available for clinical use. We have designed a new superelastic Nitinol-Dacron, double-disk, self-centering, atrial septal defect closure device and studied its efficacy in a canine model of atrial septal defects. METHODS AND RESULTS: Atrial septal defects were created surgically in 20 adult dogs using either a 7.5-mm or 10-mm punch. Percutaneous transcatheter closures were attempted using a new device. The device sizes used were 20 mm in 6 dogs, 22 mm in 9, and 25 mm in 5 (22.1 +/- 1.9 mm, mean +/- SD). The stretched atrial septal defect diameter was 10.5 +/- 1.3 mm, and the device to stretched atrial septal defect diameter ratio was 2.1 +/- 0.3. Closures were successful in 19 studies and unsuccessful in 1. Angiography showed a left-to-right shunt in all 20 dogs before closure. Immediately after closure (n = 19), there were no shunts in 17 and trivial shunts in 2. Six dogs were followed for a period of 4.7 +/- 3.0 months (range, 2 to 8 months). The trivial shunt present in 1 animal immediately after closure had closed by the time of the repeat study. Spontaneous embolization of the device was not seen during follow-up. A solitary wire fracture was found 8 months after closure in 1 device. Light microscopy at 8 weeks in 3 dogs showed the devices to be covered by smooth endocardium, enmeshed in mature collagen tissue, with a minimal mononuclear cell infiltration. Retrievability was assessed by deliberately embolizing 4 devices in 2 dogs into the right atrium (n = 1) and pulmonary artery (n = 3). All devices were successfully retrieved with a snare. CONCLUSIONS: This feasibility study demonstrates that this new self-centering atrial septal defect closure device has a number of design features that permit effective and safe closures in a canine model. These results support the investigation of this device in human clinical trials.

Alloys↗
PubMed1993

Techniques for vascular access when venous entry is impossible. Route depends on urgency and the agent to be administered.

When a patient requires parenteral fluid or drug administration and venous cannulation cannot be performed, consider less typical routes. Intraosseus infusions are usually more effective in children than adults, but intraosseus cannulation failure may occur in as many as 20% of patients. Intra-arterial infusions are possible if pump pressures are kept high. Hypodermoclysis (infusion into the subcutaneous tissues) can correct moderate dehydration. Administering resuscitative drugs endobronchially is usually safe and effective, although pulmonary function may be somewhat compromised. A number of drugs may be given sublingually, either by injection or topical application. Finally, the corpora cavernosa of the penis may be used for short-term, large-volume fluid administration.

Critical Illness↗
PubMed1993

Alternative techniques for gaining venous access. What to do when peripheral intravenous catheterization is not possible.

There are a number of therapeutic options for fluid administration in patients who lack usual venous access. Ways to establish this access include limb elevation and wrapping, the application of nitroglycerin ointment to dilate veins, and blood pressure cuff inflation. Ultrasonography can also be used to delineate vascular structures. Cutdown procedures are the oldest, most direct method to reach uncommon venous sites, such as the inferior epigastric, intercostal, iliac, and lateral thoracic veins. Today, cutdown procedures are regarded as the method of last resort, and they should be performed in operating suites or similar settings. Possible complications include inadvertent arterial puncture and hemorrhage.

Catheterization, Central Venous↗
PubMed1993

Splanchnic mucosal perfusion effects of hypertonic versus isotonic resuscitation of hemorrhagic shock.

A porcine hemorrhagic shock (HS) model was used to assess the splanchnic mucosal and systemic effects of hypertonic versus isotonic crystalloid resuscitation. Animals were bled to a mean arterial pressure of 40 mm Hg for 1 hour and then resuscitated with equivalent sodium loads of LR, 7.5 per cent hypertonic saline (HSS), or 7.5 per cent HSS with 6 per cent Dextran (HSD). Intestinal mucosal blood flow (IMBF) was measured by a laser Doppler flow probe placed on the mucosa of the small bowel. Following resuscitation the cardiac output (CO) (relative to baseline values) was significantly higher with HSD (158 17 per cent) and HSS (137 24 per cent) than with LR (84 27 per cent) (P < 0.005). There was prompt restoration of IMBF with both HSD (126 31 per cent) and HSS (106 22 per cent) (vs baseline). Resuscitation with LR was associated with a persistent reduction in IMBF (52 16 per cent) despite restoration of mean arterial pressure and cardiac output to baseline levels (P < 0.05). Thus, hypertonic saline solutions may serve an adjunctive role in the resuscitation of hemorrhagic shock by restoring intestinal nutrient blood flow and, thereby, preventing gut barrier impairment, bacterial translocation, and organ failure.

Animals↗
PubMed1993

Right ventricular response after myocardial contusion and hemorrhagic shock.

BACKGROUND: Prior functional studies on myocardial contusion (MC) have emphasized left ventricular performance even though the right ventricle (RV) is more likely to be injured after blunt trauma. Furthermore, associated injuries requiring resuscitation and surgery are frequently present. Our aim was to evaluate the impact of MC on RV function after MC and subsequent resuscitation from hemorrhagic shock. METHODS: RV performance was evaluated with a modified pulmonary artery catheter that determines RV volumes and ejection fraction (RVEF), as well as filling pressures and cardiac output in an anesthetized swine model. RESULTS: MC caused a 28% fall in mean arterial pressure and a 33% decrease in cardiac output. RVEF was 82%, and RV stroke work was 49% of baseline after injury. Resuscitation of hemorrhagic shock to baseline preload or greater failed to restore mean arterial pressure or cardiac output (depressed 23% and 22%, respectively). RV end-diastolic volume returned to baseline and central venous pressure was increased. RV dysfunction was depicted by a sustained depression of RV stroke work and RVEF. CONCLUSIONS: Impaired RV compliance and contractility, which was evident throughout this study, may hamper resuscitative efforts after multiple blunt trauma. RV monitoring may be useful in this setting.

Animals↗
PubMed1993

Hemodynamic resuscitation.

Hemodynamic resuscitation for hemorrhagic shock should be directed toward optimizing oxygen delivery to the tissues. A combination of volume restoration and inotropic support usually is needed. This article identifies the basis and strategies necessary for accomplishing these goals.

Cardiotonic Agents↗
PubMed1993

Gastric intramucosal acidosis in patients with chronic kidney failure.

BACKGROUND: Patients with chronic kidney failure have an increased incidence of gastrointestinal complications, particularly bleeding from the stomach. Diminished mucosal blood flow is thought to be an important etiologic factor for such bleeding. METHODS: Eleven patients with kidney failure on maintenance dialysis underwent placement of a gastric tonometer for the determination of gastric intramucosal pH (pHi) before and during dialysis. The arterial pH (pHa), calculated pHi, and pHa-pHi differences were compared with the results in a control group of seven normal volunteers. RESULTS: The patients with chronic kidney failure had a mean (+/- SD) pHa (7.36 +/- 0.04) similar to that found in seven control subjects (7.37 +/- 0.04). However, the gastric mucosal pH in the patients on dialysis (7.20 +/- 0.17) was lower than in the seven control subjects (7.38 +/- 0.06) (p < 0.01). A gastric mucosal pH thought to be predictive of either bleeding from stress ulceration (pHi < 7.32) or mucosal ischemia (pHi-pHa difference > 0.13) was found in nine (82%) of the patients with kidney failure and in only one (14%) of the control subjects (p < 0.001). CONCLUSIONS: This new preliminary finding suggests that the high incidence of gastric bleeding in chronic kidney failure may be related to mucosal ischemia.

Acidosis↗
PubMed1992

Coronary revascularisation in insulin-dependent diabetic patients with chronic renal failure.

Insulin-dependent diabetic patients found to have substantial coronary artery disease at the time of assessment for renal transplantation have 2-year survival of less than 50%. Because most of these patients have no angina symptoms their management is controversial. We tried to find out whether coronary artery revascularisation in such patients might decrease the combined incidence of unstable angina, myocardial infarction, and cardiac death. 151 consecutive insulin-dependent diabetic candidates for renal transplantation underwent coronary angiography. 31 had stenoses greater than 75% in one or more coronary arteries, atypical chest pain or no chest pain, and a left ventricular ejection fraction greater than 0.35. Of these, 26 agreed to be randomly assigned medical treatment (a calcium-channel-blocking drug plus aspirin) or revascularisation (angioplasty or coronary bypass surgery). 10 of 13 medically managed and 2 of 13 revascularised patients had a cardiovascular endpoint within a median of 8.4 months of coronary angiography (p < 0.01). 4 medically managed patients died of myocardial infarction during follow-up. Thus, revascularisation decreased the frequency of cardiac events in insulin-dependent diabetic patients with chronic renal failure and symptomless coronary artery stenoses. These findings suggest that diabetic renal transplant candidates should be screened for silent coronary artery disease, because revascularisation may decrease cardiac morbidity and mortality in this population.

Adult↗
PubMed1992

End-diastolic volume. A better indicator of preload in the critically ill.

The relative value of pulmonary artery wedge pressure (PAWP) and right ventricular end-diastolic volume index (RVEDVI) as a reflection of the preload status of the critically ill was determined in 29 patients. Regression analysis of 131 hemodynamic studies demonstrated that cardiac index (CI) correlated better with RVEDVI (r = .61) than did PAWP (r = .42). Comparisons of PAWP and RVEDVI showed that possible misleading information concerning filling volume was provided by the PAWP at some time in 15 (52%) of these patients. In 15 patients given 22 fluid challenges, patients with a high PAWP (greater than or equal to 18 mm Hg) "responded" with a rise in CI more frequently than did patients with a low PAWP (less than 12 mm Hg). However, all eight patients with a RVEDVI less than 90 mL/m2 responded with a rise in CI, but all seven patients with a RVEDVI greater than or equal to 139 mL/m2 failed to respond. Thus, RVEDVI more accurately predicted preload recruitable increases in cardiac output.

Adult↗
PubMed1992

The relationship between 48-h dental plaque accumulation in young human adults and the concentrations of hypothiocyanite, 'free' and 'total' lysozyme, lactoferrin and secretory immunoglobulin A in saliva.

Samples of resting and stimulated whole saliva and stimulated parotid saliva were collected from 40 young adults. One week later, after 48 h on a standardized diet without oral hygiene, all available plaque was collected for dry weighing. An inverse relationship was found between the 'free' lysozyme concentration in stimulated parotid saliva and plaque dry weight (r = -0.46, p less than 0.01). There were no other statistically significant correlation coefficients between concentrations of individual salivary constituents and plaque dry weight. However, cluster analysis of constituents in resting whole saliva revealed three groups of subjects with different salivary profiles, and in particular with different concentrations of both IgA and hypothiocyanite. Subsequent analysis revealed differences in plaque dry weight between the groups, demonstrating the potential biological significance of cluster membership based on salivary factors.

Adult↗
PubMed1992

Effect of increased intra-abdominal pressure on mesenteric arterial and intestinal mucosal blood flow.

The effects of increased intra-abdominal pressure (IAP) on intestinal blood flow were studied in eight anesthetized pigs. Mesenteric artery blood flow (MABF), intestinal mucosal blood flow (IMBP), tonometric intramucosal pH (pHi), mean BP (MAP), cardiac output (CO), and pulmonary artery wedge pressure (PAWP) were measured as IAP was raised to 10, 20, 30, and 40 mm Hg by infusing lactated Ringer's solution (LR) into the peritoneal cavity. The MAP was kept constant with IV LR. Cardiac output fell slightly from 5.4 +/- 1.1 at baseline to 4.0 +/- 1.2 L/min at an IAP of 40 mm Hg (p less than 0.05). An IAP of 20 mm Hg caused significant decreases in MABF (73% +/- 22% of baseline) (p less than 0.05) and IMBF (61% + 12% of baseline) (p less than 0.05). These changes became progressively greater as the IAP was increased to 40 mm Hg. The pHi fell to 6.98 +/- 0.14 at 40 mm Hg IAP (p less than 0.01), indicating severe mucosal ischemia. Thus increased IAP can cause severe intestinal ischemia, which may be more important than the cardiac, pulmonary, and renal changes usually described.

Animals↗
PubMed1992

Effect of increased intra-abdominal pressure on hepatic arterial, portal venous, and hepatic microcirculatory blood flow.

The effects of increased intra-abdominal pressure (IAP) on hepatic perfusion were studied in five anesthetized pigs. Doppler flow probes were used to measure hepatic artery blood flow (HABF) and portal venous blood flow (PVBF), and laser Doppler flowmetry was used to assess changes in hepatic microvascular blood flow (HMVBF). Hepatic blood flow responses to 10, 20, 30 and 40 mm Hg increases in IAP were assessed while the mean arterial BP (MAP) was maintained at baseline levels with IV crystalloid infusions. Although cardiac output and MAP were normal, HABF and HMVBF fell significantly with 10 mm IAP, and at 20 mm Hg IAP, HABF was 45% of the control value, PVBF was 65% of the control value, and HMVBF was 71% of the control value (p less than 0.05). At 30 and 40 mm Hg, hepatic blood flow was reduced even more. Thus, modest increases in IAP can cause significant impairment of hepatic perfusion despite a normal BP and cardiac output.

Abdomen↗