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Biomedical subjects

J B Knox

Publications and source records attributed to J B Knox.

11 recordsLinked to original sources
PubMed2005

Comparison of conventional testing to polymerase chain reaction in detection of Trichomonas vaginalis in indigenous women living in remote areas.

There are high rates of Trichomonas vaginalis in remote areas of Central Australia. Conventional tests for T. vaginalis have low sensitivity in this setting. Aims of the study were to estimate the prevalence of T. vaginalis, to assess the presence of clinical signs and symptoms, to compare a T. vaginalis polymerase chain reaction (PCR) test with conventional methods of diagnosis, and to compare the PCR from different samples, including self-collected swabs (SCS). Of 205 women recruited, the prevalence of T. vaginalis was 24%. The prevalence of T. vaginalis was higher in women under 25 years (33%), compared with those who were 25-34 years (26%) and those over 35 years (15%, P < 0.05). The sensitivity of T. vaginalis PCR detection from SCS (94%) was not statistically different from a practitioner-collected HVS (96%), but was superior to urine PCR (74%) and conventional methods. After multivariate analysis, those women with high pH were almost three times more likely to be positive for T. vaginalis (odds ratio = 2.71 with 95% confidence interval 1.06-6.93, P = 0.037). Superior assays such as PCR should be a diagnostic option to adequately screen and treat women with T. vaginalis, in order to reduce complications, including the increased risk of HIV transmission.

Adult↗
PubMed1997

Evidence for altered balance between matrix metalloproteinases and their inhibitors in human aortic diseases.

BACKGROUND: Although abdominal aortic aneurysms (AAAs) exhibit increased expression of matrix metalloproteinases (MMPs), the functional balance between MMPs and their tissue inhibitors (TIMPs) remains uncertain. This report compares the proteolytic activity in normal aorta, aorto-occlusive disease (AOD), and AAA by use of a novel in situ zymographic technique. METHODS AND RESULTS: Infrarenal aortic specimens were obtained from 25 patients undergoing surgery for AOD or AAA and were compared with normal aortic tissue (n = 7) obtained from cadavers. Immunohistochemical staining was performed for collagenase (MMP-1), gelatinase A (MMP-2), stromelysin (MMP-3), TIMP-1, and TIMP-2. Net proteolytic activity was determined with in situ zymography whereby aortic sections were incubated on fluorescently labeled substrate. Proteolytic activity was detected under epifluorescent examination. Compared with normal aortic tissue, AOD and AAA tissue demonstrated marked increases in MMP-1 and MMP-3 immunoreactivity, predominantly in the neointima, and modest increases in TIMP-1. MMP-2 was increased in the diseased aortas, and TIMP-2 was abundant in normal, AOD, and AAA samples. Zymography revealed proteolytic activity in AOD and AAA tissues with active digestion of casein and gelatin substrate, particularly on the luminal portion of the specimens. Normal specimens exhibited no lytic activity. Comparison of AOD and AAA specimens revealed no difference in MMP/TIMP immunoreactivity or net proteolytic activity. CONCLUSIONS: MMP expression is markedly increased in AOD and AAA samples, and an imbalance between MMPs and their inhibitors results in similar proteolytic activity. The eventual formation of aneurysmal or occlusive lesions appears not to result from an ongoing difference in the proteolytic pattern.

Aged↗
PubMed1997

Validation of a new and specific intraoperative measurement of vein graft resistance.

PURPOSE: Clinical studies have revealed that the most important predictor of successful bypass grafting is the origin and quality of the bypass conduit. Attempts at intraoperative evaluation of the hemodynamic properties of the conduit, including assessment of blood flow (Q), pressure gradients (delta P), and resistance (R), have not been useful. This is because each of these parameters measures the characteristics of the graft plus the outflow bed. To date, no specific measurement of the resistive properties of the conduit only is available. The purpose of this investigation was to evaluate longitudinal impedance (ZL) as a measure of conduit-specific resistance and to evaluate its potential in predicting the outcome of infrainguinal vascular reconstructions. METHODS: ZL was measured during surgery in 73 infrainguinal autologous vein reconstructions performed in 68 patients in two separate institutions over a 21-month period. Vein graft ultrasonic transit time Q and delta P (from proximal to distal anastomosis) were measured at baseline and after maximal peripheral vasodilatation with an intraarterial injection of papaverine 30 mg. Waveforms were recorded for 10 seconds at 200 Hz using a digital acquisition system. R was calculated as proximal mean pressure divided by mean blood flow (Q). After Fourier transformation, ZL was calculated as delta P/Q at each harmonic and total ZL (integral of ZL) was defined as the integral of moduli from 0 to 4 Hz. RESULTS: All hemodynamic variables were significantly affected by papaverine vasodilatation (delta P, 3.9 +/- 0.5 vs 6.3 +/- 0.8 mm Hg; Q, 78.2 +/- 7.0 vs 126 +/- 11 ml/min; R, 134 +/- 17 vs 72.7 +/- 6.2 x 10(3) dyne.sec.cm-5; p < 0.0001), except integral of ZL, which remained constant (31.1 +/- 2.8 vs 30.8 +/- 2.8 x 10(3) dyne.cm-5; p = NS). After follow-up of 1 week to 17 months (median, 5 months), the 1-year primary, primary-assisted, and secondary patency rates were 72% +/- 7%, 77% +/- 6%, and 81% +/- 6%, respectively. Using Cox analysis, primary patency was significantly associated with decreased integral of ZL (p = 0.0001), but not with baseline or papaverine-stimulated delta P, Q, delta P/Q, or R integral of ZL > 47 x 10(3) dyne.cm-5 predicted primary failure with 90% positive and negative predictive value. CONCLUSIONS: Intraoperative measurement of integral of ZL in infrainguinal vein grafts is independent of outflow conditions (that is, does not change with papaverine), and hence describes the resistive properties of the conduit only. In addition, these preliminary data suggest that integral of ZL is predictive of short-term primary patency. integral of ZL is the first available hemodynamic measurement that is conduit-specific and may therefore be a better predictor of graft patency than currently available methods.

Aged↗
PubMed1996

Use of growth hormone for postoperative respiratory failure.

BACKGROUND: The authors examined the efficacy of human growth hormone (HGH) in patients dependent on mechanical ventilation who were being weaned from the respirator. METHODS: A total of 53 patients were chosen by the primary surgical team in consultation with the critical care service to undergo HGH therapy. These patients had been receiving standard ICU support and had failed standard ventilator weaning protocols. As such, they were treated with HGH in an attempt to increase respiratory muscle strength and facilitate weaning from mechanical ventilation. RESULTS: General demographic information was recorded. Patients suffered from a high incidence of co-morbid conditions and infectious complications. The average duration of HGH therapy was 38 days, and 81% of the previously unweanable patients were eventually weaned from mechanical ventilation with an overall survival of 76%. Mortality as predicted by APACHE II Scores was significantly less than actual mortality (24% actual mortality vs. 42% predicted mortality, P < 0.05). CONCLUSIONS: This phase I study presents clinical evidence supporting the safety and efficacy of HGH in promoting respiratory independence in a selected group of surgical ICU patients. Randomized, blinded, controlled trials now seem warranted.

Aged↗
PubMed1995

Hypercalcemia associated with the use of human growth hormone in an adult surgical intensive care unit.

BACKGROUND: The anabolic properties of human growth hormone (HGH) may prove beneficial in critically ill surgical patients. Potential effects of hypercalcemia with HGH therapy have not been addressed for adult patients in the intensive care unit. METHODS: We performed a retrospective review of the past 100 patients treated with HGH in a surgical intensive care unit. Laboratory data, including serum calcium levels, were recorded at baseline and during HGH therapy. Additionally, calcium levels in 27 burn patients receiving HGH were compared with calcium levels in a well-matched group of 27 burn patients not receiving HGH. The incidence and severity of hypercalcemia were recorded, with attention to contributing factors and overall outcome. RESULTS: There was a statistically significant increase in the mean +/- SD serum calcium level with the institution of HGH therapy (2.50 +/- 0.20 mmol/L [10.0 +/- 0.8 mg/dL] before HGH vs 2.74 +/- 0.27 mmol/L [11.0 +/- 1.1 mg/dL] during HGH, P < .05). Before HGH, 14% of the patients had hypercalcemia, defined as a calcium level greater than 2.74 mmol/L (11.0 mg/dL). During HGH, 43% of the patients developed hypercalcemia. Before HGH, no patient exhibited severe hypercalcemia, defined as a calcium level greater than 3.12 mmol/L (12.5 mg/dL). However, during HGH, 10% of the patients developed severe hypercalcemia. Elevations in serum calcium levels were correlated with the duration of HGH therapy and renal dysfunction. Burn patients receiving HGH exhibited significantly higher mean +/- SD calcium levels than controls (2.87 +/- 0.32 mmol/L [11.5 +/- 1.3 mg/dL] vs 2.50 +/- 0.17 mmol/L [10.0 +/- 0.7 mg/dL], P < .001). Studies performed in selected patients demonstrated that alterations in parathyroid function, vitamin D metabolism, and thyroid function did not appear to contribute to this effect. CONCLUSION: Prolonged HGH therapy in critically ill surgical patients may result in severe hypercalcemia, particularly in patients with altered renal function. Possible mechanisms for HGH-induced hypercalcemia include increased intestinal absorption and decreased urinary excretion. Outcome was not adversely affected by this biochemical alteration, but careful monitoring of calcium levels should be undertaken in this population receiving HGH.

Adult↗
PubMed1995

Axillary artery injuries secondary to anterior dislocation of the shoulder.

We describe a case report of an axillary artery injury after recurrent anterior dislocation of the shoulder. Review of 22 reported cases reveals that 27% are recurrent dislocations, 86% occurred in patients older than 50, 86% of the injuries are in the third part of the axillary artery, and 68% presented with an axillary mass.

Aged↗
PubMed1995

Efficacy of subcutaneous heparin in prevention of venous thromboembolic events in trauma patients.

Trauma patients have an incidence of deep venous thrombosis (DVT) of 7% to 65%. Conflicting data exists regarding the impact of prophylactic anticoagulant therapy. The purpose of this study is to assess the efficacy of DVT prophylaxis based upon our data and a meta-analysis of the current literature. Literature review revealed five recent studies that met the following criteria: 1) Adult patients sustaining major trauma (injury severity score (ISS) > 10), 2) prospective surveillance for DVT using lower extremity duplex examinations, 3) clear documentation of method of DVT prophylaxis with particular attention to the use of anticoagulation and the corresponding incidence of DVT or pulmonary embolus (PE). Additionally, 66 trauma patients in our intensive care unit were prospectively identified and followed with duplex examinations. Patients received either anticoagulation DVT prophylaxis or pneumatic compression boots. An unpaired Student t test was used to compare the characteristics of patients with and without DVT. A Mantel-Haenszel chi-square meta-analysis was performed on the five recent studies and our own data to compare the incidence of DVT/PE in patients with and without anticoagulation. Meta-analysis of the literature included 1102 patients and demonstrated no benefit from anticoagulation for DVT prophylaxis in trauma patients (10% DVT/PE with anticoagulation versus 7 per cent DVT/PE without anticoagulation, P = 0.771). Our own population had a mean age of 38 +/- 17 years, ISS of 29 +/- 11 and a length of stay (LOS) of 34 +/- 22 days. Sixteen events occurred with 13 (20%) DVTs and three (4%) pulmonary emboli.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Basic concepts of lung function and dysfunction: oxygenation, ventilation, and mechanics.

Acute respiratory failure is a complex disease process. However, it can be understood and appropriately managed if the key components of normal lung function are well understood and abnormalities are specifically identified. These components include oxygenation, ventilation, and respiratory mechanics. The abnormalities, which include hypoxia, hypercarbia, and altered compliance, can be present together or independent of each other. The optimum treatment modality will depend on which component predominates and on the factors producing changes from normal.

Acute Disease↗
PubMed1993

Oxygen consumption-oxygen delivery dependency in adult respiratory distress syndrome.

Considerable attention has been directed toward the study of oxygen transport principles in the adult respiratory distress syndrome (ARDS). In particular, concerns have been voiced regarding disturbed tissue oxygen extraction creating a pathologic dependency of oxygen consumption on oxygen delivery. This article discusses oxygen transport principles, data relevant to the oxygen extraction controversy, and implications regarding the pathogenesis and potential therapies for ARDS.

Bias↗