High alveolar surface tension increases clearance of technetium 99m diethylenetriamine-pentaacetic acid.

The effect of high alveolar surface tension on alveolar epithelial permeability was studied in anesthetized closed-chest mongrel dogs. Alveolar surface tension was elevated by displacement of pulmonary surfactant from the alveolar hypophase by the aerosolized detergent dioctyl sodium sulfosuccinate (OT). After measurement of baseline hemodynamics, arterial blood gases, and airway pressure, the dogs were separated into groups: Group I inhaled a 1% solution of OT (15 mg/kg) in a vehicle of equal parts saline and ethanol; group II inhaled the same volume of vehicle without OT. The pulmonary clearance of technetium 99m diethylenetriamine-pentaacetic acid (99mTc-DTPA) (half-time in minutes) was studied immediately after aerosol (OT and vehicle) delivery and compared with that of historical control values. No change was seen in arterial blood gases and airway pressure after vehicle inhalation, whereas OT caused a marked fall in arterial oxygen tension and increase in airway pressure. Vehicle inhalation effected only a slight increase in DTPA clearance, whereas OT significantly reduced half-time over control and group II. These data suggest that high alveolar surface tension increases alveolar epithelial permeability.     

Positive end-expiratory pressure accelerates lung water accumulation in high surface tension edema

The effect of positive end expiratory pressure (PEEP) on the rate of lung water accumulation with high surface tension pulmonary edema was examined. Alveolar surface tension was elevated by inhalation of 15 mg/kg of the aerosolized detergent dioctyl sodium sulfosuccinate (OT). Hemodynamic measurements, blood gases, and colloid oncotic pressures were recorded in anesthesized dogs for 2 hours after surfactant displacement and elevation of PEEP to 10 cm H2O pressure (group II; n = 10). These data were compared with those of an identical protocol that used only 5 cm H2O PEEP (group I; n = 10). Pulmonary extravascular water volume (PEWV) was measured gravimetrically at the end of the experiment. OT inhalation resulted in an immediate fall in Pao2 and rise in venous admixture (QVa/QT), with little change in colloid oncotic pressure or left atrial pressure. In group I, Pao2 and QVa/QT did not improve significantly over 2 hours, whereas both returned to near baseline in group II. PEWV was elevated in group I compared with normal PEWV (historic controls; n = 11) (6.1 +/- 0.07 - 3.6 +/- 0.01 ml/gm dry lung; p less than 0.01); however, PEWV in group II (9.1 +/- 1.0 ml/gm dry lung; p less than 0.01) was greater than in both group I and historic controls. These data indicate that high alveolar surface tension induces pulmonary edema and PEEP accelerates this edema formation.     

Ambulatory Phlebectomy Versus Compression Sclerotherapy: Results of a Randomized Controlled Trial

BACKGROUND: Although no randomized controlled trial has assessed the effects of either compression sclerotherapy or ambulatory phlebectomy, both techniques are used to treat varicose veins worldwide. We performed a randomized controlled trial to compare recurrence rates of varicose veins and complications after compression sclerotherapy and ambulatory phlebectomy. METHODS: From September 1996 to October 1998, we randomly allocated 49 legs to compression sclerotherapy and 49 legs to ambulatory phlebectomy. Our primary outcome parameters were as follows: recurrence rates at 1 and 2 years and complications related to therapy. Eighty-two patients were included, of whom 16 were included with both of their legs. The number of treated legs was therefore 98, but two patients were lost to follow-up. RESULTS: One year recurrence amounted to 1 out of 48 for phlebectomy and 12 out of 48 for compression sclerotherapy (P<0.001); at 2 years, six additional recurrences were found, but then solely for compression sclerotherapy (P<0.001). Significant differences in complications occurring more in phlebectomy than in compression sclerotherapy therapy were blisters, teleangiectatic matting, scar formation, and bruising from bandaging. CONCLUSION: Our results show that ambulatory phlebectomy is an effective therapy for varicose veins of the leg. Recurrence rates are significantly lower than for compression sclerotherapy therapy. If varicose veins persist 4 weeks after compression sclerotherapy, it can be argued that to reduce the risk of future recurrence ambulatory phlebectomy should be considered as the better treatment option.     

Increased salt retention and hypertension from non-steroidal agents in the elderly

We studied blood pressure and natriuretic responses to acute salt loading, and the effect of non-steroidal anti-inflammatory agents on these responses, in five healthy normotensive women aged 65 to 71 years. Five women aged 25 to 31 years acted as controls. Intravenous saline loading, with and without prior ingestion of ibuprofen, was 15 ml/kg/h for 3 h. Baseline blood pressures were higher in the elderly. Saline infusion without ibuprofen raised systolic blood pressure (SBP) by about 25 mmHg in the older group only. Ibuprofen increased baseline SBP in the elderly (129 +/- 6 vs. 116 +/- 5 mmHg, p < 0.05). Saline loading after ibuprofen again raised blood pressure by about 25 mmHg in the elderly only. The elderly group showed markedly increased sodium excretion during saline loading, but this was reduced by ibuprofen. Ibuprofen had no effect on SBP or sodium excretion in controls. Ageing appears to increase susceptibility to salt retention and hypertension from non-steroidal anti-inflammatory agents.      

Imaging of thoracic aortic dissection

Acute thoracic aortic dissection has a high mortality if untreated, so the diagnosis must be rapidly made if mortality is to be lowered significantly. Multiple imaging techniques are often used. This retrospective study from 1988 to 1993 assesses the usefulness in diagnosis of chest X-rays, computed tomography (CT) scanning, aortography, magnetic resonance imaging (MRI), trans-thoracic (TTE) and trans-oesophageal (TOE) echocardiography. Forty-two patients with a final clinical diagnosis of dissection were studied. The diagnosis was confirmed in 16 (13 at surgery and three at autopsy). Three died with dissection given as the only cause for death. Chest X-ray abnormalities were seen in all 19 patients with surgery or death from dissection, with a widened mediastinum and/or dilated aorta being present in 17. In the group of 16 patients with surgery or autopsy proof, CT scans found dissections in 9 of 12 patients studied and correctly classified the type in only five. Aortography was performed in five, with accurate depiction of dissection and type in all. TTE found dissections in three of eight patients imaged by this method. MRI and TOE were performed each on two patients, with accurate depiction of dissection and type in each. Because of the relatively low sensitivity of CT scanning in defining aortic dissections Westmead Hospital is currently assessing the use of TOE as the prime imaging modality prior to surgical intervention.     

Similarities in Skeletal Muscle Strength and Exercise Capacity Between Renal Transplant and Hemodialysis Patients

Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients. Aim of the study was to assess to what extent exercise capacity and skeletal muscle strength of RTx patients differ from HD patients and healthy controls and to elucidate potential determinants of exercise capacity in RTx patients. Exercise capacity, muscle strength, lean body mass (LBM) and physical activity level (PAL) were measured by cycle-ergometry, isokinetic dynamometry, DEXA and Baecke Questionnaire, respectively, in 35 RTx, 16 HD and 21 controls. VO2peak and muscle strength of the RTx patients were significantly lower compared to controls (p<0.01), but not different compared to HD patients. In RTx patients, strength (p<0.001), PAL (p=0.001) and age (p=0.045) were significant predictors of VO2peak. Muscle strength was related to LBM (p=0.001) and age (p=0.001), whereas gender (p<0.001) and renal function (p=0.01) turned out to be significant predictors of LBM. No effects of corticosteroids were observed. Exercise capacity and muscle strength seem equally reduced in RTx and HD patients compared to controls. In RTx patients, muscle strength and PAL are highly related to exercise capacity. Renal function appears to be a significant predictor of LBM, and through the LBM, of muscle strength and exercise capacity.     

Fiber optic probe for polarized reflectance spectroscopy in vivo: design and performance

We present the design and construction of a fiber optic probe for elastic light scattering spectroscopy in vivo with polarized excitation and polarization sensitive detection. The performance of the fiber probe is evaluated using a suspension of polystyrene spheres placed atop a diffusely scattering substrate, and it demonstrates that the size-dependent characteristics of the scatterers can be extracted in the presence of a highly diffusely scattering background using a linear combination of forward and backward Mie scattering components of the scatterers. Subsequently, Mie theory calculations are performed over a broad range of diagnostically relevant parameters of nuclei-mean diameter, size distribution, and relative refractive index-to understand how the polarized reflectance measurements with the fiber probe can be used to extract morphological information about epithelial tissue. Finally, the feasibility of in vivo measurements with the fiber optic based polarization sensitive light scattering spectroscopy is demonstrated.