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Biomedical subjects

S R Powers

Publications and source records attributed to S R Powers.

At least 19 recordsLinked to original sources
PubMed1983

Lung vascular permeability after reversal of fibronectin deficiency in septic sheep. Correlation with patient studies.

Plasma fibronectin deficiency and opsonic dysfunction exist in critically ill septic surgical, trauma, and burn patients with multiple organ failure. Fibronectin deficiency can be reversed by infusion of fresh plasma cryoprecipitate. The influence of therapy with human cryoprecipitate on lung vascular permeability in septic sheep with plasma fibronectin deficiency following surgery was evaluated. Additionally, selected studies on pulmonary function in septic surgical and trauma patients after infusion of plasma cryoprecipitate were completed. In patients, ventilation-perfusion balance appeared to improve as measured by the multiple inert gas elimination technique. With the lung lymph fistula preparation in fibronectin deficient sheep, infusion of human plasma cryoprecipitate (10 units; 250 ml) delayed the onset and minimized the increase in lung vascular permeability during postoperative Pseudomonas sepsis (5 X 10(9) bacteria, I.V.; 5 X 10(10) bacteria, I.P.). For example, in a first group of sheep, the transvascular protein clearance (TPC) at 2 hrs in septic sheep (n = 4) treated with only saline (volume control) was 20.1 +/- 3.1 ml/hr, compared to 11.23 +/- 0.83 ml/hr in the sheep (n =a 4) treated with fibronectin-rich cryoprecipitate (p less than 0.05). In a second group of sheep, cryoprecipitate depleted of fibronectin by affinity chromatography was used as the control solution. It also did not manifest this protective effect with respect to lung vascular permeability. Thus, at 2 hrs the lymph flow (Qlym) was 30.2 ml/hr and the transvascular protein clearance (TPC) was 18.0 ml/hr in septic sheep given fibronectin-deficient cryoprecipitate. In contrast, in the fibronectin-rich cryoprecipitate treated sheep, the Qlym was 14.8 ml/hr and the TPC was 8.12 ml/hr. It is suggested that fibronectin may influence lung vascular integrity during sepsis following surgery and trauma.

Adolescent↗
PubMed1981

Intra-arterial tissue adhesive for medical splenectomy in humans.

Bucrylate (isobutyl 2-cyanoacrylate) was used for the transcatheter embolization of the splenic artery in 4 patients with bleeding gastric varices secondary to splenic vein thrombosis, 3 patients with symptoms of hypersplenism, and 8 patients with bleeding esophageal varices secondary to portal hypertension. The splenic artery was completely occluded in 13 patients and partially occluded in 2. In all but one of the patients, functioning splenic tissue was preserved and no abscess developed. Medical splenectomy with Bucrylate appears to be a safe and effective method for treating bleeding gastric varices secondary to splenic vein thrombosis, and it can alleviate symptoms of hypersplenism. Its role in controlling bleeding from esophageal varices in patients with generalized portal hypertension is worth further study.

Adhesives↗
PubMed1981

Ventilation-perfusion relationships with high cardiac output in lobar atelectasis.

Pulmonary gas exchange was evaluated in 10 anesthetized mechanically ventilated dogs. Cardiac output (QT) was increased approximately 50% by opening peripheral arteriovenous fistulas. With both lungs ventilated, increasing QT increased mixed venous O2 both pressure (PO2) and pulmonary arterial pressure, but neither shunt fraction nor the distribution of ventilation-perfusion was consistently altered. During left lung atelectasis, increasing QT again increased mixed venous PO2 and pulmonary arterial pressure, but two different responses in shunt-like perfusion were measured. In four dogs, left lung atelectasis caused a shunt fraction of 46 +/- 6% that was not changed by high QT (P greater than 0.05). In six dogs, atelectasis caused a shunt fraction of 24 +/- 3% during normal QT that increased to 42 +/- 2% during high QT (P less than 0.001). Dogs whose shunt fraction during atelectasis was high and unchanged by QT had lower arterial pH (7.24 +/- 0.03) than dogs whose shunt fraction was initially lower and was increased with QT (7.36 +/- 0.02) (P less than 0.01). We conclude that increased QT can worsen shunt flow during lobar atelectasis when hypoxic vasoconstriction has been effective in limiting perfusion to the collapsed region at normal levels of QT.

Animals↗
PubMed1981

Effects of dopamine, ethanol, and mannitol on cardiopulmonary function in patients with adult respiratory distress syndrome.

Dopamine, ethanol, and mannitol were investigated to determine if they could increase pulmonary blood flow and oxygen delivery without significantly increasing intrapulmonary shunt. These drugs were studied in adult patients with respiratory distress following trauma, operation, or sepsis. Intravascular pressure, cardiac output, oxygen consumption and delivery, and limb blood flow and peripheral oxygen delivery were measured in all patients. Hypotensive patients received dopamine in incremental doses of 2 mu g/kg/min until either mean arterial pressure increased 15 mm Hg or heart rate increased by more than 15 beats/min. Ethanol was given as 10% ethanol in 5% dextrose at 2 ml/kg/hr. Mannitol was given as 25 gm of a 25% solution in a single bolus followed by infusion of 8 to 25 gm of 20% solution (mean 10 +/- 2 gm) as a continuous intravenous drip over 1 hour. No drug produced a significant change in intrapulmonary shunt. Ethanol produced significant (p less than 0.05) increases in cardiac index, heart rate, oxygen consumption, and oxygen delivery. Dopamine significantly decreased pulmonary vascular resistance while increasing systemic blood pressure. Visceral blood flow apparently increased while the peripheral vascular response to ischemia remained intact. Mannitol increased oxygen delivery and consumption in both the total body and limb. Thus in patients with adult respiratory distress syndrome (ARDS), increases in pulmonary blood flow can be achieved with several distinct pharmacologic agents without significant increases in intrapulmonary shunt. These increases in flow are generally accompanied by increases in oxygen delivery without increased pulmonary vascular resistance.

Adolescent↗
PubMed1980

Chronic venosus obstruction as a factor in the early failure of bypass grafts in the leg.

It is suggested that the early failure of bypass grafts in patients with clinical evidence of venous hypertension is a result of increased resistance caused by venous obstruction. The importance of using autogenous vein grafts in such cases is emphasized. One should accept the possibility that arterial reconstruction may result in a less successful outcome in patients with chronic venous disease.

Bioprosthesis↗
PubMed1980

Detrimental effects of removing end-expiratory pressure prior to endotracheal extubation.

Patients recovering from acute respiratory insufficiency are usually not extubated until they can ventilate adequately while breathing spontaneously at ambient end-expiratory pressure (T-tube). It is hypothesized that this period of T-tube breathing might be detrimental to gas exchange since the endotracheal tube abolishes the expiratory retard produced by the glottis and thereby inhibits the patient's ability to maintain adequate functional residual capacity (FRC). To test this hypothesis, pulmonary function of 17 patients was compared during T-tube breathing and Continuous Positive Airway Pressure (CPAP) and after extubation. Intrapulmonary shunt was higher (p less than 0.05) and arterial PO2 and FRC were lower (p less than 0.05) during T-tube breathing than during CPAP or after extubation. In contrast, shunt, PaO2 and FRC were similar during CPAP and after extubation. Furthermore, after extubation there was an increase (p less than 0.05) in mean expiratory airway pressure as compared to T-tube breathing. A comparison of patients extubated from T-tube with patients extubated from CPAP showed no difference in postextubation shunt, PaO2 or FRC. These data suggest that endotracheal intubation should be accompanied by low levels of CPAP and that patients should be extubated directly from CPAP. The practice of placing patients in T-tube prior to extubation should be abandoned as unnecessary and potentially harmful.

Adult↗
PubMed1980

Bucrylate embolization of abdominal aortic aneurysms: an adjunct to nonresective therapy.

Abdominal aneurysmectomy in a patient with an abdominal aortic aneurysm who has cardiac, renal, or pulmonary disease is associated with a high surgical mortality. Fifteen such patients underwent nonresective therapy of an abdominal aortic aneurysm consisting of an axillobifemoral bypass graft which maintains blood flow to the lower extremities. At the time of the graft the iliac vessels were ligated, occluding the outflow tract from the aneurysm, and resulting in retrograde thrombosis. In three of the 15 patients, however, the aneurysm remained patent because of patency of the hypogastric arteries. The outflow tract in these three patients was occluded by a transcatheter injection of Bucrylate, a tissue adhesive, into the distal abdominal aorta and iliac vessels. Bucrylate embolization is a potentially useful adjunct to nonresective treatment of abdominal aortic aneurysms.

Aged↗
PubMed1980

The sizing of fibres using optical scattering.

The light scattering pattern from absorbing cylinders has been shown to be adequately described by Fraunhofer diffraction for cylinders with diameters as small as 4 micrometers for light of wavelength 632.8 nm. A simple inversion procedure based on a Fourier transform of the scattering pattern may be used to obtain the size distribution of fibre widths. For fibres of diameter less than 4 micrometers the same inversion procedure may be used when an electron micrograph of the fibres becomes the scattering object. The size distribution for aligned and unaligned fibres may be obtained directly, and no initial calibration is required.

Asbestos↗
PubMed1979

Lung volume and blood oxygenation after intermittent positive pressure breathing.

Functional residual capacity (FRC) was measured in 12 postoperative patients and in one preoperative patient before and after they received intermittent positive pressure breathing (IPPB) with room air for ten minutes at a peak delivered pressure of 15 cm H2O. Ten patients had a normal or low pretreatment FRC. After cessation of IPPB, the mean FRC decreased further. Arterial oxygen tensions, measured in 11 of the 13 patients, decreased in all 11 from a pretreatment mean of 67.8 +/- 4.3 mm Hg to an immediate posttreatment mean of 57.7 +/- 4.2 mm Hg. In five patients repeated arterial blood gases were measured. At 30 minutes, their arterial oxygen tensions had returned to the pre-IPPB values. This study demonstrates that the routine use of IPPB in postoperative patients accentuates preexisting hypoxia and, therefore, must be used with caution.

Adolescent↗
PubMed1979

Ventilation-perfusion imbalance after head trauma.

To investigate the role of ventilation-perfusion (VA/Q) imbalance in the hypoxemia observed after head injury, 5 male subjects (17 to 26 years of age) with isolated head trauma and subsequent hypoxemia were studied. Disturbances of ventilation and perfusion were assessed using the steady-state elimination of six inert gases of different solubilities. Paired studies were conducted during mechanical ventilation with a volume-cycled ventilator and during spontaneous ventilation. Distributions recovered from studies of spontaneous ventilation show a mode of ventilation and perfusion near a VA/Q of 1.0. In addition, 41% of the cardiac output was distributed to a second population of lung units with low VA/Q (less than 0.1) and shunt. During mechanical ventilation, perfusion to these regions of low VA/Q decreased to 21% of the cardiac output, whereas shunt fraction was unchanged. This was associated with a marked broadening of the VA/Q mode near 1.0, relative to the studies during spontaneous ventilation. Mean functional residual capacity during mechanical ventilation was not different from that during spontaneous ventilation. These results suggest that head injury can lead to hypoxemia through a failure of VA/Q regulatory mechanisms.

Adolescent↗