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Biomedical subjects

J F Schweiss

Publications and source records attributed to J F Schweiss.

At least 19 recordsLinked to original sources
PubMed1995

Relation between pulmonary venous flow and pulmonary wedge pressure: influence of cardiac output.

Multiple factors affect the systolic and diastolic components of pulmonary venous flow. It has been suggested that left ventricular function might influence the effects of filling pressures on indexes of pulmonary venous flow. The present study was designed to evaluate the effect of the pulmonary wedge pressures, left ventricular function, and cardiac output on the pulmonary vein flow pattern. Forty-five patients undergoing cardiac surgery were included in this study. Pulmonary venous flow and mitral flow variables were obtained by transesophageal echocardiography with hemodynamic variables obtained simultaneously. In the total group, there was no consistent relation between the pulmonary venous flow or the mitral flow parameters and the capillary wedge pressures. When patients were grouped according to normal (> 2.2 L/min/m2) or low (< 2.2 L/min/m2) cardiac index, a significant and positive relation was found between the systolic component of the pulmonary venous flow and the pulmonary wedge pressure in patients with normal cardiac index (r = 0.69; p = 0.003). Conversely, in patients with low cardiac index there was also a significant although negative correlation between the systolic velocity integral and the pulmonary wedge pressure (r = -0.58; p < 0.001). In conclusion, the systolic component of the pulmonary venous flow correlates closely and significantly with the capillary wedge pressures. The direction of this relation depends to a large extent on the total cardiac output and to a lesser extent on the left ventricular systolic function as assessed by the ejection fraction.

Adult↗
PubMed1992

A comparison of two epidural alpha 2-agonists, guanfacine and clonidine, in regard to duration of antinociception, and ventilatory and hemodynamic effects in goats.

Epidural clonidine produces analgesia in humans with acute and chronic pain. Its use is limited because of short-lasting analgesia, hemodynamic depression, sedation, and respiratory depression. Intrathecal guanfacine has a longer duration of action than intrathecal clonidine. The present study compares these two drugs administered epidurally. Pulmonary artery, carotid artery, and epidural catheters were inserted into five goats. Each animal received guanfacine 5 mg/10 mL, clonidine 750 micrograms/10 mL, or a 10-mL saline control solution on separate occasions. Antinociception (tested via a point pressure stimulation device), arterial blood pressure, heart rate, cardiac output, pulmonary capillary wedge pressure, and arterial and mixed venous blood gases were measured every 30 min for 8 h. Guanfacine produced a longer duration of antinociception (guanfacine = 8 h vs clonidine = 5.5 h). Increases in PaCO2 were more pronounced in the clonidine group. There were no marked hemodynamic differences between the two drugs. Pretreatment with epidural idazoxan, an alpha 2-antagonist, blocked the antinociceptive effects of guanfacine. Because of a longer duration of action and less respiratory depression, epidural guanfacine may be superior for postoperative analgesia and chronic pain syndromes.

Animals↗
PubMed1991

In vitro reappraisal of the pulmonary artery catheter balloon volume-pressure relationship: comparison of four different catheters.

The most serious risk of the use of the flow-directed pulmonary artery (PA) catheter is PA rupture due to high balloon inflation pressure of the catheter. Previously reported measurements of PA catheter intra-balloon pressure and volume during balloon inflation were performed mostly in a static fashion, that is, measurements were performed after a certain volume of air had been injected into the balloon. In this study, simultaneous measurements of pressure and volume, in addition to a static study, were performed in vitro using four PA catheters (Abbott Opticath, Arrow Hands-Off, Baxter Edwards and Spectramed). The peak intra-balloon pressure was recorded immediately before loss of resistance was felt in the inflating syringe. Contrary to previously reported studies, the peak intra-balloon pressure was not the pressure exerted on the pulmonary artery wall unless the tip of the catheter was already in the peripheral pulmonary artery. The loss of resistance volume which was constant for each catheter could be used reliably as an indicator of instantaneous balloon inflation. The slower the rate of injection, the lower were the peak pressure and the injection volume at the peak pressure. The Abbott, Edwards and Spectramed catheters had similar characteristics of inflation volume and intra-balloon pressure. The Arrow catheter had higher balloon opening and plateau pressures, and a smaller balloon volume compared with the other three catheters.

Analysis of Variance↗
PubMed1990

Measurement of blood cyanide with a microdiffusion method and an ion-specific electrode.

The use of a cyanide ion-specific electrode in combination with the Conway microdiffusion method was modified for the measurement of cyanide concentration in human red blood cells and plasma. With our modified method, the optimal pH of cyanide isolation from red blood cells and plasma was investigated. Cyanide recovery from red blood cells increased with decreasing pH. The maximal recovery of 96.9 +/- 2.6% was obtained at a pH of less than 1. Cyanide recovery from plasma, however, peaked at a pH between 7 and 8, and further changes in pH reduced the recovery rate. The maximal recovery rate from plasma was 74.1 +/- 1.5%. In previous studies, cyanide isolations from both plasma and red blood cells were carried out at a pH of less than 1. This study shows that cyanide isolation from plasma should be performed at a pH between 7 and 8.

Blood Chemical Analysis↗
PubMed1989

Triple knotting of a central venous catheter.

A case of unusual triple knotting of a central venous catheter inserted through the left basilic vein is reported. The catheter with intact triple knots could be withdrawn without an invasive maneuver. A possible cause of triple knotting was discussed in regard to the anatomic configuration of the central veins. This case emphasizes that a central venous catheter should not be advanced if resistance is encountered.

Adult↗
PubMed1988

In vitro cyanide release from sodium nitroprusside in various intravenous solutions.

The concentration of cyanide, a toxic metabolite of sodium nitroprusside, in solutions other than 5% dextrose in water, has not been reported. In this study, cyanide ion levels were measured by a cyanide ion-specific electrode in 250 ml of six different intravenous solutions (5% dextrose in water, 10% dextrose in water, distilled water, 0.9% sodium chloride, and lactated Ringer's solution with and without 5% dextrose) exposed to 300 foot candles of fluorescent light for 72 hours after sodium nitroprusside was dissolved in each solution. The rates of the increase in cyanide ion concentration in all six solutions were fairly constant between 4 and 24 hours. At 24 hours, there were no statistically significant differences in cyanide ion concentration among the six solutions. After 24 hours, the rate of the increase in cyanide ion concentration in the electrolyte solutions decreased more than that in the nonelectrolyte solutions. At 72 hours, the electrolyte-containing solutions had statistically significant lower mean cyanide ion concentrations than 5% dextrose, often the recommended diluent for sodium nitroprusside. There was no difference in mean cyanide ion concentration between lactated Ringer's solution with and without 5% dextrose. Solutions containing electrolytes are preferable to 5% dextrose for the dilution of sodium nitroprusside.

Cyanides↗
PubMed1987

In vitro cyanide release from sodium nitroprusside.

In vitro release of cyanide from sodium nitroprusside in 5% dextrose in water solution following exposure or non-exposure to fluorescent light (500 ft candles or 791 microwatt per square cm [muWcm-2]), was measured by a cyanide-specific ion electrode at 4, 8, 24, 48, and 72 h. The cyanide concentrations were significantly increased at 24 h in the light-exposed solution. In this group, 100% of the cyanide was released from sodium nitroprusside at 72 h exposure to light. However, cyanide concentrations showed no significant changes for 72 h in the light-protected solutions, which were either exposed to 500 foot candles fluorescent light or stored in a dark room. Less than 2.5% of the cyanide was released from sodium nitroprusside at 72 h in both of the light-protected groups. No significant differences in cyanide concentrations were observed at 8 h among the exposed or non-exposed solutions. After 24 h of exposure, the cyanide concentrations in the exposed group were significantly higher than those of the two light-protected solutions. However, there were no significant differences between the cyanide concentration in the light-protected solutions. These results substantiate the safety of sodium nitroprusside solution for 24 h if the sodium nitroprusside containing solutions are properly protected from light. An additional study performed showed that a significant amount of cyanide released from sodium nitroprusside was adsorbed to the surface of polyvinylchloride.

Cyanides↗
PubMed1987

Mixed venous hemoglobin saturation: theory and application.

SvO2 measurement by reflectance oximetry incorporated into a thermodilution catheter is a reliable method of assessing the adequacy of oxygen delivery and is currently the best method of continuously monitoring oxygen supply-demand relationships. The SvO2 measurement continuously monitors the tissue status of oxygenation. It is an early warning indicator of detrimental changes in supply and demand and is an on-line tool in guiding therapeutic management and evaluating the effectiveness of interventions. SvO2 monitoring is of value in the critically ill cardiac and general surgical patients, not only during the surgical intervention but also in the postoperative period when managing derangements of ventilation and circulation. In our experience, continuous surveillance of the SvO2 currently is the best rapidly responsive indicator of cardiopulmonary function and oxygen transport.

Hemoglobins↗
PubMed1985

Repair of aortic coarctation in infants: experience with an intraluminal shunt.

From 1962 to mid-1984, 63 infants underwent coarctation repair. Cardiac defects were present in 46 (73%). Repair was by subclavian aortoplasty in 35 patients, resection and end-to-end anastomosis in 19, and other techniques in 6. Three patients died before the repair was completed. In 15 patients, an intraluminal shunt was used during subclavian aortoplasty. Prostaglandin E1 (PGE1) was infused in 9 patients. Early (thirty-day) mortality was 16% (10 patients): 4 patients who underwent end-to-end anastomosis; 3 during attempted end-to-end anastomosis; 2 who received bypass grafts; and 1 who had subclavian aortoplasty without a shunt. None of the 15 patients who had subclavian aortoplasty with a shunt died. There were no early deaths among the last 25 patients seen. One patient who underwent subclavian aortoplasty without a shunt is paraplegic. There were 10 late deaths among the 53 patients followed from 1 month to 12 years (mean, 3 years). Arm-leg pressure gradients of 20 mm Hg or greater were found in 4 of the patients who had end-to-end anastomosis but not in any of the patients who had subclavian aortoplasty. Improved results of coarctation repair in infants in this study were attributed to PGE1, subclavian aortoplasty, and use of an intraluminal shunt.

Acidosis↗
PubMed1985

Maximum infusion rates and CVP accuracy during high-flow delivery through multilumen catheters.

Flow rates and pressure recording accuracy were compared for Argyle 14-, 16-, and 18-ga double-lumen and Edwards 7-Fr triple-lumen CVP catheters. Physiologic saline solution was pressure-infused into dogs through one lumen and CVP was measured via the other lumen. CVP accuracy was unaltered by simultaneous rapid infusion in either the double-lumen or triple-lumen catheters. In a separate in vitro experiment, physiologic saline and blood were pressurized at 100 to 400 mm Hg and infused through each port, and volume delivery per minute was measured. Only the 14-ga double-lumen catheter was adequate for the administration of a large amount of crystalloid solution. However, it was not large enough to permit the rapid infusion of blood. On the other hand, large volumes of both crystalloid and whole blood could be delivered through the 7-Fr triple-lumen catheter.

Animals↗
PubMed1983

Temperature dependent release of cyanide from sodium nitroprusside.

The effect of temperature on the release of cyanide from sodium nitroprusside (SNP), a potent vasodilating drug, was studied in vitro. It was observed that higher temperatures accelerate the degradation rate of SNP and facilitate the formation of cyanmethemoglobin in blood. The results indicate that hypothermia which is often used in combination with SNP may reduce the incidence of cyanide toxicity by slowing the degradation of SNP.

Body Temperature↗
PubMed1983

Failure of droperidol and ketamine to influence cerebrospinal fluid production in the dog.

Using the ventriculo-cisternal perfusion method, the effects of droperidol and ketamine hydrochloride on cerebrospinal fluid (CSF) production were studied in dogs. Neither droperidol (0.25 mg/kg, IV) nor ketamine (3 mg/kg, IV) caused a statistically significant change in CSF production rate. Positive correlation between CSF production and corresponding cerebral perfusion pressure (CPP) was observed in the ketamine study, whose unfavorable effect on neurosurgical anaesthesia would be obvious. On the other hand droperidol (0.25 mg/kg, IV) tended to decrease CSF production. Droperidol alone or in combination with other analgesics such as fentanyl as currently used in neurosurgical anaesthesia appears to be an appropriate choice in patients with increased intracranial pressure.

Anesthesia, General↗
PubMed1982

Excessive blood loss during operation in the patient treated with propylthiouracil.

A case of bleeding during operation due to propylthiouracil-induced thrombocytopenia is reported. A 55 year old male who had been treated with propylthiouracil for two months before operation underwent otherwise uneventful cervical laminectomy. Perioperatively he was transfused seven units of whole blood, two units of packed red cells, six units of platelets and two units of fresh frozen plasma for the estimated blood loss of 5500 ml. The patient underwent thyroidectomy without incident 45 days after withdrawal from propylthiouracil. The value of the preoperative coagulation studies of the patient treated with propylthiouracil is discussed.

Hemorrhage↗