John F. Schweiss

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.

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.

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.

Intraoperative autologous blood salvage with cardiac surgery: An analysis of five years' experience in more than 3,000 patients

STUDY OBJECTIVE To analyze intraoperative autologous salvage of shed mediastinal blood and subsequent transfusion in cardiac surgery. DESIGN Retrospective statistical analysis. SETTING University hospital. PATIENTS Three thousand twenty two patients undergoing cardiac surgery from 1984 to 1988. INTERVENTIONS A review of anesthesia and transfusion records of all patients who underwent intraoperative salvage of shed blood and autologous transfusion using the Sorenson Receptal Auto Transfusion System (ATS) with saline wash prior to reinfusion in cardiac surgery. MEASUREMENTS AND MAIN RESULTS The salvaged blood volume ranged from 36 to 2,795 ml, with a mean of 321 +/- 222 ml (SD). Eighteen percent of patients did not receive any homologous blood products during their hospitalization. Patients who received only salvaged autologous transfusion were younger, had higher preoperative hemoglobin and hematocrit values, had a larger body surface area, and had shorter surgeries compared with patients who received only homologous blood or both autologous and homologous blood. More blood products were given to patients who received salvaged autologous blood compared with those who did not. Patients who underwent normovolemic hemodilution prior to extracorporeal circulation with subsequent reinfusion received significantly fewer blood products. Ten preoperative and four intraoperative variables significantly influenced the salvaged volume. Previous cardiac surgery was the most significant preoperative variable, and repair of ventricular septal defect produced by myocardial ischemia was the most significant intraoperative variable. CONCLUSION Considering the average salvaged volume and its current autologous transfusion-related expense, autologous blood salvage is potentially an economic benefit. Perioperative blood conservation requires a considerable commitment from surgeons, anesthesiologists, perfusionists, and intensive care physicians to be effective.

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.

Late repair of bronchial rupture in a child by bronchial replantation

A 3-yr-old boy suffered blunt trauma to the anterior chest. Immediate treatment resulted in resolution of acute respiratory distress. Subsequent events led to the recognition of previous bronchial rupture six months later. Primary bronchial repair was not feasible and bronchial replantation onto the trachea was employed. An excellent early result was achieved.

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.

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.

TRACHEAL TUBE CUFF VOLUME CHANGES DURING EXTRACORPOREAL CIRCULATION

Changes in the volume of tracheal tube cuffs were examined during extracorporeal circulation to determine the influence of the composition of the inspired gases and of the gas within the cuff. The study was carried out on 90 patients who underwent coronary artery bypass grafting. When the cuff contains nitrous oxide at the start of extracorporeal circulation, the cuff volume decreases during bypass regardless of the composition of the inspired gases. When the cuff is filled with air or 100 per cent oxygen at the start of extracorporeal circulation and the inspired gas mixture consists of nitrous oxide and oxygen the cuff volume increases. When the cuff is deflated and then refilled with either room air or oxygen at the beginning of the extracorporeal circulation and the lungs are inflated with oxygen, the cuff volume change is minimal during bypass. This combination of gas prevents any undesirable change in the cuff volume. It appears desirable to monitor the tracheal tube cuff volume or pressure and to maintain a constant pressure and volume during bypass to prevent deflation and silent aspiration associated with cuff deflation, as well as to avoid mucosal damage due to excessive pressure in the cuff.RéSUMéLes changements de volume du ballonnet des tubes trachéaux ont été étudiés pendant la circulation extracorporelle pour déterminer les effets de la composition des gaz inspirés et des gaz du ballonnet. Cette étude a porté sur 90 patients qui subissaient un pontage aortocoronarien.Lorsque le ballonnet contenait du protoxyde d’azote au début de la circulation extracorporelle, le volume du ballonnet a diminué pendant le pontage quelque soit la composition de gaz inspiré. Lorsque le ballonnet est vérifié d’air ou d’oxygène, le volume du ballonnet est dégonflé et ensuite empli soit avec de l’air ou de l’oxygène au début de la circulation extracorporelle et que les poumons sont ventilés à l’oxygène, le changement de volume du ballonnet est minime pendant le pontage. Ce mélange de gaz prévient tout changement indesirable du volume du ballonnet. II semble désirable de monitoriser le volume ou la pression du ballonnet du tube trachéal et de maintenir un volume ou une pression constante pendant le pontage pour éviter la déplation et I’aspiration silencieuse associée à la déflation du ballonnet, aussi bien pour éviter d’endommager la muqueuse trachéale par pression excessive par le ballonnet.

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 Ringers solution with and without 5% dextrose) exposed to 300 foot candles of fluorescent light for72 hours after sodium nitroprusside was dissolved in each solution. The rates of the increase incyanide 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, theelectrolyte-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 Ringers solution with and without 5% dextrose. Solutions containing electrolytes are preferable to 5% dextrose for the dilution of sodium nitroprusside.