Robert L. Replogle

Thermodilution cardiac output: A critical analysis and review of the literature

Abstract A critical analysis of the thermodilution method of cardiac output determination has been presented. The factors determining cardiac output calculations have been discussed and specific sources of error have been analyzed. This method offers advantages of internal electrical calibration, use of physiologic fluid as indicator, minimal recirculation, lack of requirement for a withdrawal system, and a short interval between successive determinations. The method has compared favorably to other methods of cardiac output determination and is easily used in the modern clinical setting because of its technical simplicity and the availability of flow-directed balloon-tipped catheters with thermistors. Specific sources of error include factors influencing the temperature of the injectate bolus, the determination of initial baseline blood temperature, the integration of the time-temperature curve, the technique of injection, and the method of sampling. These errors depend both upon experimental technique and upon the internal calibrations and methods of curve integration as determined by the manufacturer. In general, the method can be used to accurately determine cardiac output when it is applied systematically and the sources of error are understood.

Combined application of heterologous collagen and fibrin sealant for liver injuries

Hemostasis in complex liver injuries remains a problem despite improvements in operative techniques including debridement, suturing or packing. To evaluate fibrin sealant (FS), a new biodegradable hemostatic agent in combination with porcine collagen for sealing of liver injuries, three series of experiments were performed in 132 rats. In series I, 18 rats had a 10-mm in diameter and 2-mm in depth punch defect to the left lateral lobe. In the FS group (n = 9), bleeding was treated by insertion of an FS-soaked piece of collagen of equal size which was firmly attached to a plastic disk with wire anchor. In the control group (n = 9), collagen alone was inserted. Fifteen minutes after the insertion the lobe was excised and pull-off experiments were performed with simultaneous script chart recording. There was a highly significant difference in the adhesion to the liver surface (85.6 +/- 7.1 in the FS group versus 24.8 +/- 2.6 g/cm2 in the control group, P less than 0.001). In series II, 42 anticoagulated rats (Coumadin, PT 27.5% +/- 1.3) with lobectomy or liver rupture were placed in three groups (n = 14). Group I was treated with FS, group II with FS and collagen, and group III with catgut sutures which served as controls. Fourteen days later 12 rats of group I, 13 of group II, and 7 of group III were alive yielding 85.7, 92.8, and 50% overall survival rates, P less than 0.05 groups I and II versus group III. In series III, 72 non-anticoagulated rats were treated identically to series II and examined morphologically at 1, 7, 28, and 56 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectrum of pulmonary sequestration: Association with anomalous pulmonary venous drainage in infants

SummaryPulmonary sequestration is a spectrum of related lesions, each of which may be absent or present: (1) bronchial sequestration of pulmonary parenchyma; (2) arterial supply from systemic circulation; (3) anomalous pulmonary venous drainage to the right atrium; (4) communications between bronchus and esophagus; (5) defects of diaphragm; (6) gross lung anomalies, such as horseshoe lungs or hypoplasia. Any combination of these primary lesions can occur in an individual patient. Diagnosis should be directed towards each component of the spectrum. Of special importance is the venous connection, as anomalous pulmonary venous drainage can involve not only the sequestered segment but the entire ipsilateral lung, making surgical therapy far more complex. Treatment of choice is surgical resection, associated, if needed, with rerouting of the pulmonary venous return.Classification of sequestration of the lung as intra- and extralobar is of secondary importance: these 2 groups do not represent lesions of different embryological significance.

Coronary artery aneurysms after angioplasty and atherectomy

Coronary artery aneurysm formation after percutaneous transluminal coronary angioplasty and directional coronary atherectomy is unusual. We report the case of a left anterior descending coronary artery aneurysm that formed in such a patient. The left anterior descending coronary artery was bypassed and the aneurysm was plicated with the aid of coronary angioscopy. The English-language medical literature on the topic of coronary artery aneurysms is reviewed.

Electrophysiologic abnormalities of children with ostium secundum atrial septal defect

Sinus node (SN) and atrioventricular node (AVN) function were evaluated in 49 patients with secundum type atrial septal defect (ASD). Automaticity and conduction system function were assessed by intracardiac recording of the AH and HV intervals at rest, corrected SN recovery time, sinoatrial conduction time, AVN refractory period and the ability of the AVN to conduct rapidly paced atrial beats to the ventricles. Electrophysiologic abnormalities were found in 41% of the 34 patients who were studied before surgery. However, no preoperative abnormalities were present in children younger than 2.5 years. If only children older than 2.5 years were analyzed, the incidence of conduction abnormalities was similar for the patients studied before operation (62%) and those studied after operation (71%). The size and ejection fractions of the right and left ventricles, the magnitude of shunt flow and the size of the ASD did not differ between the patients with and those without electrophysiologic abnormalities. AVN dysfunction was present in 40% of the patients who were studied after surgical repair. While this frequency was more than twice the preoperative incidence of AVN dysfunction, it was not statistically significant. The data suggest that patient age is the major factor that influences the presence of conduction system dysfunction in patients with ASD.

Use of fibrin sealant for reinforcing arterial anastomoses.

Despite improvements in needles, sutures, and technique, hemorrhage remains a problem in cardiovascular surgery. In this study conventional vascular suture lines and suture lines reinforced with fibrin sealant are compared for blood loss and burst strength. Bilateral femoral arteries in 20 dogs were divided at 50% of their circumference and repaired with six 6-0 polypropylene sutures. Ten animals were systemically heparinized (3 mg/kg), and 10 were not on anticoagulants. The right femoral artery anastomosis was treated with fibrin sealant in all animals, and the left suture line served as the control. Three minutes after initiation of the sealing procedure, blood flow was reinstituted in both femoral arteries. After 3 minutes a significant difference in blood loss between the conventional suture technique and fibrin-reinforced anastomoses was noted in both heparinized (12.1 +/- 2.79 vs. 0.13 +/- 0.06 ml/min; p less than 0.01) and nonheparinized dogs (8.45 +/- 1.37 vs. 0.20 +/- 0.08 ml/min; p less than 0.001). After 30 minutes volume inflow and pressure catheters were inserted into snared compartments encompassing the femoral artery anastomosis. Continuous pressure recordings during volume loading with normal saline solution demonstrated increased bursting pressures of the fibrin-sealed suture lines in both the heparinized (317.5 +/- 13.18 vs. 135 +/- 23.17 mm Hg; p less than 0.001) and nonheparinized animals (474.5 +/- 26.82 vs. 311 +/- 29.31 mm Hg; p less than 0.001). Histologic examination revealed no fibrosis or foreign body reaction and complete resorption of the fibrin sealant within 3 weeks. Fibrin sealant, a powerful hemostatic agent produced from human donors not suffering from hepatitis, decreases blood loss and strengthens suture lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Reperfusion of skeletal muscle after warm ischemia.

The effect of 2 to 10 hours of tourniquet ischemia on the microcirculation of the tenuissimus muscle in 29 cats was studied by in vivo microscopy and electron microscopy. After release of the tourniquet there was immediate reperfusion and hyperemia in all muscles. Arterioles of 20 µm increased in diameter by 50% and venules of 35 µm by 30%. If the ischemia had lasted for 8 hours or more, reocclusion of flow occurred after 3 to 55 minutes. Platelet thromboembolism, sticking of leukocytes, and red cell aggregation seem to cause the occlusion.

Aberrant left pulmonary artery (pulmonary artery sling): Successful repair and 24 year follow-up report

A case of anomalous left pulmonary artery arising from the right and coursing behind the trachea and anterior to the esophagus (pulmonary artery sling) is reported. The therapy currently advocated for this disorder is ligation of the anomalous vessel and performance of a left pulmonary to main pulmonary arterial anastomosis anterior to the trachea. A median sternotomy incision allows total mobilization of the anomalous vessel, minimizes respiratory embarrassment and aids in performance of the anastomosis. In the present case, a postoperative pulmonary angiogram revealed a patent left pulmonary artery, the second reported instance of such patency. The first successful repair of pulmonary artery sling was reported by Potts and colleagues in 1954. After a 24 year follow-up period their patient has normal exercise tolerance and no perfusion to the left lung is evident on ventilation-perfusion scan.

The Prosthetic (Teflon) Central Aortopulmonary Shunt for Cyanotic Infants Less Than Three Weeks Old: Results and Long-Term Follow-up

The expanded microporous polytetrafluoroethylene (PTFE) 4 mm vascular prosthesis has been used to create a central aortopulmonary shunt in 20 critically ill infants less than 3 weeks old. The infants ranged from 1 to 18 days old (5.25 days), and from 1.5 to 4.0 kg (2.9 kg). Conduit length ranged from 2 to 6 cm (4 cm). Sixteen patients had atresia of the tricuspid or pulmonary valve. There were 6 early deaths (30%), only 1 of which was shunt related. The mean preoperative arterial oxygen saturation was 62% (range, 33 to 80%), and mean postoperative saturation was 87% (range, 78 to 90%). There were 5 late deaths, 1 probably caused by shunt failure. Nine long-term survivors have done well. Follow-up ranges from 1 to 36 months (18 months). Factors influencing conduit function are length, technical considerations, and pulmonary vascular resistance. Late restudy in 5 of 9 survivors confirms patency and demonstrates bidirectional pulmonary blood flow. Since PTFE shunt flow capability is fixed, the infant may require repair or a second shunt within 24 months of the initial procedure.

Pathophysiology of acute and chronic cardiac failure

Cardiac (or myocardial) failure, a major health problem, can be defined using physiologic criteria that consider the adequacy of O2 delivery relative to the bodys O2 requirements. In clinical terms, cardiac failure may be described in terms of its chronicity or the extent to which signs and symptoms of right- versus left-sided heart failure are dominant. Congestive heart failure is a clinical syndrome that consists of a constellation of signs and symptoms that arise from congested organs and hypoperfused tissues. Acute cardiac failure occurs because of a decrease in myocardial contractility that can be offset by the Frank-Starling mechanism. In chronic cardiac failure dilatation and myocardial hypertrophy serve to restore ventricular function. Other compensatory responses that are invoked include a salt avid kidney, which mediates an expansion of the intravascular space, and the activation of the adrenergic nervous and renin-angiotensin-aldosterone systems and an increase in circulating arginine vasopressin. The management of acute and chronic cardiac failure can be derived from an understanding of the pathophysiologic mechanisms responsible for their appearance and include improving cardiac performance, as well as the distribution of systemic blood flow to tissues based on physiologic priorities and moment to moment variations in O2 requirements.