Venoarterial bypass: a technique for spinal cord protection.

In the present study, we examined the effects of various levels of oxygen tension on spinal cord blood flow while using somatosensory evoked potentials to monitor spinal cord sensory function during hypoxia. In this experiment, six adult, mongrel dogs were heparinized and placed on right atrial-femoral artery bypass with an oxygenator in the bypass circuit. The aorta was cross-clamped proximal to the left subclavian artery, and bypass flow and fluid balance were adjusted so as to maintain a distal aortic perfusion pressure of greater than 80 mm Hg. Oxygen flow to the oxygenator was lowered by graded decrements to provide decreasing levels of oxygen tension, which ultimately approached pure venoarterial bypass. Each successive oxygen level was maintained for 30 minutes. Spinal cord blood flow was measured with radioactive microspheres, and latency and amplitude of somatosomatic evolved potentials were continuously monitored. The somatosensory evolved potential signal was invariably present as long as the distal aortic pressure was greater than 80 mm Hg; there were several transient hypotensive episodes (less than 5 minutes), which were accompanied by reversible loss of somatosensory evolved potentials. The spinal cord blood flow increased from 13.6 to 119.7 ml/100 gm/min as the distal oxygen tension fell to a mean value of 30 mm Hg, while latency of somatosensory evolved potentials increased 19.3% and amplitude decreased 43.3%. These results suggest the following conclusions: (1) In response to hypoxia, spinal cord blood flow dramatically increases and somatosensory evolved potentials deteriorate (increase in latency and decrease in amplitude). (2) However, during prolonged hypoxia, spinal cord sensory function can be maintained by sufficiently high flow rates and perfusion pressures. (3) Somatosensory evolved potentials can be used to monitor continuously spinal cord sensory function under these conditions.

Adjunctive left ventricular unloading during myocardial reperfusion plays a major role in minimizing myocardial infarct size.

Although prompt institution of reperfusion following coronary artery occlusion has been shown to limit myocardial infarct size, significant "reperfusion injury" may result. We investigated in a canine model whether maintenance of the left ventricle in an unloaded state during the initial reperfusion period following acute myocardial ischemia would result in greater limitation of infarct size or modify the development of reperfusion injury. Group I (control, n = 6) underwent 6 hours of occlusion of the left anterior descending coronary artery without further intervention. In both Group II (n = 6) and Group III (n = 6), the snare was released after 2 hours and hearts were reperfused for 4 hours. In Group III only, the left ventricle was maintained in an unloaded state throughout the entire reperfusion interval via pulsatile left atrial-femoral artery bypass. The results showed that reperfusion of the left ventricle in an unloaded state resulted in significantly improved limitation of both infarct size (area of infarct/area at risk = 16.6% for Group III versus 72.0% for Group I and 55.4% for Group II, p less than 0.001) and area of microvascular damage (area of microvascular damage/area at risk = 4.8% for Group III versus 30.6% for Group II, p less than 0.001). These results indicate that although myocardial reperfusion of the type provided by thrombolysis and/or angioplasty techniques does result in limitation of infarct size when compared to no reperfusion, this limitation is not optimal unless the left ventricle is unloaded during the initial reperfusion period.

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. III. Intraoperative identification of vessels critical to spinal cord blood supply.

Somatosensory evoked potentials were used to locate intercostal arteries critical to spinal cord blood flow in nine dogs. To mimic a clinical situation, the proximal descending thoracic aorta (left subclavian artery to T7) was excluded with cross-clamps, and partial pulsatile left atrial-femoral artery bypass was instituted to maintain distal aortic pressure at 100 mm Hg. Progressively lower aortic segments were excluded (T7-10, T10-L1, L1-3, L3-6, L6-7) until loss of somatosensory evolved potentials occurred. Spinal cord blood flow measurements at the time of evoked potential loss revealed significant ischemia (p less than 0.02 versus baseline) in the excluded segment in seven animals but normal spinal cord blood flow in the remainder of the cord. Upon reperfusion, significant reactive hyperemia (p less than 0.02) was noted only in previously ischemic cord segments. Two animals exhibited no change in somatosensory evoked potentials or spinal cord blood flow despite exclusion of the entire thoracoabdominal aorta, presumably as a result of spinal collaterals. Loss of somatosensory evoked potentials despite adequate distal perfusion indicates that critical intercostal vessels have been excluded from systemic and bypass circulations. Use of evoked potential measurements in both experimental and clinical situations provides a means for assessing adequacy of spinal cord blood flow during cross-clamping and can alert the surgeon to the need for reimplantation of critical intercostal arteries during surgical resection of the thoracoabdominal aorta.

Superiority of the University of Wisconsin solution over simple crystalloid for extended heart preservation. A study of left ventricular pressure-volume relationship.

To compare the effects of the University of Wisconsin solution with those of an extracellular crystalloid solution, Krebs-Ringer bicarbonate, as cardiac preservation media, we studied 35 adult dogs in an isolated heart preparation. Four groups of seven hearts were preserved in University of Wisconsin solution for 6 or 12 hours or in Krebs-Ringer bicarbonate solution for 6 or 12 hours. An additional group of seven hearts with no ischemia was used for a control group. In the four preservation groups, hearts were arrested by electrolyte solution (Normosol with potassium chloride, 20 mEq/L, added, 4 degrees C), flushed with 200 ml of the preservation solution, and then stored in the same solution at 1 degree to 2 degrees C. The hearts were mounted on an isolated heart preparation equipped with a computer-controlled servo-pump system that used a mock arterial system to modulate the aortic input impedance presented to the left ventricle. Left ventricular pressure-volume loops were measured on-line for 2 hours of reperfusion with autologous warm oxygenated blood. Elastance was derived from the end-systolic pressure-volume relationship, and diastolic compliance was derived from the end-diastolic pressure-volume relationship. The total left ventricular performance was assessed by the preload recruitable stroke work area, the slope, and its x-intercept, all of which derived from the stroke work (pressure-volume area)-end-diastolic volume relationship. Extended global ischemia had more deleterious effects on the end-diastolic than the end-systolic pressure-volume relationship. In confirmation with other studies, elastance did not accurately reflect the level of ventricular contractile dysfunction because of the significant amount of diastolic dysfunction. The preservation of myocardial systolic and diastolic functions, as demonstrated by the preload recruitable stroke work area and diastolic compliance, was better in the University of Wisconsin solution groups than in the Krebs-Ringer bicarbonate solution groups after 6 and 12 hours of preservation. In addition, 6 hours of preservation with University of Wisconsin solution maintained normal systolic and diastolic functions as compared with those of the control group. Preservation with University of Wisconsin solution prevented any myocardial edema formation; by contrast, this was significantly increased after 12 hours in Krebs-Ringer bicarbonate solution. Groups preserved with University of Wisconsin solution had less reperfusion injury as evidenced by the release of coronary sinus creatine kinase during reperfusion; they also had improved oxygen use during reperfusion.(ABSTRACT TRUNCATED AT 400 WORDS)

Time course of effective interventional left heart assist for limitation of evolving myocardial infarction.

Previous work has shown that if pulsatile left atrial-femoral artery bypass is instituted after occlusion of the left anterior descending coronary artery for from 15 minutes to 2 hours, it can significantly limit the size of the infarct resulting 4 hours later. This study investigated whether pulsatile left atrial-femoral artery bypass begun after more clinically pertinent periods of initial ischemia can still significantly limit infarct expansion. After baseline measurements of hemodynamics, tension-time index, and regional myocardial blood flow in 73 open-chest, adult dogs, the left anterior descending coronary artery was ligated for 15 minutes or 1, 2, 4, or 6 hours of unprotected ischemia. In the five control groups, the initial ischemic period was merely extended for another 4 hours. In the five experimental groups, the animals were placed on pulsatile left atrial-femoral artery bypass for another 4 hours after the initial ischemic period. At the end of each procedure, gentian violet was used to identify the area at risk of infarction, and triphenyltetrazolium chloride was used to delineate the area of infarct. The results showed a significant reduction in the area of infarct as a percentage of the area at risk in each bypass group compared with its control group for all ischemic periods of less than 6 hours. These findings suggest that the maximum permissible ischemic time delay for myocardial salvage by pulsatile left atrial-femoral artery bypass is one which is pertinent in a clinical setting. The results justify continued attempts to develop appropriate techniques for percutaneous application of this modality to patients with an evolving myocardial infarction.

Isolated coronary artery bypass grafting in one hundred consecutive octogenarian patients. A multivariate analysis.

One hundred consecutive patients aged 80 or older underwent isolated coronary artery bypass grafting for New York Heart Association functional class III (24%) or IV (76%) disease in our institution from 1985 to 1989. The operations were elective in 36 patients, urgent in 52, and emergent in 12. Twenty-eight patients had significant disease of the left main coronary artery, with the remainder having an average of 2.8 diseased coronary vessels. Preoperative left ventricular ejection fraction was considered good (greater than 50%) in 62 patients, fair (30% to 50%) in 24 patients, and poor (less than 30%) in 14 patients. An average of 2.8 grafts were performed per patient, and the internal mammary artery was used in 10 patients. Univariate analysis of 36 perioperative factors followed by multivariate logistic regression analysis of the significant variables (p less than 0.05) revealed that the urgency of the operation and left ventricular ejection fraction were independent predictors of operative mortality. There were 12 in-hospital deaths, and the mortality was significantly lower in the elective cases (2.8%) than in the urgent (13.5%) and emergent cases (33.3%). Major complications occurred in 14% of the elective cases, in 21% of the urgent cases, and in 67% of the emergent cases. The operative mortality rates for good, fair, and poor left ventricular ejection fraction were 4.9%, 12.5%, and 42.9%, respectively. Long-term follow-up averaging 22 months revealed a 77% actuarial probability of survival at 24 months and 51% at 48 months, with only two cardiac-related deaths. We conclude that coronary artery bypass grafting can be performed in octogenarians with a favorable outcome when done electively in patients with normal to moderately depressed left ventricular function.

The effects of amrinone versus dobutamine on myocardial mechanics and energetics after hypothermic global ischemia.

The effects on the postischemic myocardium of amrinone and dobutamine were studied in canine hearts that underwent 90 minutes of hypothermic (10 degrees C) arrested ischemia. In an isolated heart preparation cross-circulated by a support dog, left ventricular pressure-volume loops were collected under a constant afterload based on a mock circulatory system and a range of preload conditions controlled by a computerized servo volume pump. Dobutamine (0, 5, 10, 15 micrograms/kg per minute) and amrinone (0, 0.75, 1.5, 3.0 mg/kg) were tested in this order based on the weights of the support dogs in eight experiments. Changes in intrinsic myocardial contractility were analyzed as percent increases in the preload recruitable stroke work area from baselines. Dobutamine exhibited significant dose-related increases in the preload recruitable stroke work area. Amrinone did not produce significant increases in preload recruitable stroke work area at 0.75 mg/kg; amrinone's inotropic effect was equivalent to dobutamine, 5 micrograms/kg per minute at 1.5 mg/kg, and at the maximum dose (3.0 mg/kg) it was equivalent to dobutamine, 10 micrograms/kg per minute. The myocardial energetic efficiency was determined from the analysis of the myocardial oxygen consumption-pressure volume area relationship. The y intercept represents the basal metabolic oxygen requirement of the unloaded beating heart, and the slope is inversely proportional to the rate of energy conversion for increasing loading conditions. Dobutamine significantly increased the y intercepts, but it had no effects on the slopes. These changes demonstrate reduced myocardial efficiencies that are consistent with previous reports. Amrinone (0.75 and 1.50 mg/kg) did not result in change of the y intercepts and the slopes of myocardial oxygen consumption-pressure-volume area relationship from baseline conditions. The y intercept was increased with amrinone (3.0 mg/kg), although still not significantly higher than baseline and not to the extents of the dobutamine group. Dobutamine did not have any primary effect on coronary resistance, while amrinone significantly reduced coronary resistance in all loading conditions at 1.5 and 3.0 mg/kg. This study demonstrates that the inotropic effects of amrinone tested under this constant afterload preparation were lower than those of dobutamine. Amrinone has a superior profile of myocardial efficiency on the postischemic myocardium since it does not produce the oxygen-wasting effects of the traditional inotropic agents such as the beta agonists. This benefit, together with amrinone's coronary dilating effects, critically improves the supply/demand ratio that may be of importance in certain clinical situations.

Myocardial reperfusion injury. Platelet-activating factor stimulates polymorphonuclear leukocyte hydrogen peroxide production during myocardial reperfusion.

To study the roles of platelet-activating factor, polymorphonuclear leukocytes, and oxygen free radicals in myocardial reperfusion injury, we subjected 10 sheep to 90 minutes of mid-left anterior descending coronary artery followed by 6 hours of reperfusion. Stainings with gentian violet and tetratriphenyl ammonium chloride demonstrated 20% +/- 3% of the left ventricular mass at risk for ischemia, of which 75% +/- 10% underwent infarction. Coronary sinus blood was assayed for platelet-activating factor and neutrophil hydrogen peroxide production before and during coronary occlusion and during reperfusion. Platelet-activating factor was isolated by column chromatography and lipid extraction and quantified by radioimmunoassay. Neutrophil hydrogen peroxide production was measured by a 2',7'-dichlorofluorescein flow-cytometric assay. Platelet-activating factor was elevated to 899 +/- 210 pg/ml at 15 minutes of reperfusion, compared with the preocclusion level of 271 +/- 55 pg/ml and coronary occlusion level of 359 +/- 64 pg/ml (p less than 0.05; analysis of variance). Neutrophil hydrogen peroxide production, measured on a relative fluorescence scale, was also elevated to a level of 141 +/- 27 at 1 hour of reperfusion, compared with the preocclusion level of 103 +/- 6 and the coronary occlusion level of 114 +/- 13 (p less than 0.01; analysis of variance). Both of these parameters returned toward baselines at the end of 6 hours of reperfusion. Histologic examination revealed infiltration of polymorphonuclear leukocytes into the interstitium of the reperfused myocardium. Neutrophils isolated from unoperated and healthy sheep demonstrated a graded dose response in hydrogen peroxide production when stimulated by purified platelet-activating factor in vitro. These findings suggest that platelet-activating factor is released in the coronary circulation and is a mediator of oxygen free radical production in polymorphonuclear leukocytes during myocardial reperfusion.

Retrograde autologous priming for cardiopulmonary bypass: a safe and effective means of decreasing hemodilution and transfusion requirements.

OBJECTIVES: The obligatory hemodilution resulting from crystalloid priming of the cardiopulmonary bypass circuit represents a major risk factor for blood transfusion in cardiac operations. We therefore examined whether retrograde autologous priming of the bypass circuit would result in decreased hemodilution and red cell transfusion. METHODS: Sixty patients having first-time coronary bypass were prospectively randomized to cardiopulmonary bypass with or without retrograde autologous priming. Retrograde autologous priming was performed at the start of bypass by draining crystalloid prime from the arterial and venous lines into a recirculation bag (mean volume withdrawal: 880 +/- 150 ml). Perfusion and anesthetic techniques were otherwise identical for the two groups. The hematocrit value was maintained at a minimum of 16% and 23% during and after cardiopulmonary bypass, respectively, in all patients. Patients were well matched for all preoperative variables, including established transfusion risk factors. Subsequent hemodynamic parameters, pressor requirements, and fluid requirements were equivalent in the two groups. RESULTS: The lowest hematocrit value during cardiopulmonary bypass was 22% +/- 3% versus 20% +/- 3% in patients subjected to retrograde autologous priming and in control patients, respectively (p = 0.002). One (3%) of 30 patients subjected to retrograde autologous priming had intraoperative transfusion, and seven (23%) of 30 control patients required transfusion during the operation (p = 0.03). The number of patients receiving any homologous red cell transfusions in the two groups during the entire hospitalization was eight of 30 (27%; retrograde autologous priming) versus 16 of 30 (53%; control) (p = 0.03). CONCLUSIONS: These data suggest that retrograde autologous priming is a safe and effective means of significantly decreasing hemodilution and the number of patients requiring red cell transfusion during cardiac operations.

Is paraplegia after repair of coarctation of the aorta due principally to distal hypotension during aortic cross-clamping?

The hypothesis is presented that paraplegia after coarctation of the aorta is principally due to hypotension of sufficient severity and duration. In a group of 103 patients who underwent surgery during a 10-year period, the distal aortic pressure was maintained above 60 mm Hg while the aorta was cross-clamped or the period of cross-clamping was limited to less than 20 minutes. No neurologic problems occurred. In 17 of the 103 cases aortic pressure decreased below 60 mm Hg, occurring in 8% of patients with the aorta occluded below the left subclavian artery but in 30% of those occluded above. Therapeutic measures used in the 17 patients included infusion of metaraminol in five and limiting cross-clamp time to less than 20 minutes in 11. The theory is proposed that ligation of intercostal arteries in a patient with coarctation cannot injure the spinal cord because the normal direction of blood flow is reversed. Certainly, in patients without a coarctation, such as thoracic aneurysms, ligation of a critical intercostal artery may injure the spinal cord. However, in patients with coarctation the direction of blood flow is reversed, blood flowing from the intercostals into the distal aorta. The vague relationship long noted between development of collateral circulation, including rib notching, and the frequency of paraplegia probably depends not on the presence of enlarged intercostal arteries but on whether their temporary occlusion at the time of aortic cross-clamping results in distal hypotension. Data with somatosensory-evoked potentials measured during operations on the thoracic aorta in 25 patients found no changes in sensory potentials as long as the distal aortic pressure remained above 60 mm Hg, but a gradual disappearance was found at lower pressures. In five of six patients with large thoracicoabdominal aneurysms in whom sensory potentials were absent for longer than 30 minutes, paraplegia resulted. Use of somatosensory potentials provides a significant method for evaluating methods to protect from paraplegia. This method should be far more productive than are simple clinical experiences because the fortunate rare occurrence of paraplegia, one in 200, greatly limits available data.

Aortopulmonary fistula in a post-coarctation mycotic aneurysm.

A 21-year-old man presented with fever and septicemia resistant to antibiotic therapy. An unusual post-coarctation mycotic aortic aneurysm that had eroded into the left main stem bronchus was identified and replaced with a Dacron graft. A critical factor in achieving the satisfactory result was preparation of the femoral vessels for autotransfusion and possible cardiopulmonary bypass.

Quantification of pulsatile flow during cardiopulmonary bypass to permit direct comparison of the effectiveness of various types of "pulsatile" and "nonpulsatile" flow.

The relative merits of adding a "pulsatile" component to flow during cardiopulmonary bypass (CPB) has long generated controversy, the resolution of which has been hampered by lack of quantification of the "pulsatility" delivered by different devices. The present experimental series had two goals: to quantify the "pulsatility" of blood flow during CPB in terms of pulse rate and pulsatility index (PI) and to examine which aspects of a "pulsed flow" provide clinical benefits. A flow waveform can be expressed in terms of its baseline rate and its PI, the sum of the square of its harmonics components divided by the square of the mean flow. We used PI to quantify the pulsatility of blood flow in the descending thoracic aorta and used changes in the serum lactate level as an indication of end organ flow. In one experimental series seven adult mongrel dogs were placed on roller pump CPB at a constant flow of 100 ml/kg/min. After a 20-minute stabilization period a roller pump wave and three different pulse shapes (generated by a computer-controlled hydraulic pump) were evaluated for 15 minutes each. The pulse wave shapes were graded, with C being the sharpest and A the least sharp. In a second series six other dogs were placed on CPB and were subjected to roller pump perfusion and three pulse waves of identical shape but at different rates. The results indicated that a combination of a minimum PI of 1.88 and a minimum rate of 80 bpm were necessary to significantly reduce lactate production as compared with roller pump perfusion. Thus the same mean flow can have very different physiologic effects depending on how it is delivered. This quantification method permits direct comparison of different "pulsatile waveforms" and provides a means for identification of optimal pulsatile flow.

Effect of hypothermia on cellular membrane function during low-flow extracorporeal circulation.

The use of systemic hypothermia is known to allow recovery from potentially lethal states of profound hypoperfusion or total circulatory arrest. While the cellular alterations accompanying states of decreased perfusion in skeletal muscle are well defined, little is known regarding the impact of coexistent hypothermia. To investigate this issue, nine dogs were placed on total cardiopulmonary bypass (CPB) and perfused in nonpulsatile fashion. The following flow and temperature parameters were used in three different perfusion models: 3.5 L/min/m2 at 23 degrees C (group A, n = 3), 1.6 L/min/m2 at 37 degrees C (group B, n = 3), and 1.6 L/min/m2 at 23 degrees C (group C, n = 3). Assessment of cellular function in a hind limb adductor muscle by measurement of resting transmembrane potential difference (Em) and determination of tissue electrolyte distribution in a biopsy specimen was performed in the control state and again after 60 minutes of total CPB. Low-flow/hypothermic CPB (group C) was associated with depolarization of resting Em to -63.3 +/- 3.2 mV from a control value of -87.0 +/- 1.3 mV (p less than 0.05), an increase in the calculated intracellular Na ([Na]i) to 16.4 +/- 4.0 mEq/L from a control value of 7.6 +/- 1.4 mEq/L (p less than 0.05), and an increase in the ratio of the selective membrane permeabilities of Na+ to K+ (pNa/pK), to 0.067 +/- 0.013 from a control value of 0.013 +/- 0.002 (p less than 0.05). In contrast, resting Em was maintained at -86.4 +/- 6.1 mv during normal-flow/hypothermic CPB (group A), while low-flow/normothermic CPB (group B) produced an intermediate depolarization to -75.2 +/- 3.0 mV (p less than 0.05). Neither [Na]i or pNa/pK was altered significantly in group A or group B dogs. These data characterize a physiologic alteration in the cellular membrane function of skeletal muscle during low-flow/hypothermic CPB, which is similar in many respects to that accompanying hemorrhagic shock. This suggests that during periods of profound hypothermia certain flow-related derangements in skeletal muscle are not obviated and may be exacerbated.

Combined aprotinin and erythropoietin use for blood conservation: results with Jehovah's Witnesses.

Despite recent advances in blood conservation techniques, major risks persist for excessive bleeding and blood transfusion after open heart operations. We reviewed the records of 100 consecutive patients undergoing first-time coronary artery bypass grafting at our institution to define these risks and develop a multimodality blood conservation program based on the results. This program was subsequently applied on a prospective basis to a select group of patients who refuse blood transfusion on religious grounds (Jehovah's Witnesses [JW]) (n = 15). Encouraging initial results with coronary artery bypass grafting in this group (n = 8) led to the application of the program to more complex operations (n = 7), including repeat bypass grafting with use of the internal mammary artery, repeat mitral valve replacement, aortic and mitral valve replacement with coronary artery bypass grafting, mitral valve replacement with bypass grafting, chronic type 1 dissection repair, aortic valve replacement, and atrial septal defect repair in 1 patient each. The blood conservation program employed in these patients included the use of (1) aprotinin (full Hammersmith regimen), (2) high-dose erythropoietin, (3) "maximal"-volume intraoperative autologous blood donation, (4) low-prime cardiopulmonary bypass, (5) exclusive use of intraoperative cell salvage, and (6) continuous reinfusion of shed mediastinal blood. There were no deaths in the JW group. Thromboembolic complications consisted of a transient posterior circulation stroke in only 1 patient (dissection repair). No blood or blood products were transfused compared with the transfusion of 5.1 +/- 7.8 units (mean +/- standard deviation) in the 100 primary coronary bypass patients in whom the blood conservation program was not employed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of shaving methods and intraoperative irrigation on suppurative mediastinitis after bypass operations.

To investigate the effects of the hair removal methods and intraoperative irrigation on suppurative mediastinitis after cardiopulmonary bypass operations, 1,980 consecutive adult patients over a 2-year period in our institution were prospectively randomized to manual shaving versus electrical clipping of hair before the skin incision, and to povidone-iodine solution (0.5%) versus saline solution mediastinal and subcutaneous irrigation before wound closure. The overall incidence of suppurative mediastinitis was 0.86% (17/1,980). The infectious rate was significantly higher in the manually shaven (13/990) than in the electrically clipped patients (4/990) with an odds ratio of 3.25 (95% confidence interval, 1.11 to 9.32; p = 0.024). It was also higher in the povidone-iodine group (11/990) than in the saline group (6/990), although the difference was not statistically significant (p = 0.16). Fourteen patients were treated with operative debridement with closed tube irrigation, with one failure requiring a conversion to an open wound. Two patients were successfully treated with primary open wound procedures followed by delayed muscular flap closures, and 1 patient succumbed to rapid and profound sepsis soon after open drainage. We conclude that electrical clipping is superior to manual shaving in the prevention of suppurative mediastinitis. The routine use of povidone-iodine (0.5%) irrigation was of no benefit in this study and may increase the incidence of infection due to its known suppressive effects on local leukocytes and fibroblasts. Furthermore, operative debridement with closed tube irrigation was successful in treating the majority of cases in this series.

A survey of 77 major infectious complications of median sternotomy: a review of 7,949 consecutive operative procedures.

Sternal wound infections developed following 77 (0.97%) of 7,949 operative procedures involving median sternotomy at New York University Medical Center from 1976 to 1984. Risk factors associated with the development of a sternal wound infection included combined revascularization and valve replacement, early reexploration for bleeding, prolonged low cardiac output syndrome, and prolonged ventilatory support (greater than 24 hours). Concomitant infection at other sites with the same organism as cultured from the sternum was present in 42% of the patients. Thirty-seven patients (48%) were treated with radical debridement followed by closed antibiotic irrigation. In 31 other patients (40%), the wounds were debrided and left to heal by open granulation. Both initial treatments had equally high success rates (78.4% and 74.2%, respectively). However, the open granulation method resulted in a hospital stay that was an average of 10 days longer than the closed antibiotic irrigation method. Muscle flaps were used to expedite healing of open granulation in 9 patients. Analysis of the results of different treatment strategies revealed that if debridement was accomplished within 20 days of the initial cardiac procedure, 76% of the patients could be successfully treated with closed antibiotic irrigation. Conversely, if treatment was delayed for longer than 20 days, 81% of the patients were treated with open granulation (p less than 0.001). Also noted was an inverse relationship between the serum blood urea nitrogen (BUN) level and the success rate of initial treatment with closed antibiotic irrigation. Patients with a serum BUN level of less than 40 mg/dl at the time of debridement had a 90% success rate as opposed to a success rate of 38% when the BUN level was 40 mg/dl or greater. The data presented suggest the following conclusions. Early diagnosis is crucial to successful treatment of sternal wound infection. When diagnosis can be established within 20 days, 80% of infections can be eradicated by the simple approach of debridement and closed antibiotic irrigation. When diagnosis is delayed, however, prompt debridement followed by muscle flaps is the procedure of choice. Open granulation alone, while successful, unnecessarily prolongs the hospital course.

Evaluation of an extraaortic counterpulsation device in severe cardiac failure.

A valveless, single-orifice polyurethane ventricle with a maximum stroke volume of 60 mL was implanted on the brachiocephalic artery just above the aortic arch in sheep (n = 14) to act as an extraaortic counterpulsation device. In parallel, an intraaortic balloon was placed in the descending thoracic aorta. Both devices were pneumatically driven with an intraaortic balloon pump console that was gated by the electrocardiogram to provide aortic diastolic augmentation at a stroke volume of 40 mL. To compare the efficacy of counterpulsation for each device during severe cardiac failure, biventricular block was induced by continuous infusion of esmolol (100 to 600 micrograms.kg-1.min-1), titrated to reduce aortic flow and pressure to less than 75% of baseline. Pulsatile coronary and aortic flows were recorded with ultrasonic flow probes placed around their respective vessels. Aortic root and left ventricular pressures were recorded using micromanometers. The enhancement of hemodynamic variables for both devices were compared for optimal timing conditions, which were defined as inflation set just before the dicrotic notch and deflation bordering on isovolumetric systole. The extraaortic counterpulsation device was able to significantly augment aortic and coronary flows while simultaneously decreasing left ventricular tension time index and aortic end-diastolic pressure (p less than 0.02). The intraarotic balloon pump was able to significantly reduce only tension time index (p less than 0.002) to a lesser extent that the extraaortic counterpulsation device. All analysis was performed with the paired-samples t test. The extraaortic counterpulsation device greatly improves the myocardial oxygen supply-consumption ratio of the left ventricle by increasing diastolic coronary flow and reducing left ventricular wall tension during systole.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of temperature and flow rate on regional blood flow and metabolism during cardiopulmonary bypass.

Eleven dogs were subjected to a 150-minute period of cardiopulmonary bypass that consisted of a high-flow, normothermic phase, a high-flow, hypothermic phase, a low-flow, hypothermic phase, and then a high-flow, rewarming phase. Regional blood flow and oxygen consumption to the brain, intestines, kidney, and hind limb were determined at baseline and at 10-minute intervals during cardiopulmonary bypass. Blood flow to the carotid artery, superior mesenteric artery, and renal artery declined significantly with hypothermic cardiopulmonary bypass whereas blood flow to the femoral artery increased significantly. Although total body oxygen consumption returned to baseline values at the end of the rewarming phase, oxygen consumption for these regions differed somewhat from their baseline values. We conclude that blood flow during hypothermic cardiopulmonary bypass is shunted to skeletal muscle, particularly with high pump flows. Additionally, the return of total body oxygen consumption to baseline after rewarming is not necessarily reflected at the regional level.

Cardiac operations in patients with cirrhosis.

BACKGROUND: A retrospective review was performed to determine the outcome after cardiac operations in patients with a documented history of noncardiac cirrhosis. METHODS: The charts of patients admitted to the cardiothoracic surgical service between 1990 and 1996 were reviewed, and 13 patients with a preoperative history of cirrhosis were identified. The severity of preoperative liver disease was graded according to the criteria of Child. RESULTS: Most of the cases of cirrhosis were alcohol-related. Eight patients were classified as having Child class A and 5 as having Child class B cirrhosis. One hundred percent of patients with Child class B and 25% of those with Child class A cirrhosis had major complications. The postoperative chest tube output and transfusion requirements of these patients were approximately three times higher than average. The overall perioperative mortality rate was 31%. In patients with Child class B cirrhosis, the mortality rate was 80%. No patient with Child class A cirrhosis died. Deaths were related to gastrointestinal and septic complications, and not to cardiovascular failure. CONCLUSIONS: These findings suggest that patients with minimal clinical evidence of cirrhosis can tolerate cardiopulmonary bypass and cardiac surgical procedures, whereas those with more advanced liver disease should not be offered operation.

Triiodothyronine therapy lowers the incidence of atrial fibrillation after cardiac operations.

BACKGROUND: Cardiopulmonary bypass results in a euthyroid sick state, and recent evidence suggests that perioperative triiodothyronine (T3) supplementation may have hemodynamic benefits. In light of the known effects of thyroid hormone on atrial electrophysiology, we investigated the effects of perioperative T3 supplementation on the incidence of postoperative arrhythmias. METHODS: One hundred forty-two patients with depressed left ventricular function (ejection fraction < 0.40) undergoing coronary artery bypass grafting were randomized to either T3 or placebo treatment groups in a prospective, double-blind fashion. Triiodothyronine was administered as a 0.8 micrograms/kg intravenous bolus at the time of aortic cross-clamp removal followed by an infusion of 0.113 micrograms.kg-1.h-1 for 6 hours. Patients were monitored for the development of arrhythmias during the first 5 postoperative days. RESULTS: The incidence of sinus tachycardia and ventricular arrhythmias were similar between groups. Triiodothyronine-treated patients had a lower incidence of atrial fibrillation (24% versus 46%; p = 0.009), and fewer required cardioversion (0 versus 6; p = 0.012) or anticoagulation (2 versus 10; p = 0.013) during hospitalization. Six patients in the T3 group versus 16 in the placebo group required antiarrhythmic therapy at discharge (p = 0.019). CONCLUSIONS: Perioperative T3 administration decreased the incidence and need for treatment of postoperative atrial fibrillation.