Immediate functional benefits after controlled reperfusion during surgical revascularization for acute coronary occlusion

Controlled Reperfusion Reduces Reperfusion Injury in Skeletal Muscle After Incomplete Limb Ischemia

Systemic and local complications occur after revascularization of extremities exposed to prolonged complete ischemia. Recently the authors demonstrated in experimental and clinical studies that these deleterious effects after normal blood (uncontrolled) reperfusion could be reduced significantly by controlling the composition of the reper fusate (calcium, pH, amino acids, osmolarity, and glucose) and the circumstances of the reperfusion (time, temperature, and pressure; controlled reperfusion) after complete prolonged limb ischemia. In this study the authors test the hypothesis that controlled reperfusion also has a beneficial effect and is safe to apply after a period of six hours of incomplete limb ischemia.

Ten adult German house swine were exposed to six hours of incomplete limb ischemia by occlusion of the left iliac artery. This resulted in a significant reduction of limb tissue temperature (P < 0.0003, ANOVA), pH, (P < 0.0003, ANOVA), and adenosine triphosphate (ATP) (P < 0.0003, ANOVA), as well as in increased levels of (continued on next page) (Abstract continued) creatine kinase (CK) in the systemic venous (P < 0.003, ANOVA) and in the femoral vein blood (P < 0.03 ANOVA). To simulate the clinical situation of embolectomy in 5 pigs the authors released the occlusive snares after the ischemic period and let the normal blood flow with systemic pressure occur (uncontrolled reperfusion). In the other 5 pigs (controlled reperfusion) they delivered a controlled reperfusate by with drawing blood from the aorta and mixing it with a crystalloid solution (calcium reduced, hyperosmolaric, hyperglycemic, alkalotic, glutamate and aspartate enriched, and containing a free radical scavenger) under controlled conditions (ratio blood:crys talloid solution 6:1, for thirty minutes, reperfusion pressure < 50 mmHg, and normoth ermia) before establishing normal blood reperfusion.

During the initial reperfusion (measured at five minutes after start of reperfusion) the group with controlled reperfusion (as compared with the animals with uncontrolled reperfusion) showed higher oxygen consumption (32.7 ±3.4 vs 15.8 ±1.9 mL/100g/min, P < 0.01, ANOVA), higher glucose consumption (439.0 ±115.7 vs 16.5 ±4.7 mg/100g/min, P < 0.03, ANOVA), less vascular resistance (19.2 ±2.8 vs 31.4 ±2.1 dyn x sec/cm5, P < 0.03, ANOVA) as well as less lactate dehydrogenase (LDH; 286.2 ±38.2 vs 604.6 ±30.7 U/L, P < 0.0003, ANOVA) and creatine kinase (CK; 294.2 ±73.0 vs 602.8 ±85.5 U/L, P < 0.03, ANOVA) concentration in the femoral vein blood. At the end of the observation period (measured at ninety minutes after start of reperfusion), the group with controlled reperfusion showed less tissue water content (81.8 ±0.7 vs 84.3 ±0.7%, P < 0.05, ANOVA), higher tissue ATP content (17.0 ±2.4 vs 9.7 ±4.3 μ Mol/g protein, ns), higher tissue ATP increase as compared with end ischemic values (6.1 ±1.5 vs -2.5 ±1.8 μMol/g protein, P < 0.03, ANOVA), higher tissue pH (7.2 ±0.1 vs 6.8 ±0.1, P < 0.03, ANOVA), less temperature decrease (0.3 ±0.2 vs 1.2 ±0.3°C, P < 0.05, ANOVA), less reduction of flow in the limb (0.2 ±0.2 vs -1.3 ±0.4 mL/100g/min, P < 0.03, ANOVA), less vascular resistance (16.7 ±1.2 vs 22.8 ±1.5 dyn x sec/cm 5, P < 0.03, ANOVA), less CK (355.0 ±87.5 vs 624.4 ±73.4 U/L, P < 0.05, ANOVA) and LDH (369.5 ±42.5 vs 538.4 ±39.1 U/L, P < 0.03, ANOVA) concentration in the femoral vein blood as well as less CK (335.0 ±89.0 vs 595.8 ±76.6, P < 0.05) and LDH (356.5 ±48.9 vs 546.0 ±37.8 U/L, P < 0.0003, ANOVA) concentration in the central venous blood.

These data indicate that severe local and systemic damage occurs with uncontrolled (normal blood) reperfusion even after incomplete limb ischemia and that these reper fusion changes can be reduced significantly by delivering a controlled reperfusate under controlled conditions without any observable negative side effects. They confirm the results with controlled limb reperfusion after prolonged complete limb ischemia (aortic occlusion), and this concept has already been successfully applied in 15 patients with complete and incomplete limb ischemia as long as eighteen hours.

Does leukocyte-depleted blood cardioplegia reduce myocardial reperfusion injury in cardiac surgery? A systematic review and meta-analysis

Blood cardioplegia in cardiac surgery contains leukocytes, which causes the inflammatory reaction and promotes myocardial reperfusion injury. The removal of leukocytes from the cardioplegia line, using specialized filters, has been proposed as one of the effective methods in attenuating the inflammatory response. We performed a two-level search to identify randomized, controlled trials concerning the effects of leukocyte-depleted blood cardioplegia on myocardial reperfusion injury. Sixteen studies, comprising 738 patients, met the selection criteria. There are significant reductions in creatinine kinase isoenzyme MB (CK-MB) during 4-8h postoperatively (SMD - 0.577; 95% CI -0.795 to -0.358; p=0.000), CK-MB peak (SMD - 0.713; 95% CI -1.027 to -0.400; p=0.000), troponin in the period of 4-8h postoperatively (SMD - 0.502; 95% CI -0.935 to -0.069; p=0.023), troponin peak (SMD - 0.826; 95% CI -1.373 to -0.279; p=0.003) and inotropic support (RR, 0.500; 95% CI 0.269 to 0.931; p=0.029). Leukocyte-depleted blood cardioplegia may reduce myocardial reperfusion injury in the early postoperative period, but there has been no evidence to support the clinically significant difference. Larger and more precise randomized control trials are needed to further elucidate the cardioprotective effects of cardioplegia leukofiltration.

The use of controlled reperfusion strategies in cardiac surgery to minimize ischaemia/reperfusion damage

Ischaemia and reperfusion occur during almost every cardiac operation, and one of the key elements to achieve a successful operation is to counteract the detrimental effects of induced ischaemia and reperfusion during the operation. The cardiac surgeon is in a unique position to protect the heart before ischaemia is induced and to avoid further damage during the reperfusion period. The surgeon can alter the composition of the reperfusate and the conditions of reperfusion so that the ischaemia/reperfusion injury is minimal, even after very complex procedures that require long aortic cross-clamp periods. This in turn allows him to perform a near-perfect surgical repair of the underlying disease without the pressure of time. The vast knowledge gained in this field over the years has led to application in other organs, such as the limbs (acute limb ischaemia), lungs (lung transplantation), kidney and liver (kidney and liver transplantation), and more recently even for the brain [acute cerebral artery occlusion (stroke)] and the whole body (cardiopulmonary resuscitation). Further improvements in reperfusion strategies will allow salvage of tissue and even whole body after ischaemic periods thought previously to be irreversibly damaged.

The effects of various leukocyte filtration strategies in cardiac surgery

It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbidity and mortality. Several anti-inflammatory strategies have been implemented to reduce this response, including leukocyte removal from the circulation using specialised filters. The aim of this study is to systematically review the available evidence on leukocyte filtration in cardiac surgery, focusing on its effect on systemic inflammation and whether this has influenced clinical outcomes. Five electronic databases were systematically searched for studies reporting the effect of leukocyte filtration at any point within the cardiopulmonary bypass circuit in humans. Reference lists of all identified studies were checked for any missing publications. Two authors independently extracted the data from the included studies. Whilst systemic leukodepleting filters do not appear to consistently lower leukocyte counts, they may preferentially remove activated leukocytes. Small improvements in early post-operative lung function in patients receiving systemic leukodepletion have been reported, but this does not lead to reduced hospital stay or decreased mortality. There is substantial evidence that cardioplegic leukocyte filtration attenuates the reperfusion injury at a cellular level, but this has not been translated into clinical improvements. Finally, whilst various strategies involving multiple leukocyte filters, or the incorporation of pharmacological agents into leukocyte-depleting protocols have been evaluated, the current available results are not conclusive. Our study suggests that there is not enough high quality or consistent evidence to draw guidelines regarding the use of leukocyte-depleting filters within routine cardiac surgical practice.

Low-pressure reperfusion alters mitochondrial permeability transition

We hypothesized that low-pressure reperfusion may limit myocardial necrosis and attenuate postischemic contractile dysfunction by inhibiting mitochondrial permeability transition pore (mPTP) opening. Male Wistar rat hearts (n = 36) were perfused according to the Langendorff technique, exposed to 40 min of ischemia, and assigned to one of the following groups: 1) reperfusion with normal pressure (NP = 100 cmH(2)O) or 2) reperfusion with low pressure (LP = 70 cmH(2)O). Creatine kinase release and tetraphenyltetrazolium chloride staining were used to evaluate infarct size. Modifications of cardiac function were assessed by changes in coronary flow, heart rate (HR), left ventricular developed pressure (LVDP), the first derivate of the pressure curve (dP/dt), and the rate-pressure product (RPP = LVDP x HR). Mitochondria were isolated from the reperfused myocardium, and the Ca(2+)-induced mPTP opening was measured using a potentiometric approach. Lipid peroxidation was assessed by measuring malondialdehyde production. Infarct size was significantly reduced in the LP group, averaging 17 +/- 3 vs. 33 +/- 3% of the left ventricular weight in NP hearts. At the end of reperfusion, functional recovery was significantly improved in LP hearts, with RPP averaging 10,392 +/- 876 vs. 3,969 +/- 534 mmHg/min in NP hearts (P < 0.001). The Ca(2+) load required to induce mPTP opening averaged 232 +/- 10 and 128 +/- 16 microM in LP and NP hearts, respectively (P < 0.001). Myocardial malondialdehyde was significantly lower in LP than in NP hearts (P < 0.05). These results suggest that the protection afforded by low-pressure reperfusion involves an inhibition of the opening of the mPTP, possibly via reduction of reactive oxygen species production.

Blood cardioplegia filtration

The introduction of blood cardioplegia has been proven to limit ischaemia and reperfusion injury in cardiac surgery. But the presence of activated neutrophils in the capillary bed may cause further damage. Leukocyte filters have been shown to be very effective in reducing the leukocytes in blood cardioplegia to less than 10%. Leukocyte depletion of blood cardioplegia provides an excellent approach to minimizing myocardial injury, predominantly in high-risk cardiac surgery.

Cardiopulmonary bypass for bilateral sequential lung transplantation in patients with chronic obstructive pulmonary disease without adverse effect on lung function or clinical outcome

OBJECTIVE

The use of cardiopulmonary bypass in lung transplantation remains controversial. Previous studies have concluded that cardiopulmonary bypass is deleterious, but these studies were confounded by the inclusion of patients with different diagnoses undergoing single- and double-lung transplantation with elective or emergency use of bypass. The goal of this study was to determine whether cardiopulmonary bypass has deleterious effects on lung function or clinical outcome by analyzing the cases of patients with a single disease entity and elective use of bypass for bilateral sequential lung transplantation.

METHODS

A retrospective review of 50 patients with chronic obstructive pulmonary disease who underwent bilateral sequential lung transplantation was performed. Fourteen patients who underwent elective cardiopulmonary bypass for 218.3 +/- 75.4 minutes were compared to 36 control patients.

RESULTS

After the operation, the bypass and nonbypass groups were not significantly different with respect to median duration of mechanical ventilation (1 day vs 1 day, P =.76), median stay in the intensive care unit (4 days vs 4 days, P =.44), median hospital stay (15.5 days vs 16 days, P =.74), mean increase in serum creatinine level (1.4 +/- 1.9 mg/dL vs 0.9 +/- 1.0 mg/dL, P =.33), and mean ratio of Pao(2) to fraction of inspired oxygen at 1 hour (376.6 +/- 123 vs 357.0 +/- 218, P =.75), at 24 hours (309.9 +/- 92 vs 350.6 +/- 122, P =.26), and at 48 hours (335.0 +/- 144 vs 316.2 +/- 120, P =.64). Late outcome markers compared between the bypass and nonbypass groups were the following: 1-year percentage predicted forced expiratory volume in 1 second (76.1% +/- 17.0% vs 85.3% +/- 21.7%, P =.24), 30-day mortality (7.1% vs 8.3%, P >.999), 1-year survival (85.7% vs 80.1%, P =.66), 3-year survival (64.3% vs 58.3%, P =.70), and the prevalence of bronchiolitis obliterans syndrome (0% vs 36.1%, P =.01).

CONCLUSION

Cardiopulmonary bypass appears to have no deleterious effect on early lung function or clinical outcome. We hope that this pilot study removes some of the unwarranted fear of the use of bypass in lung transplantation for chronic obstructive pulmonary disease.

Proximal aortic dissection with coronary malperfusion: presentation, management, and outcome

BACKGROUND

Acute myocardial ischemia and infarction due to retrograde dissection of the aortic root reaching the coronary ostia is a potentially fatal condition. Surgical treatment of these patients relies on the re-establishment of an adequate coronary blood flow and on the rescue of jeopardized myocardium. This article reports the results of a selected group of 24 patients with type A acute aortic dissection and coronary artery dissection. We review our experience and illustrate our approach to this condition, which evolved over a 15-year period.

METHODS

Between July 1985 and March 2000, 24 patients from a total of 211 (11.3%) treated for acute type A aortic dissection had dissection of at least one of the coronary ostia. There were 14 men and 10 women. The mean age was 65.5 years (median 61.7; range 41-78 years). The right coronary artery was involved in 11 patients, the left in 4 patients, and both coronary arteries in 9 patients. At admission, 16 patients had Q waves (66%), inferior in 6 (25%) and anterior, lateral, septal, or posterior in 10 (41%). All procedures were done on an emergency basis within 10 hours (median 4 hours) after initial chest pain and within 2 hours after the patient's arrival.

RESULTS

Hospital mortality was 20% (5 patients); 3 patients could not be weaned from cardiopulmonary bypass and died intraoperatively, and 2 patients died postoperatively of low cardiac output.

CONCLUSIONS

As illustrated in this study, direct coronary repair is a safe alternative to bypass grafting. Aggressive myocardial resuscitation together with early operation is a key factor in the management of these patients.

Cardioplegia solutions--unproven herbal approach versus tested scientific study

Cardioplegic solutions are used throughout the world, but must undergo careful testing before their clinical application. This study points out the importance of recognizing the hemodynamic changes produced by tested solutions so that appropriate decisions can be made in selecting crystalloid or blood solutions. Examples are provided, in which arbitrary changes made by the well-intentioned surgeon can produce damage through unanticipated alterations that are introduced without prior testing, and then used clinically. Recognition of the advantages and disadvantages of each solution is the underpinning of selection for clinical use so that unanticipated misadventures do not occur. Furthermore, the importance of making solutions in pharmacies with good manufacturing practices can avoid causing problems that would otherwise be prevented. Fundamentally, cardioplegic solutions are direct cardiac medications that must be tested as other drugs are so that unforeseen problems are avoided.

Protection of acutely ischemic myocardium by controlled reperfusion

The goal of revascularization after acute occlusion of a coronary artery is the return of contractile function and the reduction of mortality. Although reperfusion of ischemic myocardium is a prerequisite for return of function, it may, in itself, cause further injury. Controlled blood cardioplegic reperfusion reduces this "reperfusion injury" and provides maximal myocardial protection. In this article, we review recent advances in surgically controlled reperfusion and speculate on future prospects for myocardial protective techniques in patients with acute coronary artery occlusion.

Single aortic cross-clamp technique in coronary surgery: a prospective randomized study

OBJECTIVE

To test the hypothesis of an improved myocardial and cerebral protection by combining blood cardioplegia and the single aortic cross-clamp technique, 100 patients were enrolled in a prospectively randomized study and stratified for preoperative conditions.

METHODS

In Group I, 55 patients underwent myocardial revascularization using crystalloid cardioplegia and the conventional partial occluding clamp technique to perform proximal anastomoses, whereas in Group II, 45 patients were operated on combining blood cardioplegia and the single aortic cross-clamp technique. Unstable angina, emergency procedures, reoperations and preoperative counterpulsation accounted for an higher risk score in group II patients (P < 0.03). Operations were performed by the same surgical team. Aortic cross-clamp time was significantly longer in group II patients (59 +/- 22 vs. 47 +/- 18 min.) (P < 0.001). Other intraoperative variables were not significant.

RESULTS

A 70-year-old male in group I died on post-operative day 5 as a consequence of a major neurological event. Length of ventilatory dependency, post-operative bleeding, need for blood transfusions, ICU stay, and hospital stay were similar between the two groups (P = NS). Patients in group I showed a strict correlation between the duration of surgical ischemia and post-operative myocardial necrosis. Analysis of combined mortality and morbidity events (adverse events) between the two groups, led to a significant prevalence in group I patients (P < 0.03) in spite of an higher pre-operative risk score and longer ischemic times in group II patients. Neurological lesions remained confined to group I patients.

CONCLUSIONS

The combined use of blood cardioplegia, delivered via the antegrade and retrograde routes, and the single-clamp technique to perform myocardial revascularization, might enhance myocardial and cerebral protection when compared to conventional methods. Larger groups of patients are needed to support this trend.

Critical importance of the first 10 minutes of lung graft reperfusion after hypothermic storage

BACKGROUND

We have shown previously that lung graft function can be improved by achieving reperfusion with stepwise increments of perfusion pressure over 60 minutes. This study aimed to establish whether similar benefit could be achieved with a shorter, simpler protocol and different storage conditions.

METHODS

Rat lungs were flushed with University of Wisconsin or modified Euro-Collins solution and reperfused for 1 hour with blood from a support animal. Grafts were reperfused immediately or after storage at 4 degrees C for 24 hours (University of Wisconsin solution) or 6 hours (Euro-Collins solution). Stored-graft reperfusion was initiated with a 0-, 5-, or 10-minute period during which reperfusion pressure was reduced by 50%.

RESULTS

Stored grafts receiving 0 to 5 minutes of initial low-pressure reperfusion performed poorly, with reduced oxygenation and blood flow and elevated pulmonary artery pressure, airway pressure, and wet/dry weight ratio. In contrast, 10 minutes of initial 50%-pressure reperfusion yielded function comparable with that in controls with both storage conditions.

CONCLUSIONS

An initial 10-minute period of 50%-pressure reperfusion improves the function of stored rat lung grafts, whereas 5 minutes is insufficient.

Experimental application of controlled limb reperfusion after incomplete ischaemia

Severe local and systemic complications may occur after revascularization of extremities exposed to prolonged complete or incomplete ischaemia. These complications may be reduced by controlling the reperfusate and the circumstances of the reperfusion period. Ten adult German domestic pigs were exposed to 6 h of incomplete limb ischaemia by occlusion of the left iliac artery. To simulate the clinical situation of embolectomy, the occlusive snares were released after the ischaemic period in five pigs and normal blood flow developed with systemic pressure (uncontrolled reperfusion). In the other five pigs, a controlled reperfusate was delivered at controlled pressure before establishing normal blood reperfusion (controlled reperfusion). At the end of the observation period (90 min after start of reperfusion), the group with controlled reperfusion had a lower mean(s.e.m.) tissue water content (81.8(0.7) versus 84.3(0.7) per cent, P < 0.05, a greater increase in tissue adenosine 5'-triphosphate compared with values at the end of ischaemia (6.2(1.5) versus -2.5(1.8) mumol per g protein, P < 0.03), a higher tissue pH (7.2(0.1) versus 6.8(0.1), P < 0.03), a smaller temperature decrease (0.3(0.2) versus 1.2(0.3) degrees C, P < 0.05), lower concentrations of creatine kinase (355.0(87.5) versus 624.4(73.4) units/l, P < 0.05) and lactate dehydrogenase (LDH) (369.5(42.5) versus 538.4(39.2 units/l, P < 0.03) in the femoral vein blood and lower LDH concentrations (356.5(48.9) versus 546.0(37.8 units/l, P < 0.03) in central venous blood. These data indicate that severe local and systemic damage occurs with uncontrolled (normal blood) reperfusion even after incomplete limb ischaemia, and that these changes can be reduced by delivering a controlled reperfusate under controlled conditions.

Protection of evolving myocardial infarction and failed PTCA

Acute myocardial infarction is caused by acute coronary occlusion and is the major cause of death in Europe and the United States. In-hospital mortality is due principally to cardiogenic shock because of extensive ischemic muscle damage. Previous surgical results of coronary artery bypass grafting for left ventricular power failure have been disappointing because intraoperative ischemic injury is superimposed on severe damage already sustained by the myocardium. Surgical revascularization has, in general, been restricted to patients with acute occlusion after elective percutaneous transluminal coronary angioplasty with or without thrombolytic therapy. During the last years new knowledge has been gained in the pathophysiology of acute coronary occlusion on ischemic and nonischemic (remote) myocardium that has evolved in a new surgical strategy for revascularization of patients with evolving myocardial infarctions and failed percutaneous transluminal coronary angioplasty. Studies of the natural history of acute regional ischemia have shown that acute occlusion of a coronary artery not only affects the ischemic myocardium but causes structural, functional, and metabolic alterations in the remote and adjacent myocardium. These changes in the remote myocardium are even more severe if the remote myocardium is supplied by a stenotic coronary artery. Furthermore, many experimental and clinical studies have shown that normal blood reperfusion of myocardium injured previously by ischemia leads to additional damage (reperfusion injury).(ABSTRACT TRUNCATED AT 250 WORDS)

New surgical treatment for severe limb ischemia

Revascularization after prolonged complete limb ischemia may result in severe damage to skeletal muscle and systemic alterations (postischemic syndrome). Our previous experimental studies have shown that this injury can be reduced substantially by treating the jeopardized extremity by controlling the conditions of reperfusion and composition of the initial reperfusate. In the present study this concept of controlled limb reperfusion was applied in patients with prolonged severe limb ischemia. Controlled limb reperfusion was used in 14 patients after prolonged complete uni- or bilateral ischemia. The ischemic interval ranged from 5 to 21 h. Two patients were in cardiogenic shock, 11 had associated cardiac disease, and seven coexistent peripheral vascular disease. After systemic heparinization, standard thromboembolectomy was done using a Fogarty catheter. Cannulas were placed into the iliac, profunda, and superficial femoral arteries and were connected to a reperfusion set. Oxygenated blood was drawn from the iliac artery and mixed with an asanguineous solution (ratio 6:1). This controlled reperfusate was delivered into the profunda and superficial femoral arteries using a single rollerpump. The system allows control of the composition of the reperfusate (calcium, pH, osmolarity, glucose, substrate, pO2, free radical scavengers) and the conditions of reperfusion (pressure, flow, temperature). After 30 min of controlled limb reperfusion, the cannulas were removed and normal blood reperfusion started. All 12 patients who were stable hemodynamically before the operation survived the revascularization. Eleven patients, including one with acute aortic occlusion for several hours, were discharged with functional recovery of their extremities. Despite the severe ischemic insult, controlled limb reperfusion avoided amputation and profound systemic complications. Two patients who were in cardiogenic shock preoperatively died from progressive cardiac failure. We conclude that controlled arterioarterial limb reperfusion may reduce the local manifestations of the postischemic syndrome after prolonged periods of ischemia, may salvage limbs thought previously to be damaged irreversibly by prolonged ischemia, and can be done easily in the operating room.

Postcardioplegia acute cardiac dysfunction and reperfusion injury

In cardiac surgery, an obligatory period of ischemia is imposed in order to provide a convenient operative field. Brief periods of ischemia produce systolic and diastolic abnormalities related to pathology occurring during ischemia per se (ischemic injury) or expressed after the onset of reperfusion (reperfusion injury). In the surgical setting, ischemia may be encountered preoperatively with preexisting coronary disease, hypotension, or ventricular fibrillation, between intermittent infusions of cardioplegia solutions, or as a result of maldistribution of cardioplegia solution. The potential for reperfusion injury exists not only at the time of cross-clamp removal, but also with each infusion of cardioplegia solution. Infusion of cardioplegic solution is, in fact, a form of reperfusion to previously ischemic myocardium. Ischemic injury and reperfusion injury are intimately linked in that the severity of ischemia sets the stage for and determines, in part, the extent of reperfusion injury. Mild-to-moderate systolic dysfunction, which may be called "postcardioplegia stunning," remains a significant complication after cardiac surgery. More significant postoperative functional depression may occur in hearts with severe preoperative dysfunction, and in operations requiring long cross-clamp times. In addition, the failure to adequately distribute cardioplegic solution to all areas of the myocardium because of coronary stenoses, high coronary resistance or inadequate delivery pressure-flow relations, contributes to postcardioplegia dysfunction. However, the cardioplegic solution itself may also contribute to postcardioplegic dysfunction by creating temporary ionic and metabolic abnormalities. In addition, systemic hypocalcemia or hyperkalemia resulting from using large doses of cardioplegic solution may temporarily aggravate postcardioplegic mechanical dysfunction. Current formulations and strategies for delivery of cardioplegia solutions are designed to address the various contributors to both ischemic and reperfusion injury that may impact on postoperative mechanical performance. Ischemic injury is avoided by reducing myocardial oxygen demand by engaging immediate arrest and cooling the heart to approximately 10 degrees centigrade, and intermittently infusing solution to reoxygenate the myocardium, maintain hypothermia, and wash out accumulated metabolites. Reperfusion injury may be avoided by infusing hyperosmotic solutions at moderate pressures, and by incorporating oxygen radical scavengers or inhibitors to reduce membrane lipid peroxidation, myocellular and microcirculatory (endothelium) damage.(ABSTRACT TRUNCATED AT 400 WORDS)

Controlled reperfusion during emergency coronary artery bypass surgery after angioplasty failure restores immediate segmental contractility

This study tests the hypothesis that careful control of the composition of the initial reperfusate and the conditions of the reperfusion during emergency CABG will restore immediate segmental contractility in the previously ischemia area despite ischemic intervals of greater than 2 hours. Between January 1987, and October 1990, 41 consecutive patients with acute coronary occlusion (90% due to PTCA failures) were reperfused during emergency myocardial revascularization according to one of two different protocols: in 25 patients the reperfusate was normal blood given at systemic pressure ("uncontrolled reperfusion"); in 16 patients the ischemic segment was reperfused during the first 20 minutes with a regional blood cardioplegic solution (substrate-enriched, hyperosmotic, hypocalcemic, alkalotic, diltiazem-containing) at 37 degrees C at a pressure of 50 mmHg. Thereafter, total bypass was prolonged for an additional 30 minutes before extracorporeal circulation was discontinued ("controlled reperfusion"). Assessment of regional contractility (echocardiography, radionuclide ventriculography), electrocardiographic evidence of myocardial infarction, release of CK and CK-MB enzymes, and hospital mortality were performed. Quantification of regional contractility was done with a scoring system from 0 (normokinesis) to 4 (dyskinesis). Data are expressed as mean +/- standard error of the mean. Both groups were well matched for age, sex, and the distribution of the occluded artery. In the controlled reperfusion group there was a higher incidence of previous infarctions (50% vs 30%), additional significant stenosis (1.1 +/- 0.2 vs 0.8 +/- 0.1), and cardiogenic shock (38% vs 20%) as compared to uncontrolled reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)