Assisted Circulation in Cardiac and Respiratory Insufficiency

Summary: Intra-aortic counterpulsation with a balloon pump (IABP) was used in 63 patients with cardiogenic shock, heart failure after surgery with artificial circulation, internal lacerations of the myocardium, or unstable angina. It was found that the IABP was most efficient in conditions related to myocardial ischemia. Use of arteriovenous perfusion (in 11 patients) or artificial ventricles is indicated in severe perturbations of the pumping function of the heart. As experience has shown, cardiologic and heart surgery patients usually have multiorgan insufficiency. For this reason, it is necessary to use other artificial organs in complex treatment: artificial lungs, kidneys, livers, etc.     

Coronary circulation and myocardial oxygen consumption after extracorporeal circulation and after cardioplegic arrest.

The influence of haemodilution or of blood perfusion on the coronary circulation, myocardial oxygen consumption and on haemodynamic parameters was examined in two comparable groups of patients with slight congenital acyanotic cardiac malformation without indications of myocardial damage. In a third group of patients similar data were collected before and after artificial cardiac arrest by cardioplegic solutions. No findings concerning this question could be found in the literature. Coronary circulation was measured by the argon-gas-technique of Bretschneider et al. A fall in haemoglobin of 4.8% caused by haemodilution resulted in the first group in an increase in the cardiac index of about 8% and an increase in the coronary circulation of about 100% over the initial value with a simultaneous decrease in the coronary resistance due to coronary dilatation and reduction in blood viscosity. The myocardial O2 consumption was raised in spite of an increase in the coronary-venous O2 saturation and a clear reduction in the AVD O2. In contrast, the patients in the blood perfusion group showed no change in the coronary circulation and coronary resistance although a decrease of the myocardial O2 consumption was observed. The cardiac index fell to about 16% in these patients. After cardioplegic cardiac arrest there was no significant reduction in myocardial blood flow except for a decrease of myocardial oxygen consumption of about 20% The results are discussed and cantra-indications of haemodilution perfusion and cardioplegic cardiac arrest mentioned.     

The effect of pulsatile perfusion on aortocoronary bypass grafting

To evaluate the effect of pulsatile perfusion on myocardial protection and peripheral circulation, 23 patients undergoing aortocoronary bypass grafting were studied by dividing two groups; one with pulsatile perfusion technique (11 patients) and the other with non-pulsatile (12 patients). The cardiac functional assessments were made on CI, LVSWI, PCWP, CVP at 3, 6, 12 and 24 hours after the operation and the enzyme (CPK, CPK-MB, LDH, GOT) sampling were performed on 1, 2, 4 and 7 days after the operation. The difference between esophageal and rectal temperature, and urine output during cardiopulmonary bypass, indicating the peripheral circulation, were also measured. From these clinical results, it is concluded that pulsatile perfusion method is to be beneficial in myocardial protection and peripheral circulation during operation of aortocoronary bypass grafting.     

Long-Term Circulatory and Respiratory Support Using Two Artificial Ventricles and a Fluorocarbon Oxygenator

Using a new heart-lung machine developed at our Institute, experiments were conducted on dogs, donkeys, and monkeys, providing complete and assisted artificial circulation, assisted oxygenation, and perfusion preservation of the heart. The new apparatus consists of two sequentially mounted artificial ventricles working in an antiphase mode; blood oxygenation is accomplished by a reusable oxygenator with a fluorocarbon preoxygenator. Experimental results indicate that clinical use of the apparatus is promising and deserves consideration. The conditions of perfusion were close to physiological conditions and provided long-term survival of the animals. Performance in left ventricular bypass was optimized by monitoring myocardial PO2 and the state of the quick-connect/cut-off assemblies.     

Experimental evaluation of the influence of complete artificial circulation on renal circulation and tissue metabolism -comparative study of pulsatile vs nonpulsatile circulation.

In this study, pulsatile and nonpulsatile assisted circulation were compared to evaluate renal circulation under complete artificial circulation. In addition, differences were also compared between animals supported by high (assist rate 80%)- and low (assist rate 60%)-level artificial circulation. Using 20 pigs, ventricular fibrillation was induced after cardiogenic shock, assist by mechanical support by pulsatile and nonpulsatile artificial circulation. Hemodynamics and renal circulation were evaluated by measuring renal arterial blood flow, renal cortical blood flow, renal medullar blood flow, cortical/medullar flow ratio, serum urea nitrogen levels, blood creatinine levels, urinary beta(2)-microglobulin (MG) levels, and serum beta(2)-MG levels. Tissue metabolism was evaluated by comparing arterial ketone body ratios and lactic acid/pyruvic acid ratios. During the acute stage of cardiogenic shock, redistribution of renal blood flow and tissue metabolism were improved in the pigs with pulsatile artificial circulation, suggesting the usefulness of pulse pressure. In nonpulsatile artificial circulation, the possibility of irreversible renal dysfunction was suggested. Although changes in renal blood flow were smaller in high-level artificial circulation than in low-level artificial circulation, physiological maintenance of renal circulation was better in pulsatile artificial circulation than in nonpulsatile artificial circulation. These results suggest that this effect of pulsatile assisted circulation may become more marked when evaluated in the early state after cardiogenic shock.     

Effects of graded infusion rates of propofol on cardiovascular haemodynamics, coronary circulation and myocardial metabolism in dogs

We have studied the effects of a 30-min infusion of propofol 6, 9, 12, 15, 18 and 21 mg kg-1 h-1 on cardiovascular haemodynamics, coronary circulation and myocardial metabolism in 12 mongrel dogs. Mean plasma concentrations of propofol after infusion of 6 and 21 mg kg-1 h-1 increased from 2.9 (SEM 0.3) to 11.5 (0.1) micrograms ml-1. Propofol produced a progressive decrease in arterial pressure. Heart rate tended to decrease at 15, 18 and 21 mg kg-1 h-1 and cardiac index decreased significantly at infusion rates > or = 9 mg kg-1 h-1. Systemic vascular resistance tended to increase except at 21 mg kg-1 h-1 and left ventricular systolic and diastolic function were depressed. Both coronary sinus blood flow and myocardial oxygen consumption decreased in parallel with a decrease in left ventricular minute work index without producing lactate. Propofol produced progressive decreases in coronary blood flow and myocardial oxygen consumption but did not exert adverse effects on the coronary circulation.      

Biventricular Bypass: Alternative to Univentricular Bypass and Total Artificial Heart–Bridge

Left ventricular and biventricular bypasses (LVBs, BVBs) were performed in 102 experiments in sheep, goats, and donkeys. Biventricular bypass was performed in the assisted circulation mode or in the paracorporeal artificial heart bridge (PCAHB) mode when the natural heart fibrillates. During implantation of artificial ventricles instead of a heart-lung bypass, counterpulsation was used. Several types of connective conduits were developed and tested in experiments. The conduits included bifurcational connective pipes that permit "intake" of blood into artificial ventricles from atria and ventricles of the natural heart simultaneously and consequently provide effective blood flow through shunts not depending on the state of the natural heart (acute cardiac weakness or asystole). Monitoring gas content (PO2, PCO2, and pH) in the myocardium of both ventricles suggested development of right ventricular failure under conditions of LVB before hemodynamic changes occurred and confirmed the preferability of BVB over other methods of assisted circulation, as it is most effective and capable of normalizing short-term cardiac disturbances in the course of the 1st 2 days. Survival time of experimental animals (2-3 days for dogs, 5-12 days for sheep, goats, and donkeys) is sufficient to overcome acute cardiac insufficiency. This suggests that BVB in the assisted circulation mode or PCAHB mode can serve as a bridge for cardiac transplantation for the time of search for the available organ.     

体外循环下冠状动脉旁路移植术中性粒细胞表面黏附分子表达水平的临床观察

目的 以心肌肌钙蛋白Ⅰ（cTnⅠ）作为心肌损伤的标志物,观察心肌缺血-再灌注损伤期中性粒细胞表面黏附分子CD11b冠脉循环和外周循环的表达水平.方法 选取12例择期进行冠状动脉旁路移植手术（CABG）者,分别于CPB开始前、CPB中和主动脉开放后,经冠脉循环和体循环同时取血,测定中性粒细胞表面CD11b平均荧光强度和血清cTnⅠ浓度.结果 冠脉循环和体循环血cTnⅠ浓度在主动脉开放后均明显升高（P＜0.05）;CPB期间和主动脉开放后,体循环血CD11b含量不断升高,而冠脉循环内CD11b含量则呈现下降趋势,二者间差异有统计学意义（P＜0.05）.结论 体外循环期间,存在心肌缺血-再灌注损伤.激活的中性粒细胞有冠脉滞留效应,中性粒细胞表面CD11b表达水平在冠脉循环中下降,在体循环中升高,出现分离现象,此时单纯以冠脉循环内CD11b表达水平判定心肌缺血再灌注损伤并不全面.     

人工血管移植修复肢体血管缺损及临床观察

目的 总结应用人工血管移植修复技体血管闭塞及缺损的临床效果。方法 1992年6月-2000年12月，采用Gore-Tex膨胀泡沫聚四氟乙烯（ePTEE）人工血管移植修复肢体动脉及静脉缺损，动-静脉造瘘及复合皮瓣移植，神经移植共65例。结果 创伤性下肢肢体人工血管移植有1例行截肢术，桡动脉重建档中有3例闭塞，1例血管旁路重建术后3d并发急性心肌梗死而死亡，其余血管移植后肢体液血循环良好。术后行彩色多普勒检查、螺旋CT及DSA造影显示血管通畅。动-静脉造瘘28例全部成功，全部患者在临床上定期进行血液透析。随访2-5年，血管通畅率为71%。结论 人工血管移植修复肢体血管缺损、血管旁路术及动-静脉造瘘是一种有效的手术方式。既能解决自体血管来源困难的难题，又能保证临床应用的效果。     

Cardiac troponin T release during coronary surgery using intermittent cross-clamp with fibrillation, on-pump and off-pump beating heart.

OBJECTIVE: Troponin T is a unique marker which might be particularly useful in assessing myocardial cell damage in patients undergoing cardiac surgery. The aim of the study was a comparison between intra-operative release of troponin T (TnT) during three different myocardial protection strategies. METHODS: Thirty-eight PTS undergoing myocardial revascularization were randomised into 3 groups in whom procedure was performed with intermittent cross-clamp (Group I; n = 13), beating-heart on pump without aortic cross-clamp (Group II; n = 12), beating-heart without use of extracorporeal circulation (Group III; n = 13). Serial venous blood samples were collected for TnT measurement prior surgery, 1, 4, 12, 24, 48, 72 h after the procedure. Haemodynamic measurements were made using a thermodilution PA catheter. RESULTS: The groups were similar with respect to age, sex, preoperative LV function, number of grafts, potential risk factors. There were no hospital deaths and no myocardial infarction (MI) in three groups, postoperative haemodynamic measurements showed no significant differences. TnT serum levels were significantly higher in group I when compared to groups II and III. TnT levels were significantly lower in group Ill when compared to group II following 48-h post-operation. CONCLUSIONS: Coronary bypass grafting without aortic cross-clamping and without CPB offers superior myocardial protection.     

Effects of artificial circulation by pulsatile and non-pulsatile flow on brain tissues.

We examined the effects of artificial circulation by pulsatile and non-pulsatile flow on microcirculation in the brain from the viewpoints of circulation and metabolism in the brain. A centrifugal pump was fixed in the bypass in the right heart of 10 pigs. In 5 of the 10 pigs, a pulsatile flow pump was fixed in the bypass in the left heart (P group), and in the remaining 5 pigs, a centrifugal pump was fixed in the bypass in the left heart (NP group). Hemodynamics were periodically monitored for 3 hours while maintaining about 100 mmHg of the mean aortic pressure. Intracranial pressure (ICP), cerebral tissue blood flow and cerebral blood flow (CBF) were measured and compared with the initial values. As the parameters of metabolism in the brain, the cerebral oxygen consumption and lactic acid - pyruvic acid ratio were evaluated. If the cerebral blood flow was reduced by cardiogenetic shock, we suggest that blood circulation and metabolism in the brain were maintained by artificial circulation. It also indicated that there was no significant difference in blood circulation and metabolism in the brain between artificial pulsatile and non-pulsatile flow circulation.     

Nicardipine for preservation of myocardial metabolism and function in patients undergoing coronary artery surgery

The present study was designed to evaluate the myocardial protective effect of nicardipine (NIC) in patients with normal left ventricular (LV) function (control vs. NIC treatment group) and impaired LV function (control vs. NIC treatment group) during extracorporeal circulation for coronary artery surgery. NIC infusions were begun approximately 12 min before aortic cross clamping (AoX) at an infusion rate of 5 micrograms.kg-1.min-1 and maintained for 10 min. Prior to AoX an additional bolus of NIC 5 mg was given. Coronary hemodynamics, myocardial metabolic parameters (continuous thermodilution), and regional LV function (two-dimensional transesophageal echocardiography) were measured. At 15 min after discontinuation of AoX, lactate production was found in the two control groups but not in the two NIC treatment groups. In the control groups, lactate production returned to extraction at sternal closure. At that time regional area ejection fraction (RAEF) had significantly improved in both groups with impaired LV function compared with postintubation (baseline) values. In NIC-treated patients with impaired LV function, however, the percentage improvement in RAEF was significantly greater than that in the control groups. Between the groups, there were no differences in the number of patients requiring inotropic support, pacing, and/or diuretics after bypass or postoperatively. There were no significant differences in postoperative creatine kinase myocardial band release or in the incidence of dysrhythmias, myocardial infarction, or mortality. The results of the present study suggest that NIC iv may be used to provide additional myocardial protection during extracorporeal circulation. In addition, in NIC-treated patients with compromised LV function, this may be associated with a more apparent improvement in RAEF than that seen in nontreated patients.     

Long-term circulatory maintenance with a left-sided single artificial heart.

The purpose of this study is to examine the feasibility of long-term circulatory maintenance with only a left-sided single artificial heart that is inserted between the left atrium and the aorta to assist a nonfunctioning heart. The basic hemodynamics were determined in short-term experiments in goats (n = 4), and feasibility studies of long-term circulatory maintenance with a single artificial heart during cardiac arrest were performed in long-term experiments (n = 12). When pulmonary vascular resistance was less than 15,000 dynes .sec.cm-5.kg, which was twice the normal value, the circulation was well maintained with the single artificial heart alone, so long as the right atrial pressure was kept at 14 to 16 mm Hg. Under such conditions the flow yielded by the single artificial heart fluctuated between 80 and 140 ml/kg/min depending on the animal's demand, while the mean arterial pressure was kept above 80 mm Hg. The goats behaved normally, although retention of pleural effusion was a serious problem in maintaining normal circulation over a long-term. Maintaining the plasma total protein level above 6.0 gm/dl delayed the onset of retention or even prevented pooling of pleural effusion. The longest survival period to date has been 38 days. We conclude that when the pulmonary vascular resistance is less than twice the normal value and the total protein level is above 6.0 gm/dl, a left-sided single artificial heart alone can maintain normal circulation and provide time for patients with a nonfunctioning heart to undergo a further treatment, such as heart transplantation.     

Perioperative myocardial injury in patients undergoing aortic valve replacement

In cases of myocardial hypertrophy myocardial protection may be insufficient. In order to determine the factors responsible for myocardial injury we assessed myocardial injury in 54 patients undergoing isolated aortic valve replacement. In all cases hypothermic cardioplegic arrest was induced. At 13 different times we measured the serum level of creatine-kinase (CK), myocardial bound creatine-kinase (CKmb), lactic dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (alpha-HBDH), glutamic oxaloacetic transferase (GOT) and myoglobin. The mean duration of ischemia was 52.6 +/- 16.2 minutes and the mean time of extracorporeal circulation was 85.85 +/- 20.25 minutes. By performance of a multiple regression analysis a significant correlation between ischemia and LDH and alpha-HBDH was found; CK, GOT, LDH and alpha-HBDH correlated with duration of extracorporeal circulation. In none of the patients was a low cardiac output syndrome observed. From our results we conclude that in our study myocardial protection was sufficient and therefore the detrimental effects of extracorporeal circulation were the determining factors of enzyme release.     

Effect of a hybrid artificial pancreas in totally pancreatectomized dogs

This study was undertaken to estimate the effect of hybrid artificial pancreas (HAP) containing xenogeneic hamster islets in totally pancreatectomized dogs. HAP were attached either to the systemic circulation or to the portal circulation for 12 to 24 hours in totally pancreatectomized dogs. Following the systemic attachment of HAP containing 10,000 islets, in four out of 6 dogs the plasma glucose levels decreased to normoglycemic levels within 5.8 +/- 1.3 hours and thereafter maintained within normal range at least 12 hours until the removal of HAP. When HAP containing 10,000 islets were attached to the portal circulation, no decrease in the plasma glucose levels was observed in all four dogs. However, HAP containing 14,000 islets were able to restore normoglycemia in four out of 5 dogs within 7.0 +/- 1.6 hours after the portal attachment. No significant difference in the plasma glucose level was observed between the dogs with HAP containing 10,000 islets attached to the systemic circulation and those with HAP containing 14,000 islets attached to the portal circulation. Those results suggested that the systemic circulation, concerning with the quantity of the islets, was the superior site of the attachment of HAP to the portal circulation for controlling hyperglycemia in apancreatic dogs.     

Increasing operability and survival with intra-aortic ballon pump assist.

Intra-aortic ballon pump assist (IABPA) was used over a 12-month period in the management of 41 patients: 5 patients with complications of myocardial infarction in shock whose circulation was supported by IABPA before operation immediately after angiographic and hemodynamic study (group 1); 14 patients with postcardiotomy low-output state who could not be weaned from cardiopulmonary bypass and required IABPA circulatory support either in the operating room or in the intensive care area (group 2); 19 patients with severe myocardial ischemia and unstable circulation in whom IABPA was instituted either before angiography or before saphenous vein bypass operation (group 3); and 3 patients with severe left ventricular dysfunction and left ventricular hypertrophy due to aortic valve or coronary artery disease, or both, in whom IABPA was used before, during and after cardiopulmonary bypass and a corrective operative procedure (group 4). Survival rates for patients in these groups were 2/5,8/14,18/19 and 2/3 respectively (overall survival, 73%). IABPA may increase the postoperative survival of certain high-risk patients with poor left ventricular function due to valvular disease or coronary artery disease, or both. The survival of patients with severe myocardial ischemia and complicated myocardial infarction is improved by IABPA, early angiography and appropriate surgical correction. Left ventricular ejection fraction and the estimate of subendocardial coronary flow by the ratio of the diastolic pressure time index to the tension time index appear to be significant in identifying patients who may benefit from the use of IABPA.     

Influence of Ventricular Fibrillation on Sympathetic Nerve Activity Under Biventricular Bypass Circulation

Abstract: Autonomic nerves play an important role in circulatory control. The characteristics of sympathetic nerve activity (SNA) during artificial circulation, however, are not well understood. In this study, we examined the influence of natural heart beating on the renal SNA (RSNA) using pulsatile 100% biventricular assistance and electrically induced ventricular fibrillation in anesthetized goats, whose heart rate and size are similar to the human heart's. Following induction of the ventricular fibrillation, the pulse-synchronous discharges in the RSNA did not change their periodicity and quantity significantly. It was concluded that the beating of the heart had little influence on the RSNA and was presumably not essential for maintaining nervous control of circulation as long as the circulation was maintained by an artificial heart.     

Surgical simulation of cerebral revascularization via skull base approaches in the posterior circulation using three-dimensional skull model with artificial brain and blood vessels

Posterior circulation revascularization is a challenging technique because microanastomosis must be performed in deep locations. A reproducible simulation model is proposed for training. The prototype three-dimensional skull model with artificial brain was used. The mesencephalic segment of superior cerebellar artery (SCA) and the caudal loop of the posterior inferior cerebellar artery (PICA) were made from artificial blood vessels and glued on the brain. The skull model was drilled to perform the presigmoid transpetrosal approach and then superficial temporal artery-SCA anastomosis was performed under the operating microscope. The skull model was also drilled to perform the far lateral approach and then occipital artery-PICA anastomosis was performed. The skull model with artificial brain and arteries allows simulation and training in the surgical techniques of posterior circulation revascularization with skull base approaches.     

气管切除术麻醉及手术方式探讨

目的探讨不同气管疾病气管切除的麻醉和手术方式。方法回顾性分析18例气管切除手术的临床资料,分析麻醉和手术方法的选择及其与结果的关系。结果局部麻醉(局麻)气管切开插管麻醉2例,经气管造口插管麻醉2例,体外循环2例,气管插管全身麻醉12例,全组无麻醉和手术死亡。局部切除3例,节段性切除15例,气管切除最长8,0cm。节段性切除后一期吻合8例．记忆合金网二期成形人工气管7例,人工气管长度3．0—5．0cm。随访5个月-8年,4例因肿瘤等原因分别死于术后4,11及12个月,其余均生存。结论气管切除的麻醉与手术方式因人而异,高危患者可以体外循环,或者局麻下气管切开插管;开胸后切开气管或右主支气管,行左主支气管插管是有效、安全的麻醉方法。全身状况差者可仅行局部切除,切除气管小于5cm者可行节段性切除一期吻合,大于5.5cm者,可以用记忆合金网二期成形人工气管重建气管缺损。     

Intraoperative ischemia and long-term events after minimally invasive coronary surgery

Background

Concern has been raised about the effects of prolonged left anterior descending (LAD) artery occlusion during minimally invasive direct coronary artery bypass graft surgery (MIDCABG). We sought to assess the impact of myocardial dysfunction during MIDCABG on long-term outcome and the protective role of collateral circulation on myocardial ischemia.

Methods

Myocardial function was evaluated in 92 patients by intraoperative transesophageal echocardiography during MIDCABG.

Results

Wall motion score index increased during LAD occlusion (p < 0.00l) and reverted after LAD reopening (p < 0.001 versus occlusion and p = not significant versus baseline). The change in wall motion score index (occlusion versus baseline) was higher in patients with multivessel disease (p < 0.05) and in patients with LAD Thrombolysis in Myocardial Infarction study classification flow grade 2 or less without collateral circulation (p < 0.05). Myocardial stunning was documented in 12 patients (13%). The 5-year adverse event rate (including death, myocardial infarction, and revascularization) was 12%. By multivariate Cox regression analysis, multivessel disease, but not perioperative ischemia or stunning, was the only predictor of event-free survival.

Conclusions

During MIDCABG anterior wall dysfunction is transient, with prompt recovery after completion of the anastamosis in most cases; myocardial stunning can be documented in a minority of patients. Flow either antegrade or retrograde in the LAD territory plays a protective role against the development of ischemia. Multivessel disease, but not perioperative ischemia or stunning, predicts long-term event-free survival.