The importance of monitoring intramyocardial temperature during hypothermic myocardial protection.

In 50 patients undergoing cardiac operation, hypothermic cardioplegic solution was infused into the root of the aorta immediately after aortic cross-clamping. Cardiac standstill was achieved within 1 to 3 minutes. However, monitoring of intramyocardial temperature with a needle thermistor revealed that such core cooling is unpredictable (the intramyocardial temperature achieved ranged from 7 degrees to 33 degrees C), unstable (this temperature can rise at more than 0.5 degrees C per minute), and uneven (a difference of up to 17 degrees C was observed between the intramyocardial temperature of the anterior and posterior left ventricular sites). The area supplied by the stenotic coronary artery was least protected. Monitoring of intramyocardial temperature enables one to know when supplementary cooling is indicated. We conclude that widespread differences in this temperature during cardiac operation make monitoring advisable for optimal myocardial protection.     

Brain monitoring and protection during pediatric cardiac surgery

With advances in medical care, survival after cardiac surgery for congenital heart disease has dramatically improved, and attention is increasingly focused on long-term functional morbidities, especially neurodevelopmental outcomes, with their profound consequences to patients and society. There are multiple reasons for concern about brain injury. Some cardiac defects are associated with brain anomalies and altered cerebral blood flow regulation. Brain imaging studies have demonstrated that injury to gray and white matter is quite frequent before heart surgery in neonates. Cardiopulmonary bypass and deep hypothermic circulatory arrest are associated with short- and longer-term adverse neurologic outcome. Additional brain injury can occur during the patient's recovery from surgery. Strategies to optimize neurologic outcome continue to evolve. With new technological developments, perioperative neurologic monitoring of small children has become easier, and data suggest these modalities usefully identify adverse neurologic events and might predict outcome. Monitoring methods to be discussed include processed electroencephalography, near infrared spectroscopy, and transcranial Doppler ultrasound. Alternative perfusion techniques to deep hypothermic circulatory arrest have been developed, such as regional antegrade cerebral perfusion during cardiopulmonary bypass. Other neuroprotective strategies employed during open-heart surgery include temperature regulation, acid-base management, degree of hemodilution, blood glucose control and anti-inflammatory therapies. Evidence of the impact of these measures on neurologic outcome is examined, and deficiencies in our current understanding of neurologic function in children with congenital heart disease are identified.     

Preventive insulin administration for myocardial protection in cardiac surgery

The object of this study was to determine whether high doses of insulin administered preventively in combination with glucose and potassium exert a protective effect upon the myocardium. This approach should result in a preoperative accumulation of the myocardial glycogen stores with an increased anaerobic provision of energy-rich substrates (ATP) during coronary ischemia. Two comparable groups of seven dogs each, undergoing experimental extracorporeal circulation (ECC) with 90-min aortic cross-clamping were examined. Cardiac output (CO), systolic left ventricular blood pressure (pventr), left ventricular enddiastolic pressure (LVEDP), mean central venous pressure (CVP), and heart rate (HR) were recorded at left atrial (LA) pressures of 5, 10, 15, and 20 mmHg in order to construct ventricular function curves. These data were registered prior to the onset of ECC (preischemic value), after termination of ECC and after two 10-min periods of reperfusion. The first group served as control and the second group received high iv doses of insulin (total 25 U/kg) within 60 min prior to the onset of the ECC. In the control group, pventr and CO after termination of the ECC and after the first reperfusion were significantly (P less than 0.05) less than the preischemic values; after the second reperfusion they reached the preischemic range. In contrast, pventr and CO in the insulin group already were within the preischemic range at the termination of the ECC. After the first and the second reperfusion, CO was even greater than the preischemic value. LVEDP changed inversely, while CVP and HR showed no significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of normothermic systemic perfusion temperature on cold myocardial protection during coronary artery bypass surgery.

OBJECTIVE: To determine the effect of normothermic systemic perfusion on myocardial injury when using cold cardioplegic techniques in patients undergoing coronary artery bypass surgery. METHOD: Sixty six patients with stable angina pectoris were prospectively randomized into three groups according to cardiopulmonary bypass temperature: hypothermia (28 degrees C, n = 22), moderate hypothermia (32 degrees C, n = 22) and normothermia (37 degrees C, n = 22). All patients received cold antegrade crystalloid cardioplegia and topical cooling with saline at 4 degrees C. Serum samples were collected for troponin T and I estimation preoperatively, 4 hours after removal of the aortic cross clamp, and 12, 24, 36 and 48 hours postoperatively. In addition, serial electrocardiographic studies were undertaken on days 1, 3 and 5. RESULTS: Patients were similar with regard to preoperative and intraoperative characteristics Four patients showed ECG changes typical of perioperative myocardial infarction but remained clinically well (28 degrees C, one; 32 degrees C, one; 37 degrees C, two). In the remaining 62 patients, serum troponin T increased significantly from a mean baseline value of 0.02 ng/ml to 1.5+/-0.9 ng/ml 4 hours after removal of the aortic cross-clamp (P<0.0001). Similarly, troponin I increased from 0.06 ng/ml to 0.63+/-0.47 ng/ml 12 hours after reperfusion (P<0.0001). Serum concentrations of both markers subsequently declined with time but remained higher than preoperative values at 48 hours. There were no differences between the three groups with respect to peak and cumulative serum troponin release. Normothermic cardiopulmonary bypass did not compromise the efficacy of cold myocardial protection when assessed by serum troponin concentrations in low risk patients undergoing coronary revascularization.     

Role of creatine phosphate in myocardial protection in heart surgery

The Authors report their experience with the use of Creatine Phosphate (CP) in cardiac surgery. Forty patients undergoing mitral valve replacement are randomly divided into two groups: the former is treated with plain cardioplegia, the latter with CP-enriched cardioplegia at a concentration of 10 mmol/l. A sample of papillary muscle, obtained from the removed valve, is studied by means of spectrophotometric analysis in order to assess the enzyme activities and the intermediate metabolites of the different biochemical pathways of the myocardial cell. Our results suggest a possible interaction of exogenous CP with the cellular metabolism: all the mechanisms involved with the production of energy seem to be shifted towards a better preservation of the available pool of high-energy compounds.     

Adenosine in myocardial protection in on-pump and off-pump cardiac surgery

Adenosine is most well known for its potent vasodilation of the vasculature. However, it also promotes glycolysis, and activates potassium-sensitive adenosine triphosphate (K(ATP)) channels. Adenosine also strongly inhibits neutrophil function such as superoxide anion production, protease release, and adherence to coronary endothelial cells. Hence adenosine attenuates ischemic injury as well as neutrophil-mediated reperfusion injury. Adenosine has also been implicated in the cardioprotective phenomenon of ischemic preconditioning. Accordingly experimental evidence shows that adenosine reduces postischemic injury when administered before ischemia and at the onset of reperfusion. Clinical studies in cardiology and cardiac surgery show cardioprotective trends with adenosine treatment but the effects are not as dramatic as those reported by experimental studies.     

Hepatic and renal protection during cardiac surgery

Hepatic injury in cardiac surgery is a rare complication but is associated with significant morbidity and mortality. A high index of suspicion postoperatively will lead to earlier treatment directed at eliminating or minimizing ongoing hepatic injury while preventing additional metabolic stress from ischemia, hemorrhage, or sepsis. The evidence-basis for perioperative renal risk factors remains hampered by the inconsistent definitions for renal injury. Although acute kidney injury (as defined by the Risk, Injury, Failure, Loss, End-stage criteria) has become accepted, it does not address pathogenesis and bears little relevance to cardiac surgery. Although acute renal failure requiring renal replacement therapy after cardiac surgery is rare, it has a devastating impact on morbidity and mortality, and further studies on protective strategies are essential.     

On-line measurement of gas-exchange during cardiac surgery

This paper describes an on-line system for continuously monitoring expired CO2 during controlled ventilation. Signals from a Servo ventilator 900B or C and a CO2 Analyzer 930 are processed and corrected by the computer to produce a CO2 single breath test (SBT-CO2). This is the tracing of expired CO2 concentration or fraction against expired volume, from which the computer calculates the airway deadspace (VDaw). If a value for arterial PCO2 is supplied, the computer will calculate the physiological deadspace (VDphys) and the alveolar deadspace (VDalv) for each breath. The system was used to make measurements at four stages during coronary artery by-pass grafting in 13 male patients. When the sternum was opened there was a 32% increase in VDaw, and the physiological deadspace fraction therefore increased. There were reductions in VDaw after extra-corporeal circulation and again after sternal suture. By the end of surgery, the alveolar deadspace fraction had increased significantly. VDaw at this stage was smaller than pre-operatively, and so there was no net change in the physiological deadspace fraction at the end of surgery. Arterial PO2 was, however, reduced at this stage.     

术中核心温度监测研究进展

背景 随着对术中和术后体温相关并发症的深入认识,术中核心温度监测逐渐受到人们的关注. 目的 探讨体温监测在手术中的应用,为临床应用带来理论支持. 内容 综述体温监测意义以及不同的体温监测方法和监测位置.趋向 寻找更加精确、安全无创并且容易监测的核心温度监测技术.     

重视脊柱外科手术中的神经电生理监护

近年来,随着我国脊柱外科的长足发展,特别是脊柱内固定技术和各类先进手术器械的普及,脊柱外科手术得以在全国各类医院中广泛开展,但随之而来的是脊柱手术中脊髓损伤和神经损伤的增加。应用术中神经电生理监护是防止医源性脊髓和神经损伤的一种重要技术手段,     

On-line metabolic monitoring of the heart during cardiac surgery

A new system for the on-line monitoring of intramyocardial pH and temperature has been used in more than 120 patients undergoing cardiac surgery. This article summarizes the experimental studies on which the system was based and highlights some of the data obtained and explains their significance.     

Real-time monitoring of cardiac metabolism using biosensors shows myocardial protection during ischemia-reperfusion injury with glucose-insulin-potassium administration

BACKGROUND: Systemic infusion of glucose-insulin-potassium (GIK) is thought to confer myocardial protection during ischemia-reperfusion injury. Our laboratory has experience with real-time monitoring of glucose and pH levels using needle-mounted biosensors. We tested the hypothesis that GIK enhances myocardial metabolism as displayed by real-time myocardial metabolic monitoring. METHODS: A total of 40 kg male swine were randomized to receive GIK (n = 7) or lactated Ringer's (n = 7) solution intravenously at 1.5 mL/kg/hour. Ischemia was induced in the left anterior distribution (LAD) by 20 minutes LAD occlusion, followed by 20 minutes reperfusion. Hearts were instrumented anteriorly and posteriorly with continuously recording myocardial pH and glucose biosensors. Biopsies from the LAD distribution were taken at baseline, maximum ischemia, and after reperfusion to assess cardiac adenosine triphosphate (ATP) levels. RESULTS: GIK animals had less myocardial pH decrease than controls during both ischemia (pH decrease -0.03 vs -0.37, P = .04) and reperfusion (pH decrease -0.10 vs -0.44, P = .05). Neither ATP (74% vs 73% decrease from baseline) nor glucose (27% vs 33% decrease from baseline) varied significantly between groups during ischemia. GIK animals had faster normalization of ATP (100% vs 79% increase from ischemia) and glucose (69% vs 28% increase from ischemia) during reperfusion. CONCLUSIONS: Real-time myocardial metabolic monitoring shows that cardiac pH is improved by GIK during ischemia-reperfusion injury; however, ATP and glucose levels were not significantly enhanced. GIK animals trended toward earlier recovery during reperfusion. Mediators of this metabolic enhancement need to be explored.     

Determinants of regional myocardial acidosis during cardiac surgery

BACKGROUND: Intraoperative regional myocardial acidosis (RMA) during cardiac surgery has been shown to be reflective of regional myocardial ischemia and an independent predictor of adverse postoperative outcomes. This study identifies the determinants of intraoperative RMA. METHODS: Intramyocardial tissue pH(37C) in the anterior and posterior LV walls was measured in 641 adult patients during cardiac surgery. RMA at two intraoperative periods was quantified as integrated mean pH(37C) < 6.35 during aortic clamping (AC) and pH(37C) < 6.73 at the end of cardiopulmonary bypass (CPB). These pH thresholds were chosen because of their demonstrated relationship to long-term patient survival. Multivariate logistic regression models were constructed. An acidosis prediction score was constructed based on the factors determining RMA at the end of CPB. RESULTS: Independent determinants of RMA during AC were preoperative New York Heart Association class III/IV (P = .007), current smoker (P = .0088), pH(37C) < 6.63 prior to AC (P < .0001), and intraoperative myocardial management technique (P = .0001). Independent determinants of RMA at end of CPB were ASA class IV/V (P = .0042), pH(37C) < 6.63 prior to AC (P = .035), pH(37C) < 6.35 during AC (P = .001), and total duration of CPB > or = 212 minutes (P = .001). CONCLUSIONS: RMA during cardiac surgery is determined by patient risk factors, the magnitude of preceding regional myocardial acidosis, and the duration of CPB.     

Endoscopic monitoring of operative procedures during cardiac surgery

Both intracardiac repair and fine anastomotic procedures are hard to visualize in the sterile operative field. To overcome this problem, we have recently developed an endoscope video system for intraoperative monitoring in open heart surgery. The endoscope can be introduced into the cardiac cavity in a sterile fashion and thus be used to visualize intracardiac lesions as well as the operative procedures. This endoscopic video monitoring system is considered to be useful not only for thoracic surgery but also for cardiac surgery as well. A preliminary report of this work was presented at the 95th Annual Congress, Japan Surgical Society, 10 April 1995, Nagoya, Japan     

Aprotinin and hemostasis monitoring concerns during cardiac surgery

Aprotinin (Trasylol) is a serine protease inhibitor, isolated from bovine lung that initially was marketed for the treatment of pancreatitis. In the mid 1980s, reports of its ability to decrease hemorrhaging after cardiopulmonary bypass surgery introduced the drug to the realm of cardiac surgery. Unfortunately, its introduction into this arena was followed by the publication of multiple studies and case reports that blamed aprotinin for poor outcomes in the form of early graft closure. More than 17 years have passed since the initial article describing the use of aprotinin during cardiopulmonary bypass, and with time there has been a significant increase in scientific knowledge and clinical experience. Interestingly, modern literature does not support the dogma that aprotinin is a procoagulant. Aprotinin increases the activated partial thromboplastin time (aPTT), as well as the kaolin- and celite-activated clotting time (ACT), regardless of heparin. Aprotinin, because of its ability to inhibit kallikrein, has been found to decrease thrombin antithrombin III complexes, fibrin-split products, fibrinopeptide 1+2, prothrombin fragments, and all markers of thrombin formation. Some authors have suggested that it may have a synergistic effect with heparin to ensure graft patency. Anticoagulation monitoring during the use of aprotinin also has been developed based on early studies. Aprotinin administration does influence the results of various ACT tests, and consequently different methods of testing anticoagulation have been developed. Researchers have demonstrated that the celite ACT is not "artificially" prolonged in the presence of heparin and aprotinin, rather the kaolin ACT is "artificially" shortened. This article will review the scientific literature with regard to aprotinin's anticoagulatory effects and review the current recommendations for hemostasis monitoring during the use of aprotinin.