Corrective Open Heart Surgery Research Articles

A comparison of high thoracic epidural anaesthesia versus conventional intravenous opioids in pediatric patients undergoing corrective open heart surgery for ventricular septal defect

Background: We compared high thoracic epidural anaesthesia with a combination of morphine and bupivacaine versus IV fentanyl as an alternative for perioperative pain management.Methods: Group-E: Injection Morphine 75-100 mcg/kg and Injection 0.25 % Bupivacaine 0.5 ml/kg was given via epidural catheter at insertion, Injection 0.25% Bupivacaine 0.5 ml/kg just before skin incision, and continuous infusion of Injection 0.125% Bupivacaine at 0.2 ml/kg/hr intra-operatively. Post-operative 0.1 ml/kg/hr infusion. Group F- intravenous fentanyl 2-3 mcg/Kg IV bolus given just before skin incision, followed by 1-2 mcg/Kg/hr IV fentanyl started after weaning from cardiopulmonary bypass.Results: The mean ScvO2 was comparable between the two groups during induction period but became higher in group E during bypass and post bypass period intraoperatively, and the difference in rise in ScvO2 is statistically significant with a p<0.05. The mean rSo2- C was comparable between the two groups in the first postoperative hour but group F shows higher rSo2-C postoperatively which was statistically significant. The postoperative pain was significantly lower in group E in the postoperative period (except for 4,5,6 and 40 and 48th hour).Conclusions: HTEA to paediatric patients prior to sternotomy for cardiac surgeries resulted in a much better control of haemodynamic parameters. Produces better central venous and regional tissue oxygenation during bypass and post bypass intraoperatively as compared to the patients that received only intravenous fentanyl. There was lower amount of postoperative bleeding in the HTEA group with significant reduction in requirement of post-operative ventilation and time to extubation after surgery, better post-operative pain control and overall outcome.

Usefulness of intraoperative bronchoscopy during surgical repair of a congenital cardiac anomaly with possible airway obstruction: three cases report.

Compression of the airway is relatively common in pediatric patients, although it is often an unrecognized complication of congenital cardiac and aortic arch anomalies. Aortopexy has been established as a surgical treatment for tracheobronchial obstruction associated with vascular anomaly, aortic arch anomaly, esophageal atresia, and tracheoesophageal fistula. The tissue-to-tissue arch repair technique could result in severe airway complication such as compression of the left main bronchus which was not a problem before the correction. We report three cases of corrective open heart surgery monitored by intraoperative bronchoscopy performed during prebypass, and performed immediately before weaning from bypass, to evaluate tracheobronchial obstruction caused by congenital, complex cardiac anomalies in the operating room.

Alveolar recruitment manoeuvre is safe in children prone to pulmonary hypertensive crises following open heart surgery: a pilot study

To test the tolerance and safety of an alveolar recruitment manoeuvre performed in the immediate postoperative period of corrective open heart surgery in children with congenital heart disease associated with excessive pulmonary blood flow and pulmonary arterial hypertension due to left-to-right shunt. Ten infants aged 1-24 months with congenital heart disease associated with excessive pulmonary blood flow and pulmonary artery hypertension (mean pulmonary artery pressure ≥ 25 mmHg) were evaluated. The alveolar recruitment manoeuvre was performed in the operating theatre right after skin closure, and consisted of three successive stages of 30 s each, intercalated by a 1-min interval of baseline ventilation. Positive end-expiratory pressure was set to 10 cmH2O in the first stage and to 15 cmH2O in the two last ones, while the peak inspiratory pressure was kept at to 30 cmH2O in the first stage and at 35 cmH2O in the latter ones. Haemodynamic and respiratory variables were recorded. There was a slight but significant increase in mean pulmonary artery pressure from baseline to Stage 3 (P = 0.0009), as well as between Stages 1 and 2 (P = 0.0001), and 1 and 3 (P = 0.001), with no significant difference between Stages 2 and 3 (P = 0.06). Upon completion of the third stage, there were significant increases in arterial haemoglobin saturation as measured by pulse oximetry (P = 0.0009), arterial blood partial pressure of oxygen (P = 0.04), venous blood oxygen saturation of haemoglobin (P = 0.03) and arterial oxygen partial pressure over inspired oxygen fraction ratio (P = 0.04). A significant reduction in arterial blood partial pressure of carbon dioxide (P = 0.01) and in end tidal carbon dioxide also occurred (P = 0.009). The manoeuvre was well tolerated and besides a slight and transitory elevation in mean pulmonary artery, no other adverse haemodynamic or ventilatory effect was elicited. The alveolar recruitment manoeuvre seemed to be safe and well tolerated immediately after open heart surgery in infants liable to pulmonary hypertensive crises.

Ventilation and cardiac related impedance changes in children undergoing corrective open heart surgery

Electrical impedance tomography (EIT) can determine ventilation and perfusion relationship. Most of the data obtained so far originates from experimental settings and in healthy subjects. The aim of this study was to demonstrate that EIT measures the perioperative changes in pulmonary blood flow after repair of a ventricular septum defect in children with haemodynamic relevant septal defects undergoing open heart surgery. In a 19 bed intensive care unit in a tertiary children's hospital ventilation and cardiac related impedance changes were measured using EIT before and after surgery in 18 spontaneously breathing patients. The EIT signals were either filtered for ventilation (ΔZV) or for cardiac (ΔZQ) related impedance changes. Impedance signals were then normalized (normΔZV, normΔZQ) for calculation of the global and regional impedance related ventilation perfusion relationship (normΔZV/normΔZQ). We observed a trend towards increased normΔZV in all lung regions, a significantly decreased normΔZQ in the global and anterior, but not the posterior lung region. The normΔZV/normΔZQ was significantly increased in the global and anterior lung region. Our study qualitatively validates our previously published modified EIT filtration technique in the clinical setting of young children with significant left-to-right shunt undergoing corrective open heart surgery, where perioperative assessment of the ventilation perfusion relation is of high clinical relevance.

The Vasoactive-Inotropic Score and Levosimendan: Time for LVIS?

Three recent randomized controlled trials1Momeni M. Rubay J. Matta A. et al.Levosimendan in congenital cardiac surgery: A randomized, double-blind clinical trial.J Cardiothorac Vasc Anesth. 2011; 25: 419-424Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar, 2Ricci Z. Garisto C. Favia. I et al.Levosimendan infusion in newborns after corrective surgery for congenital heart disease: Randomized controlled trial.Intensive Care Med. 2012; 38: 1198-1204Crossref PubMed Scopus (43) Google Scholar, 3Lechner E. Hofer A. Leitner-Peneder G. et al.Levosimendan versus milrinone in neonates and infants after corrective open-heart surgery: A pilot study.Pediatr Crit Care Med. 2012; ([Epub ahead of print])PubMed Google Scholar evaluated the safety and efficacy of levosimendan in children with congenital heart disease undergoing cardiac surgery. All these papers concluded that levosimendan was safe and contributed to improvement of cardiac function and inotropic support optimization. From these initial experiences following levosimendan use in adult critically ill patients, indications for this drug in the pediatric setting is expected to increase. Recently, Davidson et al4Davidson J. Tong S. Hancock H. et al.Prospective validation of the vasoactive-inotropic score and correlation to short-term outcomes in neonates and infants after cardiothoracic surgery.Intensive Care Med. 2012; 38: 1184-1190Crossref PubMed Scopus (123) Google Scholar prospectively compared the vasoactive-inotropic score (VIS) and inotrope score in infants after cardiovascular surgery, as mathematical measures for evaluating vasoactive drug administration, and, consequently, the hemodynamic condition of patients. At all assessed time points, VIS was shown to be more predictive of poor short-term outcome than inotrope score. Interestingly, the authors observed that from a clinical perspective, a high VIS at 48 hours postoperatively achieved the best performance as a predictor for poor outcome. VIS is calculated as dopamine dose (mcg/kg/min)+dobutamine dose (mcg/kg/min)+100×epinephrine dose (mcg/kg/min)+10×milrinone dose (mcg/kg/min)+10,000×vasopressin dose (U/kg/min)+100×norepinephrine dose (mcg/kg/min). We noticed that levosimendan is not currently included in the VIS calculation. In our opinion, the time has come for a modified version of VIS also including levosimendan input in the formula (levosimendan VIS [LVIS]). It should be mentioned that the hypothetical application of levosimendan to the VIS formula should be prolonged for a week (3 or 4 days after the drug infusion has been stopped, due to its prolonged metabolite activity). We propose to include levosimendan with a factor of 50 (to achieve a contribution to VIS similar to milrinone); milrinone 0.5 to 1 mcg/kg/min has a VIS weight from 5 to 10. Similarly, a levosimendan dose of 0.1 to 0.2 mcg/kg/min would achieve a LVIS formula weight of 5 to 10. We tried to apply this concept to a recent study from our group2Ricci Z. Garisto C. Favia. I et al.Levosimendan infusion in newborns after corrective surgery for congenital heart disease: Randomized controlled trial.Intensive Care Med. 2012; 38: 1198-1204Crossref PubMed Scopus (43) Google Scholar and found that the significant VIS differences between the levosimendan group and controls would change dramatically; significant LVIS differences are not present between the 2 groups (Fig 1A and B). We suggest authors and reviewers take into account the following LVIS in future pediatric papers dealing with levosimendan: LVIS = dopamine dose (mcg/kg/min)+dobutamine dose (mcg/kg/min)+100×epinephrine dose (mcg/kg/min)+10×milrinone dose (mcg/kg/min)+10,000×vasopressin dose (U/kg/min)+100×norepinephrine dose (mcg/kg/min)+50×levosimendan dose (mcg/kg/min).

Levosimendan versus milrinone in neonates and infants after corrective open-heart surgery

Low cardiac output syndrome commonly complicates the postoperative course after open-heart surgery in children. To prevent low cardiac output syndrome, prophylactic administration of milrinone after cardiopulmonary bypass is commonly used in small children. The aim of this study was to compare the effect of prophylactically administered levosimendan and milrinone on cardiac index in neonates and infants after corrective open-heart surgery. Prospective, single-center, double-blind, randomized pilot study. Tertiary care center, postoperative pediatric cardiac intensive care unit. After written informed consent, 40 infants undergoing corrective open-heart surgery were included. At weaning from cardiopulmonary bypass, either a 24-hr infusion of 0.1 μg/kg/min levosimendan or of 0.5 μg/kg/min milrinone were administered. Cardiac output was evaluated at 2, 6, 9, 12, 18, 24, and 48 hrs after cardiopulmonary bypass using a transesophageal Doppler technique (Cardio-QP, Deltex Medical, Chichester, UK). Cardiac index was calculated from cardiac output and the patients' respective body surface area. Intention-to-treat data of 39 patients (19 in the levosimendan and 20 in the milrinone group) were analyzed using analysis of variance for repeated measurements for statistics. Analysis of variance revealed for both, cardiac index and cardiac output, similar results with no significant differences of the factors group and time. A significant interaction for cardiac output (p = .005) and cardiac index (p = .007) was found, which indicates different time courses of cardiac index in the two groups. Both drugs were well tolerated; no death or serious adverse event occurred. In our small study, postoperative cardiac index over time was similar in patients with prophylactically administered levosimendan and patients with prophylactically given milrinone. We observed an increase in cardiac output and cardiac index over time in the levosimendan group, whereas cardiac output and cardiac index remained stable in the milrinone group. This pilot study has primarily served to obtain experience using the new drug levosimendan in neonates and infants and to initiate further multicenter trials in pediatric patients.

Right atrial mass after open heart surgery: tumour or thrombus?

Detection of a rapidly growing mass in the right atrium during routine inter-echocardiogram follow-up period in two patients after corrective open-heart surgery raises concerns about nature of the mass and the probable cause. One turned out to be an atrial myxoma that grew rapidly over a eight month period and the other a well encapsulate thrombus in a fully anticoagulated patient. Preoperative transthoracic echocardiogram had reported both the cases to be a myxoma. This article highlights the importance of considering rare causes in the face of a seemingly obvious diagnosis and possible use of imaging modalities in the management of these cases.

Mechanical Circulatory Support to Control Medically Intractable Arrhythmias in Pediatric Patients After Cardiac Surgery

Postoperative intractable arrhythmia can result in high morbidity and mortality. This report describes our experiences using mechanical circulatory support (MCS) to control medically intractable arrhythmias in three pediatric patients with congenital heart disease (CHD), after palliative or total corrective open-heart surgery.

Anesthetic management for resection of cor triatriatum during the second trimester of pregnancy

Hemodynamic changes during pregnancy can result in cardiovascular decompensation in women with pre-existing cardiac diseases. Despite optimized medical treatment, some patients with severe structural cardiac abnormalities may need surgical intervention during pregnancy. We describe a woman who presented at 20 weeks of gestation with acute heart failure due to cor triatriatum, a rare form of congenital heart disease. This condition is characterized by a perforated fibromuscular membrane dividing the left atrium into two chambers. The clinical presentation varies from asymptomatic to acute heart failure depending on the size of the fenestrations in the membrane and the presence of associated cardiac malformations. In our patient, two severely restrictive orifices in a membrane within the left atrium, moderate to severe pulmonary hypertension and good biventricular function were demonstrated by transthoracic echocardiography. Without surgical resection, the increased blood volume and cardiac output associated with pregnancy could have resulted in cardiovascular decompensation. She underwent urgent corrective open heart surgery with cardiopulmonary bypass. Perioperative anesthetic management included prevention of tachycardia, atrial dysrhythmias and pulmonary hypertension, close monitoring for and prompt treatment of maternal hypotension, maintaining euvolemia and good cardiac contractility and avoiding hemodilution and hypothermia. These approaches, together with minimizing bypass time, resulted in successful maternal and fetal outcome.

Human cardiac mesoangioblasts isolated from hypertrophic cardiomyopathies are greatly reduced in proliferation and differentiation potency

Our objective was to test whether progenitor cell proliferation and differentiation potential may vary depending upon the disease of the donor. Human cardiac mesoangioblasts were isolated from cardiac muscle biopsies of patients undergoing open heart surgery for correction of mitral regurgitation following an acute myocardial infarction (MR-MI) or correction of mitral and aortic regurgitation with ensuing left ventricular hypertrophy (MAR-LVH). The cells express surface markers and cardiac genes similar to mouse cardiac mesoangioblasts; they have limited self-renewing and clonogenic activity and are committed mainly to cardiogenesis. Although cardiac differentiation can be induced by 5-azacytidine or by co-culture with rat neonatal cardiomyocytes, human cells do not contract spontaneously like their mouse counterparts. When locally injected in the infarcted myocardium of immunodeficient mice, cardiac mesoangioblasts generate a chimeric heart that contains human myocytes and some capillaries; likewise, they colonize chick embryo hearts when transplanted in ovo. At variance with cells from patients with MR-MI, when isolation was performed on biopsies from MAR-LVH, cells could be isolated in much lower numbers, proliferated less extensively and failed to differentiate. Cardiac mesoangioblasts are present in the human heart but this endogenous progenitor population is progressively exhausted, possibly by continuous and inefficient regeneration attempts.

Effects of fresh versus old stored blood in the priming solution on whole blood lactate levels during paediatric cardiac surgery

It has been suggested that lactate levels may predict morbidity and mortality in paediatric patients during corrective open-heart surgery. Packed red blood cells (PRBC) are frequently necessary for priming the reservoir used in cardiopulmonary bypass (CPB). The storage of PRBC might cause a significant increase in lactate levels. The purpose of the present study was to quantify the increase in lactate levels in stored red blood cells over time and to compare lactate levels after transfusions of fresh (< or =12 days) versus old blood (>12 days) in 20 patients. We found an increase in lactate levels from 6.0 to 44.7mmol/L (mean 17.0+/-7.8 mmol/L) during storage. Lactate levels were also significantly higher after the onset of CPB in paediatric patients transfused with old blood than in patients transfused with fresh blood (1.43+0.36 versus 3.46+/-0.63, p=0.0006). Our results suggest that the higher lactate levels found after the initiation of CPB should be used with caution when assessing tissue hypoxia and predicting outcome.

Neurologic status of newborns with congenital heart defects before open heart surgery.

Controversy exists regarding the integrity of the nervous system in the newborn with a congenital heart defect who must undergo corrective or palliative open heart surgery. Neurodevelopmental sequelae have been primarily attributed to surgical procedures without standardized evaluation of the preoperative neurologic status. To determine whether newborns with congenital heart defects demonstrate abnormalities in neurobehavioral status before surgery. In this prospective study, a standardized neonatal neurobehavioral assessment and a neurologic examination were conducted independently in a consecutive series of 56 neonates referred to our hospital for investigation of open heart surgery. Neurobehavioral and neurologic abnormalities were documented in greater than half of the cohort and included hypotonia, hypertonia, jitteriness, motor asymmetries, and absent suck. Poor state regulation (62%) and feeding difficulties (34%) also were commonly observed. Furthermore, 3 subjects had seizures, 35.7% were microcephalic, and 12.5% were macrocephalic. The overall likelihood of neurobehavioral abnormalities was not enhanced by indicators of cardiorespiratory compromise. Interestingly, newborns with acyanotic congenital heart defects were more likely to demonstrate neurologic compromise than were those with cyanotic defects. Findings suggest that the prevalence of neurobehavioral abnormalities before surgery in newborns with congenital heart defects has been underappreciated and would indicate that factors other than intraoperative procedures should be considered in the genesis of brain injury in this population.congenital heart defects, neurologic examination, newborn.

LTE4 blood levels in infants with congenital heart lesions.

The cysteinyl-leukotrienes are metabolites of arachidonic acid via the 5-lipoxygenase pathway.1 These potent smooth muscle contractile agents are released from the human lung in vitro. 2,3 Since the cysteinyl-leukotrienes are potent vasoconstrictor agents in human pulmonary vessels, 4,5 these mediators may be responsible for pulmonary hypertension. Previous data have shown that infants with congenital heart lesions frequently have elevated pulmonary arterial pressure. In these patients, there are also acute transitory episodes of increased pulmonary arterial pressure following open heart surgery for correction of congenital heart lesions. Unfortunately, the circulating levels of leukotrienes in infants with pulmonary hypertension is not known. The aim of this study was to measure the LTE4 levels in the circulation of infants and to correlate these levels with the elevated pulmonary arterial pressure.

Bloodless open-heart surgery in infants and children.

Between October 1984 and January 1993, seven children of Jehovah's Witnesses underwent corrective open-heart surgery for congenital defects, on cardiopulmonary bypass (CPB). Age at surgery ranged from three months to 6.5 years, and weight ranged from 4.2 kg to 23.2 kg, with two children weighing less than 10 kg. The principal cardiac anomalies were tetralogy of Fallot (two), double outlet right ventricle (one), subaortic stenosis (one), transposition of the great arteries and ventricular septal defect (one), atrial septal defect and congenital heart block (one), and congenital mitral regurgitation (one). Hypothermic CPB was used in all seven operations with crystalloid priming of the extracorporeal circuit. CPB was based on our standard perfusion protocols. All surgical procedures were done without the use of blood or blood products. The mean preoperative haematocrit (Hct) was 40.9% (range 31.0-47.8%). The mean lowest intraoperative Hct was 17.3% (range 15.0-24.3%), whereas the immediate post-CPB Hct was 19.6% (range 15.3-24.0%). The Hct progressively increased to 29.2% (range 21.0-34.2%) on the first postoperative day, and 32.3% (range 24.2-38.3%) at the time of discharge. There was no hospital mortality, and the mean hospital stay was 10 days (8-13 days). We report the safe repair of complex open-heart surgery in children, without blood transfusion, even in small infants. The successful management of these patients requires meticulous attention to surgical and perfusion technique, and sound postoperative management.

Changes in calcium fractions during cardiopulmonary bypass in infants and neonates

The changes in total blood calcium fractions were investigated in 20 infants and neonates undergoing open-heart surgery for correction of congenital heart defects. On initiation of cardiopulmonary bypass (CPB), total serum calcium fell from 2.29 ± 0.05 mmol/I to 1.8 ± 0.04 mmol/I and there was a profound fall in biologically active ionized calcium from 1.26 ± 0.02 mmol/I to 0.49 ± 0.04 mmol/l. Protein-bound calcium also fell from 1.03 ± 0.07 mmol/I to 0.09 ± 0.03 mmol/l. Complexed calcium increased from 0.08 ± 0.02 mmol/I to 1.1 ± 0.05 mmol/l. The large fall in ionized calcium and increase in complexed calcium could be accounted for by the corresponding large increases in serum citrate (162.2 ± 29.8 μmol/l to 1689.8 ± 163.1 μmol/l) and serum lactate (1.27 ± 0.18 mmol/I to 7.79 ± 0.72 mmol/l). All measured fractions of calcium returned towards their pre-operative levels by the end of bypass. However, 13 of the 20 patients had less than optimal levels of ionized calcium when being weaned from bypass despite the empirical use of intravenous calcium supplements. This study demonstrates that ionized calcium can be quickly and easily measured in the peri-operative period, that there can be extremely large changes in calcium fractions during CPB in infants and neonates, and that ionized calcium can be unexpectedly low in the critical period when weaning patients from bypass. Total calcium measurements gave an inaccurate estimate of the ionized calcium fraction.

Pacemaker activity is modulated by tissue levels of cyclic adenosine 3′,5′-monophosphate in human atrial fibers

We studied the role of tissue cyclic AMP levels in the chronotropic effects of theophylline on automatic human atrial fibers obtained from the hearts of 17 patients undergoing corrective open-heart surgery. Atrial fibers were perfused with Tyrode solution and transmembrane action potentials were recorded with a conventional microelectrode technique. In normal Tyrode solution, theophylline (0.1–1 mM) often decreased the late diastolic slope and the spontaneous rate. In the presence of 0.3–1 μM epinephrine, however, theophylline dose-dependently increased the diastolic slope, the rate of spontaneous discharges and the force of contraction. The increase in tissue level of cyclic AMP (+288 ± 69%) induced by 0.3 mM theophylline in the presence of epinephrine was much greater than the increase (+73 ± 19%) in the absence of epinephrine. It is concluded that pacemaker activity in human atrial fibers is modulated by tissue levels of cyclic AMP and theophylline may induce atrial tachycardia through an increase in the diastolic slope and the rate of discharges of automatic atrial fibers.

Arrhythmogenic effects of theophylline in human atrial tissue

We studied the effects of theophylline on the transmembrane action potential and the contractile force of human atrial fibers obtained from the hearts of 15 patients, undergoing corrective open-heart surgery. Atrial fibers were perfused with Tyrode solution and driven electrically at a constant rate of 60 beats per min. Theophylline (0.1–1 mM) steepened the diastolic depolarization, increased the amplitude of oscillatory potential during diastole and facilitated the development of spontaneous slow response action potentials. These arrhythmogenic effects of theophylline were suppressed after diltiazem (0.1–0.3 μM) pretreatment. The present findings provide the electrophysiologic evidence that abnormal atrial automaticity as a result of triggered activity may be the underlying cause for atrial ectopic activity and multifocal atrial tachycardia in patients taking theophylline.

Metabolism and the electrical activity of human atrial myocardium.

The electrophysiological effects of hypoxia, glucose and iodoacetic acid (IAA) were studied in 16 preparations of human right atrial tissue obtained during corrective open heart surgery. During atrial pacing, transmembrane action potentials were recorded with intracellular micro-electrodes. Hypoxia caused predominant alterations in the repolarisation phase of the action potential including depression of the plateau and a decrease in duration associated with a shortening of the effective refractory period and an increase in the maximum atrial rate at which 1:1 conduction was still maintained. The maximum rate of rise was moderately reduced but the resting potential, action potential amplitude and conduction time were not significantly altered. The critical range of stimulus intervals at which inhomogeneity of conduction first occurred was shifted to shorter values. An increase in the extracellular glucose concentration from 5 to 50 mmol·litre−1 in the presence of persisting hypoxia reversed the anoxic effects. The action of IAA (7.5 × 10−5 mol·litre−1) alone on repolarisation resembled qualitatively that obtained with hypoxia but with a slower time course. The maximum rate of rise was not significantly altered. Combination of IAA with hypoxia rapidly abolished all atrial electrical activity. The results support the hypothesis that: (1) human atrial fibres can utilise both aerobic and glycolytic energy for maintenance of electrical activity; (2) under physiological extracellular glucose concentrations, either aerobic or glycolytic processes alone can provide sufficient energy to maintain the action potential amplitude but not the action potential plateau; and (3) stimulation of glycolysis by high extracellular glucose during hypoxia allows additional energy production that effectively contributes to the maintenance of the electrical activity of the human heart.

Electrophysiological study of human ventricular heart muscle treated with quinidine: interaction with isoprenaline.

We have investigated the effects of quinidine on the force of contraction and the intracellularly recorded action potential in papillary muscles isolated from human hearts. All preparations were obtained from patients undergoing corrective open heart surgery. The following results were obtained: (1) quinidine had a depressant effect on myocardial contractile force; (2) quinidine reduced the maximal upstroke velocity of the action potential; (3) quinidine shortened the plateau phase and prolonged the terminal repolarization of the action potential; (4) at higher concentrations quinidine reduced the resting potential; and (5) the depression by quinidine of both the plateau and the force of contraction was antagonized by isoprenaline. It is concluded that quinidine reduces the membrane conductances for sodium, calcium, and potassium ions. All of these actions of quinidine may contribute to the antiarrhythmic effects of the drug. The negative inotropic effect of quinidine can be explained by a depression of the calcium conductance at the myocardial cell membrane. The results show that earlier findings in laboratory animals regarding the effects of quinidine on the upstroke velocity and repolarization phase of the action potential are applicable to the human heart.

The effects of deep hypothermia and circulatory arrest on systemic metabolic state of infants undergoing corrective open heart surgery: a comparison of two methods.

Fortyone of 187 infants undergoing corrective surgery for their congenital cardiac lesions using profound hypothermic circulatory arrest were randomly selected for metabolic studies. Deep hypothermia of 21 to 22 degrees C core temperature was reached by two different techniques: 1. Perfusion cooling by extracorporeal circulation (ECC-C) 2. Surface cooling with ice bags combined with perfusion cooling (SC + ECC-C) After circulatory arrest (34.2 min. ECC-C v.s. 46.7 min. SC + ECC-C) bypass rewarming was used in both groups. The metabolic reaction to these interventions are described. No significant differences in acid base status in oxygen consumption, lactate concentration, serum electrolytes (K+, Na+, Ca++,Cl-) and serum enzyme activity (CPK, alpha-HBDH, LDH, SGOT, SGPT) could be demonstrated between the two groups of patients during the entire course of cooling, circulatory arrest and rewarming. The glucose concentration was significantly lower in the ECC-C group during the entire period of operation. Total cooling time was significantly shorter in the group without surface cooling. (ECC-C: 12 min, v.s. SC + ECC-C: 64 min). Since no favourable effects of the SC + ECC-C method on systemic metabolism could be demonstrated and operative results were similar we now prefer the time-saving ECC-C technique.