Bench-to-bedside review: Inotropic drug therapy after adult cardiac surgery -- a systematic literature review

Catecholamine and volume therapy for cardiac surgery in Germany--results from a postal survey

BACKGROUND

Management of cardiac surgery patients is a very standardized procedure in respective local institutions. Yet only very limited evidence exists concerning optimal indication, safety and efficacy of hemodynamic monitoring catecholamine and fluid therapy.

METHODS

Between April and May 2013, all 81 German anaesthesia departments involved in cardiac surgery care were asked to participate in a questionnaire addressing the institutional specific current practice in hemodynamic monitoring, catecholamine and volume therapy.

RESULTS

51 (63%) questionnaires were completed and returned. All participating centers used basic hemodynamic monitoring (i.e. invasive arterial blood pressure and central venous pressure), supplemented by transesophageal echocardiography. Pulmonary arterial catheter and calibrated trend monitoring devices were also routinely available. In contrast, non-calibrated trend monitoring and esophageal doppler ultrasound devices were not commonly in use. Cerebral oximetry is increasingly emerging, but lacks clear indications. The majority of patients undergoing cardiac surgery, especially in university hospitals, required catecholamines during perioperative care, In case of low cardiac output syndrome, dobutamine (32%), epinephrine (30%) or phosphodiesterase inhibitors (8%) were first choice. In case of hypotension following vasoplegia, norepinephrine (96%) represented the most common catecholamine. 88% of the participating centers reported regular use of colloid fluids, with hydroxyethyl starches (HES) being first choice (64%).

CONCLUSIONS

Choice of hemodynamic monitoring is homogenous throughout German centers treating cardiac surgery patients. Norepinephrine is the first line catecholamine in cases of decrease in peripheral vascular resistance. However, catecholamine choice for low cardiac output syndrome varies considerably. HES was the primary colloid used for fluid resuscitation. After conduct of this survey, HES use was restricted by European regulatory authorities in critically ill patients and should only be considered as second-line fluid in surgical patients without renal impairment or severe coagulopathy. Large clinical studies addressing catecholamine and fluid therapy in cardiac surgery patients are lacking.

Pharmacokinetics, hemodynamic and metabolic effects of epinephrine to prevent post-operative low cardiac output syndrome in children

Introduction

The response to exogenous epinephrine (Ep) is difficult to predict given the multitude of factors involved such as broad pharmacokinetic and pharmacodynamic between-subject variabilities, which may be more pronounced in children. We investigated the pharmacokinetics and pharmacodynamics of Ep, co-administered with milrinone, in children who underwent open heart surgical repair for congenital defects following cardiopulmonary bypass, including associated variability factors.

Methods

Thirty-nine children with a high risk of low cardiac output syndrome were prospectively enrolled. Ep pharmacokinetics, hemodynamic and metabolic effects were analyzed using the non-linear mixed effects modeling software MONOLIX. According to the final model, an Ep dosing simulation was suggested.

Results

Ep dosing infusions ranged from 0.01 to 0.23 μg.kg^-1.min^-1 in children whose weight ranged from 2.5 to 58 kg. A one-compartment open model with linear elimination adequately described the Ep concentration-time courses. Bodyweight (BW) was the main covariate influencing clearance (CL) and endogenous Ep production rate (q0) via an allometric relationship: CL(BWi) = θ_CL x (BWi)^3/4 and q0(BWi) = θ_q0 x (BWi )^3/4. The increase in heart rate (HR) and mean arterial pressure (MAP) as a function of Ep concentration were well described using an Emax model. The effect of age was significant on HR and MAP basal level parameters. Assuming that Ep stimulated the production rate of plasma glucose, the increases in plasma glucose and lactate levels were well described by turnover models without any significant effect of age, BW or exogenous glucose supply.

Conclusions

According to this population analysis, the developmental effects of BW and age explained a part of the pharmacokinetic and pharmacodynamics between-subject variabilities of Ep administration in critically ill children. This approach ultimately leads to a valuable Ep dosing simulation which should help clinicians to determine an appropriate a priori dosing regimen.

Hemodynamic variables and progression of acute kidney injury in critically ill patients with severe sepsis: data from the prospective observational FINNAKI study

Introduction

Knowledge of the association of hemodynamics with progression of septic acute kidney injury (AKI) is limited. However, some recent data suggest that mean arterial pressure (MAP) exceeding current guidelines (60–65 mmHg) may be needed to prevent AKI. We hypothesized that higher MAP during the first 24 hours in the intensive care unit (ICU), would be associated with a lower risk of progression of AKI in patients with severe sepsis.

Methods

We identified 423 patients with severe sepsis and electronically recorded continuous hemodynamic data in the prospective observational FINNAKI study. The primary endpoint was progression of AKI within the first 5 days of ICU admission defined as new onset or worsening of AKI by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. We evaluated the association of hemodynamic variables with this endpoint. We included 53724 10-minute medians of MAP in the analysis. We analysed the ability of time-adjusted MAP to predict progression of AKI by receiver operating characteristic (ROC) analysis.

Results

Of 423 patients, 153 (36.2%) had progression of AKI. Patients with progression of AKI had significantly lower time-adjusted MAP, 74.4 mmHg [68.3-80.8], than those without progression, 78.6 mmHg [72.9-85.4], P < 0.001. A cut-off value of 73 mmHg for time-adjusted MAP best predicted the progression of AKI. Chronic kidney disease, higher lactate, higher dose of furosemide, use of dobutamine and time-adjusted MAP below 73 mmHg were independent predictors of progression of AKI.

Conclusions

The findings of this large prospective multicenter observational study suggest that hypotensive episodes (MAP under 73 mmHg) are associated with progression of AKI in critically ill patients with severe sepsis.

Preoperative levosimendan in ischemic mitral valve repair

Background

Levosimendan is a new calcium sensitizing drug with vasodilatory and inotropic properties, which is used for the treatment of postoperative low cardiac output syndrome and difficult weaning from cardiopulmonary bypass.

Objective

To evaluate the hemodynamic effects of levosimendan during and after coronary artery bypass grafting on cardiopulmonary bypass and mitral valve repair in patients with low left ventricular ejection fractions (<30%).

Methods

40 patients were enrolled in this double-blind prospective randomized controlled trial. They received either levosimendan or a placebo preoperatively ( n = 20) for 24 h. Clinical parameters were measured before and after administration. Any adverse events during and after drug administration and postoperative complications were evaluated.

Results

Patients treated with levosimendan exhibited a higher cardiac index and mean arterial pressure intraoperative and in the early postoperative period, compared to the control group. Patients treated with levosimendan required less ventilatory support ( p < 0.0001) and had shorter intensive care unit ( p < 0.0001) and hospital stay ( p < 0.0001).

Conclusions

Preoperative treatment with levosimendan in patients undergoing coronary artery bypass grafting and mitral valve repair resulted in improved hemodynamics and a stable postoperative course.

Hyperkalemic cardioplegia for adult and pediatric surgery: end of an era?

Despite surgical proficiency and innovation driving low mortality rates in cardiac surgery, the disease severity, comorbidity rate, and operative procedural difficulty have increased. Today's cardiac surgery patient is older, has a "sicker" heart and often presents with multiple comorbidities; a scenario that was relatively rare 20 years ago. The global challenge has been to find new ways to make surgery safer for the patient and more predictable for the surgeon. A confounding factor that may influence clinical outcome is high K(+) cardioplegia. For over 40 years, potassium depolarization has been linked to transmembrane ionic imbalances, arrhythmias and conduction disturbances, vasoconstriction, coronary spasm, contractile stunning, and low output syndrome. Other than inducing rapid electrochemical arrest, high K(+) cardioplegia offers little or no inherent protection to adult or pediatric patients. This review provides a brief history of high K(+) cardioplegia, five areas of increasing concern with prolonged membrane K(+) depolarization, and the basic science and clinical data underpinning a new normokalemic, "polarizing" cardioplegia comprising adenosine and lidocaine (AL) with magnesium (Mg(2+)) (ALM™). We argue that improved cardioprotection, better outcomes, faster recoveries and lower healthcare costs are achievable and, despite the early predictions from the stent industry and cardiology, the "cath lab" may not be the place where the new wave of high-risk morbid patients are best served.

Dexmedetomidine overdosage: An unusual presentation

We present a case of dexmedetomidine toxicity in a 3-year-old child. The case report describes the features and outlines the treatment strategy adopted. The child presented with bradypnoea, bradycardia, hypotension, deep hypnosis and miosis. He was successfully managed with oxygen, saline boluses and adrenaline infusion. He became haemodynamically stable with adrenaline infusion. He started responding to painful stimuli in 3 h and became oriented in 7 h. Dexmedetomidine, a selective α₂ adrenoceptor agonist, is claimed to have a wide safety margin. This case report highlights the fact that dexmedetomidine administered in a toxic dose may be life-threatening may present with miosis and adrenaline infusion may be a useful supportive treatment.

Prolonged sevoflurane administration in the off-pump coronary artery bypass graft surgery: beneficial effects

PURPOSE

The benefits of intraoperative administration of halogenated agents in patients undergoing cardiac surgery have been shown by numerous studies. The mechanisms of preconditioning and postconditioning appear to be the cause of these benefits. The possibility of maintaining the early postoperative sedation with halogenated agents, after its intraoperative administration, can increase their benefits.

PATIENTS AND METHODS

This is a prospective trial with 60 patients undergoing coronary artery bypass graft surgery divided into 3 groups according to the administration of hypnotic drugs in the intraoperative and postoperative periods (sevoflurane, sevoflurane: SS, sevoflurane-propofol: SP, propofol-propofol: PP). For the first 48 hours, hemodynamic parameters, the need for inotropic drugs, N-terminal pro-brain natriuretic peptide, and troponin I plasmatic concentrations were obtained.

RESULTS

There were significant differences between group SS and the other 2 groups in the levels of N-terminal pro-brain natriuretic peptide (SS [501±280 pg/mL] compared with SP [1270±498 pg/mL] and PP [1775±527 pg/mL] [P<.05]) and troponin I (SS [0.5±0.4 ng/mL] compared with SP [1.61±1.30 ng/mL] and PP [2.27±1.5 ng/mL] [P<.05]) and a lower number of inotropic drugs.

CONCLUSION

Sevoflurane administration in patients undergoing off-pump coronary artery bypass graft, in the operating room and the intensive care unit, decreases myocardial injury markers compared with patients who only received sevoflurane in the intraoperative period, but both were a better option to decrease levels of myocardial markers when compared with the propofol group.

Mild metabolic acidosis impairs the β-adrenergic response in isolated human failing myocardium

INTRODUCTION

Pronounced extracellular acidosis reduces both cardiac contractility and the β-adrenergic response. In the past, this was shown in some studies using animal models. However, few data exist regarding how the human end-stage failing myocardium, in which compensatory mechanisms are exhausted, reacts to acute mild metabolic acidosis. The aim of this study was to investigate the effect of mild metabolic acidosis on contractility and the β-adrenergic response of isolated trabeculae from human end-stage failing hearts.

METHODS

Intact isometrically twitching trabeculae isolated from patients with end-stage heart failure were exposed to mild metabolic acidosis (pH 7.20). Trabeculae were stimulated at increasing frequencies and finally exposed to increasing concentrations of isoproterenol (0 to 1 × 10(-6) M).

RESULTS

A mild metabolic acidosis caused a depression in twitch-force amplitude of 26% (12.1 ± 1.9 to 9.0 ± 1.5 mN/mm(2); n = 12; P < 0.01) as compared with pH 7.40. Force-frequency relation measurements yielded no further significant differences of twitch force. At the maximal isoproterenol concentration, the force amplitude was comparable in each of the two groups (pH 7.40 versus pH 7.20). However, the half-maximal effective concentration (EC50) was significantly increased in the acidosis group, with an EC50 of 5.834 × 10(-8) M (confidence interval (CI), 3.48 × 10(-8) to 9.779 × 10(-8); n = 9), compared with the control group, which had an EC50 of 1.056 × 10(-8) M (CI, 2.626 × 10(-9) to 4.243 × 10(-8); n = 10; P < 0.05), indicating an impaired β-adrenergic force response.

CONCLUSIONS

Our data show that mild metabolic acidosis reduces cardiac contractility and significantly impairs the β-adrenergic force response in human failing myocardium. Thus, our results could contribute to the still-controversial discussion about the therapy regimen of acidosis in patients with critical heart failure.

Mapping genetic variants associated with beta-adrenergic responses in inbred mice

β-blockers and β-agonists are primarily used to treat cardiovascular diseases. Inter-individual variability in response to both drug classes is well recognized, yet the identity and relative contribution of the genetic players involved are poorly understood. This work is the first genome-wide association study (GWAS) addressing the values and susceptibility of cardiovascular-related traits to a selective β₁-blocker, Atenolol (ate), and a β-agonist, Isoproterenol (iso). The phenotypic dataset consisted of 27 highly heritable traits, each measured across 22 inbred mouse strains and four pharmacological conditions. The genotypic panel comprised 79922 informative SNPs of the mouse HapMap resource. Associations were mapped by Efficient Mixed Model Association (EMMA), a method that corrects for the population structure and genetic relatedness of the various strains. A total of 205 separate genome-wide scans were analyzed. The most significant hits include three candidate loci related to cardiac and body weight, three loci for electrocardiographic (ECG) values, two loci for the susceptibility of atrial weight index to iso, four loci for the susceptibility of systolic blood pressure (SBP) to perturbations of the β-adrenergic system, and one locus for the responsiveness of QTc (p<10⁻⁸). An additional 60 loci were suggestive for one or the other of the 27 traits, while 46 others were suggestive for one or the other drug effects (p<10⁻⁶). Most hits tagged unexpected regions, yet at least two loci for the susceptibility of SBP to β-adrenergic drugs pointed at members of the hypothalamic-pituitary-thyroid axis. Loci for cardiac-related traits were preferentially enriched in genes expressed in the heart, while 23% of the testable loci were replicated with datasets of the Mouse Phenome Database (MPD). Altogether these data and validation tests indicate that the mapped loci are relevant to the traits and responses studied.

Inotropic drugs and their uses in critical care

The aim of this article was to provide a resource for critical care nurses wishing to further their understanding of inotropic drugs used in critical care. The physiology of cardiac output and blood pressure is examined along with an explanation of adrenergic receptors acted on by inotropes. Some common indications for inotropic therapy are discussed, along with essential patient monitoring and dose calculations to ensure safe therapeutic ranges are observed. Some of the most commonly used positive inotropes used in critical care environments are individually explored, providing indications and some of the latest research relating to their uses. Frequently, observed side effects of individual inotropes are also offered, enabling the nurse to maintain patient safety when administering these potent drugs. Some major nursing and professional issues related to inotrope therapy and medicine administration are discussed, as well as some recommended practices in renewing infusions.

Postoperative inotrope and vasopressor use following CABG: outcome data from the CAPS-care study

BACKGROUND/AIM

Limited clinical data exist to guide practice patterns and evidence-based use of inotropes and vasopressors following coronary artery bypass grafting (CABG).

METHODS

Contemporary Analysis of Perioperative Cardiovascular Surgical Care (CAPS-Care) collected detailed perioperative data from 2390 CABG patients between 2004 and 2005 at 55 U.S. hospitals. High-risk elective or urgent CABG patients were eligible for inclusion. We stratified participating hospitals into high, medium, and low tertiles of inotrope use. Hospital-level outcomes were compared before and after risk adjustment for baseline characteristics.

RESULTS

Hospital-level risk-adjusted rates of any inotrope/vasopressor use varied from 100% to 35%. Hospitals in the highest tertile of use had more patients with mitral regurgitation compared to medium- or low-use hospitals (p < 0.001), more previous cardiovascular interventions (p = 0.002), longer cardiopulmonary bypass (p < 0.001), longer cross-clamp times (p < 0.001), and required more transfusions (p = 0.001). Despite these differences, unadjusted outcomes were similar between high-, medium-, and low-use hospitals for operative mortality (4.5% vs. 5.3% vs. 5.2%; p = 0.702), 30-day mortality (4.1% vs. 4.6% vs. 5.0%; p = 0.690), postoperative renal failure (7.2% vs. 9.2% vs. 6.6%; p = 0.142), atrial fibrillation (23.0% vs. 27.2% vs. 25.6%; p = 0.106), and acute limb ischemia (0.6% vs. 0.5% vs. 0.5%; p = 0.945). These similar outcomes persisted after risk adjustment: adjusted OR = 0.97 (95% CI [0.94, 1.00], p = 0.086) for operative mortality and adjusted OR = 1.00 (95% CI [0.96, 1.04], p = 0.974) for postoperative renal failure.

CONCLUSION

While considerable variability is present among hospitals in inotrope use following CABG, observational comparison of outcomes did not distinguish a superior pattern; thus, randomized prospective data are needed to better guide clinical practice.

The relationship between inotrope exposure, six-hour postoperative physiological variables, hospital mortality and renal dysfunction in patients undergoing cardiac surgery

Introduction

Acute haemodynamic complications are common after cardiac surgery and optimal perioperative use of inotropic agents, typically guided by haemodynamic variables, remains controversial. The aim of this study was to examine the relationship of inotrope use to hospital mortality and renal dysfunction.

Material and methods

A retrospective cohort study of 1,326 cardiac surgery patients was carried out at two university-affiliated ICUs. Multivariable logistic regression analysis and propensity matching were performed to evaluate whether inotrope exposure was independently associated with mortality and renal dysfunction.

Results

Patients exposed to inotropes had a higher mortality rate than those not exposed. After adjusting for differences in Parsonnet score, left ventricular ejection fraction, perioperative intraaortic balloon pump use, bypass time, reoperation and cardiac index, inotrope exposure appeared to be independently associated with increased hospital mortality (adjusted odds ratio (OR) 2.3, 95% confidence interval (95% CI) 1.2 to 4.5) and renal dysfunction (adjusted OR 2.7, 95% CI 1.5 to 4.6). A propensity score-matched analysis similarly demonstrated that death and renal dysfunction were significantly more likely to occur in patients exposed to inotropes (P = 0.01).

Conclusions

Postoperative inotrope exposure was independently associated with worse outcomes in this cohort study. Further research is needed to better elucidate the appropriate use of inotropes in cardiac surgery.

Inotropes in cardiac patients: update 2011

PURPOSE OF REVIEW

ICU patients frequently develop low output syndromes due to cardiac dysfunction, myocardial injury, and inflammatory activation. Conventional inotropic agents seem to be useful in restoring hemodynamic parameters and improving peripheral organ perfusion, but can increase short-term and long-term mortality in these patients. Novel inotropes may be promising in the management of ICU patients, having no serious adverse effects. This review summarizes all the current knowledge about the use of conventional and new inotropic agents in various clinical entities of critically ill patients.

RECENT FINDINGS

In recent European Society of Cardiology guidelines, inotropic agents are administered in patients with low output syndrome due to impaired cardiac contractility, and signs and symptoms of congestion. The most recommended inotropes in this condition are levosimendan and dobutamine (both class of recommendation: IIa, level of evidence: B). Recent data indicate that levosimendan may be useful in postmyocardial infarction cardiac dysfunction and septic shock through increasing coronary flow and attenuating inflammatory activation, respectively. Furthermore, calcium sensitizing by levosimendan can be effectively used for weaning of mechanical ventilation in postcardiac surgery patients and has also cardioprotective effect as expressed by the absence of troponin release in this patient population. Finally, new agents, such as istaroxime and cardiac myosin activators may be safe and improve central hemodynamics in experimental models of heart failure and heart failure patients in phase II clinical trials; however, large-scale randomized clinical trials are required.

SUMMARY

In an acute cardiac care setting, short-term use of inotropic agents is crucial for the restoration of arterial blood pressure and peripheral tissue perfusion, as well as weaning of cardiosurgery. New promising agents should be tested in randomized clinical trials.

Exploration of disease mechanism in acute kidney injury using a multiplex bead array assay: a nested case-control pilot study

BACKGROUND

Acute kidney injury (AKI) following cardiac surgery with cardiopulmonary bypass (CPB) causes increased morbidity and mortality.

OBJECTIVE

To evaluate the plasma profile of biomarkers potentially involved in AKI development following CPB.

METHODS

In a nested case-control study, plasma levels of 27 biomarkers in 11 AKI cases were compared with 25 controls.

RESULTS

Pre-CPB, plasma levels of epidermal growth factor and macrophage inflammatory protein-1beta, 2 h following CPB, soluble vascular cell adhesion molecule-1 (sVCAM-1), fractalkine and macrophage inflammatory protein-1alpha, and at later time points, sVCAM-1 and interleukin-6 were associated with AKI.

CONCLUSION

Biomarkers associated with AKI following CPB may merit further study.

Mixed venous oxygen saturation is a prognostic marker after surgery for aortic stenosis

BACKGROUND

Adequate monitoring of the hemodynamic state is essential after cardiac surgery and is vital for medical decision making, particularly concerning hemodynamic management. Unfortunately, commonly used methods to assess the hemodynamic state are not well documented with regard to outcome. Mixed venous oxygen saturation (SvO(2)) was therefore investigated after cardiac surgery.

METHODS

Detailed data regarding mortality were available on all patients undergoing aortic valve replacement for isolated aortic stenosis during a 5-year period in the southeast region of Sweden (n=396). SvO(2) was routinely measured on admission to the intensive care unit (ICU) and registered in a database. A receiver operating characteristics (ROC) analysis of SvO(2) in relation to post-operative mortality related to cardiac failure and all-cause mortality within 30 days was performed.

RESULTS

The area under the curve (AUC) was 0.97 (95% CI 0.96-1.00) for mortality related to cardiac failure (P=0.001) and 0.76 (95% CI 0.53-0.99) for all-cause mortality (P=0.011). The best cutoff for mortality related to cardiac failure was SvO(2) 53.7%, with a sensitivity of 1.00 and a specificity of 0.94. The negative predictive value was 100%. The best cutoff for all-cause mortality was SvO(2) 58.1%, with a sensitivity of 0.75 and a specificity of 0.84. The negative predictive value was 99.4%. Post-operative morbidity was also markedly increased in patients with a low SvO(2).

CONCLUSION

SvO(2), on admission to the ICU after surgery for aortic stenosis, demonstrated excellent sensitivity and specificity for post-operative mortality related to cardiac failure and a fairly good AUC for all-cause mortality, with an excellent negative predictive value.

Clinical review: practical recommendations on the management of perioperative heart failure in cardiac surgery

Acute cardiovascular dysfunction occurs perioperatively in more than 20% of cardiosurgical patients, yet current acute heart failure (HF) classification is not applicable to this period. Indicators of major perioperative risk include unstable coronary syndromes, decompensated HF, significant arrhythmias and valvular disease. Clinical risk factors include history of heart disease, compensated HF, cerebrovascular disease, presence of diabetes mellitus, renal insufficiency and high-risk surgery. EuroSCORE reliably predicts perioperative cardiovascular alteration in patients aged less than 80 years. Preoperative B-type natriuretic peptide level is an additional risk stratification factor. Aggressively preserving heart function during cardiosurgery is a major goal. Volatile anaesthetics and levosimendan seem to be promising cardioprotective agents, but large trials are still needed to assess the best cardioprotective agent(s) and optimal protocol(s). The aim of monitoring is early detection and assessment of mechanisms of perioperative cardiovascular dysfunction. Ideally, volume status should be assessed by 'dynamic' measurement of haemodynamic parameters. Assess heart function first by echocardiography, then using a pulmonary artery catheter (especially in right heart dysfunction). If volaemia and heart function are in the normal range, cardiovascular dysfunction is very likely related to vascular dysfunction. In treating myocardial dysfunction, consider the following options, either alone or in combination: low-to-moderate doses of dobutamine and epinephrine, milrinone or levosimendan. In vasoplegia-induced hypotension, use norepinephrine to maintain adequate perfusion pressure. Exclude hypovolaemia in patients under vasopressors, through repeated volume assessments. Optimal perioperative use of inotropes/vasopressors in cardiosurgery remains controversial, and further large multinational studies are needed. Cardiosurgical perioperative classification of cardiac impairment should be based on time of occurrence (precardiotomy, failure to wean, postcardiotomy) and haemodynamic severity of the patient's condition (crash and burn, deteriorating fast, stable but inotrope dependent). In heart dysfunction with suspected coronary hypoperfusion, an intra-aortic balloon pump is highly recommended. A ventricular assist device should be considered before end organ dysfunction becomes evident. Extra-corporeal membrane oxygenation is an elegant solution as a bridge to recovery and/or decision making. This paper offers practical recommendations for management of perioperative HF in cardiosurgery based on European experts' opinion. It also emphasizes the need for large surveys and studies to assess the optimal way to manage perioperative HF in cardiac surgery.

Cardiovascular response to beta-adrenergic blockade or activation in 23 inbred mouse strains

We report the characterisation of 27 cardiovascular-related traits in 23 inbred mouse strains. Mice were phenotyped either in response to chronic administration of a single dose of the β-adrenergic receptor blocker atenolol or under a low and a high dose of the β-agonist isoproterenol and compared to baseline condition. The robustness of our data is supported by high trait heritabilities (typically H²>0.7) and significant correlations of trait values measured in baseline condition with independent multistrain datasets of the Mouse Phenome Database. We then focused on the drug-, dose-, and strain-specific responses to β-stimulation and β-blockade of a selection of traits including heart rate, systolic blood pressure, cardiac weight indices, ECG parameters and body weight. Because of the wealth of data accumulated, we applied integrative analyses such as comprehensive bi-clustering to investigate the structure of the response across the different phenotypes, strains and experimental conditions. Information extracted from these analyses is discussed in terms of novelty and biological implications. For example, we observe that traits related to ventricular weight in most strains respond only to the high dose of isoproterenol, while heart rate and atrial weight are already affected by the low dose. Finally, we observe little concordance between strain similarity based on the phenotypes and genotypic relatedness computed from genomic SNP profiles. This indicates that cardiovascular phenotypes are unlikely to segregate according to global phylogeny, but rather be governed by smaller, local differences in the genetic architecture of the various strains.

Cyclohexanone contamination from extracorporeal circuits impairs cardiovascular function

Extracorporeal circulation provides critical life support in the face of cardiopulmonary or renal failure, but it also introduces a host of unique morbidities characterized by edema formation, cardiac insufficiency, autonomic dysfunction, and altered vasomotor function. We tested the hypothesis that cyclohexanone (CHX), a solvent used in production of extracorporeal circuits and intravenous (IV) bags, leaches into the contained fluids and can replicate these clinical morbidities. Crystalloid fluid samples from circuits and IV bags were analyzed by gas chromatography-mass spectrometry to provide a range of clinical CHX exposure levels, revealing CHX contamination of sampled fluids (9.63-3,694 microg/l). In vivo rat studies were conducted (n = 49) to investigate the effects of a bolus IV infusion of CHX vs. saline alone on cardiovascular function, baroreflex responsiveness, and edema formation. Cardiovascular function was evaluated by cardiac output, heart rate, stroke volume, vascular resistance, arterial pressure, and ventricular contractility. Baroreflex function was assessed by mean femoral arterial pressure responses to bilateral carotid occlusion. Edema formation was assessed by the ratio of wet to dry organ weights for lungs, liver, kidneys, and skin. CHX infusion led to systemic hypotension; pulmonary hypertension; depressed contractility, heart rate, stroke volume, and cardiac output; and elevated vascular resistance (P < 0.05). Mean arterial pressure responsiveness to carotid occlusion was dampened after CHX infusion (from +17.25 +/- 1.8 to +5.61 +/- 3.2 mmHg; P < 0.05). CHX infusion led to significantly higher wet-to-dry weight ratios vs. saline only (3.8 +/- 0.06 vs. 3.5 +/- 0.05; P < 0.05). CHX can reproduce clinical cardiovascular, neurological, and edema morbidities associated with extracorporeal circulatory treatment.

Assisting the failing heart

Anesthesiologists increasingly encounter patients who have a spectrum of heart failure ranging from stable chronic heart failure to acute heart failure to cardiogenic shock. Improved medical therapy has increased the survival of patients who have chronic heart failure but not of patients who have acute heart failure. New surgical techniques and mechanical devices may offer alternatives to certain patients who have refractory heart failure This article provides an overview of established and newer pharmacologic and nonpharmacologic therapies and surgical interventions to manage patients who have heart failure, including the perioperative management of heart transplantation and ventricular assist devices.

The metabolic and renal effects of adrenaline and milrinone in patients with myocardial dysfunction after coronary artery bypass grafting

INTRODUCTION

Myocardial dysfunction necessitating inotropic support is a typical complication after on-pump cardiac surgery. This prospective, randomized pilot study analyzes the metabolic and renal effects of the inotropes adrenaline and milrinone in patients needing inotropic support after coronary artery bypass grafting (CABG).

METHODS

During an 18-month period, 251 patients were screened for low cardiac output upon intensive care unit (ICU) admission after elective, isolated CABG surgery. Patients presenting with a cardiac index (CI) of less than 2.2 liters/minute per square meter upon ICU admission - despite adequate mean arterial (titrated with noradrenaline or sodium nitroprusside) and filling pressures - were randomly assigned to 14-hour treatment with adrenaline (n = 7) or milrinone (n = 11) to achieve a CI of greater than 3.0 liters/minute per square meter. Twenty patients not needing inotropes served as controls. Hemodynamics, plasma lactate, pyruvate, glucose, acid-base status, insulin requirements, the urinary excretion of alpha-1-microglobuline, and creatinine clearance were determined during the treatment period, and cystatin-C levels were determined up to 48 hours after surgery (follow-up period).

RESULTS

After two to four hours after ICU admission, the target CI was achieved in both intervention groups and maintained during the observation period. Plasma lactate, pyruvate, the lactate/pyruvate ratio, plasma glucose, and insulin doses were higher (p < 0.05) in the adrenaline-treated patients than during milrinone or control conditions. The urinary excretion of alpha-1-microglobuline was higher in the adrenaline than in the control group 6 to 14 hours after admission (p < 0.05). No between-group differences were observed in creatinine clearance, whereas plasma cystatin-C levels were significantly higher in the adrenaline than in the milrinone or the control group after 48 hours (p < 0.05).

CONCLUSION

This suggests that the use of adrenaline for the treatment of postoperative myocardial dysfunction - in contrast to treatment with the PDE-III inhibitor milrinone - is associated with unwarranted metabolic and renal effects.

Inoprotection: the perioperative role of levosimendan

Levosimendan is emerging as a novel cardioprotective inotrope. Levosimendan augments myocardial contractility by sensitising contractile myofilaments to calcium without increasing myosin adenosine triphosphatase activity or oxygen consumption. Levosimendan activates cellular adenosine triphosphate-dependent potassium channels, a mechanism which is postulated to protect cells from ischaemia in a manner similar to ischaemic preconditioning. Levosimendan may therefore protect the ischaemic myocardium during ischaemia-reperfusion as well as improve the contractile function of the heart. Adenosine triphosphate-dependent potassium channel activation by levosimendan may also be protective in other tissues, such as coronary vascular endothelium, kidney and brain. Clinical trials in patients with decompensated heart failure and myocardial ischaemia show levosimendan to improve haemodynamic performance and potentially improve survival. This paper reviews the known pharmacology of levosimendan, the clinical experience with the drug to date and the potential use of levosimendan as a cardioprotective agent during surgery.

Levosimendan: the inotrope of choice in cardiogenic shock secondary to takotsubo cardiomyopathy?

Takotsubo cardiomyopathy (TC) has become an increasingly recognised entity in Western literature since its initial reporting in Japan. The pathogenesis underlying the myocardial stunning and systolic dysfunction is thought to be induced by elevated systemic levels of catecholamines and neuropeptides. Whilst the majority of patients are haemodynamically stable, a small proportion can develop cardiogenic shock. This creates a therapeutic dilemma because inotropic support using exogenous catecholamines (adrenaline, dobutamine, dopamine) may be counter-productive. Two cases where the calcium sensitiser levosimendan (a non-catecholamine inotrope) was used successfully in TC-related cardiogenic shock are presented. The management of circulatory compromise in TC is then discussed.

Current practice of hemodynamic monitoring and vasopressor and inotropic therapy in post-operative cardiac surgery patients in Germany: results from a postal survey

BACKGROUND

In Germany, more than 100,000 patients are monitored and treated in 80 intensive care units (ICUs) following cardiac surgery each year. The controversies concerning the different methods of hemodynamic monitoring and the appropriate agents for volume therapy and inotropic support are well known. However, little is known about how monitoring and treatment are currently performed.

METHODS

A questionnaire with 39 questions was sent to the leading physicians of 80 ICUs in Germany, treating patients after cardiac surgery. The questions to be answered covered the current practice of hemodynamic monitoring, volume replacement, inotropic/vasopressor support and transfusions in patients after cardiac surgery.

RESULTS

Sixty-nine per cent of the questionnaires were completed and returned. All ICUs used basic monitoring as recommended by the societies. The use of advanced hemodynamic monitoring included the pulmonary artery catheter (58.2%), transesophageal echocardiography (38.1%) and transpulmonary dilution techniques (13%). Crystalloids (21.2%) and colloids (73%) were used for volume replacement. Epinephrine (41.8%) and dobutamine (30.9%) were the first-choice inotropic drugs for the treatment of low cardiac output syndrome, followed by phosphodiesterase inhibitors (14.5%). Second-choice drugs for the treatment of low cardiac output syndrome were enoximone (29%), milrinone (25%) and dobutamine (25%). A written transfusion protocol and a transfusion threshold for red blood cells existed in 59% and 79% of ICUs, respectively.

CONCLUSION

Hemodynamic monitoring and the variability in clinical practice with regard to volume replacement, transfusion triggers and the use of vasopressors/inotropes in cardiac surgery patients tend to follow the results of traditional experience rather than current scientific knowledge. Guidelines are therefore necessary to help to improve the standards of intensive care after cardiac surgery and thus the outcome of patients.

Properties of the Human Umbilical Vein as a Living Scaffold for a Tissue-Engineered Vessel Graft

Umbilical cords are usually discarded after delivery, even though they contain a set of functional vessels. We investigated whether the human umbilical vein (HUV) is suitable as a storable scaffold for the tissue engineering of small-caliber vessel grafts. Isolated HUVs were cryopreserved by freezing or vitrification. The reaction of the vessels to vasoactive compounds and the mechanical properties were determined in an organ bath. Mitochondrial metabolism, release of antithrombotic compounds, and platelet adhesion were measured on the luminal vessel surface. Seeding with endothelial cells was tested on denuded HUVs. The vessels showed a weak response to norepinephrine but were readily contracted by serotonin and by the thromboxane A2 mimetic U46619. Endothelium-dependent vasorelaxation was weak, reaching significance only for histamine. However, the vessels relaxed to sodium nitroprusside, and to acetylcholine if sandwiched with human saphenous vein. Cryopreservation did not change the mechanical properties in the relevant tension range. Vasoconstriction to potassium chloride and serotonin were reduced after freezing (22.9+/-7.6%, 27.7+/-10.2%) and after vitrification (2.6+/-5.8%, 4.3+/-7.1%). The mitochondrial metabolism was also attenuated after freezing (57.9+/-25.9%) and after vitrification (21.7+/-6.7%). Prostacyclin release was elevated after both cryopreservation procedures (4.0-fold, 3.9-fold), whereas there was no significant change in the adhesion of platelets. Denuded HUVs could readily be seeded with isolated endothelial cells before and after freezing. We conclude that HUV is suitable as a storable living scaffold with antithrombogenic properties.

French multicentre survey on the use of inotropes after cardiac surgery

Results from a French multicentre survey on the use of inotropes after cardiac surgery are presented. Consideration of these findings, which strictly apply only to France, highlights the importance of developing monitoring strategies to help in decision making regarding therapy with inotropes in this context.