Prediction of survival in out-of-hospital cardiac arrest: the updated Swedish cardiac arrest risk score (SCARS) model.

Aims: Out-of-hospital cardiac arrest (OHCA) is a major health concern worldwide. Although one-third of all patients achieve a return of spontaneous circulation and may undergo a difficult period in the intensive care unit, only 1 in 10 survive. This study aims to improve our previously developed machine learning model for early prognostication of survival in OHCA. Methods and results: We studied all cases registered in the Swedish Cardiopulmonary Resuscitation Registry during 2010 and 2020 (n = 55 615). We compared the predictive performance of extreme gradient boosting (XGB), light gradient boosting machine (LightGBM), logistic regression, CatBoost, random forest, and TabNet. For each framework, we developed models that optimized (i) a weighted F1 score to penalize models that yielded more false negatives and (ii) a precision-recall area under the curve (PR AUC). LightGBM assigned higher importance values to a larger set of variables, while XGB made predictions using fewer predictors. The area under the curve receiver operating characteristic (AUC ROC) scores for LightGBM were 0.958 (optimized for weighted F1) and 0.961 (optimized for a PR AUC), while for XGB, the scores were 0.958 and 0.960, respectively. The calibration plots showed a subtle underestimation of survival for LightGBM, contrasting with a mild overestimation for XGB models. In the crucial range of 0-10% likelihood of survival, the XGB model, optimized with the PR AUC, emerged as a clinically safe model. Conclusion: We improved our previous prediction model by creating a parsimonious model with an AUC ROC at 0.96, with excellent calibration and no apparent risk of underestimating survival in the critical probability range (0-10%). The model is available at www.gocares.se.

Prehospital monitoring of cerebral circulation during out of hospital cardiac arrest ? A feasibility study.

BACKGROUND: About two-thirds of the in-hospital deaths after out-of-hospital cardiac arrests (OHCA) are a consequence of anoxic brain injuries, which are due to hypoperfusion of the brain during the cardiac arrests. Being able to monitor cerebral perfusion during cardiopulmonary resuscitation (CPR) is desirable to evaluate the effectiveness of the CPR and to guide further decision making and prognostication. METHODS: Two different devices were used to measure regional cerebral oxygen saturation (rSO2): INVOS™ 5100 (Medtronic, Minneapolis, MN, USA) and Root® O3 (Masimo Corporation, Irvine, CA, USA). At the scene of the OHCA, advanced life support (ALS) was immediately initiated by the Emergency Medical Services (EMS) personnel. Sensors for measuring rSO2 were applied at the scene or during transportation to the hospital. rSO2 values were documented manually together with ETCO2 (end tidal carbon dioxide) on a worksheet specially designed for this study. The study worksheet also included a questionnaire for the EMS personnel with one statement on usability regarding potential interference with ALS. RESULTS: Twenty-seven patients were included in the statistical analyses. In the INVOS™5100 group (n = 13), the mean rSO2 was 54% (95% CI 40.3-67.7) for patients achieving a return of spontaneous circulation (ROSC) and 28% (95% CI 12.3-43.7) for patients not achieving ROSC (p = 0.04). In the Root® O3 group (n = 14), the mean rSO2 was 50% (95% CI 46.5-53.5) and 41% (95% CI 36.3-45.7) (p = 0.02) for ROSC and no ROSC, respectively. ETCO2 values were not statistically different between the groups. The EMS personnel graded the statement of interference with ALS to a median of 2 (IQR 1-6) on a 10-point Numerical Rating Scale. CONCLUSION: Our results suggest that both INVOS™5100 and ROOT® O3 can distinguish between ROSC and no ROSC in OHCA, and both could be used in the pre-hospital setting and during transport with minimal interference with ALS.

Renal Hemodynamics, Function, and Oxygenation in Critically Ill Patients and after Major Surgery.

This review outlines the available data from the work of our group on renal hemodynamics, function, and oxygenation in patients who are critically ill with acute renal dysfunction, such as those with postoperative AKI, those in early clinical septic shock, in patients undergoing cardiac surgery with cardiopulmonary bypass, or in patients undergoing liver transplantation. We also provide information on renal hemodynamics, function, and oxygenation in patients with chronic renal impairment due to congestive heart failure. This review will argue that, for all of these groups of patients, the common denominator is that renal oxygenation is impaired due to a lower renal oxygen delivery or a pronounced increase in renal oxygen consumption.

Durable circulatory support with a paracorporeal device as an option for pediatric and adult heart failure patients.

OBJECTIVES: Not all patients in need of durable mechanical circulatory support are suitable for a continuous-flow left ventricular assist device. We describe patient populations who were treated with the paracorporeal EXCOR, including children with small body sizes, adolescents with complex congenital heart diseases, and adults with biventricular failure. METHODS: Information on clinical data, echocardiography, invasive hemodynamic measurements, and surgical procedures were collected retrospectively. Differences between various groups were compared. RESULTS: Between 2008 and 2018, a total of 50 patients (21 children and 29 adults) received an EXCOR as bridge to heart transplantation or myocardial recovery. The majority of patients had heart failure compatible with Interagency Registry for Mechanically Assisted Circulatory Support profile 1. At year 5, the overall survival probability for children was 90%, and for adults 75% (P = .3). After we pooled data from children and adults, the survival probability between patients supported by a biventricular assist device was similar to those treated with a left ventricular assist device/ right ventricular assist device (94% vs 75%, respectively, P = .2). Patients with dilated cardiomyopathy had a trend toward better survival than those with other heart failure etiologies (92% vs 70%, P = .05) and a greater survival free from stroke (92% vs 64%, P = .01). Pump house exchange was performed in nine patients due to chamber thrombosis (n = 7) and partial membrane rupture (n = 2). There were 14 cases of stroke in eleven patients. CONCLUSIONS: Despite severe illness, patient survival on EXCOR was high, and the long-term overall survival probability following heart transplantation and recovery was advantageous. Treatment safety was satisfactory, although still hampered by thromboembolism, mechanical problems, and infections.

Effects of milrinone on renal perfusion, filtration and oxygenation in patients with acute heart failure and low cardiac output early after cardiac surgery.

PURPOSE: Early postoperative heart failure is common after cardiac surgery, and inotrope treatment may impact renal perfusion and oxygenation. We aimed to study the renal effects of the inodilator milrinone when used for the treatment of heart failure after weaning from cardiopulmonary bypass (CPB). MATERIAL AND METHODS: In 26 patients undergoing cardiac surgery with CPB, we used renal vein catheterization to prospectively measure renal blood flow (RBF), glomerular filtration rate (GFR), and renal oxygenation. Patients who developed acute heart failure and low cardiac output (cardiac index <2.1 L/min/m2) at 30 min after weaning from CPB (n = 7) were given milrinone, and the remaining patients (n = 19) served as controls. Additional measurements were made at 60 min after CPB. RESULTS: In patients with acute postoperative heart failure, before receiving milrinone, renal blood flow was lower (-33%, p < .05) while renal oxygen extraction was higher (41%, p < .05) compared to the control group. Milrinone increased cardiac index (21%, p < .001), RBF (36%, p < .01) and renal oxygen delivery (35%, p < .01), with no significant change in GFR and oxygen consumption compared to the control group. CONCLUSIONS: In patients with acute heart failure after weaning from CPB, the milrinone-induced increase in cardiac output was accompanied by improved renal oxygenation. TRIAL REGISTRATION: ClinicalTrials.gov; identifier NCT02405195, date of registration; March 27, 2015, and NCT02549066, date of registration; 9 September 2015.

Impact of Cardiopulmonary Bypass Flow on Renal Oxygenation in Patients Undergoing Cardiac Operations.

BACKGROUND: Cardiac surgery with cardiopulmonary bypass (CPB) is associated with acute kidney injury, and the risk increases with low oxygen delivery during CPB. We hypothesized that renal oxygenation could be improved at higher than normal CPB flow rates. METHODS: After ethical approval and informed consent, 17 patients with normal serum creatinine undergoing normothermic CPB were included and received pulmonary artery and renal vein catheters after anesthesia induction for measurements of systemic and renal variables. Renal oxygen extraction, a direct measure of the renal oxygen delivery/renal oxygen consumption ratio, and renal filtration fraction were measured, the latter by renal extraction of 51chromium-ethylenediaminetetraacetic acid. After start of CPB and aortic cross-clamp, the pump flow rate was randomly varied between 2.4, 2.7, and 3.0 L · min-1 · m-2, and measurements were made after 10 minutes at each flow rate. RESULTS: Renal oxygen extraction increased by 30% at a flow rate of 2.4 L · min-1 · m-2 versus pre-CPB (p < 0.05). At a flow rate of 2.7 and 3.0 L · min-1 · m-2, Renal oxygen extraction was 12% (p < 0.05) and 23% (p < 0.01) lower, respectively, compared with 2.4 L · min-1 · m-2. This corresponds to a 14% and 30% improvement, respectively, of the renal oxygen supply/demand relationship. Filtration fraction was not affected by changes in flow rate, indicating that the glomerular filtration rate increased in proportion to the increase in renal perfusion. CONCLUSIONS: The impaired renal oxygenation seen during CPB is ameliorated by an increase in CPB flow rate. Thus, one way to protect the kidneys during CPB could be to use a higher flow rate than the one traditionally used.

Renal Blood Flow, Glomerular Filtration Rate, and Renal Oxygenation in Early Clinical Septic Shock.

OBJECTIVE: Data on renal hemodynamics, function, and oxygenation in early clinical septic shock are lacking. We therefore measured renal blood flow, glomerular filtration rate, renal oxygen consumption, and oxygenation in patients with early septic shock. DESIGN: Prospective comparative study. SETTING: General and cardiothoracic ICUs. PATIENTS: Patients with norepinephrine-dependent early septic shock (n = 8) were studied within 24 hours after arrival in the ICU and compared with postcardiac surgery patients without acute kidney injury (comparator group, n = 58). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data on systemic hemodynamics and renal variables were obtained during two 30-minute periods. Renal blood flow was measured by the infusion clearance of para-aminohippuric acid, corrected for renal extraction of para-aminohippuric acid. Renal filtration fraction was measured by renal extraction of chromium-51 labeled EDTA. Renal oxygenation was estimated from renal oxygen extraction. Renal oxygen delivery (-24%; p = 0.037) and the renal blood flow-to-cardiac index ratio (-21%; p = 0.018) were lower, renal vascular resistance was higher (26%; p = 0.027), whereas renal blood flow tended to be lower (-19%; p = 0.068) in the septic group. Glomerular filtration rate (-32%; p = 0.006) and renal sodium reabsorption (-29%; p = 0.014) were both lower in the septic group. Neither renal filtration fraction nor renal oxygen consumption differed significantly between groups. Renal oxygen extraction was significantly higher in the septic group (28%; p = 0.022). In the septic group, markers of tubular injury were elevated. CONCLUSIONS: In early clinical septic shock, renal function was lower, which was accompanied by renal vasoconstriction, a lower renal oxygen delivery, impaired renal oxygenation, and tubular sodium reabsorption at a high oxygen cost compared with controls.

Renal function and oxygenation are impaired early after liver transplantation despite hyperdynamic systemic circulation.

BACKGROUND: Acute kidney injury (AKI) occurs frequently after liver transplantation and is associated with the development of chronic kidney disease and increased mortality. There is a lack of data on renal blood flow (RBF), oxygen consumption, glomerular filtration rate (GFR) and renal oxygenation, i.e. the renal oxygen supply/demand relationship, early after liver transplantation. Increased insight into the renal pathophysiology after liver transplantation is needed to improve the prevention and treatment of postoperative AKI. We have therefore studied renal hemodynamics, function and oxygenation early after liver transplantation in humans. METHODS: Systemic hemodynamic and renal variables were measured during two 30-min periods in liver transplant recipients (n = 12) and post-cardiac surgery patients (controls, n = 73). RBF and GFR were measured by the renal vein retrograde thermodilution technique and by renal extraction of Cr-EDTA (= filtration fraction), respectively. Renal oxygenation was estimated from the renal oxygen extraction. RESULTS: In the liver transplant group, GFR decreased by 40% (p < 0.05), compared to the preoperative value. Cardiac index and systemic vascular resistance index were 65% higher (p < 0.001) and 36% lower (p < 0.001), respectively, in the liver transplant recipients compared to the control group. GFR was 27% (p < 0.05) and filtration fraction 40% (p < 0.01) lower in the liver transplant group. Renal vascular resistance was 15% lower (p < 0.05) and RBF was 18% higher (p < 0.05) in liver transplant recipients, but the ratio between RBF and cardiac index was 27% lower (p < 0.001) among the liver-transplanted patients compared to the control group. Renal oxygen consumption and extraction were both higher in the liver transplants, 44% (p < 0.01) and 24% (p < 0.05) respectively. CONCLUSIONS: Despite the hyperdynamic systemic circulation and renal vasodilation, there is a severe decline in renal function directly after liver transplantation. This decline is accompanied by an impaired renal oxygenation, as the pronounced elevation of renal oxygen consumption is not met by a proportional increase in renal oxygen delivery. This information may provide new insights into renal pathophysiology as a basis for future strategies to prevent/treat AKI after liver transplantation. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02455115 . Registered on 23 April 2015.

Are biventricular assist devices underused as a bridge to heart transplantation in patients with a high risk of postimplant right ventricular failure?

OBJECTIVE: Right ventricular failure in patients treated using left ventricular assist devices is associated with poor outcomes. We assessed the strategy of preplanned biventricular assist device implantation in patients with a high risk for right ventricular failure. METHODS: Between 2010 and 2014, we assigned 20 patients to preplanned biventricular assist device and 21 patients to left ventricular assist device as a bridge to heart transplantation on the basis of the estimated risk of postimplant right ventricular failure. Preimplant characteristics and postimplant outcomes were compared between the 2 groups. RESULTS: Patients with a biventricular assist device were younger, more often female, and more frequently had nonischemic heart disease than left ventricular assist device recipients. At preoperative assessment, biventricular assist device recipients had poorer Interagency Registry for Mechanically Assisted Circulatory Support profiles, a lower cardiac index, and more compromised right ventricular function. Survival on device to heart transplantation/weaning/destination for biventricular assist device and left ventricular assist device recipients was 90% versus 86% (not significant), with shorter heart transplantation waiting times for biventricular assist device recipients (median days, 154 vs 302, P < .001). Overall survival at 1 year was 85% (95% confidence interval, 62-95) versus 86% (95% confidence interval, 64-95) (not significant). The majority of both biventricular assist device and left ventricular assist device recipients could be discharged to home during the heart transplantation waiting time (55% vs 71%, not significant), and complication rates on device were comparable between groups (major stroke 10% vs 10%, not significant). CONCLUSIONS: Planned in advance, the biventricular assist device seems to be a feasible option as bridge to heart transplantation for patients with a high risk of postimplant right ventricular failure. The outcomes for these patients were similar to those observed for contemporary left ventricular assist device recipients, despite those receiving biventricular assist devices being more severely ill.

Effects of Cardiopulmonary Bypass on Renal Perfusion, Filtration, and Oxygenation in Patients Undergoing Cardiac Surgery.

BACKGROUND: Acute kidney injury is a common complication after cardiac surgery with cardiopulmonary bypass. The authors evaluated the effects of normothermic cardiopulmonary bypass on renal blood flow, glomerular filtration rate, renal oxygen consumption, and renal oxygen supply/demand relationship, i.e., renal oxygenation (primary outcome) in patients undergoing cardiac surgery. METHODS: Eighteen patients with a normal preoperative serum creatinine undergoing cardiac surgery procedures with normothermic cardiopulmonary bypass (2.5 l · min · m) were included after informed consent. Systemic and renal hemodynamic variables were measured by pulmonary artery and renal vein catheters before, during, and after cardiopulmonary bypass. Arterial and renal vein blood samples were taken for measurements of renal oxygen delivery and consumption. Renal oxygenation was estimated from the renal oxygen extraction. Urinary N-acetyl-ß-D-glucosaminidase was measured before, during, and after cardiopulmonary bypass. RESULTS: Cardiopulmonary bypass induced a renal vasoconstriction and redistribution of blood flow away from the kidneys, which in combination with hemodilution decreased renal oxygen delivery by 20%, while glomerular filtration rate and renal oxygen consumption were unchanged. Thus, renal oxygen extraction increased by 39 to 45%, indicating a renal oxygen supply/demand mismatch during cardiopulmonary bypass. After weaning from cardiopulmonary bypass, renal oxygenation was further impaired due to hemodilution and an increase in renal oxygen consumption, accompanied by a seven-fold increase in the urinary N-acetyl-ß-D-glucosaminidase/creatinine ratio. CONCLUSIONS: Cardiopulmonary bypass impairs renal oxygenation due to renal vasoconstriction and hemodilution during and after cardiopulmonary bypass, accompanied by increased release of a tubular injury marker.

Acute tamponade of the left paracorporeal pump house due to membrane defect in a patient with a Berlin Heart EXCOR biventricular assist device.

We report a case of acute tamponade of the left paracorporeal pump house in a patient supported by a Berlin Heart EXCOR biventricular assist device (BiVAD) caused by mechanical defect in the membrane of the arterial chamber. A 36-year old male was admitted for composite graft surgery due to a large aortic regurgitation and consecutive heart failure, decompensated postoperatively and was rescued by with an extracorporeal membrane oxygenation (ECMO) device. He was accepted for heart transplantation, and a BiVAD (Berlin Heart EXCOR) was implanted as bridge-to-transplantation. Two months after discharge, he experienced dyspnoea and received error signals from his BiVAD. Relatives released him from his BiVAD companion driver, connected him to the hand pump and transported him to our institution. On arrival, he was in cardiogenic shock and was stabilized by ECMO. Inspection of the arterial chamber revealed a wear hole and delamination of the diaphragm, which had led to a tamponade by air insufflation into the three-layer membrane. New BiVAD paracorporeal pumps were connected, and the patient was subsequently successfully transplanted. The case depicts the difficulty of diagnosis in this specific patient setting. Despite transparent design of the BiVAD chambers, the development of a chamber tamponade remained undetected until explantation of the system.

Effects of levosimendan on glomerular filtration rate, renal blood flow, and renal oxygenation after cardiac surgery with cardiopulmonary bypass: a randomized placebo-controlled study.

OBJECTIVES: Acute kidney injury develops in a large proportion of patients after cardiac surgery because of the low cardiac output syndrome. The inodilator levosimendan increases cardiac output after cardiac surgery with cardiopulmonary bypass, but a detailed analysis of its effects on renal perfusion, glomerular filtration, and renal oxygenation in this group of patients is lacking. We therefore evaluated the effects of levosimendan on renal blood flow, glomerular filtration rate, renal oxygen consumption, and renal oxygen demand/supply relationship, i.e., renal oxygen extraction, early after cardiac surgery with cardiopulmonary bypass. DESIGN: Prospective, placebo-controlled, and randomized trial. SETTING: Cardiothoracic ICU of a tertiary center. PATIENTS: Postcardiac surgery patients (n=30). INTERVENTIONS: The patients were randomized to receive levosimendan, 0.1 µg/kg/min after a loading dose of 12 µg/kg (n=15), or placebo (n=15). MEASUREMENTS AND MAIN RESULTS: The experimental procedure started 4-6 hours after surgery in the ICU during propofol sedation and mechanical ventilation. Systemic hemodynamic were evaluated by a pulmonary artery thermodilution catheter. Renal blood flow and glomerular filtration rate were measured by the renal vein retrograde thermodilution technique and by renal extraction of Cr-EDTA, respectively. Central venous pressure was kept constant by colloid/crystalloid infusion. Compared to placebo, levosimendan increased cardiac index (22%), stroke volume index (15%), and heart rate (7%) and decreased systemic vascular resistance index (21%), whereas mean arterial pressure was not affected. Levosimendan induced significant increases in renal blood flow (12%, p<0.05) and glomerular filtration rate (21%, p<0.05), decreased renal vascular resistance (18%, p<0.05) but caused no significant changes in filtration fraction, renal oxygen consumption, or renal oxygen extraction, compared to placebo. CONCLUSIONS: After cardiac surgery with cardiopulmonary bypass, levosimendan induces a vasodilation, preferentially of preglomerular resistance vessels, increasing both renal blood flow and glomerular filtration rate without jeopardizing renal oxygenation. Due to its pharmacodynamic profile, levosimendan might be an interesting alternative for treatment of postoperative heart failure complicated by acute kidney injury in postcardiac surgery patients.

Assessing glomerular filtration rate (GFR) in critically ill patients with acute kidney injury--true GFR versus urinary creatinine clearance and estimating equations.

INTRODUCTION: Estimation of kidney function in critically ill patients with acute kidney injury (AKI), is important for appropriate dosing of drugs and adjustment of therapeutic strategies, but challenging due to fluctuations in kidney function, creatinine metabolism and fluid balance. Data on the agreement between estimating and gold standard methods to assess glomerular filtration rate (GFR) in early AKI are lacking. We evaluated the agreement of urinary creatinine clearance (CrCl) and three commonly used estimating equations, the Cockcroft Gault (CG), the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, in comparison to GFR measured by the infusion clearance of chromium-ethylenediaminetetraacetic acid (51Cr-EDTA), in critically ill patients with early AKI after complicated cardiac surgery. METHODS: Thirty patients with early AKI were studied in the intensive care unit, 2 to 12 days after complicated cardiac surgery. The infusion clearance for 51Cr-EDTA obtained as a measure of GFR (GFR51Cr-EDTA) was calculated from the formula: GFR (mL/min/1.73m2)=(51Cr-EDTA infusion rate×1.73)/(arterial 51Cr-EDTA×body surface area) and compared with the urinary CrCl and the estimated GFR (eGFR) from the three estimating equations. Urine was collected in two 30-minute periods to measure urine flow and urine creatinine. Urinary CrCl was calculated from the formula: CrCl (mL/min/1.73m2)=(urine volume×urine creatinine×1.73)/(serum creatinine×30 min×body surface area). RESULTS: The within-group error was lower for GFR51Cr-EDTA than the urinary CrCl method, 7.2% versus 55.0%. The between-method bias was 2.6, 11.6, 11.1 and 7.39 ml/min for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA. The error was 103%, 68.7%, 67.7% and 68.0% for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA. CONCLUSIONS: The study demonstrated poor precision of the commonly utilized urinary CrCl method for assessment of GFR in critically ill patients with early AKI, suggesting that this should not be used as a reference method when validating new methods for assessing kidney function in this patient population. The commonly used estimating equations perform poorly when estimating GFR, with high biases and unacceptably high errors.

Renal oxygenation and haemodynamics in acute kidney injury and chronic kidney disease.

Acute kidney injury (AKI) is a major burden on health systems and may arise from multiple initiating insults, including ischaemia-reperfusion injury, cardiovascular surgery, radiocontrast administration and sepsis. Similarly, the incidence and prevalence of chronic kidney disease (CKD) continues to increase, with significant morbidity and mortality. Moreover, an increasing number of AKI patients survive to develop CKD and end-stage renal disease. Although the mechanisms for the development of AKI and progression to CKD remain poorly understood, initial impairment of oxygen balance likely constitutes a common pathway, causing renal tissue hypoxia and ATP starvation that, in turn, induce extracellular matrix production, collagen deposition and fibrosis. Thus, possible future strategies for one or both conditions may involve dopamine, loop diuretics, atrial natriuretic peptide and inhibitors of inducible nitric oxide synthase, substances that target kidney oxygen consumption and regulators of renal oxygenation, such as nitric oxide and heme oxygenase-1.

Mannitol increases renal blood flow and maintains filtration fraction and oxygenation in postoperative acute kidney injury: a prospective interventional study.

INTRODUCTION: Acute kidney injury (AKI), which is a major complication after cardiovascular surgery, is associated with significant morbidity and mortality. Diuretic agents are frequently used to improve urine output and to facilitate fluid management in these patients. Mannitol, an osmotic diuretic, is used in the perioperative setting in the belief that it exerts reno-protective properties. In a recent study on uncomplicated postcardiac-surgery patients with normal renal function, mannitol increased glomerular filtration rate (GFR), possibly by a deswelling effect on tubular cells. Furthermore, experimental studies have previously shown that renal ischemia causes an endothelial cell injury and dysfunction followed by endothelial cell edema. We studied the effects of mannitol on renal blood flow (RBF), glomerular filtration rate (GFR), renal oxygen consumption (RVO2), and extraction (RO2Ex) in early, ischemic AKI after cardiac surgery. METHODS: Eleven patients with AKI were studied during propofol sedation and mechanical ventilation 2 to 6 days after complicated cardiac surgery. All patients had severe heart failure treated with one (100%) or two (73%) inotropic agents and intraaortic balloon pump (36%). Systemic hemodynamics were measured with a pulmonary artery catheter. RBF and renal filtration fraction (FF) were measured by the renal vein thermo-dilution technique and by renal extraction of chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), respectively. GFR was calculated as the product of FF and renal plasma flow RBF × (1-hematocrit). RVO2 and RO2Ex were calculated from arterial and renal vein blood samples according to standard formulae. After control measurements, a bolus dose of mannitol, 225 mg/kg, was given, followed by an infusion at a rate of 75 mg/kg/h for two 30-minute periods. RESULTS: Mannitol did not affect cardiac index or cardiac filling pressures. Mannitol increased urine flow by 61% (P < 0.001). This was accompanied by a 12% increase in RBF (P < 0.05) and a 13% decrease in renal vascular resistance (P < 0.05). Mannitol increased the RBF/cardiac output (CO) relation (P = 0.040). Mannitol caused no significant changes in RO2Ext or renal FF. CONCLUSIONS: Mannitol treatment of postoperative AKI induces a renal vasodilation and redistributes systemic blood flow to the kidneys. Mannitol does not affect filtration fraction or renal oxygenation, suggestive of balanced increases in perfusion/filtration and oxygen demand/supply.

Effects of norepinephrine on renal perfusion, filtration and oxygenation in vasodilatory shock and acute kidney injury.

PURPOSE: The use of norepinephrine (NE) in patients with volume-resuscitated vasodilatory shock and acute kidney injury (AKI) remains the subject of much debate and controversy. The effects of NE-induced variations in mean arterial blood pressure (MAP) on renal blood flow (RBF), oxygen delivery (RDO(2)), glomerular filtration rate (GFR) and the renal oxygen supply/demand relationship (renal oxygenation) in vasodilatory shock with AKI have not been previously studied. METHODS: Twelve post-cardiac surgery patients with NE-dependent vasodilatory shock and AKI were studied 2-6 days after surgery. NE infusion rate was randomly and sequentially titrated to target MAPs of 60, 75 and 90 mmHg. At each target MAP, data on systemic haemodynamics, RBF, GFR and renal oxygen extraction were obtained by pulmonary artery catheter, by the renal vein thermodilution technique and by renal extraction of (51)Cr-ethylenediamine tetraacetic acid ((51)Cr-EDTA), respectively. RESULTS: At target MAP of 75 mmHg, RDO(2) (13%), GFR (27%) and urine flow were higher and renal oxygen extraction was lower (-7.4%) compared with at target MAP of 60 mmHg. However, the renal variables did not differ when compared at target MAPs of 75 and 90 mmHg. Cardiac index increased dose-dependently with NE. CONCLUSIONS: Restoration of MAP from 60 to 75 mmHg improves renal oxygen delivery, GFR and the renal oxygen supply/demand relationship in post-cardiac surgery patients with vasodilatory shock and AKI. This pressure-dependent renal perfusion, filtration and oxygenation at levels of MAP below 75 mmHg reflect a more or less exhausted renal autoregulatory reserve.

Acute renal failure is NOT an "acute renal success"--a clinical study on the renal oxygen supply/demand relationship in acute kidney injury.

OBJECTIVES: Acute kidney injury occurs frequently after cardiac or major vascular surgery and is believed to be predominantly a consequence of impaired renal oxygenation. However, in patients with acute kidney injury, data on renal oxygen consumption (RVO2), renal blood flow, glomerular filtration, and renal oxygenation, i.e., the renal oxygen supply/demand relationship, are lacking and current views on renal oxygenation in the clinical situation of acute kidney injury are presumptive and largely based on experimental studies. DESIGN: Prospective, two-group comparative study. SETTING: Cardiothoracic intensive care unit of a tertiary center. PATIENTS: Postcardiac surgery patients with (n = 12) and without (n = 37) acute kidney injury were compared with respect to renal blood flow, glomerular filtration, RVO2, and renal oxygenation. INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: Data on systemic hemodynamics (pulmonary artery catheter) and renal variables were obtained during two 30-min periods. Renal blood flow was measured using two independent techniques: the renal vein thermodilution technique and the infusion clearance of paraaminohippuric acid, corrected for renal extraction of paraaminohippuric acid. The filtration fraction was measured by the renal extraction of Cr-EDTA and the renal sodium resorption was measured as the difference between filtered and excreted sodium. Renal oxygenation was estimated from the renal oxygen extraction. Cardiac index and mean arterial pressure did not differ between the two groups. In the acute kidney injury group, glomerular filtration (-57%), renal blood flow (-40%), filtration fraction (-26%), and sodium resorption (-59%) were lower, renal vascular resistance (52%) and renal oxygen extraction (68%) were higher, whereas there was no difference in renal oxygen consumption between groups. Renal oxygen consumption for one unit of reabsorbed sodium was 2.4 times higher in acute kidney injury. CONCLUSIONS: Renal oxygenation is severely impaired in acute kidney injury after cardiac surgery, despite the decrease in glomerular filtration and tubular workload. This was caused by a combination of renal vasoconstriction and tubular sodium resorption at a high oxygen demand.

Dopamine increases renal oxygenation: a clinical study in post-cardiac surgery patients.

BACKGROUND: Imbalance of the renal medullary oxygen supply/demand relationship can cause ischaemic acute renal failure (ARF). The use of dopamine for prevention/treatment of ischaemic ARF has been questioned. It has been suggested that dopamine may increase renal oxygen consumption (RVO(2)) due to increased solute delivery to tubular cells, which may jeopardize renal oxygenation. Information on the effects of dopamine on renal perfusion, filtration and oxygenation in man is, however, lacking. We evaluated the effects of dopamine on renal blood flow (RBF), glomerular filtration rate (GFR), RVO(2) and renal O(2) demand/supply relationship, i.e. renal oxygen extraction (RO(2)Ex). METHODS: Twelve uncomplicated, mechanically ventilated and sedated post-cardiac surgery patients with pre-operatively normal renal function were studied. Dopamine was sequentially infused at 2 and 4 ug/kg/min. Systemic haemodynamics were evaluated by a pulmonary artery catheter. Absolute RBF was measured using two independent techniques: by the renal vein thermodilution technique and by infusion clearance of paraaminohippuric acid (PAH), with a correction for renal extraction of PAH. The filtration fraction (FF) was measured by the renal extraction of (51)Cr-EDTA. RESULTS: Neither GFR, tubular sodium reabsorption nor RVO(2) was affected by dopamine, which increased RBF (45-55%) with both methods, decreased renal vascular resistance (30-35%), FF (21-26%) and RO(2)Ex (28-34%). The RBF/CI ratio increased with dopamine. Dopamine decreased renal PAH extraction, suggestive of a flow distribution to the medulla. CONCLUSIONS: In post-cardiac surgery patients, dopamine increases the renal oxygenation by a pronounced renal pre-and post-glomerular vasodilation with no increases in GFR, tubular sodium reabsorption or renal oxygen consumption.