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.

A novel fluid-filled pressure wire avoids hydrostatic errors in physiologic measurements

Background

Hydrostatic pressure impacts intracoronary pressure measurements, generally causing overestimation of stenosis significance in the LAD and underestimation in non-LAD vessels [1–3]. Different cut-offs have been suggested for post-PCI FFR [4], corresponding to average hydrostatic effects [1–3]. Different cut-offs and stenosis misclassification may be avoided if hydrostatic effects are eliminated.

Purpose

We aimed to compare the effect of hydrostatic pressure on resting distal-to-aortic coronary pressure ratio (Pd/Pa) and FFR, using a conventional sensor-tipped- versus a novel fluid-filled pressure wire. Since the fluid-filled wire has an outside-the-body pressure transducer instead of a sensor at the tip, the fluid (saline) compensates for the hydrostatic pressure that is inside the patient's body.

Methods

We placed the sensor of a sensor-tipped wire and the measure point of a fluid-filled wire at the same location in the coronary vessel. By performing simultaneous measurements, we aimed to assess the relationship between vertical height differences and distal pressure (Pd).

We measured the vertical height difference between the tip of the guide catheter and the measure point, by changing the vertical position of the cath lab table and assessing the total distance in mm between the two table positions.

Results

The two wires were used simultaneously in 21 arteries. The lower in the coronary tree the measurements were made (e.g., in the LCX or RCA), the higher the Pd value by the conventional wire was, compared to the novel wire; the higher the measurement was made (e.g., in the LAD), the lower the Pd value.

After we corrected for hydrostatic effect on the sensor-tipped wire using the height measurement (0.77 mmHg/cm [2]), sensor-tipped wire pressure correlated better with fluid-filled wire pressure (R=0.73 vs. R=0.89 at rest and R=0.83 vs. R=0.96 at hyperaemia).

Drift was also compared in 31 simultaneous measurements. The fluid-filled wire demonstrated less drift than the sensor-tipped wire (standard deviation 0.11 vs. 0.18). With an increasing number of cases, less drift was observed, possibly learning curve-related.

Finally, we compared measurements of pressure-derived CFR using the fluid-filled wire, versus echocardiography-CFR (n=10) and bolus thermodilution-CFR (n=11). Pressure-derived CFR with the fluid-filled wire correlated to echocardiography-CFR and thermodilution-CFR (R=0.69 and R=0.76 respectively). Sensor-tipped wire pressure-derived CFR did not correlate to thermodilution-CFR measurements (n=11; R=−0.57).

Conclusions

Hydrostatic pressure introduces a variable error in conventional intracoronary pressure measurements. Resting indices are more susceptible to the hydrostatic error than hyperaemic. There is a slight learning curve associated with use of the novel wire, but hydrostatic errors in physiologic measurements can be avoided thanks to the wire's fluid-filled design and external pressure transducer.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swedish Governmental Agency for Innovation Systems (Vinnova)

Takotsubo syndrome-like model in rats with high reproducibility and low mortality

Background/Purpose

Takotsubo syndrome (TS) is an acute form of heart failure with similar mortality and clinical presentation as myocardial infarction. The pathophysiology of the potentially life-threatening syndrome is only partially understood. This experimental study aimed to produce a human-like TS model with high reproducibility and low mortality. Rats have been the small-animal model of choice for preclinical studies within the cardiovascular field, successfully translating gained knowledge to humans. A relevant animal model can aid in elucidating mechanisms behind TS and serve as a platform for developing evidence-based treatment guidelines specific for the disease, which are currently missing.

Methods

190 Sprague Dawley rats (male, ∼300 g, ∼47 d) were infused i.v. with a single dose of the β-adrenergic agonist isoprenaline. The first study group was randomized by infusion time (ranging from 1 min to 60 min) while maintaining a fixed total dose (6.25 mg/kg), and the second group by total dose (0.1–50 mg/kg) with specified infusion time. The studies were replicated with saline infusion as a control. This study looked at mortality, the incidence of apical akinesia, the extent of apical akinesia, and recovery time. ECG, HR, SpO2, and temperature were monitored during the induction phase (<60 min) and at time points for imaging. High-resolution speckle-tracking echocardiography was used to study heart function for up to 30 days. The study followed the principles of laboratory animal care and was approved by our institution's Animal Ethics Committee.

Results

Mechanical dyssynchrony preceded global contractile dysfunction and development of transient apical akinesia. LV function and contractility normalised after 1 to 7 days. All surviving rats showed normal behaviour, ECG, and imaging at 30 days. TS-like phenotype was achieved in 92.9% of survivors. Mortality at 30-day was 6.7%. The deceased animals developed complications like TS patients including heart failure, malignant arrhythmias, LV mural thrombus formation, cardiogenic shock. Longer infusion time was associated with increased mortality (p=0.002), but not with the incidence of akinesia (p=0.818). The extent of apical akinesia decreased at the shortest infusion time (1 min) while at 7.5 minutes and above, it did not differ. The replication study validated these findings, although variability in incidence and mortality was seen across the groups.

Conclusions

This study provides a highly reproducible TS-like model with low mortality and excellent translational potential. High-resolution imaging and the natural course demonstrated the presence of the most critical characteristics of TS-like phenotype as in humans. The model also validates other findings related to TS including variability in the susceptibility to develop TS-like phenotype and complications. Our model provides a solid experimental platform for future preclinical studies of TS.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): ALF - Swedish Research Council

Does the quality index of adherence to the evidence-based guidelines predict mortality in patients with myocardial infarction?

Background

The SWEDEHEART quality index of hospitals' adherence to the evidence-based (EB) guidelines for myocardial infarction (MI) patients has been continuously used for several decades in Sweden. The grading protocol is based on the consensus among hospitals. The hospitals are awarded points (0, 0.5, 1) for each of the 11 indicators depending on the proportion of patients who received EB treatment and achieved treatment goals. The 11 indicators at present are reperfusion treatment in STEMI (yes/no), time to-reperfusion treatment in STEMI, time to revascularisation in NSTEMI, P2Y12 antagonists at discharge, ACE-inhibitor/ARB at discharge, the proportion of patients at follow-up, smoking cessation at one-year, participation in a physical exercise program, target LDL-cholesterol and target blood pressure at one year.

Purpose

To evaluate whether the SWEDEHEART quality index predicts mortality in patients with MI.

Methods

We used data for all MI patients reported to the SWEDEHEART registry from 72 hospitals in Sweden between 2015–2021. We calculated the difference in quality index between 2021 and 2015. The hospitals were divided into quintiles based on the difference in the score. Logistic regression with log-time offset was used to adjust for confounders (age, gender, diabetes, hypertension, hyperlipidemia, STEMI/NSTEMI, cardiac arrest before admission, occupation status, history of heart failure, prior MI, prior PCI, prior CABG, cardiogenic shock).

Results

We identified 98,635 patients with MI, 32,608 (33.1%) were women and 34,198 (34.7%) had STEMI. The average age was 70.8±12.2 years. The median follow-up time was 2.7 years (IQR 1.06–4.63). The crude all-cause mortality rate was 5.5% at 30-days and 22.3% after long-term follow-up. Most hospitals (72.1%) improved their quality index on average by 3.4% per year (P<0.001). The increase in the quality index continued during COVID-19 pandemic (2020–2021) with average increase of 8.6%, 95% CI, 0.97–1.02; P<0.001. The median change in SWEDEHEART quality index score among the quintiles were −1.5 (Q1), 0,5 (Q2), 2,5 (Q3), 3 (Q4), and 4 (Q5). We found no difference in mortality between the quintiles at 30-days (OR 0.99; 95% CI 0.97–1.02; p=1.02) and long-term (OR 1.01; 95% CI 0,99–1.02; p=0.850).

Conclusion

The SWEDEHEART quality index provides valuable descriptive information about hospitals' adherence to the guidelines. However, the index, in its current form, does not predict mortality in patients with MI.

Funding Acknowledgement

Type of funding sources: None.

Early changes in myocardial stunning and biomarkers after ST-elevation myocardial infarction compared to the takotsubo syndrome

Background

Takotsubo syndrome (TS) and ST-elevation myocardial infarction (STEMI) are both characterized by sudden cessation of myocardial contractions (myocardial stunning) as well as elevation of cardiac troponins and B-type natriuretic peptides (BNP). Whereas STEMI results in variable degrees of necrosis and persistent cardiac dysfunction, TS results in little to any necrosis and full recovery of cardiac function. No “head-to-head” comparison of the temporal resolution of myocardial stunning and serum biomarkers in STEMI versus takotsubo has been done.

Purpose

To compare the time course of the recovery of cardiac function and serum biomarkers over the acute and subacute phases of takotsubo and STEMI, with patients with STEMI further subdivided into anterior and non-anterior STEMI.

Method

The Stunning In Takotsubo and Acute Myocardial Infarction (STAMI) study is a prospective, multi-center study that enrolls patients with TS or STEMI without known pre-existing cardiac dysfunction. Echocardiography, laboratory testing (including troponins and NT-proBNP), and ECG are acquired within 4 hours after acute coronary angiography and at 24±6, 48±12, 72±12 hours and 7±1, 14±2, and 30±2 days. The primary endpoint is the proportion of reversible myocardial akinesia resolved after 72 hours (Figure 1), as determined by echocardiography. Secondary endpoints include troponin-I, troponin-T, and NT-proBNP.

Results

Preliminary results from 155 patients with STEMI (78 anterior STEMI and 77 non-anterior STEMI) and 32 patients with TS are presented in Figure 1. Mean (SD) age was similar for patients with takotsubo (67±14), anterior STEMI (68±11), and non-anterior STEMI (68±10). All 3 groups showed substantial recovery of cardiac function over the course of the study, with the most pronounced recovery of cardiac function in TS. Compared to both STEMI groups, the TS group also had lower troponin-I to troponin-T ratio, and higher NT-proBNP (Figure 2). The proportion of reversible akinesia that had recovered at 72 hours was similar in patients with TS, anterior STEMI and non-anterior STEMI (p=0.8414).

Conclusion

The STAMI study will provide the comprehensive assessment of cardiac function and serum biomarker profile of patients with takotsubo and STEMI over the early course of the disease. Preliminary data from the study suggest that early myocardial functional recovery is more substantial but follows a similar time-course in takotsubo and STEMI. The differences in the magnitude of troponin elevation after takotsubo versus STEMI were more pronounced for troponin-I than T.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ERC - European Research Council

Maximally tolerated guideline-directed medical therapy and barriers to optimization in patients with heart failure with reduced ejection fraction: the COAPT trial

Background

The COAPT trial of MitraClip therapy employed a central screening eligibility committee (CSEC) of heart failure (HF) experts to ensure the use of maximally tolerated guideline-directed medical therapy (GDMT) and systematically document intolerances in all potential patients prior to approval for randomization.

Purpose

To describe the percentage of GDMT classes, doses tolerated, predictors of intolerance, and specific intolerances limiting GDMT among patients approved for randomization by the CSEC.

Methods

We analyzed baseline use, dose, and intolerances of i) angiotensin-converting enzyme inhibitors (ACEI), angiotensin II receptor blockers (ARB) or angiotensin receptor neprilysin inhibitor (ARNI); ii) beta-blockers (BB); and iii) mineralocorticoid receptor antagonists (MRA) in the CSEC-approved COAPT population with HF with reduced ejection fraction (HFrEF; LVEF ≤40%). We analyzed variables associated with GDMT tolerance.

Results

In COAPT, 464 patients had HFrEF and complete screening medication information. Any dose of all 3, 2 or 1 GDMT classes were tolerated in 39%, 39% and 20% of patients respectively; only 2% of patients (n=9) could not tolerate any GDMT (Figure 1). BB were prescribed in the most (93%) patients followed by ACEI/ARB/ARNI (69%) and MRA (55%). Intolerances limiting each GDMT class differed, but hypotension and kidney dysfunction were most common (Figure 2). No patients tolerated goal doses of all 3 GDMT classes. For BB, only 32% tolerated ≥50% of the goal dose; while for ACEI/ARB/ARNI, no patients achieved goal doses, and only 1% tolerated ≥50% of the goal dose. For MRA, 86% of patients tolerated 25mg/day or less. Patients intolerant of BB were less likely to tolerate an ACEI/ARB/ARNI (OR 0.39, 95% CI 0.20–0.76; p=0.004) but not a MRA (p=0.21) compared with patients tolerating a low dose BB. Patients intolerant of MRA were less likely to tolerate ACEI/ARB/ARNI therapy (OR 0.37, 95% CI 0.25–0.57; p&lt;0.0001) but not a BB (p=0.31) compared with patients tolerating MRA. Patients tolerating low dose ACEI/ARB/ARNI had a higher baseline mean eGFR (52±21 versus 40±21 ml/min/m2; p&lt;0.0001) compared with patients intolerant of ACEI/ARB/ARNI. Likewise, patients tolerating MRA had a higher baseline mean eGFR (52±21 versus 42±21 ml/min/m2; p&lt;0.0001) compared with patients intolerant of MRA.

Conclusion

In a contemporary trial in which HF specialists ensured GDMT optimization, many patients had medical intolerances prohibiting use of one or more GDMT classes, and few patients tolerated target doses. These findings indicate medical intolerances are the primary cause of low GDMT prescription rates in patients with moderate to severe HFrEF. Yet, use of GDMT in this very ill population was much better than “real world” registries of HFrEF suggesting that mandating careful CSEC review prior to study enrollment is important for clinical trials having the objective of randomizing a maximally treated patient cohort.

Funding Acknowledgement

Type of funding sources: None.

Cerebrovascular events after transcatheter mitral valve repair or guideline-directed medical therapy in patients with mitral regurgitation and heart failure in the COAPT trial

Background

Our knowledge regarding the risk of cerebrovascular events (CVE) in patients with heart failure (HF) and severe secondary mitral regurgitation (SMR) treated by transcatheter mitral valve repair (TMVr) is limited.

Purpose

To examine the incidence, predictors, timing, and prognostic impact of CVE in patients with heart failure and SMR treated with TMVr vs guideline-directed medical therapy (GDMT) alone.

Methods

In the COAPT trial, 614 patients with HF with moderate-to-severe or severe SMR were randomized to TMVr with the MitraClip + GDMT vs GDMT alone. After 2 years, patients who were randomized to GDMT alone could crossover and undergo TMVr. CVE (defined as stroke or TIA) were adjudicated by an independent clinical events committee.

Results

A total of 43 CVE occurred in 42 patients within 3-year follow-up (34 strokes and 9 TIAs; 1 patient had both). CVE occurred in 10.0% (n=20) of patients randomized to TMVR and 11.3% (n=22) of patients randomized to GDMT alone (p=0.53) (Figure). Of the 22 CVE in the GDMT alone group, 3 occurred after the patient had crossed over to TMVr. The incidence rates in the TMVr and GDMT groups were similar within the first 3 months (incidence rate ratio [IRR] 0.78, 95% CI 0.17–3.48, p=0.74) and between 3 months and 3 years (IRR 0.83, 95% CI 0.43–1.60, p=0.58) after randomization. After multivariable adjustment, baseline estimated glomerular filtration rate (eGFR) was associated with CVE in the overall population (HR per 5 ml/min increase in eGFR 0.91, 95% CI 0.84–0.99, p=0.03). Peripheral vascular disease was associated with CVE in patients treated by GDMT (HR=3.21, 95% CI [1.35, 7.67]) but not TMVr (HR 0.53 95% CI 0.12–2.24; p-interaction=0.04). In contrast, baseline chronic oral anticoagulation use was associated with a reduced risk of CVE in patients in the TMVr group (HR 0.18, 95% CI 0.05–0.63) but not in the GDMT alone group (HR 1.66, 95% CI 0.70–3.94; p-interaction=0.004). In a time-adjusted multivariable analysis, CVE was associated with a higher risk of death (HR 2.51, 95% CI 1.54–4.08; p=0.0002), a risk that was marked in the first 30 days after the event (HR 14.21, 95% CI 7.30–27.97, p&lt;0.0001), and declined thereafter (HR 1.37, 95% CI 0.72–2.59, p=0.34).

Conclusions

In patients with HF and severe SMR, CVE at 3 years was not infrequent, increased linearly over time, was similar after treatment with the MitraClip and GDMT alone, and was associated with a marked increase in all-cause death. Whether anticoagulation is especially effective at preventing CVE in patients treated by TMVr, as suggested by this report, warrants further study.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Abbott Figure 1

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.

Comparative Effectiveness of CABG versus PCI in Patients with Ischemic Heart Disease: insights from SWEDEHEART Registry

Background

Several studies have compared CABG to PCI as revascularization treatment in patients with ischemic heart disease (IHD). However, it remains unclear which revascularization strategy carries survival benefits in the long-term.

Methods

We used data from the SWEDEHEART (Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry for all hospital admissions at 13 cardiac care centers within Västra Götaland County in Sweden (∼20% of all SWEDEHEART data). The database contains &gt;1000 clinical variables documenting the entire process of acute coronary hospital care. All patients hospitalized for stable angina or NSTE-ACS during the period 2000–2018 were included in the analysis. We used a propensity score-adjusted Cox proportional-hazards regression with hospitals as random-effect variables. We adjusted for patients' demographics, socio-economic status, traditional risk factors, comorbidities, the severity of coronary artery disease, left ventricular function, calendar year and medication at discharge. For sensitivity analysis, we used the instrumental variable estimator for the Cox proportional-hazards model (with treating hospital as a treatment-preference instrument) to simultaneously deal with the problems of unmeasured confounding and censoring of the outcome. The primary outcome was all-cause mortality.

Results

In total, 11,896 patients were included in the study. Of these, 3,129 (26.3%) were women. 20.4% had diabetes and 10.4% had a previous myocardial infarction. The mean age was 66.7±10.7, and 42.9% were &gt;70 years old. 61.5% had three-vessel and/or left main disease. Median follow-up time was 5.7 years (range 1 day-18.2 years). Revascularization therapy after coronary angiography was PCI in 9449 (79.4%) and CABG in 2,447 (20.6%) patients. CABG patients were more likely to have diabetes, left main/multivessel disease and heart failure. The number of revascularized patients with PCI increased by 6.4% per calendar year (P&lt;0.001). There were 2,481 (20.9%) deaths. CABG was associated with a lower risk of death compared to PCI (HR 0.81; 95% CI 0.69–0.95; P=0.011. We found no evidence for treatment heterogeneity between the revascularization strategy and age, gender, diabetes, heart failure and indication for revascularization (all P-interaction &gt;0.05). Results from the sensitivity analysis support the conclusions from the primary model.

Conclusions

In hospitalized patients due to IHD, revascularization with CABG was associated with superior long-term survival compared to PCI.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Heart and Lung Foundation, ALF Västra Götaland, Swedish Scientific Council

Long-term survival in patients with coronary artery disease undergoing percutaneous coronary intervention with or without intracoronary pressure wire guidance: a report from SCAAR

Background

Intracoronary pressure wire measurements of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) provide decision-making guidance during percutaneous coronary intervention (PCI). However, limited data exist on the impact of FFR/iFR on long-term clinical outcomes in patients with stable angina, unstable angina (UA)/non-ST-segment elevation myocardial infarction (NSTEMI), or STEMI.

Methods

We used data from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR) on all patients in Sweden undergoing PCI (with or without FFR/iFR guidance) for stable angina, UA/NSTEMI, or STEMI between January 2005 and March 2018. The primary endpoint was all-cause mortality and the secondary endpoints were stent thrombosis or restenosis and periprocedural complications. The primary model was multilevel Cox proportional-hazards regression using an instrumental variable (IV) to adjust for known and unknown confounders with treating hospital as a treatment-preference instrument. The following variables were entered into Cox proportional-hazards regression in addition to the IV: age, sex, diabetes, indication for PCI, severity of coronary disease, smoking status, hypertension, hyperlipidemia, previous myocardial infarction, previous PCI, previous coronary artery bypass graft, type of stent.

Results

In total, 151,001 patients underwent PCI: 31,514 (20.9%) for stable angina, 74,982 (49.6%) for UA/NSTEMI, and 44,505 (29.5%) for STEMI. Of these, FFR/iFR guidance was used in 11,433 patients (7.6%): 5029 (44.0%) with stable angina, 5989 (52.4%) with UA/NSTEMI, and 415 (3.6%) with STEMI; iFR was used in 1156 (10.1%) of these patients. After a median follow-up of 1784 (range 1–4824) days, the FFR/iFR group had lower adjusted risk estimates for all-cause mortality [hazard ratio (HR) 0.79; 95% confidence interval (CI) 0.69–0.91; P=0.001] and stent thrombosis and restenosis (HR 0.13; 95% CI 0.09–0.19; P&lt;0.001). The number of periprocedural complications did not differ significantly between the groups (odds ratio 0.69; 95% CI 0.30–1.55; P=0.368). There was no interaction between FFR/iFR and indication for PCI. We found no difference between FFR and iFR (HR 1.12; 95% CI 0.90–1.59; P=0.216).

Conclusions

In this observational study, the use of FFR/IFR was associated with a lower risk of long-term mortality in patients undergoing PCI for stable angina, UA/NSTEMI, or STEMI. Our study supports the current European and American guidelines for the use of FFR/iFR during PCI and shows that intracoronary pressure wire guidance has prognostic benefit in patients with stable angina as well as in patients with the acute coronary syndrome.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Heart and Lung Foundation, ALF Västra Götaland, Swedish Scientific Council

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.

P1966Impact of coronary artery calcification on long-term outcomes after implantation of first and second-generation drug-eluting stents: a patient-level analysis of 18 randomized trials

Background

Available data on the long-term impact of coronary artery calcification (CAC) after percutaneous coronary intervention (PCI) with drug-eluting stents (DES) are limited.

Purpose

We evaluated the long-term impact of CAC on outcomes after PCI and the respective performance of first- and second-generation DES.

Methods

We pooled patient-level data from 18 randomized trials evaluating DES categorized according to the presence of angiographic core lab-confirmed moderate or severe CAC in any target lesion. Outcome measures of interest were the patient-oriented composite endpoint (POCE; death, myocardial infarction [MI], or any revascularization), the device-oriented composite endpoint of target lesion failure (TLF; cardiac death, target vessel MI or ischemia-driven target lesion revascularization), and definite or probable stent thrombosis (ST). Multivariable Cox proportional regression with study as a random effect was used to assess 5-year outcomes.

Results

A total of 19,833 patients were included. Moderate or severe CAC was present in 6211 (31.3%) patients and associated with increased 5-year risk of the POCE (adjHR 1.12, 95% CI 1.05–1.20, p<0.001), TLF (adjHR 1.21, 95% CI 1.09–1.35, p<0.001), and a trend for greater ST (adjHR 1.24, 95% CI 0.99–1.54, p=0.06). In patients with CAC, second-generation DES were associated with a reduction in the 5-year risk of TLF and ST, and a trend for reduced POCE compared with first-generation DES (Table).

Conclusion

In this large-scale study, target lesion moderate or severe CAC was associated with adverse patient- and device-related outcomes at 5 years, risks that were reduced but not eliminated with second-generation DES.

Acknowledgement/Funding

This investigator-sponsored study was funded by Abbott Vascular.

Renal effects of norepinephrine-induced variations in mean arterial pressure after liver transplantation: A randomized cross-over trial

BACKGROUND

Acute kidney injury is commonly seen after liver transplantation. The optimal perioperative target mean arterial pressure (MAP) for renal filtration, perfusion and oxygenation in liver recipients is not known. The effects of norepinephrine-induced changes in MAP on renal blood flow (RBF), oxygen delivery (RDO₂ ), glomerular filtration rate (GFR) and renal oxygenation (=renal oxygen extraction, RO₂ Ex) were therefore studied early after liver transplantation.

METHODS

Ten patients with an intra- and post-operative vasopressor-dependent systemic vasodilation were studied early after liver transplantation during sedation and mechanical ventilation. To achieve target MAP levels of 60, 75 and 90 mm Hg, the norepinephrine infusion rate was randomly and sequentially titrated. At each target MAP, data on cardiac index (CI), RBF and GFR were obtained by transpulmonary thermodilution (PiCCO), the renal vein thermodilution technique and renal extraction of chromium ethylenediaminetetraaceticacid (⁵¹ Cr-EDTA), respectively. Renal oxygen consumption (RVO₂ ) and extraction (RO₂ Ex) were calculated according to standard formulas.

RESULTS

At a target MAP of 75 mm Hg, CI (13%), RBF (18%), RDO₂ (24%), GFR (31%) and RVO₂ (20%) were higher while RO₂ Ex was unchanged compared to a target MAP of 60 mm Hg. Increasing MAP from 75 up to 90 mm Hg increased RVR by 38% but had no further effects on CI, RBF, RDO₂ or GFR.

CONCLUSIONS

In patients undergoing liver transplantation, RBF and GFR are pressure-dependent at MAP levels below 75 mm Hg. Our results suggest that MAP should probably be targeted to approximately 75 mm Hg for optimal perioperative renal filtration, perfusion and oxygenation in patients undergoing liver transplantation.

Renal tubular injury during cardiopulmonary bypass as assessed by urinary release of N-acetyl-ß-D-glucosaminidase

BACKGROUND

Acute kidney injury (AKI) is a common complication with a major impact on morbidity and mortality after cardiac surgery with cardiopulmonary bypass (CPB). The aim of the present study was to perform a detailed analysis on the release of the tubular injury biomarker N-acetyl-b-D-glucosaminidase (NAG) during and early after CPB and to describe independent predictors of maximal tubular injury. We hypothesized that renal tubular injury occurs early after the onset of CPB.

METHODS

In this prospective observational study, we included 61 patients undergoing open cardiac surgery with an expected CPB duration exceeding 60 min. The urinary NAG levels were measured at 30 min intervals during CPB, as well as early (30 min) after CPB and post-operatively. Independent predictors of tubular injury were identified using an Interquantile multivariate regression model.

RESULTS

Already 30 min after the onset of CPB, NAG excretion was significantly increased (P < 0.001), followed by a sixfold peak increase after discontinuation of CPB (P < 0.001). In the multivariable regression model, CPB duration (P < 0.05) and the degree of rewarming during CPB (P < 0.05), were independent predictors of peak NAG excretion.

CONCLUSION

In cardiac surgery, a renal tubular cell injury is seen early after onset of CPB with a peak biomarker increase early after end of CPB. The magnitude of this tubular injury is independently related to CPB duration and the degree of rewarming. Efforts made to decrease the CPB duration and to avoid hypothermia and the need for rewarming may decrease the risk for tubular injury.

Takotsubo syndrome in hemodynamically unstable patients admitted to the intensive care unit - a retrospective study

INTRODUCTION

Takotsubo syndrome (TS) is an acute cardiac condition that is often triggered by critical illness but that has rarely been studied in the intensive care unit (ICU) setting. The aim of this study was to (i) estimate the incidence of TS in a hemodynamically unstable ICU-population; (ii) identify predictors of TS in this population; (iii) study the impact of TS on prognosis and course of hospitalization.

METHODS

Medical records from all patients admitted to our general ICU from 2012 to 2015 were analyzed. TS was defined as having transient regional wall motion abnormalities (RWMA) with a typical pattern not attributable to a history of coronary artery disease or acute coronary syndromes.

RESULTS

Out of 6470 patients admitted to the ICU, echocardiography due to hemodynamic instability was performed in 1051 patients; 467 had LV dysfunction and 59 fulfilled TS criteria. Patients with TS had higher SAPS 3 scores on admission than patients with normal LV function. Septic shock, cardiac arrest, cerebral mass lesion, female sex and low pH were independently associated with TS on admission. Patients with TS needed more ICU resources measured by higher NEMS scores and longer ICU-stay. Crude mortality was higher in TS patients (32%) vs the ICU-population (20%, P = 0.020), but there were no differences in a SAPS 3 adjusted analysis.

CONCLUSION

TS was not an uncommon cause of LV dysfunction in hemodynamically unstable ICU-patients. Furthermore, TS was associated with a more complex disease. TS is a complication to take in consideration in the critically ill.

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.

Early treatment with isoflurane attenuates left ventricular dysfunction and improves survival in experimental Takotsubo

BACKGROUND

Takotsubo syndrome (TS) is an acute cardiac condition, often triggered by critical illness, for which no specific treatment exists. Previously, we showed that isoflurane can prevent experimental TS. The aim of this study was to evaluate the potential treatment effects of isoflurane. Our primary hypothesis was that early treatment with isoflurane attenuates left ventricular akinesia in experimental TS.

METHOD

In propofol-sedated animals, TS was induced by an intraperitoneal bolus of isoprenaline (50 mg/kg). Animals were randomized to one of six groups (n = 15 in each group), and 1% isoflurane was administered for 90 min in all groups. Isoflurane treatment was started at 0, 10, 30 (early treatment) or 120 (late treatment) minutes after isoprenaline injection. One additional late treatment group received isoflurane 0.5% for 180 min. A control group did not receive isoflurane. Left ventricular (LV) echocardiographic examination was performed at 90 min and 48 h after isoprenaline. Mortality was assessed at 48 h.

RESULTS

Median degree of LV akinesia at 90 min was 24% in the control group and 0% in the early treatment groups (P < 0.001). Stroke volume, cardiac output and LV ejection fraction were higher in the early treatment groups vs. controls (P < 0.01). Mortality was lower in the early treatment groups (24%) vs. controls (86%) (P < 0.001). Mortality did not differ between the late treatment groups and controls.

CONCLUSION

Early treatment with isoflurane attenuates the LV akinesia and improves survival in experimental TS. Isoflurane sedation in patients at risk of developing Takotsubo syndrome could be a subject for future studies.

Anaesthetic-induced cardioprotection in an experimental model of the Takotsubo syndrome - isoflurane vs. propofol

BACKGROUND

Takotsubo syndrome (TS) is an acute cardiac condition with a substantial mortality for which no specific treatment is available. We have previously shown that isoflurane attenuates the development of left ventricular (LV) dysfunction in an experimental TS-model. We compared the effects of equi-anaesthetic doses of isoflurane, propofol and ketamine+midazolam on haemodynamics, global and regional LV systolic function and the activation of intracellular metabolic pathways in experimental TS. We hypothesized that cardioprotection in experimental TS is specific for isoflurane.

METHODS

Forty-five rats were randomized to isoflurane (0.6 MAC, n = 15), propofol (bolus 200 mg/kg+360 mg/kg/h, n = 15) or ketamine (100 mg/kg)+midazolam (10 mg/kg, n = 15) anaesthesia. Arterial pressure, heart rate and body temperature were continuously measured and arterial blood gas analysis was performed intermittently. TS was induced by intraperitoneal injection of isoprenaline, 50 mg/kg. LV echocardiography was performed 90 min after isoprenaline injection. Apical cardiac tissue was analysed by global discovery proteomics and pathway analysis.

RESULTS

Isoprenaline-induced changes in arterial blood pressure, heart rate or body temperature did not differ between groups. LV ejection fraction was higher and extent of LV akinesia was lower with isoflurane, when compared with the propofol and the ketamine+midazolam groups. In this TS-model, the proteomic analysis revealed an up-regulation of pathways involved in inflammation, coagulation, endocytosis and lipid metabolism. This up-regulation was clearly attenuated with isoflurane compared to propofol.

CONCLUSION

In an experimental model of TS, isoflurane, but not propofol, exerts a cardioprotective effect. The proteomic analysis suggests that inflammation might be involved in pathogenesis of TS.

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−1 · m−2) 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-β-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-β-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.

Pressure-dependent changes in haematocrit and plasma volume during anaesthesia, a randomised clinical trial

BACKGROUND

Induction of general anaesthesia has been shown to cause haemodilution and an increase in plasma volume. The aim of this study was to evaluate whether prevention of hypotension during anaesthesia induction could avoid haemodilution.

METHODS

Twenty-four cardiac surgery patients, 66 ± 10 years, were randomised to receive either norepinephrine in a dose needed to maintain mean arterial blood pressure (MAP) at pre-anaesthesia levels after induction or to a control group that received vasopressor if MAP decreased below 60 mmHg. No fluids were infused. Changes in plasma volume were calculated with standard formula: 100 × (Hct(pre)/Hct(post) - 1)/(1 - Hct(pre)). Arterial blood gas was analysed every 10 minutes and non-invasive continuous haemoglobin (SpHb) was continuously measured.

RESULTS

Pre-anaesthesia MAP was 98 ± 7 mmHg. Ten minutes after anaesthesia induction, the haematocrit decreased by 5.0 ± 2.5% in the control group compared with 1.2 ± 1.4% in the intervention group, which corresponds to increases in plasma volume by 310 ml and 85 ml respectively. MAP decreased to 69 ± 15 mmHg compared to 92 ± 10 mmHg in the intervention group. The difference maintained throughout the 70 min intervention period. The change in haemoglobin level measured by blood gas analysis could not be detected by SpHb measurement. The mean bias between the SpHb and blood gas haemoglobin was 15 g/l.

CONCLUSION

During anaesthesia induction, haematocrit decreases and plasma volume increases early and parallel to a decrease in blood pressure. This autotransfusion is blunted when blood pressure is maintained at pre-induction levels with norepinephrine.

Incidence and Treatment Options for Massive Pulmonary Embolism in Sweden

Swedish Healthcare is organised by relatively independent counties which are responsible for the appropriateness of delivered care. As a consequence, few formal guidelines are issued by national authorities or professional societies, which is the case for the treatment of pulmonary embolism (PE). The yearly incidence of PE in Swedish adults was 86/100,000 in 2011, corresponding to approximately 6000 cases with an overall mortality of 6.5%. Acute massive PE with circulatory shock carries mortality up to 50% but its true incidence in Sweden is not known. First-line treatment is intravenous thrombolysis but non-pharmacological alternatives for cases where thrombolysis has no effect or is contraindicated have recently undergone technical development. This includes catheter fragmentation, surgical embolectomy and extracorporeal circulatory support, which may be used as a bridge to further treatment in very unstable patients. This article summarises the treatment options for acute massive PE and their rationale as seen from a Swedish perspective.

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.

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.

Importance of circulating IGF-1 for normal cardiac morphology, function and post infarction remodeling

IGF-1 plays an important role in cardiovascular homeostasis, and plasma levels of IGF-1 correlate inversely with systolic function in heart failure. It is not known to what extent circulating IGF-1 secreted by the liver and local autocrine/paracrine IGF-1 expressed in the myocardium contribute to these beneficial effects on cardiac function and morphology. In the present study, we used a mouse model of liver-specific inducible deletion of the IGF-1 gene (LI-IGF-1 -/- mouse) in an attempt to evaluate the importance of circulating IGF-I on cardiac morphology and function under normal and pathological conditions, with an emphasis on its regulatory role in myocardial phosphocreatine metabolism. Echocardiography was performed in LI-IGF-1 -/- and control mice at rest and during dobutamine stress, both at baseline and post myocardial infarction (MI). High-energy phosphate metabolites were compared between LI-IGF-1 -/- and control mice at 4 weeks post MI. We found that LI-IGF-1 -/- mice had significantly greater left ventricular dimensions at baseline and showed a greater relative increase in cardiac dimensions, as well as deterioration of cardiac function, post MI. Myocardial creatine content was 17.9% lower in LI-IGF-1 -/- mice, whereas there was no detectable difference in high-energy nucleotides. These findings indicate an important role of circulating IGF-1 in preserving cardiac structure and function both in physiological settings and post MI.

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.

Norepinephrine causes a pressure-dependent plasma volume decrease in clinical vasodilatory shock

BACKGROUND

Recent experimental studies have shown that a norepinephrine-induced increase in blood pressure induces a loss of plasma volume, particularly under increased microvascular permeability. We studied the effects of norepinephrine-induced variations in the mean arterial pressure (MAP) on plasma volume changes and systemic haemodynamics in patients with vasodilatory shock.

METHODS

Twenty-one mechanically ventilated patients who required norepinephrine to maintain MAP > or =70 mmHg because of septic/postcardiotomy vasodilatory shock were included. The norepinephrine dose was randomly titrated to target MAPs of 60, 75 and 90 mmHg. At each target MAP, data on systemic haemodynamics, haematocrit, arterial and mixed venous oxygen content and urine flow urine were measured. Changes in the plasma volume were calculated as 100 x (Hct(pre)/Hct(post)-1)/ (1-Hct(pre)), where Hct(pre) and Hct(post) are haematocrits before and after intervention.

RESULTS

Norepinephrine doses to obtain target MAPs of 60, 75 and 90 mmHg were 0.20+/-0.18, 0.29+/-0.18 and 0.42+/-0.31 microg/kg/min, respectively. From 60 to 90 mmHg, increases in the cardiac index (15%), systemic oxygen delivery index (25%), central venous pressure (CVP) (20%) and pulmonary artery occlusion pressure (33%) were seen, while the intrapulmonary shunt fraction was unaffected by norepinehrine. Plasma volume decreased by 6.5% and 9.4% (P<0.0001) when blood pressure was increased from 60 to 75 and 90 mmHg, respectively. MAP (P<0.02) independently predicted the decrease in plasma volume with norepinephrine but not CVP (P=0.19), cardiac index (P=0.73), norepinephrine dose (P=0.58) or urine flow (P=0.64).

CONCLUSIONS

Norepinephrine causes a pressure-dependent decrease in the plasma volume in patients with vasodilatory shock most likely caused by transcapillary fluid extravasation.

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.