The role of cardiac power and lactate clearance as an indicator of resuscitation success among pediatric patients with shock in the intensive care unit of Cipto Mangunkusumo Hospital

BACKGROUND

Shock in children remains the primary cause of mortality and morbidity worldwide. Furthermore, its management outcome is improved using many hemodynamic parameters, such as cardiac power (CP) and lactate clearance (LC). Cardiac power is a contractility index based on the measurement of flow and pressure, and it is a relatively new hemodynamic parameter with limited studies. In contrast, LC has been proven useful as a target outcome in shock resuscitation. This study aims to explore the values of CP and LC in pediatric shock and their association with clinical outcomes.

METHODS

This prospective observational study was conducted on children (1 month-18 years old) with shock at Cipto Mangunkusumo Hospital, Indonesia, from April to October 2021. We measured CP using ultrasonic cardiac output monitoring (USCOM®) and serum lactate levels at 0, 1, 6, and 24 h post-initial resuscitation. Subsequently, the variables were described and analyzed with the resuscitation success, length of stay, and mortality.

RESULTS

A total of 44 children were analyzed. There were 27 (61.4%), 7 (15.9%), 4 (9.1%), 4 (9.1%), and 2 (4.5%) cases of septic, hypovolemic, cardiogenic, distributive, and obstructive shock, respectively. Within the first 24 h post-initial resuscitation, CP and LC had an increasing trend. Compared to children who had successful resuscitation, those who did not have successful resuscitation had similar CP at all time points (p > 0.05) and lower LC at 1 and 24 h post-initial resuscitation (p < 0.05). Lactate clearance was an acceptable predictor of resuscitation success (area under the curve: 0.795 [95% CI: 0.660-0.931]). An LC of 7.5% had a sensitivity, specificity, positive predictive value, and negative predictive value of 75.00%, 87.5%, 96.43%, and 43.75%, respectively. Lactate clearance in the first hour post-initial resuscitation had a weak correlation (r=-0.362, p < 0.05) with hospital length of stay. We found no difference in CP and LC among survivors compared to nonsurvivors.

CONCLUSIONS

We found no evidence that CP was associated with resuscitation success, length of stay, or mortality. Meanwhile, higher LC was associated with successful resuscitation and shorter length of stay at the hospital, but not mortality.

Age- and sex-stratified normal values for circulatory and ventilatory power during ramp exercise derived from a healthy Japanese population

Circulatory power (CP) and ventilatory power (VP), obtained by cardiopulmonary exercise testing (CPX), have been suggested to be excellent prognostic markers for heart failure. However, the normal values of these parameters in healthy Japanese populations remain unknown; thus, we aimed to investigate these values in such a population. A total of 391 healthy Japanese participants, 20-78 years of age, underwent CPX with a cycle ergometer with ramp protocols. Systolic blood pressure (SBP), heart rate, oxygen uptake ([Formula: see text]O₂) at peak exercise, and the slope of minute ventilation ([Formula: see text]E) versus carbon dioxide ([Formula: see text]CO₂) ([Formula: see text]E vs. [Formula: see text]CO₂ slope) were measured. CP was calculated by multiplying the peak [Formula: see text]O₂ and SBP values, and VP was calculated by dividing the peak SBP value by the [Formula: see text]E versus [Formula: see text]CO₂ slope. For males and females, the average CP values were 6119 ± 1280 (mean ± standard deviation) and 4775 ± 914 mmHg·mL/min/kg, respectively (p < 0.001). The average VP values for males and females were 8.0 ± 1.3 and 6.9 ± 1.3 mmHg (p < 0.001). CP decreased with age in both sexes. VP increased with age in females, with no significant change in males. We calculated the normal values for CP and VP in a healthy Japanese population. The results can contribute to the evaluation of patients' CPX results as a reference.

Prognostic value of peak stress cardiac power in patients with normal ejection fraction undergoing exercise stress echocardiography

AIMS

Cardiac power is a measure of cardiac performance that incorporates both pressure and flow components. Prior studies have shown that cardiac power predicts outcomes in patients with reduced left ventricular (LV) ejection fraction (EF). We sought to evaluate the prognostic significance of peak exercise cardiac power and power reserve in patients with normal EF.

METHODS AND RESULTS

We performed a retrospective analysis in 24 885 patients (age 59 ± 13 years, 45% females) with EF ≥50% and no significant valve disease or right ventricular dysfunction, undergoing exercise stress echocardiography between 2004 and 2018. Cardiac power and power reserve (developed power with stress) were normalized to LV mass and expressed in W/100 g of LV myocardium. Endpoints at follow-up were all-cause mortality and diagnosis of heart failure (HF). Patients in the higher quartiles of power/mass (rest, peak stress, and power reserve) were younger and had higher peak blood pressure and heart rate, lower LV mass, and lower prevalence of comorbidities. During follow-up [median 3.9 (0.6-8.3) years], 929 patients died. After adjusting for age, sex, metabolic equivalents (METs) achieved, ischaemia/infarction on stress test results, medication, and comorbidities, peak stress power/mass was independently associated with mortality [adjusted hazard ratio (HR), highest vs. lowest quartile, 0.5, 95% confidence interval (CI) 0.4-0.6, P < 0.001] and HF at follow-up [adjusted HR, highest vs. lowest quartile, 0.4, 95% CI (0.3, 0.5), P < 0.001]. Power reserve showed similar results.

CONCLUSION

The assessment of cardiac power during exercise stress echocardiography in patients with normal EF provides valuable prognostic information, in addition to stress test findings on inducible myocardial ischaemia and exercise capacity.

NT-proBNP is a weak indicator of cardiac function and haemodynamic response to exercise in chronic heart failure

AIMS

N-terminal prohormone of brain natriuretic peptide (NT-proBNP) plays an important role in diagnosis and management of heart failure. The aim of the present study was to assess haemodynamic response to exercise and to evaluate the relationship between NT-proBNP, cardiac function, and exercise tolerance in chronic heart failure.

METHODS AND RESULTS

A single-centre, cross-sectional pilot study recruited 17 patients with chronic heart failure with reduced left ventricular ejection fraction (age 67 ± 7 years) and 20 healthy volunteers (age 65 ± 12 years). The NT-proBNP was measured in the heart failure group. All participants completed maximal graded cardiopulmonary exercise stress testing coupled with gas exchange (using metabolic analyser for determination of exercise tolerance, i.e. peak O₂ consumption) and continuous haemodynamic measurements (i.e. cardiac output and cardiac power output) using non-invasive bioreactance technology. Heart failure patients demonstrated significantly lower peak exercise cardiac function and exercise tolerance than healthy controls, i.e. cardiac power output (5.0 ± 2.0 vs. 3.2 ± 1.2 W, P < 0.01), cardiac output (18.2 ± 6.3 vs. 13.5 ± 4.0 L/min, P < 0.01), heart rate (148 ± 23.7 vs. 111 ± 20.9 beats/min, P < 0.01), and oxygen consumption (24.3 ± 9.5 vs. 16.8 ± 3.8 mL/kg/min, P < 0.01). There was no significant relationship between NT-proBNP and cardiac function at rest, i.e. cardiac power output (r = -0.28, P = 0.28), cardiac output (r = -0.18, P = 0.50), and oxygen consumption (r = -0.18, P = 0.50), or peak exercise, i.e. cardiac power output (r = 0.18, P = 0.49), cardiac output (r = 0.13, P = 0.63), and oxygen consumption (r = -0.05, P = 0.84).

CONCLUSIONS

Lack of a significant and strong relationship between the NT-proBNP and measures of cardiac function and exercise tolerance may suggest that natriuretic peptides should be considered with caution in interpretation of the severity of cardiac dysfunction and functional capacity in chronic heart failure.

Post cardiac surgery stunning reduces stroke work, but leaves cardiac power output unchanged in patients with normal ejection fraction

This study assesses positional changes in cardiac power output and stroke work compared with classic hemodynamic variables, measured before and after elective coronary artery bypass graft surgery. The hypothesis was that cardiac power output was altered in relation to cardiac stunning. The study is a retrospective analysis of data from two previous studies performed in a tertiary care university hospital. Thirty-six patients scheduled for elective coronary artery bypass graft surgery, with relatively preserved left ventricular function, were included. A pulmonary artery catheter and a radial artery catheter were placed preoperatively. Cardiac power output and stroke work were calculated through thermodilution both supine and standing prior to induction of anesthesia and again day one postoperatively. Virtually all systemic hemodynamic parameters changed significantly from pre- to postoperatively, and from supine to standing. Cardiac power output was maintained at 0.9-1.0 (±0.3) W both pre- and postoperatively and from supine to standing on both days. Stroke work fell from pre- to postoperatively from 1.1 to 0.8 J (P < 0.001), there was a significant fall in stroke work with positional change preoperatively from 1.1 to 0.9 J (P < 0.001). Postoperatively the stroke work remained at 0.8 J despite positional change. Cardiac power output was the only systemic hemodynamic variable which remained unaltered during all changes. Stroke work appears to be a more sensitive marker for temporary cardiovascular dysfunction than cardiac power output. Further studies should explore the relationship between stroke work and cardiac performance and whether cardiac power output is an autoregulated intrinsic physiological parameter.

Minimally invasive beat-by-beat monitoring of cardiac power in normal hearts and during acute ventricular dysfunction

Cardiac power, the product of aortic flow and blood pressure, appears to be a fundamental cardiovascular parameter. The simplified version named cardiac power output (CPO), calculated as the product of cardiac output (CO) in L/min and mean arterial pressure (MAP) in mmHg divided by 451, has shown great ability to predict outcome in a broad spectrum of cardiac disease. Beat‐by‐beat evaluation of cardiac power (PWR) therefore appears to be a possibly valuable addition when monitoring circulatory unstable patients, providing parameters of overall cardiovascular function. We have developed a minimally invasive system for cardiac power measurement, and aimed in this study to compare this system to an invasive method (ttPWR). Seven male anesthetized farm pigs were included. A laptop with in‐house software gathered audio from Doppler signals of aortic flow and blood pressure from the patient monitor to continuously calculate and display a minimally invasive cardiac power trace (uPWR). The time integral per cardiac cycle (uPWR‐integral) represents cardiac work, and was compared to the invasive counterpart (ttPWR‐integral). Signals were obtained at baseline, during mechanically manipulated preload and afterload, before and after induced global ischemic left ventricular dysfunction. We found that the uPWR‐integral overestimated compared to the ttPWR‐integral by about 10% (P < 0.001) in both normal hearts and during ventricular dysfunction. Bland–Altman limits of agreement were at +0.060 and −0.054 J, without increasing spread over the range. In conclusion we find that the minimally invasive system follows its invasive counterpart, and is ready for clinical research of cardiac power parameters.

Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers

Background

Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure. We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure ventilation (NPPV).

Methods

Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, −20, −40, −60 and −80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with LBNP-levels.

Results

Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous breathing increasing 103 % (p < 0.001) from baseline to LBNP −80 mmHg. Respiratory variation in pulse pressure was the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP −80 mmHg. The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to LBNP −80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV.

Conclusions

Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly better than equivalent flow parameters, and far better than equivalent pressure parameters.

A meta-analysis of in vivo vertebrate cardiac performance: implications for cardiovascular support in the evolution of endothermy

Endothermy in birds and mammals is associated with high body temperatures, and high rates of metabolism that are aerobically supported by elevated rates of cardiovascular O2 transport. The purpose of this meta-analysis was to examine cardiovascular data from ectothermic and endothermic vertebrates, at rest and during exercise, with the goal of identifying key variables that may have contributed to the role of the cardiovascular system in supporting high rates of O2 transport associated with endothermy. Vascular conductance, cardiac power and stroke work were summarized and calculated from a variety of studies at rest and during exercise for five classes of vertebrates where data were available. Conductance and cardiac power were linearly related to cardiac output from rest to exercise and also interspecifically. Exercise cardiac power and stroke work were greater in the endothermic species, owing to increased flow resulting from increased heart rate and increased pressure. Increased relative ventricle mass (RVM) was related to increased stroke volume in both groups. However, the increased RVM of endotherms was related to the increased pressure, as stroke work per gram of ventricle during exercise was equivalent between the groups. Cardiac power was linearly related to aerobic metabolic power, with 158 mW aerobic power output achieved per mW of cardiac power input. This analysis indicates that the greatly increased heart rate and cardiac stroke work leading to increased blood flow rate and blood pressure was necessary to support the metabolic requirements of endothermy.