Comparison of electrical velocimetry and transpulmonary thermodilution for measuring cardiac output in piglets

EARLY FLUID PLUS NOREPINEPHRINE RESUSCITATION DIMINISHES KIDNEY HYPOPERFUSION AND INFLAMMATION IN SEPTIC NEWBORN PIGS

ABSTRACT

Sepsis is the most frequent risk factor for acute kidney injury (AKI) in critically ill infants. Sepsis-induced dysregulation of kidney microcirculation in newborns is unresolved. The objective of this study was to use the translational swine model to evaluate changes in kidney function during the early phase of sepsis in newborns and the impact of fluid plus norepinephrine resuscitation. Newborn pigs (3-7-day-old) were allocated randomly to three groups: 1) sham, 2) sepsis (cecal ligation and puncture) without subsequent resuscitation, and 3) sepsis with lactated Ringer plus norepinephrine resuscitation. All animals underwent standard anesthesia and mechanical ventilation. Cardiac output and glomerular filtration rate were measured noninvasively. Mean arterial pressure, total renal blood flow, cortical perfusion, medullary perfusion, and medullary tissue oxygen tension (mtPO 2 ) were determined for 12 h. Cecal ligation and puncture decreased mean arterial pressure and cardiac output by more than 50%, with a proportional increase in renal vascular resistance and a 60-80% reduction in renal blood flow, cortical perfusion, medullary perfusion, and mtPO 2 compared to sham. Cecal ligation and puncture also decreased glomerular filtration rate by ~79% and increased AKI biomarkers. Isolated foci of tubular necrosis were observed in the septic piglets. Except for mtPO 2 , changes in all these parameters were ameliorated in resuscitated piglets. Resuscitation also attenuated sepsis-induced increases in the levels of plasma C-reactive protein, proinflammatory cytokines, lactate dehydrogenase, alanine transaminase, aspartate aminotransferase, and renal NLRP3 inflammasome. These data suggest that newborn pigs subjected to cecal ligation and puncture develop hypodynamic septic AKI. Early implementation of resuscitation lessens the degree of inflammation, AKI, and liver injury.

Performance of four cardiac output monitoring techniques vs. intermittent pulmonary artery thermodilution during a modified passive leg raise maneuver in isoflurane-anesthetized dogs

Objective

This study investigated the performance among four cardiac output (CO) monitoring techniques in comparison with the reference method intermittent pulmonary artery thermodilution (iPATD) and their ability to diagnose fluid responsiveness (FR) during a modified passive leg raise (PLRM) maneuver in isoflurane-anesthetized dogs undergoing acute blood volume manipulations. The study also examined the simultaneous effect of performing the PLRM on dynamic variables such as stroke distance variation (SDV), peak velocity variation (PVV), and stroke volume variation (SVV).

Study design

Prospective, nonrandomized, crossover design.

Study animals

Six healthy male Beagle dogs.

Methods

The dogs were anesthetized with propofol and isoflurane and mechanically ventilated under neuromuscular blockade. After instrumentation, they underwent a series of sequential, nonrandomized steps: Step 1: baseline data collection; Step 2: removal of 33 mL kg-1 of circulating blood volume; Step 3: blood re-transfusion; and Step 4: infusion of 20 mL kg-1 colloid solution. Following a 10-min stabilization period after each step, CO measurements were recorded using esophageal Doppler (EDCO), transesophageal echocardiography (TEECO), arterial pressure waveform analysis (APWACO), and electrical cardiometry (ECCO). Additionally, SDV, PVV, and SVV were recorded. Intermittent pulmonary artery thermodilution (iPATDCO) measurements were also recorded before, during, and after the PLRM maneuver. A successful FR diagnosis made using a specific test indicated that CO increased by more than 15% during the PLRM maneuver. Statistical analysis was performed using one-way analysis of variance for repeated measures with post hoc Tukey test, linear regression, Lin's concordance correlation coefficient (ρc), and Bland-Altman analysis. Statistical significance was set at p < 0.05.

Results

All techniques detected a reduction in CO (p < 0.001) during hemorrhage and an increase in CO after blood re-transfusion and colloid infusion (p < 0.001) compared with baseline. During hemorrhage, CO increases with the PLRM maneuver were as follows: 33% for iPATD (p < 0.001), 19% for EC (p = 0.03), 7% for APWA (p = 0.97), 39% for TEE (p < 0.001), and 17% for ED (p = 0.02). Concurrently, decreases in SVV, SDV, and PVV values (p < 0.001) were also observed. The percentage error for TEE, ED, and EC was less than 30% but exceeded 55% for APWA. While TEECO and ECCO slightly underestimated iPATDCO values, EDCO and APWACO significantly overestimated iPATDCO values. TEE and EC exhibited good and acceptable agreement with iPATD. However, CO measurements using all four techniques and iPATD did not differ before, during, and after PLRM at baseline, blood re-transfusion, and colloid infusion.

Conclusion and clinical relevance

iPATD, EC, TEE, and ED effectively assessed FR in hypovolemic dogs during the PLRM maneuver, while the performance of APWA was unacceptable and not recommended. SVV, SDV, and PVV could be used to monitor CO changes during PLRM and acute blood volume manipulations, suggesting their potential clinical utility.

Comparison of heart rate and cardiac output of VVI pacemaker settings in patients with atrial fibrillation with bradycardia

BACKGROUND

While most VVI pacemakers in bradycardic patients are set to a low limit of 60/min, the optimal lower limit rate for VVI pacemakers in atrial fibrillation has not been established. Although an increase in heart rate within the normal range in the setting of a VVI pacemaker might be expected to lead to an increase in cardiac output with the shortening of the diastolic time, the changes in cardiac output at different pacemaker settings have not been fully clarified.

METHODS

We included 11 patients with bradycardic atrial fibrillation who had VVI pacemakers implanted. Stroke volume was measured using the electrical cardiometry method (AESCULONⓇ mini; Osypka Medical) without pacing and at ventricular pacings of 60, 70, 80, and 90/min.

RESULTS

Stroke volume decreased stepwise at ventricular pacing rates of 60, 70, 80, and 90/min (63.6 ± 11.2, 61.9 ± 10.6, 59.3 ± 12.2, and 57.5 ± 12.2 mL, p < .001), but cardiac output increased (3.81 ± 0.67, 4.33 ± 0.74, 4.74 ± 0.97, and 5.17 ± 1.09 L/min, p < .001). The rate of increase in cardiac output at a pacing rate of 70/min compared to 60/min correlated with left ventricular end-systolic volume (r = 0.711, p = .014).

CONCLUSIONS

Cardiac output increased at a pacing rate of 70 compared to 60 in bradycardic atrial fibrillation patients, and the rate of increase in cardiac output was greater in those with larger left ventricular end-systolic volume.

Evaluation of Electrical Cardiometry for Measuring Cardiac Output and Derived Hemodynamic Variables in Comparison with Lithium Dilution in Anesthetized Dogs

Numerous cardiac output (CO) technologies were developed to replace the 'gold standard' pulmonary artery thermodilution due to its invasiveness and the risks associated with it. Minimally invasive lithium dilution (LiD) shows excellent agreement with thermodilution and can be used as a reference standard in animals. This study evaluated CO via noninvasive electrical cardiometry (EC) and acquired hemodynamic variables against CO measured using LiD in six healthy, anesthetized dogs administered different treatments (dobutamine, esmolol, phenylephrine, and high-dose isoflurane) impacting CO values. These treatments were chosen to cause drastic variations in CO, so that fair comparisons between EC and LiD across a wide range of CO values (low, intermediate, and high) could be made. Statistical analysis included linear regression, Bland-Altman plots, Lin's concordance correlation coefficient (ρ_c), and polar plots. Values of p < 0.05 represented significance. Good agreement was observed between EC and LiD, but consistent underestimation was noted when the CO values were high. The good trending ability, ρ_c of 0.88, and low percentage error of ±31% signified EC's favorable performance. Other EC-acquired variables successfully tracked changes in CO measured using LiD. EC may be a pivotal hemodynamic tool for continuously monitoring circulatory changes, as well as guiding and treating cardiovascular anesthetic complications in clinical settings.

Agreement between Electrical Cardiometry and Pulmonary Artery Thermodilution for Measuring Cardiac Output in Isoflurane-Anesthetized Dogs

In animals, invasive pulmonary artery thermodilution (PATD) is a gold standard for cardiac output (CO) monitoring, but it is impractical in clinical settings. This study evaluates the agreement between PATD and noninvasive electrical cardiometry (EC) for measuring CO and analyzes the other EC-derived hemodynamic variables in six healthy anesthetized dogs subjected to four different hemodynamic events in a sequential order: (1) euvolemia (baseline); (2) hemorrhage (33% blood volume loss); (3) autologous blood transfusion; and (4) 20 mL/kg colloid bolus. The CO measurements obtained using PATD and EC are compared using Bland-Altman analysis, Lin's concordance correlation (LCC), and polar plot analysis. Values of p < 0.05 are considered significant. The EC measurements consistently underpredict the CO values as compared with PATD, and the LCC is 0.65. The EC's performance is better during hemorrhage, thus indicating its capability in detecting absolute hypovolemia in clinical settings. Even though the percentage error exhibited by EC is 49.4%, which is higher than the standard (<30%), EC displays a good trending ability. Additionally, the EC-derived variables display a significant correlation with the CO measured using PATD. Noninvasive EC may have a potential in monitoring trends in hemodynamics in clinical settings.

Systemic and regional cerebral perfusion in small infants undergoing minor lower abdominal surgery under awake caudal anaesthesia: An observational study

BACKGROUND

Infants undergoing general anaesthesia have an increased risk of severe respiratory and cardiovascular critical events. Awake caudal anaesthesia is an alternative for small infants undergoing minor lower abdominal surgery. While clinical experience has shown stable intra-operative haemodynamic conditions, there are no studies evaluating systemic and regional cerebral perfusion during such a procedure.

OBJECTIVES

The purpose of this study was to evaluate the effects of awake caudal anaesthesia on systemic and regional cerebral perfusion in small infants.

DESIGN

A prospective observational cohort study.

SETTING

Clinic of Anaesthesiology, University Children's Hospital, between November 2017 and June 2018.

PATIENTS

Twenty small infants (postmenstrual age 36 to 54 weeks, weight 1800 to 5700 g) scheduled for lower abdominal surgery under awake caudal anaesthesia were enrolled in this study.

INTERVENTION

Standard monitoring was expanded to include cardiac index using electrical velocimetry and regional cerebral oxygen saturation using near infrared spectroscopy. The caudal block was performed with 0.3% ropivacaine 1 ml kg Hypotension was defined as mean arterial blood pressure (BP) less than 35 mmHg and regional cerebral desaturation as regional cerebral oxygen saturation less than 80% of baseline.

MAIN OUTCOMES

Mean arterial BP, cardiac index and regional cerebral oxygen saturation parameters under awake caudal anaesthesia.

RESULTS

Mean arterial BP, cardiac index and regional cerebral oxygen saturation remained above the predefined lower limits. No episodes of hypotension or regional cerebral desaturation were observed. Operation time was 35 ± 13 (range 20 to 71) min. The infants were discharged to the neonatal ward after the end of surgery, and milk was fed 22 ± 15 (range 6 to 55) min thereafter. Five preterm infants experienced self-limiting episodes of apnoea intra-operatively.

CONCLUSION

The current study shows that awake caudal anaesthesia does not impair systemic and regional cerebral perfusion in small infants.

TRIAL REGISTRATION

German registry of clinical studies (DRKS-ID: 800015742).

Bioimpedance analysis as a tool for hemodynamic monitoring: overview, methods and challenges

Recent advances in hemodynamic monitoring have seen the advent of non-invasive methods which offer ease of application and improve patient comfort. Bioimpedance Analysis or BIA is one of the currently employed non-invasive techniques for hemodynamic monitoring. Impedance Cardiography (ICG), one of the implementations of BIA, is widely used as a non-invasive procedure for estimating hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Even though BIA is not a new diagnostic technique, it has failed to gain consensus as a reliable measure of hemodynamic parameters. Several devices have emerged for estimating CO using ICG which are based on evolving methodologies and techniques to calculate SV. However, the calculations are generally dependent on the electrode configurations (whole body, segmental or localised) as well as the accuracy of different techniques in tracking blood flow changes. Blood volume changes, concentration of red blood cells, pulsatile velocity profile and ambient temperature contribute to the overall conductivity of blood and hence its impedance response during flow. There is a growing interest in investigating limbs for localised BIA to estimate hemodynamic parameters such as pulse wave velocity. As such, this paper summarises the current state of hemodynamic monitoring through BIA in terms of different configurations and devices in the market. The conductivity of blood flow has been emphasized with contributions from both volume and velocity changes during flow. Recommendations for using BIA in hemodynamic monitoring have been mentioned highlighting the suitable range of frequencies (1 kHz-1 MHz) as well as safety considerations for a BIA setup. Finally, current challenges in using BIA such as geometry assumption and inaccuracies have been discussed while mentioning potential advantages of a multi-frequency analysis to cover all the major contributors to blood's impedance response during flow.

Non-invasive evaluation of macro- and microhemodynamic changes during induction of general anesthesia – A prospective observational single-blinded trial

BACKGROUND: Hypotension and bradycardia are known side effects of general anesthesia, while little is known about further macro- and microhemodynamic changes during induction. Intriguing is furthermore, why some patients require no vasopressor medication to uphold mean arterial pressure, while others need vasopressor support. OBJECTIVE: Determination of macro- and microhemodynamic changes during induction of general anesthesia. METHODS: We enrolled 150 female adults scheduled for gynaecological surgery into this prospective observational, single-blinded trial. Besides routinely measuring heart rate (HR) and mean arterial blood pressure (MAP), the non-invasive technique of thoracic electrical bioimpedance was applied to measure cardiac output (CO), cardiac index (CI), stroke volume (SV), stroke volume variability (SVV) and index of myocardial contractility (ICON) before induction of anesthesia, 7 times during induction, and, finally, after surgery in the recovery room. Changes in microcirculation were assessed using sidestream dark field imaging to establish the perfused boundary region (PBR), a validated gauge of glycocalyx health. Comparisons were made with Friedman’s or Wilcoxon test for paired data, and with Mann-Whitney-U test for unpaired data, with post-hoc corrections for multiple measurements by the Holm-Bonferroni method. RESULTS: 83 patients did not need vasopressor support, whereas 67 patients required therapy (norepinephrine, atropine or cafedrine/theodrenaline) to elevate MAP values to ≥70mmHg during induction, 54 of these receiving norepinephrine (NE) alone. Pre-interventional (basal) values of CO, CI, ICON, SV and SVV were all significantly lower in the group of patients later requiring NE (p < 0.04), whereas HR and MAP were identical for both groups. HR, MAP and CO decreased from baseline to 12 min after induction of general anesthesia in both the patients without and those with NE support. Heart rate decreased significantly by about 25% in both groups (–19 to –21 bpm). The median individual decrease of MAP amounted to –26.7% (19.7/33.3, p < 0.001) and –26.1% (11.6/33.2, p < 0.001), respectively, whereas for CO it was –40.7% (34.1/50.1, p < 0.001) and –43.5% (34.8/48.7). While these relative changes did not differ between the two groups, in absolute values there were significantly greater decreases in CO, CI, SV and ICON in the group requiring NE. Noteably, NE did not restore ICON or the other cardiac parameters to levels approaching those of the group without NE. PBR was measured in a total of 84 patients compiled from both groups, there being no intergroup differences. It increased 6.4% (p < 0.001) from pre-induction to the end of the operation, indicative of damage to microvascular glycocalyx. CONCLUSION: Non-invasive determination of CO provides additional hemodynamic information during anesthesia, showing that induction results in a significant decrease not only of MAP but also of CO and other cardiac factors at all timepoints compared to baseline values. The decrease of CO was greater than that of MAP and, in contrast to MAP, did not respond to NE. There was also no sign of a positive inotropic effect of NE in this situation. Support of MAP by NE must consequently result from an increase in peripheral arterial resistance, posing a risk for oxygen supply to tissue. In addition, general anesthesia and the operative stimulus lead to an impairment of the microcirculation.

Objective Assessment of Physiologic Alterations Associated With Hemodynamically Significant Patent Ductus Arteriosus in Extremely Premature Neonates

Delay in closure of ductus arteriosus in postnatal life may lead to serious consequences and complications in an extremely premature neonate secondary to hemodynamic alterations in regional blood flow pattern in various organs. Despite the widespread recognition amongst neonatologists to identify a hemodynamically significant patent ductus arteriosus (hsPDA) early in the postnatal course, there is lack of consensus in its definition and thus the threshold to initiate treatment. Echocardiographic assessment of PDA shunt size and volume combined with neonatologists' impression of clinical significance is most frequently used to determine the need for treatment of PDA. Common clinical signs of hsPDA utilized as surrogate for decreased tissue perfusion may lag behind early echocardiographic signs. Although echocardiogram allows direct assessment of PDA shunt and hemodynamic alterations in the heart, it is limited by dependence on pediatric cardiologist availability, interobserver variation and isolated time point assessment. Electrical cardiometry (EC) is a non-invasive continuous real time measurement of cardiac output by applying changes in thoracic electrical impedance. EC has been validated in preterm newborns by concomitant transthoracic echocardiogram assessments and may be beneficial in studying changes in cardiac output in premature newborns with hsPDA. Alterations in perfusion index derived from continuous pulse oximetry monitoring has been used to study changes in cardiac performance and tissue perfusion in infants with PDA. Near infrared spectroscopy (NIRS) has been used to objectively and continuously assess variations in renal, mesenteric, and cerebral oxygen saturation and thus perfusion changes due to diastolic vascular steal from hsPDA in preterm neonates. Doppler ultrasound studies measuring resistive indices in cerebral circulation indicate disturbance in cerebral perfusion secondary to ductal steal. With recent trends of change in practice toward less intervention in care of preterm newborn, treatment strategy needs to be targeted for select preterm population most vulnerable to adverse hemodynamic effects of PDA. Integration of these novel ways of hemodynamic and tissue perfusion assessment in routine clinical care may help mitigate the challenges in defining and targeting treatment of hsPDA thereby improving outcomes in extremely premature neonates.

Can bioimpedance cardiography assess hemodynamic response to passive leg raising in critically ill patients: A STROBE-compliant study

Passive leg raising (PLR) is a convenient and reliable test to predict fluid responsiveness. The ability of thoracic electrical bioimpedance cardiography (TEB) to monitor changes of cardiac output (CO) during PLR is unknown.In the present study, we measured CO in 61 patients with shock or dyspnea by TEB and transthoracic echocardiography (TTE) during PLR procedure. Positive PLR responsiveness was defined as the velocity-time integral (VTI) ≥10% after PLR. TTE measured VTI in the left ventricular output tract. The predictive value of TEB parameters in PLR responders was tested. Furthermore, the agreement of absolute CO values between TEB and TTE measurements was assessed.Among the 61 patients, there were 28 PLR-responders and 33 non-responders. Twenty-seven patients were diagnosed with shock and 34 patients with dyspnea, with 55.6% (15/27) and 54.6% (18/34) non-responders, respectively. A change in TEB measured CO (ΔCO) ≥9.8% predicted PLR responders with 75.0% sensitivity and 78.8% specificity, the area under the receiver operating characteristic curve (AUROC) was 0.79. The Δd2Z/dt2 (a secondary derivative of the impedance wave) showed the best predictive value with AUROC of 0.90, the optimal cut point was -7.1% with 85.7% sensitivity and 87.9% specificity. Bias between TEB and TTE measured CO was 0.12 L/min, and the percentage error was 65.8%.TEB parameters had promising performance in predicting PLR responders, and the Δd2Z/dt2 had the best predictive value. The CO values measured by TEB were not interchangeable with TTE in critically ill settings.

Effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease: A prospective observational study

BACKGROUND

Neonates and infants with congenital heart disease undergoing general anesthesia have an increased risk for critical cardiovascular events. Etomidate produces very minimal changes in hemodynamic parameters in older children with congenital heart disease. There is a lack of studies evaluating the effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease.

AIM

The aim of this prospective observational study was to evaluate the effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease.

METHODS

In fifty infants aged 0-11 months (24% neonates n = 12) with congenital heart disease, mean arterial blood pressure, cardiac index using electrical cardiometry, and regional cerebral oxygen saturation using near-infrared spectroscopy were measured at baseline and 1, 3, 5, and 10 minutes after induction by 0.4 mg kg^-1 etomidate. Hypotension was defined as a mean arterial blood pressure under 35 mm Hg and cerebral desaturation as a regional cerebral oxygen saturation of less than 80% of baseline.

RESULTS

Mean arterial blood pressure, cardiac index, and regional cerebral oxygen saturation remained stable above the predefined limits. Mean arterial blood pressure decreased slightly within a physiological range after 3 minutes (P = .005, 95% CI:-5.9 to -1.0). No significant change in cardiac index could be observed.

CONCLUSION

Etomidate 0.4mg kg^-1 does not impair systemic or regional cerebral perfusion in neonates or infants with congenital heart disease.

Appropriate delivery method for cardiac disease pregnancy based on noninvasive cardiac monitoring

Background There are numerous significant physiological changes occurring in circulation during labor. To detect these rapid hemodynamic changes, invasive and intermittent measurement techniques are not reliable. To suggest a suitable delivery method for pregnancy with cardiac disease, this study analyzed how each delivery method influences cardiac function using a noninvasive and continuous measurement technique. Methods A prospective study was accomplished at the National Cerebral and Cardiovascular Center in Japan from October 1, 2014, to November 30, 2018. The classification of the healthy heart pregnant women was according to the delivery method: vaginal delivery (VD) without epidural anesthesia, VD with epidural anesthesia, and caesarean section (CS). The hemodynamic parameters cardiac index (CI), stroke volume index (SI), and heart rate (HR) were evaluated regularly throughout delivery by noninvasive electrical cardiometry monitor. Results Ten cases were examined for each group. CI and HR were significantly increased before VD, while the increase in CI and HR was mild in the epidural group in comparison to the nonepidural group. SI was increased toward the delivery in the epidural group, and it was constant in the nonepidural group. However, there was no alteration in the level of outcomes of the two groups. In CS, SI increased and HR decreased before delivery. After delivery, SI continued to increase, while HR did not change but CI increased. Conclusion In VD, the increase in venous circulation according to the autotransfusion is managed by increasing HR. By epidural anesthesia, the increase in HR was suppressed and SI was increased. However, as epidural anesthesia increases the vascular capacity, the level of SI outcome was comparable. In CS, the HR was decreased because of the spinal anesthesia and the SI was increased because of many factors like hydration. As there are many factors to control in CS, VD with epidural anesthesia will be the first preference for most cardiac patients.

Effect of hemodialysis on impedance cardiography (electrical velocimetry) parameters in children

BACKGROUND

Pediatric hemodialysis (HD) patients have a high incidence of cardiovascular morbidity and mortality. The study aim was to investigate whether impedance cardiography (electrical velocimetry, EV) is suitable as a hemodynamic trend monitoring tool in pediatric patients during HD.

METHODS

Measurements by EV were obtained before, during, and after HD in a prospective single-center pediatric observational study. In total, 54 dialysis cycles in four different pediatric patients with end-stage kidney disease on chronic HD were included. EV parameters analyzed were heart rate (HR), stroke volume (SV), stroke volume index (SI), cardiac output (CO), cardiac index (CI), thoracic fluid content (TFC), index of contractility (ICON), stroke volume variation (SVV), variation of ICON (VIC), R-R interval (TRR), pre-ejection period (PEP), left ventricular ejection time (LVET), and systolic time ration (STR). Systemic vascular resistance index (SVRI) was calculated.

RESULTS

EV did measure significant changes in cardiovascular parameters associated with HD. The following parameters increased after HD: HR (9%), SVV (19%), VIC (33%), PEP (8%), and STR (18%). A decrease after HD was measured in SV (18%), SI (18%), CO (10%), CI (10%), TFC (10%), ICON (7%), TRR (7%), LVET (8%), and LVET (8%). SVRI was not affected by HD. The changes were correlated to ultrafiltration. HD cycles without fluid withdrawal also altered cardiovascular parameters.

CONCLUSIONS

Pediatric HD with and without fluid withdrawal changes hemodynamic EV monitoring parameters. Possibly EV may be useful to optimize HD management in pediatric patients.

Feasibility, reproducibility and accuracy of electrical velocimetry for cardiac output assessment in congenital heart disease

BACKGROUND

Noninvasive cardiac output assessment is important for prognostication in patients with heart failure. Electrical velocimetry (EV), an impedance cardiography technique, can be used for noninvasive cardiac output assessment. The purpose of this study was to determine the feasibility, reproducibility and accuracy of cardiac output assessment by EV in adults with congenital heart disease (CHD).

METHODS

Cross-sectional study of CHD patients that had simultaneous cardiac output assessment by Fick and EV (using Cardiotronic monitor, Osypka Medical). We divided the cohort into: Group 1 patients (n = 54) had hemodynamic assessment at rest only, while Group 2 patients (n = 7) had assessment both at rest and peak exercise.

RESULTS

EV cardiac output assessment was feasible in 100% of the patients. There was good correlation between Fick-derived and EV-derived cardiac index (r = 0.89, p < 0.001) in Group 1. Among 26 patients in Group 1 that underwent cardiac output assessment pre- and post-intervention, there was no difference in the strength of correlation of Fick and EV cardiac output pre- and post-intervention (p-interaction 0.244) indicating good reproducibility of the technique. There was also modest correlation between Fick-derived and EV-derived cardiac index at rest (r = 0.68, p = 0.032), and peak exercise (r = 0.62, p = 0.055), in Group 2.

CONCLUSION

In this study, we demonstrated the feasibility and accuracy of EV cardiac output assessment in adults with CHD. We also demonstrated, for the first time, that EV cardiac output assessment was reproducible under different loading conditions, and that EV can be used for the assessment of cardiac output augmentation at peak exercise.

Changes in cardiac output and cerebral oxygenation during prone and supine sleep positioning in healthy term infants

OBJECTIVE

To investigate the changes in systemic and cerebral haemodynamics between supine and prone sleep in healthy term infants during the early postnatal period.

DESIGN/METHODS

Healthy term infants without congenital anomalies, patent ductus arteriosus and/or small for gestational age status were enrolled. Infants were placed in supine (SP₁), prone (PP) and back in supine (SP₂) position for 15 min each while asleep. Cardiac output (CO) and stroke volume (SV) were assessed by electrical velocimetry (EV) and echocardiography (echo), and cerebral regional oxygen saturation (CrSO₂) in the frontal lobes was monitored by near-infrared spectroscopy. Heart rate (HR) and SpO₂ were continuously monitored by conventional monitoring.

RESULTS

In 34 healthy term infants (mean age 3.7±1.2 days; 16 females), 66 sets of serial CO measurements (34 EV and 32 echo) in three sleep positions were obtained. Mean CO_EV and CO_echo were 182±57 (SP₁), 170±50 (PP) and 177±54 (SP₂), and 193±48 (SP₁), 174±40 (PP) and 192±50 (SP₂) mL/kg/min, respectively. Mean SV_EV and SV_echo were 1.46±0.47 (SP₁), 1.36±0.38 (PP) and 1.37±0.39 (SP₂), and 1.54±40 (SP₁), 1.38±0.38 (PP) and 1.51±0.41 (SP₂) mL/kg, respectively. Repeated measures analysis of variance revealed a decrease in CO and SV during prone positions by both EV and echo, while HR, SpO₂ and CrSO₂ did not change. Thirty-eight per cent of the CO measurements decreased≥10% during prone positioning.

CONCLUSIONS

In healthy term infants, CO decreases in prone position due to a decrease in SV and not HR. CO recovers when placed back in supine. However, frontal lobe CrSO₂ does not change in the different positions.

Comparison of bioreactance non-invasive cardiac output measurements with cardiac magnetic resonance imaging

Impedance cardiography measurement of cardiac output gained wide interest due to its ease of use and non-invasiveness. However, validation studies of different algorithms yielded diverging results. Bioreactance (BR) as a recent adaption differs fundamentally as the flow signal is derived from phase shifts. Our aim was to assess the accuracy and reproducibility of BR, as compared to the non-invasive gold standard--cardiac magnetic resonance imaging (CMR). We prospectively included 32 stable patients. BR was performed twice in the supine position and averaged over 30 seconds. Mean bias was 0.2 ± 1.8 l/minute (1 ± 28%, percentage error 55%) with limits of agreement ranging from  -3.4 to 3.7 l/minute. Reproducibility was acceptable with a mean bias of 0.1 ± 0.9 l/minute (1 ± 14%, 27%). Low cardiac output was significantly overestimated (-1.1 ± 1.5 l/minute), while high cardiac output was underestimated (1.5 ± 1.7 l/minute), (P=0.001), although reproducibility was unaffected. Bias and weight were moderately correlated in men (r = 0.50, P=0.02). No differences for accuracy were found in nine patients who had an arrhythmia (0.3 ± 1.4 versus 0.1 ± 2.0 l/minute, P=0.76), while clinically relevant differences were found in patients with mild aortic valve disease (1.9 ± 2.2 versus -0.3 ± 1.7 l/minute, P=0.02). Overall, BR showed insufficient agreement with CMR, overestimating low and underestimating high cardiac output states. Reproducibility was acceptable and not negatively affected by the circulatory condition. Consequently, absolute values acquired with BR should be interpreted with caution and must not be used interchangeably in clinical practice.

Changes in cardiac index during labour analgesia: A double-blind randomised controlled trial of epidural versus combined spinal epidural analgesia - A preliminary study

BACKGROUND AND AIMS

Combined spinal-epidural (CSE) analgesia for labour and delivery is occasionally associated with foetal bradycardia. Decreases in cardiac index (CI) and/or uterine hypertonia are implicated as possible aetiological factors. No study has evaluated CI changes following combined spinal analgesia for labour and delivery. This prospective, double-blind, randomised controlled trial evaluates haemodynamic trends during CSE and epidural analgesia for labour.

METHODS

Twenty-six parturients at term requesting labour analgesia were randomised to receive either epidural (E) or CSE analgesia. The Electrical Cardiometry Monitor ICON^® was used to continuously determine maternal CI non-invasively, heart rate (HR) and stroke volume at baseline and up to 60 min after initiation of either intrathecal or epidural analgesia. In addition, maternal systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded.

RESULTS

Both SBP and DBP had a similar, significant decrease following initiation of either epidural or CSE analgesia. However, parturients in the CSE group (n = 10) demonstrated a significant decrease in HR and CI compared to the baseline measurements. On the other hand, the parturients in the E (n = 13) group showed no decreases in either maternal HR or CI. Foetal heart changes were observed in four patients following CSE and one patient following an epidural.

CONCLUSION

Labour analgesia with CSE is associated with a significant decrease in HR and CI when compared to labour analgesia with epidural analgesia. Further studies are necessary to determine whether a decrease in CI diminishes placental blood flow.

Cardiac output decreases and systemic vascular resistance increases in newborns placed in the left-lateral position

OBJECTIVE

The objective of the study was to study the effect of short-term left-lateral position on cardiovascular parameters in hemodynamically stable newborns.

STUDY DESIGN

Cardiac output (CO), stroke volume (SV), systemic vascular resistance index (SVRI) and heart rate (HR) were measured by electric velocimetry in hemodynamically stable newborns without respiratory support in the supine, left-lateral and back-to-supine positions, each kept for 10 min.

RESULTS

Thirty-two newborns were enrolled, birth weight 2134 (1818 to 2460) g, gestational age 34.5±2.4 weeks. CO and SV decreased significantly from supine to left-lateral position (CO supine: 193.4 (168.0 to 229.6) ml kg^-1min^-1; CO left-lateral: 172.0 (154.9 to 201.6) ml kg^-1min^-1, P<0.0001; SV supine: 3.0 (2.7 to 4.0) ml; SV left-lateral: 2.7 (2.4 to 3.2) ml, P<0.0004). Conversely, SVRI increased in left-lateral position: SVRI supine: 18865±9244 dyns cm^-5 m^-2; SVRI left-lateral: 21203±10059 dyns cm^-5 m^-2, P<0.0001). All variables returned to the initial value when infants were back in the supine position. HR and blood pressure did not change.

CONCLUSION

In stable infants, CO and SV decrease and SVRI increases, in left-lateral position.

Electrical velocimetry for noninvasive cardiac output and stroke volume variation measurements in dogs undergoing cardiovascular surgery

OBJECTIVE

To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Seven adult Beagle dogs with a median weight of 13.6 kg.

METHODS

Simultaneous, coupled cardiac index (CI; CO indexed to body surface area) measurements by EV (CI_EV) and the reference pulmonary artery catheter thermodilution method (CI_PAC) were obtained in seven sevoflurane-anaesthetized, mechanically ventilated dogs undergoing experimental open-chest cardiovascular surgery for isolated right ventricular failure. Relationships between SVV or central venous pressure (CVP) and stroke volume (SV) were analysed to estimate fluid responsiveness. Haemodynamic data were recorded intraoperatively and before and after fluid challenge.

RESULTS

Bland-Altman analysis of 332 matched sets of CI data revealed an overall bias and precision of - 0.22 ± 0.52 L minute^-1 m^-2 for CI_EV and CI_PAC (percentage error: 30.4%). Trend analysis showed a concordance of 88% for CI_EV. SVV showed a significant positive correlation (r² = 0.442, p < 0.0001) with SV changes to a volume loading of 200 mL, but CVP did not (r² = 0.0002, p = 0.94). Better prediction of SV responsiveness (rise of SV index of ≥ 10%) was observed for SVV (0.74 ± 0.09; p = 0.014) with a significant area under the receiver operating characteristic curve in comparison with CVP (0.53 ± 0.98; p = 0.78), with a cut-off value of 14.5% (60% specificity and 83% sensitivity).

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs undergoing cardiovascular surgery, EV provided accurate CO measurements compared with CI_PAC, although its trending ability was poor. Further, SVV by EV, but not CVP, reliably predicted fluid responsiveness during mechanical ventilation in dogs.

Noninvasive stroke volume variation using electrical velocimetry for predicting fluid responsiveness in dogs undergoing cardiac surgery

OBJECTIVE

To evaluate the ability of a noninvasive cardiac output monitoring system with electrical velocimetry (EV) for predicting fluid responsiveness in dogs undergoing cardiac surgery.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

A total of 30 adult Beagle dogs.

METHODS

Stroke volume (SV), stroke volume variation (SVV) and cardiac index were measured using the EV device in sevoflurane-anaesthetized, mechanically ventilated dogs undergoing thoracotomies for experimental creation of right ventricular failure. The dogs were considered fluid responsive if stroke volume (SVI; indexed to body weight), measured using pulmonary artery thermodilution, increased by 10% or more after volume loading (10 mL kg^-1). Relationships of SVV, central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) with SVI were analysed to estimate fluid responsiveness.

RESULTS

Better prediction of fluid responsiveness, with a significant area under the receiver operating characteristic curve, was observed for SVV (0.85±0.07; p=0.0016) in comparison with CVP (0.65±0.11; p=0.17) or PAOP (0.60±0.12; p=0.35), with a cut-off value of 13.5% (84% specificity and 73% sensitivity).

CONCLUSIONS AND CLINICAL RELEVANCE

SVV derived from EV is useful for identification of dogs that are likely to respond to fluids, providing valuable information on volume status under cardiothoracic anaesthesia.

Reliable and developmentally appropriate study end points are needed to achieve drug development for treatment of pediatric pulmonary arterial hypertension

OBJECTIVE

To identify suitable end points and surrogates for pediatric pulmonary arterial hypertension (PAH) as the lack of developmentally appropriate end point and clinical trials contribute to the unmet medical need.

STUDY DESIGN

Reviewed the efficacy end points and surrogates for all trials (1995 to 2013) that were submitted to the Food and Drug Administration (FDA) to support the approval of PAH therapy and conducted literature search.

RESULTS

An increase in the 6 min walking distance (6MWD) was used as a primary end point in 8/9 adult PAH trials. This end point is not suitable for infants and young children because of performance limitations and lack of control data. One adult PAH trial used time to the first morbidity or mortality event as a primary end point, which could potentially be used in pediatric PAH trials. In the sildenafil pediatric PAH trial, the change in pulmonary vascular resistance index or mean pulmonary artery pressure was used as a surrogate for the 6MWD to assess exercise capacity. However, two deaths and three severe adverse events during the catheterizations made this an unacceptably high-risk surrogate. The INOmax persistent pulmonary hypertension of the newborn trial used a reduction in initiation of extracorporeal membrane oxygenation treatment as a primary end point, which is not feasible for other pediatric PAH trials. A Literature review revealed none of the existing noninvasive markers are fully validated as surrogates to assess PAH efficacy and long-term safety.

CONCLUSIONS

For pediatric PAH trials, clinical end points are acceptable, and novel validated surrogates would be helpful. FDA seeks collaboration with academia, industry and parents to develop other suitable and possibly more efficient efficacy end points to facilitate pediatric PAH drug development.

Stroke volume and cardiac output evaluation by electrical cardiometry: accuracy and reference nomograms in hemodynamically stable preterm neonates

OBJECTIVE

To investigate the accuracy of electrical cardiometry (EC) to measure stroke volume (SV) and cardiac output (CO) and to provide gestational age (GA) and birth weight (BW)-based reference data for SV and CO in hemodynamically stable preterm neonates.

STUDY DESIGN

Prospective observational blinded study. Paired measurements of SV and CO on stable preterm infants without any hemodynamic compromise were carried out using EC (SVEC) and echocardiography (SVECHO).

RESULTS

Seventy-nine preterm neonates (mean GA: 31±3.2 weeks) were enrolled. A good correlation was found for SV (r=0.743; P<0.0001) and CO (r=0.7; P<0.0001) measured by EC and echocardiography. These correlations remained significant after adjusting for GA, patent ductus arteriosus and type of respiratory support (SV: St.β=0.48, P<0.0001 and CO: St.β=0.69, P<0.0001). Mean biases (and variabilities) were -1.1 (from 0.7 to -2.9) ml and -0.21 (from 0.15 to -0.55) l min(-1) for SV and CO, respectively. Local regression shows a tendency for EC to overestimate SV and CO especially at higher values (at about >2 ml and >0.4 l min(-1), respectively). Coefficient of variation of SV was 48.9% and 52%, for EC and echocardiography. SV and CO rose with increasing GA and BW following an exponential equation (R(2)>0.8).

CONCLUSION

Measuring SV and CO with EC in hemodynamically stable preterm infants shows good correlation and variability similar to that of echocardiography. A trend to overestimation exists at highest values, but it is unlikely to be clinically significant. Reference GA and BW-based nomograms for SV and CO are provided.

Influence of electrode positioning on accuracy and reproducibility of electrical velocimetry cardiac output measurements

Electrical velocimetry (EV) is one of the most recent adaptions of impedance cardiography. Previous studies yielded diverging results identifying several factors negatively influencing accuracy. Although electrode arrangement is suspected to be an influencing factor for impedance cardiography in general, no data for EV is available. We aimed to prospectively assess the influence of electrode position on the accuracy and reproducibility of cardiac output (CO) measurements obtained by EV. Two pairs of standard electrocardiographic electrodes were placed at predefined positions of the thorax in 81 patients. The inter-electrode gap was varied between either 5 or 15 cm by caudal movement of the lowest electrode. Measurements were averaged over 20 s and performed twice at each electrode position. Reference values were determined using cardiac magnetic resonance imaging (CMR). Mean bias was 1.2  ±  1.6 l min(-1) (percentage error 22  ±  28%) between COCMR and COEV at the 5 cm gap significantly improving to 0.5  ±  1.6 l min(-1) (8  ±  28%) when increasing the gap (p  <  0.0001). The mean difference between repeated measurements was 0.0  ±  0.3 l min(-1) for the 5 cm and 0.1  ±  0.3 l min(-1) for the 15 cm gap, respectively (p  =  0.3). The accuracy of EV can be significantly improved when increasing the lower inter-electrode gap still exceeding the Critchley and Critchley recommendations. Therefore, absolute values should not be used interchangeably in clinical routine. As the reproducibility was not negatively affected, serial hemodynamic measurements can be reliably acquired in stable patients when the electrode position remains unchanged.

Hemodynamic reference for neonates of different age and weight: a pilot study with electrical cardiometry

OBJECTIVE

Electrical cardiometry (EC) is an impedance-based monitor that provides noninvasive, real-time hemodynamic assessment. However, the reference values for neonates have not been established.

STUDY DESIGN

EC (Aesculon) was applied to hemodynamically stable preterm and term infants. Hemodynamic variables included cardiac output (CO), cardiac index (CI), stroke volume (SV) and heart rate (HR). Their gestational age (GA), weight and body surface area (BSA) were recorded.

RESULTS

A total of 280 neonates were studied. Their GA ranged from 26(5/7) to 41(4/7) weeks, weight 800 to 4420 g and BSA 0.07 to 0.26 m(2). CO was positively correlated to GA, weight and BSA (r=0.681, 0.822, 0.830, respectively; all P<0.001). Using regression analysis, CO was most significantly correlated to BSA. Mean CI was 2.55±0.37 l min(-1) per m(2).

CONCLUSION

Hemodynamic reference by EC is notably distinct among neonates of diverse maturity. CO is most closely correlated to BSA.

The Role of Biomarkers and Surrogate End Points in Drug Development for Neonatal Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare disease in newborns, infants, and children. It is associated with significant morbidity and mortality, but has limited treatment options. Except for inhaled nitric oxide, which is approved for persistent pulmonary hypertension of the newborn (PPHN), no drug is approved for the treatment of newborns, infants, and children with PAH. The lack of developmentally appropriate pediatric efficacy end points and pediatric clinical trials contribute to this unmet medical need. The noninvasive biomarkers reported in the literature that can be used as potential surrogate end points to assess disease severity and treatment response in neonates, infants, and children with PAH are reviewed herein. In addition, the role of the US Food and Drug Administration in developing potential biomarkers as surrogate end points to facilitate drug development for the treatment of children with PPHN and PAH in children is reviewed herein.

Influence of patent ductus arteriosus and ventilators on electrical velocimetry for measuring cardiac output in very-low/low birth weight infants

OBJECTIVE

We evaluated electrical velocimetry, a noninvasive method for continuous cardiac output measurement, in very-low and low birth weight infants and the influence of patent ductus arteriosus (PDA) and ventilators on this method.

STUDY DESIGN

This prospective study compared 81 pairs of simultaneous cardiac output measurements by electrical velocimetry and transthoracic echocardiography in 28 patients. Data were compared by correlation, Bland-Altman analysis and two-way analysis of variance.

RESULTS

The two methods exhibited a high correlation (r=0.859, P<0.0001). The bias (mean difference of the methods) and percent error (100 × 1.96 × s.d./mean cardiac output) were -6 ml min(-1) and 29.2%, respectively. PDA significantly affected the bias (P=0.0004), but ventilators did not (P=0.14). Hemodynamically significant PDA had a larger bias (-36 ml min(-1)) and higher percent error (38.6%).

CONCLUSIONS

Although influenced by PDA, electrical velocimetry was generally interchangeable with transthoracic echocardiography even using ventilators.

Prone positioning decreases cardiac output and increases systemic vascular resistance in neonates

OBJECTIVE

To evaluate the cardiovascular response to short-term prone positioning in neonates.

STUDY DESIGN

In this prospective study, we continuously monitored heart rate (HR), stroke volume (SV) and cardiac output (CO) by electrical velocimetry in hemodynamically stable neonates in each of the following positions for 10 min: supine, prone and back-to-supine position. Skin blood flow (SBF) was also continuously assessed on the forehead or foot using Laser Doppler technology. Systemic vascular resistance (SVR) index was calculated as mean blood pressure (BP)/CO. Data were analyzed using repeated measures analysis of variance.

RESULTS

Thirty neonates (gestational age: 35±4 weeks; postmenstrual age: 36±3 weeks) were enrolled. HR did not change in response to positioning. However, in prone position, SV, CO and SBF decreased and SVR index increased from 1.5±0.3 to 1.3±0.3 ml kg(-1) (mean ±s.d., P<0.01), 206±44 to 180±41 ml kg(-1) min(-1) (P<0.01), 0.54±0.30 to 0.44±0.29 perfusion units (P<0.01) and 0.25±0.06 to 0.30±0.07 mm Hg ml(-1) kg(-1) min(-1) (P<0.01), respectively. After placing the infants back-to-supine position, SV, CO, SBF and SVR index returned to baseline. The above pattern of cardiovascular changes was consistent in vast majority of the studied neonates.

CONCLUSIONS

Short-term prone positioning is associated with decreased SV, CO and SBF and increased calculated SVR index.

Hemodynamic alterations recorded by electrical cardiometry during ligation of ductus arteriosus in preterm infants

This is a prospective study using non-invasive electrical cardiometry to measure hemodynamic changes during surgical ligation of patent ductus arteriosus (PDA) in very low birth weight (VLBW, ≤1500 g) infants. The aims of this study were to examine hemodynamic aberration caused by abrupt closure of a ductal shunting and to define factors that affect hemodynamic changes. Simultaneous measurements of heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) were collected at ten time points: 1 h prior to anesthesia, at the beginning of anesthesia, starting of surgery, immediately after PDA being ligated, and 1 h followed by 6, 12, 18, 24, and 48 h after the surgery. Thirty infants with gestational age of 27.7 ± 2.0 weeks and birth weight of 929 ± 280 g were studied. Upon sudden termination of ductal shunting, there was a significant decline in CO to 73 % of presurgery baseline. The deterioration in CO was associated with a decreased SV rather than HR. At the same time, there was an increase of SVR following ductal ligation. Magnitude of CO and SV reduction were higher in smaller infants (≤1 kg), and recovery was to a lesser degree in infants with more severe PDA.

CONCLUSION

Reduced stroke volume and elevated vascular resistance contribute to the major hemodynamic aberrations in VLBW infants receiving PDA ligation surgery.

Relationship between stroke volume and pulse pressure during blood volume perturbation: a mathematical analysis

Arterial pulse pressure has been widely used as surrogate of stroke volume, for example, in the guidance of fluid therapy. However, recent experimental investigations suggest that arterial pulse pressure is not linearly proportional to stroke volume. However, mechanisms underlying the relation between the two have not been clearly understood. The goal of this study was to elucidate how arterial pulse pressure and stroke volume respond to a perturbation in the left ventricular blood volume based on a systematic mathematical analysis. Both our mathematical analysis and experimental data showed that the relative change in arterial pulse pressure due to a left ventricular blood volume perturbation was consistently smaller than the corresponding relative change in stroke volume, due to the nonlinear left ventricular pressure-volume relation during diastole that reduces the sensitivity of arterial pulse pressure to perturbations in the left ventricular blood volume. Therefore, arterial pulse pressure must be used with care when used as surrogate of stroke volume in guiding fluid therapy.

Pulse wave transit time measurements of cardiac output in patients undergoing partial hepatectomy: a comparison of the esCCO system with thermodilution

BACKGROUND

Measuring cardiac output accurately during anesthesia is thought to be helpful for safely controlling hemodynamics. Several minimally invasive methods to measure cardiac output have been developed as alternatives to thermodilution with pulmonary artery catheterization. We evaluated the reliability of a novel pulse wave transit time method of cardiac output assessment to trend with thermodilution cardiac output in patients undergoing partial hepatectomy.

METHODS

Thirty-one patients (ASA physical status II or III) undergoing partial hepatectomy under general anesthesia were evaluated. Cardiac output measurements by pulse wave transit time method and by thermodilution were recorded after induction of anesthesia, after a change in body positioning to 20° head up, after a change to 20° head down, after volume challenge with 10 mL·kg hydroxyethyl starch 6%, during the Pringle maneuver, and immediately after Pringle maneuver release. Trending was assessed using Bland-Altman analysis and concordance analysis.

RESULTS

The direction of change between consecutive pulse wave transit time measurements and the corresponding thermodilution measurements showed a concordance rate of 96.0% (lower 95% confidence interval = 64%), with limits of agreement -1.51 and 1.61 L·min.

CONCLUSIONS

The pulse wave transit time method had good concordance but fairly wide limits of agreement with regard to trending in patients with changes in preload and systemic vascular resistance. There are potential inaccuracies when vasopressors are used to treat hypotension associated with decreased systemic vascular resistance. The study limitations are that the cardiac output data were collected in a nonblinded fashion, and an existing intraarterial catheter was used, although the system requires only routine, noninvasive cardiovascular monitors. This is a promising technique that currently has limitations and will require further improvements and clinical assessment.

Neonatal hemodynamics: monitoring, data acquisition and analysis

Monitoring of cardiovascular function is critical to both clinical care and research as the use of sophisticated monitoring systems enable us to obtain accurate, reliable and real-time information on developmental hemodynamics in health and disease. Novel approaches to comprehensive hemodynamic monitoring and data acquisition will undoubtedly aid in developing a better understanding of developmental cardiovascular physiology in neonates. In addition, development and use of state-of-the-art, comprehensive hemodynamic monitoring systems enable the recognition of signs of cardiovascular compromise in its early stages, and provide information on the hemodynamic response to treatment in critically ill patients.

Comparison Between the Effects of Ringer`s Lactate and Hydroxyethyl Starch on Hemodynamic Parameters After Spinal Anesthesia: A Randomized Clinical Trial

BACKGROUND

Hypotension during spinal anesthesia is common and can lead to severe injuries and even death. Administration of crystalloid fluids is advised to prevent occurrence of hypotension; however its effectiveness is still the matter of arguments.

OBJECTIVES

This study was designed to compare the effects of Ringer`s lactate and hydroxyethyl starch 6% on hemodynamic parameters after spinal anesthesia in patients undergoing orthopedic surgeries on lower limbs.

PATIENTS AND METHODS

This randomized clinical trial was performed in Rasoul Akram Hospital, Tehran, Iran. 60 patients undergoing elective femoral fracture surgeries with spinal anesthesia were included in this study. Fitted patients were randomly divided into two equal groups. After entrance to the operation room and before spinal anesthesia, patients' hemodynamic parameters including systolic blood pressure (SBP), cardiac output (CO), and cardiac index (CI) were evaluated using monitoring electro-velocimetry set. In both groups, spinal anesthesia was performed using needle no. 25 and 3 mL of marcaine 0.5% in the sterile situation. None of the treatment group was aware of investigated group during the study.

RESULTS

The baseline values of mentioned variables did not show a significant difference between two groups using t-test (P > 0.05). Also SBP, CI, and CO after intervention was not significantly different between two groups using t-test (P > 0.05).

CONCLUSIONS

The result of present study on patients undergoing femoral fracture surgeries who received Hetastarch or Ringer`s lactate solutions showed that Hetastarch was not significantly more effective in compensation of hypotension induced by spinal anesthesia.

Non-invasive measurement of cardiac output in obese children and adolescents: comparison of electrical cardiometry and transthoracic Doppler echocardiography

The objective of this study was to evaluate the reliability and accuracy of electrical cardiometry (EC) for the noninvasive determination of cardiac output (CO) in obese children and adolescents. We compared these results with those obtained by transthoracic echocardiography. Sixty-four participants underwent simultaneous measurement of CO. Cardiac output was measured by EC using the ICON(®) device. Simultaneously CO was determined by using transthoracic Doppler echocardiography from parasternal long-axis and apical view. The median age was 12.52 years (range 7.9-17.6 years) and 36 (56 %) were female. A strongly significant correlation was found between the COEC and COEcho measurements (p < 0.0001, r = 0.91). Significant correlations were also found between CO and age (r = 0.37, p = 0.002), weight (r = 0.57, p < 0.0001), height (0.60, p < 0.0001) and BMI (r = 0.42, p = 0.001). The mean difference between the two methods (COEC - COEcho) was 0.015 l min(-1). According to the Bland and Altman method, the upper and lower limits of agreement, defined as mean difference ±2 SD, were +1.21 and -0.91 l min(-1), respectively. Compared to the transthoracic Doppler echocardiography, Electrical Cardiometry provides accurate and reliable CO measurements in obese children and adolescents.

A history of pediatric anesthesia: a tale of pioneers and equipment

The history of pediatric anesthesia is fascinating in terms of how inventive anesthesiologists became over time to address the needs for advances in surgery. We have many pioneers and heroes. We hope you will enjoy this brief overview and that we have not left out any of the early contributors to our speciality. Obviously there is insufficient space to include everyone.

Pulmonary artery catheter monitoring in 2011

PURPOSE OF REVIEW

Hemodynamic monitoring has gained widespread acceptance in intensive care units. Despite ongoing debate regarding its safety and efficacy, monitoring with the pulmonary artery catheter (PAC) remains used for the management of severe heart failure and shock.

RECENT FINDINGS

To reanalyze using the most recently published literature in the field, the role of the PAC to manage critically ill patients with right ventricular failure, pulmonary hypertension and weaning failure from cardiac origin. The role of PAC as a gold standard to validate new cardiac output monitoring devices was also reported.

SUMMARY

Despite competition with less invasive hemodynamic monitoring devices or ultrasonic methods, the PAC remains a useful monitoring device in situations in which the knowledge of pulmonary artery pressure, pulmonary artery occlusion pressure and oxygenation parameters are needed. The proper use of PAC requires, however, a perfect knowledge of the numerous pitfalls and difficulties in interpretation of its measurements.

A comparative evaluation of electrical velocimetry and inert gas rebreathing for the non-invasive assessment of cardiac output

BACKGROUND

When assessing the function of the cardiovascular system, cardiac output (CO) is a substantial parameter. For its determination, numerous non-invasive techniques have been proposed in the recent years including inert gas rebreathing (IGR) and impedance cardiography (ICG). The aim of our study was to evaluate whether a novel ICG algorithm (electrical velocimetry) and IGR can be used interchangeably in the clinical setting.

METHODS

A total of 120 consecutive stable patients were included resulting in two pairs of repeated non-invasive cardiac output measurements.

RESULTS

The mean CO was 5.0 ± 1.2 l/min (range 2.6-8.6 l/min) using IGR and 4.4 ± 1.1 l/min (1.7-7.4 l/min) using ICG, respectively. Bland-Altman analysis revealed an acceptable agreement with a mean bias of 0.6 ± 1.2 l/min. We found a high reproducibility with a mean bias of 0.2 ± 0.7 l/min for IGR and 0.0 ± 0.3 l/min for ICG (p < 0.001), respectively. There was a statistically significant difference for unphysiological circulatory conditions represented by values of 2.6-4.1 l/min and 5.6-8.6 l/min.

CONCLUSIONS

Both non-invasive techniques are associated with low operating costs and require only a few expendable items for the rapid determination of cardiac function. We found an acceptable agreement between IGR and ICG as well as a high reproducibility, which was statistically significant higher for ICG. For cardiac output states exceeding the physiological range, we found a statistically significant difference. Consequently, values of cardiac function determined by either method should not be used interchangeably in the clinical setting.

Non-invasive cardiac output and oxygen delivery measurement in an infant with critical anemia

OBJECTIVE

To assess the combination of a non-invasive blood oxygen content (CaO(2)) monitor and a non-invasive cardiac output (CO) monitor to continuously measure oxygen delivery (DO(2); DO(2) = CaO(2) × CO).

METHODS

DO(2) was assessed during blood transfusions in an infant with acute hemolytic anemia following admission (~48 h). CaO(2) was measured by Pulse Co-Oximetry, which also provides estimates of hemoglobin (Hgb) concentration and percent oxygen saturation. CO was measured by Electrical Velocimetry, which also provides an estimate of stroke volume (SV). Lactate levels, an indirect measure of adequate DO(2), were assessed during the initial 8 h following admission.

RESULTS

Incremental blood transfusions during the first 36 h increased Hgb from 2.7 to 9.5 g/dL during which time heart rate (HR) normalized from 156 to 115 beats/min. Lactate levels decreased from 20 to 0.8 mmol/L in the first 7 h. Non-invasive Hgb and CaO(2) measurements were well correlated with invasive Hgb and CaO(2) measures (r (2) = 0.88; P = 0.019; r (2) = 0.86; P = 0.0074, respectively). CO decreased from 2.47 ± 0.06 to 1.28 ± 0.02 L/min and SV decreased from 15.9 ± 0.4 to 11.1 ± 0.2 mL/beat. Mean arterial blood pressure was stable throughout the admission with systemic vascular resistance increasing from 407.6 ± 15.2 to 887.7 ± 30.1 dynes-s/cm(5). DO(2) was estimated to increase from 120.2 ± 18.9 to 182.4 ± 5.6 mL O(2)/min.

CONCLUSIONS

Non-invasive continuous CO and CaO(2) monitors are shown in this single case to provide continuous DO(2) measurement. The ability to assess DO(2) may improve hemodynamic monitoring during goal directed therapies.

Evaluation of a new software version of the FloTrac/Vigileo (version 3.02) and a comparison with previous data in cirrhotic patients undergoing liver transplant surgery

BACKGROUND

Reliable cardiac output monitoring is particularly useful in the cirrhotic patient undergoing liver transplant surgery, because cirrhosis of the liver is associated with a vasodilated and high output state, known as cirrhotic cardiomyopathy, that challenges the reliability of pulse contour cardiac output technology. The contractility of the ventricle in cirrhosis is impaired, which is tolerated even though the ejection fraction and cardiac output are elevated because of the low peripheral resistance. However, during surgery the cirrhotic patient can decompensate because of the physiological changes and stress of surgery. Recently, we showed that the FloTrac/Vigileo™ failed to perform in cirrhotic patients undergoing transplant surgery. In response, the company upgraded their software. Therefore, we have assessed the accuracy and reliability of this new third-generation (version 3.02) FloTrac/Vigileo algorithm software in the same setting.

METHODS

The cardiac index was measured simultaneously by single-bolus thermodilution (CI(TD)), using a pulmonary artery catheter, and pulse contour analysis, using the FloTrac/Vigileo (CI(V)). Readings were made at 10 time points during and after liver transplant surgery in 21 patients. Comparisons with data from our 2009 study, which used second-generation (version 01.10) software, were also made.

RESULTS

Our new data show that version 3.02 software significantly reduced the adverse effect on pulse contour cardiac output reading bias in low peripheral resistance states, and thus improves the overall precision and trending ability of the system. Regression analysis between CI(TD) and CI(V) showed that the correlation was moderate (r =0.67, 95% confidence interval, 0.40 to 0.86). The Bland and Altman analysis showed that bias was 0.4 L.min(-1) · m(-2), and the percentage error was 52% (95% confidence interval, 49% to 55%). Trending ability of the new software also was improved but was still well below the current benchmarks.

CONCLUSION

The new software (version 3.02) provided substantial improvements over the previous versions with better overall precision and trending ability. Further algorithm refinements will increase this technology's reliability to be extensively used in the highly complex setting of cirrhotic patients undergoing liver transplantation.