Clinical validation of bioreactance for the measurement of cardiac output in pregnancy

Bioreactance noninvasive cardiac output monitoring in euvolemic adult horses subjected with 7.2% saline and 6% hydroxyethyl starch (130/0.4) solution infusions

OBJECTIVE

To compare the ability of bioreactance noninvasive cardiac output (BR-NICO) with thermodilution cardiac output (TDCO) for the measurement of cardiac output (CO) in healthy adult horses receiving 2 different IV volume replacement solutions.

DESIGN

Prospective randomized crossover study from September to November 2021.

SETTING

University teaching hospital.

ANIMALS

Six university-owned adult horses.

INTERVENTIONS

Horses were randomly assigned to receive 7.2% hypertonic saline solution (HSS) or 6% hydroxyethyl starch (130/0.4) solution (HETA). BR-NICO and TDCO were measured simultaneously at baseline, 10, 20, 30, 40, 50, 60, 90, and 120 minutes before fluid administration and again at the same times after starting a bolus infusion of IV volume replacers. All solutions were administered within 10 minutes.

MEASUREMENTS AND MAIN RESULTS

BR-NICO and TDCO were strongly correlated (Pearson r2 = 0.93; P < 0.01). Regression analysis showed the relationship between TDCO and BR-NICO was BR-NICO = 0.48 × TDCO + 0.6. For the corrected BR-NICO values, the Bland-Altman agreement mean bias and lower/upper limits of agreement were -0.62 and -5.3 to 3.9 L/min, respectively. Lin's concordance (95% confidence interval) between methods was 0.894 (0.825-1.097). Compared with baseline, HSS increased the CO at 10 and 20 minutes (TDCO and BR-NICO). Compared with baseline, HETA decreased the CO at 10 and 20 minutes (TDCO and BR-NICO) and increased the CO at 90 (TDCO only) and 120 minutes (TDCO and BR-NICO).

CONCLUSIONS

BR-NICO strongly agreed with TDCO in the measurement of CO in healthy unsedated adult horses. HSS administration significantly increased CO in the first 30 minutes, while HETA initially decreased CO at 10 minutes but increased CO to above baseline values by 90 minutes.

Longitudinal maternal cardiac function in hypertensive disorders of pregnancy

BACKGROUND

Compared with gestational hypertension, preeclampsia has traditionally been considered the worse end of the spectrum of hypertensive disorders of pregnancy. It is associated with worse pregnancy outcomes and future cardiovascular morbidities. Both hypertensive disorders may be associated with cardiac maladaptation in pregnancy. However, previous studies were limited by small numbers and a paucity of longitudinal data and unaccounted for the contribution of maternal characteristics that can affect hemodynamics.

OBJECTIVE

This study aimed to assess, in an unselected population, the maternal cardiac adaptation in normotensive and hypertensive pregnancies after controlling for important maternal characteristics that affect maternal cardiac function and the interaction among these covariates.

STUDY DESIGN

This was a prospective, multicenter longitudinal study of maternal hemodynamics, assessed by a noninvasive bioreactance technology, measured at 11 0/7 to 13 6/7, 19 0/7 to 24 0/7, 30 0/7 to 34 0/7, and 35 0/7 to 37 0/7 weeks of gestation in 3 groups of women. Group 1 was composed of women with preeclampsia (n=45), group 2 was composed of women with gestational hypertension (n=61), and group 3 was composed of normotensive women (n=1643). A multilevel linear mixed-effects model was performed to compare the repeated measures of hemodynamic variables controlling for maternal age, height, weight, weight gain, race, previous obstetrical history, and birthweight.

RESULTS

After adjusting for confounders that significantly affect maternal hemodynamics, both group 1 and group 2, compared with group 3, had pathologic cardiac adaptation. Group 1, compared with group 3, demonstrated hyperdynamic circulation with significantly higher cardiac output driven by greater stroke volume in the first trimester of pregnancy. As the pregnancies progressed to after 20 0/7 weeks of gestation, this hyperdynamic state transitioned to hypodynamic state with low cardiac output and high peripheral vascular resistance. Group 2, compared with group 3, had no significant differences in cardiac output, stroke volume, and heart rate before 20 0/7 weeks of gestation but thereafter demonstrated a continuous decline in cardiac output and stroke volume, similar to group 1. Both groups 1 and 2, compared with group 3, had persistently elevated mean arterial pressure and uterine artery pulsatility index throughout pregnancy.

CONCLUSION

After adjusting for confounders that affect maternal hemodynamics in an unselected pregnant population, women with preeclampsia and gestational hypertension, compared with normotensive women, demonstrated similar cardiac maladaptation. This pathologic profile was evident after 20 0/7 weeks of gestation and at least 10 weeks before the clinical manifestation of the disease.

Accuracy and trending ability of finger plethysmographic cardiac output monitoring in late pregnancy

PURPOSE

Individuals in late pregnancy are at risk of significant hemodynamic variations, especially during Cesarean delivery. Although non-invasive monitoring might enable the early detection of variations in cardiac output (CO), clinical validation is lacking.

METHODS

In a prospective, single-center study, we measured CO simultaneously with finger plethysmography and transthoracic echocardiography in 100 third-trimester pregnant individuals in the supine and left lateral decubitus (LLD) positions.

RESULTS

A Bland-Altman analysis revealed a mean (standard deviation) bias of 1.36 (1.04) L·min-1 in the supine position (95% limits of agreement, -0.68 to 3.4 L·min-1; percent error, 26.6%), indicating overestimation by finger plethysmography. The intra-class correlation coefficient was 0.43 (95% confidence interval [CI], 0.33 to 0.51). Regarding the changes in CO induced by the supine-to-LLD transition, the concordance rate in a four-quadrant plot was 98.3% (95% CI, 91.1 to 99.9%).

CONCLUSION

Our study showed a poor reliability of finger plethysmography for static measurement of CO. Nevertheless, finger plethysmography had a reasonably high concordance rate for the detection of CO changes secondary to positional changes in late-pregnant individuals. STUDY REGISTRATION DATE: www.

CLINICALTRIALS

gov (NCT03735043); registered 8 November 2018.

Impact of maternal height, weight at presentation and gestational weight gain on cardiac adaptation in pregnancy

OBJECTIVE

To compare longitudinal maternal hemodynamic changes throughout gestation between different groups stratified according to weight at presentation and assess the relative influence of height, weight at presentation and gestational weight gain on cardiac adaptation.

METHODS

This was a prospective, longitudinal study assessing maternal hemodynamics using bioreactance technology at 11 + 0 to 13 + 6, 19 + 0 to 24 + 0, 30 + 0 to 34 + 0 and 35 + 0 to 37 + 0 weeks' gestation. Women were divided into three groups according to maternal weight at presentation at the first visit at 11 + 0 to 13 + 6 weeks: Group 1, &lt; 60.0 kg (n = 421); Group 2, 60.0-79.7 kg (n = 904); Group 3, &gt; 79.7 kg (n = 427). A multilevel linear mixed-effects model was used to compare the repeated measures of hemodynamic variables, correcting for demographics, medical and obstetric history, pregnancy complications, maternal weight and time of evaluation. The linear mixed-effects model was then repeated using maternal height, weight at presentation and gestational weight gain Z-scores, and the standardized coefficients were used to evaluate the relative impact of each of these demographic parameters on longitudinal changes of maternal hemodynamics.

RESULTS

Compared with Group 1, women in Group 3 demonstrated higher cardiac output (CO), heart rate (HR) and mean arterial pressure (MAP) throughout pregnancy. Groups 2 and 3 had higher stroke volume (SV) than Group 1 at the first visit, but their SV plateaued between the first and second visits and demonstrated an earlier significant decrease from the second visit to the third visit when compared with Group 1. Compared with Groups 1 and 2, there was a higher prevalence of pre-eclampsia, gestational hypertension and gestational diabetes in Group 3. Maternal height was the most important contributor to CO, peripheral vascular resistance (PVR), SV and HR, while weight at presentation was the most important contributor to MAP. Gestational weight gain was the second most important characteristic influencing the longitudinal changes of PVR and SV.

CONCLUSIONS

Women with greater weight at presentation have a pathological hemodynamic profile, with higher CO, HR and MAP compared to women with lower weight at presentation. Height is the main determinant of CO, SV, HR and PVR, weight is the main determinant of MAP, and gestational weight gain is the second most important determinant of SV and PVR. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Quantification of stroke volume in a simulated healthy volunteer model of traumatic haemorrhage; a comparison of two non-invasive monitoring devices using error grid analysis alongside traditional measures of agreement

Introduction

Haemorrhage is a leading cause of death following traumatic injury and the early detection of hypovolaemia is critical to effective management. However, accurate assessment of circulating blood volume is challenging when using traditional vital signs such as blood pressure. We conducted a study to compare the stroke volume (SV) recorded using two devices, trans-thoracic electrical bioimpedance (TEB) and supra-sternal Doppler (SSD), against a reference standard using trans- thoracic echocardiography (TTE).

Methods

A lower body negative pressure (LBNP) model was used to simulate hypovolaemia and in half of the study sessions lower limb tourniquets were applied as these are common in military practice and can potentially affect some haemodynamic monitoring systems. In order to provide a clinically relevant comparison we constructed an error grid alongside more traditional measures of agreement.

Results

21 healthy volunteers aged 18–40 were enrolled and underwent 2 sessions of LBNP, with and without lower limb tourniquets. With respect to absolute SV values Bland Altman analysis showed significant bias in both non-tourniquet and tourniquet strands for TEB (-42.5 / -49.6 ml), rendering further analysis impossible. For SSD bias was minimal but percentage error was unacceptably high (35% / 48%). Degree of agreement for dynamic change in SV, assessed using 4 quadrant plots showed a seemingly acceptable concordance rate for both TEB (86% / 93%) and SSD (90% / 91%). However, when results were plotted on an error grid, constructed based on expert clinical opinion, a significant minority of measurement errors were identified that had potential to lead to moderate or severe patient harm.

Conclusion

Thoracic bioimpedance and suprasternal Doppler both demonstrated measurement errors that had the potential to lead to clinical harm and caution should be applied in interpreting the results in the detection of early hypovolaemia following traumatic injury.

A Detailed Review of Critical Care Considerations for the Pregnant Cardiac Patient

Maternal cardiovascular disease is a leading cause of maternal death worldwide and recently, maternal mortality has increased secondary to cardiovascular causes. Maternal admissions to critical care encompass 1%-2% of all critical care admissions, and although not common, the management of the critically ill pregnant patient is complex. Caring for the critically ill pregnant cardiac patient requires integration of pregnancy-associated physiologic changes, understanding pathophysiologic disease states unique to pregnancy, and a multidisciplinary approach to timing around delivery as well as antenatal and postpartum care. Herein we describe cardiorespiratory changes that occur during pregnancy and the differential diagnosis for cardiorespiratory failure in pregnancy. Cardiorespiratory diseases that are either associated or exacerbated by pregnancy are highlighted with emphasis on perturbations secondary to pregnancy and appropriate management strategies. Finally, we describe general management of the pregnant cardiac patient admitted to critical care.

Lung-to-finger circulation time can be measured stably with high reproducibility by simple breath holding method in cardiac patients

Lung to finger circulation time (LFCT) has been used to estimate cardiac function. We developed a new LFCT measurement device using a laser sensor at fingertip. We measured LFCT by measuring time from re-breathing after 20 s of breath hold to the nadir of the difference of transmitted red light and infrared light, which corresponds to percutaneous oxygen saturation. Fifty patients with heart failure were enrolled. The intrasubject stability of the measurement was assessed by the intraclass correlation coefficient (ICC). The ICC calculated from 44 cases was 0.85 (95% confidence interval: 0.77–0.91), which means to have “Excellent reliability.” By measuring twice, at least one clear LFCT value was obtained in 89.1% of patients and the overall measurability was 95.7%. We conducted all LFCT measurements safely. High ICCs were obtained even after dividing patients according to age, cardiac index (CI); 0.85 and 0.84 (≥ 75 or < 75 years group, respectively), 0.81 and 0.84 (N = 26, ≥ or < 2.2 L/min/M²). These results show that our new method to measure LFCT is highly stable and feasible for any type of heart failure patients.

Effect of maternal age on cardiac adaptation in pregnancy

OBJECTIVE

To compare longitudinal maternal hemodynamic changes throughout gestation between different age groups.

METHODS

This was a prospective longitudinal study assessing maternal hemodynamics using a bioreactance technique at 11 + 0 to 13 + 6, 19 + 0 to 24 + 0, 30 + 0 to 34 + 0 and 35 + 0 to 37 + 0 weeks' gestation. Women were divided into four groups according to maternal age at the first visit at 11 + 0 to 13 + 6 weeks: Group 1, < 25.0 years; Group 2, 25.0-30.0 years; Group 3, 30.1-34.9 years; and Group 4, ≥ 35.0 years. A multilevel linear mixed-effects model was performed to compare the repeat measurements of hemodynamic variables, correcting for demographics, medical and obstetric history, pregnancy complications, maternal age and gestational-age window.

RESULTS

The study population included 254 women in Group 1, 442 in Group 2, 618 in Group 3 and 475 in Group 4. Younger women (Group 1) had the highest cardiac output (CO) and lowest peripheral vascular resistance (PVR), and older women (Group 4) had the lowest CO and highest PVR throughout pregnancy. The higher CO seen in younger women was achieved through an increase in heart rate alone and not with a concomitant rise in stroke volume. Although the youngest age group demonstrated an apparently more favorable hemodynamic profile, it had the highest incidence of a small-for-gestational-age neonate. There was no significant difference between the groups in the incidence of pre-eclampsia.

CONCLUSION

Age-specific differences in maternal hemodynamic adaptation do not explain the differences in the incidence of a small-for-gestational-age neonate between age groups. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Maternal cardiac adaptation and fetal growth

BACKGROUND

Pregnancies with small-for-gestational-age fetuses are at increased risk of adverse maternal-fetal outcomes. Previous studies examining the relationship between maternal hemodynamics and fetal growth were mainly focused on high-risk pregnancies and those with fetuses with extreme birthweights, such as less than the 3rd or 10th percentile and assumed a similar growth pattern in fetuses above the 10th percentile throughout gestation.

OBJECTIVE

This study aimed to evaluate the trends in maternal cardiac function, fetal growth, and oxygenation with advancing gestational age in a routine obstetrical population and all ranges of birthweight percentiles.

STUDY DESIGN

This was a prospective, longitudinal study assessing maternal cardiac output and peripheral vascular resistance by bioreactance at 11⁺⁰ to 13⁺⁶, 19⁺⁰ to 24⁺⁰, 30⁺⁰ to 34⁺⁰, and 35⁺⁰ to 37⁺⁰ weeks' gestation, sonographic estimated fetal weight in the last 3 visits and the ratio of the middle cerebral artery by umbilical artery pulsatility indices or cerebroplacental ratio in the last 2 visits. Women were divided into the following 5 groups according to birthweight percentile: group 1, <10th percentile (n=261); group 2, 10 to 19.9 percentile (n=180); group 3, 20 to 29.9 percentile (n=189); group 4, 30 to 69.9 percentile (n=651); and group 5, ≥70th percentile (n=508). The multilevel linear mixed-effects model was performed to compare the repeated measures of hemodynamic variables and z scores of the estimated fetal weight and cerebroplacental ratio.

RESULTS

In visit 2, compared with visit 1, in all groups, cardiac output increased, and peripheral vascular resistance decreased. At visit 3, groups 1, 2, and 3, compared with 4 and 5, demonstrated an abrupt decrease in cardiac output and increase in peripheral vascular resistance. From visit 2, group 1 had a constant decline in estimated fetal weight, coinciding with the steepest decline in maternal cardiac output and rise in peripheral vascular resistance. In contrast, in groups 4 and 5, the estimated fetal weight had a stable or accelerative pattern, coinciding with the greatest increase in cardiac output and lowest peripheral vascular resistance. Groups 2 and 3 showed a stable growth pattern with intermediate cardiac output and peripheral vascular resistance. Increasing birthweight was associated with higher cerebroplacental ratio. Groups 3, 4, and 5 had stable cerebroplacental ratio across visits 3 and 4, whereas groups 1 and 2 demonstrated a significant decline (P<.001).

CONCLUSION

In a general obstetrical population, maternal cardiac adaptation at 32 weeks' gestation parallels the pattern of fetal growth and oxygenation; babies with birthweight<20th percentile have progressive decline in fetal cerebroplacental ratio, decline in maternal cardiac output, and increase in peripheral vascular resistance.