Anneleen Staelens

The use of bio-electrical impedance analysis (BIA) to guide fluid management, resuscitation and deresuscitation in critically ill patients: a bench-to-bedside review

The impact of a positive fluid balance on morbidity and mortality has been well established. However, little is known about how to monitor fluid status and fluid overload. This narrative review summarises the recent literature and discusses the different parameters related to bio-electrical impedance analysis (BIA) and how they might be used to guide fluid management in critically ill patients. Definitions are listed for the different parameters that can be obtained with BIA; these include among others total body water (TBW), intracellular water (ICW), extracellular water (ECW), ECW/ICW ratio and volume excess (VE). BIA allows calculation of body composition and volumes by means of a current going through the body considered as a cylinder. Reproducible measurements can be obtained with tetrapolar electrodes with two current and two detection electrodes placed on hands and feet. Modern devices also apply multiple frequencies, further improving the accuracy and reproducibility of the results. Some pitfalls and conditions are discussed that need to be taken into account for correct BIA interpretation. Although BIA is a simple, noninvasive, rapid, portable, reproducible, and convenient method of measuring body composition and fluid distribution with fewer physical demands than other techniques, it is still unclear whether it is sufficiently accurate for clinical use in critically ill patients. However, the potential clinical applications are numerous. An overview regarding the use of BIA parameters in critically ill patients is given, based on the available literature. BIA seems a promising tool if performed correctly. It is non-invasive and relatively inexpensive and can be performed at bedside, and it does not expose to ionising radiation. Modern devices have very limited between-observer variations, but BIA parameters are population-specific and one must be aware of clinical situations that may interfere with the measurement such as visible oedema, nutritional status, or fluid and salt administration. BIA can help guide fluid management, resuscitation and de-resuscitation. The latter is especially important in patients not progressing spontaneously from the Ebb to the Flow phase of shock. More research is needed in critically ill patients before widespread use of BIA can be suggested in this patient population.

Non-invasive assessment of gestational hemodynamics: benefits and limitations of impedance cardiography versus other techniques

To obtain data for maternal stroke volume and cardiac output during pregnancy, it is preferable to use a non-invasive, accurate and reproducible method. In this aspect, impedance cardiography is an excellent technique which is also highly accessible and easy to perform. This paper is a comprehensive review on the published literature about impedance cardiography and highlights the strengths and limitations of its applications in obstetrics.

Maternal venous Doppler characteristics are abnormal in pre‐eclampsia but not in gestational hypertension

To compare functional characteristics of maternal thoraco‐abdominal arteries and veins in proteinuric and non‐proteinuric hypertension in pregnancy.

Intra-Abdominal Pressure Measurements in Term Pregnancy and Postpartum: An Observational Study

Objective To determine intra-abdominal pressure (IAP) and to evaluate the reproducibility of IAP-measurements using the Foley Manometer Low Volume (FMLV) in term uncomplicated pregnancies before and after caesarean section (CS), relative to two different reference points and to non-pregnant values. Design Observational cohort study. Setting Secondary level referral center for feto-maternal medicine. Population Term uncomplicated pregnant women as the case-group and non-pregnant patients undergoing a laparoscopic assisted vaginal hysterectomy (LAVH) as control group. Methods IAP was measured in 23 term pregnant patients, before and after CS and in 27 women immediately after and 1 day after LAVH. The midaxillary line was used as zero-reference (IAPMAL) in all patients and in 13 CS and 13 LAVH patients, the symphysis pubis (IAPSP) was evaluated as additional zero-reference. Intraobserver correlation (ICC) was calculated for each zero-reference. Paired students t-tests were performed to compare IAP values and Pearsons correlation was used to assess correlations between IAP and gestational variables. Main outcome measures ICC before and after surgery, IAP before and after CS, IAP after CS and LAVH. Results The ICC for IAPMAL before CS was lower than after (0.71 versus 0.87). Both mean IAPMAL and IAPSP were significantly higher before CS than after: 14.0±2.6 mmHg versus 9.8±3.0 mmHg (p<0.0001) and 8.2±2.5 mmHg versus 3.5±1.9 mmHg (p = 0.010), respectively. After CS, IAP was not different from values measured in the LAVH-group. Conclusion IAP-measurements using FMLV is reproducible in pregnant women. Before CS, IAP is increased in the range of intra-abdominal hypertension for non-pregnant individuals. IAP significantly decreases to normal values after delivery.

Maternal venous hemodynamics in gestational hypertension and preeclampsia

BackgroundTo evaluate characteristics of venous hemodynamics, together with cardiac and arterial function, in uncomplicated pregnancies (UP), non-proteinuric gestational hypertension (GH) and preeclampsia (PE).MethodsIn this observational cross-sectional study, venous hemodynamics was assessed using a standardised protocol for combined electrocardiogram (ECG)-Doppler ultrasonography, together with a non-invasive standardised cardiovascular assessment using impedance cardiography (ICG) in 13 women with UP, 21 with GH, 34 with late onset PE ≥ 34 w (LPE) and 22 with early onset PE < 34 w (EPE). ECG-Doppler parameters were impedance index at the level of hepatic veins (HVI) and renal interlobar veins (RIVI) together with venous pulse transit times (VPTT), as well as resistive and pulsatility index, and arterial pulse transit time (APTT) at the level of uterine arcuate arteries. ICG parameters were aortic flow velocity index (VI), acceleration index (ACI) and thoracic fluid content. Mann Whitney U-test, Kruskall-Wallis test and linear regression analysis with heteroskedastic variance was used for statistical analysis.ResultsRIVI in both kidneys was >15% higher (P ≤ .010) in LPE and EPE, as compared to GH and UP. Next to this, >30% lower values for VI and ACI (P ≤ .029), and > 15% lower values for APTT (P ≤ .012) were found in GH, LPE and EPE, as compared to GH.ConclusionIn comparison to UP, similar abnormalities of central arterial function and APTT were found in GH, EPE and LPE. Proteinuria of LPE and EPE was associated with increased RIVI, this was not observed in GH.

IMPROVING THE RELIABILITY OF VENOUS DOPPLER FLOW MEASUREMENTS: RELEVANCE OF COMBINED ECG, TRAINING AND REPEATED MEASURES

The nature of venous Doppler waves is highly variable. An additional electrocardiogram (ECG) improves the interpretation of venous Doppler wave characteristics and allows measurement of venous pulse transit time. The purpose of this study was to assess the reproducibility of ECG-guided repeated measurements of venous Doppler flow characteristics before and after sonographer training and the inter- and intra-observer variability. In four groups of 25 healthy women, venous Doppler flow measurements were performed at the level of the kidneys and liver according to a standardized protocol. Intra-observer Pearson correlation coefficients of the renal interlobar vein Doppler indices were ≥ 0.80 with the addition of the ECG, which are higher than the results of a former study. The inter-observer correlation between an experienced ultrasonographer and an inexperienced ultrasonographer improved from ≥ 0.71 to ≥ 0.91 after training. The correlation range of all parameters between two independent observers improved when values were based on repeated measures. The addition of an ECG to the Doppler image, training and repeated measurements are helpful in improving venous Doppler wave interpretation.

Remote Monitoring of Hypertension Diseases in Pregnancy: A Pilot Study

Background Although remote monitoring (RM) has proven its added value in various health care domains, little is known about the remote follow-up of pregnant women diagnosed with a gestational hypertensive disorders (GHD). Objective The aim of this study was to evaluate the added value of a remote follow-up program for pregnant women diagnosed with GHD. Methods A 1-year retrospective study was performed in the outpatient clinic of a 2nd level prenatal center where pregnant women with GHD received RM or conventional care (CC). Primary study endpoints include number of prenatal visits and admissions to the prenatal observation ward. Secondary outcomes include gestational outcome, mode of delivery, neonatal outcome, and admission to neonatal intensive care (NIC). Differences in continuous and categorical variables in maternal demographics and characteristics were tested using Unpaired Student’s two sampled t test or Mann-Whitney U test and the chi-square test. Both a univariate and multivariate analysis were performed for analyzing prenatal follow-up and gestational outcomes. All statistical analyses were done at nominal level, Cronbach alpha=.05. Results Of the 166 patients diagnosed with GHD, 53 received RM and 113 CC. After excluding 5 patients in the RM group and 15 in the CC group because of the missing data, 48 patients in RM group and 98 in CC group were taken into final analysis. The RM group had more women diagnosed with gestational hypertension, but less with preeclampsia when compared with CC (81.25% vs 42.86% and 14.58% vs 43.87%). Compared with CC, univariate analysis in RM showed less induction, more spontaneous labors, and less maternal and neonatal hospitalizations (48.98% vs 25.00%; 31.63% vs 60.42%; 74.49% vs 56.25%; and 27.55% vs 10.42%). This was also true in multivariate analysis, except for hospitalizations. Conclusions An RM follow-up of women with GHD is a promising tool in the prenatal care. It opens the perspectives to reverse the current evolution of antenatal interventions leading to more interventions and as such to ever increasing medicalized antenatal care.

Maternal cardiovascular profiling in the first trimester of pregnancies complicated with gestation-induced hypertension or fetal growth retardation: a pilot study

Abstract Objective: In this study, we determine whether maternal cardiovascular (CV) profiling can detect first trimester differences between women with uncomplicated pregnancies (UP) and those who will develop gestational hypertensive disorders (GHD) or normotensive fetal growth retardation (FGR). Methods: Cardiac, arterial, and venous function were evaluated in 242 pregnant women around 12 weeks of gestation, using impedance cardiography (ICG) and combined electrocardiogram – Doppler ultrasonography. After postnatal determination of gestational outcome, first trimester measurements were compared between groups using Mann–Whitney U test for continuous data or Fisher’s Exact test for categorical variables (SPSS 20.0). Results: Compared to UP, first trimester aortic flow velocity index [71 ± 0.96 versus 61 ± 4.91 1/1000/s (p = 0.016)], acceleration index [133 ± 2.25 versus 106 ± 11.26 1/100/s2 (p = 0.023)] and Heather index [23.1 ± 0.35 versus 19.2 ± 1.70 Ω/s2 (p = 0.019)] were lower in GHD pregnancies, and first trimester stroke volume [77 ± 1.16 versus 67 ± 3.97 ml (p = 0.033)] and cardiac output [7.3 ± 0.10 versus 6.2 ± 0.31 l/min (p = 0.025)] were lower in FGR pregnancies. Conclusions: Maternal CV function in the first trimester of pregnancy differs between UP and those destined to develop GHD or FGR. This can be assessed with non-invasive maternal CV profiling, opening perspectives for the application of this technique in early gestational screening for GHD and FGR.

Hepatic Hemodynamics and Fetal Growth: A Relationship of Interest for Further Research

Background It is well known that hepatic hemodynamics is an important physiologic mechanism in the regulation of cardiac output (CO). It has been reported that maternal cardiac output relates to neonatal weight at birth. Aims In this study, we assessed the correlation between maternal hepatic vein Doppler flow parameters, cardiac output and neonatal birth weight. Methods Healthy women with uncomplicated second or third trimester pregnancy attending the outpatient antenatal clinic of Ziekenhuis Oost-Limburg in Genk (Belgium), had a standardized combined electrocardiogram-Doppler ultrasound with Impedance Cardiography, for measurement of Hepatic Vein Impedance Index (HVI  =  [maximum velocity – minimum velocity]/maximum velocity), venous pulse transit time (VPTT  =  time interval between corresponding ECG and Doppler wave characteristics) and cardiac output (heart rate x stroke volume). After delivery, a population-specific birth weight chart, established from a cohort of 27000 neonates born in the index hospital, was used to define customized birth weight percentiles (BW%). Correlations between HVI, VPTT, CO and BW% were calculated using Spearmans ρ, linear regression analysis and R2 goodness of fit in SPSS 22.0. Results A total of 73 women were included. There was a negative correlation between HVI and VPTT (ρ = −0.719, p<0.001). Both HVI and VPTT correlated with CO (ρ = −0.403, p<0.001 and ρ = 0.332, p<0.004 resp.) and with BW% (ρ = −0.341, p<0.003 and ρ = 0.296, p<0.011 resp.) Conclusion Our data illustrate that the known contribution of hepatic hemodynamics in the regulation of cardiac output is also true for women with uncomplicated pregnancies. Our study is the first to illustrate a potential link between maternal hepatic hemodynamics and neonatal birth weight. Whether this link is purely associative or whether hepatic vascular physiology has a direct impact on fetal growth is to be evaluated in more extensive clinical and experimental research.

Clinical inference of maternal renal venous Doppler ultrasonography

Abstract Venous compliance is known to differ between uncomplicated and preeclamptic pregnancies and can be assessed using Doppler ultrasonography. The purpose of this report is to address some of the interfering conditions in order to illustrate some of the limitations of venous Doppler sonography. Five case reports of pregnant women with important morbidity were selected: (1) auto-immune vasculitis, (2) polycystic renal dysplasia, (3) hydronephrosis, (4) HELLP syndrome and (5) morbid obesity. All cases had a Doppler flow examination of renal interlobar veins according to a standardized protocol and venous impedance index of left and right kidney was calculated. Results were plotted on a normal reference curve. Renal venous Doppler sonography may be hampered by maternal comorbidities or disease-specific conditions due to which it is difficult or even impossible to perform or interpret the Doppler signal.