Effect of airway pressure on inferior vena cava pressure as a measure of central venous pressure in children

Evaluation of caudal vena cava size using computed tomography in dogs under general anesthesia

This study investigated the association between caudal vena cava (CVC) size and circulatory dynamics in dogs using computed tomography (CT) under general anesthesia. The subjects were 104 dogs who had undergone CT under general anesthesia in the past. The ratio of short diameter of the CVC to aortic diameter (CVC_S/Ao) and the ratio of long to short diameter of the CVC (CVC_L/CVC_S) in the thorax and abdomen, respectively, were calculated using factors such as mean blood pressure (MBP), shock index (SI), anemia, hypoproteinemia, presence of intra-abdominal mass, and cardiac disease. There was a significant but negligible negative correlation between CVC_S/Ao and MBP. In contrast, no significant correlation was found between CVC size and SI. The low MBP group had significantly higher CVC_S/Ao of the thorax than the normal MBP group. The group with intra-abdominal mass had significantly lower CVC_S/Ao of the abdomen than the group without intra-abdominal mass. The group with cardiac disease had significantly lower CVC_L/CVC_S of the thorax than the group without cardiac disease. In multiple regression analysis, low MBP, cardiac disease, intra-abdominal mass, and anemia were significant factors for CVC_S/Ao of the thorax, CVC_L/CVC_S of the thorax, CVC_S/Ao of the abdomen, and CVC_L/CVC_S of the abdomen, respectively. In conclusion, CVC size assessment using CT in dogs under general anesthesia is influenced by various factors.

Echocardiographic Assessment of Right Atrial Pressure in a Pediatric and Young Adult Population

Right atrial pressure (RAP) reflects right-sided cardiac hemodynamics and is useful in management of patients with cardiac and systemic disease. Studies in older adults demonstrated that inferior vena cava (IVC) diameter, IVC collapsibility index, hepatic vein systolic filling fraction (SFF), and right atrial volume (RAV) correlated with mean RAP at catheterization. This study aimed to assess the utility of echocardiographic parameters for assessment of RAP in children and young adults. Patients with pulmonary hypertension or heart transplantation undergoing right heart catheterization were recruited for this prospective observational pilot study. Transthoracic echocardiographic assessment of RAP was performed simultaneously with catheterization. For each parameter, three consecutive cardiac cycles were recorded. Long- and short-axis images of the IVC were obtained. RAV was assessed by area-length and biplane methods. IVC diameters and RAV were indexed to body surface area (BSA)(0.5) and (BSA)(1.4), respectively. Relationships between echocardiographic parameters and mean RAP were correlated using "Pearson's r." Fifty subjects aged 0.3-23 years (median 13, mean 12.3 ± 7 years) were enrolled. Mean RAP correlated modestly with RAV (r = 0.51, p < 0.001). Long-axis IVCmax (r = 0.30, p < 0.05) and tricuspid E wave velocity (r = 0.36, p < 0.01) also correlated with mean RAP. RV free wall tissue Doppler velocities, IVC collapsibility index, and hepatic vein SFF had no relation to mean RAP. In a pediatric and young adult population with pulmonary hypertension or heart transplantation, echocardiographic assessment of RAV and long-axis IVCmax provided a reasonable estimate of mean RAP. IVC collapsibility index and hepatic vein SFF demonstrated no association with mean RAP.

The changes of central venous pressure by body posture and positive end-expiratory pressure

BACKGROUND

Central venous pressure (CVP) monitoring provides a useful estimate of the volume status of the systemic circulation. Both increase in the intrathoracic pressure by applying positive-end expiratory pressure (PEEP) and various patient positioning may commonly mislead the interpretation of CVP. We investigated the effect of body posture and different PEEPs on CVP in anesthetized patients.

METHODS

Ninety-one patients (ASA I or II) scheduled for elective surgery with supine (50 patients), lateral decubitus (27 patients), or prone position (14 patients) were included. After induction of general anesthesia, CVP, mean arterial pressure (MAP), heart rate (HR), end-tidal CO2 (EtCO2) and peak inspiratory pressure (PIP) were measured under different PEEP conditions of 0, 5, 10, and 15 cmH2O in each body posture.

RESULTS

CVP and PIP increased gradually by the increment of PEEP in patients with all positions. The magnitude of changes of CVP and PIP was significantly greater than other PEEP conditions when PEEP was 15 cmH2O, especially in prone position (P < 0.05). There were no differences in MAP, HR and EtCO2 during the increase of PEEP in all positions.

CONCLUSIONS

These results suggest that PEEP as much as 15 cmH2O may alter reliability of CVP in estimating adequate circulatory volumes, especially in prone position.

Intensivist use of hand-carried ultrasonography to measure IVC collapsibility in estimating intravascular volume status: correlations with CVP

BACKGROUND

Volume status assessment is an important aspect of patient management in the surgical intensive care unit (SICU). Echocardiologist-performed measurement of IVC collapsibility index (IVC-CI) provides useful information about filling pressures, but is limited by its portability, cost, and availability. Intensivist-performed bedside ultrasonography (INBU) examinations have the potential to overcome these impediments. We used INBU to evaluate hemodynamic status of SICU patients, focusing on correlations between IVC-CI and CVP.

STUDY DESIGN

Prospective evaluation of hemodynamic status was conducted on a convenience sample of SICU patients with a brief (3 to 10 minutes) INBU examination. INBU examinations were performed by noncardiologists after 3 hours of didactics in interpreting and acquiring two-dimensional and M-mode images, and > or =25 proctored examinations. IVC-CI measurements were compared with invasive CVP values.

RESULTS

Of 124 enrolled patients, 101 had CVP catheters (55 men, mean age 58.3 years, 44.6% intubated). Of these, 18 patients had uninterpretable INBU examinations, leaving 83 patients with both CVP monitoring devices and INBU IVC evaluations. Patients in three IVC-CI ranges (<0.20, 0.20 to 0.60, and >0.60) demonstrated significant decrease in mean CVP as IVC-CI increased (p = 0.023). Although <5% of patients with IVC-CI <0.20 had CVP <7 mmHg, >40% of this group had a CVP >12 mmHg. Conversely, >60% of patients with IVC-CI >0.6 had CVP <7 mmHg.

CONCLUSIONS

Measurements of IVC-CI by INBU can provide a useful guide to noninvasive volume status assessment in SICU patients. IVC-CI appears to correlate best with CVP in the setting of low (<0.20) and high (>0.60) collapsibility ranges. Additional studies are needed to confirm and expand on findings of this study.

Establishing normal values of central venous pressure in very low birth weight infants

The objective of this paper is to establish a reference range of central venous pressure (CVP) values during the first 4 days of life in very low birth weight (VLBW) infants. A prospective observational study with continuous monitoring of CVP in VLBW newborns who had an umbilical venous catheter (UVC) positioned in or near the right atrium is conducted. All UVCs were inserted as part of normal care of the infants. The mean CVP (mCVP) was monitored for 72 h from recruitment, or until the UVC was removed. The mean mCVP was calculated for each infant. The median of the mean mCVPs was then calculated. Data were analysed in 17 infants. The median gestational age was 27 weeks and median birth weight was 940 g. Sixteen were mechanically ventilated and of these, six also received continuous positive airway pressure (CPAP) during the study period. One infant received no respiratory support. One infant died during the study period. The lowest mean mCVP was 2.8 mmHg and the highest was 13.9 mmHg. The median mean mCVP was 4.9 mmHg (interquartile range 4.4-6.1). The normal range of CVP in VLBW infants during the first 4 days of life is wider than previously suggested.

Estimation of central venous pressure by ultrasound

INTRODUCTION

Increasing blood volume and cardiac output is one of the most commonly needed intervention in the primary care of traumatized and severely ill patients. Although cardiac filling pressures have severe limitations in assessing the preload, central venous pressure (CVP) is the invasive measure most frequently used in clinical practice for the assessment of volume status and cardiac preload. We combined ultrasound and tissue pressure measurement for non-invasive jugular and brachial venous pressure estimation.

MATERIALS AND METHODS

CVP was measured invasively and non-invasively using the new technique in 32 critically ill patients. In six volunteers, increasing PEEP was used for the assessment of changes in non-invasive CVP.

RESULTS

Non-invasive CVP increased linearly with increasing PEEP, independent of the investigator. Median (range) coefficient of variation (CV) for five consecutive measurements performed by three investigators in volunteers was 15% (6-31%), 14% (4-31%), and 21% (8-42%). Absolute differences between the average non-invasive CVP between investigators was 1.7 cm H2O (0.4-6.6 cm H2O), and the inter-examiner CVP was high (182%, 40-415%). In patients, invasive CVP was 10 mmHg (5-18 mmHg), and the corresponding non-invasive venous pressures were 8 mmHg (3-14 mmHg, basilic vein, p<0.01) and 6 mmHg (3-13 mmHg, jugular vein, p<0.01). The coefficients of variation were 4% (<1%-64%, invasive CVP), 22% (5%-51%, non-invasive basilic vein pressure), and 17% (7%-34%, non-invasive jugular vein pressure).

CONCLUSION

Ultrasound-based, non-invasive measurement of venous pressure provides a relatively easy method rapid estimation of changes in CVP, although absolute values may differ substantially from invasive CVP and between different investigators.

Low inferior vena caval catheters for hemodynamic and pulmonary function monitoring in pediatric critical care patients

OBJECTIVE

To assess the value of low inferior vena caval (LIVC) catheters for estimating central venous pressure in pediatric intensive care patients and to assess influences of intra-abdominal pressures and mean airway pressure on these measurements.

DESIGN

Prospective cohort of consecutive patients.

SETTING

Pediatric intensive care unit.

PATIENTS

Thirty patients ranging in age (18, 0-1 yrs; four, 1-3 yrs; four, 3-10 yrs; four, > or =10 yrs).

INTERVENTIONS

Interventions included catheterizations via internal jugular, subclavian, and common femoral veins, as well as direct right atrial catheterization during surgery; arterial catheter placement; airway pressure monitoring during mechanical ventilation; indirect intra-abdominal pressure monitoring via bladder catheter pressure readings; and arterial and central venous blood gas analysis. LIVC vein catheters were placed below the origin of the renal veins.

MEASUREMENTS AND MAIN RESULTS

LIVC pressure was highly correlated with central venous pressure (n=30, r2=.965, p=.0001). LIVC pressure did not correlate with intra-abdominal pressure (n=18, r2=.000). Mean airway pressure did not correlate with central venous pressure (n=11, r2=.106). The pH of LIVC blood was similar to that of central venous blood (n=18, r2=.941, p=.0001). PCO2 values of inferior vena cava and central venous blood correlated (r2=.945, p=.0001). However, agreement between inferior vena cava and central venous PO2 and oxyhemoglobin saturation was poor (PO2, r2=.066; oxyhemoglobin saturation, r2=.000).

CONCLUSIONS

LIVC catheters whose tips lie below the origin of the renal veins predict central venous pressure in pediatric intensive care unit patients. Intra-abdominal pressure and mean airway pressure do not affect this relationship, within the wide range of values for these variables included in this study. Blood samples drawn from femoral venous catheters can be used to monitor acid-base balance and partial pressure of carbon dioxide.

Ductus venosus blood velocity in persistent pulmonary hypertension of the newborn

AIMS

To investigate the ductus venosus flow velocity (DVFV) in infants with persistent pulmonary hypertension of the newborn (PPHN); to evaluate the DVFV pattern as a possible diagnostic supplement in neonates with PPHN and other conditions with increased right atrial pressure.

METHODS

DVFV was studied in 16 neonates with PPHN on days 1-4 of postnatal life using Doppler echocardiography. DVFV was compared with that in mechanically ventilated neonates with increased intrathoracic pressure, but without signs of PPHN (n=11); with neonates with congenital heart defects resulting in right atrial pressure (n=6); and with preterm neonates without PPHN (n=46); and healthy term neonates (n=50).

RESULTS

Infants with PPHN and congenital heart defects with increased right atrial pressure were regularly associated with an increased pulsatile pattern and a reversed flow velocity in ductus venosus during atrial contraction. A few short instances of reversed velocity were also noted in normal neonates before the circulation had settled during the first day after birth.

CONCLUSIONS

A reversed velocity in the ductus venosus during atrial contraction at this time signifies that central venous pressure exceeds portal pressure. This negative velocity deflection is easily recognised during Doppler examination and can be recommended for diagnosing increased right atrial pressure and PPHN.