Article, Emergency Medicine

Estimation of central venous pressure using inferior vena caval pressure from a femoral endovascular cooling catheter

Unlabelled imageAmerican Journal of Emergency Medicine (2013) 31, 240-243

Brief Report

Estimation of central venous pressure using inferior vena caval pressure from a femoral endovascular cooling catheter?

Byung Kook Lee MD, PhD, Hyoung Youn Lee MD, Kyung Woon Jeung MD, PhD?, Yong Hun Jung MD, Geo Sung Lee MD

Department of Emergency Medicine, Chonnam National University Hospital, 501757, Gwangju, Republic of Korea

Received 11 June 2012; revised 28 June 2012; accepted 30 June 2012

Abstract

Purpose: Endovascular cooling using the femoral cooling catheter is widely practiced. central venous pressure monitoring in patients undergoing femoral endovascular cooling may require the placement of another catheter near the right atrium (RA). We sought to estimate the agreement between the CVP recorded from catheters placed in the superior vena caval pressure (SVCP) and the inferior vena caval pressure (IVCP) recorded from the femoral cooling catheter in patients undergoing femoral endovascular cooling.

Methods: We enrolled adult cardiac arrest survivors undergoing femoral endovascular cooling. A commercially available central venous catheter was placed in the SVC (superior vena cava) near the RA via subclavian venous access. Both SVCP and IVCP were recorded every 4 hours during therapeutic hypothermia. Arterial pressure, heart rate, peak inspiratory pressure (PIP), and positive end expiratory pressure (PEEP) at the time of vena caval Pressure measurements were obtained.

Results: A total of 323 pairs of SVCP and IVCP measurements were collected. The correlation coefficient between SVCP and IVCP was 0.965 (P b .001). The mean difference between SVCP and IVCP was -0.45 mm Hg (SD, 1.27; 95% confidence interval, -0.59 to -0.31 mm Hg). The limits of agreement were -2.94 to 2.05 mm Hg. Vena caval pressures were significantly correlated with airway pressures (peak inspiratory pressure and positive end expiratory pressure), whereas the difference between SVCP and IVCP did not correlate with airway pressures.

Conclusion: Inferior vena caval pressure measured via the femoral cooling catheter showed excellent agreement with CVP recorded from catheters placed in the SVC, which indicates that the femoral cooling catheter can be used for monitoring CVP.

(C) 2013

Introduction

? Funding sources/disclosures: The authors have no relevant financial information or potential confticts of interest to disclose.

* Corresponding author. Tel.: +82 62 220 6809; fax: +82 62 228 7417.

E-mail address: [email protected] (K.W. Jeung).

Postcardiac arrest patients frequently require the moni- toring of central venous pressure (CVP) for hemodynamic optimization [1]. The measurement of CVP requires a catheter to be placed in the vena cava near the right atrium (RA), which is usually inserted through the internal jugular

0735-6757/$ – see front matter (C) 2013 http://dx.doi.org/10.1016/j.ajem.2012.06.034

CVP monitoring during femoral endovascular cooling 241

vein or subclavian vein. Therapeutic hypothermia has become a standard treatment for comatose cardiac arrest survivors [2]. Endovascular cooling using a femoral endovascular cooling catheter is widely used because of the highly reliable maintenance of core temperature and the relatively rapid Cooling rates [3,4]. Central venous pressure monitoring in patients undergoing femoral endovascular cooling may require the placement of another catheter near the RA because the tip of the currently available femoral endovascular cooling catheter resides in the abdominal inferior vena cava. Several previous studies have shown a high correlation between the abdominal inferior vena caval pressure (IVCP) and the CVP measured in the superior vena caval pressure (SVCP) in severely ill patients [5-7]. However, to our knowledge, there is no study examining the accuracy of IVCP relative to SVCP in patients undergoing femoral endovascular cooling. Postcardiac arrest patients usually require mechanical ventilation during TH and show variable hemodynamic features from intravascular volume overload to Volume depletion because of the precipitating cause of arrest or the ischemic- reperfusion response.

The aim of this study was to estimate the agreement between the CVP recorded from catheters placed in the superior vena cava through the subclavian vein, which is a common practice for CVP measurement, and the IVCP recorded from the femoral endovascular cooling catheter in comatose cardiac arrest survivors treated with femoral endovascular cooling.

Methods

Study design, population, and setting

Our prospective study was conducted in the intensive care unit of the hospital. After receiving approval by the institutional review board and the consent of the next of kin, we enrolled cardiac arrest survivors older than 18 years old who were undergoing endovascular cooling using the femoral endovascular cooling catheter (Icy catheter, 9.3F, 38-cm-long catheter; Zoll circulation, Sunnyvale, CA) via femoral venous access. The femoral endovascular cooling catheter was inserted to a length of 38 cm in all patients. Directly after the placement of the femoral endovascular cooling catheter, a commercially available central venous catheter (7F, 20-cm-long catheter; Arrow International, Reading, PA) was placed in the superior vena cava near the RA via subclavian venous access. After the insertion of both catheters, radiography was performed to confirm the appropriate location of the catheters. The SVCP and IVCP were measured by using the same pressure transducer (ICU medical, San Clemente, CA), which was fixed at the junction of the midaxillary line and fourth intercostal space and connected to both catheters with a 3-way stopcock.

The SVCP and IVCP were recorded every 4 hours during the TH. At least 6 pairs of data were collected from each patient. Measurements were obtained with the patient supine at the end of expiration during positive pressure ventilation and were taken in rapid succession. Each measurement was taken after a zero pressure calibration. Arterial pressure, heart rate, peak inspiratory pressure (PIP), and positive end expiratory pressure (PEEP) at the time of the vena caval pressure measurements were collected. Arterial pressure, SVCP, IVCP, and heart rate were obtained using an Eagle 4000 patient monitor (Marquette medical system, Milwaukee, WI). The patient monitor was set to display a beat-to-beat record of the patient’s Blood pressure and heart rate averaging 8 beats. Analysis of vena caval pressure measurement required a minimum of 3 heartbeats. Peak inspiratory pressure and PEEP were obtained from a conventional mechanical ventilator (840 Ventilator System, Nellcor Puritan Bennett, Inc, Pleasanton, CA).

Data analysis

A previous study showed that the mean difference between IVCP and right atrial pressure was 0.23 mm Hg with an SD of 1.27 mm Hg [6]. Based on these findings, this study was designed to have at least 130 pairs of measurements (involving at least 22 patients) with a sample size calculated to detect differences at the 5% significance level and with a statistical power of 80%. The categorical data were presented as absolute numbers and percentages. Continuous variables were presented as the mean (SD) or median (interquartile range), as appropriate. The correlation between nonnormally distrib- uted measurements was calculated by examining Spear- man correlation coefficient. Bias with a 95% confidence interval (CI) and 95% limits of agreement between SVCP and IVCP were determined by using the method of Bland and Altman [8]. Data were analyzed using PASW/SPSS software, version 18 (IBM, Inc, Chicago, IL). Significance was set at P b .05.

Results

A total of 323 pairs of SVCP and IVCP measurements were collected from 22 patients. The tips of the femoral endovascular cooling catheters were positioned within inferior vena cava at the level between 11th thoracic vertebra and first lumbar vertebra. The demographic and clinical characteristics of the patients are presented in Table 1. Both SVCP and IVCP ranged from 0 to 35 mm Hg. spearman correlation coefficient between SVCP and IVCP was 0.965 (P b .001). The mean difference between SVCP and IVCP was -0.45 mm Hg (SD, 1.27; 95% CI, of -0.59 to -0.31

mm Hg). The limits of agreement were -2.94 to 2.05 mm Hg

242 B.K. Lee et al.

Table 1 Demographic and clinical characteristics of patients

Table 2 The correlation coefficient between airway pressures and vena caval pressures

PIP

P

PEEP

P

SVCP

0.544

b.001

0.434

b.001

IVCP

0.546

b.001

0.424

b.001

Difference between

-0.075

.179

0.061

.276

SVCP and IVCP

(Fig.). Vena caval pressures (SVCP and IVCP) were significantly correlated with airway pressures (PIP and PEEP), whereas the difference between SVCP and IVCP did not correlate with airway pressures (Table 2).

Variables

Age (y), mean (SD) 52.7 (17.4)

Sex

Male 14 (63.6)

Female 8 (36.4)

Height (cm), mean (SD) 166.1 (8.3)

Weight (kg), mean (SD) 64.1 (13.0)

Systolic blood pressure (mmHg), 113.0 (101.0-136.0) median (IQR)

Diastolic blood pressure (mmHg), 67.0 (58.0-93.0) median (IQR)

Heart rate per min, median (IQR) 69 (57-89)

SVCP (mmHg), median (IQR) 11.0 (8.0-15.0)

IVCP (mmHg), median (IQR) 11.0 (8.0-15.0)

IQR indicates interquartile range.

Discussion

This prospective study demonstrated a strong correlation between SVCP and IVCP. The mean difference between the 2 measurements in this study was only -0.45 mm Hg. Thus, the present study indicates that the IVCP measurement can be used instead of the SVCP measurement, eliminating the need for additional central venous catheterization via the subclavian vein or internal jugular vein in postcardiac arrest patients undergoing femoral endovascular cooling.

There have been several previous studies showing results consistent with this study [5,6,9]. In a study by Nahum et al [5], abdominal IVCP accurately reftected the pressure in the RA in children aged 6 months to 14 years. Dillon et al [9]

image of Fig.

Fig. Bland-Altman plot of the differences between SVCP and IVCP against their average.

reported that there was excellent agreement between SVCP and femoroiliac venous pressure in ventilated adult patients. The IVCP is expected to reftect SVCP more accurately if the IVCP is measured at a point nearest to the RA as possible. In a study by Walsh et al [6], which compared right atrial pressure with venous pressures in the superior vena cava, inferior vena cava, and femoral vein in 60 patients undergoing femoral vein catheterization, the mean differences between right atrial pressure and venous pressure and the limits of agreement were largest in the femoral vein and smallest in the superior vena cava. Thus, IVCP recorded from the femoral endovascular cooling catheter is likely to provide a more accurate estimate of SVCP than the venous pressure recorded from the commonly used 20-cm-long central venous catheter placed in the femoroiliac vein. In a study by Joynt et al [7], which compared SVCP with IVCP recorded from catheters placed in the inferior vena cava close to the RA under electrocardiographic guidance, a mean difference between SVCP and IVCP was 0.45 mm Hg (SD, 0.89; 95% CI, 0.30-

0.60 mm Hg). The mean difference determined in the present study was very similar to the value reported by Joynt et al [7]. Our study differs from the previous studies in that we enrolled postcardiac arrest patients undergoing femoral endovascular cooling. The range of CVP in this study, which was 0 to 35 mm Hg, was wider than the range of CVP in the previous studies [6,10]. The wider range of CVP in this study may reftect the hemodynamic variability of postcardiac arrest patients. Cooling also induces hemodynamic changes via an increase in systemic vascular resistance, a decrease in heart rate, and cold-induced dieresis [11]. In this study, despite the wide range of CVP, IVCP estimated SVCP accurately.

Comatose cardiac arrest survivors usually require me- chanical ventilation during TH. In this study, both SVCP and IVCP increased similarly with an increase in airway pressures, whereas the difference between SVCP and IVCP did not correlate with airway pressures. Consistent with this study, Ho et al [12] demonstrated that airway pressures had no effect on the difference between SVCP and common iliac venous pressure. The present study, with the previous studies examining IVCP in Mechanically ventilated patients, in- dicates that agreement between SVCP and IVCP will be maintained regardless of the use of positive pressure ventilation because airway pressures affect the 2 vena caval pressures similarly.

CVP monitoring during femoral endovascular cooling

Conclusions

This prospective study demonstrated a strong correlation between SVCP and IVCP in comatose cardiac arrest survivors undergoing femoral endovascular cooling. Con- sidering the potential complications of central venous catheterization, such as pneumothorax, hemothorax, and carotid artery puncture, IVCP measured via the femoral endovascular cooling catheter can substitute for SVCP in patients undergoing femoral endovascular cooling, obviating the need for additional Central venous catheter placement.

References

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  2. Deakin CD, Nolan JP, Soar J, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 4. Adult advanced life support. Resuscitation 2010;81:1305-52.

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