Ultrasound guided measurement of inferior vena cava diameter, common carotid artery diameter versus central venous pressure for estimation of intravascular volume status in critically ill patients.

Introduction

Fluid management in the intensive care plays a vital role in the outcome of the patient. Hypovolemia with inappropriate use of vasopressors to maintain the blood pressure reduces the organ perfusion leading to ischemia. On the other hand fluid overload causes cellular swelling and congestion of lungs thereby increasing morbidity and mortality⁽¹⁾. Central venous catheters have a wide variety of uses such as hemodynamic monitoring, drug administration, total parenteral nutrition, trans-venous pacemaker placement, pulmonary artery catheterization. The central venous pressure is a static measure of volume. The method has been followed widely to assess the volume status and thereby treating the patient accordingly. Insertion of central venous catheter is contraindicated in certain situation as any coagulation disorders, infection over the insertion site⁽²⁾.      

Recently the ultrasound, guided measurement of the IVC diameter and Common carotid artery diameter can be used as an alternative to central venous catheterization to assess the volume status of patients. It is a dynamic measure of intravascular volume status⁽³⁾. The IVC adjusts to the body's volume status by changing its diameter depending on the total body fluid volume. The caval opening increases in size during inspiration, which encourages venous return of blood to the heart through the IVC due to the negative intrathoracic pressure. This results in the collapse of the IVC. During expiration the reverse happens, where due to the positive intra-thoracic pressure the pressure gradient decreases causing a distension of the IVC⁽⁴⁾. Bedside ultrasonography is readily available in intensive care setups. It is safe, cheap and non- invasive. Ultrasound of inferior vena cava (IVC) is a tool that can provide a rapid and non-invasive means of gauging preload and the need for fluid resuscitation⁽⁵⁾. Also studies reported that the diameter of the CCA respond to intravascular volume expansion with significant dilation.

Aim of the work

The aim of this study is to know the effect of fluid administration on the diameters of IVC and Common carotid artery in prediction of volume status in critically ill patients and to know the correlation between Inferior vena cava and Common carotid artery diameters Versus Central venous pressure.

 Patients and Methods

This prospective observational  study was conducted in El-Minia University Hospital during the period from March 2021 to August 2022 after obtaining approval of the university ethical committee (approval number.133:2021) and written informed consent from all Patients or first degree relatives. We studied 55 patients their ages group ranged between 20 and 60 years, of both genders; males and females, who admitted to our surgical Intensive care unit (SICU) from the American Society of Anesthesiology (ASA) physical status II and III who were able to breathe spontaneously, lie supine and had central venous catheter (CVC) who required close monitoring and assessment of intravascular volume status.

 Results

A total of 29 patients were male (52%) and 26 were female (47.3%) with a mean age of 43.3±13.1 years. There was 40 patients ASA II and 15 patients was ASA III. The patients had been under follow up most commonly with the diagnosis of sepsis (33 patients, 60%), blood loss (22 patients, 40%). About 21.8% of patients received norepinephrine while 14.5% received norepinephrine plus epinephrine is summarized in table 1.

Changes in mean arterial blood pressure and heart rate are illustrated in table 2. The mean value of MAP was increased significantly at 30 min, 1hr, 2hrs, 3hrs, 6hrs, 12hrs, 24hrs, and 48hrs as compared to base line value but insignificant at 30min. The mean value of HR was decreased significantly at 30 min, 1hr, 2hrs, 3hrs, 6hrs, 12hrs, 24hrs, 48hrs as compared to base line value.

Changes in Ultrasound parameters and CVP are presented in table 3 The mean values of inferior vena cava maximum (IVC max) and Inferior vena cava minimum (IVC min) diameters were  increased significantly at 1hr,  2hrs, 3hrs, 6hrs, 12hrs, 24hrs, 48hrs as compared to base line value except at 30min. The mean value of Inferior vena cava collapsibility index (IVC CI) was decreased significantly at 30 min, 2hrs, 6hrs, 12hrs, 24hrs, and 48hrs as compared to base line value. The baseline value of CCA was 2.9±0.4mm and this value increased significantly at all times till it reached to 5.1±0.7mm after fluid administration. Serial CVP monitored at all times showed a gradual significant increase from baseline value of 2±0.8 cm H2O to 11.2±2.4 cm H2O except at 30min.

 Person’s correlation was applied between CVP and U/S parameters. CVP showed positive correlation with IVC max, IVC min diameters and with CCA diameter, whereas a negative correlation to IVC CI as seen in table (4). CVP had a significant relation with U/S parameters as shown in table 5.

Analysis of Roc curve shows a better diagnostic accuracy of IVC max diameter than IVC CI for predicting low CVP< 8 cmH2O with  a cut-off value ≤ 1.38 cm, with a sensitivity 90.48% and specificity 91.82%, positive predictive value (PPV) 95.9%, negative predictive value (NPV) 82%, accuracy 90.91%, AUC (0.965). While for IVC CI at cut-off value> 10.3, the sensitivity 69.35%, specificity 57.23%, PPV 77.4 % and  NPV  46.9%, accuracy 65.5% and AUC was 0.682. and for  IVC min diameter at cut-off value ≤ 1.25 the sensitivity, specificity, PPV, NPV,  accuracy and AUC were 92.26%,  82.39%,  91.7%, 83.4%, 89.1%, 0.955.  for CCA diameter has Cut- off value ≤ 4.4 mm with sensitivity 93.15%, specificity 71.7 %, PPV 87.4%, NPV 83.2%, accuracy 86.3% and AUC was 0.937 as shown in table (6).

Discussion

In the current study, there was positive correlation between CVP and IVC max, IVC min diameters,  whereas a negative correlation to IVC CI. In agreement with our result, Deepak Raj Singh et al., 2021 who revealed positive correlation between CVP and VC diameters and negative correlation with IVC CI ^(6).

In collaboration with our results, Mahrous et al., 2022 who discovered a statistically significant relationship between IVC diameter and CVP. This indicated that a rise in CVP is followed by a reduction in CVI-CI⁽⁵⁾ .

The current study shows a better diagnostic accuracy of IVC max diameter than IVC CI for predicting low CVP< 8 cmH₂O with a cut-off value ≤1.38 cm a sensitivity of  90.48%, specificity of 91.82%, and accuracy of  90.91%, but there was a negative correlation with IVC CI, where IVC CI > 10.3%  can predict low CVP<8 cm H₂O with a sensitivity of  69.35%, specificity of 57.23% and accuracy of 65.5%.

Our results agree with the outcome of Prekker et al., 2013 who found that the area under the curve to discriminate low central venous pressure (< 10 mm Hg) was 0.91 for inferior vena cava diameter, which was significantly higher than the IVC CI 0.66. An inferior vena cava diameter <2 cm predicted a central venous pressure < 10 mmHg with a sensitivity of 85%, specificity of 81% ^(7).

Our findings correlate with Bahman Naghipour and Gholamreza Faridaalaee 2016, who evaluated the correlation of sonographic IVC diameter, aorta diameter, and IVC / aorta ratio with CVP. 39 patients were included (53.8% male; mean age 62.1±5.8 years, Patients in need of catheterization and TEE who were referred  to a teaching hospital in Tabriz, Iran, from 2013 to 2015 were enrolled. At this study CVP had a significant c orrelation with IVC diameter at the point of entry into the right atrium (r =0.85) ⁽⁸⁾

In contrast to our study, Shalaby et al., 2018, who found a better diagnostic accuracy of IVC CI (AUC 0.871, p <0.001) than IVC dmax, for predicting baseline low CVP< 10 cmH2O, where IVC CI >33.33% can predict low CVP with a sensitivity of 76.0% and a specificity of 92.0% ^(9).

In this study we found that the mean of the CCA diameter on admission was 3.2±2.6 and significantly increased all over 48hrs after fluid administration till it reached to 5.1±0.7. In accordance to our study Samaa et al., 2020 who found that the mean diastolic CCA diameter was 5.4± 0.6 (mm) on admission and significantly increased from 5.5 ± 0.7 to 6.6 ± 0.5(mm) after fluid administration (P < 0.001) ^(10).

Our findings go hand to hand with  Hilbert et al., 2016 who conducted a study at cardiac surgery intensive care unit of the University Hospital Bonn, Germany, the diameter of the CCA measured using bedside ultrasound responds to intravenous fluid expansion with significant dilation^(11).

In collaboration with our results Marik et al., 2013 who conducted a study during an 8-month period, collected clinical, hemodynamic, and carotid Doppler data on hemodynamically unstable patients in the ICU who underwent a PLR maneuver as part of our resuscitation protocol. We noted a significant increase in the diameter of the common carotid artery in the fluid responders ^(12).