Volume Responsiveness By Ultrasound Of Carotid Blood Flow In Patients With Cardiogenic Shock

Resuscitation of critically ill patients has changed since the advent of goal directed therapy. Today, practitioners providing fluid resuscitation are attentive of the danger associated with volume depletion while being aware of the morbidity of volume overload. Fluid resuscitation must be rapid, precise, and individually tailored to each patient based on reliable data obtained by various means inside ICU setting.

There is no non-invasive method that can reliably and accurately identify fluid responsiveness. As such, in patients with undifferentiated shock, treatment often involves empiric fluid administration, in the hopes that volume expansion will increase preload, which will then serve to increase cardiac output (CO). However, for patients on the flat portion of the Starling curve, aggressive fluid administration results in no appreciable increase in CO and may be detrimental to hemodynamically unstable patients.

Study location and population: Alexandria Main University Hospitals ICU, Alexandria Egypt. Approval of the Medical Ethics Committee of Alexandria Faculty of Medicine was obtained before the start of the study. Sample size was estimated using PASS version 20 program. The minimal hypothesized total sample size of 40 cardiogenic shock patients of both sexes is needed to determine the sensitivity and specificity of cardiac output measurement using either bedside ultrasound on carotid artery and TTE (Standard) while assessing volume responsiveness with 95 % confidence level and 80 % power using z-test.

Study procedures: All enrolled patients were subjected on admission to thorough history taking including age, sex, date of ICU admission and preexisting underlying disease (Diabetes Mellitus, hypertension), presence of sepsis, smoking, analgesic abuse. Full clinical examination. Severity of illness was assessed by Acute Physiological And Chronic Health Evaluation-ΙΙ (APACHE ΙΙ). ICU length of stay (LOS) and final outcome were recorded.

Noninvasive measurement of Systolic arterial pressure, diastolic arterial pressure (DAP), mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR), and temperature were recorded upon admission and after PLR.

Fluid challenge: A PLR was performed, Transferring a patient to the passive leg raising (PLR) position (in which the lower limbs are elevated at 45_ while the trunk is lying supine) transfers venous blood from the legs to the intrathoracic compartment and increases cardiac preload around 300-500 mL.

Carotid ultrasonography and Echocardiogram: Stroke volume is the amount of blood ejected from the ventricle with each cardiac cycle. It can be readily calculated by subtracting the end-systolic volume from the end-diastolic volume. Multiplying the stroke volume by the heart rate yields the cardiac output, typically reported in liters per minute.

Stroke volume can be estimated by using a combination of 2D and Doppler imaging. HR was recorded before and after PLR test then CO is calculated by equation of:

CO = π × (LVOTd)2/4 × VTI LVOT × HR Percent change is \[(cardiac output after passive leg raising - cardiac output before passive leg raising)/cardiac output after passive leg raising\] × 100%. A greater than 10% increase in cardiac output would predict volume responsiveness and constitute an indication for a 500-mL fluid bolus. Measurements were repeated as needed, and fluid resuscitation continued until no further response to passive leg raising was noted.

Changes (%) =100 X (post-FC value - baseline value)/ baseline value

Patients were divided into 2 groups:

Responder is defined by an increase of 10% or more. Non responder is less than 10%. The Common Carotid artery is a large superficial accessible artery so carotid doppler flow imaging would be simple, non-invasive method to assess volume responsiveness. Use of Velocity Time Integral of flow through the Common Carotid artery (Carotid VTI) and Passive Leg Raising (PLR) described as a marker of volume responsiveness in hemodynamically unstable patients.

Carotid flow is measured during the passive leg raising maneuver by using a linear array transducer positioned in the long axis over the CCA, after procuring a longitudinal view of the common carotid artery, pulsed Doppler analysis at 2 cm from the bifurcation was performed. The CCA diameter is measured from opposing points of the vessel's intimal wall, with the velocity time integral determined automatically using spectral Doppler envelopes and the sample obtained from the center of the artery. Common carotid artery blood flow per minute is calculated by the equation CBF= π × (CCA diameter)2/4 × CCA velocity time integral × heart rate This parameter is measured both before and after the passive leg raising to determine the percent change in CCA blood flow. An increase in CCA flow with passive leg raising only occurs in patients with shock, and an increase of greater than 20% is highly predictive of volume responsiveness.

HR is recorded before and after PLR then CBF was calculated by the following equation:

CBF = π × (CCA diameter)2/4 × VTI CCA × HR

Patients was divided into 2 groups:

Responder is defined by an increase of 20% or more. Non responder is less than 20%. After fluid challenge we remeasured Systolic arterial pressure, diastolic arterial pressure (DAP), mean arterial pressure (MAP), heart rate (HR) to assess clinical response to the fluid challenge.

Eligibility Criteria:
Inclusion Criteria:

* Age \> 18 Y.
* Cardiogenic shock.

Exclusion Criteria:

* Age \< 18 Y.
* Pregnant females.
* All types of shock state other than cardiogenic.
* Peripheral arterial disease.
* Non consenting patients.
* Unable to tolerate passive leg raise (PLR).
* Common carotid artery stenosis greater than 50 % (systolic peak velocity \>182 cm/s and/or diastolic velocity \>30 cm/s by Doppler ultrasound.