Volume Responsiveness By Ultrasound Of Carotid Blood Flow In Patients With Cardiogenic Shock
Condition: Cardiogenic Shock; Volume Responsiveness; Ultrasound
MeSH terms: Shock, Cardiogenic; Shock
Study type: Observational

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Transthoracic echocardiography and Carotid artery doppler (PHILIPS HD11 XE ultrasound device) before and after PLR test.
Intervention type(s): Other
Intervention description(s): VTI-LVOT was measured by echo by placing the pulsed wave Doppler sample gate in the LVOT diameter in apical-5-chamber window. VTI-LVOT was obtained by manually tracing the Doppler velocity spectrum. LVOT velocity time integral was recorded before and after PLR test within 2 minutes. Carotid blood flow was measured by using two-dimensional image, the optimal image of the long-axis view was obtained at the common carotid artery. The sample volume was placed on the center of the lumen, 2 cm proximal to the bulb, and a pulsed wave Doppler examination,The angle correction cursor was placed parallel to the direction of blood flow. A PLR will be performed in 2 sequential steps, first step patient is seated in the semi recumbent position (45°) then using an automatic bed elevation technique, the lower limbs will be then raised to a 45° angle while the patient's trunk will be lowered in supine position. Thus, the angle between the trunk and the lower limbs will remain unchanged (135°).
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        40 cardiogenic shock patients of both gender admitted to intensive critical care units.

        Approval of the Medical Ethics Committee of Alexandria Faculty of Medicine. An informed
        consent was taken from the patients' next of kin before their enrollment in the study.