The aim of the study is to detect wither dobutamine or milrinone have a privilege in the management of low cardiac output pediatric patients over the other.

Randomized controlled trials (RCTs) enrolling critically ill patients with low cardiac output syndrome (LCOS) admitted at pediatrics emergency and intensive care units ,Cairo University Children's Hospital, identified by treating medical team as requiring initiation of inotropic therapy based on healthcare team assessment of :

• Capillary refill time > 3 sec
• Hypotension (less than the 5th percentile or less than 90/50 mmHg for children 10 years or older (Kleinman et al.,2010) (Haque et al .,2007)
• Oliguria (urine output that is less than 1 mL/kg/h in infants, less than 0.5 mL/kg/h in children ) (Nakano et al.,2022)
• Metabolic acidosis with base excess > -2 (Nakano et al.,2020)

Patient randomization will be done by a computer based generation , serial enveloped numbers will be taken for the patients. Cardiac assessment will be done by a blinded pediatric cardiologist. If at any time the randomly assigned therapy considered to be failed or unsafe to continue, the treating physician will discontinue randomization and will continue with the appropriate medication according to the patients need.

Every patient will be evaluated after the first 24 hours of starting the inotropic therapy by :

• pre and post inotropic therapy ICON measurements ( evaluating cardiac index and systemic vascular resistance pre and post inotropic support)
• pre and post inotropic therapy echocardiography ( evaluating systolic and diastolic dysfunction by M-mode and two dimensional methods) through measuring LV EDD cm, LV ESD cm, LV EDV ml, LVESV ml, FS% , LV mass, EF% , MAPSE cm, TAPSE cm.
• pre and post inotropic therapy clinical assessment of vital signs (heart rate , blood pressure, capillary refill time and urine output as mention before)
• The need of titration up of inotropes :

Milrinone will start by 0.25 , 0.5 , 0.75 we can titrate up with time interval 3 hours after re-assessment.

Dobutamine will start by 5, 10 , 15, 20 we can titrate with time interval 15 mins after re-assesment.

-Time to achievement of therapeutic endpoints for hemodynamics

• adequate blood pressure
• clinically adequate cardiac output ( capillary refill time < 2sec , urine output that is more than 1 mL/kg/h in infants, more than 0.5 mL/kg/h in children, full conscious )

Data will be collected for each patient in form of [ Time Frame: Through first 24 hours up to first week since admission ] :

1. Total time on inotropes (in hours)
2. Non-invasive or invasive mechanical ventilation Total number of days requiring non-invasive or invasive mechanical ventilation
3. Change in cardiac index ([CI] measured with ICON
4. Change in systemic vascular resistance [SVR] measured with ICON
5. Presence of acute kidney injury (defined as an increase in serum creatinine or a decrease in urine output or both over hours to days.) (Jacob J et al.,2020)
6. Absence of metabolic acidosis (BE -2 to 2)
7. Arrhythmia requiring medical team intervention, either through electrical or chemical cardioversion or any intravenous anti-arrhythmia medication administration
8. Need for up-titration or addition of new vasopressor therapy

Inclusion Criteria:

• 1-Patients from age of 1 month to 14 years old of both sexes.

  2-Patients presenting with fluid refractory shock with low cardiac output state, evidenced by sustained hypotension (systolic blood pressure below 5th percentile for age) and end organ dysfunction (altered level of consciousness, renal or hepatic dysfunction)

  3-Clinical evidence of systemic and/or pulmonary congestion despite use of vasodilators and/or diuretics

  4-Refractory heart failure requiring admission for inotropic support.

Exclusion Criteria:

1-All other causes of pediatric shock not in need for inotropic support (eg.isolated hypovolemic shock, anaphylaxis,….)

2 - patients not fit for randomization needing specific line of management (eg. Sever hypotension patients with good filling pressure unfit for milrinone , patients previously known having sever pulmonary hypertension not fit for dobutamine ,…)

3-post cardiac surgery patients with low cardiac output manifestation.

. Cardiac assessment will be done by a blinded pediatric cardiologist.