In assessing critically ill patients, an accurate assessment of a patient's volume status and whether they will respond to a fluid challenge with an increase in cardiac output is vital. 1 When hypovolemia is detected, volume expansion is utilized to enhance hemodynamics and restore normal blood pressure. 2 Hemodynamic tests (right atrial pressure, pulmonary artery occlusion pressure, and cardiac output ) are used to assess preload in critically ill patients, although these indexes are not necessarily reliable predictors of fluid status. According to the Starling law, fluid administration is hypothesized to boost cardiac output by raising preload, which describes a positive relationship between cardiac muscle fiber length and contractility. However, the Starling curve hits a plateau beyond its ascending leg, and additional fluid administration can be hazardous, leading to right ventricular overload and pulmonary edema Invasive or noninvasive techniques can be used to determine blood volume status. Assessments such as central venous pressure (CVP) and mean pulmonary artery pressure (mPAP) are both invasive procedures. Various factors influence CVP (including thoracic, pericardial, abdominal pressures, etc.). CVP can be used as a fluid management indication, although It can be misused to estimate blood volume or mislead methods for treatment. Dynamic indices such as stroke volume variation (SVV) and pulse pressure variation (PPV) are superior to static indices for assessing volume status. However, these dynamic indices are unreliable when a patient is ventilated with low tidal volume, such as acute respiratory distress syndrome (ARDS); the tidal volume is insufficient to change intrathoracic pressure significantly. Ultrasound (US) evaluation of the inferior vena cava (IVC) may help determine fluid status.

The study will be conducted in intensive care units of Fayoum University Hospitals after approval of the local institutional ethics committee, and the local institutional review board will approve the study. The inclusion criteria will be as follows: patients on mechanical ventilation(MV), aged between 18 and 60 years with circulatory failure defined as mean arterial pressure (MAP) less than 65 mmHg or systolic arterial pressure less than 90mm Hg with signs of hypoperfusion (urinary flow < 0.5mL/kg/ min for > 2hr, tachycardia > 100 beats/min, or presence of skin mottling, and serum lactate more than 2 mmol/L) 17 and showing positive PLRT. The exclusion criteria: cardiac arrhythmias, previously known significant valvular disease or intracardiac shunt, air leakage through chest drains, increasing intraabdominal pressure, norepinephrine infusion as it decreases PPV and SVV, masking their ability for the detection of FR15

, peripheral vascular diseases, ARDS patients due to low tidal volume a, Contraindication for fluid administration as cardiogenic shock, acute pulmonary edema or LVEF% less than 50%. , renal patients with oliguria and volume overload including patients on hemodialysis or patients with acute anuric renal failure., patients with lower extremity artery/vein thrombosis, significant lower extremity artery plaque, lower extremity artery occlusion, inferior vena cava filter implantation, lower extremity varicose veins,

All patients fulfilling criteria will be monitored by (1) 6 leads ECG, (2) noninvasive BP, (3)urinary catheter for UOP, (4) pulse oximeter then divided into 2 groups, group (P) PPV guided group and group (F) FVD/FAD ratio guided

Randomization of patients to each of the treatment groups will be done by a statistician not involved in the study, using the website randomization.com. The allocation concealment will be done by contacting the statistician giving him the patient number, age, and sex to receive the patient allocation in a sealed envelop.

The envelope is to be received and opened after the informed consent is obtained Neither the participants, the study investigator, the attending clinicians, nor the data collector will be aware of groups allocation till the study end. The Consolidated Standards of Reporting Trials (CONSORT)recommendation will be followed. Group (P):(n=30), patients will be temporarily sedated and paralyzed and on fully controlled mechanical ventilation. No spontaneous breathing effort will be detected on the mechanical ventilator waveform monitor, ensuring that the respiratory changes in arterial pressure reflect only the effects of positive pressure ventilation. Modes of ventilation are selected to volume or pressure-controlled ventilation, depending on the decision of the primary physicians. A tidal volume will be set to not less than 8 ml/ kg (predicted body weight). The preset respiratory rate will be set at 14 breaths/min. Positive end-expiratory pressure (PEEP) will be between 8 and 10 cmH2O. The plateau pressure was kept at below 30 cmH2O. In all patients, radial artery cannulation will be done for invasive blood pressure monitoring (using a 20 G cannula), PPV is calculated directly on Nihon Kohden monitors at the base line then infusion of 4ml/kg /h of crystalloids will be infused till PPV will be less than 13%. 15

Group(F) : (n=30), FVD/FAD ratio guided; US probe will be used first to find the bifurcation position of the femoral artery, and then the probe will be retracted proximally. The visual field of the bifurcation will disappear until the probe enters the main branch of the femoral artery, and the femoral artery and vein could be observed simultaneously. Under normal conditions, pulsation indicates the femoral artery, and its companion is the femoral vein. The mean FVD and FAD will be measured then the FVD / FAD ratio will be calculated.

Inclusion Criteria:

• patients on mechanical ventilation

Exclusion Criteria:

• cardiac arrhythmias
• previously known significant valvular disease or intracardiac shunt
• air leakage through chest drains
• increasing intraabdominal pressure
• norepinephrine infusion as it decreases PPV and SVV
• peripheral vascular diseases
• ARDS

No plan to share data