Practical Prescription and Monitoring in Critical Patients

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The 4 "D" of Fluid Therapeutics

💊 Drug (The Drug-Solution)

Select the crystalloid or colloid solution of choice according to the molecular physicochemical needs of each patient. Avoid the routine and unjustified prescription of 0.9% Physiological Saline Solution in states of primary tissue acidosis.

⚖ Dose (The Dose / Speed)

Establish the exact net volume to be infused, calculating the optimal administration rate in milliliters per hour according to the patient's baseline hemodynamic status and baseline parameters.

⏳ Duration

Define the time limits for suspending active therapy, monitoring the resolution of shock or the achievement of cellular stabilization to avoid tissue volume overload.

🔄 De-escalation (The De-escalation)

Actively remove accumulated extracellular volume overloads, promoting negative water balance through diuretics or ultrafiltration once vascular stability is restored.

The Four Phases Conceptual Approach (ROSE Model)

Fluid management in patients in septic or critical shock evolves dynamically throughout four different temporal stages:

Phase R (Resuscitation)

• Clinical objective: Save the patient's life by immediately correcting extreme arterial hypotension and refractory circulatory shock.
• Fluid therapy: Rapid bolus administration of balanced isotonic crystalloids (30 mL/kg of weight in the first 3 hours of evolution).
• Balance sheet status: Strongly positive on purpose.

Phase O (Optimization)

• Clinical objective: Stabilize cell perfusion, closely monitoring that overload does not compromise tissue oxygenation.
• Fluid therapy: Rigorous evaluation of volume response using dynamic parameters, minimizing the use of blind continuous basal infusions.
• Balance sheet status: Moderate positive controlled.

Phase S (Stabilization)

• Clinical objective: Maintain tissue homeostasis and perfusion of vital organs upon remission of the acute phase of shock.
• Fluid therapy: Exclusive contribution to cover basal requirements for insensible losses and ongoing diuresis, providing minimal basal electrolytes.
• Balance sheet status: Neutral or stable maintenance.

Phase E (Evacuation - Evacuation)

• Clinical objective: Promote active de-escalation and removal of excess body water accumulated in the interstitium during the resuscitation phases.
• Fluid therapy: Targeted use of loop diuretics (furosemide in continuous infusion) or renal clearance support with targeted negative balance.
• Balance status: Strongly negative, reducing damage due to pulmonary and visceral interstitial edema.

Evaluation of Response to Fluids: Dynamic vs. Static Indices

It is a clinical error in contemporary practice to guide fluid administration based exclusively on traditional static parameters such as Central Venous Pressure (CVP) or pulmonary artery occlusion pressure. These values ​​only measure atrial or ventricular filling pressures and do not predict in any way whether a ventricle is capable of increasing its ejection cardiac output in the face of an additional volume load.

The use of dynamic volume response parameters based on the cardiopulmonary physiological interactions of positive pressure mechanical ventilation should be prioritized:

• Pulse Pressure Variation (PPV) or Stroke Volume Variation (SVV): A value of PPV > 12% or SVV > 10% in a patient under controlled mechanical ventilation, in sinus rhythm, with tidal volume 8 mL/kg of weight, predicts with high diagnostic sensitivity an increase in cardiac output after the infusion of a volume bolus.
• Passive Leg Raise Test (PLR): Reversible dynamic maneuver that simulates an immediate internal autotransfusion of approximately 300 mL of blood from the venous territory of the lower extremities to the right atrium. If measurement by transthoracic echocardiography or pulse contour reveals an increase in systolic ejection volume > 10% during the maneuver, the patient is classified as a fluid responder, allowing volume to be prescribed with minimal risk of irreversible iatrogenic overload.