Four D concept of fluid therapy
Authors: Mulbrain M. 
Published: July 2021

Background. D (definition): the daily fluid balance is the sum of all the amounts of consumed and excreted fluid. Assessment of fluid accumulation per day allows to detect fluid overload. At early stages (the first 1-3 hours) of infusion therapy (IT) targeted administration of necessary drugs should be carried out. The volume of infusion is 10-30 ml/kg of body weight. Subsequently, during the first week of treatment in the intensive care unit (ICU) it is necessary to achieve two consecutive days with a negative fluid balance. In the later stages of treatment, active fluid removal is performed with diuretics or renal replacement therapy. The concept of four D IT actually includes seven D: definitions, diagnosis, drug, dose, duration, de-escalation, discharge.
Objective. To describe the basic principles of modern IT.
Materials and methods. Analysis of literature sources on this topic.
Results and discussion. The improvement and proper application of the existing IT techniques and drugs is an important step in improving treatment outcomes. Frequent mistakes include too long IT, wrong choice of drug or dose. Hypervolemia as a result of excessive infusions is even more dangerous than hypovolemia because it can lead to the interstitial edema. To address the issue of IT, it is advisable to focus on preload – the degree of stretching of a cardiomyocyte before contraction. Echocardiographic indicators of preload include end-diastolic volume and end-diastolic pressure of left ventricle. When choosing a solution for IT, it is necessary to take into account its tonicity and osmolality, as it depends on whether the solution will remain in the vessels or enter the intercellular space. Choosing an optimal IT, one should take into account the choice of solution or combination of solutions, the optimal time and duration of its introduction, the pathological condition of the patient. Thus, in case of trauma, blood and crystalloids are prescribed, in case of sepsis – crystalloids, and later albumin, in the perioperative period – hydroxyethyl starch (HES) and crystalloids. When choosing an antibiotic for IT, you should pay attention to the recent history of hospitalizations, length of stay in a medical institution (term >5 days increases the likelihood that the patient’s infection is nosocomial), comorbid conditions, history of steroid use, previous antibiotic therapy (ABT), duration of mechanical lung ventilation. Dose is another important aspect of IT. In ABT, too high dose can be toxic to the macroorganism, and too low dose can be ineffective and cause bacterial resistance. When selecting the dose of the antibiotic, attention should be paid to the distribution volume of the drug, the liver and kidney function and the peculiarities of the drug clearance, albumin level, ability to penetrate into tissues, minimal inhibitory concentration. In turn, when selecting the dose of solutions for IT, it is necessary to take into account the volume of distribution, type of solution, osmolality, tonicity, and the condition of renal function. In most cases, the maintenance volume of solutions is 1 ml/kg/h (25 ml/kg/day), and the volume required for resuscitation is 30 ml/kg in the first 3 hours, the fluid bolus is 4 ml/kg / 15 min. Some fluids (HES) are toxic for the kidneys (maximum dose is 30 ml/kg/h). However, lack of control over shock is also not beneficial for the kidneys, so the benefit/risk balance should always be assessed. Static surrogate parameters of preload (central venous pressure, average arterial pressure, urine volume, volumetric indicators) are often used for IT titration. However, it is more appropriate to use dynamic functional parameters of hemodynamics: pulse pressure variations, stroke volume variations, passive leg raise test. The duration of optimal IT has not yet been established, although there is evidence of a downward trend. After eliminating shock and normalizing blood lactate, it is advisable to stop IT. It is advisable to reduce the duration of ABT to a minimum and to remember that the goal is to treat the infection, not to treat fever, infiltrates or elevated C-reactive protein. Therefore, ABT should be discontinued when the signs and symptoms of active infection disappear. In future, biomarkers (procalcitonin or cystatin C, citrulline, respectively) will be used to determine the need to discontinue ABT or IT. Timely de-escalation of IT is no less important than its timely start. It is advisable to follow the ROSE concept (R – resuscitation; O – organ support; S – stabilization; E – evacuation).
Conclusions. 1. The concept of four D IT includes definitions, diagnosis, drug, dose, duration, de-escalation, and discharge. 2. For IT titration it is reasonable to use dynamic functional parameters of hemodynamics: pulse pressure and shock volume variation, passive leg raise test. 3. It is advisable to follow the concept of ROSE.