From critical care nephrology to critical care blood purification

Critical care blood purification is inseparable from the guidance of critical care medicine theory

Critical care medicine has developed rapidly in recent years, enabling more and more critically ill patients to receive effective treatment. One of the main reasons that critical care medicine can improve the prognosis of patients is to emphasize the early detection and early intervention of severe diseases, as well as the concept of organ protection, such as early detection and treatment of shock, and lung protection strategies for acute respiratory distress syndrome. In addition, critical care medicine attaches importance to the study of the interaction between organs, such as cardiorenal syndrome, hepatorenal syndrome, and multiple organ dysfunction syndrome. Paying attention to the interaction between organs helps to balance a variety of treatment contradictions in the treatment process, thereby promoting the recovery of organ function and improving the prognosis. This treatment concept has also had a huge impact on CCBP. Taking acute renal failure and renal replacement therapy as examples, in order to achieve early detection and intervention of acute renal failure, the concept of “acute kidney injury” came into being;[2] in order to protect the damaged kidney, the traditional approach of “renal replacement therapy” is gradually replaced by the concepts of “renal support therapy” and “multiple organ support therapy”.[14] Therefore, although the renal support treatment in CCBP is similar to the traditional RRT, there are obvious differences in the treatment indications and timing, as well as the method and dosage.

In addition, the volume adjustment range of critically ill patients is narrowed, and both insufficient volume and fluid overload will affect the prognosis.[15] The progress of critical care medicine in the field of hemodynamics and fluid therapy also has a great impact on the volume management of CCBP. For example, when CRRT is performed on patients with unstable hemodynamics, only goal-directed treatment under the guidance of hemodynamics can achieve accurate and appropriate volume management, thereby improving the prognosis of those patients and their kidneys.[7]

Personnel engaged in critical care blood purification must master the theories and skills of critical care medicine

The fact that CCBP is inseparable from the guidance of critical care medicine theory also determines that the doctors who implement CCBP should have deep critical care medicine theory and skills, especially solid hemodynamic skills, in order to ensure the quality of CCBP. Whether CCBP is led by intensivists or nephrologists depends on the country or hospital. Which of the two forms is better or worse is still controversial.[16, 17, 18, 19] Vincent’s research shows that under the premise of good multidisciplinary consultation, closed ICU formats with intensivist-led care can improve the prognosis of patients with acute renal failure.[16] It shows that CCBP led by intensivists is a main direction for future development. Intensivists should strengthen their own learning and training and master the theory and skills of CCBP. Even for CCBP led by nephrologists, it should be ensured that they are trained in the theories and skills of critical care medicine.

Critical care blood purification takes the internal environment of critically ill patients as the main research object and intervention target

Various internal environmental disorders can occur to critically ill patients. In addition to the volume, electrolyte and acid–base imbalance frequently seen in AKI, severe internal environmental disorders can also be caused by hepatotoxins in liver failure, pathogenic microorganisms, and cytokine storms in severe infections, pathogenic antibodies from autoimmune disease, exogenous drugs or poisons entering the body, hyperthermia caused by heat stroke, and so on.[20, 21]

Using blood purification technology to rebuild homeostasis to maintain a good internal environment for organs and cells throughout the body will help restore organ function and improve prognosis. Traditional blood purification pays attention to the replacement of organ functions, while CCBP pays more attention to the correction of internal environmental disorders caused by various reasons such as organ dysfunction. Taking the internal environment disorder of critically ill patients as the target of CCBP intervention rather than just organ function is helpful to focus on the whole body and correctly determine the intervention timing, method, and dose of CCBP, reflecting the advantages of CCBP’s systemic support.[5]

Critical care blood purification has the characteristics of integration

Due to the complexity and variability of critically ill patients, their internal environmental disorders are also diverse. Therefore, doctors are required to select appropriate blood purification techniques for patients and formulate individualized blood purification programs. Different from the relatively fixed treatment plan of traditional blood purification, CCBP often needs to flexibly select different blood purification techniques according to the changes of the patient’s condition, showing the characteristic of integration. We divide the integration of CCBP into synchronous integration and sequential integration. Synchronous integration refers to the use of Integrated Blood Purification Technique (IBPT, that is, different blood purification principles or methods are integrated in the one composite technique) to treat critically ill patients, such as the use of Molecular Adsorption Recirculation System (MARS) to treat liver failure. Sequential integration refers to the use of different blood purification techniques one after another to treat the same critically ill patient. For example, patients with hepatorenal syndrome are treated with plasma exchange first, followed by CRRT.

In summary, CCBP, as a discipline that intersects with critical care medicine, cannot be developed without the guidance of critical care medicine theory. CCBP takes the internal environment of critically ill patients as the research object and intervention target. Due to the complexity and variability of critically ill patients, it is determined that the way of CCBP is not fixed, and different blood purification techniques need to be flexibly selected, showing a characteristic of integration. At present, the international CCN has made great achievements. With the deepening of CCBP’s other subspecialty research and multidisciplinary cooperation, its concepts and technologies will inevitably be mastered by more clinical medical staff. The extensive and standardized application of CCBP will become another advantageous weapon that can significantly improve the prognosis of critically ill patients after mechanical ventilation.