Название: 40 Years of Continuous Renal Replacement Therapy
Автор: Группа авторов
Издательство: Ingram
Жанр: Медицина
Серия: Contributions to Nephrology
isbn: 9783318063073
isbn:
Introduction
Acute kidney injury (AKI) is an important syndrome frequently occurring in intensive care patients with high morbidity and mortality. This clinical entity has required a progressive scientific effort to develop adequate technology for providing safe and reliable treatment. As a consequence, the area of acute renal replacement therapy (RRT) and related technology underwent a significant evolution over the last 4 decades, making critical care nephrology a new emerging subspeciality of intensive care medicine [1, 2]. We briefly describe the pathway of evolution in the area of continuous RRT (CRRT) that has occurred over the last 40 years.
The Era of Continuous Arteriovenous Hemofiltration
Continuous arteriovenous hemofiltration (CAVH) was first proposed in 1977 and immediately became an important alternative treatment for AKI in patients in whom peritoneal dialysis or hemodialysis was clinically or technically precluded [3]. This opened the doors of intensive care units to extracorporeal treatments, which experienced a flourishing evolution in subsequent years. In the mid-1980s, the technology of CAVH was extended to infants and children, and newly designed hemofilters permitted the application of the technique even to newborns [4]. CAVH presented important advantages over intermittent hemodialysis, such as hemodynamic stability with slow continuous volume and solute control. Specific filters with reduced flow resistance that were adequate to operate in an arteriovenous modality were designed to improve performance. In spite of technological ameliorations in the filter and membrane design, CAVH presented limited ultrafiltration and solute clearance as well as risk derived from arterial cannulation.
The Addition of Diffusion and the Birth of Hemodiafiltration
A significant advance was made by designing new filters with 2 ports in the dialysate/filtrate compartment that allowed the circulation of dialysate fluid countercurrent to blood and obtained additional diffusive solute clearance. This modified technique was named continuous arteriovenous hemodiafiltration or hemodialysis, respectively [5]. With the arrival of continuous arteriovenous hemodialysis and continuous arteriovenous hemodiafiltration, uremic control became easier in patients irrespective of their weight or catabolic state simply by increasing countercurrent dialysate flow rates to 1.5 or 2 L/h as necessary.
Ultrafiltration and Fluid Balance Control
Originally, ultrafiltration control was done manually and transmembrane pressure was modified by positioning the ultrafiltrate (UF) collecting bag at different heights in respect to the filter. The replacement solution was delivered using manually regulated clamps. The negative pressure generated by the UF column regulated the final transmembrane pressure. Subsequently, manual systems were, in some cases, substituted by automatic fluid balance systems called Equaline [6]. The systems operated by gravity utilizing 2 load cells for UF and SF measurement, and a smart clamp provided adequate SF flow to achieve the desired fluid balance.
Introduction of Venovenous Pumped Techniques
Arteriovenous therapies were simple because they did not require a peristaltic blood pump, but the morbidity associated with arterial cannulation was substantial. For this reason, venovenous techniques utilizing a double-lumen central venous catheter for vascular access were considered preferable and safe. Thus, within a few years, continuous venovenous hemofiltration or continuous venovenous hemodiafiltration replaced CAVH because of its improved performance and safety. The advance was made possible by the use of blood pumps, calibrated ultrafiltration control systems, and double-lumen venous catheters. These treatment methods were widely utilized at the end of the 1980s and showed excellent uremic control utilizing high blood flows (150 mL/min or more) and large membrane surface areas (0.8 m2 or more). To facilitate nursing care, ultrafiltration was soon controlled by devices with reasonable precision. Thus, for clinical purposes, ultrafiltration and reinfusion could be fully regulated to achieve the desired therapeutic goals. This era was characterized, however, by the adoption of technology from other fields (e.g., such as chronic hemodialysis), and multiple devices (blood pump, UF pump, reinfusion pump, anticoagulation, etc.) were connected to the patient without a systematic assembly and a coherent combined strategy. Although efficiency was highly improved and treatment performance was superior to any previous technique, this approach led to potential errors and treatment failures due to the inability of different devices to communicate and operate together.
From Adoptive Technology to Dedicated Equipment
In the late 1980s, specific machines for CRRT were designed and a new era of RRT in the critically ill patient began [7, 8]. The therapy started to get standardized and clear indications began to be defined. Special requirements from easier institution of CRRT and easier monitoring of treatment led to the development of the first generation of CRRT-integrated machines with several pumps and different technique capabilities. The ‘Prisma’ machine was one of the first integrated CRRT machines designed specifically for acute RRT in intensive care. The preassembled circuit and the autopriming feature made CRRT possible in almost every intensive care unit, with improved safety and performance.
Technological Response to New Demands
After the extracorporeal therapies had become more or less a routine treatment in intensive care, new studies were performed to determine the importance of accurate delivery of therapy and a minimum quantity (dose) of treatment to be provided in CRRT to optimize results and improve outcomes [9]. New requirements in terms of performance and safety were identified, with the result that technology followed the demand for higher efficiency and large exchange volumes in presence of a user-friendly interface. This process led to the development of a new generation of machines with advanced features, higher performance, and an integrated easy-to-use operator interface [10].
Evolution of CRRT Techniques
Different techniques are available today for the therapy of the critically ill patient with renal and other organ dysfunction. An interesting aspect is the definition of an “adequate” dose of dialysis in AKI and the potential of different therapies for the treatment of sepsis [9–15]. Originally, 35 mL/kg/h was the value identified to maximize survival, whereas higher doses did not seem to give additional benefits in the general population [9]. Subsequent studies have demonstrated that lower doses can be equally safe and successful in treating the critically ill patient, although effective delivery often differs significantly from prescription [11–20]. The second concept introduces the rationale for high-volume hemofiltration in specific patients with acute renal failure and sepsis [21–27]. СКАЧАТЬ