Machines for Continuous Renal Replacement Therapy

A significant number of advancements have taken place since the beginning of continuous renal replacement therapy (CRRT). In particular, high volume hemofiltration and high permeability hemofiltration have been successful extensions of the technique. The additional and combined use of sorbent has also been tested successfully. Specific machines have now been designed to permit safe and reliable performance of the therapy. These new devices are equipped with a friendly user interface that allows for easy performance and monitoring. The apparent complexity of the circuit is made simple by a self-loading circuit or a cartridge which includes the filter and the blood and dialysate lines. Priming is performed automatically by the machine and pre- or postdilution (reinfusion of substitution fluid before or after the filter) can easily be performed by changing the position of the reinfusion line. These new machines permit all CRRT methodologies to be performed by programming the flows and the total amounts of fluid to be exchanged or circulated as a countercurrent dialysate at the beginning of the session. Progress has been made not only in technology in this area but also on our understanding of the pathophysiology of acute renal failure. New biomaterials and new devices are now available with new frontiers are on the horizon. We might, however, speculate that although improvements have been made, a lot remains to be done. There is no doubt that technology has progressed enormously in critical care nephrology and that more progress will come in the near future. The goal, and likely outcome, is an improvement in the morbidity and mortality of the most severely ill patients.     

Anticoagulation for Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) has emerged as the preferred dialysis modality for critically ill patients with acute kidney injury, particularly those with hemodynamic instability. Anticoagulation is necessary for effective delivery of CRRT, but this requirement can also present challenges, as many critically ill patients with sepsis and inflammation already have a higher risk of bleeding as well as clotting. Without anticoagulation, CRRT filter and circuit survival are diminished, and therapy becomes less helpful. Heparins are presently the most commonly used anticoagulants worldwide for CRRT. They are widely available and can be easily monitored, but disadvantages include risks of hemorrhage, heparin resistance, and heparin-induced thrombocytopenia (HIT). Because of the potential side effects of heparin, alternative methods of anticoagulation have been investigated, including regional heparin/protamine, low molecular weight heparins, heparinoids, thrombin antagonists (hirudin and argatroban), regional citrate, and platelet inhibiting agents (prostacyclin and nafamostat). Each of these techniques has unique advantages and disadvantages, and anticoagulation for CRRT should be adapted to the patient's characteristics and institution's experience. Of the alternative methods, citrate anticoagulation is gaining wider acceptance with the development of simplified and safer protocols.     

Complications of Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) is commonly used in critically ill patients with acute kidney injury. Many studies show that compared with intermittent hemodialysis, continuous therapy has superior hemodynamic stability, metabolic clearance, and volume control. Despite these benefits, no survival advantage can be demonstrated with its use. Although study design explains much of this paradox, it is also quite plausible that the complications associated with CRRT negate its potential benefits in the critically ill patient. We summarize the common complications associated with the use of CRRT.     

Volume Management in Continuous Renal Replacement Therapy

Volume management is an integral component of the care of critically ill patients to maintain hemodynamic stability and optimize organ function. The dynamic nature of critical illness often necessitates volume resuscitation and contributes to fluid overload particularly in the presence of altered renal function. Diuretics are commonly used as an initial therapy to increase urine output; however they have limited effectiveness due to underlying acute kidney injury and other factors contributing to diuretic resistance. Continuous renal replacement techniques (CRRT) are often required for volume management. In this setting, successful volume management depends on an accurate assessment of fluid status, an adequate comprehension of the principles of fluid management with ultrafiltration, and clear treatment goals. Complications related to excessive ultrafiltration can occur and have serious consequences. A careful monitoring of fluid balance is therefore essential for all patients. This review provides an overview of the appropriate assessment and management of volume status in critically ill patients and its management with CRRT to optimize organ function and prevent complications of fluid overload.     

Drug Dosing During Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) has given clinicians an important option in the care of critically ill patients. The slow and continuous dialysate and ultrafiltrate flow rates that are employed with CRRT can yield drug clearances similar to an analogous glomerular filtration rate of the native kidneys. Advantages such as superior volume control, excellent metabolic control, and hemodynamic tolerance by critically ill patients are well documented, but an understanding of drug dosing for CRRT is still a bit of a mystery. Although some pharmaceutical companies have dedicated postmarket research in this direction, many pharmaceutical companies have chosen not to pursue this information as it is not mandated and represents a relatively small part of their market. This lack of valuable information has created many challenges in the care of the critically ill patient as intermittent hemodialysis drug dosing recommendations cannot be extrapolated to CRRT. This drug dosing review will highlight factors that clinicians should consider when determining a pharmacotherapy regimen for a patient receiving CRRT.     

Nursing Management of Continuous Renal Replacement Therapy

With CRRT becoming the preferred treatment for acute renal failure, more and more centers will be using this form of therapy. The preparation and on-going education of the nursing staff and their man-agement of the therapy determine the success of CRRT. It is imperative that nurses have clinical andtechnical expertise in the therapy in order for the patient to have positive outcomes on CRRT.     

Continuous Renal Replacement Therapy for Burned Patients: Renal and Systemic Considerations

Significant improvements in wound care have re-sulted in decreased mortality rates in burned pa-tients since the mid-seventies. The main determi-nants of survival remain the extent of the burn and the age. Infection is still the most frequent cause of mortality. Burned patients are prone to develop MOF, not only following sepsis, but from the sys-temic inflammation associated with thermal injury. Many metabolic derangements occur after a burn:hypermetabolism with several hormonal changes, enhanced catabolism and gluconeogenesis, im-paired ketogenesis and lipolysis. Aggressive nutri-tional support is particularly important in burned patients and avoiding a negative nitrogen balance is priority. Since early aggressive fluid resuscitation is widely applied, ARF occurs later during the course hospitalization, often after 10 days. Its pathogen-esis seems multifactorial, mainly related to sepsis and nephrotoxic agents, and is usually part of MOF. Dialytic support is challenged by the important fluid intake and removal required, the high catabolism, and the hemodynamic instability that characterize burned patients. Since they allow a better hemody-namic tolerance, a more precise fluid balance, and a more stable metabolic control, CRRTs appear as modalities of choice for ARF burned patients. How-ever, only three series report their usefulness for this selected population. In our experience, CRRTs have been performed over long periods and have allowed significant fluid loss over time. Bleeding complications from wounds have been much more frequent than for intensive care patients treated by CRRT with a similar anticoagulation regimen, and mandate prudent monitoring. Owing to limited vas- cular access sites and inherent risks of arterial cath-eterization, venovenous might be preferred to arte-riovenous modalities, if they are available. Despite more aggressive management, the mor-tality rates of burned patients with ARF remain high80%, reflecting the associated MOF. From a sys-temic point of view, considering the important vol-ume loss required, the potential for enhanced cyto-kine removal, and the important cumulative soluteclearances provided over time by CRRT, ARF burned patients should particularly benefit from continuous over intermittent modalities. When dia-lytic support has to be initiated, we consider CRRT, particularly hemodiafiltration which provides a larger dialysis dose, as the modality of choice.     

We use Continuous Renal Replacement Therapy for Overdoses and Intoxications

Extracorporeal modalities for the removal of drugs and toxins are indicated for the treatment of overdoses and intoxications. Well‐established modalities include hemodialysis (HD), high‐flux HD (HfD), and charcoal hemoperfusion (HP). Recently, there have been increasing reports on the use of continuous renal replacement therapy (CRRT), such as continuous veno‐venous hemodialysis (CVVHD), continuous veno‐venous hemofiltration (CVVH) or CVVH combined with dialysis (CVVHDF). In the present article, we will discuss the various factors that determine the clearance of drugs and toxins and accordingly, we will propose that with few exceptions, CRRT does not have a role in the routine management of intoxications.     

连续性肾脏替代治疗在慢性肾衰竭并发急性心肌梗死中的应用

目的:总结日间连续性肾脏替代治疗(CRRT)救治慢性肾衰竭并发急性心肌梗死的经验.方法:对9例慢性肾衰竭常规透析时发生急性心肌梗死的患者改行CRRT,观察临床效果,监测血生化、肾功能.结果:所有患者经CRRT治疗,心前区疼痛、胸闷、憋气均有不同程度缓解,7例患者度过急性期,平均治疗时间90～146 h,转为常规血透,目前仍存活;2例患者因并发症死亡.结论:CRRT操作简便,对血流动力学影响小,日间CRRT同样能有效救治病人,使其度过急性期,降低急性心肌梗死的病死率.     

The Predictors for Continuous Renal Replacement Therapy in Liver Transplant Recipients

Background

Acute renal failure (ARF) after liver transplantation requiring continuous renal replacement therapy (CRRT) adversely affects patient survival. We suggested that postoperative renal failure can be predicted if a clinically simple nomogram can be developed, thus selecting potential risk factors for preventive strategy.

Methods

We retrospectively reviewed the medical records of 153 liver transplant recipients from January 2008 to December 2011 at Severance Hospital, Yonsei University Health System, in Seoul, Korea. There were 42 patients treated with CRRT (20 and 22 patients received transplants from living and deceased donors, respectively) and 115 were not. Univariate and stepwise logistic multivariate analyses were performed. A clinical nomogram to predict postoperative CRRT application was constructed and validated internally.

Results

Hepatic encephalopathy (HEP; odds ratio OR, 5.47), deceased donor liver donations (OR, 3.47), Model for End-Stage Liver Disease (MELD) score (OR, 1.09), intraoperative blood loss (L; OR, 1.16), and tumor (hepatocellular carcinoma) as the indication for liver transplantation (OR, 0.11) were identified as independent predictive factors for postoperative CRRT on multivariate analysis. A clinical prediction model constructed for calculating the probability of CRRT post-transplantation was 1.7000 × HEP + [−4.5427 + 1.2440 × (deceased donor) + 0.0830 × (MELD score) + 0.000149 × the amount of intraoperative bleeding (L) − 2.1785 × tumor]. The validation set discriminated well with an area under the curve (AUC) of 0.90 (95% confidence interval, 0.85–0.95). The predicted and the actual probabilities were calibrated with the clinical nomogram.

Conclusions

We developed a predictive model of postoperative CRRT in liver transplantation patients. Perioperative strategies to modify these factors are needed.     

Continuous Renal Replacement Therapy: Cost Considerations and Reimbursement

Cost considerations with CRRT are important and vary substantially among centers. Major areas of concern are personnel, equipment, supplies, CRRT modality chosen and patients chosen. Costs are higher with CRRT than with either IHD or APD. These cost differences narrow as greater amounts of therapy are delivered. There are signif- icant areas for cost control in CRRT. Each center must evaluate its program to find the areas of cost control that are potentially available.