Continuous arteriovenous hemofiltration in premature infants

Anticoagulation in patients with acute kidney injury undergoing kidney replacement therapy

Kidney replacement therapy (KRT) is used to provide supportive therapy for critically ill patients with severe acute kidney injury and various other non-renal indications. Modalities of KRT include continuous KRT (CKRT), intermittent hemodialysis (HD), and sustained low efficiency daily dialysis (SLED). However, circuit clotting is a major complication that has been investigated extensively. Extracorporeal circuit clotting can cause reduction in solute clearances and can cause blood loss, leading to an upsurge in treatment costs and a rise in workload intensity. In this educational review, we discuss the pathophysiology of the clotting cascade within an extracorporeal circuit and the use of various types of anticoagulant methods in various pediatric KRT modalities.

A Meta-Analysis of Extracorporeal Anticoagulants in Pediatric Continuous Kidney Replacement Therapy

OBJECTIVE

Continuous kidney replacement therapy (CKRT) is the primary therapeutic modality utilized in hemodynamically unstable patients with severe acute kidney injury. As the circuit is extracorporeal, it poses an increased risk of blood clotting and circuit loss; frequent circuit losses affect the provider's ability to provide optimal treatment. The objective of this meta-analysis is to evaluate the safety and efficacy of the extracorporeal anticoagulants in the pediatric CKRT population.

DATA SOURCES

We conducted a literature search on PubMed/Medline and Embase for relevant citations.

STUDY SELECTION

Studies were included if they involved patients under the age of 18 years undergoing CKRT, with the use of anticoagulation (heparin, citrate, or prostacyclin) as a part of therapy. Only English articles were included in the study.

DATA EXTRACTION

Initial search yielded 58 articles and a total of 24 articles were included and reviewed. A meta-analysis was performed focusing on the safety and effectiveness of regional citrate anticoagulation (RCA) vs unfractionated heparin (UFH) anticoagulants in children.

DATA SYNTHESIS

RCA had statistically significantly longer circuit life of 50.65 hours vs. UFH of 42.10 hours. Two major adverse effects metabolic alkalosis and electrolyte imbalance seen more commonly in RCA compared to UFH. There was not a significant difference in the risk of systemic bleeding when comparing RCA vs. UFH.

CONCLUSION

RCA is the preferred anticoagulant over UFH due to its significantly longer circuit life, although vigilant circuit monitoring is required due to the increased risk of electrolyte disturbances. Prostacyclin was not included in the meta-analysis due to the lack of data in pediatric patients. Additional studies are needed to strengthen the study results further.

Prostacyclin as an Anticoagulant for Continuous Renal Replacement Therapy in Children

Effective delivery of continuous renal replacement therapy (CRRT) depends on the longevity of the filter and circuit used in the CRRT machine. Safe and effective anticoagulation is crucial for maintaining the patency of these circuits. In children, heparin and citrate are the commonly used anticoagulants but they are limited by serious side effects and thus calls for meticulous monitoring. In conditions where neither of these can be used, prostacyclin can be an effective alternative. Prostacyclin is a platelet inhibitor that can be safely used as an efficient anticoagulant in CRRT. When combined with heparin, it induces a heparin-sparing effect, which can reduce the dosage and side effects of heparin. Furthermore, there is no need for performing time-consuming monitoring tests. Although prostacyclin seems to be an attractive option, there is scanty evidence about its use as an anticoagulant in CRRT in children. We review the evidence and practicalities, and propose a guideline for the use of prostacyclin as an anticoagulant in children requiring CRRT.

Acute lung injury in pediatric intensive care in Australia and New Zealand: a prospective, multicenter, observational study

OBJECTIVE

Acute lung injury (ALI) is poorly defined in children. The objective of this prospective study was to clarify the incidence, demographics, management strategies, outcome, and mortality predictors of ALI in children in Australia and New Zealand.

DESIGN

Multicenter prospective study during a 12-month period.

SETTING

Intensive care unit.

PATIENTS

All children admitted to intensive care and requiring mechanical ventilation were screened daily for development of ALI based on American-European Consensus Conference guidelines. Identified patients were followed for 28 days or until death or discharge.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 117 cases of ALI during the study period, giving a population incidence of 2.95/100,000 <16 yrs. ALI accounted for 2.2% of pediatric intensive care unit admissions. Mortality was 35% for ALI, and this accounted for 30% of all pediatric intensive care unit deaths during the study period. Significant preadmission risk factors for mortality were chronic disease, older age, and immunosuppression. Predictors of mortality during admission were ventilatory requirements (peak inspiratory pressures, mean airway pressure, positive end-expiratory pressure) and indexes of respiratory severity on day 1 (Pao2/Fio2 ratio and oxygenation index). Higher maximum and median tidal volumes were associated with reduced mortality, even when corrected for severity of lung disease. Development of single and multiple organ failure was significantly associated with mortality.

CONCLUSIONS

ALI in children is uncommon but has a high mortality rate. Risk factors for mortality are easily identified. Ventilatory variables and indexes of lung severity were significantly associated with mortality.

Continuous renal replacement therapy in children up to 10 kg

BACKGROUND

There is growing use of continuous renal replacement therapy (CRRT) for pediatric patients, but no large studies reporting CRRT use and outcome in young children. We describe a cohort of patients weighing 10 kg or less who underwent CRRT at five US children's hospitals between 1993 and 2001.

METHODS

We reviewed records of 85 patients weighing 10 kg or less who underwent at least 24 hours of CRRT. We evaluated weight, diagnosis, pressor number, CRRT characteristics, days on CRRT, and outcome (survival to leave intensive care unit versus death).

RESULTS

Patients weighed 1.5 to 10 kg (mean, 5.3 +/- 2.8 kg; 16 patients < or = 3 kg). Sixty-nine percent of patients were being administered pressors at the time of CRRT initiation, 88% of patients were administered heparin, and the others were administered citrate or no anticoagulation. Mean blood flow was 48 +/- 24 mL/min (range, 15 to 106 mL/min) or 9.5 +/- 4.2 mL/min/kg. Six hundred fifty-five patient-days of therapy were studied (mean, 7.6 +/- 8.6 d/patient; range, 1 to 46 d/patient). Thirty-two patients (38%) survived; 4 of 16 patients (25%) weighing 3 kg or less survived. The smallest survivor weighed 2.3 kg. Overall, survivors and nonsurvivors showed no significant difference in weight, days on CRRT, or pressor number. However, for patients weighing more than 3 kg, 28 of 69 patients (41%) survived, and mean pressor number was lower for survivors versus nonsurvivors (0.96 +/- 1.1 versus 1.6 +/- 1.0 pressors; P < 0.03).

CONCLUSION

CRRT is feasible and useful in children weighing 10 kg or less. Hemodynamic instability requiring pressor support neither precludes successful CRRT nor adversely affects survival. After CRRT, the survival rate in children who weigh 3 to 10 kg is similar to that in older children and adolescents.

Pharmacokinetics of Catecholamines During Hemofiltration in Pediatric Patients

BACKGROUND: Continuous hemofiltration is used in pediatric patients with acute renal failure. Many of these patients are treated with catecholamines for hemodynamic instability. The authors studied the pharmacokinetics of dopamine and dobutamine on patients undergoing continuous venovenous hemofiltration. METHODS AND RESULTS: Three critically ill pediatric patients with acute renal failure and cardiovascular instability treated with hemofiltration and intravenous infusion of dopamine and/or dobutamine were entered into the study. Blood samples were drawn at steady-state levels from the arterial port (inflow) of the hemofilter, from the venous port (outflow) of the hemofilter, and from the ultrafilter. Sixteen (n = 16) pharmacokinetic measurements were made, six (n = 6) for dopamine and 10 (n = 10) for dobutamine. The clearance of dopamine by the hemofilter was 0.078 +/- 0.011 mL/kg/min, and for dobutamine it was 0.036 +/- 0.008 mL/kg/min. On the average, 0.56% of the dopamine dose and 0.13% of the dobutamine dose was removed by the hemofilter. CONCLUSIONS: The pharmacokinetics of dopamine and dobutamine at the dosage range of 5-25 µg/kg/min are not altered by continuous hemofiltration. Relative to total plasma clearance, negligible amounts of the drug were removed. The dosage of these catecholamines need not be adjusted during continuous hemofiltration.

Haemodynamic effects of arteriovenous and venovenous haemofiltration in piglets

The aim of this study was to compare the early haemodynamic effects of continuous arteriovenous haemofiltration (CAVH) with those of continuous venovenous haemofiltration (CVVH) in normal and endotoxic piglets, within the framework of a two-period cross-over trial. Sixteen domestic piglets (weight 6-18 kg) underwent 1 h of CAVH followed by 1 h of CVVH or 1 h of CVVH followed by 1 h of CAVH. Six were pre-treated with a graded endotoxin infusion to simulate clinical sepsis. The main measurements included: heart rate; mean arterial (MAP), pulmonary artery, central venous and pulmonary artery occlusion pressures; thermodilution cardiac output; and calculated systemic (SVRI) and pulmonary vascular resistance indexes. Each measurement was performed immediately before and 30 min after commencement of each technique of filtration. Commencement of haemofiltration in normal piglets caused minimal haemodynamic effects. In endotoxic piglets, commencement of filtration, whether CAVH or CVVH, caused a haemodynamic change which was significantly more pronounced in the first filter (SVRI -39%, MAP -32%) than the second filter (SVRI +22%, MAP +0.9%) (SVRI, P=0.01, first filter vs. second) (MAP, P=0.009 first filter vs. second). In conclusion, there were no significant differences between the early haemodynamic effects of CAVH and CVVH in normal or endotoxic piglets. The haemodynamic effects of either technique may become more significant in the presence of sepsis.

Use of peritoneal dialysis, continuous arteriovenous hemofiltration, and continuous arteriovenous hemodiafiltration for removal of ammonium chloride and glutamine in rabbits

OBJECTIVE

We compared the ability of peritoneal dialysis, hemofiltration, and continuous hemodiafiltration to remove infused ammonium chloride.

STUDY DESIGN

Anesthetized adult rabbits received an intravenous infusion of ammonium chloride. Two methods of removal of ammonium chloride were performed in each animal and compared. In group 1 (n = 6), peritoneal dialysis (dialysate = 75 ml.kg-1) and continuous arteriovenous hemofiltration (CAVH) with a polysulfone 800 cm2 hemofilter (Minifilter Plus; Amicon Division, W. R. Grace & Co., Danvers, Mass.) were simultaneously performed for 40 minutes. In group 2 (n = 6), peritoneal dialysis and continuous arteriovenous hemodiafiltration (CAVHD) (dialysate flow = 1000 ml.hr-1) were simultaneous performed for 40 minutes. In group 3 (n = 6), CAVH and CAVHD were performed successively in random order for 30 minutes each.

RESULTS

Animals had high and stable ammonium chloride and glutamine plasma levels during the experimental procedure. No significant difference in ammonium chloride clearance was observed between PD and CAVH (group 1). In comparison with PD or CAVH, CAVHD resulted in significantly higher clearances of ammonium chloride (40% +/- 10% vs 96% +/- 34%, respectively) and of glutamine (195% +/- 17% vs 77% +/- 25%, respectively).

CONCLUSION

The overall results indicate that CAVHD should be considered for hyperammonemia when peritoneal dialysis is indicated but unfeasible or inefficient.

A review of venovenous haemofiltration in seriously ill infants

Between April 1989 and October 1991, 13 severely ill infants, median age 13 days (range 1-180 days), median weight 3.5 kg (range 2.5-4.8 kg), received continuous venovenous haemofiltration (CVVH) for a median duration of 39 h (range 5-234 h). Filtration was performed through a double lumen catheter inserted into a central vein. The indications for filtration included acute renal failure (8), fluid overload (5), inborn errors of metabolism (3) and sepsis (1). Some infants had more than one indication. The median Paediatric Risk of Mortality (PRISM) score on the day of admission to the intensive care unit was 27 (range 8-42). No change in the level of respiratory support was required following the commencement of CVVH. Serum electrolyte concentrations and plasma osmolality remained normal throughout. Serum creatinine fell from a mean of 0.11 mmol/L (95% CI 0.058-0.168) to 0.07 mmol/L (CI 0.034-0.112). Urea fell from a mean of 9.5 mmol/L (CI 4.4-14.6) to 6.5 mmol/L (CI 2.7-10.3). Platelet counts fell by 40-50% from a mean of 126 x 10(6)/mm3 (CI 72-180) to 69 x 10(6)/mm3 (CI 36-103) 18 h following commencement of filtration but no bleeding was encountered. The main complication was a thrombosis of the superior and inferior vena cava in one infant. Four infants survived to be discharged from intensive care. Continuous venovenous haemofiltration, with its inherent advantages over arteriovenous haemofiltration, is feasible in small infants using standard paediatric equipment.

Hemofiltration modifies complement activation after extracorporeal circulation in infants

Complement and fibrinolytic factors were measured in 9 infants undergoing hemofiltration immediately after cardiopulmonary bypass in an attempt to reduce activation of these systems. Plasma levels of C3a, C5a, and terminal complement complexes increased during bypass by 460%, 85%, and 745%. Plasma levels were reduced after hemofiltration in 8 of the 9 infants, and C3a and C5a fractions were recovered in the ultrafiltrate. The observed activation of the fibrinolytic system seemed to be unaltered by hemofiltration. Fibrinolytic factors were not filtered. Our study shows that increased concentrations of complement factors in the plasma after bypass in infants may be reduced by hemofiltration.

Peritoneal dialysis for acute renal failure in children

Fifty infants and children with acute renal failure were treated with acute peritoneal dialysis between 1987 and 1990. The patients were dialyzed using either a catheter introduced percutaneously over a guide-wire (n = 40) or a Tenckhoff catheter (n = 10). The cause of the acute renal failure was primary renal disease in 17 children, cardiac disease in 19, and trauma/sepsis in 14. Peritoneal dialysis succeeded in controlling metabolic abnormalities, improving fluid balance, and relieving the complications of uremia. The procedure had few major complications. Overall mortality was 50%, reflecting the serious nature of the underlying diseases. We conclude that acute peritoneal dialysis is a safe and effective treatment in most pediatric patients with acute renal failure. Our series of patients treated with acute peritoneal dialysis serves as a basis of comparison for the evaluation of new modalities of therapy in childhood acute renal failure.

Comparison of pump-driven and spontaneous continuous haemofiltration in postoperative acute renal failure

In a comparison of spontaneous continuous arteriovenous haemofiltration (CAVH) and pump-driven haemofiltration (PDHF) for acute renal failure after surgery, 116 patients admitted to a surgical intensive care unit were assigned CAVH (48) or PDHF (68). The method of assignment was that a patient was treated by PDHF if he or she was the only patient requiring treatment at that time (only one pump was available); any other patient coming to the unit would be treated by CAVH. The groups were slightly unbalanced because there were fewer simultaneous cases than expected. The main endpoints were survival rate, control of uraemia, and additional application of haemodialysis. There were no differences between the patient groups in age, duration of treatment, severity of illness, serum creatinine concentration at the start of treatment, or cause of acute renal failure. Both treatments adequately controlled uraemia and fluid overload. However, the survival rate was significantly higher with PDHF than with CAVH (6 [12.5%] vs 20 [29.4%]; p less than 0.05). The daily ultrafiltrate volume was significantly higher with PDHF than with CAVH (15.7 [95% confidence interval 13.6-17.8] vs 7.0 [6.6-7.4] l/day; p less than 0.05). The volume of ultrafiltrate in patients with ischaemic or sepsis-induced acute renal failure was correlated with the survival rate. This finding suggests that the better survival rate in the PDHF group was due to faster elimination of toxic mediators (of molecular weight 800-1000 daltons) through the filter membrane by high-volume haemofiltration.