872 inserted permanent catheters are associated with fewer acute complications [89] Ideally, a surgi cal permanent catheter should have a few days (or preferably weeks) to heal before use, but immedia[.]
872 inserted permanent catheters are associated with fewer acute complications [89] Ideally, a surgical permanent catheter should have a few days (or preferably weeks) to heal before use, but immediate use is often necessary in patients with AKI. If one cannot wait, using small fill volumes should be used to reduce the risk of catheter leak and infection Since the use of automated peritoneal dialysis devices (cyclers) requires a significant amount of dead space for tubing and minimal fill volume for accurate functioning, their use in neonates is limited Instead, manual continuous low-volume cycles at the bedside are usually employed The manual PD setup involves a Buretrol device to measure volumes, to which the dialysate bag is attached to one end through spikes or a Luer lock, while the other end is connected to the PD catheter via a Y-set The other limb of the Y-set is connected to the drainage line An example of a commercially available neonatal/infant manual PD set is shown in Fig. 44.1 (Dialy-Nate system, Utah Medical Products, Midvale, Utah) This pre-assembled closed system with a total priming volume of 63 mL includes a 150 mL burette, a graduated dialysate meter for measuring outflow, and an inline helical infusate warmer Warming the dialysate is extremely important for the neonate with their higher risk of temperature instability and hypothermia In the acute setting, the default PD cycle duration is 60 minutes Approximately 10 ml/kg (or 200 ml/m2) of dextrose-based dialysis fluid fills the abdomen, dwells, and then drains The fill, dwell, and draining phases should be 5–10, 40–50, and 5–10 minutes in length, respectively If more clearance of fluid or waste products is needed, then 32 cycles lasting 45 minutes can be performed in 24 hours Another method to increase clearance is by increasing the dwell volume, but needs to be mitigated with higher chances of leaking from the catheter exit site Increasing the dextrose concentration can increase ultrafiltration and may be necessary with low fill volumes If commercially manufactured fluids are not available, they can be locally prepared [90] Some programs add 500 units of heparin/L to prevent catheter obstruction from C Mammen and D Askenazi blood or fibrin Potassium and phosphorous can also be added to the dialysate to prevent hypokalemia and hypophosphatemia, respectively, both of which can occur with prolonged frequent exchanges In discussions with the treating team, our patient was placed on PD, and the local surgeon placed a tunneled PD catheter in the OR with no complications Manual PD was started using 30 ml fill volumes (10 ml/kg with 1.5% dextrose) with hourly cycles The cycles consisted of 10-minute fill times, 40-minute dwell times, and 10-minute drain times In the first 12 hours, total ultrafiltration was 100 mL, and hyperkalemia, acidosis, and hyperphosphatemia improved Total protein intake was increased back to 2.5 g/ kg/day to account for ongoing losses inherent to PD. At 24 hours after starting PD, a large leak developed around the catheter exit site, and PD could no longer be utilized effectively Due to ongoing oliguric AKI, a decision was made to start extracorporeal therapy in the form of CRRT (continuous renal replacement therapy) Extracorporeal Therapies RRT using extracorporeal therapies has several advantages over PD. The first is that once vascular catheter access is established, the therapy can be started immediately Second, higher clearances can be achieved, which can be critical in neonates, especially in those with severe hyperammonemia from inborn errors of metabolism [87, 91] Third, the net ultrafiltration rate can be precisely titrated for the desired effect, and changes can be made in real time as necessary This differs from fluid removal approaches in PD where the clinician prescribes a specific dextrose concentration, fill volume, and dwell time and then explores empirically what rates of fluid removal are achieved for several hours before the PD prescription is changed There are also several disadvantages to extracorporeal therapies First, the cost of specialized equipment is higher Second, the nursing expertise is significantly higher Third, there are risks to anticoagulation Fourth, there is risk for hemo- 44 Neonatal Acute Kidney Injury Fig 44.1 Neonatal/ infant manual peritoneal dialysis set (Dialy-Nate system from Utah Medical Products, MidVale, UT) 873 C Mammen and D Askenazi 874 dynamic instability during initiation This risk can be mitigated to some degree by priming the circuit with blood in conjunction with steps to make the blood more physiologic before initiation Finally, compared to older children, placement of a catheter is more challenging and has potentially more complications, especially in situations with significant fluid overload and high ventilation support need renal support for more than a few weeks, the preferred location is a right internal jugular catheter (ideally tunneled with a cuff) Femoral and umbilical veins are usually smaller diameter than internal jugular veins, but can be used With smaller circuits, smaller vascular access (5 or French) can be used to provide adequate flows for these machines Fluid to Prime Machine Vascular Access The ideal location for catheter placement depends on multiple factors including the size of the patient, estimated duration of therapy (cuffed catheters are preferred if the estimated duration of the CRRT will be for at least weeks), urgency of the therapy, and local expertise Access is achieved with either a double-lumen catheter or two single-lumen catheters (see Table 44.3 for sizes for neonates/infants) For those who will Whether one is using hemodialysis (HD) or continuous renal replacement therapy (CRRT), the clinician must determine which type of fluid is required to prime the machine as the relatively large extracorporeal volume places a young infant at a higher risk of cardiovascular instability upon initiation of RRT. The extracorporeal volume (ECV)/total blood volume (TBV) has been used as a gauge to determine the type of prime to use The TBV of a neonate can be esti- Table 44.3 Central venous catheter types and sizes for neonatal/infant extracorporeal therapies Weight 2.5 kg As Above Medcomp 8Fr × 18 cm DLC with cuff Un-cuffed (un-tunneled) × Single-lumen Cook 3 F or higher single-lumen catheter Cook 4Fr × 5 cm DL Right IJ b Cook 5Fr × 5 cm DLC Right IJ b Cook 6.5Fr × 12 cm DLC Femoral a,b Bard 6Fr × 50 cm (POWERHOHN) DLC Right IJ Femoral Umbilical b Gambro 6Fr × 15 cm DLC Femoral Umbilical Medcomp 7Fr × 7 cm DLC Right IJ As Above × Single-lumen 4Fr or higher catheter Medcomp 7Fr × 10 cm DLC Femoral Fr French, DLC double-lumen catheter Note: The diameter of the catheter needs to be tailored to the size of the vessel by ultrasound Above are catheters that have been suggested/reported for small infants a PowerHohn and Powerline catheters are designed to cut the desired length b These catheters have been reported in use with circuits with smaller extracorporeal volume (Aquadex, Carpediem, and Nidus) 44 Neonatal Acute Kidney Injury mated as 80 ml/kg In general, if the ECV/TBV is 10% of the ECV/ TBV. An albumin prime can be used when the ECV is 10–15% of the TBV. A blood prime may be preferable when the ECV is >15% of the TBV or for any patients not stable enough for a saline or albumin prime Priming the circuit with packed red blood cells (pRBC) can reduce morbidity; however, it is important to recognize that compared to physiologic blood, pRBC are cold, very concentrated, acidic, hyperkalemic, and hypocalcemic Most centers that perform neonatal CRRT have protocols in place to buffer the acidic environment, reverse hypocalcemia, and dilute the higher hematocrit of pRBCs Even with these measures, blood primes are not without risk, as blood primes can cause hypothermia, acidosis, hypocalcemia, hyperkalemia, thrombocytopenia, hypotension, and coagulopathy These risks increase exponentially with smaller-sized infants, those who are often hemodynamically unstable, along with the frequent need of repeated RRT initiation [92] Continuous Versus Intermittent Duration Hemodialysis Intermittent hemodialysis (HD) using standard dialysis machines is the most efficient form of renal support clearance and is usually provided over a 3–4-hour period However, the main challenge of HD is related to the machines requiring expert nursing care from dialysis-trained personnel Intermittent hemodialysis can be used if the goals of the therapy can be achieved in a short amount of time However, if the patient is hemodynamically unstable, it may be very difficult to accomplish the fluid removal goals during a short intermittent therapy The dialyzer size should be between 75% and 100% of the infant’s total body surface area to minimize the ECV while maintaining effective solute removal Dialyzers with smaller surface 875 areas of 0.2m2 (e.g., Gambro Polyflux 2H, Fresenius FX Paed) and 0.4m2 (e.g., Fresenius F3) are available along with low priming volumes (17 mL and 28 mL, respectively) Blood lines designed for neonates with low volumes are also available (e.g., Gambro Phoenix BTS neonatal lines with 40 ml volume and Fresenius 2008K neonatal line options with 29ml and 52 ml) There are no published recommendations for blood flow rates in neonates Initial blood flows should be prescribed to provide adequate clearance and flow to prevent clotting Not more than 5% of the body weight should be removed per session with ultrafiltration to maintain hemodynamic stability Most centers use systemic heparin for anticoagulation during HD. A report of HD in 33 infants kg This filter has been available in Canada, Europe and other countries for several years with good experience CRRT machines with even smaller ECV should reduce the risks associated with the therapy and improve outcomes For these reasons, several groups have developed or adapted dialysis and convective clearance devices which use a smaller size circuit The miniaturization of CRRT devices allows for adequate flows with much smaller diameter catheters In addition, initiation of CRRT circuit with much lower ECV is for the C Mammen and D Askenazi most part uneventful, even in very small and very critically ill infants [95] The Newcastle infant dialysis ultrafiltration system (Nidus) [96] has an ECV of around 10 ml and can provide continuous or intermittent dialysis with the use of a French single-lumen catheter (Fig. 44.2a) The circuit uses automated syringe pumps to accomplish four separate steps: (a) remove a volume of blood from the patient, (b) send blood through a dialysis filter that has counter-current dialysis running, (c) return the blood back to the initial syringe pump, and (d) return that volume of blood (now cleaned) back to the patient The cardio-renal pediatric dialysis emergency machine (Carpediem™) has available circuits of 27, 34, and 45 ml [96, 97] for filters of 0.075m2, 0.15m2, and 0.25m2, respectively (Fig. 44.2b) By using a smaller blood pump with a unique design, it reduces the peak pressure for a given blood volume, reducing the need for a very wide catheter A 4.5 French double-lumen catheter can be used to accomplish the flow rates required for this machine The circuit has to be exchanged daily The blood flow rate can be titrated from to 40 ml/minute, and it has very precise fluid scales available, minimizing any potential errors of ultrafiltration To mitigate concerns posed by CRRT machines with large ECV in relation to blood volume size, Askenazi et al adapted the Aquadex™ machine (a machine initially designed for ultrafiltration in adults with heart failure) to provide convective clearance by using an independent IV pump to deliver the replacement fluid (Fig. 44.2c) The machine can ultrafilter up to 500 ml/hour It has an integrated hematocrit detector that can help mitigate any abrupt changes in hematocrit This system can provide clearance, electrolyte balance, and fluid ultrafiltration with minimal need for interventions during circuit initiation [95] The biggest drawback to this system is that the replacement pump is not directly in communication with the blood flow pump Several catheters have been used in the right internal jugular, femoral, and umbilical veins More recently, use of a French double-lumen catheter (Bard Powerline 6Fr x 50 cm tunneled, Tempe AZ, USA) that is cut to 44 Neonatal Acute Kidney Injury Fig 44.2 Newer renal replacement therapy devices designed for neonates and young infants (a) The Newcastle infant dialysis ultrafiltration system (Nidus) The circuit has two operating syringes (1), a high-flux polysulfone 0.045 m2 filter (2), a heparin syringe (3), pumped dialysate (4), a pressure transducer (5) and an air-detector (6), and self-primes with 4.3 ml of heparinized saline, giving a minimum operating volume of 9.3 ml (b) The cardio-renal pediatric dialysis emergency machine (Carpediem™) (c) Continuous venovenous hemofiltration (CVVH) using the Aquadex™ machine Heparin is infused through a y-connector attached to the withdraw (access) line of the patient’s catheter Using an in-line medication infusion machine, prereplacement 877 fluid is infused via the proximal pigtail of the circuit There are two pumps on the machine: the blood pump (which can pump blood to a maximum of 40 ml/min) and the ultrafiltration (UF) pump (which can perform UF to a maximum of 500 ml/h when the blood flow is 40 ml/ min) Blood for anticoagulation monitoring is obtained through the distal pigtail of the circuit A blood warmer is attached to the tubing on the infusion (return) line before the blood is returned to the patient (Reprinted with permission from Coulthard et al [56] Reprinted with permission from Ronco C and Ricci Z. Evolution of the Management of AKI in Neonates ASN Kidney News Volume 2015 Reprinted with permission from Askenazi et al [95]) ... hematocrit This system can provide clearance, electrolyte balance, and fluid ultrafiltration with minimal need for interventions during circuit initiation [95] The biggest drawback to this system... infants