16.1 ECMO, CRRT, Dialysis, and Other Advanced Therapies

16.1 ECMO, CRRT, Dialysis, and Other Advanced Therapies

Quick Answer: Venoarterial (VA) ECMO supports heart and lungs and is the usual neonatal mode when PPHN, CDH, or cardiac failure produces shock. Venovenous (VV) ECMO supports the lungs only and requires adequate cardiac output. CRRT is preferred for unstable neonates who need controlled solute and fluid clearance, including many hyperammonemia cases. Peritoneal dialysis remains useful when vascular access or anticoagulation is unsafe. Therapeutic hypothermia belongs on the advanced-therapy list for qualifying HIE; the cooling protocol is in Chapter 11.

AACN Certification Corporation lists advanced therapy—ECMO, CRRT, dialysis, and therapeutic hypothermia—as a Multisystem Clinical Judgment problem on the current Neonatal CCRN Test Plan. This OpenExamPrep chapter teaches how the bedside nurse recognizes when conventional support has failed, which extracorporeal mode matches the physiology, and which complications to hunt for hour by hour. Independent practice items for this exam live at /practice/ccrn-neonatal.

Why these therapies sit in Multisystem

A neonate who reaches ECMO or kidney replacement therapy is rarely a single-organ story. Hypoxemic respiratory failure from persistent pulmonary hypertension of the newborn (PPHN) or congenital diaphragmatic hernia (CDH) quickly becomes a cardiac problem when the right ventricle fails against a high pulmonary vascular resistance. Cardiac ECMO after surgery or myocarditis quickly becomes a lung, kidney, and coagulation problem because the circuit consumes platelets, the kidneys see low pulse pressure, and the lungs need rest ventilator settings. The nurse's job is to keep the whole infant—brain, bleeding risk, temperature, family, and circuit—in view at once.

Think of advanced therapy as the last rung on a ladder you have already climbed: surfactant, inhaled nitric oxide, high-frequency ventilation, vasoactives, and meticulous lung-protective support. If you cannot name what has already been optimized, you are not ready to argue for a cannula.

Oxygenation index and failed conventional therapy

The oxygenation index (OI) is the number most exam items expect you to interpret:

OI = (mean airway pressure × FiO2 × 100) / PaO2

Use postductal PaO2 when the formula is quoted that way in neonatal respiratory ECMO literature. An OI greater than 40 for more than about 4 hours, a PaO2 persistently below 40 mm Hg despite intervention, pressor-resistant hypotension, or pulmonary hypertension with ventricular dysfunction are classic reasons to call the ECMO team. An OI in the mid-20s to 40s is severe disease: this is where you double-check iNO delivery, lung recruitment, sedation, hematocrit, and whether the heart is contributing to the hypoxemia. Do not treat a single OI as an automatic cannulation order—lethal anomalies, large intracranial hemorrhage, and irreversible brain injury remain reasons not to offer ECMO—but do not wait for a code either. Early notification of a center that actually runs neonatal ECMO is part of competent care.

Historical size and age floors (often near 2 kg and 34 weeks) exist because cannulas are large and intracranial hemorrhage risk is high in the most immature brains. Many programs have lowered those floors in selected infants; the exam still expects you to know why the floors existed: technical access and bleeding risk, not a belief that small infants cannot be hypoxemic.

VA versus VV: physiology first, then the neck

VA ECMO drains venous blood, runs it through a pump and membrane oxygenator, and returns oxygenated blood to the arterial tree. In a neonate that usually means a venous cannula via the right internal jugular vein into the right atrium and an arterial cannula via the right common carotid artery aiming at the aortic arch. The carotid is often ligated. VA unloads the heart, raises systemic oxygen delivery, and can support infants in shock. The prices are loss of a carotid, a more nonpulsatile arterial waveform, and a higher reported rate of neurologic injury than VV in respiratory series.

VV ECMO drains and returns on the venous side, typically with a dual-lumen cannula in the internal jugular vein. The infant's own heart must still eject. Coronary and carotid arteries receive blood that the left ventricle pumps. VV preserves the carotid, keeps pulsatile flow, and is attractive when the problem is the lung and the echo shows adequate cardiac function. If you place VV in a neonate whose left ventricle cannot generate output, you have an oxygenator attached to a pump that is not actually perfusing the body.

How PPHN, CDH, and cardiac disease map onto mode

PPHN is extra-pulmonary right-to-left shunting across the ductus and foramen ovale because pulmonary vascular resistance never fell. Many PPHN infants improve with oxygen, iNO, lung recruitment, and support of the right ventricle. ECMO is for the subset who still have life-threatening hypoxemia or ventricular failure. If blood pressure and echo are acceptable, VV can treat the gas-exchange problem and often improves hemodynamics simply by raising mixed venous oxygen. If the infant is on escalating vasoactives, has a collapsing right ventricle, or is about to arrest, VA is the safer default.

CDH combines lung hypoplasia, pulmonary hypertension, and frequent left-ventricular underfilling. About 15 to 30 percent of CDH infants need ECMO in contemporary series. Inability to keep preductal saturations above roughly 85 percent, pH below 7.15 despite optimized ventilation, peak inspiratory pressures above about 28 cm H2O or mean airway pressure above about 17 cm H2O, OI above 40, or shock with oliguria are the physiologic pictures that trigger a call. VA remains common because so many of these infants have mixed cardiopulmonary failure. Some centers start VA and later convert to VV once the heart recovers. Repair of the diaphragm while on ECMO is a surgical decision; nursing priorities stay bleeding, lung rest, and the brain.

Cardiac indications include postoperative inability to separate from bypass, acute myocarditis, refractory cardiogenic shock, and, in some centers, extracorporeal CPR. Those runs are VA (or central cannulation in the chest). Do not offer VV as the primary mode for pump failure.

The heparinized circuit: bleeding versus clot

Neonatal ECMO requires systemic anticoagulation, most often unfractionated heparin, because blood meeting plastic wants to clot. The same heparin turns every recent puncture, the cannulation wounds, the lung, the gut, and the brain into bleeding risks. Bleeding is the complication that kills or maims if you miss it; circuit thrombosis is the complication that embolizes or stops flow if you ignore the bladder, the connectors, and the oxygenator color.

Bedside surveillance is not optional decoration:

• Cannulation sites: ooze, hematoma, sudden swelling of the neck
• Neurologic: pupils, fontanelle, seizures, unexplained hemoglobin drop (think intracranial hemorrhage)
• Circuit: clots on connectors, increasing transmembrane pressure, dark or streaked oxygenator, chatter, air, declining flow for the same RPM
• Hemolysis: pink-tinged urine, rising plasma-free hemoglobin, falling hematocrit without obvious external loss
• Coagulation panel: platelets are consumed; fibrinogen falls; ACT or anti-Xa is interpreted with the perfusionist, not in isolation

Lung rest settings (limited peak pressure, modest PEEP, low rate, FiO2 toward 0.3–0.5 once saturations allow) exist so the native lung can recover. Sweep gas mainly clears carbon dioxide; circuit blood flow mainly determines oxygenation on VA. Correct hypercarbia slowly to avoid cerebral blood-flow swings.

CRRT versus peritoneal dialysis

Continuous renal replacement therapy (CRRT)—CVVH, CVVHD, or CVVHDF—pulls blood through a filter and returns it. It is the usual extracorporeal choice when the neonate is hemodynamically unstable, when fluid overload (often cited around more than 10 percent) is worsening gas exchange, or when a urea-cycle or organic-acid crisis has produced dangerous hyperammonemia. Intermittent hemodialysis clears ammonia fastest in a large child; in a 3 kg neonate the same treatment can crash the blood pressure and then allow ammonia to rebound when you stop. High-dose continuous dialysis with a later step-down is a common modern compromise. CRRT also lets you create space for nutrition and infusions in an oliguric infant. Costs include a large dual-lumen catheter or a connection into an ECMO circuit, anticoagulation (heparin or citrate), hypothermia, filter clotting, and stripping of phosphate, potassium, and many antibiotics—so doses must be adjusted.

Peritoneal dialysis (PD) uses the peritoneum as the membrane. Fill volumes often start near 10–20 mL/kg. PD needs no extracorporeal blood volume and little or no systemic heparin, which is why many nurseries still reach for it first in isolated neonatal AKI when the belly is intact. It is slower and less predictable for ammonia, can splint the diaphragm and worsen ventilation, leaks around the catheter, risks peritonitis, and is a poor plan after recent abdominal surgery or active NEC. If CRRT is hours away and potassium is 8 mEq/L with peaked T waves, start whatever dialysis you can staff safely rather than waiting for a perfect modality.

Worked scenario

A 39-week infant with meconium aspiration and PPHN sits on HFOV, iNO 20 ppm, and two vasoactives. Preductal saturation is 82 percent, postductal PaO2 is 38 mm Hg, MAP is 18 cm H2O, FiO2 is 1.0. OI is (18 × 1.0 × 100) / 38 ≈ 47, and it has been in that range for 5 hours. Echo shows a dilated, poorly functioning right ventricle. This is not a VV-first thought experiment: the infant needs VA ECMO unless a contraindication (for example a large ICH) is found on a pre-cannulation head ultrasound. After cannulation you would rest the lungs, watch the neck and the fontanelle, and keep the circuit in your visual field every time you walk in the room.

Therapeutic hypothermia as an indication, not a protocol dump

Therapeutic hypothermia (TH) is the fourth named advanced therapy on the test plan. List it here as the neuroprotective therapy indicated for a qualifying term or near-term neonate with moderate-to-severe hypoxic-ischemic encephalopathy who meets blood-gas and/or resuscitation criteria and can start within the usual therapeutic window (typically 6 hours of age). Inclusion details, target temperature, duration, monitoring, and rewarming live with HIE in Chapter 11. Do not start cooling as a substitute for ECMO in isolated PPHN, and do not skip the HIE exam just because the infant is already on a circuit. Some infants receive both; that is a combined-risk situation (coagulopathy plus hypothermia plus heparin), not a reason to memorize the cooling recipe twice.

Exam traps

• Choosing VV because the diagnosis is respiratory when the blood pressure and ventricle have already failed
• Treating OI as a trivia number without naming MAP, FiO2, and PaO2
• Offering PD as the fastest ammonia therapy
• Reciting the full TH protocol in a Multisystem advanced-therapy item when the question only asks whether cooling is indicated
• Forgetting that the nurse's ECMO job is bleeding versus clot, not turning the oxygenator into a chemistry experiment

If you also sit adult or pediatric CCRN, keep the populations separate: neonatal neck cannulation and CDH physiology are not interchangeable with femoral adult VA. Pediatric content on OpenExamPrep is at /study-guides/ccrn-pediatric; adult CCRN is at /study-guides/ccrn.