Link to the by Nick Mark MD onepagericu.com RENAL REPLACEMENT ONE most current @nickmmark DEFINITION: COMPONENTS OF A CIRCUIT & PARAMETERS SET: version → Renal Replacement (RRT) are (UF) is the of FLOW RATE (Q ) is the flow used in patients in the IUC with renal failure B ANTICOAGULATION may be used to remove excess fluid or to clear the from the blood, driven by the transmembrane pressure rate of blood through the circuit. (CITRATE or ) to reduce in the circuit. It blood of toxins (such as or ). (TMP) gradient between the blood & effluent. TMP can Higher flows enable greater clearance/UF is typically reversed on return. be titrated by adjusting the effluent pump & pressure. & have lower thrombosis risk but may · Clearance (K) is the volume of blood Filter “Arterial” Temporary � + � require larger access & have more cleared of a solute (typically urea) per time. ������ ������ pressure Blood or access central venous �� ∝ ��� ��� = − ��������� adverse hemodynamic effects. Clearance depends on Blood flow (Q ), � Pump pressure dialysis B Ultrafiltration (UF) provides clearance by convection dialysate flow (QD) and the dialyzer. There are two primary mechanisms involved: (also called solute drag) removing small & medium sized molecules. Effluent · (with dialysis) clears smaller pressure molecules (<200 D), while convection (with DIALYSATE is an Heater UF) clears small & medium sized (< 50kD) Effluent warms “Venous” molecules. isotonic fluid containing , Pump /acetate, glucose, & returning or return blood INDICATIONS: sometimes other small molecules. pressure

Urgent/emergency RRT may be indicated The dialysate is chosen to match D B serum osmolality & to correct any Q for conditions refractory to medical therapy: Q · A: (usually severe metabolic) blood chemistry abnormalities; e.g:

FLOW Anticoagulant

· E: derangements ������ + ���������� = � ���/� FLOW Dialysate reversal (, hypercalcemia, etc) EFFLUENT DIALYSATE DIALYZER · I: Intoxications (APAP, , DIALYSATE FLOW RATE (QD) pressure is a countercurrent flow of dialysate BLOOD , carbamazepine, metformin, DIALYSATE AV , salicylates, thallium, through the dialyzer. Higher flow fistula Tunneled central , valproate, etc); see ExTRIP rates enable greater clearance of small molecules via diffusion. venous dialysis

guidelines FLUID catheter · O: Fluid Overload (pulmonary edema refractory to diuretics, uncontrolled DIALYZER is rigid case that encloses thousands of Dialysate REPLACEMENT Bubble hypertension, etc). Volume removal may semi-permeable polymer tubules. Blood flows through Pump detector also hasten liberation from ventilation. the tubules & dialysate flows in the opposite direction · U: Symptomatic (causing severe outside (countercurrent). Dialyzers differ in surface area, REPLACEMENT FLUID (RF) can be VASCULAR ACCESS can be permanent (such as an AV altered mental status, uremic , hydraulic permeability (KUF), permeability to medium used to restore fluid volume removed fistula or an AV graft) accessed using needles, semi-permanent bleeding diathesis, etc) sized molecules (flux of β2 microglobulin), & permeability by UF in the dialyzer. Replacement (a tunneled CVC), or temporary (such as a non-tunneled CVC). to small molecules diffusion (mass transfer coefficient) fluid can be given pre- or post-dialyzer. NB: The “arterial” (red) side describes blood coming out of the MODALITIES OF RRT IN THE ICU: patient; it does NOT mean that it comes out of an artery. IHD SLEDD (Sustained low CRRT (Continuous renal CRRT Mode Description Schematic (Intermittent HD) efficiency daily dialysis) replacement therapy) Slow continuous UF; UF removes fluid but provides almost 3-5 hr session using ~12 hr session using 24 hr (continuous) session using Description SCUF no clearance and does not correct pH; no replacement standard HD machine standard HD machine a CRRT machine fluid required. Corrects volume overload only. UF Typically done by dialysis RNs Typically done by CCRNs Logistics Continuous venovenous . Provides Requires fresh water & drain connections Uses sterile fluid bags CVVH convective clearance by filtering a large volume of blood; RF )

Replacement fluid restores volume lost. Corrects uremia, 17 Vascular Access Fistula/Graft or CVC Usually requires CVC Requires CVC a.k.a. UF - ( CVVHF) lytes, pH and can remove volume. 02 > 300 ml/min ~ 200 ml/min < 200 ml/min - QB / QD > 500 ml/min 100-200 ml/min <50 ml/min (depends on mode) Continuous venovenous hemodialysis. Provides diffusive CVVHD clearance by running dialysate opposite blood flow. No 2021 Highest; ideal for Low; ideal for slower correction replacement fluid used. Gently corrects uremia, lytes, pH Dialysate Clearance Moderate ( v1.0 hyperK or toxins of abnormalities & fluid removal Continuous venovenous hemodiafiltration. High clearance Hemodynamics Hypotension common Causes less hypotension Causes the least hypotension RF achieved using both UF & dialysate flow (both convection SA3.0 CVVHDF - Risk of disequilibrium Risk of hypoPhos, unclear Thrombosis risk, immobility, & diffusion). Replacement fluid used. Allows fluid removal UF Dialysate Other risks and correction of electrolyte/pH. Good for toxin removal. syndrome med pharmacokinetics higher cost BY CC