Renal Replacement Therapy (RRT) - ICU One Pager Summary Indications (AIEOU): • A: Acidosis (usually severe metabolic) • E: Electrolyte derangements (hyperkalemia, hypercalcemia, etc) • I: Intoxications (APAP, Barbiturates, Lithium, carbamazepine, metformin, methanol, salicylates, thallium, theophylline, valproate, etc); see ExTRlP guidelines • O: Fluid Overload (pulmonary edema refractory to diuretics, uncontrolled hypertension, etc). Volume removal may also hasten liberation from ventilation. • U: Symptomatic Uremia (causing severe altered mental status, uremic pericarditis, bleeding diathesis, etc) Components of a Hemodialysis Circuit & Parameters Set: • Ultrafiltration (UF) is the filtration of water from the blood, driven by the transmembrane pressure the blood & effluent. • Blood Flow Rate (QB) is the flow rate of blood through the dialysis circuit. • Dialysate Solution is an isotonic fluid containing electrolytes, bicarbonate/acetate, glucose, & sometimes other small molecules. The dialysate is chosen to match serum osmolality & to correct any blood chemistry abnormalities. • Dialysate Flow Rate (QD) is a countercurrent flow of dialysate through the dialyzer. Higher flow rates enable greater clearance of small molecules via diffusion. • Dialyzer is rigid case that encloses thousands of semi-permeable polymer tubules. Blood flows through the tubules & dialysate flows in the opposite direction outside (countercurrent). • Replacement Fluid (RF) can be used to restore fluid volume removed by UF in the dialyzer. • Vascular Access can be permanent (such as an AV fistula or an AV graft) accessed using needles, semi-permanent (a tunneled CVC), or temporary (such as a non-tunneled CVC). Modalities of RRT in the ICU: • IHD (Intermittent HD): 3-5 hr session using standard HD rnachine • SLEDD (Sustained low efficiency daily dialysis): ~12 hr session using standard HD machine • CRRT (Continuous renal replacement therapy): 24 hr (continuous) session using a CRRT machine CRRT Modes: • SCUF: Slow continuous UF; UF removes fluid but provides almost no clearance and does not correct PH; no replacement fluid required. Corrects volume overload only. • CVVH: Continuous venovenous hemofiltration. Provides convective clearance by filtering a large volume of blood; Replacement fluid restores volume lost. Corrects uremia, lytes, pH and can remove volume. • CVVHD: Continuous venovenous hemodialysis. Provides diffusive clearance by running dialysate opposite blood flow. No replacement fluid used. Gently corrects uremia, lytes, pH • CVVHDF: Continuous venovenous hemodiafiltration. High clearance achieved using both UF & dialysate flow (both convection & diffusion). Replacement fluid used. Allows fluid removal and correction of electrolyte/pH. Good for toxin removal. by Nick Mark MD @nickmmark #Renal #Replacement #Therapy #RRT #managment #nephrology #CRRT #Modes #modalities
