Flashcards in AKI and Dialysis Deck (30)
What are 2 main types of insults in AKI?
1) Acute ischemia --> Patchy lesions along proximal and distal tubules, basement cell membrane is affected and necrosis is present
2) Acute toxic --> Basement membrane usually left intact, tubular destruction ranges from swelling to necrosis, damage is generalized and widespread
What are the 3 main categories of AKI?
What is prerenal failure?
Physiological response to insult that occurs before blood reaches kidney.
Result in renal hypoperfusion, decrease GFR, oliguria.
Nephrons remain normal and can recover
What are causes of pre-renal failure?
Local causes: Emboli, thrombus, surgery, hepatorenal syndrome
General causes: Hypoperfusion, decreased CO
What is intra-renal failure?
Parenchymal damage to nephrons resulting from disease or nephrotoxic agents. Damage can involve both glomerulus and tubular epithelium
**ATN (Acute Tubular Necrosis)
What causes intra-renal failure / ATN?
Nephrotoxic or ischemic injury to the renal tubular epithelium. Damage can extend to the basement membrane
What are the differences between Ischemic vs toxic ATN?
Ischemic: Damage is irregular along PCT and DCT, failure of autoregulatory properties of afferent and efferent arterioles that regulate GFR. ***Basement membrane damaged and necrotic
Toxic: Some nephrotoxins are vasoconstrictors (contrast dye), uniform widedspread damage to tubules range from swelling to necrosis. ***Basement membrane not as severely injured
What is pathophys of ATN?
Tubular swelling, cast formation (cellular debris)
Obstruction decrease capillary BF
Ischemia, cell injury
Decrease O2, ATP
Decrease cell function
O2 free radicals attract Ca intracellularly
Decrease serum Ca
Why do AKI pts become anuric?
Glomerular pressure equals hydrostatic pressure.
Obstructions increase tubular hydrostatic pressure that eventually equals filtration pressure
What is postrenal failure?
Physiological response caused by disruption of urine flow from urinary tract to bladder.
Rare but accounts for most anuric cases.
What are the 4 stages of acute renal failure?
1) Initiation (onset phase)
2) Maintenance (oliguric / anuric phase)
What happens in initiation phase?
Time of onset to cell damage, decrease in GFR due to impaired renal BF. Glomerular filtrate backleaks into tissues.
Pt has fatigue, fluid retention, anemia, decreased UO
What happens in maintenance phase?
Oliguria, severe decrease GFR with excessive H2O retention leading to dilutional hyponatremia
Increased K --> due to decreased excretion, muscle breakdown
Increased H+ --> leading to metabolic acidosis
Anemia --> due to suppressed erythropoietin
Creatinine, urea, phosphate elevated --> Muscle breakdown and inability to excrete waste
Hypocalcemia --> Decreased gut absorption due to decreased Vit D activation in kidney and O2 free radicals attracting calcium intra-cellularly
Azotemia (Buildup of metabolic waste)
What happens in the diuretic stage?
GFR begins to increase, reabsorption might not follow for a while. Gradual increase in UO
May have polyuria and dehydration d/t INABILITY TO CONCENTRATE URINE
Kidneys can clear volume but not solutes
What happens in recovery stage?
GFR returns to 70-80% normal
BUN and Cr may never completely normalize
Final stage is ability to concentrate urine
What is the best imaging test for AKI?
What is medical management of AKI?
1) Prevention --> Avoid nephrotoxins, IV contrast
2) Correct causative agent
3) Maintain fluid balance --> Replacement vs restriction vs removal
4) Restore/maintain electrolyte balance (K, Na, Ca, Po4)
5) Manage nutrition
6) Medication --> DIuretics, vasodilators, inotropes, Ca+ ch blockers
How are electrolytes managed in AKI?
Increased K --> Diuretics, insulin/glucose, sodium bicarb, kayexelate
Decreased Na --> Fluid restriction vs hypertonic saline, dialysis
Decreased Ca --> Supplement Ca and Vit D
Increased Po4 --> From bones attempt to free Ca, decreased excretion. Administer aluminum hydroxide to bind with phosphate and excrete in feces
Nursing diagnosis for AKI?
Impaired oxygenation d/t: Anemia from loss of erythropoietin, poor g/e from fluid in alveoli
--> Suction, monitor ABGs, Hgb, give EPO, blood, diuretics, monitor fluid status
Skin breakdown d/t: Generalized pitting edema, altered skin perfusion, pruritis caused by uremic toxins
--> Skin care, turns, nutrition
What is the purpose of dialysis?
Remove excess electrolytes, fluid, and toxins from blood via filtering through a semi-permeable membrane.
Does NOT improve renal function, indicated when there is buildup or uremia leading to changes in pt condition
What are the basic principles of dialysis?
1) Diffusion (movement of solutes)
2) Osmosis (movement of water)
3) Hydrostatic pressure (force of fluid pushing out)
4) Ultrafiltration (removal of fluid from vascular space)
What is uremia and what is its effect?
Accumulation of substance in blood ordinarily eliminated in urine.
Decrease LOC, metabolic acidosis, increased PO4, K,Cr, BUN, decreased Ca
Causes pulmonary edema, CHF, positive fluid balance, drug toxicity
What are contraindications to HD?
1) Inability to obtain vascular access
2) Hemodynamic instability
What is the process of intermittent HD (IHD)?
Blood mechanically pulled from pt through PVC tubing system to dialyzer. Diffusion and ultrafiltration occurs, wastes removed and blood is pumped back to pt.
**Blood volume removed approx 250-300mls
Treatment lasts 3-4 hrs given every other day or daily
How does blood flow relate to dialysate flow?
Always counter-current, enhancing diffusion
Pros and cons of IHD?
Pros: Remove large amount of fluid volume, decreases cardiac workload, correct cardiac arrythmias d/t hyperkalemia, improve metabolic acidosis, pt can mobilize
Cons: Not for hemodynamically unstable, drops in BP, potential for bleeding, blood clotting in circuit results in loss
Nursing considerations of IHD
Monitor hemodynamics, pt may need inotropes or albumin, accurate I/Os, daily monitoring of lytes, pre-and post IHD K level, observe for bleeding
What is Continuous renal replacement therapy (CRRT)? Pros/cons?
For pts who cannot tolerate IHD.
100-200ml blood removed at once outside of body
Slower blood flow, continuous controlled removal
Continuous control of acid-base and lytes
Rate of fluid removal can be altered
Gentle dialysis for hemodynamically unstable
Unable to mobilize pt
Circuit clotting, issues
What is sustained low efficiency daily dialysis (SLEDD)?
Similar to IHD but lasts longer, done over 8-10 hrs, usually at night, does not interfere with mobilization. One HD nurse can monitor many pts