Critical Care Nursing

Renal Outline: Interventions, Labs and Tests

Critical Care Nursing, The University of Iowa
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V. Interventions

A. Pharmacotherapy

1. Bumetanide (Bumex) - acts on the ascending limb of the loop of Henle to inhibit reabsorption of water and electrolytes.

Nursing Interventions

1. Monitor for signs of electrolyte imbalance
2. One or 2 daily doses appear to be more effective than small doses administered frequently.
3. May need potassium supplements or potassium-sparing diuretics. Watch for hypokalemia.
4. Concurrent use with aminoglycoside antibiotics may increase potential for ototoxicity.
5. Avoid use of indomethacin or probenecid.

2. Ethacrynic acid (Edecrin) promotes the excretion of water, sodium, chloride and other electrolytes by inhibiting tubular reabsorption, especially in the medullary and cortical portions of the acending limb of the loop of Henle.

Nursing Interventions

1. Administer with meals to reduce gastric upset.
2. Avoid using with neurotoxic drugs such as amikacin, gentamicin, vancomycin
3. Watch for hypokalemia. Concurrent use with corticosteroids can produce severe hypokalemia.

3. Furosemide (Lasix) - promotes excretion of water, sodium, chloride and other electrolytes by inhibiting tubular reabsorption, especially in the medullary and cortical portions of the ascending loop of the loop of Henle.

Nursing Interventions

1. Watch potassium levels.
2. Watch for hearing loss. Give with caution in patients receiving neurotoxic drugs (see Edecrin)
3. When giving IV push - give 10 mg/min.

4. Hydrochlorothiazide (Esidrix, Hydro-diuril, Oretic) - promotes excretion of water, sodium and chloride by inhibiting the reabsorption of sodium ions in the ascending limb of the loop of Henle and in the early distal tubule of the nephron. Thiazide diuretic.

Nursing Interventions

1. Watch for potassium depletion
2. Electrolyte imbalance may increase when used with steroids, corticotropin, or Ampho B.

5. Mannitol (Osmitrol) elevates blood plasma osmolality resulting in flow of water from tissues, including brain and CSF. Mannitol is not reabsorbed in the renal tubule, which increases osmolality of the glomerular filtrate, facilitates the excretion of water and inhibits reabsorption of Na, Cl, and solutes.

Nursing Interventions

1. Use with in-line IV filter

B. Hemodialysis - most widely used treatment for renal failure. Invented during WWII but not widely used until approximately 1960.

Hemodialysis replaces excretory functions of the kidney but not hormonal functions. Eliminates wastes, electrolytes and water by:

1. Passive diffusion - solutes pass through a semipermeable membrane from an area of high concentration to low.
• a. Factors which influence clearance capacity
  • i. Pore size of the membrane
  • ii. Concentration gradient of the dialysate,
  • iii. Surface area of the dialyzer

2. Convection (ultrafiltration) - water movement encouraged by establishment of a hydrostatic pressure force across a membrane (some solute passes also)

• a. Factors which influence:
  • i. transmembrane hydrostatic pressure
  • ii. surface area
  • iii. selective permeability of the membrane
• b. Indications
  • i. volume overload
  • ii. electrolyte imbalance
  • iii. contraindications to peritoneal dialysis
  • iv. uremic symptons
• c. Contraindications/disadvantages
  • i. Hemodynamic instability
  • ii. vascular access problems
  • iii. adherence to rigid diet
  • iv. disequilibrium syndrome
  • v. hepatitis
  • vi. muscle cramping
  • vii. bleeding tendancies due to anticoagulant used
• d. Types of vascular access:
  • i. Quinton or temporary double or single lumen catheters
  • ii. AV fistulas
  • iii. grafts (Gortex)
  • iv. shunts (Scribner)

D. Continuous Arteriovenous Hemodialysis (CAVHD) and Slow Continuous Ultra-filtration (SCUF)

Uses patient's arterial blood pressure to deliver blood to a low-resistance hemodialyzer primarily for water removal. Alternative for patients who are oliguric and require large quantities of parenteral fluids, such as hyperalimentation, antibiotics, or vasopressors. Also when other forms of dialysis are contraindicated.

1. Contraindications to SCUF or CAVHD
• a. inability to tolerate anticoagulation
• b. hematocrit greater than 45

2. Difference between SCUF and CAVHD:

• a. smaller volumes with SCUF, so control of uremia and electrolytes is impossible.

3. Advantages

• a. Better for cardiovascualr stability since the process of volume removal is slower
• b. Can be managed by critical care nurse rather than hemodialysis staff

4. Disadvantage:

• a. limited ability to remove wastes and excess solutes
• b. need arterial and venous access

VI. Labs and Tests

A. Urea - an end-product of protein metabolism. Urea rises with high-protein diet, excessive tissure breakdown, or in presence of GI bleeding (blood protein broken down in the intestine and urea absorbed into the blood). Kidneys regulate BUN levels, filter urea in the glomeruli and reabsorb it in the tubules.

*BUN increases during dehydration

*Excretion is markedly decreased when GFR drops. (Longer the tubular fluid remains in the kdiney, the greater the reabsorption of urea into the blood.)

B. Creatinine - product of creatine metablism inmuscle. is filtered in the glomeruli, but not reabsorbed in the tubules. Therefore, blood values depend closely on GFR.

*Normal cretinine level is proportional to muscle mass. ex: smallwoman - 0.5 mg/100 ml blood, man - 1.0 mg/100ml, muscular man - 11.4 mg/100ml

*If value doubles, GFR - and renal function - probably have fallen to half of normal state.

*If value triples - suggests 75% loss of renal function.

*Values of 10 mg/100 ml - 90% loss of function

C. Urinalysis - Normal urine contains metabolic wastes and little, if any, plasma proteins, blood cells, or glucose.

Casts - molds of distal nephron lumen. Tamm and Horsfall mucoprotein (gel-like substance) forms the matrix of casts.
Hyaline casts - contain Tamm and Horsfall mucoprotein, without cells. Develop when protein content of urine is high (such as nephrotic syndrome) urine osmo high, urine pH low.

D. Other Serum lab tests

1. potassium, phosphate - tend to increase in renal failure
2. Calcium, pH, bicarbonate - tend to decrease in renal failure.

E. Cystoscopy - visualize the urethra, bladder, and ureteral orifices. Biopsy specimens, small stones, lesions, small tumor, and foreign bodies can be removed from urethra, bladder, or ureters by this means.

F. Radiologic exams

1. Computerized axial tomography (CAT) delineate tissue at any level. May be used to outline kidney and detect tumors therein.
2. Radiopaque iodine contrast medium - allows for visualization of urinary structures. Dye can be introduced into urinary system or into a vein.
3. Intravenous pyelogram (IVP) - allows for x-ray visualization of renal calyces, renal pelvis, and ureters as dye is excreted by the kidneys.
4. Retrograde pyelography - cystoscope is used to introduce dye into the ureters.

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Last Modified: January 22, 1997