Kidney Function, Injury & related medication

• Acute kidney injury (AKI) occurs in the ritoperitoneal area, between T12 and L3.
• Renal colic (kidney pain) radiates to the toes and is related to kidney issues; the right kidney sits lower than the left due to the liver.

Kidney Function and Injury

• Kidney functions include waste excretion, blood purification, and urine production, with measures of urine output, phosphate, urea, and creatinine levels indicating kidney health.
• Kidney injury can lead to fluid overload, causing shortness of breath and impacting blood pressure regulation via the renin hormone.
• Chronic kidney disease may require dialysis and result in low hemoglobin levels.
• ARBs (angiotensin II receptor blockers) and erythropoietin (EPO) are relevant in kidney function, where the kidney's failure to produce erythropoietin necessitates intervention.
• Renin increases blood pressure, and erythropoietin is necessary for red blood cell production.
• Creatinine indicates protein breakdown, while blood urea indicates muscle breakdown, both key waste products the kidneys filter.
• Kidneys filter approximately 1.50 liters of blood in 24 hours, with each cycle taking less than an hour.

Nephrons and Urine Production

• Nephrons perform blood filtration; the glomerulus within the nephron is responsible for filtering the blood.
• After purification, urine flows through the renal pelvis to the bladder.
• Urine travels from the bladder through the urethra for excretion.
• The bladder has a capacity of about 750ml.
• Micturition (urination) is controlled by the center of the pons and involves both voluntary and involuntary muscles.

Acute Kidney Injury (AKI) Details

• Acute Kidney Injuries cause include waste accumulation due to dehydration, diarrhea, and vomiting, along with elevated BUN and creatinine levels and low urine output.
• Prerenal AKI Causes: severe dehydration, heart failure, and low cardiac output, all leading to low blood pressure which damages the kidney.
• Glomerular damage leads to blood waste accumulation, increased BUN and creatinine, azotemia, and oliguria.
• Intrarenal AKI occurs inside the kidneys and is caused by nephrotoxic substances like certain medications (e.g., "-mycin" drugs, metformin, IV contrast). Metformin should be stopped prior to CT scans, and kidney lab values should be checked.
• Postrenal AKI involves obstruction of urine flow.
• Myoglobin release due to prolonged immobility can lead to AKI.
• Acute kidney injury can be reversible with proper management, unlike chronic kidney disease, which is irreversible.

Etiology and Clinical Manifestations of AKI

• AKI etiology includes the need for kidney perfusion, hypovolemia can lead to acute injury.
• Antibiotics require renal lab monitoring becausethe kidneys filter these.
• Reversing AKI is possible, assessing kidney function to determine the extent of loss.
• Diuretic phase is an important phase in recovery.

Clinical Manifestations

• Oliguria phase involves urine output less than 400ml per day, with dark urine potentially containing casts, RBCs, and WBCs, lasting 10-14 days.
• During the oliguria phase, edema and fluid overload signs include heart failure, crackles, labored breathing, low oxygen saturation, hypertension, low heart rate, and JVD.
• Fluid retention can lead to pulmonary edema.
• Metabolic acidosis occurs due to impaired kidney function, resulting in Kussmaul respirations.
• Hyponatremia (low sodium) can cause cerebral changes, including altered consciousness.
• Hyperkalemia (excess potassium) is often asymptomatic but results from the kidneys' impaired ability to excrete potassium.
• AKI also presents with changes in leukocytosis, elevated BUN and creatinine levels, and neurologic disorders like fatigue, difficulty concentrating, seizures, stupor, and coma.
• Nursing care includes monitoring fluid urinary output, neurological changes, and safety, especially related to hyperkalemia and dietary potassium intake.

Diuretic Phase

• All electrolytes tend to be low, leading to dehydration as nephrons recover; monitor for hyponatremia, hypokalemia, and dehydration, with daily output of 1-3 liters.

AKI Treatment

• IV fluids treat blood loss, but edema is a concern.
• Vancomycin levels should be monitored due to its nephrotoxic effects.
• Lab monitoring includes sodium, potassium, BUN, and creatinine levels.
• Ultrasounds are used to check for kidney stones.
• Biopsies determine the degree of kidney damage for final diagnosis.
• CT scans without IV contrast are preferred to prevent further kidney damage.
• Medication history is important, with caution advised for metformin, "-mycin" antibiotics with long-term use, and contrast studies.
• Fluid management, including Lasix (furosemide) and mannitol, is crucial in oliguria cases due to fluid overload.

Managing AKI Complications

• Avoid potassium administration and restricting food high in potassium.
• Administer IV insulin (10 units) with dextrose to shift potassium into cells.
• Sodium bicarbonate manages metabolic acidosis.
• Calcium carbonate is also used in treatment.
• Sodium Kayexalate helps eliminate potassium through diarrhea
• Avoid Kayexalate if bowel sounds are absent to prevent bowel necrosis; the goal is to eliminate potassium through feces.

AKI and Dialysis

• If a patient with massive blood loss-induced AKI presents with high potassium and BUN levels, creatinine elevation, and metabolic acidosis, and doesn't respond to initial treatments with sodium bicarbonate, fluids, and Lasix, temporary dialysis may be necessary.
• Rapid nephrology consultation for emergency access is required for temporary dialysis to prevent death.
• If a patient has low BP during AKI treatment, continuous renal replacement dialysis (CRRT) may be used instead of standard dialysis.
• Renal replacement therapy (RRT) may be initiated and continued in intensive care.

Nutrition and Monitoring

• Nutritional therapy involves restricting sodium and potassium intake, with protein intake not restricted.
• Vital signs, fluid intake and output, mental status, heart rhythm, daily weight, and electrolyte levels should be closely monitored.
• Replace significant fluid losses, administer diuretic therapy for fluid overload, and avoid nephrotoxic medications.

This lesson explains kidney function related to waste excretion, blood purification, and urine production. It highlights how kidney injury can lead to fluid overload, shortness of breath, and impact blood pressure regulation. The lesson also touches on treatments like dialysis and medications like ARBs and erythropoietin for chronic kidney disease.