Exam 3 - Renal Assessment Flashcards
How is osmolar homeostasis maintained?
- Mediated by osmolality sensors in anterior hypothalamus
- Stimulates thirts via release of ADH from pituatary gland
How is volume homeostasis maintained?
- Mediated by the JGA
- ↓ in volume activates the RAAS → Na+/H2O reabsorption
What can cause someone to have a TBW > 60%?
Increased muscle mass
What degree of hypo-/hypernatremia would give you pause for surgery?
- < 125 mg/dL or > 155 mg/dL
- More concerned about acute changes in Na+; monitor trends
Some causes of hypovolemic hyponatremia?
d/t Na+ and H20 losses:
- Diuretics
- GI losses
- Burns
- Vomiting
- 3rd spacing
Some causes of euvolemic hyponatremia?
- Salt restriction
- Hypothyroidism
- Drugs
- SIADH
Some causes of hypervolemic hyponatremia?
- Renal failure
- Heart failure
- Cirrhosis
Why are 15% of hospitalized patients hyponatremic?
- Over resuscitated
- ↑ endogenous vasopressin
What are the most severe consequences of hyponatremia?
Seizures, coma, death
How would hyponatremia be treated?
- Treatment of underlying disease (look at volume status)
- Electrolyte drinks
- NS
- Hypertonic Saline: 80mL/hr over 15 hrs
- Diuretics
How quickly should you correct low Na+?
How often should you check serum levels?
- Do not exceed > 1.5 mEq/L/hr
- q4h
What might happen if you correct the sodium > 6 mEq/L in 24 hr?
Osmotic Demyelination Syndrome - leads to permanent neuro damage
What is the treatment for hyponatremic seizures?
3-5mL/kg of 3% NS over 20 min until seziures resolve
What are some causes of hypovolemic hypernatremia?
- Diuretics
- Post renal obstruction
- GI losses
- Sweating
- Burns
What are some causes of euvolemic hypernatremia?
- DI
- Insensible losses
What are some causes of hypervolemic hypernatremia?
Sodium Gains
- Hyperaldosteronism
- Cushing’s
- Sodium bicarbonate
S/S of hypernatremia?
- Restlessness
- Lethargy
- Tremor
- Seizures
- Death
Treatment of hypernatremia?
Hypovolemic: NS
Euvolemic: Water replacent (PO or D5W)
Hypervolemic: Diuretics
At what rate should you aim to correct hypernatremia?
< 0.5 mmol/L/hr and < 10 mmol/L/day
Aldosterone’s relationship to K+?
- Inversely affects K+ levels
- Causes distal nephron to secrete K+ and reabsorp Na+
Common causes of hypokalemia?
Not so common..?
- Renal losses: diuretics, hyperaldosteronism
- GI losses
- Intracellular shifting: alkalosis, beta agonists, insulin
- DKA (osmotic diuresis)
- HCTZ
- Excessive licorice - board question
S/S of hypokalemia?
- Muscle weakness/cramps
- Ileus
- Dysrhythmias (u wave)
Treatments for hypokalemia?
- Treat underlying cause
- PO K+ preferred over IV
- Avoid excessive insulin, bicarb, β agonists, hyperventilation, and diuretics
How much does IV K+ increase serum K+?
Every 10 mEq IV increases serum K+ by ~0.1 mmol/L
Causes of hyperkalemia?
- Hypoaldosteronism
- Succinylcholine
- Acidosis
- Cell death (trauma/tourniquet)
- MTP
S/S of hyperkalemia?
- If chronic, may not have symptoms
- Skeletal muscle paralysis
- ↓ fine motor movement
- Dysrhythmias
EKG progression with hyperkalemia?
- Peaked T wave
- P wave abscence
- Prolonged QRS
- Sine waves
- Asystole
How much does succinylcholine increase serum K+?
0.5-1 mEq/L
Hyperkalemia treatments?
- Dialyze w/i 24 hrs of surgery
- Calcium 1st treatment
- Hyperventilation
- 10 units IV insulin
- Bicarb
- Loop diuretics
- Kayexalate
Hyperventilation’s affect on pH?
each ↑ pH by 0.1 = ↓K+ by 0.4-1.5 mmol/L
Where is 99% of the body’s calcium stored?
Bone
What is physiologically active calcium and it’s normal value?
Ionized calcium - 1.2-1.38 mmol/L
What affects ionized calcium levels?
- Albumin and pH
- ↑pH/Alkalosis = ↑Ca++ binding to albumin (therefore ↓iCa++)
What hormones affect calcium levels?
- PTH: ↑’s GI absorption, renal reabsorption, and regulates bone/bloodstream levels
- Vitamin D: augments intestinal Ca++ absorption
- Calcitonin: promotes storage of Ca++ in bone
Causes of hypocalcemia?
- ↓PTH secretion
- Mg deficiency (required for PTH production)
- Low Vitamin D
- Renal failure (not responding to PTH)
- MTP (citrate in blood products)
Complication of thyroid/PT surgery?
Laryngospasm d/t hypocalcemia
Causes of hypercalcemia?
Most common: Hyperparathyroid (serum Ca++ < 11) and cancer (serum Ca++ >13)
Less common: Vitamin D intoxication, milk-alkali syndrome (excessive GI absorption), and sarcoidosis
S/S of hypercalcemia?
- Confusion
- Lethargy
- Decreased DTR
- N/V/abd pain
- Short QTi
Chronically can cause kidney stones
S/S of hypocalcemia?
- Parasthesia
- Irritability
- Hypotension
- Seizures
- Prolonged QTi
Causes and symptoms of hypomagnesia?
Causes: Decreased intake or absorption, renal wasting
Symptoms: Muscle weakness or excitation, seizures, VTach/Torsades
Treatments for hypomagnesia?
Dependent of severity of symptoms
Slow replacement if not urgent
Torsades/seizures → 2 g Mg sulfate
Causes for hypermagnesemia?
Very rare - d/t over treatment, eclampsia, pheochromocytoma
S/S of hypermagenesia at different serum levels?
4-5 mEq/L: Lethargy, N/V, Flushing
>6 mEq/L: HoTN, ↓DTR
>10 mEq/L: Paralysis, apnea, heart blocks, cardiac arrest
Treatment of hypermagnesemia?
- Diuresis
- IV calcium
- Dialysis
Location of kidneys (specifically)?
- Retroperitoneal between T12-L4
- Right kidney lower than left to accomodate for the liver
The kidneys recieve how much of the CO?
Where does most of it go?
Which part of the kidney is most vulnerable to ischemia?
- 20% of the CO
- Cortex gets 85-90%
- Medulla most sensitive to changes in BP
Role of calcitriol and prostaglandins?
Calcitriol: Maintains serum Ca++
PG’s: inflammatory mediators, cause vasodilation, maintain RBF
What is the best measure of renal function overtime?
Normal value?
GFR
125-140mL/hr - heavily influenced by hydration status
What is the best lab value for measuring GFR and acute changes?
Normal value?
Creatinine clearance
110-140 mL/min
Creatinine is freely filtered and not reabsorped
Normal serum creatinine?
When is it useful?
0.6-1.3 mg/dL (correlates with muscle mass)
Good for acute monitoring, need to know baseline
How is serum creatinine related to GFR?
- Inversely related
- Acutely, an double in serum creatinine and mean GFR has dropped by half
Normal BUN?
Causes of low and high BUN?
Normal: 10-20 mg/dL
Low BUN: malnourishment or volume diluted
High BUN: ↑protein diet, dehydrated, GI bleed, trauma, muscle wasting
What lab value is a good indicator of hydration status?
Normal value?
BUN:Cr ratio
10:1
BUN is reabsorped and Cr is not
Normal urine protein levels?
What do high levels indicate?
< 150 mg/dL
>750mg/day could suggest glomerular injury or UTI
What lab measures the nephrons ability to concentrate urine?
Normal values?
Specific gravity
1.001-1.035
What is a late sign of volume loss?
Decreased UOP
What defines oliguria?
< 500 mL/day
What can we monitor to assess for volume status?
- US for IVC collapsibility (>50% collapse = fluid deficit)
- CVP
- LAP/PAWP
- SVV (compares inspiratory and expirartory pressure; pt must be ventilated and in SR)
What is a hallmark finding of AKI?
Azotemia - buildup of nitrogenous products (urea, creatinine)
Some risk factors for AKI?
- Pre-existing renal dx
- Elderly
- CHF
- DM
- Sepsis (hypotension)
- IV contrast
- Major operations
4 diagnostic criteria for AKI?
- Serum Cr ↑ by 0.3 mg/dL in 48 hrs
- Serum Cr ↑ by 50% in 7 days
- ↓ in CrCl by 50%
- Abrupt oliguria (not always)
Physical S/S of AKI?
- Malaise
- Hypotensive
- Hypo/hypervolemic
- Asymptomatic
Causes of prerenal AKI?
- Hemorrhage
- Traume
- Surgery
- Sepsis
Anything that decreases renal perfusion
Causes of intrarenal AKI?
- Vasculitis
- ATN
- Contrast dye
Anything that caues injury to the nephron
Causes of postrenal AKI?
- Kidney stone (nephrolithiasis)
- BPH
Anything that blocks urine outflow (easiest to treat and most common)
Lab values that indicate preranal AKI?
Treatment?
BUN:Cr > 20:1
Tx: Restore RBF → Fluids, diuretics, maintain MAP (pressors)
Lab values indicative of intrarenal AKI?
- ↓ GFR (late sign)
- ↓urea reabsorption and ↓Cr filtration leads to BUN:Cr < 15:1
Neuro complications of AKI?
- Uremic encephalopathy
- Neuropathies
- Myopathies
- Seizures
- Strokes
CV complications of AKI in order of incidence?
- Hypertension
- LVH
- CHF
- Pulm. edema
- Arrythmias
Hematologic complications of AKI?
- Anemia (↓ EPO)
- PLT dysfunction
- vWF disruption from uremia - prophylactic DDAVP
Metabolic complications of AKI?
- Hyperkalemia
- Water/Na+ imbalance
- Hypoalbuminemia (renal loss)
- Met. acidosis
- Malnutritin
- Hyperparathyroidism (in OD to try to stimulate kidneys to reabsorb Ca++)
Volume status managemet for patients with AKI?
- NS preferred (no K+)
- Correct fluid, electrolyte, and acid/base imbalance pre-op
- Maintain MAP 20% of baseline
- Vasopressin > ⍺ agonists - preferentialy constricts the efferent arteriole (better for increasing RBF)
Why would we give sodium bicarbonate prophylactically to AKI pts?
- ↓ free radical formation
- Prevents ATN from causing renal failure
Leading cause of CKD?
When are seeing them in the OR?
- DM and hypertension
- Surgery for dialysis access
- Diabetic amputations/debridements
- Non-healing wounds
How does GFR change with aging?
Decreases by 10 mL/min/decade beginning at 20 yo
Describe the stages of CKD?
1 - Kidney damage with normal or increased GFR (>90)
2 - Kidney damage with midly decreased GFR (60-89)
3 - Moderately decreased GFR (30-59)
4 - Severely decreased GFR (15-29)
5 - Kidney failure (GFR < 15)
CV effects of CKD?
Treatments?
- Systemic HTN (cause and consequence): d/t ↑RAAS (↑Na+/H2O retention)
- Dyslipidemia (↑triglycerides and LDL) - can lead to slient MI from decreased sensation
- Tx: 1st = Thiazides, may need ACEi/ARB
Why are ACEi and ARB beneficial in CKD?
Anesthesia concerns?
- ↓systemic BP and glomerular pressure
- ↓proteinuria by reducing glomerular hyperfiltration
- ↓glomerulosclerosis
- Hold before surgery to prevent profound hypotension - have pressors on hand if not held
Hematologic treatments and risks for CKD?
- Exogenous EPO (goal is hgb of 10)
- Transfusion of blood products (can lead to sluggish circulation, acidosis, and hyperkalemia)
Indications for dialysis?
AEIOU
Acidosis
Electrolyte imbalance
Intoxication
Overload
Uremia
Best type of dialysis?
Leading cause of death for patients of dialysis?
- HD more efficient
- Infection (impaired immune system and healing)
Why might we be concerned for bleeding in patients with CKD?
Treatments for surgery?
Uremia inhibits vWF = bleeding
Assess coag function
Transfuse if needed
DDAVP - tachyphylaxis, choose wisely if multiple operations
Best NMB for CKD patients?
Nimbex - is not dependent on renal elimination
Why should you avoid giving lipid insoluble drugs to CKD patients?
Prolongs the medications duration of action d/t unchanged renal elimination - need renal dosing
Some drugs we give that are renally excreted?
- Phenobarbital
- Pancuronium/vecuronium
- Neostigmine
- Glycopyrrolate
- Atropine
- Hydralazine
- PCN
- Vancomycins
What 2 drugs should we avoid in CKD patients d/t their active metabolites?
Morphine - M-3 glucuronide/M-6 glucuronide (can cause profound resp depression)
Meperidine - Normeperidine has half life of 15-30 hrs → neurotoxicity
What K+ is acceptable for elective surgeries?
< 5.5 mEq/L
Why should we aim to blunt the SNS outflow in CKD patients in surgery?
Catecholamines activate ⍺1 receptors and constrict the afferent arteriole ↓RBF
