Renal Flashcards
6 hormones secreted by the renal system
Aldosterone Anti-diuretic hormone Angiotensin Atrial Natriuretic Factor Vitamin D Erythropoietin
Location on spinal column of kidneys
T12 - L3
Location of right vs left kidney
Right kidney is slightly lower than the left because of hepatic displacement
Hilus of the kidney
Recessed fissure in medial margin of kidney, concaved shape
-Renal artery, renal vein, nerves, lymphatics, and ureters enter/exit the kidney here
Regions of kidney: Outer ___, inner ____
Outer cortex
Inner medulla
-Divided into wedges called pyramids
-Pyramid bases are directed toward cortex, apexes converge toward renal pelvis
Path filtrate takes through the nephron
Nephron=functional unit of kidney, 1,250,000 of them in each kidney
- Afferent arteriole
- Glomerulus - Efferent arteriole
- Bowmans capsule
- Proximal convoluted tubule
- Loop of henle
- Distal convoluted tubule
- Collecting duct
Cortical vs juxtamedullary nephrons
Cortical: 70-80%
-Have short loop of henle, extend only to superficial regions of medulla, lack a thin ascending limb
Juxtamedullary: 20-30%
-Important in concentrating urine
-Renal corpuscles located near the medulla, loops of henle project deeply into medulla
Blood flow to kidneys (mL/min, % CO)
1100-1200 mL/min
20-25% CO
Where blood goes after it leaves the renal vein
Inferior vena cava
Renal fraction
Cardiac output that passes through the kidneys -CO ~5600 mL/min -RBF ~1200 mL/min Normal renal fraction = 21% -Can vary from 12-30%
Regulation of renal blood flow equation
=(MAP-VP) x VR
VP=Venous pressure
VR=Vascular resistance
Regulated by:
-Autoregulation: Afferent arteriole vasodilation and myogenic mechanisms
-Neural regulation: SNS innervates afferent and efferent arterioles
-SNS stimulation will decrease RBF
MAP that autoregulation can maintain RBF between
50-180 mmHg
-Remains 1200 mL/min to both kidneys
GFR
Glomerular filtration rate
- Quantity of glomerular filtrate formed each minute in the nephrons
- Most important index of intrinsic renal function
- 125 mL/min - 180 L/day
- 99% of this is reabsorbed from the renal tubules
Juxtaglomerular complex
Regulates GFR
Distal convoluted tubule
-Lie between afferent and efferent arterioles
-Cells here that come into contact with the arterioles=macula densa
Smooth muscle cells of the afferent and efferent arterioles consist of juxtaglomerular cells
-Contain renin
Structure is anatomically arranged to allow fluid in the distal tubule to alter afferent or efferent arteriolar tone - regulate GFR
SNS stimulation affect on juxtaglomerular cells
SNS/decreased Na and Cl delivery to macula densa -> renin release from juxtaglomerular cells
- Renin -> angiotensinogen from liver -> angiotensin I -> angiotensin II in lung with ACE
- Angiotensin II = efferent arteriole contriction (vasocontriction in general) = increased pressure in glomerulus = increased GFR
Proximal tubule major function
Active transport of Na(Na/K/ATPase)
- Water, lytes, and organic substances are cotransported with Na
- Angiotensin II and Norepi will enhance this Na reabsorption
Loop of henle primary function
Descending and ascending portions
- Maintain a hypertonic medullary interstitum
- Indirectly provide the collecting tubules with the ability to concentrate urine
- 15-20% of Na is reabsorbed
- Descending limb: solute and water reabsorption is passive, follows concentration and osmotic gradients
- Ascending thick segment: Na and Cl absorbed in excess of water
- Countercurrent mechanism: Establishes a hyperosmotic state - vital for water conservation
Distal convoluted tubule primary function
Na reabsorbed under influence of aldosterone
K concentration controlled
-Secreted into lumen in exchange for Na
*Only permeable to water in the presence of ADH
Collecting tubule primary function
Acidifying urine (H secretion)
Aldosterone and Na reabsorption
ADH determines permeability of water
-Dehydration: Increased production of ADH
-Adequate hydration: Decreased production of ADH
Juxtaglomerular apparatus primary function
Contain renin
Innervated by Beta-1 adrenergic SNS
-Decreased GFR=over absorption of Na and Cl - decreased delivery to macula densa - AA vasodilates - increased RBF
Aldosterone
- Produced: Adrenal cortex
- Increases Na/H2O reabsorption
- Regulated: K concentration (strongest trigger) in ECF, renin-angiotensin, ECF Na concentration
- Target: Distal nephron
ADH
- Synthesized: Hypothalamus
- Release: Posterior pituitary
- Regulated: Osmoreceptors near hypothalamus sense ECF concentration, inhibited by stretch atrial barorecptors
- Target: Distal tubule, collecting ducts, impermeable to water without ADH, with ADH-water is reabsorbed
Renin and Angiotensin
Renin released from
-Beta-adrenergic stimulation
-Decreased AA perfusion
-Decreased Na
Acts on hepatic angiotensin - angiotensin II in lungs
-Vasoconstriction
-Stimulates aldosterone release from adrenal cortex
Atrial natriuretic factor
- Produced: Cardiac atria
- Stimulus: Stretch/distention/increased pressure in atria
- Effect: Increased Na excretion, urine flow, RBF, GFR
- Potent diuretic
Erythropoietin
- Created: Kidneys
- Effect: Stimulates RBC production
Prostaglandins
Modulate the renal effects of other hormones, protective vasodilators during periods of hypotension and ischemia PGE2 -Vasodilator Thromboxane A2 -Contraction of vascular smooth muscle
Vitamin D
-Vital role in calcium metabolism
% that anesthesia can depress renal function
30-40%
-Directly correlated with degree of sympathetic block and BP depression, impairment of autoregulation
Renal effects in general vs regional anesthesia
Both = Reversible decrease in RBF, GFR, urinary flow, Na excretion
- Usually less pronounced during regional anesthesia
- Indirect, mediated by autonomic and hormonal responses to surgery
Anesthetic drugs ___ renal perfusion, ____ vascular resistance
Decrease renal perfusion
Increase vascular resistance
Drugs that stimulate catecholamines cause an ___ in renal vascular resistance, vaso____, and ____ RBF
Increase in renal vascular resistance
Vasoconstriction
Decreased RBF
Inhalation agents ___ renal vascular resistance in response to a ___ SVR
Increase renal vascular resistance
Lower SVR
Neurologic effects in periop period
Increased SNS tone occurs periop from anxiety, pain, light anesthesia, surgical stimulation
- > Increased renal vascular resistance
- > Activates hormonal systems -> reduced RBF, GFR, UOP
Endocrine stimulation periop
Common component of stress response
- > Increase epi, norepi, renin, angiotensin II, aldosterone, ADH, ACTH, cortisol
- At least party responsible for transient fluid retention seen postop in many patients
Inhalation agent nephrotoxicity
Methoxyflurane - old agent no longer used
-Release of inorganic fluoride ions in metabolism = cause
-Fluoride alters renal concentration by interfering with active transport of Na and Cl
-Potent vasodilator, inhibits ADH - interferes with urine concentrating ability
-2-5 days postop pts had high nonconcentrated UOP - fluid/lyte imbalances - death
-AKA Penthrane polyuria
None of the modern agents are nephrotoxic
Sevoflurane and renal toxicity
5-8% metabolism - metabolites = fluoride and HFIP (1/4th Fl production as methoxyflurane)
-Compound A only fund in animal studies, not humans, FDA recs 1LPM FGF if <1 hour, 2LPM if >1hr
Nonoliguric vs oliguric vs anuric AKI
Nonoliguric: UOP >400 mL/day
Oliguric: UOP <400 mL/day
Anuric: UOP <100 mL/day
How many ICU patients will develop AKI after a major surgical procedure
36%
Most common cause of ESRD
Glomerulonephritis
-Due to deposition of antigen-antibody complex in the glomeruli
Diuretics for AKI prevention
Increases UOP but doesn’t decrease chronic renal dysfunction or mortality
-Must be balanced with fluid administration to prevent hypotension and hypoperfusion
Key approaches to treat AKI
Administer volume to achieve euvolemia
Improve CO by afterload reduction
Normalize SVR
CKD characteristic
GFR<60 mL/min for >3 months 5 stages... 1: Kidney damage, GFR normal 2: Kidney damage, GFR 60-89 3: GFR 30-59 4: GFR 15-29 5: ESRD, GFR<15
Nephron function with aging
Normal - nephron function <10% for each decade of life
-Renal insufficiency is common in the geriatric population
Most important source of information in preop assessment for renal disease patients
Medical history
-History arousing suspicion should lead to a more thorough evaluation of renal function
What medication to use if excessive bleeding is present preop for ESRD patients
Desmopressin
Ideal weight preop for ESRD dialysis patients
1-2 kg above “dry weight”
-Dialyze 24 hours or less before surgery
Creatinine clearance
-Specific test of GFR
-Most reliable assessment tool for renal function
-Measures glomerular ability to excrete creatinine into urine for a given plasma concentration
=(urine creatinine x urine volume) x serum creatinine (24 hour urine specimen needed)
-Normal: 95-150 mL/min
Urinalysis tests to look for
Specific gravity: renal capacity to excrete concentrated or dilute urine
Urine osmolality: indicative of tubular function
Proteinuria: indicates severe glomerular damage
Urinary pH: ability to acidify urine
CKD pharmacological implications (volume of distribution, protein bound drugs, acidosis, metabolites, anema, uremia)
- Larger volume of distribution
- Highly protein bound drugs will have greater effect
- Acidosis-more unionized drug available (cross lipid membrane faster)
- Metabolites can accumulate and become physiologically active
- Anemia increases CO/delivery to brain
- Uremia alters integrity of BBB, increased sensitivity
CKD effect on ketamine, sodium penthothal, Propofol, benzos, narcotics, inhalation agents, muscle relaxants
Ketamine: Metabolites accumulate, may worsen HTN (catecholamine release)
Sodium penthothal: Highly protein bound, exaggerated prolonged effect
Propofol: Hyperdynamic state - increased dose
Benzos: Greater sensitivity if hypo-albuminemic
Narcotics: Increase volume of distribution, exaggerated response, slow elimination half-life
-Morphine: May have prolonged respiratory depression
-Meperidine: Norperidine metabolite, seizures, respiratory depression
-Sufentanil: highly variable clearance and half life
Inhalation agents: Avoid methoxyflurane
Muscle relaxants:
-Succinylcholine: Increased K, increased block (accumulation of metabolites)
-Roc, vec, mivacurium: Block may be prolonged, unpredictable
-Atracurium, cis: Drug of choice, predictable (Hoffman elimination)
Acidosis with regional anesthesia
Will affect block
- Faster onset
- Shorter duration
Preop fluid and intraop UOP for CKD
Preop hydration with NS: 10-20 mL/kg
0.5-1 mL/kg/hr UOP
Loop vs osmotic vs aldosterone antagonist vs thiazide diuretics
Loop: Lasix
-Inhibits reabsorption of Na and Cl, augments secretion of K
Osmotic: Mannitol, isosorbide
-Inhibits reabsorption of water and Na, increase osmolarity of blood - increased secretion of water
Aldosterone antagonist: Spironolactone
-Offsets loss of K with thiazide diuretics, watch for high K
Thiazide: Chlorothiazide, hydrochlorothiazide
-Used for essential HTN
-Inhibits reabsorption of Na
-Side effects: Hypokalemia, muscle weakness, potentiation of NDMRs
Most common position for urologic procedures
Lithotomy
Cystoscopy
Camera into bladder
-Spinal MAC, MAC, GA
Brachytherapy
Radioactive implants inserted into tissue
- To treat ca (prostate esp)
- Spinal, epidural, GA
Extracorporeal shock wave lithotripsy
High energy shock waves passed through body to break urinary stones
- Water immersion vs dry (common dry now)
- Shock waves sync to R waves of heart (notify surgeon if CV issues)
- Anesthetic concerns if panc/hepatic damage, plt dysfunction
- Contraindicated: AAA, pregnancy, morbid obesity
- MAC, GA
Radical prostatectomy
Remove prostate gland, bladder neck, seminal vesicles, ampullae of vas deferens, pelvic lymph node dissection
Radical retropubic prostatectomy
Vertical incision below umbilicus
-High EBL (500) from dorsal vein
-Foley clamped on field, blood can mix with urine b/c bladder is open
Laparoscopic/Robotic
-Extreme Trendelenburg - venous congestion, ventilation difficulty
-Peripheral neuropathy risk
-Arms tucked, 2 PIVs present, possible A-line
Radical perineal prostatectomy
Extreme lithotomy position - shoulder braces on acromion process - high risk for nerve injury
- Less EBL than Radical retropubic prostatectomy
- Bleomycin patients (for ca): At risk for pulmonary insufficiency, oxygen toxicity, fluid overload
Radical nephrectomy
Excision of peri-nephritic fat and fascia, proximal 2/3 of ureter, para-aortic lymph nodes
- GA, epidural
- 2 PIVs, possible A-line
- Potential for high EBL especially if tumor is well vascularized (involvement with IVC=5-10%)
- Position: Supine or lateral with bean bag
- Fluid: NS/LR 6-8 mL/kg/hr, UOP >0.5 mL/kg/hr, use mannitol, lasix, or renal dose dopamine
- Concerns: Potential for pneumothorax, decreased venous return if pressure on vena cava, increased airway pressures (retraction of diaphragm)
Renal transplant patients goal SBP and CVP
SBP>100
CVP 10-15
Cystectomy
Removal of all or part of bladder, simple or radical
- GA, epidural
- Many patients are smokers, have underlying renal impairment
TURBT
Transurethral resection of bladder tumor
- Cysto with rigid scope
- GA or spinal
TURP
Transurethral resection of the prostate
-Spinal preferred - monitor for CNS signs of hyponatremia (TURP syndrome)
TURP syndrome
Hyponatremia dur to large amounts of irrigation used, venous sinuses are open - systemic absorption of irrigation fluid
- Spinal anesthesia is less likely to mask symptoms
- Some irrigations use NaCl and special cautery to avoid this
- Symptoms: periop or postop, headache, restless, confused, cyanosis, arrhythmias, hypotension, seizures (fluid overload, water intoxication)
- Treatment: Hypertonic saline, lasix
Treatment for hyperkalemia
Calcium chloride Hyperventilation Insulin Glucose Sodium bicarbonate
What patient population should osmotic diuretics not be used in?
CHF
-Get pulmonary edema
Diamox makes urine ___
Alkaline
