Renal Flashcards
These factors will result in prostaglandin synthesis by the kidneys
Renal ischemia, renal hypotension, and physiological stress
This common drug used for post-op pain relief should be avoided in those at risk for medullary ischemia. Why?
Ketorolac (Toradol) This is because it is a powerful NSAID, which drastically reduces prostaglandin synthesis, putting the kidneys at risk for ischemia
Low dose dopamine will do this, but not this
Will have positive inotropic effects, which increase UO. Will not decrease the incidence of ARF, dialysis, or mortality
The kidneys are able to autoregulate over this range of MAPs
80-180 Some say up to 200 Either way, kidneys are very sensitive to a reduction in MAP Also, may be higher than 80 if the patient has chronic HTN
Surgical stimulation can cause release of this hormone
ADH This will cause a drop in UO
This will cause aldosterone release
baroreceptor response to volume depletion
In hypotension, blood will be shunted (towards/away) from the kidneys
Away from the kidneys! Towards the vital organs
What ion are we concerned about in renal failure?
Floride. Free fluoride ions cause tubular injury and loss of concentrating ability (can result in ARF)
Ranking of volatile agent effects on the kidney
Methoxy>Enflu>Sevo>Iso>Des>Halo (MESID H)
We prefer the use of these IAs in renal failure patients
Iso and des These have negligible effects on renal function
This is the minimum amount of gas flow that should be given with Sevo
2L to prevent compound A formation
BUN > ___ is indicative of decreased GFR
50
These factors may cause GFR to rise despite a normal GFR
High protein diet GI bleed Febrile illness Dehydration
What is the most common cause of high BUN
CHF secondary to the reabsorption of BUN Low CO causes lows kidney perfusion. Kidneys try to correct perceived fluid deficit by reabsorbing urea.
There is a __-__ hour lag time after a change in GFR before the increase creatinine levels are seen
8 - 17
What test is the most reliable estimate of GFR?
Creatinine clearance
Why is anemia common in renal failure?
1) Decreased EPO production 2) Build-up of toxins decreases the lifespan of RBCs
Chronic renal patients will usually have an increased or decreased CO?
Increased to compensate for the anemia
Hemoglobin levels as low as __-__ are common for renal patients, so don’t freak out
5-8
Renal patients usually have fucked up coags. Which coags are fucked up and why?
PT, PTT, and bleeding time. These are fucked up because they have shitty vWF. Treat this by replacing vWF.
How can you treat the fucked up coags seen in renal dysfunction?
Replace the vWF! 1) Desmopressin .3-.4mg/kg over 30 min) - Desmopressin will increase the release of vWF from endothelial cells 2) Cryoprecipitate (remember that this contains factor VIII, XIII, fibrinogen, and whaddup –> vWF!)
The hyperkalemia seen in RF can result in these EKG changes
Peaked T waves, ST depression, prolonged PR interval and QRS complex, heart block, and V-fib
Hypermagnesemia resulting from RF can cause
Coma and CNS depression Prolongs the duration of NMBs
Why do we use a microdripper to give fluids in renal patients?
To make sure we don’t fluid overload them
Why does RF cause HTN?
1) Renin release by the diseases kidney 2) High intravascular fluid volume d/t inappropriate handling of sodium and water
RF can lead to ____ pericarditis and cause
uremic pericarditis tamponade
Hypocalcemia causes this on EKG
Prolonged QT
Digitalis toxicity produces this on EKG
Shortened QT and depressed ST
These meds are excreted via the kidneys unchanged and are contraindicated in RF
Gallamine (100% renal elimination) and phenobarbital
Is UO predictive of post-op renal insufficiency?
No
What can happen if you give too much fluid to your anuric renal patients?
CHF and pulmonary edema
UO during surgery should be maintained at this rate
0.5cc/kg/min If it falls, we can give 5mg of lasix
A 50% increase in plasma creatinine means
A 50% reduction in GFR
This is the source of creatinine
Skeletal muscle
We are concerned about K+ when it is over
5
When is vasopressin released?
Released by the posterior pituitary in response to high serum osmolarity and acts on the kidneys
This is the dose for low-dose dopamine
1-2mcg/kg/min
Effect of neuraxial anesthesia in renal dysfunction
• T4-T10 sympathectomy will decrease the release of catecholamines, renin, and vasopressin (ADH) o This is because we’re causing vasodilation and blocking the sympathetic response! o Make sure to pre-hydrate before placement! • Key to maintenance of renal blood flow and GFR is you have to maintain renal perfusion pressure – fluid boluses etc. o Remember that proper RBF is dependent on MAP
Effect of PPV on renal function, and how we can over come this
• The higher the PIP and PEEP the greater the decrease in RBF, GFR, and urine flow rate o Probably because PPV will decrease venous return and CO We can overcome this by hydrating.
Creatinine Clearance
Normal is 125mL/min •
What may a CXR show in the patient with renal failure?
• LVH o Determine presence of hypertensive cardiovascular disease • Pericardial effusion (from uremic pericarditis) • Uremic pneumonitis- RF patients have chronic pulmonary edema → fluid overload, shitty heart function, and leaky capillaries
Avoid these NMBs in renal failure
d-tubocurarine, metocurine, gallamine
What is the most common cause of death in renal failure?
Infection Make sure to use aseptic technique!!
IAs for RF
Halothane Avoid- High K+ & acidosis-> myocardial irritability Enflurane Avoid- fluoride concern Sevoflurane Controversial: some practitioners remain concerned regarding Compound A and fluoride Isoflurane/Desflurane Volatile agents ideal-no dependence on kidney for elimination Accelerated induction and emergence seen with severe anemia Anemia results in decreased solubility of the IA
Ventilation goals in RF
Hypoventilation exacerbates acidosis Hypercapnia predisposes to cardiac arrhythmias from acidosis Alkalosis shifts oxy-hgb curve to left- less O2 available to tissues Overall, we want to maintain normal acid/base balance Remember too that they are anemic and we want to do this to keep the O2 dissociation curve to the right!! Remember that high PIP and PEEP will decrease RBF
This is the pressor of choice for renal pts
Ephedrine
What’s the deal with H2 blockers and renal failure?
H2 blockers are highly dependent on renal excretion
When does cystoscopy require more than local anesthesia?
If the bladder if being inflated (consider RA or GA)
Lithotomy position for cystoscopy puts you at risk for these nerve injuries
All major legs nerves except LFC (Sciatic, common peroneal, femoral, saphenous, and obturator)
RA for cystoscopy
Need T10 block Spinal preferred d/t brief nature of the surgery Will not abolish the obturator reflex (can only be blocked by muscle relaxants, which we don’t use with a regional technique)
GA for cystoscopy
Short case (15-20 min) LMA ok to use
S/S associated with TURP syndrome
headache, restlessness, confusion, seizure, dyspnea, cyanosis, arrhythmias, hypotension with bradycardia
Irrigating fluids used for TURP
glycine, sorbitol, or mannitol
How to prevent TURP syndrome
Limit irrigating fluid height to 40cm above prostate (job of the urologist) Limit resection time to less than 1 hour
Treatment for TURP syndrome
EARLY DETECTION!! Fluid restriction Loop diuretic To correct fluid overload and hyponatremia Hypertonic solution if hyponatremia present. 100cc 3% saline over 1-2 hours. Administer based on patients serum sodium (Ideally >120) Hyponatremia occurs d/t large absorption of this fluid that doesn’t contain lytes Results in cerebral edema Treat seizures with midazolam, thiopental or phenytoin (if glycine used consider a trial of magnesium) Intubate if pulmonary edema has occurred (from volume overload)
Regional blockade level needed for ESWL
T6
Why is GA preferred for ESWL?
Ability to control diaphragmatic excursion (Jet ventilation)
Coagulation considerations in RF
o Increased bleeding despite normal PT, PTT, and Bleeding Time • Caused by release of defective von Willebrand factor • Rx- Desmopressin (0.3-0.4 mg/kg over 30 min) or cryoprecipitate o Blood warmer- set up and have ready to go
When is vasopressin released?
It’s released by the posterior pituitary in response to an increase in serum osmolarity
Something to remember before doing neuraxial anesthesia in renal failure
• T4-T10 sympathectomy will decrease the release of catecholamines, renin, and vasopressin (ADH) o This is because we’re causing vasodilation and blocking the sympathetic response! o Make sure to pre-hydrate before placement!
Kidney functions
Fluid, pH, ion homeostasis Waste removal- urea, uric acid, creatinine, meds, toxins Endocrine- RAAS system, EPO, 1,25 D3–> active vitamin D, Prostaglandin production
Hypovolemic urine production
SNS and angiotensin II–> vasoconstrictive decrease in GFR and increase in Na+ reabsorption Aldosterone increases Na+ reabsorption ADH increases H2O reabsorption
Hypervolemic urine production
ANP increases GFR via vasodilation Reduced SNS and angio II allow vasodilation and Na+ excretion Increased cap hydrostatic pressure discourages Na reabsorption Decreased aldosterone decreases Na reabsorption in the DCT and CD No ADH leads to H2O being impermeable to the CD
Normal renal autoregulation
about 80-200 mmHg
Most anesthetic agents lead to
Decreased GFR, UO, RBF, and e-lyte excretion All major kidney functions affected
Surg/Anesthesia effect on ADH, Aldosterone, RAAS system
Increase in ADH–> decreased UO Increase in Aldosterone from baroreceptors detecting volume depletion Hypotension (under 80mmHg) leads to a release of renin and further renal vasoconstriction
Prostaglandins have what effect on the renal system
Protective against renal ischemia Ischemia, renal hypotension, stress, promote their production Oppose action of angio II, SNS, ADH, Avoid ketorolac in pts at risk for medullary ischemia
Low dose dopamine is
voodoo medicine
T4-T10 sympathectomy will
Decrease catecholamines, renin, and ADH Need fluid boluses to maintain RBF and GFR
Which gas can create compound A
Sevo Maintain flows over 2L
Which gases have negligible levels of free fluoride ion from metabolism
Iso and Des Methoxy>Enflu=Sevo are the worst No evidence Sevo cause injury though
PPV
More PIP/PEEP, less RBF/GFR/UO Hydration will largely overcome this
Periop oliguria is defined as
Pre-op eval
HTN? DM, MI, CHF? Meds Dialysis- pre/post weight, how much fluid off, when was last, e-lyte status
Renal function tests
GFR: BUN (10-20mg/dl) Plasma Cr (0.7-1.5mg/dl) Cr clearance (110-150ml/min) Tubular function: Urine spec grav (1.003-1.03) Urine osmo (38-140mOsm/L)
BUN
Inverse to GFR, >50 is indicative of decrease GFR Not as sensitive as Cr Can be abnormal, but GFR ok due to- high protein diet, GI bleed, fever, dehydration
Plasma Cr
8-17 hour lag after a GFR change Suggestive of ARF 50% increase indicates 50% decrease in GFR
Cr clearance
Index of GRF Most reliable ESTIMATE of GFR (don’t forget about Inulin aka gold standard for calculating GFR) less than 25ml/min indicates moderate disease, less than 10 needs dialysis Disadvantage- needs 2-24hr urine collection
Chronic RF Hgb hovers around
5-8g/dl
PT, PTT, bleeding time in CRF, reason and Tx
increased bleeding despite normal PT, PTT, and BT- cause is defective vWF Give DDAVP 0.3-0.4mg/Kg over 30 minutes or cryo, also have blood warmer ready to go
Hyperkalemia common, what EKG changes does it produce
Peaked T, long PR, long QRS, ST depression HB and V-fib can result
HyperMg leads to
CNS depression and coma
high or low pH in CRF
low, can’t excrete H+ ions
CXR for
HTN CV disease, pericardial effusion, uremic pneumonitis
Dig tox EKG
Short QT, ST depression
Hypocalcemia EKG
Long QT
RF and drugs
Anemia, low serum protein, e-lyte changes, fluid retention, changed cell membrane dynamics all affect drugs Drugs excreted by the kidney unchanged are CONTRAINDICATED, like gallamine, phenobarbital
Common anesthetic drugs to use with caution in RF
Thiopental- high PB Midazolam- 60-80% renal clearance, high PB Dexmedetomidine- high PB
Opioid of choice in RF
Fentanyl Remi also ok
Bad opioids in RF
Meperidine, morphine, hydromorphone
Muscle relaxants to avoid in RF
d-tubo, metocurine, gallamine, pancur, pipecur, doxacur Vec, roc ok (30% renal), but may see longer effect
Effects of Anesthetics on Normal Kidney
- ADH release d/t surgical stimulation will ↓ U/O (and promote the reabsorption of H20)
- Aldosterone release → baroreceptor response to volume depletion
- Autoregulation may be affected under GA
- Lower limits of autoregulation around 80 mmHg
- Hypotension
- caused by agents shunts blood away from kidney
- Any ↓ in RBF causes release of renin → renal vasoconstriction & SNS stimulation further ↓ RBF
- with low pressure in anesthesia = get preferential efferent vasoconstriction so that the GFR is increased
- massive hypotension → get afferent vasoconstriction and dramatic decreased GFR
Extra caution with succs because
K is released! Only use if K is normal, but probably want to avoid it
