Renal reduced Flashcards
Major functions of the kidney
-
Maintains fluid and inorganinc ion balance
- volume, osmolarity, pH and mineral composition
- Na, K, Ca, Cl-, HCO3, H2O
-
Removes metabolic wastes and chemicals from the circualtion
- urea, hormones, medications, toxins
- Gluconeogenesis
-
Endocrine function/hormone secretion
- fluid balance = renin, prostaglandins, kinins
- RBC production = erythropoetin
- Bone = active vitamin D (1,25-dihydroxyvitamin D3)
How do the kidneys respond normally to changes in volume status?
Hypovolemia
- SNS stimualtion and angiotensin II → vasoconstriction → ↓GFR and ↑ Na+ reabsorption
- Aldosterone→ ↑ Na+ reabsorption
- ADH(Vasopressin)→ ↑ H2O reabsorption
Hypervolemia→ ↑↓
- ANP (Atrial nateuretic peptide) → ↑ GFR via vasodilation
- ↓ SNS and angio II leads to vasodilation and Na+ excretion
- ↑ capillary hydrostatic pressure discourages Na+ reabsobtion
- ↓ aldosterone = ↓Na reabsorption in distal tubule and coolecting duct
- ↓ADH (Vasopressin) = ↓H2O reabsorbtion at the collecting duct
Normal renal autoregulation and the impact of surgery
Autoregualtion of RBF and GFR occurs between:
- MAP of ≈ 80-200 mmHg
All agents and most anesthetic techniques WILL:
- ↓ GFR
- ↓Urine output
- ↓ Renal Blood Flow
- ↓ Electrolyte excretion
- This will effect all major functions of the kidney
- Indirect and direct stimulation/decreases SNS, circulatory and endocrine
- These effects are reversible at the end of the procedure
Effect of Anesthetics on Normal Renal function
- Surgical stimulation → ADH release→↓ UO
- Baroreceptor response to decreased volume leads to ↑ Aldosterone
-
Autoregualtion may be effected under GA
- Lower limits of autoregulation around 80 mmHg
- Hypotension caused by agents shunts blood away from kidneys
- Decreased RBF → leads to renin release → further renal vasoconstriction and SNS stimulation and FURTHER decreases in RBF
Prostaglandins and the renal system
- Protective against renal ischemia
-
Production of prostagladins stimulated via:
- renal ischemia and hypotension
- Physiologic stress
-
Prostaglandins oppose action of:
- angio II, SNS and ADH to compensate for a ↓ in RBF from physilogic stress
- Thus they INCREASE urine output
- Prostaglandin production dependent on phosphalipase A2 and cyclooxygenase
- Ketoralac inhibits these enzymes significantly and thus poses risk for those with renal insufficiency or at risk for medullary ischemia
Dopamine for renal protection
“Low Dose Dopamine”
1-2 mcg/kg/min → Does NOT decrease the incidence of acute renal failure, dialysis or mortality!!!!
that is old news!
BUT… it does have inotropic effect and diuretic activity!
Impact of spinal and Epidural Anesthesia on renal function
-
T4-T10 sympathectomy will:
- ↑ catecholamine release
- ↓ renin release
- ↓ ADH (Vasopressin)
-
GIVE fluid boluses
- this will maintain renal blood flow and GFR and thus maintain renal profusion pressure
Volitile anesthetics and nephrotixicity
Main concern = production of free fluoride ions via metabolism causing tubular injury & loss of concentrating ability → ARF
- Risk = Methoxyflurane > Enflurane > Sevoflurane > Isoflurane > Desflurane > Halothane
- Isoflurane & Desflurane: negligible levels → very low risk
-
Sevoflurane = controversial
- ↑ Free fluoride levels but NO clinical evidence of injury
-
Compound A = sevo degrades with low flow through CO2 absorber
- FDA recommends 2 L gas flow with Sevo
- NO clinical evidence of injury in humans, only RATS
(Eger et al. demonstrated transient changes in renal function has not been reproduced by subsequent studies)
Impact of poitive pressure ventilation on renal system
- The higher the PIP and PEEP the greater the decrease in RBF, GFR and UO
- ↓ Preload, ↓ CO and ↓ Arterial hydrostatic pressure will :
- increase SNS activation of the RAAS →Aldosterone and vasopressin which is
- ↓ Preload, ↓ CO and ↓ Arterial hydrostatic pressure will :
-
Hydration will largely overcome this
- Volume improves venous return, cardiac output and increases arterial pressure and thus increases renal profusion
Periop oliguria
Defintion
Casues
Urine output < 0.5 cc/kg/hour or < 30 cc/hour
- if they are not meeting this…must figure out the problem could be hypotension, dehydration, need lasix?
Causes of periop oliguria
-
Prerenal = ↓ renal blood flow
- hypovolemia, ↓ CO
-
Intrarenal = Acute tubular necrosis
- renal ischemia from prerenal casue, nephrotoxic drugs, release of hemoglobin or myoglobin (MH/blood products)
-
Postrenal = ↓ outflow
- BILATERAL ureter obstruction, bladder rupture
Pre-op eval
HTN? DM, MI, CHF? Meds Dialysis- pre/post weight, how much fluid off, when was last, e-lyte status
Renal failure and effects on the nervous system
- Uremic neuropathy
- Uremic encephelopathy
- distal symmetric mixed motor polyneuropathy
- In ESRD - paresthesias, hyperesthesias in feet and lower estremeties
Renal Labs
- BUN > 50 = indicative of decrease
- Inverse to GFR,
- GFR Not as sensitive as Cr
- Can be abnormal, but GFR ok
- due to- high protein diet, GI bleed, fever, dehydration
- Plasma Creatinine 0.7-1.5 = normal
- 8-17 hour lag after cnange in GFR
- Suggestive of ARF
- 50% increase indicates 50% decrease in GFR
- Cr Clearance < 25 ml/min = moderate disease
- Index of GRF
- Most reliable ESTIMATE of GFR
- (don’t forget about Inulin aka gold standard for calculating GFR)
- < 10 needs dialysis
- Disadvantage - needs 2-24hr urine collection
- Urine spec grav (1.003-1.03)
- Urine osmo (38-140mOsm/L)
Renal failure and infections
- Most common cause of death
- often originates as a pulmonary infection
- use Aseptic technique
Acute Renal failure
definition, diagnosis and types
Sudden deterioration in renal function
- Diagnosed by:
- Serum creatitne ↑ of > 0.5 mg/dL and a 50% ↓ in Cr Cl
-
3 categories:
-
Prerenal = ↓ RBF, ↓ CO, ↓ blood voume
- CHF, Shock syndromes
-
Intrarenal = abnormality in the kidney
- trauma, crush injuries, myoglobin accumulation
-
Postrenal = obstruction
- renal calculi
-
Prerenal = ↓ RBF, ↓ CO, ↓ blood voume
High risk patients for ARF following anesthesia
(think of categories →Pre-op conditions)
- # 1 factor = pre-op renal insufficiency
- Pre-op CHF or CAD
- Elderly
- ESLD
(then the Peri-op Events)
- Peri-op cardiac events! (inadequate BP/CO)
- Sepsis/emergency surgeries, Trauma (MODS)
- Hypovolemia
- Nephrotoxic exposure
(then think about the surgery types)
- Surgeries using cardiopulmonary bipass
- Aortic clamping
- Liver or kidney transplant procedures
- Nephrectomy procedures
Anesthesia Care and and Physiologic effects of Acute Renal Failure
- Only go to OR if it is an EMERGENCY
- GOAL = Keep MAP >65
Retention of water, waste products, and electrolytes in the blood and extracellualar fluid
- HTN, CHF and Pulm. Edema (can happen fast!)
- Diluted RBCs (HCT 20-30%)
- GI issues (bleeds, anorexia, nausea and ileus)
- Hyperkalemia (can be fatal)
- Metabolic Acidosis
- Neurological changes (confusion, coma)
- Uremia induce immune supression (Infection)
Goals of the dialysis patient (slide title)
-
AVOID infection and CV events
- 25% annual mortalitity rate for all dialysis patients
- PRESERVE vascular access (for fistula sites)
- AVOID non-dominant arm and upper proption of the dominant arm!
- Remember pre-op dialysis clears many medications!
- low molecular weight drugs (<90% proein bound)
- water solule drugs
Drug dosing in renal failure
- Pharmacy has guideline and formulas
- It is useful to know th Cr Clearance and GFR
-
GFR < 50 mL.min = Reduced doses of drugs excreted unchanged by the kidneys
- If no documented GFR it can be estimated
- significantly ↓ GFR is <10 mL/min
- Oliguric = GFR ≈ 5-15 mL/min
- If no documented GFR it can be estimated
-
Volume of distribution changes!
- no dialysis → water souble durgs will have a larger volume of distribution
- just had dialysis → Vd will be normal
- Half lives = may have to dose farther apart
-
Protein binding is altered
- Acidic drugs = LESS binding and MORE free fraction
- Basic drugs = MORE binding → may need to INCREASE the dose!
Renal Failure
Pre-medication considerations
-
Anticholinergics
-
Atropine & glycopyrrolate
- Potential for accumulation in multiple doses
- 50% of drug excreted unchanged in urine
-
Scopolamine:
- Usually not given d/t CNS effects
-
Atropine & glycopyrrolate
-
Benzodiazepines:
- Use shorter acting & titrate very carefully (avoid diazepam)
-
Midazolam
- 60-80% cleared by the kidneys in the form of active metabolite + highly protein bound.
-
GI drugs
-
Phenothiazine: Droperidol
- α-blocker → may accentuate hypotension
- Not a problem usually in small doses
-
H2 Blockers:
- Highly dependent on renal excretion
- Metoclopramide will accumulate in renal failure
-
Phenothiazine: Droperidol
Renal Failure
Considerations with Opioids
-
Drug of choice
- Fentanyl: in non-cardiac doses
-
Analaougs of Fentanyl
-
Sufentanil: DONT USE!
- no change in free fraction but pharmacokinetics unpredictable in renal failure
-
Alfentanil:
- ↓ protein binding, no active metabolite (in theory it is ok, but fentanyl is better)
-
Remifentanil:
- remifentanil acid metabolite (minimally active) no major clinical implications
-
Sufentanil: DONT USE!
-
Opioids with active metabolites
-
Meperidine: NEVER GIVE!
- normeperidine metabolite → toxic
-
Morphine: one dose OK… but avoid repeat dosing
- 6-glucuronide metabolite + highly protein bound →
-
Hydromorphone: one dose OK… but avoid repeat dosing
- hydromorphone-3-glucuronide
-
Meperidine: NEVER GIVE!
Renal failure
Considerations with induction agents
-
Thiopental:
- highly protein bound → free fraction can be 2X normal → causing an exaggerated response
-
Dexmedetomidine:
- highly protein bound
- longer lasting sedation (in recent study)
-
Propofol, Ketamine, Etomidate:
- no major clinical change in their pharmacokinetics
- consider BP drop/CV status to chose proper agent
-
Midazolam:
- 60-80% cleared by kidneys in form of active metabolite + highly protein bound
Renal failure
Considerations for Muscle Relaxants
AVOID!! Know this for boards :)
- D-tubocurarine, metocurine, gallamine
- Pancuronium, pipecuronium, & doxacurium
- Primarily dependent on renal excretion
- 60-90%
- Must monitor neuromuscular function closely
USE CAUTION!!
-
Succinylcholine: → Single dose OK if normal K+
- Gtt problematic→ active metab→ succinylmonocholine
- Remember… sux increases K+ 0.5-1 mEq/L
-
Vecuronium & Rocuronium→ Single dose OK
- 30% renal excretion → may see prolonged effect
BEST CHOICES!!!!
-
Atracurium, cis-atracurium, & mivacurium →
- normal dosing appropriate
- have the most predictable for offset!!
not in slides:
Atra and cis-atra = hoffman elimination (acidosis = longer DOA) mivacurioum = plasma cholinesterases
- mivacurioum = plasma cholinesterases
Renal Failure
Intubation considerations
-
AVOID Succinylcholine
- Unless its an RSI but you MUST know K+ level
- Succs ↑ K+ levels by 0.5-1 mEq/L
- A small dose of a non-depolarizing NMB does NOT alter release of K+ reliably
- USE Lidocaine to blunt stimulus
- May need β-blockers to control HTN
- Delayed gastric emptying (diabetes) & ↑ gastric volume → full stomach = RSI
Renal Failure
Postioning
- Hypocalcemia → prone to fractures
- Uremic neuropathies → prone to nerve injuries
- Distal symmetrical mixed motor and sensory neuropathy
- median nerve and common peroneal are most often affected
Renal Failure
Inhalational agents
Accelerated induction & emergence seen with severe anemia d/t ↓ solubility
Best agents to use
-
Isoflurane and Desflurane:
- Do not depend on kidneys for elimination
Contriversial
- Sevoflurane: → some practitioners remain concerned regarding Compound A & free fluoride ion
AVOID
-
Halothane:
- causes high K+ & acidosis → myocardial irritability
- Enflurane: → fluoride concern
Renal Failure
Mantinence of Anesthesia
-
Short acting opioid + O2 + Agent +/- N2O
- Opioids can accumulate
-
For persistant intra-op HTN:
- ↑ inhaled agent, NTG, hydralazine , ß-blockers (↑ DOA possible)
-
Ventilate to MAINTAIN NORMOCAPNIA
- VERY important!!!!!!!
- Hypoventilation exacerbates acidosis
- Hypercapnia predisposes to cardiac arrhythmias
-
Alkalosis shifts oxy-hgb curve to LEFT → less O2 available to tissues
- offsetting compensation
4.
- offsetting compensation
Renal Failure
Reversal agents
Renal excretion is the primary route of elimination
- Edrophonium (75%)
- Neostigmine (50%)
- Pyridostigmine (75%)
Renal failures effect on these drugs:
- Prolonged half life
- Prolonged at least as much as the relaxants
- Normal dosing is usually given
(Not on slides: Do NOT need to eliminate the glycopyrolate because it will also have a prolonged duration of action)
Renal Failure
Fluid Management
- USE pre-hydration in renal patients who are NOT on dialysis
- ½ NS or NS→ NO Lactated Ringers → has 4 meq/L of K+
- Use 500 ml bags & microdrip (60 gtts)
- Maintain urine output at 0.5 cc/kg/hr
- Lasix 1-5 mg if U/O drops
- Urine output is NOT predictive of postoperative renal insufficiency
-
Anuric patients
- display a narrow margin of safety for fluids
- CHF or Pulmonary Edema may develop postop if not careful with fluids
Renal Failure
Monitoring
-
Minor surgical procedures can be monitored by noninvasive means
- Do NOT measure BP in arm with fistula
- Invasive monitoring may be needed for diabetic with advanced renal disease
- A-line needed for major cases
-
CVP or PA pressures for cases with a large anticipated fluid shifts or blood loss
- bowel surgery
- Also consider TEE
Renal Failure
Regional Anesthesia
- Good to use d/t great vasodilation
- Caution with a coagualopathy (check coags)
- In combo with metabolic acidosis regional may ↓ seizure threashold
- No not use if they have an infection
-
Used for
- Placement of AV Fistula : Brachial Plexus Block/Sedation + Local
Renal Failure
Vasopressors
GOAL = adequate intravascular fluid volume & minimizing CV depression vasopressors are used sparingly
-
α-adrenergic:
- phenylephrine = greatest ↓ in renal circulation
-
β-adrenergic:
- ↑ myocardial irritability and NO renal vasoconstriction
-
AVOID hypotension with prevention techniques
- However in severe septic shock, severe hypotension ect, renal autoregulation is impired
- Norepinephrine may actually be renal protective if it increases MAP > 60mmHG
Renal Failure and general Anesthesia
Summary
- Renal patienst should have dialysis the day before or day of surgery
- NO LR → use K+ free solution and a microdrip (60 gtts)
- AV Fistula: do not use extremity for BP or IV
-
CV disease is likely:
- Step up your monitoring!
- A-line, Swan → Maintain LV preload
-
Treatment of Hypotension:
- Treat with a direct α (phenylephrine)
- but remember renal constriction
- β-can cause cardiac irritability
- Treat with a direct α (phenylephrine)
-
GI prophylaxis:
- H2 blockers (but they are not cleared very well)
- no metoclopramide
-
Muscle Relaxants:
- no/little renal elimination
Renal Failure
Post-op management
-
Recurarization can occur d/t ineffective metabolism of other drugs (antibiotics)
- Gentamycin
- HTN is common → treat w/ NTG & SNP
- ECG monitoring
- Continue O2
- Antibiotic Continuation
Endoscopy Cystoscopy
- Most common urologic procedure
- Indicated for:
- Hematuria (bleeding in the urine)
- recurrent urinary infections
- urinary obstruction (renal stones)
- Other surgeries performed under cysto bladder biopsies, extraction of renal stones, placement of ureteral stent
- Procedure:
- Endoscopy & Cystoscopy
- Endoscopy = visualize & evaluate the ureter, kidney, bladder, prostate & urethra to diagnose and treat renal calculi, hematuria, trauma, cancer
- Cystoscopy = passage of a rigid scope through the urethra into the bladder
- Can be done under MAC with 2% lidocaine jelly can be used (and can be done under MAC)
- Bladder distention requires regional or general anesthesia
- Done in Lithotomy position
Lithotomy position
Most common nerve injuries
- Common peroneal nerve injury
- Saphenous nerve damage
- Obturator and femoral nerve injury
- Sciatic nerve
Positioning considerations/risks
- Both legs need to come up together
- Decrease FRC and atelectasis possible
- Increased venous return may exacerbate CHF
- Bladder perforation
- May go unnoticed under GEN
- Consider if:
- unexplained HTN, tachycardia, hypotension
- Shoulder pain is referred bladder pain
- Fever/bacteremia
- Bleeding
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)
Cystoscopy
Anesthetic Techinque
Most often General with an LMA (if not a full stomach)
- Short procedure length (15-20 minutes)
- Most patients apprehensive
Regional anesthesia
- Spinal is preferred d/t faster onset
- Studies show no need to wait for spinal onset before moving into lithotomy
-
Need a T10 level block
-
Spinal (0.75% bupivacaine)
- (10-12 mg if > 1 hour) or (7.5 ml if < 1 hour)
-
Lumbar Epidural (1.5 - 2% lidocaine w/ epi 15-25ml)
- Supplement with 5-10 ml bolus as needed
- Local (2% lidocaine jelly with IV sedation)
-
Spinal (0.75% bupivacaine)
-
Sensory level T10 block
- Does not abolish obturator reflex
- electrocautery may stimulate obturator nerve d/t proximity of nerve to bladder wall
- Will see external rotation & adduction of thigh
- Can only block w/ muscle paralysis → but do NOT want to give MR with regional
TURP
Procedure
Types
Risks
Transurethral Resection of Prostate
-
most common GU procedures in men > 60
- Lateral and medial lobe of prostate removal alleviates urinary obstruction from BPH
-
Preceded by cystoscopy
- resecto-scope inserted into urethra/bladder allows both cutting and coagulation of tissue and vessels.
-
Three types
- M-TURP (monopolar) MUST irrigate with NON-electrolyte solution (problem = TURP syndrome)
- B- TURP (bipolar) can irrigate with 0.9% NS
- L-TURP (laser) NO fluid irrigation needed
-
Continuous irrigation is needed to
- Distend bladder
- Wash away blood and tissue
- Maintain visibility
-
Absorption of the irrigant can lead to
- Pulmonary edema
- Hyponatremia (can be fatal - sezures)
- Cardiac and retinal toxic effects
- Increased blood volume
- Hyperglycemia
- TURP syndrome
-
Hypothermia
- Results from Large volumes of irrigating fluids
- Warm fluids to body tem
TURP
Anesthetic Technique
- Position: Lithotomy w/ slight Trendelenburg
- Pre-op medication
- Sedation as needed for anxiety
- Antibiotics per surgeon/often:
- Gentamycin 80 mg IV slowly (can potentiate our NM blockade → may start w/ lower dose of Roc
-
EBL ≈ 500mls (2-4ml/min of resection time)
- Prolonged procedure? get a BG to check Hgb
- Consider Type and cross
-
General
- Acute hyponatremia from TURP syndrome may delay emergence from GA
-
Regional
- Spinal –technique of choice w/ M-TURP
- T-10 sensory block required
- Allows for monitoring of:
- accidental bladder perforation (shoulder pain)
- mental status ∆s d/t water intoxication/fluid overload (start to slur their words)
- ↓ risk of post-op venous thrombosis
- ↓ blood loss
- M & M: No difference between GEN and Spinal
TURP syndrome
What is it
Prevetion
Treatment
Irrigation opens venous sinuses in prostate & allows systemic absorption of irrigating fluid
- Usually caused glycine, sorbitol, or mannitol
-
M-TURP (monpolar = non electrolyte hyposmplar solution)
- Cant use electrolyte solutions because they disperse the electrocautery current
- B-TURP and L-TURP use NS = not an issue
Signs of hypo-osmolarity or low sodium:
- headache, restlessness confusion, seizure
- cyanosis, dyspnea,
- arrhythmias, hypotension with bradycardia,
Prevention of TURP Syndrome
- Height of irrigating sol. MUST be < 60 cm above surgical table
-
Limit resection time to less than 1
- Amount of fluid absorbed is proportional to surgical time
- Approx 20ml/min of resection time
- Longer case = increased risk
Treatment of TURP Syndrome
-
Early recognition is Key
- Look for fluid overload, lung sounds, seizures
- Fluid restriction
- Loop diuretic
-
Hypertonic solution if hyponatremia present
- 100 ml 3% saline over 1-2 hours
- Administer based on patient’s serum Na+ → ideally >120
-
Treat seizures with midazolam, thiopental, or phenytoin
- if glycine used consider a trial of magnesium
- Intubate
ESWL
Procedure
Pateint considerations
Extracorporeal Shock Wave Lithotripsy (ESWL)
- Disintegrate calculi in upper ⅔ of ureters/kidneys
- Shock waves focused at renal stones
- High energy units = 1st generation = patient in water
- Low energy unit = 2nd + 3rd = lithotrypsers w/o water bath
- small water-filling coupling device and tightly focused sound beam
Patient considerations
- Patients with pacemaker or AICD are at risk to develop arrhythmias
- turn off right before and turn on right after and have a backup pacer ready
- Shock waves synchronized to 20 ms after R wave
- During ventricular refractory period
- Bradycardia can prolong procedure as shocks are coupled to the R wave - may have to increase HR to make the procedure more efficient
ESWL
Anesthetic Management
- Immobilization is very important to limit shock to focal zone only
- Very loud = earplugs (Us and patient)
-
General (most frequently)
- Controlled Ventilation (controlled diaphragmatic excursion)
- Avoids exposure to loud noise
- Ligh GA with muscle relaxation
- Can use High frequency Jet ventilation
- General does not decrease the number of shocks or radiation exposure
-
Regional only if you can ensure immobility
- Continuous epidural most common T6 level required
- Disadvantage = inability to control diaphragmatic movement (stone moves in and out of field)
- Incidence of hypotension is higher secondary to the sitting position
- If using epidural avoid injecting air (loss of resistance with saline)
-
MAC (Monitored anesthesia care)
- Flank infiltration and Intercostal block with monitored anesthesia care w/ 3rd generation (still require immobilization)