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Flashcards in Renal reduced Deck (43):
1

Major functions of the kidney

  1. Maintains fluid and inorganinc ion balance
    • volume, osmolarity, pH and mineral composition
    • Na, K, Ca, Cl-, HCO3, H2O
  2. Removes metabolic wastes and chemicals from the circualtion
    • urea, hormones, medications, toxins
  3. Gluconeogenesis
  4. Endocrine function/hormone secretion
    1. fluid balance = renin, prostaglandins, kinins
    2. RBC production = erythropoetin
    3. Bone = active vitamin D (1,25-dihydroxyvitamin D3)

 

2

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

3

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

4

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

5

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

6

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!

7

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

8

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)

9

Impact of poitive pressure ventilation on renal system

  1. 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 
  2. Hydration will largely overcome this
    • Volume improves venous return, cardiac output and increases arterial pressure and thus increases renal profusion

 

10

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

 

11

Pre-op eval

HTN? DM, MI, CHF? Meds Dialysis- pre/post weight, how much fluid off, when was last, e-lyte status

12

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

13

Renal Labs

  1. 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
  2. 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
  3. Cr Clearance 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
  4. ​ Urine spec grav (1.003-1.03)
  5. Urine osmo (38-140mOsm/L)

14

Renal failure and infections

  • Most common cause of death
  • often originates as a pulmonary infection
  • use Aseptic technique

15

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

16

High risk patients for ARF following anesthesia

(think of categories →Pre-op conditions)

  1. #1 factor = pre-op renal insufficiency
  2. Pre-op CHF or CAD
  3. Elderly
  4. ESLD

(then the Peri-op Events)

  1. Peri-op cardiac events! (inadequate BP/CO)
  2. Sepsis/emergency surgeries, Trauma (MODS)
  3. Hypovolemia
  4. Nephrotoxic exposure

(then think about the surgery types)

  1. Surgeries using cardiopulmonary bipass
  2. Aortic clamping
  3. Liver or kidney transplant procedures
  4. Nephrectomy procedures

17

Anesthesia Care and and Physiologic effects of Acute Renal Failure

 

  1. Only go to OR if it is an EMERGENCY
  2. 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)

 

18

Goals of the dialysis patient (slide title)

 

  1. AVOID infection and CV events
    • 25% annual mortalitity rate for all dialysis patients
  2. PRESERVE vascular access (for fistula sites)
    1. ​AVOID non-dominant arm and upper proption of the dominant arm!
  3. ​Remember pre-op dialysis clears many medications!
    • ​low molecular weight drugs (<90% proein bound)
    • water solule drugs

19

Drug dosing in renal failure

  1. Pharmacy has guideline and formulas
  2. It is useful to know th Cr Clearance and GFR
  3. GFR​ < 50 mL.min = Reduced doses of drugs excreted unchanged by the kidneys
    1. If no documented GFR it can be estimated
      • significantly  GFR is <10 mL/min 
      • Oliguric = GFR ≈ 5-15 mL/min
  4. Volume of distribution changes!
    • no dialysis → water souble durgs will have a larger volume of distribution
    • just had dialysis → Vd will be normal
  5. ​Half lives = may have to dose farther apart
  6. Protein binding is altered
    1. ​​Acidic drugs = LESS binding and MORE free fraction
    2. Basic drugs = MORE binding → may need to INCREASE the dose!

20

Renal Failure

Pre-medication considerations

  1. Anticholinergics
    • Atropine & glycopyrrolate
      • Potential for accumulation in multiple doses
      • 50% of drug excreted unchanged in urine
    • Scopolamine:
      • Usually not given d/t CNS effects
  2. 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. 
  3. 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 

21

Renal Failure

Considerations with Opioids

  1. Drug of choice
    • Fentanyl: in non-cardiac doses 
  2. 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 
  3. Opioids with active metabolites
    • Meperidine: NEVER GIVE!
      • normeperidine metabolite → toxic
    • Morphine: one dose OK…  but avoid repeat dosing
      • 6-glucuronide metabolite + highly protein bound → 
    • Hydromorphoneone dose OK… but avoid repeat dosing
      • hydromorphone-3-glucuronide 

22

Renal failure 

Considerations with induction agents

  1. Thiopental:
    • highly protein bound → free fraction can be 2X normal  →  causing  an exaggerated response
  2. Dexmedetomidine:
    • highly protein bound
    • longer lasting sedation (in recent study)
  3. Propofol, Ketamine, Etomidate:
    • no major clinical change in their pharmacokinetics
    • consider BP drop/CV status to chose proper agent
  4. Midazolam:
    • 60-80% cleared by kidneys in form of active metabolite + highly protein bound

23

Renal failure

Considerations for Muscle Relaxants

AVOID!! Know this for boards :)

  1. D-tubocurarine, metocurine, gallamine
  2. Pancuronium, pipecuronium, & doxacurium
    • Primarily dependent on renal excretion
    • 60-90%
  3. Must monitor neuromuscular function closely

USE CAUTION!!

  1. Succinylcholine: → Single dose OK if normal K+
    • Gtt problematic→ active metab→  succinylmonocholine
    • Remember… sux increases K+ 0.5-1 mEq/L
  1. Vecuronium & Rocuronium→ Single dose OK
    • 30% renal excretion → may see prolonged effect

​​BEST CHOICES!!!!

  1. 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

24

Renal Failure

Intubation considerations

 

  1. AVOID Succinylcholine
    1. Unless its an RSI but you MUST know K+ level
    2. Succs ↑ K+ levels by 0.5-1 mEq/L
    3. A small dose of a non-depolarizing NMB does NOT alter release of K+ reliably
  2. USE Lidocaine to blunt stimulus 
  3. May need β-blockers to control HTN
  4. Delayed gastric emptying (diabetes) & ↑ gastric volume → full stomach = RSI

 

25

Renal Failure

Postioning

  1. Hypocalcemia → prone to fractures
  2. Uremic neuropathies → prone to nerve injuries
  3. Distal symmetrical mixed motor and sensory neuropathy
    1. median nerve and common peroneal are most often affected

26

Renal Failure

Inhalational agents

Accelerated induction & emergence seen with severe anemia d/t ↓ solubility 

Best agents to use

  1. Isoflurane and Desflurane:
    • Do not depend on kidneys for elimination 

Contriversial

  1. Sevoflurane:  → some practitioners remain concerned regarding Compound A & free fluoride ion

AVOID

  1. Halothane:
    • causes high K+ & acidosis → myocardial irritability
  2. Enflurane:  →  fluoride concern

27

Renal Failure

Mantinence of Anesthesia

  1. Short acting opioid + O2 + Agent +/-  N2O
    • Opioids can accumulate
  2. For persistant intra-op HTN:
    • ↑ inhaled agent, NTG, hydralazine , ß-blockers (↑ DOA possible)
  3. 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.  

28

Renal Failure 

Reversal agents

 

Renal excretion is the primary route of elimination

  • Edrophonium (75%) 
  • Neostigmine (50%)
  • Pyridostigmine (75%)

Renal failures effect on these drugs: 

  1. Prolonged half life
  2. Prolonged at least as much as the relaxants
  3. 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)

29

Renal Failure

Fluid Management

  1. USE pre-hydration in renal patients who are NOT on dialysis
    •  ½ NS or NS→ NO Lactated Ringers → has 4 meq/L of K+
    1. Use 500 ml bags & microdrip (60 gtts)
  2. Maintain urine output at 0.5 cc/kg/hr
    1. Lasix 1-5 mg if U/O drops 
  3. Urine output is NOT predictive of postoperative renal insufficiency
  4. Anuric patients
    1. display a narrow margin of safety for fluids
    2. CHF or Pulmonary Edema may develop postop if not careful with fluids

30

Renal Failure 

Monitoring

  1. Minor surgical procedures can be monitored by noninvasive means
    1. Do NOT measure BP in arm with fistula
    2. Invasive monitoring may be needed for diabetic with advanced renal disease
  2. A-line needed for major cases
  3. CVP or PA pressures for cases with a large anticipated fluid shifts or blood loss
    1. bowel surgery
  4. Also consider TEE

31

Renal Failure

Regional Anesthesia

  1. Good  to use d/t great vasodilation
  2. Caution with a coagualopathy (check coags)
  3. In combo with metabolic acidosis regional may ↓ seizure threashold
  4. No not use if they have an infection 
  5. Used for 
    • Placement of AV Fistula : Brachial Plexus Block/Sedation + Local 

32

Renal Failure

Vasopressors

GOAL =  adequate intravascular fluid volume & minimizing CV depression vasopressors are used sparingly

  1. α-adrenergic:
    • phenylephrine = greatest ↓ in renal circulation
  2. β-adrenergic:
    1. ↑ myocardial irritability and NO renal vasoconstriction
  3. 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

33

Renal Failure and general Anesthesia

Summary

  1. Renal patienst should have dialysis the day before or day of surgery
  2. NO LR use K+ free solution and a microdrip (60 gtts)
  3. AV Fistula: do not use extremity for BP or IV
  4. CV disease is likely:
    • Step up your monitoring! 
    • A-line, Swan → Maintain LV preload
  5. Treatment of Hypotension:
    • Treat with a direct α (phenylephrine)
      • but remember renal constriction
    • β-can cause cardiac irritability
  6. GI prophylaxis:
    • H2 blockers (but they are not cleared very well)  
    • no metoclopramide
  7. Muscle Relaxants:
    • no/little renal elimination

34

Renal Failure

Post-op management

  1. Recurarization can occur d/t ineffective metabolism of other drugs (antibiotics)
    • Gentamycin
  2. HTN is common → treat w/ NTG & SNP
  3. ECG monitoring
  4. Continue O2
  5. Antibiotic Continuation

35

Endoscopy Cystoscopy

  1. Most common urologic procedure
  2. Indicated for:
    1. Hematuria (bleeding in the urine)
    2. recurrent urinary infections
    3. urinary obstruction (renal stones)
    4. Other surgeries performed under cysto  bladder biopsies, extraction of renal stones, placement of ureteral stent
  3. Procedure:
  4. Endoscopy & Cystoscopy
    • Endoscopy = visualize & evaluate the ureter, kidney, bladder, prostate & urethra to diagnose and treat renal calculi, hematuria, trauma, cancer
    1. Cystoscopy = passage of a rigid scope through the urethra into the bladder
  5. Can be done under MAC with 2% lidocaine jelly can be used (and can be done under MAC)
  6. Bladder distention requires regional or general anesthesia
  7. Done in Lithotomy position

36

Lithotomy position

Most common nerve injuries

  1. Common peroneal nerve injury
  2. Saphenous nerve damage
  3. Obturator and femoral nerve injury
  4. Sciatic nerve

Positioning considerations/risks

  1. Both legs need to come up together
  2. Decrease FRC and atelectasis possible
  3. Increased venous return may exacerbate CHF
  4. Bladder perforation
    • May go unnoticed under GEN
    • Consider if:
      • unexplained HTN, tachycardia, hypotension
      • Shoulder pain is referred bladder pain
      • Fever/bacteremia
      • Bleeding 

37

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)

38

Cystoscopy 

Anesthetic Techinque

Most often General with an LMA (if not a full stomach)

  1. Short procedure length (15-20 minutes)
  2. Most patients apprehensive

Regional anesthesia

  1. Spinal is preferred d/t faster onset 
    1. Studies show no need to wait for spinal onset before moving into lithotomy
  2. Need a T10 level block
    1.  Spinal (0.75% bupivacaine)
      • (10-12 mg if  > 1 hour) or (7.5 ml if  < 1 hour)
    2. Lumbar Epidural (1.5 - 2% lidocaine w/ epi 15-25ml)
      • Supplement with 5-10 ml bolus as needed
    3. Local (2% lidocaine jelly with IV sedation)
  3. Sensory level T10 block
    1. Does not abolish obturator reflex
    2. electrocautery may stimulate obturator nerve d/t proximity of nerve to bladder wall
    3. Will see external rotation & adduction of thigh
    4. Can only block w/ muscle paralysis → but do NOT want to give MR with regional

39

TURP

Procedure

Types

Risks

Transurethral Resection of Prostate

  1. most common GU procedures in men > 60
    1. Lateral and medial lobe of prostate removal alleviates urinary obstruction from BPH
  2. Preceded by cystoscopy
    • resecto-scope inserted into urethra/bladder allows both cutting and coagulation of tissue and vessels. 
  3. Three types 
    1. M-TURP (monopolar) MUST irrigate with NON-electrolyte solution (problem = TURP syndrome)
    2. B- TURP (bipolar) can irrigate with 0.9% NS 
    3. L-TURP (laser) NO fluid irrigation needed
  4. Continuous irrigation is needed to
    • Distend bladder
    • Wash away blood and tissue
    • Maintain visibility
  5. 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
  6. Hypothermia
    • Results from Large volumes of irrigating fluids
    • Warm fluids to body tem

40

TURP

Anesthetic Technique

  1. Position: Lithotomy w/ slight Trendelenburg
  2. Pre-op medication
    1. Sedation as needed for anxiety
    2. Antibiotics per surgeon/often:
      • Gentamycin 80 mg IV slowly (can potentiate our NM blockade → may start w/ lower dose of Roc
  3. EBL ≈ 500mls (2-4ml/min of resection time)
    • Prolonged procedure? get a BG to check Hgb 
    • Consider Type and cross
  4. General
    • Acute hyponatremia from TURP syndrome may delay emergence from GA
  5. Regional
    1. Spinal –technique of choice w/ M-TURP
    2. T-10 sensory block required
    3. Allows for monitoring of:
      • accidental bladder perforation  (shoulder pain)
      • mental status ∆s d/t water intoxication/fluid overload (start to slur their words)
    4. ↓ risk of post-op venous thrombosis
    5. ↓ blood loss
  6. M & M: No difference between GEN and Spinal

41

TURP syndrome

What is it

Prevetion

Treatment

Irrigation opens venous sinuses in prostate & allows systemic absorption of irrigating fluid

  1. Usually caused glycine, sorbitol, or mannitol
  2. M-TURP (monpolar = non electrolyte hyposmplar solution)
    1. ​Cant use electrolyte solutions because they disperse the electrocautery current 
  3. 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 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

  1. Early recognition is Key
    • Look for fluid overload, lung sounds, seizures
  2. Fluid restriction
  3. Loop diuretic
  4. Hypertonic solution if hyponatremia present
    • 100 ml 3% saline over 1-2 hours
    • Administer based on patient's serum Na+ → ideally >120
  5. Treat seizures with midazolam, thiopental, or phenytoin  
    • if glycine used consider a trial of magnesium 
  6. Intubate

42

ESWL

Procedure

Pateint considerations

Extracorporeal Shock Wave Lithotripsy (ESWL)

  1. Disintegrate calculi in upper ⅔ of ureters/kidneys
  2. Shock waves focused at renal stones
    1. High energy units = 1st generation = patient in water
    2. Low energy unit = 2nd + 3rd = lithotrypsers w/o water bath
      • small water-filling coupling device and tightly focused sound beam 

Patient considerations

  1. 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
  2. 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 

43

ESWL

Anesthetic Management

  1. Immobilization is very important to limit shock to focal zone only
  2. Very loud = earplugs (Us and patient)
  3. 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
  4. 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)
  5. MAC (Monitored anesthesia care)
    • Flank infiltration and Intercostal block with monitored anesthesia care w/ 3rd generation (still require immobilization)