Schmerler - N614 Renal

Front 1

The kidneys regulate the volume and composition of

Back 1

body fluids

Front 2

The kidneys maintain ___, ____ and ____ balance and regulate serum osmolality.

Back 2

electrolyte, acid/base, extracellular fluid

Front 3

What do the kidneys conserve?

Back 3

glucose, amino acids, proteins, water and vitamins

Front 4

What do the kidneys excrete?

Back 4

toxins, end products of metabolism

Front 5

What do the kidneys produce?

Back 5

erythropoietin, renin, hydroxylation of Vit D to physiologically active form

Front 6

What nephron parts are in the cortex?

Back 6

macula densa, distal tubule, proximal tubule, connecting tubule, bowman's capsule, cortical collecting tubule

Front 7

What nephron parts are in the medulla?

Back 7

loop of henle (thick ascending, thin ascending, thin descending), medullary collecting tubule, collecting duct

Front 8

This is the functional unit of the kidney

Back 8

nephron

Front 9

The ______ reabsorbs 67% of filtrate, which consists mainly of glucose, water, bicarb, amino acids, sodium and potassium.

Back 9

proximal convoluted tubule

Front 10

Urine exits via the _____ into the renal pelvis for excretion.

Back 10

collecting duct

Front 11

The _____ establishes and maintains the osmotic gradient in the medulla of the kidney. It plays crucial role in establishin the countercurrent multiplier and produces the osmotic gradient.

Back 11

loop of henle

Front 12

The osmotic gradient in the corticomedullary region is___ mOsm, and ____ mOsm in the deep medulla.

Back 12

300, 1200-1500

Front 13

The _____ and _____ make final adjustments to urine osmolality, pH and ionic composition.

Back 13

distal tubule and collecting duct

Front 14

______ controls the reabsorption of H20.

Back 14

ADH

Front 15

_____ controls the secretion of K.

Back 15

aldosterone

Front 16

The kidneys receive ____ % of cardiac output, and filter ____mL/min of plasma.

Back 16

20-25% (which is 1.25 L/min)
125 mL/min of plasma filtration

Front 17

How does blood get from the aorta to the glomerulus?

Back 17

aorta --> renal artery --> interlobar arteries --> arcuate arteries --> interlobar arteries --> afferent arteriole --> glomerulus

Front 18

To evaluate renal fcn, accurate assessment relies on...

Back 18

laboratory determinations

Front 19

Renal impairment may be due to...

Back 19

- glomerular dysfunction
- tubular dysfunction
- obstruction

Front 20

The greatest renal derrangements are caused by abnormalities of

Back 20

glomerular function

Front 21

The most useful lab tests for kidney fcn are related to...

Back 21

GFR

Front 22

Ammonia is produced from deamination of _____. The primary source of urea is the ____.

Back 22

amino acids, liver

Front 23

Hepatic conversion of ammonia to urea prevents accumulation of

Back 23

toxic ammonia levels

Front 24

BUN is directly related to _____ and inversely related to _____.

Back 24

direct- protein catabolism
inverse- GFR

Front 25

BUN is not a reliable indicator of GFR unless...

Back 25

protein catabolism is normal and constant

Front 26

Normal BUN is

Back 26

10-20 mg/dL

Front 27

Creatine, a product of ______, converts to creatinine.

Back 27

muscle metabolism

Front 28

Creatinine production is relatively _____ and related to _____.

Back 28

constant, muscle mass

Front 29

Creatinine is directly related to _____ and inversely related to ____.

Back 29

direct- body muscle mass
inverse- glomerular filtration

Front 30

Is creatinine a reliable indicator of GFR?

Back 30

yep

Front 31

Normal male and female creatinine levels?

Back 31

male- 0.8-1.3
female- 0.6-1.0

Front 32

GFR declines with _____ yet serum creatinine remains relatively normal.

Back 32

increasing age

Front 33

Normal BUN:Cr ratio?

Back 33

10:1

Front 34

Low renal tubular flow rates enhance _____ but do not affect _____. As a result, ratio will increase above 10:1.

Back 34

urea reabsorption, creatinine handling

Front 35

Decreases in tubular flow can be caused by

Back 35

decr renal perfusion, obstruction

Front 36

Volume depletion, disorders assoc w decr tubular flow, obstructive uropathies, and incr in protein catabolism will all lead to BUN:Cr ratio of

Back 36

> 15:1

Front 37

This is the most accurate method available for clinically assessing overal renal function.

Back 37

Cr clearance

Front 38

Normal Cr Clearance is

Back 38

125 mL/min (110-150)

Front 39

Cr Clearance measurement is usually performed ___ hrs.

Back 39

2 or 24
2 hr determinations are accurate and easier to obtain

Front 40

Cr Clearance in mild renal impairment

Back 40

40-60 mL/min

Front 41

Cr Clearance in moderate renal dysfunction

Back 41

25-40 mL/min

Front 42

Cr Clearance in overt renal failure

Back 42

<25 mL/min

Front 43

This test may be helpful in identifying some d/o's of renal tubular dysfunction.

Back 43

Urinalysis

Front 44

_____ is related to urinary osmolality and indicative of renal concentrating ability.

Back 44

Specific gravity

Front 45

____ is the result of low tubular threshold for glucose or hyperglycemia.

Back 45

glycosuria

Front 46

Urine is 95% water....so what makes up the other 5 %???

Back 46

ammonia, sulfate, phosphate, chloride, magnesium, calcium, K, Na, Cr, Uric acid, urea

Front 47

What are the renal function tests to determine GFR?

Back 47

- BUN (10-20)
- Cr (0.7-1.5)
- Cr Clearance (110-150)

Front 48

What are the renal function tests to determine renal tubular function?

Back 48

- Urine specific gravity (1.003-1.030)
- Urine Osmolarity (38-140 mOsm/L)

Front 49

Normal renal function w 100% nephrons functioning will yield a GFR of

Back 49

125 mL/min

Front 50

Reduced renal function with 10-40% of nephrons functioning will yield a GFR of

Back 50

12-80 mL/min

Front 51

Renal failure with <10% of nephrons functioning will yield a GFR of

Back 51

<12 mL/min

Front 52

Essential physiologic functions of the kidney

Back 52

1 Glomerular filtration
2 tubular reabsorption
3 tubular secretion

Front 53

2 types of renal failure (Think time!)

Back 53

acute and chronic

Front 54

This type of renal failure is classified according to predominant cause or on basis of urine flow rates. It contains prerenal, renal, and postrenal origins.

Back 54

acute renal failure

Front 55

What are the 3 urine flow rate classifications in acute renal failure?

Back 55

-oliguric renal fx
-anuric acute renal fx
-nonoliguric acute renal fx

Front 56

____ and _____ acute renal failure are readily reversible in initial stages.

Back 56

prerenal and postrenal

Front 57

3 Causes of ARF?

Back 57

- renal ischemia
- nephrotoxins
- intrinsic renal disease

Front 58

In ______ renal failure, the actual failure of the kidney organ is the primary cause.

Back 58

chronic

Front 59

What 3 stages is progressive renal failure divided into?

Back 59

decr renal reserve,
renal insufficiency,
ESRD or uremia

Front 60

2 main types of dialysis?

Back 60

HD, peritoneal dialysis

Front 61

What are the CNS effects of dialytic therapy?

Back 61

disequilibrium syndrome, muscle cramping

Front 62

What are the CV effects of dialytic therapy?

Back 62

hypotension, anemia

Front 63

What are the resp effects of dialytic therapy?

Back 63

hypoxemia

Front 64

What are the CV alterations of advanced renal disease?

Back 64

HTN, CHF

Front 65

What are the hematological changes with advanced renal disease?

Back 65

anemia, prolonged bleeding time

Front 66

What are the GI effects of advanced renal disease?

Back 66

incr risk of GI bleeding

Front 67

What effect does advanced renal disease have on the immune system?

Back 67

infectious complications common

Front 68

What are the neuro effects of advanced renal disease?

Back 68

symptoms correlate to degree of azotemia, seizures assoc w hypertensive encephalopathy

Front 69

What are the endocrine effects of advanced renal disease?

Back 69

hyperparathyroidism, adrenal insufficiency

Front 70

What are the resp effects of advanced renal disease?

Back 70

pneumonitis, pulm congestion and edema

Front 71

What electrolyte abnormalities accompany advanced renal disease?

Back 71

acidosis, Na, Mag, Ca, K

Front 72

How is hyperkalemia related to advanced renal disease handled perioperatively?

Back 72

- HD most effective
- insulin and glucose infusion w bicarb
- hyperventilation
- life-threatening dysrhythmias treated w IV CaCl

Front 73

Describe the pre-op assessment for a renal patient?

Back 73

- H&P (EKG, CBC, H/H, recent K, CXR)
- dialysis access site
- last HD session
- Labs (Cr Clearance, BUN, Cr, U/A)

Front 74

_____ is released due to surgical stimulation in normal kidneys, decreasing urine output.

Back 74

ADH

Front 75

___ is released in normal kidneys during anesthesia due to baroreceptor response to volume depletion.

Back 75

aldosterone

Front 76

General anesthesia may affect autoregulation of the kidneys, which usually is impacted when SBP is < ____ mmHg. _____ caused by agents shunts blood away from the kidneys, and a decrease in RBF causes _____ release, leading to renal vasoconstriction.

Back 76

<80 mmHg,
Hypotension,
renin

Front 77

Most drugs admin perioperatively are at least partly dependent on _____ excretion.

Back 77

renal

Front 78

In the presence of renal impairment, what part of your medical regimen must be modified?

Back 78

dose adjustments!

Front 79

What effects do barbiturates have on renal pts?

Back 79

pts w renal disease more susceptible to these agents bc of decr protein binding and more free drug is available to act

Front 80

What effects do benzos have on renal pts?

Back 80

most are protein bound so may be more sensitive to these agents; extra caution w valium as active metabolites can accumulate, midazolam 60-80% cleared by kidneys in from of active metabolite and highly protein bound

Front 81

What is a nice choice for induction? Why not use the others?

Back 81

etomidate

thiopental is usually ok but dose must be decr and titrated (less protein binding, w/ acidosis less ionized or bound form)

propofol usually ok but can drop BP

avoid ketamine if pt HTN

Front 82

What are the considerations for using morphine in renal pts?

Back 82

6-glucuronide metabolite is active and highly protein bound, so avoid repeat dosing

Front 83

What are the considerations for using meperidine in renal pts?

Back 83

avoid due to accumulation of normeperidine metabolite

Front 84

What are the considerations for using hydromorphone in renal pts?

Back 84

hydromorphone-3-glucuronide metabolite accumulates, avoid repeat dosing

Front 85

What are the considerations for using fentanyl in renal pts?

Back 85

good choice in non-cardiac doses

Front 86

What are the considerations for using alfentanil in renal pts?

Back 86

decr protein binding, no active metabolite

Front 87

What are the considerations for using sufentanil in renal pts?

Back 87

no change in free fraction but pharmacokinetics unpredictable in CRF

Front 88

What are the considerations for using remifentanil in renal pts?

Back 88

remifentanil acid metabolite (minimally active), so no major clinical implications

Front 89

What are the considerations for using halothane in renal pts?

Back 89

avoid, high K and acidosis, can lead to myocardial irritability

Front 90

What are the considerations for using iso/des in renal pts?

Back 90

volatile agents ideal, no dependence on kidney for elim.

Front 91

What are the considerations for using enflurane and sevo in renal pts?

Back 91

compound A and free fluoride ion accumulation - avoid

Front 92

What are the considerations for using H2 blockers such as pepcid and zantac in renal pts?

Back 92

highly dependent on renal excretion

Front 93

Is metoclopramide safe in renal pts?

Back 93

partly excreted unchanged by kidneys but can accumulate in renal failure, generally safe in a single dose

Front 94

Are anticholinergics such as atropine and glycopyrrolate safe to use in renal pts?

Back 94

can be used safely though metabolites may accumulate with repeat dosing

Front 95

Should you use succ in a renal pt?

Back 95

safe in pts with K <5.0 mEq/L, but can transiently incr K by 0.5 mEq/L

Front 96

Why are atracurium and cisatracurium beneficial in renal pts?

Back 96

metab and excreted through Hoffman elimination and nonspecific esterases -- drug of choice bc does not rely on kidneys!

Front 97

What are the considerations for using vec and roc in renal pts?

Back 97

primarily elim in liver but there is some mild prolongation in renal failure

Front 98

Which paralytics are 60-90% dependent on renal excretion and should be avoided in renal pts?

Back 98

D-tubocurarine, metocurine, gallamine, pancuronium, pipecurium, doxacurium

Front 99

What are the considerations for using reversal agents in renal pts?

Back 99

edrophonium and pyridostigmine (75%) and neostigmine (50%) elim by kidneys -- prolongs half life (at least as much as relaxants they reverse)

Front 100

What are the 6 types of diuretics?

Back 100

loop, osmotic, thiazide, carbonic anhydrase inhibitors, aldosterone antagonists, Na channel blockers

Front 101

Lasix, Bumex, Edecrin, and Demadex are all _____ diuretics, acting in the ascending loop of henle.

Back 101

loop diuretics

Front 102

What are the 3 actions of loop diuretics?

Back 102

- inhibits Na, K, and 2CL-
- diminishes osmotic gradient in the interstitium of the medulla
- reduces amt of water reabsorbed from collecting duct, increasing H20 excretion

Front 103

What are the adverse effects of loop diuretics?

Back 103

hypoK, volume deficit, hypotension, reversible deafness

Front 104

____ is the primary osmotic diuretic, and it acts throughout the renal tubule.

Back 104

mannitol

Front 105

How do osmotic diuretics (mannitol) work?

Back 105

poorly permeable agent gets trapped in renal tubule --> exerts an osmotic force --> decr reabsorption of H20

Front 106

What are the adverse effects of mannitol (osmotic diuretics)?

Back 106

hypoK, rapid expansion of intravascular space --> heart failure

Front 107

_____ is the primary carbonic anhydrase inhibitor used, and it takes action in the proximal tubule.

Back 107

acetazolamide (diamox)

Front 108

How do carbonic anhydrase inhibitors (diamox) work?

Back 108

inhibits carbonic anhydrase to decr Na and HCO3 reabsorption, causing diuresis

Front 109

Why are carbonic anhydrase inhibitors (Diamox) given?

Back 109

to correct metabolic alkalosis

Front 110

What are the adverse effects of carbonic anhydrase inhibitors (diamox)?

Back 110

metabolic acidosis through HCO3 loss in urine

Front 111

______ diuretics work in the distal tubule. Examples include...

Back 111

thiazide,

HCTZ, chlorothiazide, chlorthalidone, metolazone

Front 112

How do thiazide diuretics (HCTZ, metolazone) work?

Back 112

inhibit Na reabsorption in the early distal tubule

Front 113

What are the adverse effects of thiazide diuretics (HCTZ, metolazone)?

Back 113

HypoK

Front 114

______ diuretics work in the late distal tubule and the collecting duct. Examples include...

Back 114

aldosterone antagonists,

spironolactone (aldactone), triamterene, amiloride

Front 115

How do aldosterone antagonists (spironolactone, triamterene, amiloride) exert their effects?

Back 115

decr reabsorption of Na and decr K secretion by competing for aldosterone binding sites in the distal tubule

Front 116

What are the adverse effects of aldosterone antagonist diuretics (spironolactone, triamterene, amiloride)?

Back 116

hyperK due to K-sparing diuretic

Front 117

_____ diuretics work in the late distal tubule and the collecting duct. Examples include amiloride and triamterene.

Back 117

Na channel blockers

Front 118

How do Na channel blockers (amiloride and triamterene) work?

Back 118

decr Na reabsorption from the late distal tubule and collecting duct

Front 119

What adverse effects are associated with Na channel blockers (amiloride and trimterene)?

Back 119

hyperK due to K sparing

Front 120

What are the preop anesthesia interventions for renal pts?

Back 120

- identify high risk pts and procedures
- correct fluid losses and hypovolemia
- maintain adequate hydration
- clinical monitoring

Front 121

What are the intraop strategies for renal pt anesthesia?

Back 121

- placement of urinary catheter (if not anuric)
- fluid challenge if u/o drops
- renal doses of dopamine
- diuretic therapy w aggressive monitoring and intravascular volume expansion
- prophylactic admin of mannitol or lasix

Front 122

What are the 4 phases of ARF?

Back 122

1. onset (initiation phase)
2. oliguric phase
3. diuretic phase
4. recovery phase

Front 123

What is the anesthesia mgmt strategy once renal failure has been established in the OR?

Back 123

- maint fluid and electrolyte balance
- early HD during oliguric and diuretic phases
- infection is most frequent complication that can lead to death

Front 124

What are induction techniques for renal pts?

Back 124

- avoid succ (unless necessary, IE RSI)
- lidocaine to blunt stimulus
- may need beta blocker to control HTN
- delayed gastric emptying and incr gastric volume, so consider full stomach protocol w RSI

Front 125

What are maintenance techniques for renal pts?

Back 125

- short acting opioids w N20/02/inhaled Agent cocktail
- no IV/BP cuff on arm w AV fistula
- monitors: invasive hemodynamic monitoring indicated due to high morbidity group of pts (DM and RF pts have 10x periop morbidity of pts w DM and no RF)
- HTN: manage persistent elevation in BP w incr IA, NTG, or hydralazine
- controlled ventillation good bc decreases risk fo resp acidosis which is not good in setting of metabolic acidosis

Front 126

What are some intraop fluid mgmt techniques in renal pts?

Back 126

-pre-hydrate if not dialysis dependent
- LR (has 4 mEq/L of K)
- use 500 mL bgs and microgtt (60 gtts)
- maintain u/o of 0.5 cc/kg/hr
- give 5 mg lasix if u/o drops

Front 127

In renal pts, intraop. urine output (is/is not) predictive of post op renal insufficiency.

Back 127

IS NOT

Front 128

Anuric pts display a ____ margin of safety for fluids, and ____ or _____ may develop post op if not cautious.

Back 128

narrow,
CHF or pulm edema

Front 129

What are the post op mgmt techniques for renal pts?

Back 129

- EKG, BP, SP02 monitoring
- continue supplemental O2 prn
- continue abx

Front 130

In _____ the surgeon is able to insert a surgical instrument into the urethra for direct visualization of the internal structures of the bladder.

Back 130

cystoscopy

Front 131

______ is the most commonly performed urologic procedure, and is indicated for hematuria, recurrent urinary infections, or urinary obstruction.

Back 131

cystoscopy

Front 132

Types of surgeries performed under cystoscopy:

Back 132

bladder biopsies, extraction of renal stones, placement of ureteral stents

Front 133

Pre-op considerations for cystoscopy pts?

Back 133

standard pre-op eval

Front 134

Intra-op position and positioning considerations for cystoscopy pts?

Back 134

lithotomy position

considerations: common peroneal nerve injury, saphenous nerve damage, obturator and femoral nerve injury, sciatic nerve injury, decr FRC w resulting atelectasis, incr venous return exacerbating CHF

Front 135

What are the 2 options for anesthetic technique for cystoscopy pts?

Back 135

- General anesthesia w LMA if pre-op eval permits
- regional anesthesia w spinal, local and sedation (local/MAC)

Front 136

What are the pre-op considerations for TURP pts?

Back 136

same as cysto- standard pre-op eval

Front 137

What is the position preferred for TURP cases?

Back 137

lithotomy

Front 138

List the 5 major complications assoc w TURP:

Back 138

1. hypothermia
2. TURP syndrome
3. bladder rupture
4. DIC (released of thromboplastins from prostate into blood stream; if done for CA, tumor may release fibrinolytic enzymes into blood; dilutional thrombocytopenia from absorption and irrigation)
5. septicemia (open sinuses allow bacteria to enter bloodstream)

Front 139

For a TURP procedure, a _____ is inserted in the urethra, down into the bladder and to the prostate gland for resection.

Back 139

retroscope

Front 140

This complication can occur intra or post op in TURP cases, and is caused by systemic absorption of irrigation fluid through open prostate sinuses.

Back 140

TURP syndrome

Front 141

What are awake and anesthetized pt s/s of TURP syndrome?

Back 141

awake: headache, restless, confused (hypoNa, H20 intoxication), cyanosis, dyspnea, arrhythmias, hypotension, seizures (HypoNa, H20 intox)
sleeping: hypo-osmolality, fluid overload (CHF, pulm edema), hemolysis

Front 142

How do I treat Turp syndrome?

Back 142

- early recognition and tx critical
- supportive care to avoid hypoxemia and hypoperfusion
- H20 restriction and loop diuretic to remove excess fluid
- symptomatic hypoNa leading to seizures/coma needs hypertonic saline (3% NaCl no faster than 100 mL/hr)

Front 143

What are the 2 possible anesthesia techniques for TURPs?

Back 143

- regional: spinal or epidural depending on length of procedure
- general: LMA if pre-op eval appropriate

Front 144

This type of urosurgery involves shock waves used to break apart a kidney stone to allow for passage through the urethra. Newer machines employ gel pads to conduct the shock waves into the body, and older machines employed a submersion tank w H20.

Back 144

extracorporeal shock wave lithotripsy (ESWL)

Front 145

What are the preop considerations for ESWL?

Back 145

- pts w heart dz and implantable devices (pacers or AICDs) need further eval, as ESWL more likely to cause arrhythmias in these pts

Front 146

During ESWL, it is important to control the heart rate because...

Back 146

- better results
- shock wave timed w EKG to avoid causing arrhythmias
- number of shock waves is dependent on number of heart beats/min (slower HR = lower # of shock waves/min; and fast HR = incr risk of causing arrhythmias due to inaccurate shock wave w EKG)

Front 147

What were the effects of ESWL immersion?

Back 147

- hot water bath can lead to vasodilation and hypotension initially
- compression of peripheral vasculature by pressure of H20 can lead to incr venous return (distrib of blood to thoracic compartment) which will incr SVR and decr CO
- incr in blood in central compartment leads to exacerbation of CHF
- incr intra-thoracic blood volume reduces functional residual capacity by 30-60% and predisposes to hypoxemia

Front 148

What are the 3 options for anesthetic plan for ESWL pts?

Back 148

1. regional: spinal or epidural (epidural better bc allows for re-dosing during long procedure), avoid placing too much air in epidural space during placement bc air dissipates shock wave and lowers efficacy
2. General: ETT bc pt is placed in H20 - more secured airway
3. MAC w sedation

Front 149

What are the monitoring considerations during ESWL?

Back 149

secure EKG w water proof drsgs if being immersed in H20 (EKG necessary to properly time shockwaves)

Front 150

What are the fluid management techniques recommended in ESWL?

Back 150

- large amts of fluid required to ensure adequate urine production and flow to remove debris from kidney stone
- lasix can be given in conjunction to fluid to incr u/o

Front 151

This is the removal of the prostate due to CA

Back 151

radical prostatectomy

Front 152

Intra-op considerations for radical prostatectomy?

Back 152

- large blood loss (EBL 300-500 mL) due to vascular nature of prostate and approach to remove it
- A-line recommended for frequent lab draws (Due to blood loss) and more closely monitor BP if hypotensive
- neck of bladder is removed during procedure (will lose u/o from catheter during this period)
- indigo carmine useful to help identify ureters during resection
- prepare for transfusions from blood loss (large IV access, T&C pre op)
- maintain u/o (may be temporarily anuric during construction of urinary pouch after removal of bladder)
- permissive hypotension to decr blood loss

Front 153

Choices of anesthetic plan for radical prostatectomy?

Back 153

1. regional: epidural possible but will require large amts of sedation; will cause unopposed parasymp. control of bowel causing contracted bowel (makes creation of pouch difficult for urinary diversion)
2. general: allows for better control of airway in trendelenberg, preferred, large incision from pubis to xiphoid process

Front 154

_____ requires placement of ureters into a segment of the bowel which is connected to a stoma formed in the abdomen for placement of a catheter post op.

Back 154

Urinary diversion

Front 155

During retroperitoneal lymph node dissection, there is an extremely large incision used to remove all lymph tissue from the _____ and ____ to the iliac bifurcation.

Back 155

ureters, renal vessels

Front 156

During retroperitoneal lymph node dissection, large incision size will lead to incr in ______ due to third spacing of fluids.

Back 156

fluid requirements

Front 157

During retroperitoneal lymph node dissection, _____ may be given to incr urinary blood flow and urine production duing resection around renal blood supplies.

Back 157

mannitol

Front 158

During retroperitoneal lymph node dissection, chemo pts will be at higher risk for ______ and _____, so high Fi02 should be avoided.

Back 158

O2 toxicity, pulm complications

Front 159

During retroperitoneal lymph node dissection, there is risk of damage to the _____artery, so Proper neuro exam is required prior to use of regional.

Back 159

artery of adamkiewicz

Front 160

During retroperitoneal lymph node dissection, pain control is very _____. The 2 pain mgmt techniques most appropriate are...

Back 160

difficult,

epidural cath to improve post op pain control, narcotic PCA required if not using epidural