Renal Problems in the Surgical Patient

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Renal Problems in the Surgical Patient

• Dr. Bob Richardson
• TGH Nephrology
• 2009

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Agenda

• Assessment of kidney function
• Acute renal failure
• Case studies of acute renal failure
• Chronic kidney disease
• Causes and stages of chronic kidney disease
• Surgery in patients with chronic kidney disease
• Surgery in dialysis patients
• Routine IV therapy in healthy patients

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Assessment of Kidney Function

• A normal GFR and a normal urinalysis rules out
  significant renal disease
• How to estimate GFR?
• Serum creatinine

Serum creatinine
creatinine
GFR urine
muscle
serum kidney
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Serum creatinine is an imperfect method of
estimating GFR there is no perfect method.
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Determinants of Serum Creatinine

• Muscle mass
• age (muscle mass falls with age)
• gender (women less muscle than men)
• Weight, fitness (muscle vs fat)
• Nutritional state (muscle loss)
• GFR

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How to Correct for Differences in Muscle Mass

• Measure GFR directly
• Creatinine clearance with 24 h urine
• Radionucleide GFR (nuclear medicine functional
  renal imaging)
• Estimate GFR Using Formulas
• Cockcroft-Gault
• MDRD (used by Ontario Labs to give eGFR)

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MDRD equation

• Serum creatinine, age, gender, race (black or
  caucasian)
• Only useful for patients with known kidney
  disease
• Ontario labs now report eGFR using this formula
• GFR determines stage of CKD

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Chronic Kidney Disease

• GFR ml/min
• Stage 1 gt90
• Stage 2 (mild) 60-90
• Stage 3 (moderate) 30-60
• Stage 4 (advanced) 15-30
• Stage 5 End stage KD lt 15
• GFR measured or calculated using MDRD equation

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Limitations of eGFR (MDRD)

• Cannot be used to determine if kidney function is
  normal
• Not validated in acutely ill hospitalized
  patients
• Not well validated in Asians
• Most useful for stable patients with known CKD

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Examples of Calculated Ccr

• Two patients same serum creatinine 100 umol/L
• 20 yr old male, 80 kg, creatinine 100 umol/L
  Creatinine clearance 115 ml/min
• 65 year old woman, 40 kg, creatinine 100 uM
  Creatinine clearance 30 ml/min
• Moral you need to look at more than the serum
  creatinine

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Case 1

• 67 year old man with large abdominal mass
• Biopsy sarcoma
• Encases right kidney, left kidney atrophic
• Serum creatinine 140 umol/L
• What would the effect of surgery be on residual
  GFR?

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Case 1

• Creatinine 140 uM
• eGFR 48 ml/min (stage 3 CKD)
• Functional renal imaging
• Blood side GFR 38 ml/min
• 75 function to right, 25 to left
• Estimated residual GFR if right nephrectomy is
  10-12 ml/min (stage 5 CKD)
• Conclusion patient will likely need dialysis
  post-op

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Acute Renal Failure

• Renal response to reduced effective circulating
  volume
• Prerenal ARF
• Ischemic and toxic acute tubular necrosis
• Obstruction
• Abdominal compartment syndrome
• Case studies
• Dialysis for ARF

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Renal Response to Reduced Effective Circulating
Volume

• What is effective circulating volume?
• cardiac output vs peripheral vascular resistance
• how cardiovascular receptors see arterial
  filling
• Effective circulating volume is reduced in
• volume depletion (hemorrhage, diarrhea etc)
• systemic vasodilatation (sepsis, liver failure)
• congestive heart failure

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Consequences of Reduced Effective Circulating
Volume on the Kidney

• Arterial baroreceptors
• ? SNS
• ? circ. catecholamines
• ? ADH
• JG apparatus
• ? renin, angiotensin II, aldosterone

• Effects on Kidney
• ? renal blood flow (?BP ?renal vasc.
  resistance)
• ? GFR/RBF (efferent constriction by AII,
  preserves GFR)
• Sodium, chloride retention
• urine sodium lt 20 mM
• Water retention Uosm gt500

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Angiotensin II and Regulation of GFR
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Causes of Acute Renal Failure

• 1. Prerenal
• 2. Vascular
• 3. Glomerular
• 4. Tubulo-interstitial
• 5. Obstruction

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2
3
4
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Prerenal Acute Renal Failure

• GFR arterial BP
• renal vascular resistance
• BP depends on venous return, heart rate,
  contractility, systemic vascular resistance
• RVR may be increased by
• catecholamines, angiotensin II
• sepsis, hepatic failure
• NSAIDs, Cyclosporine
• Renal arteriolarsclerosis (age, hypertension)

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Prerenal Failure-Clinical

• Hypovolemia
• hemorrhage
• diarrhea, vomiting, burns
• pancreatitis, ascites
• SIRS/capillary leak
• Septic shock
• Cardiogenic shock
• Drugs cyclosporine, NSAIDs, etc

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The Kidney In Prerenal Failure

• Normal renal response to reduced effective
  circulating volume
• oliguria (lt 0.5 ml/kg/h)
• normal urinalysis (no protein or casts)
• high urine osmolality (ADH acting)
• low urine Na or Cl-
• increasing serum creatinine
• Rapid improvement in urine flow and serum
  creatinine if prerenal state corrected

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Ischemic Acute Tubular Necrosis

• Causes same as prerenal ARF - more severe or
  more prolonged
• Factors that increase risk for ATN
• sepsis (especially gram -)
• biliary obstruction with jaundice
• angiographic dye
• myoglobin (rhabdomyolysis)
• cardiopulmonary bypass
• CKD

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Tubular proteins (markers of injury) in patients
on bypass for lt 70 minutes or gt 90 minutes Ann
Thoracic Surg 200375906
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Pathophysiology of Ischemic ATN

• Necrosis of cells of thick ascending limb and
  proximal tubule in outer medulla
• Cells and cell debris enter lumen and cause
  obstruction and backleak of filtrate
• Glomeruli are normal
• Continued hypotension causes prolonged severe
  vascoconstriction

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Focal loss of tubule cells lining tubular
basement membrane
Debris in tubule lumens
Interstitial edema
Dilated tubules
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Urine in Ischemic ATN

• Oliguria (if severe injury) or non-oliguric
• Urine flow may increase with furosemide
• Isotonic urine (300 mosmol/kg)
• High urine sodium ( gt 30 mmol/L)
• hematuria, heme granular casts, debris on
  urinalysis

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Urine in ATN note blood cells, tubular (white )
cells, debris and characteristic heme granular
casts (muddy brown casts)
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Toxic Acute Tubular Necrosis

• Aminoglycosides, amphotericin, cisplatin etc
• Aminoglycosides
• accumulate in proximal tubule, cause cell
  necrosis
• tubular obstruction and backleak
• non-oliguric, ? creatinine at 7-10 days
• toxicity most related to duration of therapy
• prevent by limiting course to lt 10 days

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Obstruction and Acute Renal Failure

• Males prostate
• Females pelvic malignancy
• Either
• single kidney and stone, clot
• retroperitoneal malignancy
• lymphoma
• bladder, rectum
• Retroperitoneal fibrosis

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Obstruction (2)

• Urine flow anuric to polyuric
• Isotonic, high urine sodium
• Diagnosis by ultrasound
• Treatment
• bladder catheter!
• Unilateral or bilateral percutaneous nephrostomy
• Ureteral stent (retrograde or antegrade)
• Good prognosis if caught in lt 1-2 months

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Abdo U/S in Obstruction
Normal
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Other Causes of Acute Renal Failure
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Abdominal Compartment Syndrome

• Normal IP pressure 0-10 mmHg
• ACS when IP pressure gt 25 mmHg
• Increased renal vein resistance
• Reduced RBF and GFR
• Low urine Na
• Causes trauma, pancreatitis, liver transplant,
  bowel obstruction often with massive amounts of
  fluid resuscitation

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Atheroembolic disease

• obstruction and inflammation of small renal
  vessels due to cholesterol emboli
• follows aortography, CABG, aortic OR
• usually elderly vasculopaths - aortic AS
• ischemic toes, livido reticularis, abdo pain
• slowly progressive renal failure over weeks
• bland urinalysis, eospinophilia

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Contrast-induced ARF

• Non-oliguric ARF within 24 h of procedure
• Cause unknown (vascular vs toxic)
• Risk factors
• Stage 4-5 (GFR lt 30 ml/min)
• diabetic nephropathy with GFR lt 40 ml/min)
• Congestive heart failure
• Prevention
• IV saline or IV sodium bicarbonate
• N-acetylcysteine (controversial)
• Prognosis usually good except DM CKD 4-5

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Less Common Causes of ARF

• Allergic interstitial nephritis drug
  reaction penicillins, cipro, NSAIDs, Septra etc
• Thrombotic Microangiopathy (hemolytic uremic
  syndrome)
• Toxemia of pregnancy
• Bone marrow transplant
• Cyclosporine
• Toxigenic E.Coli (Walkerton)
• Malignant hypertension etc.

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Assessment of Patient with ARF

• History prior renal function BP, ECFV
• Drugs diuretics, antibiotics, NSAIDs, ACE
  inhibitors, angio dye, cyclosporine
• Physical Exam BP, JVP, edema, ascites,
  peripheral pulses, bruits, urine flow
• Lab lytes, creatinine, urea, CBC, blood film,
  urinalysis, urine lytes, osmolality
• Renal U/S, renal biopsy if dg unclear

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Consequences of Acute Renal Failure

• ? ECF volume pulmonary edema, edema
• Hyperkalemia if oliguria
• Uremia anorexia, nausea, vomiting,
  encephalopthy, etc
• Metabolic acidosis, hypocalcemia,
  hyperphosphatemia, anemia
• Prognosis
• with multiorgan failure in ICU mortality 60-70
• with no other organ failure, prognosis is good

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Dialysis for Acute Renal Failure

• Indications
• Pulmonary edema
• Hyperkalemia
• Serum creatinine gt 500 umol/L
• Serum creatinine gt 300 with oliguria
• Methods
• Conventional HD (3-5 h, 3-6 days/wk)
• CRRT - using Prisma machine heparin vs citrate
• SLED (sustained low efficiency HD) 8 hours 3-6
  days/wk

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Case History 1

• 65 yr old admitted 2 months post CABGAVR
• fever, weight loss, dyspnea
• Febrile, ? JVP, aortic systolic and diastolic m
• blood cultures for strep. Sp.
• Dg bacterial endocarditis gentamicin Pen
• Serum creatinine Day 1 5 8
  10
• 130 125
  165 265
• What is differential diagnosis?

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Case 1

• Differential
• Post-infectious GN
• Ischemic ATN
• Athero-embolic disease
• GENTAMICIN-INDUCED

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Case History 2

• 75 yr old with claudication smoker, hypertension
• Aorto-bifemoral graft for AAA iliac disease
• 2 days post-op has 2 painful blue toes good
  distal pulses abdominal pain
• Creatinine preop day 1 7 14
  28
• 135 145 165
  225 450
• Urinalysis trace blood, no protein, no casts
• ?Cause of acute renal failure

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Case 2

• Differential
• Ischemic ATN
• Renal artery thrombosis
• ATHERO-EMBOLIC DISEASE

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Case History 3

• 45 yr old woman with cholelithiasis
• 1 wk RUQ pain, pale stools, dark urine, jaundice
• 2 days spiking fever, chills, vomiting
• BP 90/60, HR 110 temp 39 jaundice
• U/S dilated bile ducts, distal duct stone
• Blood cultures Klebsiella
• Creatinine 175 ? 260 umol/L urine blood, heme
  granular casts
• Diagnosis?

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CASE 3

• Ischemic ATN
• Obstructive jaundice
• Gram-negative bacteremia
• Hypotension

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Case History 4

• 42 year old primigravida
• At 34 wks mild increase in BP (140/80)
• 35 wks unwell, edema, proteinuria (3)
• C-section
• Creat HGB Plat
  AST
• Preop 98 125 125 200
• 24 h 175 80 25
  1500
• 48 h 370 60 10
  3500
• ?Diagnosis

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Case 4

• Thrombotic Microangiopathy
• HELLP syndrome
• Post-partum acute renal failure

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Case 5

• 50 year old man with known alcoholic cirrhosis
• Presents with 5 days of nausea, vomiting, severe
  epigastric pain, distended abdomen
• Serum amylase 1,500 necrotizing pancreatitis
• Given 3 L crystalloid and colloid for hypotension
• Requires intubation for acute respiratory failure
• In ICU BP 95/65, CVP 25, oliguric
• Differential?

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Case 5

• Differential
• Ischemic ATN
• Abdominal compartment syndrome

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Summary Risk Factors for ARF in Surgical Patients

• Obstructive jaundice
• Sepsis syndrome - especially with MOF
• Angiography
• dye renal failure/diabetes
• atheroembolic disease - vasculopaths
• Prolonged use of aminoglycosides (gt 7 d)
• Hypotension with pre-existing renal disease
  especially in the elderly
• Cyclosporine for transplantation

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Chronic Kidney Disease

• GFR ml/min
• Stage 1 gt90
• Stage 2 (mild) 60-90
• Stage 3 (moderate) 30-60
• Stage 4 (advanced) 15-30
• Stage 5 End stage KD lt 15
• GFR measured or calculated using MDRD equation

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Causes/Risk Factors for CKD

• Risk Factors
• Diabetes
• Hypertension
• Age
• Smoking
• High Cholesterol
• Organ transplantation

• Causes
• Diabetic nephropathy
• Hypertension/vascular
• Glomerulonephritis
• Polycystic Kidneys
• Obstruction
• Multiple myeloma
• Calcineurin-inhibitors

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Patients with Chronic Kidney Disease

• You are helping Dr. Robinette do a nephrectomy on
  a healthy living kidney transplant donor
• You ask yourself what is going to happen to this
  patients kidney function and why?

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What Happens Post Donor Nephrectomy?

• Serum creatinine rises by 50 (not 100)
• Increase in single nephron GFR of 50
• Afferent and efferent arterioles dilate,
  increased glomerular blood flow and pressure
• Normal life expectancy, no increased risk of
  renal failure with loss of 50 of nephrons

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What if More Nephrons are Lost?

• Increased single nephron GFR by afferent and
  efferent arteriolar dilatation
• If lose gt 65 of nephrons, get structural changes
  in glomeruli and arterioles due to
  hyperfiltration and hypertension
• Proteinuria and progressive renal failure
• Predictors of progessive disease?
• Higher serum creatinine
• Hypertension
• Amount of proteinuria gt 1 g/d is bad, gt3 g worse

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Impact of Chronic Kidney Disease on Surgical
Outcomes (1)

• Patients with stage 3-5 CKD are at risk
• Already maximally vasodilated
• Cannot further autoregulate in response to
  hypotension ATN
• Limited ability to excrete extra sodium, water
  and potassium
• Limited ability to retain sodium and water

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Impact of Chronic Kidney Disease on Surgical
Outcomes (2)

• Patients with stages 3-5 CKD have increased risk
  of mortality with surgery
• Higher death rates after CABG
• Higher death rates after aortic surgery
• Higher death rates after MI

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Impact of Renal Dysfunction on Outcomes of CABG
Circulation 20061131063 485,000 US patients
2002-3
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Why Increased Mortality in CKD?

• Increased incidence of vascular disease
  (atherosclerosis)
• Risk factors for kidney disease are risk factors
  for atherosclerosis
• Reduced GFR promotes vascular disease
• Vascular calcification
• Chronic inflammation
• Increased SNS, increased vascular stiffness
• Increased homocysteine

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Case History 6

• 65 yr old woman assessed in vascular surgery
  clinic for 5.5 cm AAA
• Hypertension (160/90), type 2 DM
• Urine negative blood, 1 g/L proteinuria
• Creatinine 275 umol/L (eGFR 20 ml/min)
• What are concerns regarding her low GFR- what
  should you do?

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Case History 6

• Risks
• If aortogram contrast-induced ATN or
  atheroembolic disease
• If OR hypotension, aortic cross-clamp inducing
  ischemic ATN
• If surgery markedly increased mortality risk
• Plan (Nothing evidence-based!)
• request nephrology cardiac assessment
• will renal disease progress anyway? -operate when
  on dialysis?

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Case History 6

• Surgery is planned after cardiac assessment
• Maintain as stable a BP as possible and avoid
  hypotension ( lt 130 systolic in this patient)
• Accurate fluid replacement to avoid volume
  depletion or overload
• Monitor serum potassium (daily lytes)

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Case History 7

• A 79 year old man with a solitary kidney develops
  gross hematuria
• CT 2 cm mass in mid-zone of kidney consistent
  with renal cell Ca
• Operate or not?
• Q What is mortality rate annually in 80 year old
  on dialysis?
• A 20-30

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Management of HD Patient

• Preserve HD access lower or upper arm AV fistula
  or PTFE graft
• No BP, IV or venesection in that arm
• Call nephrology to arrange dialysis
• No IV fluids unless patient is hypovolemic (ask
  nephrology)
• No IV potassium unless hypokalemic (ask
  nephrology)

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Peri-Operative Intravenous Fluid

• What is normal intake of water, Na and K?
• Water 1.5-2 L/d
• Sodium 150 mmol/day
• Potassium 50 mmol/day
• What is main risk of IV fluid post-op?
• Hyponatremia from large volume hypotonic fluid

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Prevention of Postoperative Hyponatremia

• Avoid hypotonic fluid unless the patient is
  hypernatremic
• Limit volume of I.V. fluid given to meet
  patients needs
• Adjust volume to patients body weight

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Peri-operative IV Fluid

• Annals Surgery 2003238641
• RCT of standard vs restricted IV fluid in
  patients undergoing colorectal resection
• Multicenter study from Denmark
• Powered to detect a 20 difference in
  complications with 80 power
• 86 patients per group

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Peri-operative IV Fluid -Standard

• Intra-op
• 500 ml HAES 6 in NS
• Third space loss NS 7 ml/kg/h X1 h, then 5
  ml/kg/h X 2, then .3 ml/kg/h
• Blood loss up to 500 ml 1-1.5 L NS then HAES
• Post-op
• 1-2 L crystalloid/day

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Peri-operative IV Fluid Restricted

• Intra-op
• No preloading
• No replacement of third space loss
• Blood loss volume/volume with HAES
• Post-op
• 1000 ml 5 D/W for remaining OR day
• Then oral fluid or IV if needed
• Furosemide if weight increased by 1 kg

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Results
Standard Restricted
IV fluid OR day 5.4 L 2.7 L
IV fluid POD 1 1.5 L 0.5 L
Max increase wt 0.9 kg 3.5 kg
Complications 40 21
Compl -major 18 8
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Complication frequency related to IV fluid and wt
gain on operative day
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A Comparison of Albumin and Saline for Fluid
Resuscitation in the Intensive Care Unit

• NEJM 20043502247
• Previous meta-analysis suggested albumin
  resuscitation increased mortality
• RCT in 7,000 ICU patients
• 4 albumin vs crystalloid for fluid
• No difference in mortality

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Summary

• Be familiar with stages of CKD
• Interpretation of serum creatinine
• Risks factors for ARF in surgical patients
• Differentiation of prerenal failure from ATN
• Impact of CKD stage 3-5 on surgical outcomes