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Renal Problems in the Surgical Patient
Dr. Bob RichardsonTGH Nephrology
2009
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
Assessment of Kidney Function A normal GFR and a normal
urinalysis rules out significant renal disease
How to estimate GFR?Serum creatinine
muscle
creatinine
serum kidney
Serum creatinine
GFR urine
Serum creatinine is an imperfect method of estimating GFR; there is no perfect method.
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
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)
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
Chronic Kidney DiseaseGFR ml/min
Stage 1 >90Stage 2 (mild) 60-90Stage 3 (moderate) 30-60 Stage 4 (advanced) 15-30Stage 5 End stage KD < 15
GFR measured or calculated using MDRD equation
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
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
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?
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
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
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
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] < 20 mMWater retention Uosm
>500
Angiotensin II and Regulation of GFR
Causes of Acute Renal Failure
1
23
4
1. Prerenal
2. Vascular
3. Glomerular
4. Tubulo-interstitial
5. Obstruction5
Prerenal Acute Renal Failure
GFR = arterial BP renal vascular resistanceBP depends on venous return, heart rate,
contractility, systemic vascular resistanceRVR may be increased by: catecholamines, angiotensin II sepsis, hepatic failure NSAID’s, Cyclosporine Renal arteriolarsclerosis (age,
hypertension)
Prerenal Failure-Clinical
Hypovolemia hemorrhage diarrhea, vomiting, burns pancreatitis, ascites SIRS/capillary leak
Septic shock Cardiogenic shock Drugs: cyclosporine, NSAID’s, etc
The Kidney In Prerenal Failure
Normal renal response to reduced effective circulating volume: oliguria (< 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
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
Tubular proteins (markers of injury) in patients on bypass for < 70 minutes or > 90 minutes
Ann Thoracic Surg 2003;75:906
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
Debris in tubule lumens
Dilated tubules
Focal loss of tubule cells
lining tubular basement membrane
Interstitial edema
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 ( > 30 mmol/L) hematuria, heme granular casts,
debris on urinalysis
Urine in ATN: note blood cells, tubular (white ) cells, debris and characteristic heme granular casts (muddy brown casts)
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 < 10 days
Obstruction and Acute Renal Failure
Males: prostate Females: pelvic malignancy Either:
single kidney and stone, clot retroperitoneal malignancy
lymphoma bladder, rectum
Retroperitoneal fibrosis
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 < 1-2 months
Normal
Abdo U/S in Obstruction
Other Causes of Acute Renal Failure
Abdominal Compartment Syndrome Normal IP pressure 0-10 mmHg ACS when IP pressure > 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
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
Contrast-induced ARF Non-oliguric ARF within 24 h of procedure Cause unknown (vascular vs toxic) Risk factors:
Stage 4-5 (GFR < 30 ml/min) diabetic nephropathy with GFR < 40 ml/min) Congestive heart failure
Prevention: IV saline or IV sodium bicarbonate N-acetylcysteine (controversial)
Prognosis: usually good except DM + CKD 4-5
Less Common Causes of ARF Allergic interstitial nephritis – drug
reaction penicillins, cipro, NSAID’s, Septra etc
Thrombotic Microangiopathy (hemolytic uremic syndrome) Toxemia of pregnancy Bone marrow transplant Cyclosporine Toxigenic E.Coli (Walkerton) Malignant hypertension etc.
Assessment of Patient with ARF History: prior renal function; BP, ECFV Drugs: diuretics, antibiotics, NSAID’s,
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, osmolalityRenal U/S, renal biopsy if dg unclear
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
Dialysis for Acute Renal Failure
Indications: Pulmonary edema Hyperkalemia Serum creatinine > 500 umol/L Serum creatinine > 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
Case History 1
65 yr old admitted 2 months post CABG+AVR 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?
Case 1
Differential: Post-infectious GN Ischemic ATN Athero-embolic disease GENTAMICIN-INDUCED
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
450Urinalysis: trace blood, no protein, no casts?Cause of acute renal failure
Case 2
Differential Ischemic ATN Renal artery thrombosis ATHERO-EMBOLIC DISEASE
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?
CASE 3
Ischemic ATN Obstructive jaundice Gram-negative bacteremia Hypotension
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 ASTPreop 98 125 125 20024 h 175 80 25 150048 h 370 60 10 3500 ?Diagnosis
Case 4
Thrombotic Microangiopathy HELLP syndrome Post-partum acute renal failure
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?
Case 5
Differential Ischemic ATN Abdominal compartment syndrome
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 (> 7 d)
Hypotension with pre-existing renal disease especially in the elderly
Cyclosporine for transplantation
Chronic Kidney DiseaseGFR ml/min
Stage 1 >90Stage 2 (mild) 60-90Stage 3 (moderate) 30-60 Stage 4 (advanced) 15-30Stage 5 End stage KD < 15
GFR measured or calculated using MDRD equation
Causes/Risk Factors for CKD
Risk FactorsDiabetesHypertensionAgeSmokingHigh CholesterolOrgan
transplantation
CausesDiabetic nephropathyHypertension/
vascularGlomerulonephritisPolycystic KidneysObstructionMultiple myelomaCalcineurin-inhibitors
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 patient’s kidney function and why?
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
What if More Nephrons are Lost?
Increased single nephron GFR by afferent and efferent arteriolar dilatation
If lose > 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: > 1 g/d is bad, >3 g
worse
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
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
O.R. of Death at 30 d. Post CABG
>100 80-99 60-79 40-59 0-390
1
2
3
4
5
6
Lok et al:Am Heart J 2004
Creatinine Clearance ml/min
Impact of Renal Dysfunction on Outcomes of CABG
02468
1012141618
1 2 3 4 5
CKD Stage
DeathsStroke> 14 days
Circulation 2006;113:1063
485,000 US patients 2002-3
Mortality Following Arterial Surgery
Elective Urgent All0
10
20
30
40Renal FailureNormal
Gerrard et al:Br J Surg 2002;89:70
Type of Surgery
%
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
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?
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
riskPlan: (Nothing evidence-based!) request nephrology; cardiac assessment will renal disease progress anyway? -
operate when on dialysis?
Case History 6
Surgery is planned after cardiac assessment
Maintain as stable a BP as possible and avoid hypotension ( < 130 systolic in this patient)
Accurate fluid replacement to avoid volume depletion or overload
Monitor serum potassium (daily lytes)
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%
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)
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
Prevention of Postoperative Hyponatremia
Avoid hypotonic fluid unless the patient is hypernatremic
Limit volume of I.V. fluid given to meet patient’s needs
Adjust volume to patient’s body weight
Peri-operative IV Fluid Annals Surgery 2003;238:641 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
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
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
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*
Complication frequency related to IV fluid and wt gain on operative day
A Comparison of Albumin and Saline for Fluid Resuscitation in the Intensive Care Unit
NEJM 2004;350:2247 Previous meta-analysis suggested
albumin resuscitation increased mortality
RCT in 7,000 ICU patients 4% albumin vs crystalloid for fluid No difference in mortality
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