Post on 31-Mar-2020
transcript
Dr Ross Freebairn Hawke’s Bay N.Z.
Renal Replacement Therapy What, When, Why & How Much.
Oliguria
• urine output < 0.5 ml/kg/hr
Matter of perspective
• Heart stops – Cardiac arrest
• Breathing stops – Respiratory arrest
• Kidneys stop – Oliguria – Renal arrest
Acute renal failure
• failure of solute and (usually) water clearance
• common
• associated with increased mortality
Oliguria
• warning sign of impaired tissue perfusion
• leads to acute renal failure if not corrected
• 2 hours’ oliguria MUST be treated urgently
Pathophysiology • outer renal
medulla prone to ischaemia
Pathophysiology
• reduced renal blood flow worsens medullary ischaemia
• ischaemia causes structural changes and ultimately acute tubular necrosis
Management
• treatable factors • hypovolaemia and shock - resuscitate • infection - source control and antibiotics • nephrotoxic drugs - discontinue where
possible • abdominal compartment syndrome -
decompress • rhabdomyolysis - alkalinise, mannitol • hypercalcaemia • obstruction
Resuscitation
• correct hypovolaemia • volume repletion • CVP guidance using serial fluid challenges
• restore cardiac output • vasopressors/inotropes if other evidence of
tissue hypoperfusion • restore perfusion pressure
• may need MAP > 80 mm Hg if previously hypertensive
• volume repletion and vasopressors
Frusemide is NOT
a resuscitation fluid
Dopamine • inconsistent diuretic effect
• but this may cause dehydration • does not
• increase creatinine clearance • prevent acute renal failure
• does cause serious toxicity problems • tachyarrhythmias • exacerbates renal and mesenteric ischaemia • impaired immune function
• fundamentally not useful
Frusemide
• does • reduce juxtamedullary oxygen
consumption • has not been shown to
• improve creatinine clearance • affect survival either way
• disadvantages • of diuresis
• may be used but ONLY after adequate volume resuscitation
Established acute renal failure
Management of renal failure
• avoid volume overload – input = previous hour’s output +20 ml – BUT do not withold nutrition
• treat complications • adjust drug doses • renal replacement therapy
Temporizing measures
• hyperkalaemia • insulin/dextrose, NaHCO3, β2 agonists
• severe acidosis • NaHCO3 infusion
• volume overload • GTN infusion if BP permits • frusemide if still passing urine
Indications for CRRT • Urgent
– Severe ↑ K – Severe metabolic
acidosis – Severe pulmonary
oedema due to fluid overload
– Uraemic pericarditis
• Less urgent/definite – Non-obstructive oliguria
>12 h – Creatinine 2 x baseline – Uraemic encephalopathy,
neuropathy or myopathy – Progressive dysnatraemia – Hyperthermia – Significant oedema – Requirement for large
volume transfusion in patients with/at risk of pulmonary oedema/ARDS
From: Effect of Early vs Delayed Initiation of Renal Replacement Therapy on Mortality in Critically Ill Patients With Acute Kidney Injury: The ELAIN Randomized Clinical TrialJAMA. 2016;315(20):2190-2199. doi:10.1001/jama.2016.5828
Mortality Probability Within 90 Days After Study Enrollment for Patients Receiving Early and Delayed Initiation of Renal Replacement Therapy (RRT)KDIGO indicates Kidney Disease: Improving Global Outcomes. In the delayed group, 18 patients received RRT without reaching KDIGO stage 3 (these patients had an absolute indication). The median (quartile 1 [Q1], quartile 3 [Q3]) duration of follow-up was 90 days (Q1, Q3: 90, 90) in the early group and 90 days (Q1, Q3: 90, 90) in the delayed group. The vertical ticks indicate censored cases.
Factors affecting RRT
Patient focused System Imposed Clinician Influenced
Comorbidity Health structure Indications (timing)
Kidney reserve ICU organization Prescription
Metabolic rate Resource /Costs Local Practice
Primary diagnosis Resource/ equipment Goals of therapy
Continuous venovenous haemodiafiltration--an audit demonstrating control of electrolytes with haemodynamic stability in the critically ill. Freebairn RC, Lipman J. S Afr J Surg. 1994 Jun;32(2):77-82
80
85
90
95
100
105
110
115
Heart rate MAP SBP CVP
Time 036hrs
Pump
Ultrafiltrate
Pump
Replacement fluid
Solute
Plasma protein
Replacement fluid
Ultrafiltrate
Blood
Haemofilter membrane
Replacement fluid
• Determines plasma electrolyte concentration
• Bicarbonate lost, needs to be replaced
Replacement fluid
• Bicarbonate replacement – Bicarbonate – Lactate
• Metabolized to bicarbonate by liver (or not!)
• Risk of metabolic acidosis
Dialysate
Effluent
Dialysis fluid
• Solutes will reach equilibrium • Plasma electrolyte & bicarbonate
concentration will tend towards dialysis fluid concentration
Anticoagulation
• None • Heparin
– Unfractionated – Low molecular weight
• Citrate • Prostacyclin • Systemic anticoagulation
Anticoagulation
• Avoid: – Active, recent bleeding evident – Baseline INR >2, APTT >60s, platelets
<60 • Relative contra-indications
– Less severe coagulopathy/thrombocytopaenia
– Surgery within 24 h
Summary
• Haemofiltration – convection • Haemodialysis – diffusion • Adjust dose (effluent rate) according
to patient’s needs, interuptions to treatment – Starting point 25 ml/kg/h
• Consider need for anticoagulation • Caution when starting CRRT in
haemodynamically unstable patients
Outcome with IRRT vs CRRT (3)
Vinsonneau, S et al. Lancet 2006; 368: 379-‐385
Choice of RRT • 1218 patients CRRT or IRRT for ARF • 54 ICUs in 23 countries. • Multivariable logistic regression
– choice of CRRT • Not independent predictor of
– hospital survival – dialysis-free hospital survival.
• But is predictor of dialysis independence at hospital discharge among survivors (OR: 3.333, 95% CI: 1.845 - 6.024, p<0.0001).
Uchino S et al Patient and kidney survival by dialysis modality in critically ill patients with acute kidney injury. Int J Artif Organs. 2007 Apr;30(4):281-92.
0
.2
.4
.6
.8
1
0 20 40 60 80 100
IRRT
CRRT
days
Recovery from Dialysis Dependence- BEST Re
cove
ry fr
om d
ialy
sis
depe
nden
ce
Uchino S et al Patient and kidney survival by dialysis modality in critically ill patients with acute kidney injury. Int J Artif Organs. 2007 Apr;30(4):281-92.
How much replacement and dialysate do you use?
100 90 80 70 60 50 40 30 20 10
0
Group 1(n=146)
( Uf = 20 ml/h/Kg) Group 2 (n=139) ( Uf = 35 ml/h/Kg)
Group 3 (n=140)
( Uf = 45 ml/h/Kg)
41 % 57 % 58 %
p < 0.001 p n..s.
p < 0.001
Sur
viva
l (%
)
Effects of different doses in CVVH on outcome of ARF - Ronco & Bellomo study. Lancet . july 00
Conclusions:
• An increased treatment dose from 20 ml/h/kg to 35 ml/h/kg significantly improved survival.
• A delivery of 45ml/kg/hr did not result in further benefit in terms of survival, but in the septic patient an improvement was observed.
Effects of different doses in CVVH on outcome of ARF - Ronco & Bellomo study. Lancet . july 00
High Volume 37 vs 70 ml/kg
Joannes-Boyau O et al High-volume versus standard-volume haemofiltration for septic shock patients with acute kidney injury (IVOIRE study): a multicentre randomized controlled trial Intensive Care Med (2013) 39:1535–1546
• Blood Purification: It must work!!! • maybe, • possibly, • Unlikely, • No
Never let evidence get in the way of a good opinion
• The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd; indeed in view of the silliness of the majority of mankind, a widespread belief is more likely to be foolish than sensible.
Bertrand Russell, Marriage and Morals (1929)
Recommendation • Renal replacement therapy
– When • Acute renal Failure • Exogenous toxin removal (lithium) • Early may be better-Probably is !!!!
– Dose : • 35+ ml/kg/hr (averaged) • No evidence for high dose
– Mode : • Whatever works for you
– Frusemide is not a resuscitation fluid