Fluid optimisation for the surgical patient

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Fluid optimisation for the surgical patient

• Natalie Smith
• Senior Staff Specialist Anaesthetist
• Wollongong Hospital
• Combined SIG meeting Byron Bay 2009

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• What type?
• How much?

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Choice of fluid affects

• Haemodynamic optimisation
• Pain
• N V
• Bowel function
• Respiratory function
• Inflammatory response
• Wound anastamosis and healing

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What type?

• Crystalloids
• - N/S
• - Hartmanns solution
• - Plasmalyte
• Colloids
• - Albumin
• - Dextrans
• - Gelatins
• - Starches

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• N/S
• - hyperNa, hypertonic
• - acidotic
• - very hyperCl -gt met acidosis - ?significance
  mask real BE
• - delayed micturition, dec. U/O, more abdominal
  discomfort,
• more blood products
• - no other electrolytes
• CSL / Hartmanns
• - hypoNa, hypotonic
• - excess ionised Ca
• - lactate -gt met alkalosis
• Plasmalyte
• - much more balanced
• - hypertonic
• -gt met alkalosis

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Adverse effects volume!

• Lowell et al Critical Care Medicine 1990
• - 48 pts, 40 had weight gain gt 10 pre-op
• - Increased morbidity, ICU admission
• - Increased mortality (32 v 10), correlated
  with weight gain
• - all those gt 20 gain - gt died
• Repeated in subsequent better studies
• Comparisons b/n normal (3L/24hr) with high
• volume (5-6l/24hr) crystalloid HES volume
  replacement

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Other adverse effects

• Microcirculation (eg endothelial swelling
  activation, capillary leakage, tissue PO2)
• Macrocirculation (tissue oedema)
• Inflammation
• More PONV, postop pain, periorbital oedema and
  double vision, GIT oedema with impaired
  function..

(Moretti et al Intraop colloid dec PONV and inc
postop outcomes Anesth Analg 200396611-7)
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Are crystalloids out?

• Important to limit use
• Use balanced solutions
• Does not mean deprivation
• Means avoiding overload
• 2-3 L/d good for most surgery
• Important to treat hypovolaemia with colloid and
  blood products.

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Colloids
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Albumin

• Single MW 69 kD
• Human origin, highly processed
• ? Poison Cochrane yes, SAFE - no
• Hyperoncotic solutions bad (head injury, renal
  dysfunction, ICU mortality)
• Superiority to other fluids re mortality or
  morbidity never shown
• Mostly very expensive
• Human product

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Dextrans

• Very good volume expanders
• Carrots
• Moderate allergy risk
• Coagulation problems
• XM problems
• Renal problems
• No longer available

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Gelatins

• Small molecular size MW 30 35
• Beef bone/sinew derived protein
• Short acting 1 to 2 hours
• Highest incidence anaphylaxis
• Limited increase in plasma volume expansion

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Starches

• Maize / potatoes
• Hydroxyethyl Starch HES
• Lots of different types
• Big differences between preparations
• Concentration and In vivo MW
• - determines efficacy, tolerance and side
  effects

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Characterisations

• Concentration
• Mean molecular weight
• Molar substitution
• Origin
• Solvent

Boldt J. Seven misconceptions regarding volume
therapy strategies. Editorial BJA
2009103(2)147-151
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Concentration

• 3 hypo-oncotic
• 6 iso-oncotic
• 10 hyper-oncotic

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Molecular weight

• Initial molecular weight
• Molar substitution amount of hydroxyethylation
• C2-C6 ratio pattern of hydroxyethylation
• Target MW 65 70 kDa (renal threshold)

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Substitution

• Amylases eat starch
• Hydroxyethylation makes them resistant to
  degradation, and makes them water soluble
• C2 inhibit access more than on C6
• Pattern of hydroxyethylation (C2/C6 ratio)
• Products with a higher C2/C6 ratio do maintain
  higher plasma levels for longer

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• 6 HES 450 / 0.7
• - in-vivo MW 250 kDa after 24hr
• - Hextend, Hespan
• - oldest, dinosaur, USA
• 6 HES 200 / 0.5
• - in-vivo MW 120140 after 6 hr
• - Pentastarch
• - eloHAES (0.62)
• - 3 and 10 exist
• 6 HES 130 / 0.4
• - in-vivo MW 65 70 after half hour i.e.
  reached target
• - newest, modern, Tetrastarch, 3rd generation
• - Voluven, Volulyte
• - good volume effect with far fewer side-effects

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Efficacy 1
Boldt editorial BJA
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Efficacy 2

• Persistence in plasma and volume effects are not
  related, e.g. Pentastarch and Hetastarch have
  comparable duration effect to Tetrastarch but the
  latter has no plasma accumulation
• Different pharmacokinetics
• Clearance related to MS and C2-C6 ratio
• Colloid oncotic pressure related to number of
  oncotically active particles, e.g. 6 vs 10
• Lower in-vivo MW provides more efficient volume
  expansion as more osmotically active molecules
  for the same weight

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Adverse effects of colloids

• Coagulation
• Renal dysfunction and failure
• Anaphylaxis
• Accumulation
• Rheology

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Coagulation

• All colloids (and fluids!) affect haemostasis
• Partly haemodilution, partly specific
• Crystalloids tend -gt hypercoagulable
• Dextrans worst, gelatins in middle, tetrastarch
  and albumin best.
• Tetrastarch similar to N/S, minimal cf older
  starches (gt 50 studies)

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Renal dysfunction

• ARF?
• Some evidence that older high MW starches may be
  implicated, e.g. 10 200/0.5
• No evidence for tetrastarches -gt renal probs
• Even in high risk populations
• Many studies show better markers with tetrastarch
  than with old starches / gelatin / albumin.
• Very hyperoncotic fluids, e.g. albumin 20

Westphal M et al, HES. Different
products-different effects. Anesthesiology
111(1) 187-202 Jul 2009
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Accumulation

• High MW HES stored in tissue prior to metabolism
  and excretion
• Itch
• Tetrastarches - no plasma accumulation
• - v. few reports of itching

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Beneficial effects

• Additional properties of specific molecules
• Micro-circulation
• Capillary sealing
• Oxygenation
• Anti - systemic inflammation
• Endothelial activation
• ? clinical significance

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• Albumin
• - not dangerous
• - possible risk head trauma (hyperoncotic)
• - expensive with no proved advantage
• Gelatin
• - short duration volume effect
• - gap-filler e.g. before blood arrives
• - minimal coagulation problems
• - allergic risk highest
• Dextran
• - good volume expansion but overall risk /
  benefit not great
• Starch
• - long duration volume effect
• - tetrastarches very safe and widely used (gt50
  countries)

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How much?
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Aims?

• Goal-directed therapy (Schumaker)?
• - set goal, fit pt to goal

X
v
Fluid optimisation? - look at pt, fit goal to pt
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Just right!
Bellamy BJA 2006
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How to measure?

• Cardiac output
• - BP, HR, CVP, PAOP no good
• O2 delivery
• - how?
• End-organ function
• - e.g. urine output, tissue pH, GIT pHi
• - not shown to effect outcome

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Fluid challenge
B
C
A
Grocott et al Perioperative fluid management and
clinical outcomes in adults. Anesth Analg
20051001093-106
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Monitor

• Minimally invasive
• Rapid response
• Reliable
• Robust in variety of clinical situations
• Values easy to understand and interpret

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Possible candidates

• PAC
• - FACTT trial out
• TOE
• - great if you have someone else to do it
• Cardio-respiratory interactions
• - e.g. systolic pressure or pulse pressure or
  stroke volume variations. Measures HD
  performance throughout respiratory cycle
• - swing on art line
• - some promising, some disappointing
• Doppler U/S

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OesophagealDoppler
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Doppler

• Use to assess response to fluid challenge (200ml
  colloid)
• 65 papers, over c. 15 years
• All show improved outcomes re various morbidities
  eg less unplanned ICU admission, shorter length
  of hospital stay, decreased peri-operative
  complications
• Usually in order of 60 difference
• Usual volume of colloid given c 750ml

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Doppler

• Is only measurement device validated against pt
  outcome.
• NHS authorised purchase for all hospitals doing
  major surgery
• Advantage - relatively non-invasive
• - easy
• - lowers thresh-hold
• Problems
• - learning curve
• - difficult to stabilise
• - arrhythmia

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Hypovolaemia 1
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Hypovolaemia 2
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Hypovolaemia 3
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So, what do I do?

• Some fluid is better than none.
• As the magnitude of surgical insult increases,
  choosing a dose of fluid becomes harder.
• Needs to be titrated to physiologically relevant
  end-points.

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Best practice?

• Minimise crystalloid
• - for dehydration (ICF and ECF losses)
• - 3rd space generally over-estimated
• - general aim 2L intra-op plus 1L per 24 hrs
• Optimise plasma volume with colloids
• - choose appropriate type
• - monitor with flow based dynamic system

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My practice?

• I use much more colloid than most other
  colleagues
• I use Doppler
• But less overall fluid volume
• Part of fast-track surgery package, e.g.
  epidural, pre-op warming and fluids, CHO rich
  drinks, minimal pre-op fasting, no bowel
  preparation, early mobilisation etc

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• Guide to minor and major surgery

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• Minor-moderate surgery
• - no anticipated blood loss
• - 2-3L balanced crystalloid per day
• - no need for colloid
• Major / high risk surgery
• - pre-op no bowel prep, encourage fluid
  nutrition
• - optimise O2 delivery and volume with colloid
• - titrate with flow based measures
• - early and keep ahead of losses
• - replace blood loss with colloid to
  acceptable Hct then use blood
• - use efficient colloid with best volume
  effect and minimal side effects