Download Induction to Medical on-calls

INTRAVENOUS FLUID THERAPY
Tom Heaps
Consultant Acute Physician
LEARNING OBJECTIVES
1. Crystalloids vs colloids
2. Balanced vs non-balanced solutions
3. Composition of various IV fluids
4. What is normal about ‘Normal’ Saline?
5. Goals of fluid therapy
6. Recognizing and managing hypovolaemia
7. Daily electrolyte and fluid requirements
8. Maintenance, Replacement and Redistribution
9. Summary: The 5 Rs and NICE CG174
WHAT IS THE PROBLEM WITH FLUID THERAPY?
‘Cautious IV Fluids…..
…..Because the patient has angina?!’
THE ‘POPCORN’ MODEL OF FLUID THERAPY
Daily fluid requirement =
QUESTIONS TO ASK BEFORE PRESCRIBING FLUID
1. Does my patient need IV fluid?
2. For what purpose?
3. What type of fluid?
4. What amount (volume) of fluid?
5. What rate (how fast)?
ENGAGE BRAIN!
DAILY ELECTROLYTE REQUIREMENTS
1. Sodium
• 1-2mmol/kg/d (70-140mmol/d)
• Serum concentration 140mmol/L
2. Potassium
• 0.5-1mmol/kg/d (35-70mmol/d)
• Serum concentration 4mmol/L
3. Chloride
• 1mmol/kg/d (70mmol/d)
• Serum concentration 100mmol/L
1mmol/kg/d
of each
WHAT’S IN YOUR CUPBOARD?
1. Crystalloids (hopefully)
• Isotonic (‘normal’) 0.9% saline +/- 20-40mmol KCl
• Hartmann’s solution
• 5% and 10% glucose
• 4% glucose—0.18% saline (‘dex-saline’) +/- 20-40mmol KCl
• Plasmalyte 148 (ITU)
2. Colloids (rarely)
• Albumins
• Gelatins e.g. Gelofusine®, Volplex®
• Starches
WHAT’S NORMAL ABOUT ‘NORMAL’ SALINE?
Tonicity (‘isotonic’….almost)
• Osmolality
308mOsmol/L
(275-295mOsmol/L)
…..and not a lot else!
• Sodium
154mmol/L
(140mmol/L)
• Chloride
154mmol/L
(100mmol/L)
• pH
5.5
(7.4)
• Potassium
0mmol/L
(4mmol/L)
COMPOSITION OF DIFFERENT CRYSTALLOIDS
Content
(mmol/L)
Plasma
0.9% Saline
Hartmann’s
Plasmalyte 148
5% Glucose
0.18%
Saline-4%
Glucose
Sodium
140
154
131
140
0
31
Potassium
4
0
5
5
0
0
Chloride
100
154
111
98
0
31
Lactate etc.
<2
0
29
0
(gluconate 23,
acetate 27)
Calcium
2.4
0
2
0 (Mg 1.5)
0
0
Glucose
4.5
0
0
0
278 (50g)
222 (40g)
pH
7.4
5.5
6.0
6.0
4.5
4.5
Osmolality
285
308
278
295
278
284
0
WHAT HAPPENS IF YOU GIVE ‘NORMAL’ SALINE?
• pH depends on difference between strong +ve ions (e.g. Na+) and strong –ve
ions (e.g. (Cl-) = strong ion difference (Stewart’s Theory)
• Physiological strong ion difference ≈ 40mmol/L (140 – 100)
• 0.9% Saline contains 154mmol/L Na+ and 154mmol/L Cl• Chloride rises disproportionately to sodium reducing the strong ion gap and
pH resulting in (hyperchloraemic) acidosis
• Renal vasoconstriction and impaired secretion of sodium
• Clinicians often respond to acidosis by giving more fluids…
• Don’t forget, 0.9% saline is also present in colloids e.g. HAS, Gelofusine®,
Volplex®, Voluven®
• Balanced colloids now available e.g. Gelaspan®, Isoplex®, Volulyte®
MYTHS ABOUT BALANCED CRYSTALLOIDS…
‘…but it’s got potassium in it…’
• Hyperchloraemia causes acidosis which exacerbates hyperkalaemia
• Normal saline may raise [K +] more than balanced solutions in AKI
O’Malley et al, Anesthesia and Analgesia, 2005
‘…but it’s got lactate in it…’
• Lactate is not bad for you: it is a marker of lactic acidosis and disease severity (in
certain conditions)
• Lactate in Hartmann’s ≠ lactic acid; it is a conjugate base (potential HCO 3-) and will
NEVER increase acidosis
• The patient will be making a lot more lactate (1500mmol/24h in health) than you will
be giving therefore effect on total body lactate negligible
THE GREAT FLUID DEBATE CONTINUES…
Balanced vs. non-balanced crystalloids
• 0.9% Saline slightly cheaper than Hartmann’s (£0.78/L vs £1.00/L) but is
associated with hyperchloraemic acidosis:
• Potential for renal vasoconstriction (AKI and hyperkalaemia), impaired GI
perfusion and coagulopathy
• Relevance in terms of clinical outcomes uncertain (large trials on-going)
Crystalloids vs. colloids
• Equivalent patient outcomes in most studies
• Colloids associated with greater expense, risk of anaphylaxis, coagulopathy
and increased risk of AKI (especially starches - withdrawn)
• Albumin probably reasonable choice in sepsis?
FLUID THERAPY: BACK TO BASICS
Restore circulating volume
• Diagnosis and treatment of hypovolaemia
Correct dehydration
• Reduced total body water with preservation of circulating volume
Maintain circulating volume and electrolytes
• Understand and anticipate physiological requirements
RECOGNIZING & TREATING HYPOVOLAEMIA
Treating Hypotension
Hypovolaemia
1.Vital signs and MEWS
Tachycardia
Record patient
observations
Central
Pressure
Urine Venous
output
(Oliguria)
Tachypnoea
2.Diagnostic tests
3.CVP and oliguria
4.The fluid challenge
Choose your weapon!
Cannot
describe
euvolaemia
Does
notDelayed
‘diagnose’
hypovolaemia
capillary
refill
Give 500mL QUICKLY (≤15mins)
IsOliguria
no longer
recommended
as a
should
trigger a volume
Cool
peripheries
Stayresuscitation
by
theraise
patient
and repeat
Passive
leg
test
assessment,
NOT a target
fluid challenge
observations
Autotransfusion
500mL
of blood
Other
(less of
invasive)
means
of from
‘guiding’
Oliguria
may
indicate
dehydration
Repeat
until patient no longer
legs boluses
and
fluidabdomen
resuscitation
hypovolaemic
Urine output is not a good target in the
Effect
maximal
at
30-90s
Helpful
at extremes
ofpatient
filling only
acutely
unwell
If no haemodynamic response after 2L
of fluid (i.e.
–veand/or
test) contact
Critical
10% increase
in sBP
reduction
in Care
HR predictive of fluid responsiveness
GETTING IT WRONG…
Over-transfusion: fluid in the wrong place
• Pulmonary oedema, gut oedema, peripheral oedema, anasarca
• Capillary injury and shedding of EGL
Dry
Wet
Under-transfusion: hypoperfusion and persisting shock
• AKI
• Ischaemic hepatitis / colitis
• Arrhythmias / ACS
• Cerebrovascular events
Multi-organ failure
WET, DRY OR SOMEWHERE IN-BETWEEN?
Dry (Restricted)
Wet (Liberal)
GETTING IT RIGHT FOR MEDICAL PATIENTS…
Dry (Restricted)
Dry
Wet (Liberal)
Wet
Frequent Reassessment is Key!
MAINTENANCE FLUIDS
Dry
25-30mL/kg/day + 1mmol/kg/day of Na +, Cl- and K+
25mL/kg/day of:
0.9%
NaCl
Hartmann’s
4%
Glucose-0.18%
Saline + 40KCl
+
> 4mmol/kg/day Na
Na
3.3mmol/kg/day
> 0.45mmol/kg/day
Na+ +
> 4mmol/kg/day Cl
ClCl
-- > 2.8mmol/kg/day
0.45mmol/kg/day
0.125mmol/kg/day
> 1mmol/kg/day
K+ K+
> 70g glucose
REPLACEMENT
One of the few indications for ‘normal’ saline
SUMMARY: 5 Rs
DISCUSSION
QUESTIONS
COMMENTS