fluid balance and iv fluid therapy
TRANSCRIPT
Fluid Balance and IV Fluid Therapy
Mike Bowe
Critical Care Pharmacist
Queen Elizabeth Hospital, Gateshead
Learning outcomes
• Understand principles of fluid distribution within the
adult body
• Understand the principles of fluid balance
• Understand the differences between fluid
maintenance and resuscitation
• List available fluids and their place in treatment
Fluid distribution
• Haemodynamic forces:
• Changes in blood
volume affect cardiac
output & circulation
• Autonomic control
• Starling’s hypothesis:
• If hydrostatic
pressure>osmotic
pressure, fluid leaves
capillary & vice versa
Normal composition of major body fluid compartments
Plasma (mmol/L) Interstitial Fluid (mmol/L)
Intracellular Fluid(mmol/L)
Na+ 142 144 10
K+ 4 4 160
Ca2+ 2.5 2.5 1.5
Mg2+ 1.0 0.5 13
Cl- 102 114 2
HCO3- 26 30 8
PO42- 1.0 1.0 57
Protein 16 0 55
Intracelluar fluid
• Volume controlled by water balance:
• Intake controlled by thirst
• Excretion controlled by ADH
• Volume decreases with illness
• Most potassium is intracellular
Extracellular fluid
• Made up of interstitial and intravascular (plasma)
compartments
• Volume controlled by sodium balance
• Volume increases with illness
Fluid balance
• Vital to know what goes in and what comes out
Water balance
• Osmolarity
• Plasma osmolarity >280mOsmol/kg
• Sensitises central osmoreceptors stimulates thirst response
• ADH secreted water reabsorbtion
• Circulating volume
• blood volume (atrial stretch receptors) and BP (baroreceptors)
• ADH secreted water reabsorbtion
Intake controlled by thirst
Excretion controlled by ADH (vasopressin)
Where Do We Gain Fluid?
• Need around 25-30ml/kg/day (but may range from 20-60ml/kg/day)
• Women = 2l/day
• Men = 2.5l/day
• Need 1mmol/kg each of K+ & Na+
• Need 50-100g/day glucose
Ingested Liquids
(1500ml/day)
Ingested Moist Food
(800ml/day)
Metabolic Water
(200ml/day)
Where Do We Lose Fluid?
• Water loss:
• Dehydration
• From ICF & ECF
• Na+ & H2O loss:
• From ECF (plasma – small
quantity & ISF)
• Blood loss:
• From ECF (plasma then
interstitial fluid)
Kidneys
(1500ml/day)
Skin
(600ml/day)
Lungs
(300ml/day)
GI Tract (100ml/day)
NICECG 1742013
Urine
• Minimum 0.5ml/kg/hour
• Usually 1.5-2L/day (20 x weight)
• Needed to excrete metabolic waste products
• Patient’s with oliguria/anuria may need fluid
restriction
Signs of Dehydration
• Thirst
• Dry membranes
• Urine output
• Headache
• Fatigue
• Sunken eyes (&
fontanelle in
babies)
• Skin turgor
• BP (& CVP)
• HR
• Weak, thready
pulse
• Cold peripheries
• Weight loss
• capillary refill
• Serum Na+
• Serum osmolality
• haematocrit
Hypovolaemia
• Refers to isotonic fluid loss from extracellular space
• Excess fluid loss:
• haemorrhage, GI losses, abdo surgery, excess diuretic/laxative Tx,
fever, DM with polyuria
• 3rd space fluid shifts:
• capillary membrane permeability, osmotic pressure
• (also seen in acute intestinal obstruction, acute peritonitis,
pancreatitis, burns, crush injuries, heart failure, hip fracture,
hypalbuminaemia, liver failure, pleural effusion)
Hypervolaemia
• Excess fluid in extracellular space
• Excess Na+ or fluid intake (IVT, blood/plasma products, dietary
Na+)
• Na+ and fluid retention (heart failure, cirrhosis, nephrotic
syndrome)
• Fluid shifts (remobilisation after aggressive IVT, hypertonic fluid
administration)
• Prolonged hypervolaemia oedema (hydrostatic
pressure)
Setting a fluid balance
• Parenteral fluids, parenteral medication,
enteral feeds, enteral fluids
• Urine, N&V&D, filtrate (if RRT),
insensible losses, drain & stoma losses
Assess volume status – Input vs. Output
Assess clinical status – resuscitation/stabilisation/recovery
Inputs
Outputs
Not an exact science and many need to be adapted according to patient clinical condition
Assessment of fluid status
• Systolic BP <100mgHg
• HR >90bpm
• CRT >2sec or peripheries cold to the
touch
• Resp rate >20bpm,
• NEWS >4
• FBC, U&E’s
• Passive leg raising suggests fluid
responsiveness
• Fluid balance charts
• Weight
Assess whether the patient is hypovolaemic and need of urgent fluid resuscitation:
Lab investigations should include current status and trends in:
Type of fluid replacement
Intravenous Fluid
Crystalloids Colloids
NaClHartmann’s
Balanced solutions
Glucose
Blood ProductsPRC
Plts, FFPAlbumin
GelatinsStarches
Crystalloids
• Iso-osmotic with plasma
• Distribution determined by sodium concentration
• Contain low molecular weight salts or sugars dissolved in water
• Require several times more crystalloid than colloid to achieve the same
degree of vascular filling
• Move rapidly into the interstitial space
• Can result in interstitial oedema
• No anaphylactic risk
Solution Na+
(mmol/L)
K+
(mmol/L)
Cl-
(mmol/L)
Ca2+
(mmol/L)
HCO3-
(mmol/L)
Glucose (g/L)
Plasma 135-145 3.5-5 94-111 2.2-2.6 23-27 0.72-1.26
NaCl 0.9% 154 - 154 - - -
Hartmann’s 131 5 111 2 29 -
Plasmalyte 141 4.5 98 - 26 -
Dex/Saline(+ KCl)
31 (0-40) 31 - - 40
Glucose 5% - - - - - 50
Target for 70kg pt
70 70 70 50-100
Sodium Chloride 0.9%
• Disperses throughout ECF not ICF
• Uses:
• Fluid resuscitation
• Replacement of upper GI fluid losses
• Problems:
• Hypochloraemic acidosis
• Hypernatraemia
• 20% remains intravascular at 1 hour
• Commonly used in drug preparations
Glucose 5%
• Electrolyte free, disperses through ICF and ECF as water
• Very small % remains in blood after distribution
• Good source of free water
• Can cause water intoxication, hyponatraemia, hyperglycaemia
• 1L provides 200kcal
• Used for immediate hydration, supply of water over and above
electrolyte requirements, drug administration
Balanced solutions
• Hartmann’s, Plasmalyte
• Electrolyte and pH profile similar to plasma/interstitial fluid
• vs. NaCl 0.9% less hyperchloraemic acidosis
• Shaw et al. compared NaCl 0.9% vs. Plasmalyte in patients undergoing open abdo surgery:
• Less electrolyte disturbances
• Fewer blood transfusions
• Less renal failure requiring dialysis
• Less post-op interventions
• Lactate metabolised and acts as buffer to acidosis
Balanced solutions
• Uses:
• Resuscitation fluid
• Maintenance fluid
• Replacement of large stoma losses
Hartmann’s first choice for resuscitation and maintenance
Glucose 4%/Sodium Chloride 0.18%(+KCl)
• Isotonic solution
• Useful where fluid depletion from all compartments eg. diabetes
insipidus
• Useful for maintenance but not to be used for resuscitation or
replacement
• Risk of hyponatraemia, especially in the elderly
Ideal maintenance fluid??
Colloids
• Large osmotically active molecules in an electrolyte solution (NaCl
0.9% or balanced solution)
• Remain in the plasma for longer than crystalloids so faster and more
prolonged plasma expansion
• Issues:
• Lack of evidence for benefit over crystalloids
• More expensive
• Anaphylactic risk
• Can effect coagulation
• Some evidence of harm
• Unsuitable for the Tx of dehydration
Gelatins
• Plasma volume expander
• Derived from bovine gelatin
• Wide variation in molecule size
• Provide good initial volume expansion ( 1 hour)
• Plasma t1/2 2-4 hours
• May impair haemostasis by affecting platelet function and coagulation
• May cause more kidney injury
• Stimulates histamine release
Human Albumin Solution
• Prepared from whole blood
• Contains soluble proteins suspended in NaCl
• Expensive
• Can worsen oedema as albumin will leak into interstitium
4.5%Isotonic
Volume replacementBurns
Ascitic fluid loses?
20%Hypertonic
Volume expanderHypo-oncotic intravascular volume
depletion with oedemaAscitic fluid loses
• Compared the effects of HAS 4% vs. NaCl 0.9% in 7000 critically ill pts
• No difference in all cause mortality at 28 days
• Subgroup analysis revealed possible association between the use of
HAS and increased mortality in patients with TBI
Where Does 1L Fluid Go?
Fluid IntracellularFluid
Extracellular Fluid
Interstitial Space Intravascular Space
Glucose 5% 666ml 222ml 111ml
Sodium chloride 0.9%
666ml 333ml
Colloid 1000ml
Does the patient need IV fluid?
5 R’s
Resuscitation
Routine maintenance
Replacement and Redistribution
Reassessment
Sepsis – why do you need fluids?
Activation of inflammatory cascade
vascular permeability and fluid shifts
Hypovolaemia Shock
Sepsis Fluid Resuscitation
• 1st line Hartmann’s (preferred) or NaCl 0.9%
• Consider HAS 4.5% as resuscitation fluid for severe
sepsis
• Fluids very important but aggressive early
treatment does not give improved outcome
(Mouncey, NEJM, 372:14)
Burns – why do you need fluids?
Activation of inflammatory cascade
vascular permeability and fluid shifts
Hypovolaemia Shock
Burn (>15%)
Exudation
Burns Fluid Resuscitation
• Treat from time of burn, not time of arrival
• Aims:• Adequate CVP, BP & cardiac output• Urine output 0.5-1ml/kg/hour
• First 24 hours:• Hartmanns (preferably) or NaCl 0.9%• 3-4ml/kg/%burn• Give first half in first 8 hours then rest over 16 hours
• After 24 hours:• Adapt fluids (colloids or crystalloids) to patient• May need Glucose 5%• Give electrolytes
Post-op – why do you need fluids?
• Fluids given in Theatre & Recovery to replace deficit from fasting and
intra-op blood loss
• Routine maintenance fluid should not be needed for minor procedures
(unless not drinking for several hours-days)
• Fluids may be required to manage ongoing fluid losses
• Monitor drain losses, vital signs, urine output, biochem
Pharmacist’ Role With Fluids
• Fluids are drugs and just as dangerous
• Awareness:
• What is the patient on? Rate?
• Appropriateness:
• Reasonable fluid for situation?
• Response:
• Urine output? Electrolytes?
Summary
• How fluids are distributed in the body
• Types of fluid
• Associated with organ dysfunction
• Resuscitation Stabilisation ReassessmentHypovolaemia
• Think Hartmann’s (or NaCl 0.9%)
• Not colloids in ITU (?HAS in severe sepsis)Resuscitation
• Remember normal daily fluid and electrolyte requirements
• 25-30ml/kg/day water
• 1mmol/kg Na+/K+/Cl-
• 50-100g/day glucose
• Avoid too much Na+ and Cl-
Maintenance
References• NICE, Intravenous fluid therapy in adults in hospital, CG 174, 2013
• British consensus guidelines on intravenous fluid therapy for adult surgical
patients (GIFTASUP), 2012
• Myburgh, J. A. & Mythen, M. G., Resuscitation fluids, NEJM, 2013, 369; 13:
1243-1251
• Mouncey, P. R. et al, Trial of early, goal-directed resuscitation for septic
shock, NEJM, 2015, 372; 14 1301-1311
• Shaw AD et al. Major complications, mortality, and resource utilization
after open abdominal surgery: 0.9% saline compared to Plasma-Lyte. Ann
Surg, 2012 May;255(5):821-9
• National Plasma Product Expert Advisory Group. Clinical Guidelines for
Human Albumin Use. www.nsd.scot.nhs.uk
Thanks to Nic Corkhill, Emma Boxall, Fraser Hanks & Ruth Roadley-Battin