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