Fluid Management

The NICE clinical guideline (CG 174) RCP Acute Medicine

23rd May 2016

Under/ Over-hydration: cause significant morbidity + mortality (e.g. pulmonary oedema, AKI). The problem is widely recognised by healthcare professionals

Extent: difficult to quantify: multifactorial + under-reported (91% Cons/SpR report seeing greater than >5 to >20 adverse fluid events and 89% never or rarely reported)

Mortality: ~9000 ‘estimated’ deaths/year due to poor fluid management in the USA

Morbidity: fluid-related complications in 17-54% of post-operative patients (↑ length of stay 3-14 days)

Arieff AI. Chest 1999;115:1371-1377.

Walsh SR. Ann R Coll Surg Engl 2005;87:126-130

Potential causes:

Education: many errors due to inadequate knowledge in junior medical staff (e.g. N/Saline sodium content). Senior clinicians not much better!

Poor supervision / low priority: >80% post-operative fluid prescriptions by junior clinicians (with no senior reviews).

Poor documentation: <50% fluid charts adequate (NCEPOD). Fluid administration rate considered unimportant in one study!

Callum KG. 1999 NCEPOD enquiry into perioperative deaths. London, 1999

Walsh SR et al. International Journal of Clinical Practice 2008;62:492

Rooker JC, Gorard DA. Clinical Medicine 2007;7:482-485.

Telephone survey 100 HOs in 25 DGH & Teaching Hospitals:

FY did 89% the fluid and electrolyte prescribing

(Lobo et al Clinical Nutrition 2001;20:125-130)

73% knew the minimum acceptable urine 24h output

24% knew the Na+ & Cl- content of 0.9% saline

18% knew the daily Na+ requirements

2% knew the Na+ & Cl- content of gelofusine

1. What is in the fluid administered? (i.e. what are we putting in?)

2. What are the normal daily fluid/electrolyte requirements? (i.e. how

much do we need?)

3. How is administered fluid distributed and how much remains

intravascular? (i.e. where does the fluid ‘go’)?

4. How are administered fluid + electrolytes subsequently excreted?

(i.e. in particular how does the body excrete excess administration?)

5. How does a pathophysiological insult alter fluid/electrolyte

handling? (e.g. effect on intravascular volume during sepsis?)

How competent are YOU?

b. How much sodium does a normal person require daily (in mmol)?

a. 10-60 b. 70-120 c. 130-180 d. 190-240 e. 250-300

c. What is the maximum urine concentration that can be generated by normal kidneys (mOsm/L)?

a. 600 b. 1200 c.1800 d. 2400 e. 3000

d. 4 hours after administration of 1L of normal saline, how much is left in the vascular compartment (in mls)?

a. ~70mls b. ~125mls c. ~175mls d. ~225mls e. ~300mls

e. How much water is bound to 1 gram of albumin (in mls)?

a. ~6 b. ~12 c. ~18 d. ~24 e. ~30

Lobo DN et al. Clin Sci 2001;101:173; Gosling P. Care of the critically ill 1995;11:57; Lobo DN. Basic concepts of fluid + electrolyte therapy 2013

a. How much sodium is in a litre of normal

saline (in mmol)?

a. 74 b. 104 c.124 d. 134 e. 154

Med Cons 86% Med SpR 73% FY1/CMT 68%

Med Cons 71% Med SpR 39% FY1/CMT 42%

Med Cons 57 % Med SpR 29% FY1/CMT 18%

Med Cons 29% Med SpR 25% FY1/CMT 13%

Med Cons 14% Med SpR 31 % FY1/CMT 39 %

So how do we do?

Algorithm 1: Assessment

Using an ABCDE (Airway, Breathing, Circulation, Disability, Exposure) approach, assess whether the patient is hypovolaemic and needs fluid resuscitation Assess volume status taking into account clinical examination, trends and context. Indicators

that a patient may need fluid resuscitation include: systolic BP <100mmHg; heart rate

>90bpm; capillary refill >2s or peripheries cold to touch; respiratory rate >20 breaths per

min; NEWS ≥5; 45o passive leg raising suggests fluid responsiveness.

Algorithm 2:

Fluid Resuscitation

Yes

No

Assess the patient’s likely fluid and electrolyte needs • History: previous limited intake, thirst, abnormal losses, comorbidities.

• Clinical examination: pulse, BP, capillary refill, JVP, oedema (periph/pulmonary), postural hypotension

• Clinical monitoring: NEWS, fluid balance charts, weight.

• Laboratory assessments: FBC, urea, creatinine and electrolytes.

Can the patient meet their fluid and/or electrolyte needs orally or enterally?

Ensure nutrition and fluid needs are met Also see Nutrition support in adults (NICE

clinical guideline 32).

Does the patient have complex fluid or electrolyte replacement or abnormal distribution issues? Look for existing deficits or excesses, ongoing abnormal losses, abnormal distribution or other complex issues.

Algorithm 4:

Replacement + redistribution

No

Yes

Yes

Algorithm 3:

Replacement + redistribution

No

Requirements:

◦ 1. Replace normal fluid +electrolyte losses

◦ 2. Adjust for additional losses/gains depending on pathology

◦ 3. Consider potential redistribution problems (e.g. sepsis)

Need to assess:

◦ 1. Normal fluid and electrolyte requirements

◦ 2. Clinical features, pathology and ECF/ICF status

◦ 3. Serum electrolytes: Na+, urea, HCO3, Cl-

◦ 4. Fluid input and losses (i.e. renal function)

Adjustments required for

- feeding failure

- CVVH (do not need maintenance fluids)

Claude Bernard (1813-1878)

‘La fixité du milieu intérieur est la

condition de la vie libre; ’

Preservation of cellular environment

Sea Water

Na+ 133 mmol/L

K+ 2.8 mmol/L

Cl- 92 mmol/L

Ca++ 2.9 mmol/L

The physiology of fluid and sodium handling in health and disease

We evolved in an environment with wide variations in water

availability but a paucity of salt.

Response to low sodium intake is rapid and efficient

Exposure to excess salt intake is a recent problem

Response to excess sodium is slow and ‘passive’

(even more so in unwell patients)

Basic Physiology: Fluid distribution

Total Body water 42 litres (~42kg)

Extracellular fluid (ECF) ~ 17 litres

Interstitial Space Interstitial Fluid (ISF) ~14 litres

Vascular Space (5 litres)

Plasma (non cellular blood) 3 litres

Intracellular fluid (ICF)

~ 25 litres

H2O

Red Blood Cell

Red Blood Cell

H2O

Red Blood Cell

Na+

Capillary

endothelium Albumin

Water

Na+ 140,

chloride 105,

K+ 3.7

Normal Saline

K+ 155,

phosphate 105,

Na+ 10,

chloride 3

5% Dextrose (water)

Na+/K+

Pump

Na+

K+

Repulsion of

albumin by

negative charged

collagen

Albumin + Hb

pull water

into blood vessels

Normal person given 1L of:

Fluid Volume of Amount in

Type Distribution circulation (4hrs)

5% Dextrose 42 litres ECF+ICF 3/42 x1L =

N/saline 17 litres (ECF) 3/17 x1L =

71 mls

176 mls

Effects of 2000 mL acute fluid loading in volunteers.

Blind cross over trial

Lobo et al Br J Surg 2001

Excess Chloride

Hyperchloraemic metabolic acidosis (HCMA)

- Excessive Cl- ion administration causes HCMA

- Accounts for up to 1/3rd of the acid load (e.g. sepsis)

- HCMA increased in all studies (e.g. postoperative) of

N/Saline vs Physiologically balanced sol (e.g. Hartmann’s)

Kellum JA et al. Crit Care 2004; 8: 331-336

Does this make a difference?

HCMA causes:

- Decreased mental acuity

- Abdominal discomfort, nausea & vomiting

- Reduced urine flow

In Health - Normal urine output 1ml/kg/hr (70mls/hr; ~1.5L/day)

- Maximum renal concentrating ability ~1000-1200 mOsmol/L

In Disease - Urine output often falls ≤0.5ml/kg/hr (35mls/hr; 0.75L/day)

- Max renal concentrating ability falls by up to 50% (i.e. ~500 mOsmol/L)

- Normal daily solute load is ~700mOsmol

(400 mOsmol urea waste + 200 mOsmol of Na+ + Cl- (100mmol NaCl)

and 100 mOsmol K+ + Cl- (50mmol KCl)

In health need ~700mls/urine to excrete 700mOsmol

Therefore capacity for solute excretion ~400mOsmol/day BUT

Catabolic urea waste increases to ~1000 mOsmol

Na+ +Cl- load can be large (6L N/saline = 308 x 6 = 1848 mOsmol)

= SOLUTE RETENTION

Large IV fluid volumes (6L)

= FLUID RETENTION

Key Messages: Normal concentrating

ability of kidneys is 1000mOsm/L (which

falls during illness to ~500mOsm/L often

in association with a fall in urine output)

Med Cons 57%

Med SpR 29%

FY1/CMT 29%

Fluid losses Urine water (70mls/hr = 70 x 24) = ~ 1500mls water/day

Insensible fluid losses: breathing = ~ 400mls/day (pure water)

: sweat = ~ 100mls/day (water + some salts)

Electrolyte losses Urine electrolyte losses = Na+ ~70-120mmol; K+ ~40-70mmol

Daily requirements 1. Water requirement = 1500mls (urine) + 500mls (breath/sweat) = ~2000 mls/day (30mls/kg/day)

2. Electrolyte requirements

= ~70-120mmol Na+ + ~40-70mmol K+

Algorithm 3: Routine Maintenance

Give Maintenance iv fluids Normal daily fluid and electrolyte requirements: • 25-30 ml/kg/day water • 1 mmol/kg/day sodium, potassium and chloride • 50-100 g/day glucose (i.e. 5% dextrose sol contains 50g/L)

Reassess and monitor the patient • Stop iv fluids when no longer an appropriate indication • Nasogastric fluids or enteral feeding are preferable when

maintenance needs are >3days

90 year old lady with AF, weighing 50kg, presents with a minor stroke and significantly impaired swallowing reflex. Well hydrated at admission with normal electrolytes, creatinine 102𝜇mol and good urine output. She requires intravenous fluid. Please prescribe.

Requirements

Water = 25-30mls/kg/day = 25 x 50 = 1250mls/day

Electrolytes = Na+ 1mmol/kg/day = NaCl 50mmol/day

= K+ 1mmol/day = KCl 50mmol day

Glucose = 50g glucose/L 5% dextrose = 50-100g/day

Possible regime

0.5L N/Saline and 1L 5% dextrose (+20ml KCl/bag)

Med Cons 33% Med SpR 13% FY1/CMT 10%

Algorithm 4: Replacement and redistribution

Existing fluid or electrolyte deficits

or excesses

Check for: • Dehydration • fluid overload • hyperkalaemia/ hypokalaemia Estimate deficits or excesses

Ongoing abnormal fluid or electrolyte losses

Check ongoing losses + estimate amounts. Check for: • vomiting + NG tube loss • biliary drainage loss • high/low volume ileal stoma loss • diarrhoea/excess colostomy loss • ongoing blood loss, e.g. melaena • sweating/fever/dehydration • pancreatic/jejunal fistula/stoma

loss • urinary loss, e.g. post AKI polyuria.

Redistribution and other complex issues

Check for: • gross oedema • severe sepsis • hyper/hyponatraemia • renal, liver +/or cardiac

impairment. • post-operative fluid retention +

redistribution • malnourished + refeeding issues

Seek expert help if necessary + estimate requirements

Prescribe by adding to or subtracting from routine maintenance, adjusting for all other sources of fluid and electrolytes (oral, enteral and drug prescriptions)

Monitor + reassess fluid and biochemical status by clinical + laboratory monitoring

One day postoperatively a 56 year old lady, weighing 70kg, needs fluids prescribing for the next 24hrs. Assessment notes 2L of nasogastric tube drainage, normal urine output, haemodynamic stability, hypokalaemia (K+ 3.5mmol/L) and pH 7.56 on blood gases.

Requirements = Normal maintenance requirements

+ additional losses (in this cases 2L NG fluid)

Possible fluid regime

= 2.0L N/Saline + 2L 5% dextrose + 20mmol (or more) K+/1L bag

Water needs Maintenance fluid = 30x70 =2100mls NG fluid replacement = 2000mls

= 4100 mls of water

Electrolyte needs

Na+ = 70mmol urine loss + ~250mmol in NG fluid = 300mmol

K+ = >200mmol (kidney corrects alkalosis (H+ loss in NG output)

by excreting K+ in exchange for H+)

A fall in serum K+ of 0.5mmol/l = 200mmol intracellular loss K+

Med Cons 57%

Med SpR 55%

FY1/CMT 36%

of ALBUMIN

CYCLE

120g/day of

albumin returns

to blood via the

lymphatics

120g/day of

albumin ( )

leaks into ICF.

Albumin half

life is 21 days

= 15g loss of

albumin day

Gosling P. Care of the Critically ill 1995;11:57

VASCULAR

POOL 120g

Na+

Na+

EXTRA

VASCULAR

POOL 150g 15g/day

albumin

synthesised

by liver

• 1g albumin binds ~18mls water

• 120g albumin in circulation

= 120 x 18mls = 2160mls water bound in intravascular space

About 750mls water bound by haemoglobin / globulins

Blood proteins responsible for COP?

- Albumin ~ 65-80% COP

- Haemoglobin ~ 20-25% COP

- Globulins ~ 5% COP

Plasma oncotic pressure (i.e. protein in the blood vessels) pulls

fluid into the circulation and maintains blood pressure

3 days post resuscitation + antibiotics a 70 year old, is oedematous++ and has mild AKI (Urea 14; creat 150). Her weight is 72kg (prev 60kg). HR is 90/min, BP 100/50 mmHg, Na+ 129 and albumin 18g/L. Staff are concerned about a urine output of 20mls/hr.

Plank et al, Ann Surg 1998

Would you:

Give more fluid

Restrict all fluids

Give diuretics

Wait and see

Septic patients can gain >10L of body water during resuscitation. Little is in the vascular compartment (low albumin. It can take up to 3 weeks to excrete this excess fluid (± electrolyte) load

X

Med Cons 43%

Med SpR 43%

FY1/CMT 50%

Give a further fluid bolus of 250–500 ml of crystalloid .

Seek expert help

Does the patient have signs of shock?

Initiate treatment • Identify cause of deficit and respond. • Give a fluid bolus of 500 ml of crystalloid (containing sodium in

the range of 130–154 mmol/l) over 15 minutes.

Algorithm 2: Resuscitation

>2000 ml given?

Assess the patient’s likely

fluid and electrolyte needs (see algorithm 1)

Reassess the patient using the ABCDE approach Does the patient still need fluid resuscitation? Seek expert help if unsure

No

Yes

Yes

Yes No

No

Choi PT, et al. Crit Care Med 1999; 27:200–210

Crystalloids vs. colloids in fluid resuscitation:

A systematic review.

Crysta

lloid

HES

p

CVVH 19% 31% 0.001

Acute renal

failure

23% 35% 0.003

Transfusion 69% 76% 0.07

Bleeding

events

3.6% 5% 0.52

Transfused

RBC’s

4 6 <0.001

VISEP Trial (Hemohes vs. Crystalloid) Morbidity

Fluid therapy is a powerful intervention and timing

is key (e.g. sepsis)

Correct daily maintenance requirements for

additional losses or gains

The use of ‘physiologically balanced’ intravenous

fluids may be associated with an improved outcome

Colloids may be associated with worse outcome