1. Rob Fleming Specialty Doctor – Anaesthetics 22/07/2014 Robert.Fleming@doctors.org.uk

2.  Why is it important?  Basic science  Body fluid compartments  Barriers to fluid movement  Commonly used fluids  Assessing fluid status  Prescribing: the 5 Rs  Summary

3.  Fluid management not (very) complicated, but is often done badly  Inappropriate fluid management can lead to:  Hypoperfusion, renal failure, shock (too little)  LVF, pulmonary oedema (too much)  Electrolyte abnormalities (  /  Na +, K +, Cl - ), peripheral oedema (wrong fluid)  Good fluid management reduces both morbidity and mortality

4.  Water is a large fraction of total body weight:  Adult men: 60%  Adult women 55%  Neonates: 75 - 80%  Total body water: 40L in a 70kg male  Extracellular (ECF) 1/3 – 15L  Intracellular (ICF) 2/3 – 25L

5.  Interstitial 80% – 12L  Plasma 20% – 3L  “Transcellular” / special extracellular fluids: CSF, lymph etc. – <1L

6.  Water and electrolytes enter the body via the plasma:  absorption from the gut  IV administration  To enter most body cells, water and electrolytes must pass: Plasma -> Interstitium -> Cell cytoplasm  The water will always follow the solutes

7.  Capillary wall:  allows passage of water, electrolytes  prevents passage of plasma proteins (in health)

8.  Cell membrane:  Permeable to water  Selectively permeable to electrolytes

9. (mmol/L)PlasmaInterstitiumIntracellular Na + 135 - 145 12 K+K+ 3.5 – 5.3 150 Mg 2+ 0.75 - 1.05 40 Ca 2+ (total)2.2 – 2.5 1.0 – 2.0 Cl - 95 - 105 4 HCO3 - 22 - 25 12 Protein (g/dL) 6 - 8 -2.5

10.  Crystalloids  Colloids

11.  Electrolyte / small molecule solutions  0.9% NaCl (“normal” saline)  5% glucose  4% glucose, 0.18% saline (“dextrose” saline)  Compound sodium lactate (Hartmann’s)  Hypertonic saline  Glucose 10% / 20% / 50%  5% glucose, 0.45% saline

12. (mmol/L)Plasma0.9% NaCl0.18% NaCl 4% Glucose 5% GlucoseCSL (Hartmann’s) Na + 135 - 14515431-131 K+K+ 3.5 – 5.3---5 Mg 2+ 0.75 - 1.05---- Ca 2+ (total) 2.2 – 2.5---2 Cl - 95 - 10515431-111 Glucose3.5 - 6-222278- HCO3 - 22 - 25---- Lactate0.5 – 2.2---29

13.  Large chain protein / starch molecules in an electrolyte solution  Starches – Voluven, Hemohes, Volulyte,...withdrawn June 2013 by MHRA  Gelatins – Gelofusine / Geloplasma,...lack of good quality evidence  Blood products / Human Albumin Solution

14.  History:  Thirst  Abnormal losses: Sweating, Vomiting / diarrhoea, Haemorrhage, Sepsis / SIRS / post-operatively  Comorbidities, medications  Examination:  Pulse, blood pressure, capillary refill and jugular venous pressure (JVP) – current / trends  Pulmonary or peripheral oedema  Postural hypotension  Dry mucous membranes, loss of skin turgor

15.  Monitoring (current / trends):  National Early Warning Scoring (NEWS)  Fluid balance charts  Weight  Investigations:  Urea, creatinine and electrolytes (U&Es)  Full blood count (FBC)

16.  Resuscitation  Routine maintenance  Replacement & Redistribution  Reassessment

17.  Cardiac output is partially dependent on venous return: Frank – Starling law of the heart

18.  Is the patient hypovolaemic?:  systolic blood pressure is less than 100 mmHg  heart rate > 90 beats / min  capillary refill > 2 seconds or cold peripheries  respiratory rate > 20 breaths / min  National Early Warning Score (NEWS) ≥ 5  ABCDE approach, call for help  Identify cause and treat it  Fluid bolus (challenge) of 500ml 0.9% NaCL or CSL  Reassess and repeat as needed

19.  Fluid and electrolytes are lost daily in:  Faeces (100ml/day)  Urine (1500ml/day)  “Insensible” evaporative losses (500 – 1000ml/day)  Routine maintenance fluids alone are indicated only where there is:  No abnormal fluid loss  No abnormal redistribution

20.  To maintain homeostasis water and electrolytes must be replaced at a minimum rate of....  Water 25 – 30 ml/kg/day (2 - 2.5 L in a 70kg male)  Na + 1 (– 1.5) mmol/kg/day (70 – 100 mmol)  K + (0.7 –) 1 mmol/kg/day (50 – 70 mmol)  Cl - 1 (– 2) mmol/kg/day (100 – 140mmol)  50 – 100 g/day glucose....IN HEALTH!

21.  This equates roughly to:  either 1L 0.9% NaCl and 1 - 2L 5% glucose  or 2 – 3L of 0.18% NaCl in 4% Glucose...with 60 mmol kCl added to either of the above  Remember, this is the minimum requirements of an otherwise well 70kg man  In the majority of cases, fluid prescribing is also replacing fluid loss / redistribution

22.  Abnormal losses:  Gut:  Vomiting  Diarrhoea  Stomas/ fistulae/ drains  Sweating / pyrexia  Polyuria ( e.g. DI)  Hyperventilation  Haemorrhage

23.  Redistribution  Stress response:  Activation of renin-angiotensin-aldosterone system  -> Sodium and water retention  Increased secretion of cortisol and catecholamines  Reduced secretion of insulin  -> Hyperglycaemia  Increased capillary permeability leads to increased interstitial volume (SIRS / sepsis / post-operatively)

24.  Fluid prescribing should attempt to meet losses in both volume and electrolyte composition  Seek expert help if patients have complex fluid / electrolyte requirements:  gross oedema  severe sepsis  severe hyponatraemia or hypernatraemia  renal, liver and/or cardiac impairment  post-operative fluid retention and redistribution  malnutrition / refeeding

25.  All patients continuing to receive IV fluids need regular monitoring:  Fluid balance and U&Es daily  Weight measurement twice weekly  Patients receiving IV fluids for replacement or redistribution problems may need more frequent monitoring  Patients on longer-term IV fluid therapy whose condition is stable may be monitored less frequently  Always reassess!

26.  Urinary sodium measurement may be helpful in patients with high-volume GI losses  Urinary sodium < 30 mmol/l indicates total body sodium depletion  Urinary sodium may also indicate the cause of hyponatraemia, and guide a negative sodium balance in patients with oedema  If patients have received IV fluids containing high chloride concentrations, monitor serum chloride concentration daily to prevent hyperchloraemic acidosis

27.  Fluid management is not (very) complicated  Estimate fluid status based on history, examination and investigations  Is this maintenance?  What are you replacing??  Does the patient need resuscitation???  Always reassess!  Any patient receiving IV fluids should have their U&Es checked daily  Stop IV fluids as soon as possible

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