Rob Fleming Specialty Doctor – Anaesthetics 22/07/2014

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

 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

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

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

 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

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

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

(mmol/L)PlasmaInterstitiumIntracellular Na K+K+ 3.5 – Mg Ca 2+ (total)2.2 – – 2.0 Cl HCO Protein (g/dL)

 Crystalloids  Colloids

 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

(mmol/L)Plasma0.9% NaCl0.18% NaCl 4% Glucose 5% GlucoseCSL (Hartmann’s) Na K+K+ 3.5 – Mg Ca 2+ (total) 2.2 – Cl Glucose HCO Lactate0.5 –

 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withdrawn June 2013 by MHRA  Gelatins – Gelofusine / Geloplasma,...lack of good quality evidence  Blood products / Human Albumin Solution

 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

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

 Resuscitation  Routine maintenance  Replacement & Redistribution  Reassessment

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

 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

 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

 To maintain homeostasis water and electrolytes must be replaced at a minimum rate of....  Water 25 – 30 ml/kg/day ( 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!

 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

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

 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)

 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

 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!

 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

 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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