Fluid and Electrolytes

1. Fluid and Electrolytes

2. FLUIDS

3. Fluid homeostasis • Fluid homeostasis is dependent on • Basal Inputs Vs. Outputs • Our ability during pathologic processes to control • Fluid loss • Accounting for maintenance fluids • Replacing ongoing loss • Normal total body water • It is also important to define what we mean by fluid? • Water Vs. Volume • Blood

4. Basal Input Vs. Output INPUT Oral intake ~ 2.5L Metabolic input ~ 200mls OUTPUT Urine 0.52ml/kg/hour IL insensible loss

5. Assessing fluid balance • Assessing fluid balance is SIMPLE • Be calculated and use all the tools available to you • General inspection • Physical examination • Adjuncts to the physical exam – daily weighs, inputs vs. outputs • Biochemistry

6. Assessing fluid balance • General inspection • Does the patient look well? • Sunken eyes • Kussmaul breathing • Conscious state • IV lines/catheter/NIBP/ CVP…. • Physical examination • Vital signs • BP + Postural • HR • RR • SaO2 • JVP – Efficacy? • Peripheral oedema • Pulmonary oedema • Cap refill

7. Assessing fluid balance • Adjuncts • Daily weighs • Assumes weight change is due to water change • Inputs Vs. Outputs • Oral/Parenteral Vs. Urine/Faeces/Vomitus/Drain outputs • Biochemistry • BUN:Creat ratio • Indicative of pre-renal dysfunction • Sodium • Can be used to assess total body water deficit/surplus • Based on normal TBW • Males 0.6% TB weight • Females 0.5% TB weight • Contraction alkalosis • ?Lactate?

8. In summary • General inspection • Physical examination • Adjuncts to the exam • Biochemistry

9. So after making you assessment what do you do? • FIRST  Don’t meddle too much! Part of your assessment involves knowing when not to do anything • Is the process self-resolving/can it be treated by minimal input from yourself? • Is the patient DRY?  Give them appropriate fluid • Is the patient WET?  restrict input/remove fluid • Why are they dry/wet? How do we fix this process?

10. The DRY patient

11. The DRY patient • What has made them dry as compared to baseline? • Reduced intake • Fluid loss • Two fluid rules of general medicine (geriatrics) • When the elderly become sick, they don’t drink • When they drink, they drink copious amounts of tea

12. Causes of fluid loss in the surgical patient • Fasting with inadequate replacement • Bowel prep • Pre/intra/post operative bleeding • Inappropriate post-operative hydration • Drains • Organ specific • GI – vomiting/diarrhoea/sequestration/NG aspirates/stoma loss • Urology – Post-obstructive diuresis • Neuro – Cerebral salt-wasting syndrome • Over-diuresis

13. Managing the fluid deficit patient; Fluid resuscitation • Replace losses  bring the patient to euvolaemia • Based on weight • Fluid balance charts, estimated blood loss etc… • Biochemistry (will touch on this later) • Ensure adequate maintenance fluids ~ 2.5/3L/day • Replace ongoing losses • Look at drains • Urine output • ANY recordable ongoing output

14. Sometimes a fluid challenge is the best way to test if someone is DRY • Patients will not shatter, patients will not break • Be calculated and make a calculated decision

15. Fluid resuscitation in the shocked patient • Primary survey • Large bore IV canulas • 20ml/kg bolus • 500ml/1L bolus  take into account left ventricular function • Re-assess fluid status post resuscitation to assess further need for resusc.

16. Estimating blood loss • Total blood volume • 66ml/Kg for males, 60mL/Kg for females • Class 1 <15% • Minimal signs due to transcapillary refill • Class 2 15%-30% • Orthostatic changes in HR/BP, some drop in U/O. Systemic vasoconstriction in play • Class 3 30% - 40% • Hypotension, low U/O, tachycardia, loss of systemic vasoconstriction • Class 4 >40% • U/O<5ml/hr, profound shock • When do I give blood? Acute phase vs. Delayed phase loss • Triggers? HCT? ScvO2?

18. FIX THE CAUSE • Large drain outputs • Massive haemorrhage • Etc… • Fluid will not always save the day • Never delay definitive treatment if it is indicated.

19. How do I give this patient fluid? • Oral • IV • Central line

21. What type of fluid do I use? • Depends on what you are trying to achieve • Increasing total body water? • 5% dextrose of 4% Dex and 1/5th N/S • Increasing total body volume? • Crystalloids/Colloids • Replacing blood loss • Blood • Augmenting cardiac ouput? • In the acidotic patient?

24. Just to clarify • Crystalloids • N/S, hartmann’s, 4% and 1/5th • Based on osmalarity 2/3rd will redistribute into the extravascular space  so don’t get excited when your patient’s BP bumps up 5 mins after a fluid bolus! • Colloids • Gelofusine, albumin etc... • Theoretically to stay in the intravascular space…but for how long?

26. The WET patient

27. The WET patient • The WET patient • Too much input • Not enough output • OR the fluid is just in the wrong place • Distributive shock • Crystalloid resuscitation • Increased hydrostatic pressure with venous congestion • Decreased colloid oncotic pressure

28. Treating the wet patient • Do you need to? How much fluid O/L is tolerable? • Is this process unlikely to resolve? • Is the fluid load going to cause harm to the patient in the short term? • How to treat the wet patient • Fix the underlying cause • Fluid restriction • Diuresis • Physically removing the fluid  paracentesis

29. QUESTIONS?

30. ELECTROLYTES

31. So many electrolytes, so little time… • Hypernatraemia • Hyponatraemia • Hyperkalaemia • Hypokalaemia

32. Hypernatraemia • Can be due to Conn’s syndrome or excessive salt intake (sodium bicarbonate use etc…) • But… • Almost always water depletion • Treatment? • Calculate water deficit • cTBW x Current sodium = nTBW x normal sodium • nTBW = 0.6 x weight or 0.5 x weight • Replace water deficit • BD UEC’s to drop sodium by 0.5mmol/L/hour or ~10mmol sodium/day to prevent cerebral oedema

33. Hyponatraemia • Can occur in a • Hypovolaemic state • Euvolaemic state • Hypervolaemic state • Do a fluid assessment • Do the appropriate investigations

34. Evaluating hyponatraemia • Hypovolaemic • Urinary sodium • <20: Diarrhoea with Na loss and renal reabsorption • >20: Diuresis, Addison’s disease • Euvolaemic • Urinary osmolality (must compare to serum osmolality) • >100: SIADH • <100: Psychogenic polydipsia • Hypervolaemic • Urinary sodium • >20: Renal failure • <20: Heart failure

35. Correcting hyponatraemia • Fluid restriction<urine output • If Na change rapid, correct rapidly • Or correct rapidly within limits if patient symptomatic • If slow correct slowly • ?Sodium replacement? • Sodium deficit = nTBW x (130 – Current Plasma Na) • 3% sodium chloride contains 513 mEq of Na/L • Eg. 60kg woman with plasma Na 120 • Deficit = 0.5 x 60 x (130-120) = 300mEq • 300/513 = 585mL of hypertonic saline • Max rate correction of 0.5mmol/L/hr to prevent CPM

36. Hypokalaemia • Causes • Transcellular shift • Potassium depletion • Renal loss – diuretics, magnesium depletion (impaired K reabsorption) • Extrarenal loss – Diarrhoea • Treatment • 10% total body loss for each 1 mEq decrease • CHLORVESCENT • Slow K/IVT for longer term replacement (diuretics etc…) • Should we be scared of hypokalaemia? • It does not in itself produce serious ventricular cardiac arrhythmias but DOES increase arrhythmogenic potential of associated conditions (magnesium depletion, digitalis, myocardial ischaemia)

37. Biochemistry to diagnose hypokalaemia • Urine potassium • High >30mEq – renal loss • Cl >25mEq – diuretics, Mg depletion • Cl <15mEg – Ng drainage, alkalosis • Low <30mEq • Diarrhoea

38. Hyperkalaemia • Causes • Pseudohyperkalaemia – beware the 23g needle • Impaired excretion • Adrenal insufficiency, drugs (ACEi’s, spironolactone, NSAIDs) • Transcellular shift • Acidosis, rhabdo, drugs (B-blockers, digitalis) • Clinical manifestations • ECG changes ~ serum K of 6, definitely at 8

39. Hyperkalaemia - treatment • Treatment • Repeat bloods • ECG and monitoring • Membrane antagonism • Calcium gluconate Vs. Calcium chloride(x3) • Transcellularshift • Insulin/dextrose • B-agonists • Sodium Bicarbonate • Enhanced clearance • Resins • Diuretics • Haemodialysis

41. END