1. FLUIDS

2. Aims Understanding of human water and sodium homeostasis Develop fluid management skills

3. Learning Objectives / Plan Why this is important? Body fluid compartments Water and sodium homeostasis –Normally –In disease states Intravenous fluids Cases / scenarios

4. Intravenous Fluids 1830s –cholera epidemic Late 19th Century –surgical patients Now –Routine –……too routine?

5. Problems (first reported as early as 1911) Estimated 8315 excess deaths / year USA due to iatrogenic pulmonary oedema ?number with renal failure / underperfusion –easier to see and treat Too much given Wrong stuff Or Not enough given

6. Reasons Poor understanding of normal and perioperative Na and water physiology –<50% know Na content of NaCl 0.9% –Fluid balance charts infrequently checked Infrequently correct –Perioperative patients frequently (in only the first few days) 7000ml positive fluid balance 700mmol positive Na balance Poor understanding of the effect of –Age –Comorbidity –Medications

7. Case 1 55 year old female 50kg ASA I Elective Total Abdominal Hysterectomy Fasted from midnight Prescribe an IV fluid regimen for the next 24 hours

8. Case 2 80 year old male Dx Subacute Bowel Obstruction Booked for acute theatre list following a.m. Pulse rate 120 bpm; BP 90/60; Urine output 15ml/hr

9. Case 3 16 year old male Known IDDM –BM 55 –ketonuria 24hour Hx of vomiting, abdo pain, difficulty breathing A Maintaining airway B RR 30bpm, SpO 2 99% on air, chest clear on auscultation C Pulse rate 130, BP 100/60, oliguric now, polyuric previously D GCS 10

11. Definitions –Solute – a dissolved substance e.g. glucose –Solvent – a liquid which is able dissolve a solute to form a solution e.g. water –Semipermeable membrane – freely permeable to the solvent but not the solute –Diffusion - movement of solute down concentration gradient –Osmosis - movement of water from less concentrated solution to a more concentrated solution Osmotic pressure is proportional to the number of particles in solution Concentration of osmotically active particles in the solution = osmolarity (unit = milliosmoles)

13. Fluid Compartments Intracellular –Proteins Extracellular –Sodium Volume of ECF directly dependent upon total body Na Na virtually confined to ECF Water intake and losses regulated to hold concentration of sodium in ECF constant Blood –Plasma proteins

14. Sodium-Potassium Pump

15. Body Compartments

17. Water and Na Homeostasis in Health Water Water loss –increased ECF osmolarity –Stimulates hypothalamic thirst centre osmoreceptors ADH release Increased water reabsorption at renal tubules Na Baroreceptors and sympathetic system regulate Renin-Angiotensin System –Low BP, reduced ‘stretch’ renin angiotensin 2 aldosterone sodium reabsorption (Natriuretic hormones) –inhibit sodium pump –increased sodium excretion

18. Daily requirements Water30 - 40ml/kg Energy30 – 40kcal/kg Nitrogen0.2g/kg Sodium1-2mmol/kg Potassium1mmol/kg Chloride1.5mmol/kg Phosphate0.2-0.5mmol/kg Calcium0.1-0.2mmol/kg Magnesium0.1-0.2mmol/kg

19. Water Balance in Health Obligatory Losses Skin 500ml Lungs 400ml Gut 100ml Kidneys 500ml TOTAL 1500ml Sources Water as end- product of metabolism 400ml Minimum in diet 1100ml TOTAL 1500ml

20. Water and Na Homeostasis illness / injury / starvation Water Non-physiological ADH release Water retention Hyponatraemia Pain and sympathetic stimulation Inflammatory mediators Normal mechanisms overridden Na Renin release –Etc Sodium (and water) retention Fluid overload

21. Normal response Oliguria Hyponatraemia Prompts fluid admin, NaCl Overload Oedema ?oliguria is hypovolaemia or normal response Knee jerk reaction So…

23. Intravenous Fluids Crystalloids –NaCl –Dextrose –DexSal –Hartmann’s / Ringer’s Colloids –Gelofusin –Voluven –Volulyte Others –Blood –Albumin (HAS)

24. Crystalloid Water soluble crystalline substance capable of diffusion through a semi-permeable membrane Can equilibrate across membrane NaCl Dextrose 5% DexSal Hartmann’s / Ringer’s

25. Crystalloid –Can infuse rapidly in large volumes –Readily available –Cheap But –Equilibrate with large fluid compartments –Short duration in circulation –Risk of over-infusion, pulmonary oedema

26. 0.9% NaCl ‘Normal’ Saline 9g of NaCl per litre of water 154 mmol/l sodium 154 mmol/l chloride Osmolarity 308mosm/l pH 5 Distributes to ECFV : –25% intravascular; 75% interstitial –After 20 minutes only 50% in ECF –4.7L=> 1L increase in plasma volume

27. Would 0.9% NaCl get past ethics committees? Feel rotten –Abdominal pain –Nausea Non-physiological –Normal people can’t handle the load –Hyperchloraemic acidosis Normal anion gap metabolic acidosis –[Na + ] + [K + ]) – ([Cl - ] + [HCO 3- ] High Cl, low Bc –Cl inhibits Na excretion –Lowers GFR –Vasoconstriction

28. Hartmann’s or Ringer’s Compound Sodium Lactate (HCSL) Na+ 131 Cl- 111 K+ 5 Ca++ 2 Lactate 29 Osmolarity 279 pH 6.5 Similar distribution to 0.9% NaCl i.e. to ECFV –4.7L => 1L increase in PV Lactate ~ Bicarbonate thanks to liver

29. 5% Dextrose 50g dextrose per litre Glucose taken up by cells Equivalent to giving free water Fluid rapidly lost from intravascular compartment Distributes throughout total body water 2/3 intracellular; 1/3 extracellular –<10% intravascular 14L to increase PV by 1L –hyponatraemia Calorific value approx. 200 kcal

30. 4% Dextrose/ 0.18% NaCl (DexSaline) 40g dextrose = 160 kcal 30 mmol/l Na+; 30 mmol/l Cl- Similar distribution to 5% dextrose Free water –Haemodilution Hyponatraemia

31. Constituents of Crystalloids

32. Colloids a suspension of finely divided osmotically active particles in a continuous medium Gelofusin Voluven Volulyte Albumin Blood

33. Colloids Fluid stays in circulation –If capillary permeability normal –More effective in resuscitation theoretically (but not evidence based) All contain NaCl –risk of hyperchloraemic acidosis Volulyte is different –Watch this space Remember! –No oxygen carrying capacity

34. Gelatins Gelofusin, Haemaccel, Volplex Contain modified gelatin in NaCl Plasma half-life only 2-3 hours –Leaks Average MW 30-35 kDa –Metabolised Small risk of allergic reactions (1/13000)

35. Starches Voluven Hydroxyethylstarch (HES) in NaCl Variety of different brands –Wide range of MW and concentrations –Molecular substitutions Voluven –mean MW 130 kDa Intravascular t1/2 24 hours –90% eliminated in 40 days Adverse effects –Pruritis –Coagulopathy (max 50ml/kg/day) –Hyper-oncotic state acute kidney injury –Allergy 1/16000

36. Albumin HAS = Human Albumin Solution Pooled human plasma MW 69kDa Two strengths –5% iso-oncotic –20% hyper-oncotic Stays within intravascular space –Unless capillary permeability abnormal Intra-vascular t1/2 ~ 24 hours theoretically –Initial 70% increase in intravascular volume Effect only lasts 1-2hours –Natural turnover

37. Properties of Colloids

38. Volulyte Na 137 K 4 Ca 1.5 Cl 110 Acetate 34 Significantly lower chloride levels –Minimise hyperchloraemic acidosis HES (like Voluven) in a balanced electrolyte solution (like Hartmann’s)

39. Blood Colloid Ideal replacement for acute blood loss –Expands intravascular volume –Oxygen carriage Packed red cells ~ 300ml SAGM + citrate Numerous potential disadvantages –incompatibility reactions –TRALI –coagulopathy –hypocalcaemia –infection risk Other issues –Jehovah’s Witnesses –Autologous pre-donation –Expensive

40. Body Compartments

42. Clinical Fluid Management Options are: copy what went before or prescribe a logical regimen

43. Clinical Fluid Management Individualise Assess Replace deficit Maintenance Replace ongoing losses

44. Case 1 55 year old female 50kg ASA I Elective Total Abdominal Hysterectomy Fasted from midnight Prescribe an IV fluid regimen for the next 24 hours

45. How about? Saline 0.9% 1000mL Dextrose 5% 1000mL Over a day, each bag 8hrly

46. This gives 153 mmol Na 3000 ml Water 0 mmol K

47. Requirements Water 40ml/kg/day2000ml Na 1.5 mmol/kg/day75mmol K 1 mmol/kg/day50mmol

48. Better choice DexSaline + 20mmol K 1000ml Gives; –60mmol Na, 40mmol K, 2000ml Water

49. Or Hartmanns CSL 500ml Dextrose 5% 500ml + 10mmol K Dextrose 5% 1000ml + 20mmol K Gives; –65mmol Na, 32.5mmol K, 2000ml Water –Less Cl too

50. 80 year old male, 70kg Constipation, vomiting, abdo pain Dx Subacute Bowel Obstruction Booked for acute theatre list following a.m. Pulse 120 bpm; BP 90/60; Urine output 15ml/hr Case 2

51. Clinical Fluid Management Individualise Assess Replace deficit Maintenance Replace ongoing losses

52. Assessment of Fluid Status History –How long starved? –How much lost? Ongoing losses Examination –Dry mucous membranes –Loss of skin turgor –Oliguria –Hypotension –Tachycardia –Decreased JVP / CVP

53. Assessment of Fluid Deficit Mild –Loss of 4% body weight –Loss of skin turgor –Dry mucus membranes Moderate –5-8% body weight –Oliguria –Tachycardia –Hypotension Severe –>8% body weight –Profound oliguria –CVS collapse

54. The Fluid Challenge Large bore intravenous cannula –Preferably in a proximal site – antecubital fossa Preferably colloid (preferably a starch) –250-500ml stat bolus Observe for clinical response –BP –UO –JVP / CVP

55. Plan Replace Deficit –Colloid boluses according to clinical response Maintenance –70kg and old: 100mmol Na, 60mmol K, 2500ml Water Replace Ongoing Losses –Replace like-with-like according to nasogastric aspirate –?what to use

56. Constituents of GI Fluids

57. Abnormal Fluid Losses Common in surgical patient Gut –NG suction / Vomiting Bowel obstruction –Bowel prep Skin/Lungs –Increased losses with hyperventilation –Fever losses increase by 12% per oC rise –Burns Loss proportional to %age burn Urine –hyperglycaemia –diuretics

58. Imbalances: Fluid Depletion Decreased intake –Elderly –Dysphagia –Unconsciousness –Fasting /Nil by mouth The Third Space

59. Case 3 16 year old male Known IDDM –BM 55 –ketonuria 24hour Hx of vomiting, abdo pain, difficulty breathing A Maintaining airway B RR 30bpm, SpO 2 99% on air, chest clear on auscultation C Pulse rate 130, BP 100/60, oliguric now, polyuric previously D GCS 10

60. Clinical Fluid Management Individualise Assess Replace deficit Maintenance Replace ongoing losses

61. DKA 3 to 5L fluid deficiency 300 to 500 mmol sodium deficiency 150 to 250 mmol potassium deficiency Hyperglycaemia Hyperketonaemia –Metabolic acidosis

62. DKA Replace deficit and ongoing losses Fluids: first 2 to 3 L => 0.9%NaCl –Colloid if hypotensive Fluid challenges ?CVL Potassium supplementation Insulin sliding scale –4 to 8 hours to correct hyperglycaemia –10-20 hours to correct ketoacidosis –When blood glucose < 12mmol/L change to glucose ivi Close attention to Na, K, ABG –Insulin lowers K

64. Problems Too much given Wrong stuff Or Not enough given

66. Too much Fluid overload Pulmonary oedema Anastomotic breakdown

67. Wrong Stuff Too much Na Too much Cl Inappropriate 5% Dex Hartmann’s Volulyte

68. Not enough Easier to see –Reduced urine output –Poor perfusion Easy to treat –Fluid challenges –Flow guided therapy Better prognosis in critically ill

69. Solution Know physiology Know requirements Replace losses Give enough… but not too much

70. Questions? Further reading; GIFTASUP: British Consensus Guidelines on intravenous fluid therapy for adult surgical patients (2008)