Peri-operative M anagement of Fluid , Electrolytes and Kidney Function

1. Peri-operative Management of Fluid, Electrolytes and Kidney Function Surgical Student Talk Brad Bidwell

2. If you take away one point from today it should be this: There is no magic formula for fluid management, it depends on the patient and the situation, if in doubt then asks someone more senior

3. Where is it all going?

4. Assessing Fluid Balance • Urine output • Peripheral circulation • JVP • Postural blood pressure • Lung sounds • Oedema • Thirst • Heart rate, blood pressure, mucous membranes, tissue turgor, weight

5. Assessing Kidney function • Urine output • UECs • Especially creatinine and urea

6. Categories of Fluids • Maintenance fluids • Daily requirements • Ongoing losses • “Surgical” losses: bleeding, serous ooze, drain tube losses – these tend to be sodium rich • Gastrointestinal losses: vomiting, diarrhoea, nasogastric losses – these tend to be potassium rich • Resuscitation fluids (replacement of losses)

7. What is needed each day? • Water • 4:2:1 rule: (4ml/kg/hr for the first 10kg body weight PLUS 2ml/kg/hr for 11-20kg of body weight PLUS 1ml/kg/hr for every kg of body weight after that) • For a 70kg pt: (40 + 20 + 50 = 110mL/hr = 2640 mL/day) • Monitor by maintaining urine output in the range of 0.5 - 1.0mL/kg/hr (i.e. 35 – 70 mL/hr) • Sodium • 1 – 2 mmol/kg/day (i.e. 70 – 140 mmol/day) • Potassium • 0.5 – 1 mmol/kg/day (i.e. 35 – 70 mmol/day)

8. Types of Fluids • Crystalloid • Electrolytes dissolved in water • E.g. normal saline, CSL/Hartmann’s, 5% dextrose, 4% dextrose + 1/5th normal saline (“4 and 1/5th) • Colloid • Large molecules dissolved in water • E.g. gelofusine, albumin • Blood products • E.g. PRBCs, FFP, platelets

9. Crystalloids • You can add other electrolytes to these bags!

10. Rate of fluids • Fluids come in 1 L bags • You write it up as how fast you want to give that bag • Write up 24 hours worth of fluids, and make sure they’re not finishing overnight

11. The Real World • Check the history: • CCF? Renal failure? Haemorrhage? • What restriction are they on? • How much fluid have they had already? • Fluid assess the patient: • Does the patient look well? • Are they thirsty? • Check the obs, especially BP and urine output. • Listen to the lungs, check for sacral oedema. • Check the tests: • Are their electrolytes in normal range and is their kidney function good • CXR?

12. The Autopilot Method • What people usually do: • N.saline 8/24 • N.saline 8/24 • N.saline 8/24 • The electrolyte load from this is: • 3L of water per day • 450 mmol Na+ per day • 0 mmol K+ per day • The 70kg patient needs: • 2.6L of water per day • 70 - 140mmol Na+ per day • 35 - 70mmol Na+ per day

13. The Autopilot Method • Try this: • 4% + 1/5th, with 30mmol K+ added 8/24 • 4% + 1/5th, with 30mmol K+ added 8/24 • 4% + 1/5th 8/24 • This gives: • 3L water per day • 90mmol Na+ per day • 60mmol K+ per day

14. Case study 1 • HOPC: 28 F presents to ED with 3/7 of poorly localised central abdominal pain, increasing in intensity and shifting to the RIF over the last 12/24. Nil fevers, nil changes to bowels/urine, nausea but no vomiting. Virgin abdomen. No significant PMHx. • O/E: Obs stable, afebrile abdomen soft with focal tenderness in RIF and voluntary guarding. Pain worse when the right hip is flexed. • Ix: FBE – mildly elevated WCC, UECs – NAD, LFTs/lipase NAD, CRP 50, B-HCG negative • Dx: clinically acute appendicitis • Mx: Fasting, for theatre – lap. Appendicectomy • The registrar tells you to write up some fluids. What do you give?

15. Case study 2 • Hx: 78 M 3/7 cramping abdominal pain with nausea and vomiting. Hasn’t opened bowels in 2/7. No fevers, no urinary changes. PMHx – some operation on abdomen 40 years ago, mild “heart troubles”, AF – on warfarin, high cholesterol. • O/E: Obs: HR 105, BP 110/70, abdomen soft, generalised tenderness, midline laparotomy scar visible superior to umbilicus • Ix: FBE – NAD, UECs – Na 138 K 3.5 • Dx: likely SBO • Mx: CT A/P, trial conservative management – nasogastric and IV fluids • The registrar tells you to write up some fluids. What do you give?

16. Case study 3 • Hx: 52 M presents to ED with a poor thrill in his AV fistula. PMHx – ESRF due to poorly controlled T2DM, currently on haemodialysis 3x weekly, 1L fluid restriction per day, 2 prior AMI’s – stents, on warfarin, PVD – right BKA, HTN … • O/E: Obs – stable (BP 165/130), afebrile. No thrill over AVF site, no bruit heard. • Ix: FBE – NAD, UECs – Cr 450, Ur 20.3, K+ 6.2 • Dx: blocked fistula • Mx: unblock fistula • The registrar tells you to write up some fluids. What do you give?

17. Calcium, Magnesium, Phosphate • Usually we don’t worry about these too much, especially in patients fasting for a short amount of time • Treat to target – usually we don’t prescribe regular CMP supplements, we replace in response to the test

18. Supplementation

19. Resuscitation • Ascertain where the losses are from: • Blood? • Dehydration? • Vomiting or diarrhoea? • Replace like with like (i.e. if they’ve lost blood, give them blood).

20. Haemorrhagic Shock

21. Replacing Massive Blood Loss • Control the bleeding • 1L of normal saline STAT, followed by a second bag if necessary. • If patient is still unstable, blood products are necessary at this point • Group and screen, crossmatch • RMH has a “massive exsanguination pack” – O negative blood products ready to go in a cooler.

22. Traps • Beware third spacing conditions – ascites, pleural effusion, pancreatitis, burns • Pay close attention to old, frail patients • Monitor patients closely when giving large amounts of N.saline • Ignoring CMP’s in patients who are fasting for a longer period – treat to target

23. References • Fluid Management Student BMJ 2010;18:c5063 http://student.bmj.com/student/view-article.html?id=sbmj.c5063 • “Maintenance” IV fluids in euvolaemicadults, Michael Tam http://vitualis.wordpress.com/2006/05/01/maintenance-iv-fluids-in-euvolaemic-adults/ • OHCM • Toronto Notes