INTRAVENOUS FLUID THERAPY Tom Heaps Consultant Acute Physician
LEARNING OBJECTIVES 1. Crystalloids vs colloids 2. Balanced vs non-balanced solutions 3. Composition of various IV fluids 4. What is normal about Normal Saline? 5. Goals of fluid therapy 6. Recognizing and managing hypovolaemia 7. Daily electrolyte and fluid requirements 8. Maintenance, Replacement and Redistribution 9. Summary: The 5 Rs and NICE CG174
WHAT IS THE PROBLEM WITH FLUID THERAPY? Cautious IV Fluids....Because the patient has angina?!
THE POPCORN MODEL OF FLUID THERAPY Daily fluid requirement = +
QUESTIONS TO ASK BEFORE PRESCRIBING FLUID 1. Does my patient need IV fluid? 2. For what purpose? 3. What type of fluid? 4. What amount (volume) of fluid? 5. What rate (how fast)? > POLL ENGAGE BRAIN!
DAILY ELECTROLYTE REQUIREMENTS 1. Sodium 1-2mmol/kg/d (70-140mmol/d) Serum concentration 140mmol/L 2. Potassium 0.5-1mmol/kg/d (35-70mmol/d) Serum concentration 4mmol/L 1mmol/kg/d of each 3. Chloride 1mmol/kg/d (70mmol/d) Serum concentration 100mmol/L
WHAT S IN YOUR CUPBOARD? 1. Crystalloids (hopefully) Isotonic ( normal ) 0.9% saline +/- 20-40mmol KCl Hartmann s solution 5% and 10% glucose 4% glucose/0.18% saline ( dex-saline ) +/- 20-40mmol KCl Plasmalyte 148 (if you are lucky) 2. Colloids (possibly) Albumins Gelatins e.g. Gelofusine, Volplex Starches > POLL
WHAT S NORMAL ABOUT NORMAL SALINE? Tonicity ( isotonic.almost) osmolality 308mOsmol/L (plasma 275-295mOsmol/L)..and not a lot else! Sodium 154mmol/L (140mmol/L) Chloride 154mmol/L (100mmol/L) ph 5.5 (7.4) Potassium 0mmol/L (4mmol/L) > POLL
COMPOSITION OF DIFFERENT CRYSTALLOIDS Content (mmol/l) Plasma 0.9% Saline Hartmann s Plasmalyte 148 5% Glucose 0.18% Saline-4% Glcuose Sodium 140 154 131 140 0 31 Potassium 4 0 5 5 0 0 Chloride 100 154 111 98 0 31 Lactate etc. <2 0 29 0 (gluconate 23, acetate 27) 0 Calcium 2.4 0 2 0 (Mg 1.5) 0 0 Glucose 4.5 0 0 0 278 (50g) 222 (40g) ph 7.4 5.5 6.0 6.0 4.5 4.5 Osmolality 285 308 278 295 278 284
WHAT HAPPENS IF YOU GIVE NORMAL SALINE? ph depends on difference between strong +ve ions (e.g. Na + ) and strong ve ions (e.g. (Cl - ) = strong ion difference (Stewart s Theory) Physiological strong ion difference 40mmol/L (140 100) 0.9% Saline contains 154mmol/L Na + and 154mmol/L Cl - Chloride rises disproportionately to sodium reducing the strong ion gap and resulting in (hyperchloraemic) acidosis Renal vasoconstriction and impaired secretion of sodium Clinicians often respond to acidosis by giving more fluids Don t forget, 0.9% saline is also present in colloids e.g. HAS, Gelofusine, Volplex, Voluven Balanced colloids now available e.g. Gelaspan, Isoplex, Volulyte
MYTHS ABOUT BALANCED CRYSTALLOIDS but it s got potassium in it Hyperchloraemia causes acidosis which exacerbates hyperkalaemia Normal saline may raise [K + ] more than balanced solutions in AKI but it s got lactate in it O Malley et al, Anesthesia and Analgesia, 2005 Lactate per se is not bad for you: it is a marker of disease severity Lactate in Hartmann s lactic acid; it is a conjugate base (potential HCO 3- ) and will NEVER increase acidosis The patient will be making a lot more lactate (1500mmol/d in health) than you will be giving therefore effect on total body lactate negligible
THE GREAT FLUID DEBATE CONTINUES Balanced vs non-balanced crystalloids 0.9% Saline slightly cheaper than Hartmann s ( 0.78/L vs 1.00/L) but is associated with hyperchloraemic acidosis: Potential for renal vasoconstriction (AKI and hyperkalaemia), impaired GI perfusion and coagulopathy Relevance in terms of clinical outcomes uncertain (large trials on-going) Crystalloids vs colloids Equivalent patient outcomes in most studies Colloids associated with greater expense, risk of anaphylaxis, coagulopathy and increased risk of AKI (especially starches - withdrawn) Albumin probably reasonable choice in sepsis?
FLUID THERAPY: BACK TO BASICS Restore circulating volume Diagnosis and treatment of hypovolaemia Correct dehydration Reduced total body water with preservation of circulating volume Maintain circulating volume and electrolytes Understand and anticipate physiological requirements
RECOGNIZING & TREATING HYPOVOLAEMIA 1. Vital signs and MEWS 2. Diagnostic tests 3. CVP and oliguria 4. The fluid challenge Treating Hypotension Hypovolaemia Record patient Tachycardia observations Central Urine Venous output (Oliguria) Pressure Choose Tachypnoea your weapon! Does Cannot not describe Delayed diagnose euvolaemia capillary hypovolaemia Give 500mL QUICKLY ( 15mins) refill Is Oliguria no longer should recommended Passive leg Cool raise peripheries trigger a volume as a Stay assessment, resuscitation by the patient NOT a test target and repeat fluid challenge observations Autotransfusion Other Oliguria (less of invasive) may 500mL indicate means of blood dehydration of from guiding Repeat legs boluses and fluid abdomen resuscitation until patient no longer hypovolaemic Urine output is not a good target in the Effect Helpful maximal acutely at extremes at unwell 30-90s of patient filling only If no haemodynamic response after 2L 10% increase of fluid (i.e. in sbp ve and/or test) contact reduction Critical in Care HR predictive of fluid responsiveness > POLL
GETTING IT WRONG Dry Over-transfusion: fluid in the wrong place Wet Pulmonary oedema, gut oedema, peripheral oedema, anasarca Capillary injury and shedding of EGL Dry Wet Under-transfusion: hypoperfusion and persisting shock AKI Ischaemic hepatitis / colitis Arrhythmias / ACS Cerebrovascular events Multi-organ failure
WET, DRY OR SOMEWHERE IN-BETWEEN? Dry (Restricted) Wet (Liberal)
GETTING IT RIGHT FOR MEDICAL PATIENTS Dry (Restricted) Dry Wet (Liberal) Wet Frequent Reassessment is Key!
MAINTENANCE FLUIDS Wet 25-30mL/kg/day 1mmol/kg/day of Na +, Cl - and K + 25mL/kg/day of: Dry Hartmann s 4% 0.9% Glucose-0.18% NaCl Saline + 40KCl > 3.3mmol/kg/day 0.45mmol/kg/day > 4mmol/kg/day Na Na Na + + > 2.8mmol/kg/day 0.45mmol/kg/day > 4mmol/kg/day Cl Cl Cl - - - > 0.125mmol/kg/day 1mmol/kg/day K+ K+ > 70g glucose
REPLACEMENT One of the few indications for normal saline
SUMMARY: 5 Rs
DISCUSSION QUESTIONS COMMENTS