Fluid Therapy for Veterinary Anaesthesia (October 2024) PDF
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Uploaded by SimplerBouzouki
University of Surrey
2024
Hanna Machin
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This document is a presentation on fluid therapy for veterinary anesthesia. Presented on October 4, 2024. Topics include fluid balance, fluid types and calculations, and potential complications. Aimed at professional veterinary practitioners.
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FLUID THERAPY Hanna Machin Dip ACVAA, Dip SIAV, MVetMed, MRCVS Lecturer in Veterinary Anaesthesia 4th October 2024 LEARNING OBJECTIVES Be able to: Describe the normal distribution of fluid within the body Define hypovolaemia and dehydration Describe the different...
FLUID THERAPY Hanna Machin Dip ACVAA, Dip SIAV, MVetMed, MRCVS Lecturer in Veterinary Anaesthesia 4th October 2024 LEARNING OBJECTIVES Be able to: Describe the normal distribution of fluid within the body Define hypovolaemia and dehydration Describe the different types of intravenous fluids available and their relative indications Describe normal fluid requirements and suggest a treatment plan for maintenance Suggest a treatment plan for a hypovolaemic and/or dehydrated patient Identify the patient at risk of iatrogenic fluid overload TOTA L B O D Y WAT E R ADULTS Dry matter NEONATES (% of Body weight) 20% 40% Total Body Water (% of Body 80% 60% weight) F LU I D C O M PA RT M E N TS ADULTS (% of Body Mass) 40% Dry Matter Total 40% Intracellular (2/3 of TBW) Body Water Interstitial fluid (3/4) (TBW) 20% Extracellular (1/3 of TBW) Intravascular (1/4) TOTA L B LO O D V O L U M E Dog/Horse : 8-9% body mass (i.e. 80-90 mL/kg) Cat/Cattle/Sheep: 6-7% body mass (i.e. 60-70 mL/kg) T H E B O D Y ’ S F L U I D C O M PA R T M E N T S Semi-permeable Capillary walls Cell membranes Fluids move between compartments depending on: Tonicity of fluid Tonicity of extracellular compartment (Na+) Size macromolecules in the fluid Movement across endothelial membranes: Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff Condition of capillary membrane E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 Hydrostatic pressure, colloid osmotic pressure & vascular permeability Water & electrolytes (ECF loss): Vomiting, diarrhoea, diuresis Blood TYPES of FLUID LOSS Protein rich ECF loss: Pure water Transudate, exudate, effusion, High RR (hyperthermia, severe enteritis, protein losing pneumonia), water deprivation, enteropathy/nephropathy excessive water loss FLUID BALANCE SENSIBLE LOSSES Urine output GAINS INSENSIBLE LOSSES Faeces Water intake (food & Respiration water) Saliva Metabolic water Cutaneous (i.e., Sweating) production (10%) Respiratory tract MAINTENANCE REQUIREMENTS Losses Gains To maintain balance Sensible Losses + Insensible Losses must = 25 mL/kg/day + 25 mL/kg/day = Losses = ~ 50 mL/kg/day GOAL DIRECTED FLUID THERAPY Restore homeostasis: euvolemia & hydration Correction of acid base & electrolytes imbalances Where are/is the deficit(s)? Which fluid type is the best to replace the deficit(s)? Calculate fluid dose & rate Monitor patient’s response & potential complications Reassessment of therapy Image from: BSAVA Manual of Canine and Feline Anaesthesia and Analgesia Chris Seymour, Tanya Duke-Novakovski (eds), Blackwell Publishers, 2016 Adapt plan to patient’s needs Goal: zero balance FLUIDS ARE DRUGS… Are IV fluids indicated? Correct drug Correct dose/volume Administration (rate/bolus) Patient considerations (Hypotension? Causes? Contraindications?) Monitoring Side effects H Y P O V O L E M I A v s D E H Y D R AT I O N Hypovolaemia: Decrease fluid volume within the VASCULAR space → ↓ ssue perfusion Loss of blood and/or fluid & electrolytes If persist can affect other compartments Rapid replacement therapy Dehydration: Decrease fluid volume within the interstitial compartment It can affect all other compartments causing also hypovolaemia Images from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Water & electrolytes imbalance (especially Na+) Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Slower, sustained replacement Assoc. 2024 A S S ES S I N G I N TR AVA S C U L A R S PAC E D E F I C I TS (HYPOVOLAEMIA) History: (V+, D+, anorexia, fever, haemorrhage, oedema, ascites …) Physical examination: Altered mentation including depression, inactivity & recumbency Tachycardia/ arrhythmias Change CRT & paler MM (vasoconstriction) Weak peripheral pulses (vasoconstriction), low BP Cold extremities Tachypnoea Laboratory tests: ↓ PCV, ↓TS, ↑ lactate, metabolic acidosis, anaemia, electrolytes abnormalities, ↓ urine output, ↑ urine specific gravity PHASES OF HYPOVOLEMIC SHOCK Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 A S S E S S I N G D E H Y D R AT I O N Images from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 A S S E S S I N G I N T R A C E L L U L A R S PA C E Sodium concentration Free water deficit Na-K-ATPase pumps Na+ is a membrane-impermeant solute Water moves freely Dehydration: hypernatremia and hypertonicity Image from: https://testbook.com/chemistry/electrolytes Free Water Deficit (L)= [ (Patient Na/ Desired Na) – 1] X 0.6 X Weight (kg) TYPES OF FLUIDS AVAILABLE Crystalloids Colloids Oxygen- carrying solution (covered in another lecture) Blood products (covered in another lecture) C R Y S TA L L O I D S Solutions prepared by dissolving crystalline compounds (electrolytes +/- sugar) in water, usually contain buffers (acetate, lactate, gluconate) to maintain body acid base status Classification: tonicity in comparison to plasma (290–310 mOsm/L) Isotonic: ~ osmolality Hypotonic: ↓ osmolality Hypertonic: ↑osmolality Image from: https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook- 2.0/section/2.12/primary/lesson/osmosis-bio/ I S OTO N I C C R Y S TA L LO I D S ~ composition to ECF → stay into ECF → REPLACEMENT/RESUSCITATION Redistribution from Intravascular Space to Interstitial space within 30-60’ Only 25% (1/4) remains in intravascular space Image from: Yunos, N.M., Bellomo, R., Story, D. et al. Bench-to-bedside review: Chloride in critical illness. Crit Care 14, 226 (2010). https://doi.org/10.1186/cc9052 SALINE SOLUTION (0.9% NaCl ) Not balanced Acidifying solution → Hamburger shift Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 Care with heart or renal disease (Na+ +++) AKI risk in human (+++ Cl-) Uses: Hyponatremia Hypercalcemia Hypochloremic metabolic alkalosis (pyloric obstruction: V+++→loss of HCl) HARTMANN'S SOLUTION Balanced solution Most used for Replacement/resuscitation & peri-operative fluid therapy Alkalinising solution (contain bicarbonate precursors: lactate) Liver: Lactate converted into glucose: 2 H+ consumed (less H+ in blood) “ HCO3- sparing effect” Oxidative metabolism: HCO3- production Careful with blood transfusion:clots (Ca2+) with urethral obstruction, hyperkalaemia.; (NaCl 0.9% makes acidosis worst) H Y P E R TO N I C C R Y S TA L LO I D S Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 RESUSCITATION (hypovolemia) Rapid intravascular volume expansion (3X volume infused), transient effect (1-3h): → Draws water from ICS, ISS, RBC (osmotic gradient) into IVS → dehydration: Administer WITH isotonic crystalloids to address TBW deficits + to prolong duration of action Inotropic effect, increase CO Vasodilation due to hypertonicity ( coronary & cerebral perfusion)→ do not administer fast! Dose: 4-5 ml/Kg (NO administer faster than 1ml/kg/min) H Y P OTO N I C C R Y S TA L L O I D S MAINTENANCE fluids (often now substitute with isotonic crystalloids) pure water loss treatment Often Dextrose added to ↑ tonicity to avoid damage to RBC Water in excess to electrolytes (↓ Na+ content, ↑ K+ like inside cells) Water from extracellular space to intracellular space Hypernatremia treatment No boluses! Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 COLLOIDS Macro-molecules suspended in a crystalloid solution (protein, sugars, starches) Colloid osmotic pressure: drawn fluid from ISP, ICS → volume expansion (> than volume infused) Longer lasting in intravascular space compared to crystalloids (hours) Hypoproteinaemia Natural: blood products (plasma, whole blood, albumin) Synthetic: Dextrans & hydroxyethyl starches (HESs): hetastarch, tetrastarch & pentastarch → Controversial use: Adverse effects: Coagulation impairment, Acute Kidney Injury, Death… FLUIDS CAN BE HELPFUL FOR… RESUSCITATION (i.e. Hypertonic Saline, Hartmann’s solution, Blood products..): to correct intravascular volume deficit (hypovolemia) REPLACEMENT (i.e., Hartmann’s solution): to replace lost body fluids & electrolytes that cannot be compensated by oral intake ~ to ECF: [Na+ & Cl- ]~ to ECF Often used also for short term maintenance (supplemented with K+ & dextrose) MAINTENANCE (i.e. Hypotonic crystalloids): to cover daily basal requirements of water, electrolytes, glucose ↓ Na+, > K+ than replacement fluids Suitable for long term therapy SUBSTITUTE LIKE with LIKE T R E AT M E N T P L A N F O R H Y P O V O L E M I A ( R E S U S C I TAT I O N ) Rapid correction intravascular deficits & address underlying causes Always IV/IO Buffered Isotonic crystalloids: boluses over 15-30’ Only 25% (1/4) remains in intravascular space after 30-60’ Dog: 15-20 mL/kg Cat: 5-10 mL/kg Monitor closely Assess clinical response & repeat if necessary +/- Hypertonic crystalloids: If haemorrhage: consider blood products Dog: 4-6mL/kg Cat: 1-4 mL/kg +/- Colloids: Remain in intravascular space for hours 2.5-5 mL/kg Max amount: 20mL/kg dog; 10-15mL/kg cats T R E AT M E N T P L A N F O R D E H Y D R AT I O N Balanced isotonic crystalloids IV, IO If not severe: PO (voluntary oral intake, orogastric tube), SC ( poor absorption, poor peripheral perfusion, small amount can be given at time) Calculate Total fluid deficit (L)= Body weight (kg) X % dehydration (as a decimal) Administer over 12-24h Maintenance fluid requirements & ongoing losses should be added to the volume calculated for dehydration Continuous monitoring If end points returned back to normal: → Con nue with oral administration (if possible) → If not: maintenance fluid plan Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 T R E AT M E N T P L A N I F H Y P O V O L A E M I A & D E H Y D R AT I O N A R E B OT H P R E S E N T Address hypovolemia 1st THEN rehydration (account for ongoing losses) + maintenance rate T R E AT M E N T P L A N F O R M A I N T E N A N C E Hypotonic crystalloids (or balance isotonic crystalloids + K & dextrose short term) Daily fluid requirements in hydrated & euvolemic patients that are unable to maintain fluid homeostasis through oral ingestion Dog: 60 mL/kg/day → ~ 2mL/kg/hr Cat: 40 mL/kg/day Paediatric patients: Dog: 3 X adult dose → ~ 5mL/kg/hr Cat: 2.5 X adult dose Over 24h FLUID APPROACH IN ANAESTHESIA RESTRICTED APPROACH PREVIOUS APPROACH: Administration large volume of crystalloids Fluid administration according to (10 ml/kg/hr) as: patients needs Peri-operative fasting 3ml/kg/hr (cats) Insensible losses: 5ml/kg/hr (dogs) - Evaporation If normal cardiac & renal function - Dry anaesthetic gases 3rd space losses?? Recommended: to counteract ↓ Cardiac output & vasodilation caused by inhalational agents & other drugs To maintain IV canula patency GOALS OF FLUID THERAPY DURING ANAESTHESIA O2 delivery & tissue perfusion Macro circulation Micro circulation Maintain/ correct electrolyte composition & acid balance Stabilise before anaesthesia Monitoring Maintain adequate blood pressure INFUSION EQUIPMENT Intravenous canula Intraosseous catheters Fluids of choice Giving set +/- Fluid pump/ syringe driver +/- Pressure bag GIVING SETS FOR FREE FLOW FLUID A D M I N I S T R AT I O N 20 drops/ml 60 drops/ml (adult set) Gate-clamps or squeeze-clamps Micro dripper (paediatric set) Spike Roller clamps Injection port Gravity assisted Risk of fluid overload Risk of air embolism Sometimes inaccurate (change of patient’s position, blood clots) field anaesthesia, MRI F L U I D R AT E C A L C U L AT I O N S U S I N G A G I V I N G SET From mL/kg/hr drops/second Giving set type (drops/mL) Patient body mass (kg) Info needed Desired administration rate (mL/kg/hr) mL/kg/hr x body mass (kg) → mL/hr Image from: mL/hr ÷ 60 → mL/min https://picryl.com/media/questions- demand-doubts-emotions-2ea8c6 mL/min ÷ 60 → mL/sec mL/sec x drops/mL (giving set) → drops/sec (1 ÷ drops/sec → # seconds per drop) INFUSION PUMPS & SYRINGE DRIVERS RATE of infusion: ml/hr VTBI (Volume To Be Infused): Total ml of fluid you would like the pump to deliver VI (Volume Infused): amount of fluid already infused. Should be zeroed before starting. Improve accuracy & consistency Boluses administration Audible alarms (i.e., air bubbles) FLUID THERAPY MONITORING Start treatment and monitor for changes in… Clinical signs: Heart Rate Arterial Pressure Pulse rate & quality Laboratory findings: Capillary Refill Time & MM colour Urine specific gravity Core-peripheral temperature gradient Haematocrit Respiratory rate & effort Total protein Mentation Lactate Urine Output Electrolytes Skin turgor Body weight Signs of oedema Values should trend towards normal… F L U I D T H E R A P Y C O M P L I C AT I O N S Common adverse effects: Fluid overload/ intolerance (heart or kidney disease) →Interstitial oedema & tri-cavitary effusion Electrolytes & acid-base imbalances Dilution coagulopathy (from excessive administration of crystalloids) Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 FLUID OVERLOAD THERAPY Image from: Pardo M, Spencer E, Odunayo A, Anim Hosp Assoc. 2024 Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 REFERENCES REFERENCES REFERENCES Asim M, Alkadi MM, Asim H, Ghaffar A. Dehydration and volume depletion: How to handle the misconceptions. World J Nephrol. 2019 Jan 21;8(1):23-32. doi: 10.5527/wjn.v8.i1.23. PMID: 30705869; PMCID: PMC6354080 Malbrain, Manu & Mekeirele, Michaël & Raes, Matthias & Hendrickx, Steven & Ghijselings, Idris & Malbrain, Luca & Wong, Adrian. (2023). The 4-indications of Fluid Therapy: Resuscitation, Replacement, Maintenance and Nutrition Fluids, and Beyond. 10.1007/978-3- 031-42205-8_8 Langston C., Gordon D. Effects of IV Fluids in Dogs and Cats With Kidney Failure, Frontiers in Veterinary Science, Vol 8 (2021) URL=https://www.frontiersin.org/journals/veterinary science/articles/10.3389/fvets.2021.659960DOI=10.3389/fvets.2021.659960 T H A N K Y O U F O R Y O U R AT T E N T I O N ! ANY QUESTION?