Fluid Therapy PDF

# Fluid Therapy ## VETM 5291: Cardiovascular Respiratory Hemolymphatic 2 ## Learning Goals - Describe the differences between - Crystalloids and colloids - Different classifications for crystalloids - Synthetic and biologic colloids - Summarize the uses, indications, and potential sid...

# Fluid Therapy ## VETM 5291: Cardiovascular Respiratory Hemolymphatic 2 ## Learning Goals - Describe the differences between - Crystalloids and colloids - Different classifications for crystalloids - Synthetic and biologic colloids - Summarize the uses, indications, and potential side effects for each fluid type - List and describe the components of a fluid plan - Design a fluid therapy plan for a patient - Know the indications for electrolyte/dextrose supplementation and be able to perform calculations ## Fluid Balance - 60-70% of adult body weight - Up to 90% of neonates ## Fluid Dynamics depends on: - Osmotic pressure - Oncotic pressure - Hydrostatic pressure - exerted by fluid pressing on capillary/cell walls - Reflection coefficient $Jv = Kf [ (Pc- Pi) – σ(πc – πί)]$ ## Fluid Therapy - Replacement of losses - Resuscitation - Rehydration - Providing maintenance fluids - Vehicle - Drugs - Electrolytes ## Categories of Fluids - Crystalloids - Isotonic Replacement Crystalloids - Maintenance crystalloids - Hypertonic crystalloids - Colloids - Biologic - Synthetic ## Crystalloids - Water-based solutions - Contain small osmotically active molecules which are permeable to membranes - Crystalloids redistribute! < 1/3 left in vascular space after 30-40 minutes ## Crystalloid Characterization - Tonicity - Buffer content - Acidifying versus alkalinizing - Electrolyte content - Balanced vrs unbalanced - Replacement vrs maintenance ## Tonicity | Tonicity | Description | |---|---| | Isotonic | General use | | Hypertonic | Resuscitation | | Hypotonic | Free water replacement | ## Buffer Content | Buffer Type | Example Fluids | Buffer | Effect | |---|---|---|---| | Buffered | LRS, Plasmalyte, normosol R | Lactate, Acetate, gluconate | Alkalinization | | Unbuffered | 0.9% NaCl | None | Acidifying (high Cl) | ## Replacement Crystalloids | Fluid | Na+ mEq/L | CI- mEq/L | K+ mEq/L | Ca2+ mEq/L | Mg2+ mEq/L | Osm mOsm/L | |---|---|---|---|---|---|---| | 0.9% NaCl | 154 | 154 | 0 | 0 | 0 | 308 | | LRS | 130 | 109 | 4 | 3 | 0 | 272 | | Norm-R & P-lyte | 140 | 98 | 5 | 0 | 3 | 296 | ## Maintenance Crystalloids | Fluid | Na+ mEq/L | CI- mEq/L | K+ mEq/L | Ca2+ mEq/L | Mg2+ mEq/L | Osm mOsm/L | |---|---|---|---|---|---|---| | 0.45% NaCl +2.5% dex | 77 | 77 | 0 | 0 | 0 | 280 | | 1/2 strength LRS + 2.5% dextrose | 65.5 | 55 | 2 | 1.5 | 0 | 263 | | Normosol M + 5% Dex | 40 | 40 | 13 | 0 | 3 | 363 | ## 5% Dextrose in Water | Fluid | Na+ mEq/L | CI- mEq/L | K+ mEq/L | Ca2+ mEq/L | Mg2+ mEq/L | Osm mOsm/L | |---|---|---|---|---|---|---| | D5W | 0 | 0 | 0 | 0 | 0 | 252 | Used to provide free water and as a diluent. ## Hypertonic Crystalloids - Osmotic pull from interstitium - Hypertonic saline - Primarily for resuscitation - Hypertonic bicarbonate - CALVES with severe diarrhea ## Hypertonic Saline - Contraindications - Dehydration - Hyper- or hypo- natremia - Potential side effects - Dehydration - Hypernatremia - Bradycardia - Hypotension - Bronchoconstriction ## Uses for Crystalloids - Replacement of losses - Resuscitation of hypovolemia - Rehydration - Ongoing excess losses - Providing maintenance fluids - Vehicle - Drugs - Electrolytes ## Choosing a Crystalloid - Fluid Plan - Serum sodium level - Acidemia versus alkalemia - Calcium levels? - Concurrent drug therapy? - Liver disease? ## Potential Side Effects - Exceeding Starling Curve - Fluid overload - Edema, effusions - GI stasis - Dilutional coagulopathy ## The primary difference between a replacement and a maintenance crystalloid solution is the 1. pH 2. potassium concentration 3. sodium concentration 4. **presence of calcium or magnesium** ## Colloids - Large molecules that are restricted to the plasma compartment - Provide oncotic pressure - Innate - Gibbs-Donnan effect ## Available Colloids - Biologic - Plasma - Albumin - Canine - Human - Synthetic - Hydroxylethylstarches - Gelatins ## Uses for Plasma - Provide clotting factors - Hypoalbuminemia - Inefficient - Providing immunoglobulins - Failure of passive transfer ## Potential side effects of plasma - Transfusion reaction - Fluid overload ## Albumin - Oncotic pressure - Drug carrier - Bilirubin and FFA carrier - Anti-inflammatory - Anti-coagulant ## Albumin Replacement - Species-specific albumin - Only canine available - Human albumin - 5%, 25% ## Uses for Albumin - Severe hypoproteinemia - Shock poorly responsive to crystalloids ## Possible Side Effects of Albumin - Fluid overload - Transfusion reactions - Especially HUMAN product - Facial edema - Anaphylaxis - Vomiting, fever - Delayed immune mediated disease - Death - Species-specific - Limited availability ## Synthetic Colloids: Hydroxyethylstarches (HES) - Polysaccharide - Similar to glycogen - Primarily amylopectin ## HES classification - Molecular weight - High: > 400 kD - Med: 200-300 kD - Low <200 kD - Degree of substitution - Average number of hydroxyethyl groups per glucose unit within the polymer ## Hydroxyethylstarches | Colloid | Avg MW | Degree of Substitution | Half-life | |---|---|---|---| | Hetastarch (Hespan, Hextend) | 450 | 0.7 | 24-48h | | Pentastarch (HAESteril) | 264 | 0.4-0.5 | 12 h | | Tetrastarch (Voluven, Vetstarch) | 130 | 0.4 | 12 | ## Uses for Hydroxyethylstarch - Plasma volume expansion - Resuscitation - Vascular leak - Oncotic support - Hypoproteinemia ## Potential HES side effects - Fluid overload - ↓ crystalloids by ½ - Anaphylactoid rxn - Pruritis - Coagulopathy - Platelets - vWf, VIII - Dilutional - Acute kidney injury - Human HES patients with higher rate of ARF than crystalloids - Dose dependent - Increased Mortality - Cardiac by-pass - Sepsis ## Fluid Therapy Plan - Four parts - **Resuscitation** - **Rehydration** - **Maintenance** - **Ongoing losses** ## Resuscitation - Must be completed FIRST before considering the rest of the plan ## Fluids for Resuscitation - Isotonic replacement crystalloids - Replacement solutions only - Hypertonic saline (HTS) - 7.2% (8x) is most common - Colloids - Hydroxyethylstarches (HES) - Sometimes plasma/albumin - RBCs - Severe anemia ## Fluids used for Shock Therapy | Fluid Type | Cat/camellid | Dog, Ruminants, horses | Birds | Reptiles | |---|---|---|---|---| | Isotonic crystalloids (TOTAL shock dose (ie blood volume)) | 50-60 mL/kg | 90 mL/kg | 60-120mL/kg | 70 mL/kg | | IV Shock bolus size | 10-15 mL/kg | 20-30 mL/kg | 10-15 mL/kg | 10 mL/kg | | 7.2% Hypertonic saline (IV only) | 2-3 mL/kg | 3-5 mL/kg | 3-5 mL/kg | | | Hydroxyethylstarch | 3-5 mL/kg (up to 15 mL/kg) | 3-5 mL/kg (up to 20 mL/kg) | | | ## Isotonic Replacement Crystalloids in Resuscitation - Give 1/4 - 1/3 of TOTAL shock dose - 10-30 mL/kg depending on species - Over ~15 minutes - Can be more conservative PRN - Beware of redistribution - Can be more conservative PRN ## Hypertonic Saline for Resuscitation - Severe shock - Traumatic brain injury - Small volume resuscitation - Very large patients - 3-5 mL/kg - Repeat once if necessary - Recheck Na if want to give more... - Not use if severe dehydration - Not in severe hypernatremia - Or hyponatremia ## Hypertonic Bicarbonate in Calves >8 days of age | Clinical Assessment | Base Deficit (mmol/L) | Therapy | |---|---|---| | **Visual** | **Descriptive** | **30 kg** | **35 kg** | **40 kg** | **45 kg** | **50 kg** | **55 kg** | **60 kg** | | | Standing, strong suck reflex | | | | | | | | | | Standing, weak suck reflex | | | | | | | | | | Sternal recumbency | 225 | 262.5 | 300 | 337.5 | 375 | 412.5 | 450 | | | Lateral recumbency | 300 | 350 | 400 | 450 | 500 | 550 | 600 | *Should contain at least 60 mmol/L of acetate or bicarbonate. *Total bicarbonate requirement for intravenous fluid therapy, mmol. ## Hydroxyethylstarch in Resuscitation - Hypoproteinemic - Decompensatory Shock - Failing crystalloids alone - Boluses of approximately 5 mL/kg - Up to 15 mL/kg (cat, camellid) - Up to 20 mL/kg (dog, horses, ruminants, most others) ## Lucky: 20 kg 5 yr MC mixed breed - HBC 20 minutes ago - QAR - T=101°F - P= 180-190 BPM, - MM pink, moist, CRT= 2-2.5 sec - Pulses weak - R = 36 /min, eupneic - Pain and large swelling associated with left femur - PCV= 42 %, TS = 5.6 g/dl ## What clinical stage of shock? - Early Decompensatory ## What category of shock? - Hypovolemic ## Treatment? - **Resuscitation:** - Fluid type? - TOTAL Shock dose = 90 mL/kg x 20 kg = 1800 mL - Administer ¼-1/3 of this volume: 450-600 mL over 15 min (a 500 mL bag is good)... - Or 20 mL/kg... - **Reassess!** ## What if you reassess and find...? - HR 160, pulses moderate - mm pale pk, CRT = 2 seconds ## What if you find... - HR = 120/min, pulses strong - MM pink, CRT 1 second ## Fluid Therapy Plan - Four parts - Resuscitation - **Maintenance** - Rehydration - Ongoing losses ## Maintenance Fluid Needs - What is needed to maintain homeostasis - Normal losses - Low sodium - Optimally replaced using maintenance crystalloids - Sometimes use replacement crystalloids for simplicity ## Maintenance Fluid Rates | Fluid Type | Maintenance Rate-Adult | Maintenance Rate-Neonates (~2-3x adult) | |---|---|---| | Cat/camellid, some exotics | 40-50 mL/kg/24h | 80 mL/kg/24h | | Dog, Ruminants, horses, small mammals | 50-60 mL/kg/24h | 80-180 mL/kg/24h | | Birds | 100 mL/kg/24h | 200-300 mL/kg/24h | | Reptiles | 10-30 mL/kg/24h | | ## 3 yr, 6 kg MC cat with jaw fracture - On fluids preoperatively - Just need to meet maintenance fluids - 6 kg x 40 mL/kg/24 hours = 240 mL/24 h - or approximately 10 mL/hr ## Of what type of fluid?? ## Fluid Therapy Plan - Four parts - Resuscitation - Maintenance - **Rehydration** - Ongoing losses ## Rehydration/Replacement - Replace losses - Generally high in sodium and electrolytes - Fluid of choice = balanced, isotonic replacement crystalloids ## Dehydration Estimate in Dogs, Cats, Small Mammals | Percent Dehydration | Clinical Signs | |---|---| | < 5 | Not detectable on physical examination | | 5-6 | Subtle loss of skin turgor* | | 6-8 Mild decrease in skin turgor, dry (tacky) mucous membranes | | 8-10 | Definite delay in return of skin to normal position dry ( or tacky) mucous membranes, Eyes possibly sunken in orbits | | 10-12 | Persistent skin tent, dull corneas, evidence of hypovolemia (tachycardia, cool extremities, rapid/weak pulse) | | >12 | Definite signs of hypovolemic shock, Death imminent | * Skin turgor is dependent upon the amount of subcutaneous fat and elastin as well as interstitial volume. Skin pliability should be tested over the lumbar region preferably with the animal standing. Obese animals may appear well hydrated despite being dehydrated owing to excessive subcutaneous fat. Emaciated and older animals may appear more dehydrated than they actually are owing to a lack of subcutaneous fat and elastin. Persistent panting may dry the oral mucous membranes, creating a false impression of dehydration. ## Rehydration/Replacement **Example 1:** A 16 kg dog is est to be 10% dehydrated - Wt in kg x % dehydration = Liters of fluid deficit - 16 kg x 0.1 = **1.6 Liters deficit** - Replace over 12-24 hours - 1.6 Liters/24 hours = **67 mL/hr** ## Of what fluid type?? ## Rehydration/Replacement **Example 2:** A 500 kg horse is est 8% dehydrated. - Wt in kg x % dehydration = Liters of fluid deficit - 500 kg x 0.08 = **40 Liters deficit** - Replace over 12-24 hours - 40 Liters/24 hours = **1.7 Liters/hr** ## Rehydration - 5 kg MC cat with intermittent vomiting x 2d, estimated <5% dehydrated, treated as outpatient - 5 x 0.05 = 0.25 L = 250 mL deficit ## But this is outpatient... What should we do? - Give 20 mL/kg (100 mL) subcutaneously - reassess, can readminister PRN ## Of what type of fluid?? ## Hydroxyethylstarch for non-shock use - Hypoproteinemia - Hetastarch: - 1 mL/kg/hr, 20 mL/kg/day - Tetrastarch: up to 50mL/kg/day - Smaller molecule is excreted more rapidly ## Ongoing Losses - EXCESSIVE losses - Vomiting/reflux, diarrhea - Urinary losses - Third spacing - Measure amount lost - Estimate amount lost: weigh - 1 gram fluid ≈ 1 mL fluid - Generally high electrolyte losses - use replacement crystalloid ## Examples - 200 mL fluid in a closed wound suction drain q 4 hrs - ...increase fluids by 50 mL/hr - Cat produces ~50 g of vomitus every 6 hrs - 50 g = ~ 50 mL over 6 hours - ...increase fluids by ~ 8 mL/hr ## If this was a 600 kg horse with these losses, we would not worry about that volume... ## Lucky: 20 kg 5 yr MC mixed breed - HBC 20 minutes ago - QAR - T = 101°F - P=180-190 BPM, - MM pink, moist, CRT= 2-2.5 sec - Pulses weak - R = 36 /min, eupneic - Pain and large swelling associated with left femur - PCV= 42 %, TS = 5.6 g/dl ## Treatment? - **Resuscitation:** - Fluid type? - TOTAL Shock dose = 90 mL/kg x 20 kg = 1800 mL - Administer ¼-1/3 of this volume: 450-600 mL over 15 min (a 500 mL bag is good)... - Or 20 mL/kg... - **Reassess!** ## After Resuscitation - Normal pre-HBC: no dehydration, no ongoing major losses - Maintenance fluids: 50-60 mL/kg x 20 kg = 1000-1200 mL/day or ~50 mL/hr - Often more fluids than just maintenance - For this patient, perhaps 75-100 mL/hr total dose ## Farrah - 10 week F Lhasa cross - Wt = 1 kg - Head caught in reclining mechanism of Lazy-boy ## Owner reports dog vocalized for awhile and became quiet during car ride ## Farrah - Stupor - T = 96°F - P = 90 BPM - R = 50 /min, lungs auscult normally - Hemorrhage OS (scleral) and AS - Ventral strabismus OS - Doppler = 50 mmHg - PCV = 35%, TS=6.8 mg/dl ## Plan? - Resuscitation? - 3-5 mL/kg hypertonic saline (CPP=MAP-ICP) - Rehydration? - not needed - Maintenance? - puppies have higher water requirement... so start 2x (adult) maintenance ~ 120 mL/kg/d - = 5 mL/hr of what fluid?? - Ongoing losses? TBD ## Routes of Fluid Administration - Enteral - Voluntary - tube / gavage - Per rectum – horses, ruminants - Subcutaneous - Intraperitoneal / intracoelomic - Intravenous - Intraosseous ## Fluid Supplementation - Potassium - Dextrose - Bicarbonate