The ins and outs of fluid therapy: crystalloids versus colloids

Transcription

1 The ins and outs of fluid therapy: crystalloids versus colloids Lindsay Vaughn, DVM, DACVECC Thoughts. Why does my pa,ent need fluids? Loca,on that fluids are needed (inters,,al versus intravascular)? Composi,on of fluid Volume of fluid needed Rate of fluid When are we done with fluids? Goal of Fluid Therapy Total Body Water Restore perfusion (resuscita,on) Restore and maintain hydra,on 60% of total body weight (0.6 L/kg) = WATER 1

2 5/12/15 Fluid Compartments Fluid Compartments Total Body Water (TBW) = ICF (66%) + ECF (33%) Total Body Water (TBW) = ICF + ECF Intracellular Fluid (ICF) 66% of TBW cytosol (0.4 L/kg) Extracellular Fluid Compartment ECF = inters,,al + plasma IntersJJal Fluid Compartment 75% of ECF (25% TBW) Fluid outside of vessels and outside of cells Contains lympha,cs Plasma 25% of ECF (8% TBW) Within vessels Contains plasma water, cellular components, proteins and electrolytes Extracellular Fluid (ECF) 33% of TBW (0.2L/kg) ECF = Inters,,al Fluid + Plasma Movement of body water Compartmentalizing membranes Endothelial lining of capillaries (intravascular from inters,,al) Cell membranes (separa,ng ICF from ECF) Forces dicta,ng water movement Cell membranes = osmo,c gradient Capillary wall movement = starlings forces 2

3 5/12/15 Total Body Water Hormonal mechanisms that maintain water and Na balance Regulate water and salt excre,on and reabsorp,on kidney Water intake- thirst mechanism, food DefiniJons HydraJon: pa,ent s total body water DehydraJon: reducing water content Decreased water intake (water/food) in rela,on to water lost (feces, urine, etc) Water deficit (inters,,al and intracellular) NOT intravascular water loss Hypovolemia: reduced intravascular volume Occurs with plasma water or whole blood loss A few mechanisms for TBW balance Hypotonic fluid loss (water with li_le or no solute content)! increase osmolality hypothalamic ADH release! water reabsorp,on by renal collec,ng ducts! conc urine Reduc,on in baroreceptor stretch! thirst center Hypovolemia s,mulates baroreceptors! release of ADH, aldosterone, renin, cor,sol! renal conserva,on of water and Na How do we determine TBW in a pajent clinically? Easily determined in normal subjects and athletes Controlled experimental condi,ons Gold standard - isotope dilu,on and neutron ac,va,on analysis techniques (HEALTHY) Mul,- frequency bioelectrical impedance analysis (CRITICAL pa,ents) Clinical pa,ents Much more challenging Body weight measurement 1 kg change in TBW = 1 L change in TBW Cau,on: third spacing Assess pa,ent via physical examina,on 3

4 DisJnguishing water deficits Evaluate your pa,ent Inters,,al versus intravascular versus intracellular loss Think about the pa,ent s history Clinical Assessment of HydraJon Status INTERSTITIAL Volume Changes Mm moisture, skin tent response, eye posi,on % DehydraJon PE findings < 5 Not detectable Tacky mm Decreased skin turgor Dry mucous membranes Retracted gloves within orbits Persistent skin tent Dull corneas Evidence of hypovolemia >12 Hypovolemic shock Death Clinical Assessment of HydraJon Status INTRAVASULAR Volume Changes Perfusion parameters Mucous membrane color Capillary refill,me Heart rate Pulse quality Clinical Assessment of HydraJon Status INTRACELLULAR Volume Changes Can not be iden,fied on PE Must rely on changes in effec,ve osmolality (Na concentra,on) Jugular venous distension 4

5 Fluid Loss HYPOTONIC Fluid Loss Li_le or no salt content (compared to ECF) Less common Loss of water from ECF! increased osmolality (Na) Consequently: ICF! ECF Neuro, death (neuronal cell shrinkage) Ex: Uncontrolled Diabetes Insipidus Fluid Loss ISOTONIC Fluid Loss (**most common) Loss/Gain fluid which is similar to ECF (li_le change in osmolality) No change in ICF INTERSTITIAL DEHYDRATION Ex: GI fluid loss, renal fluid loss, third space Change in PCV/TS, azotemia, etc Thoughts. Why does my pa,ent need fluids? Loca,on that fluids are needed (inters,,al versus intravascular)? Composi,on of fluid Volume of fluid needed Rate of fluid Fluid therapy Crystalloids Contain small solutes (majority are electrolytes) Freely permeable to capillary endothelium Equilibrate in ECF (intravascular and inters44al w/in min) < 1/3 remains in intravascular space 30 min administra4on Osmosis occurs based on tonicity between different fluid compartments When are we done with fluids? 5

6 Crystalloid Fluid Classified based on tonicity Hypotonic Isotonic Hypertonic Hypotonic Crystalloid Fluids Ex: 0.45% NaCl and D5W Osmolarity and [Na] lower than ECF Distribute throughout ECF and ICF (more se_ling intracellularly) Used to replenish free water deficits Can be beneficial for heart pa,ents Tolerate less of an elevated intravascular volume NEVER BOLUS cerebral edema Hypertonic Crystalloid Fluid Higher osmolarity and [Na] than ECF Free water from ICF! ECF (intravascular) 3-5 x volume administered Transient- las,ng < 30 min Used to treat hypovolemic shock, intracranial hypertension, and severe hyponatremia Dose: 4 ml/kg of 7.5% saline Prolonged effects: HTS + colloid Isotonic Crystalloid Fluids Ex: LRS, P- lyte, Norm- R, 0.9% NaCl Osmolarity and [Na] similar to ECF mosml/l Used to expand inters,,al and intravascular space and maintain Does not cause large shit between ECF and ICF Commonly used to treat inters,,al dehydra,on 6

7 Isotonic Crystalloid ComposiJon Fluid Type Osm Na K Cl Mg Ca 0.9% NaCl LRS P- lyte Norm- R All replacement fluids Most fluids are acidic Buffers consume hydrogen ions! alkalinizing effect Acetate/Gluconate: P-lyte and Norm- R Lactate: LRS Isotonic crystalloids- Not benign Inters,,al fluid gain (volume overload)! inters,,al edema, pulmonary edema, and cerebral edema Hemodilu,on of blood cons,tuents Anemia Hypoproteinemia Electrolyte derangements Hypocoagulability Choose your fluid by thinking about your pajent.. Sodium What type of loss? Avoid shit in Na (max meq/l/hr) Correc,on should occur over equivalent,me to onset of derangement Choose fluid with similar Na content 0.9% NaCl Upper GI obstruc,on? Chloride? Head trauma Choose your fluid by thinking about your pajent.. LRS Avoid in pa,ents with diabe,c ketoacidosis Avoid in pa,ents with liver dysfunc,on May be beneficial in young pa,ents as energy substrate (lactate =metabolic fuel for neonates) Acetate containing solujons Causes hypotension when bolus administra,on?? 7

8 5/12/15 Fluid Therapy Plan Consider the following: Fluid deficit Maintenance Fluid Therapy Ongoing losses Maintenance CalculaJons Sensible and insensible ongoing fluid losses Parallel res,ng energy requirements Variable based on cri,cal nature of pa,ent and body condi,on score Fluid Therapy Plan Fluid Deficit PE varied based on body compartment Intracellular: cerebral obtunda,on, hypernatremia, hyperosmolality, (NO PE signs of dehydra,on) Inters,,al: dehydra,on symptoms Intravascular: pale mm, poor pulse quality, tachycardia, prolonged CRT, cold extremi,es Fluid Therapy Plan Ongoing losses Understand underlying disease process EX: GI losses (vomi,ng and diarrhea) Adjust throughout treatment Poten,al formulas: 30 (kg) +70/day ml/kg/day 2-4 ml/kg/hr Es4mates: may not be accurate when pa4ent is < 2 kg or > 40 kg 8

9 Fluid therapy rate for a stable pajent deficit + maintenance + esjmated ongoing losses x amount of Jme Deficit (ml) = [Kg x 1000] x [% dehydra,on/100] Maintenance = ml/kg/hr Potassium SupplementaJon K Conc (meq/l) meq KCl to 1 L fluid Max Infusion Rate (ml/kg/hr) < Ex: 7% dehydrated pa,ent (10 kg) with no going losses [10 kg x 1000] x [7%/100] = 700 ml over 24 hours = 29 ml/hr 50 ml x 10 kg= in 24 hrs = 20 ml/hr 29 ml/hr + 20 ml/hr = 49 ml/hr (adjust based on PE and losses) Potassium infusion should not exceed 0.5 meq/kg/hr DO NOT BOLUS FLUID WITH K+ SUPPLEMENTATION Daily evaluajon Calculate fluid requirements over realis,c,me frame for replacement Assess pa,ent parameters, hydra,on, elimina,ons, etc q 4 hr Assess electrolytes minimum q 24 hours Na changing at appropriate rate (No > meq/l/hr) Potassium supplementa,on Colloids Colloid par,cles suspended in isotonic crystalloids Contain large molecules (>10,000 Da) Types of colloids Synthe,c starch colloid solu,ons Hetastarch Tetrastarch Pentastarch Blood products Allogenic albumin (canine or feline) Human albumin 9

10 SyntheJc Starch Colloids Hydroxyethyl Starch Vary based on molecular weight and ra,o of hydroxyethyl group subs,tu,on (C2:C6 ra,o) (all related to longer T1/2 not higher COP) Hetastarch Hespan: 6% solu,on suspended in 0.9% NaCl Hextend: 6% solu,on suspended in LRS PotenJal indicajons for synthejc colloid administrajon Refractory hypotension (lack of response to crystalloids) Hypoalbuminemia Tetrastarch Vetstarch (voluven) Lower MW, lower C2:C6 ra,o Pentastarch (not approved in US) TheoreJcal benefits of colloids Increase intravascular volume without loss to inters,,um 1.5x volume administered via movement of fluid from extravascular to intravascular space! increase COP Reduce extravasa,on of fluids into inters,,al space TheoreJcal Benefits of Colloids Plugging leaks in vascular endothelium Maintain volume expansion Healthy dog study: 20 ml/kg HES 27.2% increase in blood volume immediately ater infusion 36.8% at 30 minutes ater infusion maintenance of 26.6% at 4 hrs post infusion. 10

11 Adverse Effects of SyntheJc Colloids Coagula,on disorders (dose dependent) Hemodilu,on Decrease ac,vity of vwf and factor VIII Platelet dysfunc,on Blackbox Warning by FDA The FDA has recommended against the use of HES in cri,cally ill pa,ents with pre- exis,ng renal disease, sepsis or undergoing open heart surgery with bypass Increased incidence of acute kidney injury, increased mortality and need for renal replacement therapy Adverse effects of synthejc colloids Does not decrease overall fluid requirements (versus crystalloids alone) SAFE TRIAL; ALBIOS TRIAL; VISEP TRIAL; CRYSTMAS TRIAL; CHEST TRIAL Ini,al volume sparing effect of colloids but ul,mately same total volume of fluids u,lized Does not plug leaks Labeled HES with fluorescein Diffusion from intravascular space into,ssues within seconds of administra,on Colloids and pajent outcome Unknown survival advantage with colloids SAFE trial- no outcome differences ALBIOS- no survival advantage with albumin CHEST trial- no difference in mortality at 90 days 11

12 What does this mean for veterinary pajents? Large scale veterinary clinical trials are needed to assess outcome and adverse effects Cau,on with interpre,ng human data to veterinary pa,ents Vet pa,ents are hospitalized a shorter period of,me (days) versus human pa,ents (weeks) What does this mean for veterinary pajents? Severity of vet pa,ents oten less than human pa,ents (finances?) CRISTAL AND CRYSTMAS trials: More applicable to veterinary ICU pa,ent Focused on hypovolemic pa,ents with severe volume deficits requiring rapid correc,on and short dura,on HES use Lower total dose; not more at risk of needing RRT U,liza,on of HES short term? Doses of colloid therapy Bolus: 2-5 ml/kg IV over minutes Total dose: Dog: ml/kg Cat: 5-10 ml/kg Tetrastarches: up to ml/kg/day What about colloids with hypoalbuminemia? Consider utilizing crystalloids and colloids When to use? Alb < mg/dl Peripheral edema Hypotension unresponsive to crystalloids 12

13 Natural Colloid Therapy Allogenic albumin (species specific albumin) Unavailable in the United States 25% Human Albumin Healthy dogs! life threatening anaphylac,c reac,ons, Type III hypersensi,vity reac,on (delayed) Cri,cally ill dogs!safer than in healthy dogs due to compromised immune system Natural Colloid Therapy Fresh Frozen Plasma Cloyng factors and plasma proteins Less effec,ve than synthe,c starches for raising onco,c pressure Need ml/kg of plasma to raise plasma albumin by 1 g/dl Fluid Therapy Plan Hemodynamically stable pa,ent with hypoalbuminemia (< 1.5 mg/dl) Fluid Therapy Plan Hemodynamically stable pa,ent with hypoalbuminemia (< 1.5 mg/dl) deficit + maintenance + es,mated ongoing losses x amount of,me Ex: 7% dehydrated pa,ent (10 kg) with no going losses [10 kg x 1000] x [7%/100] = 700 ml over 24 hours = 29 ml/hr 50 ml x 10 kg= in 24 hrs = 20 ml/hr 29 ml/hr + 20 ml/hr = 49 ml/hr of an isotonic crystalloid (adjust based on PE and losses) 13

14 Fluid Therapy Plan Hemodynamically stable pa,ent with hypoalbuminemia (< 1.5 mg/dl) Ex: 7% dehydrated pa,ent (10 kg) with no going losses 49 ml/hr of an isotonic crystalloid Colloid administra,on (10-20 ml/kg HES) Ex: 10 kg x 20 ml/kg= 200 ml over 24 hrs= 8.33 ml/hr of HES Ater calcula,ons: REDUCE crystalloid volume by 25% 49 ml/hr x 0.25= ml therefore 37/hr ml of crystalloid + 8 ml/ hr of HES SHOCK Inadequate cellular energy produc,on Three major forms: Hypovolemic shock Distribu,ve shock Cardiogenic shock Stages of shock Compensated Decompensated Shock Compensated Increased sympathe,c tone! Vasoconstric,on, increased cardiac contrac,lity, and tachycardia (improve CO) Inters,,al fluid and ECF! Intravascular space Ac,va,on of RAAS! Na and H20 reten,on PE: mildly dull, tachycardia, normal or prolonged CRT, cool extremi,es, tachypnea and normal BP and pulse quality SHOCK Decompensated Compensatory mechanisms no longer adequate PE: pale mm, poor peripheral pulses, depressed menta,on, hypotension! organ failure and death 14

15 What about the hypovolemic (unstable pajent)???? Interstitial loss? Hypovolemia Hypovolemia: decreased volume of fluid in vascular system +/- whole body fluid deple,on DehydraJon: deple,on of whole body fluid Intravascular volume depletion? Hypotension? Fluid Therapy Plan Hypovolemic Shock Symptoms related to hypovolemic shock Dull menta,on Compensated or decompensated shock Goal directed therapy: Titrate treatment un,l resuscita,on endpoints achieved Alert, improvement in heart rate, pulse quality, CRT, temperature of extremi,es, normaliza,on of BP, lactate levels Hypotensive resuscita,on (BP= mmhg) Shock Fluids Crystalloids typically first choice for shock resuscita,on Bolus dose of crystalloids is equivalent to 1 blood volume: 90 ml/kg (dog) and 60 ml/kg (cat) Administer ¼ calculated shock dose over minutes Re- evaluate pa,ent to determine if addi,onal ¼ shock dose should be administered. 15

16 Shock Fluids Typically will complete incremental administra,on of ½ (some4mes full shock dose) of crystalloids Full shock dose with excessive losses (ex: parvovirus, HGE, heat stroke, etc) What about hypertonic saline (7% solujon)? Severe hemorrhagic hypovolemic shock Greatest cardiovascular benefit with the least volume of infused fluids Inters,,um! Intravascular space Colloid challenge Persistent hypotension Concern over administering large amounts of crystalloids (hypoalbuminemia) 2-5 ml/kg over minutes Dose: Dog 4-5 ml/kg; Cat 2-4 ml/kg Short- lived volume expansion (30 60 min) Note: Replenish inters,,al fluid loss with crystalloid therapy Contraindicated in hypernatremic or dehydrated pa,ents Turbo- Starch 23% Hypertonic saline + 6% Hetarstarch Colloid intended to keep hypertonic saline in vasculature longer Total dose 3-5 ml/kg Create solu,on in a 1:2 ra,o Monitor [Na] concentra,on (typically transiet) Ex: 5 ml/kg dose for 12 kg dog = 60 ml 1 part 23.4% HS (20 ml) + 2 part (40 ml) 6% HES creates a 7.5 hypertonic saline solu,on Once normovolemia is restored, calculate to replace dehydra,on + ongoing losses deficit + maintenance + es,mated ongoing losses x amount of,me 16

17 Pa,ent hemodynamically stable and clinically stable, now what??? Maintain on calculated fluid volume and adjust PRN to replace inters,,al fluid volume Serial evalua,on pa,ent Electrolytes: Correct Na as rapidly as it changed ( < mleq/kg/hr) Body weight: q 12 hr Monitoring Ins and Outs Quan,fy outs: Urinary Catheter Collect all urine voids Pee pads (1 gram = 1 ml of urine) Surgical management of cause of hypotension Prepare for pa,ent discharge Monitoring Ins and Outs Adjust fluids for ins/outs Ex: Ins < Outs Ins: 200 mls over 4 hrs (50 ml/hr) Outs: 250 mls over 6 hrs (62.5 ml/hr) Increase rate to 62.5 ml/hr for next 4-6 hrs and reassess Ex: Ins > Outs Ins: 200 mls over 4 hrs (50 ml/hr) Outs: 50 mls over 4 hrs (12.5 ml/hr) (<0.62 ml urine/kg/hr) If hydra,on corrected, pa,ent is oliguric and more fluids are doing nothing therefore decrease to maintenance and treated for oliguria DisconJnuaJon of Fluid Therapy Do NOT discon,nue fluid therapy abruptly Gradually decrease over 24 hour period May have increased water requirements over next couple days Hetastarch Dampen signal to kidneys Wean colloid to s,mulate albumin produc,on 17

18 Fluids during anesthesia Fluids are recommended during anesthesia Correct normal ongoing losses, support CV func,on, and maintain TBW during long anesthe,c periods Counter nega,ve effects of anesthe,c agents (hypotension and vasodila,on) Con,nuous flow via IV catheter to prevent clots AnestheJc fluid recommendajons Maintenance rate + any necessary replacement rate (< 10 ml/kg/hr) Ini,al rate (feline): 3 ml/kg/hr Ini,al rate (canine): 5 ml/kg/hr Adjust rate and type of fluid based on pa,ent assessment and monitoring Reduce fluid administra,on rate if anesthe,c procedure lasts > 1 hr Reduce rate by 25% q hr un,l maintenance rate achieved (if pa,ent is stable) Hypotension in the anesthejc pajent Decreased inhalant concentra,on Consider addi,onal injectable medica,ons Crystalloid bolus (10 ml/kg) Mul,ple?? Pre- anesthe,c status? Losses? QUESTIONS??? Colloid bolus (3-5 ml/kg) Pressor or balanced anesthesia 18