UPDATE ON VOLUME RESUSCITATION HYPOVOLEMIA AND HEMORRHAGE HUMAN CIRCULATORY SYSTEM OPERATES WITH A SMALL VOLUME AND A VERY EFFICIENT VOLUME RESPONSIVE PUMP. HOWEVER THIS PUMP FAILS QUICKLY WITH VOLUME LOSS AND IT CAN BE FATAL WITH JUST 35 TO 40% LOSS OF BLOOD VOLUME. DISTRIBUTION OF BODY FLUIDS HEMORRHAGE AND HYPOVOLEMIA TOTAL BODY FLUID ACCOUNTS FOR 60% OF LEAN BODY WT IN MALES AND 50% IN FEMALES. BLOOD REPRESENTS ONLY 11-12 % OF TOTAL BODY FLUID. CLINICAL MANIFESTATIONS OF HYPOVOLEMIA SUPINE TACHYCARDIA PR >100 BPM SUPINE HYPOTENSION <95 MMHG POSTURAL PULSE INCREMENT: INCREASE IN PR >30 BPM POSTURAL HYPOTENSION: DECREASE IN SBP >20 MMHG POSTURAL CHANGES ARE UNCOMMON WHEN BLOOD LOSS IS <630 ML. 1
COMPARED TO OTHERS, POSTURAL PULSE INCREMENT IS A SENSITIVE AND SPECIFIC MARKER OF ACUTE BLOOD LOSS. CHANGES IN HEMATOCRIT SHOWS POOR CORRELATION WITH BLOOD VOL DEFICITS AS WITH ACUTE BLOOD LOSS THERE IS A PROPORTIONAL LOSS OF PLASMA AND ERYTHROCYTES. INFLUENCE OF ACUTE HEMORRHAGE AND FLUID RESUSCITATION ON BLOOD VOLUME AND HCT MARKERS FOR VOLUME RESUSCITATION CVP AND PCWP USED BUT EXPERIMENTAL STUDIES HAVE SHOWN A POOR CORRELATION BETWEEN CARDIAC FILLING PRESSURES AND VENTRICULAR EDV OR CIRCULATING BLOOD VOLUME. CHEMICAL MARKERS OF HYPOVOLEMIA MORTALITY RATE IN CRITICALLY ILL PATIENTS IS NOT ONLY RELATED TO THE INITIAL LACTATE LEVEL BUT ALSO THE RATE OF DECLINE IN LACTATE LEVELS AFTER THE TREATMENT IS INITIATED ( LACTATE CLEARANCE ). Classification System for Acute Blood Loss Class I: Loss of <15% Blood volume Compensated by transcapillary refill volume Resuscitation not necessary Class II: Loss of 15-30% blood volume Compensated by systemic vasoconstriction 2
Classification System for Acute Blood Loss Cont. Class III: Loss of 30-45% blood volume Not compensated any longer Hypotension,impaired organ function Class IV: Loss of >45% blood volume MSOF, Severe Lactic acidosis FLUID CHALLENGES MOST COMMONLY USED IS 500 ML OF ISOTONIC SALINE INFUSED OVER 10-15 MINS. AN INCREASE OF CARDIAC OUTPUT BY 12-15% AS MEASURED BY NON-INVASIVE MEANS IS CONSIDERED AS EVIDENCE OF FLUID RESPONSIVENESS. Volume Resuscitation in Septic Shock 1) Infuse 500-1000 ml of crystalloid or 300-500 ml of Colloid over 30 minutes 2) Repeat as needed until CVP reaches 8-12 mm HG 3) If hypotension persists after the initial volume resuscitation, start Dopamine or Norepinephrine. 4) Reduce volume infusion Volume in Resuscitation in Septic Shock Cont. 5) Achieve MAP 65 mm HG 6) Positive fluid balance is associated with increased mortality in septic shock 6) Norepinephrine is preferred because it is more likely to raise BP then Dopamine and less likely to trigger arryhthmias CRYSTALLOID VS COLLOID CRYSTALLOID AND COLLOIDS CRYSTALLOIDS DIFFUSE READILY THROUGH A SEMI-PERMEABLE MEMBRANE: NORMAL SALINE COLLOIDS DON T READILY CROSS THROUGH A SEMI-PERMEABLE MEMBRANE: ALBUMIN 3
DIFFERENT TYPES OF VOLUME REPLACEMENT COMPARISION OF DIFFERENT FLUIDS NORMAL SALINE VS PLASMA WHEN COMPARED TO PLASMA NS HAS A HIGHER NA AND CL CONCENTRATION, HIGHER OSMOLALITY AND A LOWER PH. LACTATED RINGER IS MORE SIMILAR TO PLASMA THAN NS. INFUSION OF NS PROMOTES MORE INTERSTITIAL EDEMA THAN LACATED RINGER OR PLASMA-LYTE. NORMAL SALINE VS LR THIS IS RELATED TO INCREASED NA LEVEL FRON NS WHICH INCREASES THE TONICITY OF INTERSTITIAL FLUID AND PROMOTES NA RETENTION BY SUPPRESSING RAA AXIS. EFFECTS OF FLUID REPLACEMENT ON PLASMA VOLUME AND INTERSTITIAL FLUID VOLUME Plasma vs Intestitial Fluid 1) Extracellular fluid accounts for about 40% of total body fluid 2) It is composed of Extravascular (Interstitial) and Intravascular (plasma) fluid compartments 3) Plasma volume is about 25% of interstitial fluid volume 4) 1 L of NS infused-750 ml will distribute in interstitial fluid and 250 ml in plasma 4
EFFECT ON PH OF BLOOD RINGER S LACTATE AND RINGER S ACETATE ONLY DIFFERENCE IS THE BUFFER LACTATE VS ACETATE RINGER S ACETATE IS PREEFERRED IN PATIENTS WITH IMPAIRED LIVER FUNCTION AS LIVER IS INVOLVED IN METABOLIZING LACTATE WHILE ACETATE IS METABOLIZED IN MUSCLE. MAIN ADVANTAGE IS LACK OF EFFECT IN PH. MAIN DISADVANTAGE OF RINGER S SOLUTIONS IS THE CA CONTENT WHEN USED AS A DILUENT FOR PRBC S WHICH CAN PROMOTE CLOT FORMATION. NORMOSOL AND PLASMALYTE BALANCED SALT SOLUTIONS THEY HAVE MG INSTEAD OF CA AND CONTAIN BOTH ACETATE AND GLUCONATE AS BUFFERS. THEY CAN BE USED AS DILUENTS FOR PRBC TRANSFUSIONS. CLINICAL STUDIES HOWEVER SHOWS NO BENEFIT OVER ISOTONIC CRSTALLOIDS. HYPERTONIC SALINE 3% AND 7.5% NaCL SOLUTIONS ARE USED. THEY ARE VERY GOOD IN ANIMAL STUDIES FOR VOLUME RESUSCITATION IN HEMORRHAGIC SHOCK. HOWEVER NOT FOUND TO BE BETTER THAN ISOTONIC FLUIDS IN CLINICAL STUDIES. DEXTROSE SOLUTIONS INFUSION OF DEXTROSE SOLUTIONS CAUSE LESS INTRAVASCULAR VOLUME EXPANSION AND MORE CELLULAR SWELLING. D5NS HAS AN OSMOLALITY OF 560 mosm/l AS YOU ADD 50 GMS OF DEXTROSE. IN CRITICALLY ILL PTS IN WHOM GLUCOSE UTILIZATION IS IMPAIRED, LARGE VOLUME INFUSIONS OF D5NS CAN RESULT IN CELLULAR DEHYDRATION AND EXCESS LACTATE PRODUCTION. COLLOID FLUIDS COLLOID FLUIDS HAVE LARGE SOLUTE MOLECULES THAT DON T READILY CROSS A SEMI-PERMEABLE MEMBRANE. THE MOLECULES IN A COLLOID SOLUTION CREATE AN OSMOTIC FORCE CALLED COLLOID OSMOTIC PRESSURE OR ONCOTIC PRESSURE WHICH HOLDS WATER IN THE VASCULAR COMPARTMENT. 5
COLLOID FLUIDS COLLOIDS HIGHER THE THE COLLOID ONCOTIC PRESSURE, GREATER THE INCREMENT IN PLASMA VOLUME RELATIVE TO THE INFUSATE VOLUME. FLUIDS WITH COLLOID ONCOTIC PRESSURE OF 20 TO 30 MMHG ARE CONSIDERED ISO- ONCOTIC FLUIDS. HYPERONCOTIC ALBUMIN SOLS HAVE BEEN ASSOCIATED WITH INCREASED RISK OF RENAL INJURY. DEXTRANS AND HETASTARCH HAS BEEN IMPLICATED IN RENAL INJURY. DEXTRANS PRODUCE A DOSE RELATED BLEEDING TENDENCY BY IMPAIRING PLATELET AGGREGATION AND DECREASE LEVELS OF FACTOR VIII AND VW FACTOR. COLLOID-CRYSTALLOID CONUNDRUM COST COMPARISION EARLY STUDIES SHOWED THE BENEFIT OF CRYSTALLOIDS FOR RESUSCITATION OF BLOOD LOSS. MORE RECENTLY COLLOIDS WERE FOUND TO BE BETTER IN IMPROVING CO AND SYSTEMIC OXYGEN DELIVERY. PRINCIPAL ARGUMENT IN FAVOR OF CRYSTALLOIDS IS THE LACK OF SURVIVAL BENEFIT WITH COLLOID RESUSCITATION AND THE LOWER COST OF CRYSTALLOID SOLUTIONS. 6