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FLUID THERAPY

Body Fluid CompartmentsTotal Body water is:

60% of total body weight in males55% of total body weight in females

The lower TBW content in females is due to the higher proportion of body fat.Highest TBW is at birth and gradually decreases with age.

Body Fluid Compartments70Kg Man

Solids(40%)

Water(60%)42 Litres

ECF 14 LitresICF 28 Litres

Interstitial fluid 11 LitresPlasma 3 Litres

Blood volume or intravascular compartment = ECF (plasma) + ICF (RBC water)

Body fluid compartments

Daily Input Vs OutputInput2500mlOutput2500mlFluids 1400mlFood 750mlMetabolism 350mlWaterUrine 1500ml

Skin 500mlLungs 400mlFaeces 100mlNa 1-1.5mmol/kg/dayK 0.8 - 1 mmol/kg/day

Insensible losses1000ml

Where does the body get its fluid from?Input should = OutputCellular respiration: C6H12O6 (aq) + 6 O2 (g) 6 CO2 (g) + 6 H2O (l)

Electrolyte Composition of fluid Compartments

When you take a blood sample you are measuring the plasma levels of cations and anions. K/Mg/PO4/Proteins are predominantly intracellular whilst Na/Ca/Cl/HCO3 are extracellular.

Osmotic pressure of blood plasma 285 + 5 mOsm / L. Solution with same osmotic pressure (isotonic) = 0.96% NaCl, D51/4NS, RLLower (hypotonic)= D5W, NSHigher (hypertonic)= D5NS, D5NS, D5LR, etc.

Electrolyte content in body

(mEq/l)PlasmaInterstitialInterselulerKationNaKCaMg14245311442,51,515150227Total154152194AnionClHCO3HPO4SO4Asam organicProtein103272151611430215011010020063Total154152194

Function of Natrium Maintaining osmotic pressure and extracellular fluid volume.Needs of 50-100 mEq per day or 3-6 grBalance is set primarily by the kidneys1 gram = 17 mEq NaCl

Deficiency is usually due to excessive infusion without Na, prostate resection syndrome, decreased secretion of ADH

Function of KaliumMost found in the cells (150 MEQ / L)

Plasma potassium in only 2% of total body K, so the lack rarely detected

Useful to stimulate the muscles, sending electrical impulses, helping O2 utilization, amino acids, glycogen, & cell formation

Normal serum K rate 3-5 meq / L

Hypokalemia (1020% of their blood volume.

The most severe transfusion reactions ABO incompatibility; result in intravascular hemolysis. Acute hemolytic reaction : rise in temperature, unexplained tachycardia, hypotension, hemoglobinuria, and diffuse oozing in the surgical field.

Transfusion of leukocyte-containing blood products appears to be immunosuppressive. Immunocompromised and immunosuppressed patients are particularly susceptible to severe cytomegalovirus (CMV) infections through transfusions.

The most consistent acidbase abnormality after massive blood transfusion is postoperative metabolic alkalosis.The most common cause of bleeding following massive blood transfusion is dilutional thrombocytopenia.

Signs of Fluid Loss (Hypovolemia)Fluid Loss (Expressed as Percentage of Body Weight)SIGN5%10%15%Mucous membranesDryVery dryParched SensoriumNormalLethargicObtunded

Orthostatic changesNonePresentMarkedIn heart rate> 15 bpm In blood pressure> 10 mm Hg Urinary flow rateMildly decreasedDecreasedMarkedly decreased

Pulse rateNormal or increasedIncreased > 100 bpmMarkedly increased > 120 bpm

Blood pressureNormalMildly decreased with respiratory variationDecreased

Presentation of dehydrationSeverity of DehydrationClinical FindingsMildUp to 5% total body water(3L in 70kg man)Normal mental stateDry mucous membranesUsually thirstyBlood pressure & heart rate normalLower than normal urine outputSkin turgor almost normalModerate5-10% total body water(5L in 70kg man)Disinterest in surroundings, can be drowsyIncreased heart rate & respiratory rateOrthostatic hypotensionDecreased skin turgorReduced urine outputSevere10-15% total body water(8L in 70kg man)Reduced conscious levelFast heart rateLow blood pressureRespiratory distressOliguria / anuria

Dehydration can be either isotonic dehydration (Na levels and normal serum osmolarity);hypotonic / hiponatremik (Na 295 mOsm / L).

Classification of shock

IV fluid types

Crystalloids

ColloidsSyntheticHuman

Basis of IV fluid therapyMaintenanceTo supply daily needsReplacementTo replace on-going losses ResuscitationTo correct an intravascular or extracellular deficit

Crystalloid

A substance in solution that can diffuse through a semipermeable membranethe initial resuscitation fluid hemorrhagic and septic shock, burn, head injury to maintain cerebral perfusion pressure, and in patients undergoing plasmapheresis and hepatic resection

Electrolyte-containing solutions that are formulated to match to a greater or lesser extent the biochemical & osmotic features of the plasmaThey do not contain high molecular weight compounds

For losses primarily involving water, replacement is with hypotonic solutions, also called maintenance-type solutions. If losses involve both water and electrolytes, replacement is with isotonic electrolyte solutions, also called replacement-type solutions. Glucose is provided in some solutions to maintain tonicity or to prevent ketosis and hypoglycemia due to fasting.

Because most intraoperative fluid losses are isotonic, replacement-type solutions are generally used. The most commonly used fluid is lactated Ringer's solution.

Crystalloids Examples0.9% Saline (Normal saline)Hartmanns (compound sodium lactate)Glucose containing solutions5% Glucose10% GlucoseDextrose-saline4% glucose & 0.18% saline5% glucose & 0.45% saline

Hartmanns lactate is metabolised to bicarbonate by the liver (similar but not the same as Ringers Lactate)

Crystalloids compositionSolutionNaClKCaBicarbGlucoseg/LTonicitymmol/l0.9% Sodium Chloride154154----IsotonicHartmanns1311115229(as lactate)-Isotonic5% Dextrose-----50Isotonic(hypotonic once metabolised)10% Dextrose-----100Hypertonic(hypotonic once metabolised)4% glucose & 0.18% sodium chloride3030---40Isotonic

Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane (isotonic solutions have equal osmotic pressures). Saline pH 5; Hartmanns pH 6.5

ColloidsSolutions that contain high molecular weight proteins as well as electrolytes

Unable to diffuse through normal capillary membranes

ColloidsExamples

Gelatin-basedGelofusineHaemaccel

Hydroxyethyl starches (HES)Pentastarch5% - Hemohes10% - HAES-steril

Tetrastarch - 6% (HES) VoluvenVolulyte

Dextran 70Rescuflow

Human albumin solutionsHAS 5%HAS 20%

50ml/kg/24hr(3.5l)

Max 1.5 L / 24hrMax 2.5 L/ 24hr

Use in trauma, (Max 1L)250ml followed by isotonic fluidsSevere allergic reactions, coagulation effects

Colloid compositionSolutionNaClKMgHCO3MW

Daltonsmmol/lGelofusine1541200.40.4-30,000Voluven 6%154154---130,000Volulyte 6%13711041.534(as acetate)130,000

Gelofusine pH 7.4; Voluven 6% - pH 4.0 5.5; Volulyte 6% - pH 5.7 6.5

Distribution of IV fluids

5% Dextrose0.9% SalineColloid

Perioperative Fluid Therapy

includes replacement of preexisting fluid deficits, of normal losses (maintenance requirements), and of surgical wound losses including blood loss.

Normal Maintenance Requirements

Example: What are the maintenance fluid requirements for a 25-kg child ?Answer: 40 + 20 + 5 = 65 mL/h.

WeightRate

For the first 10 kg4 mL/kg/h

For the next 1020 kgAdd 2 mL/kg/h

For each kg above 20 kgAdd 1 mL/kg/h

Preexisting DeficitsPatients presenting for surgery after an overnight fast without any fluid intake will have a preexisting deficit proportionate to the duration of the fast. The deficit can be estimated by multiplying the normal maintenance rate by the length of the fast.

For the average 70-kg person fasting for 8 h, this amounts to (40 + 20 + 50) mL/h x 8 h, or 880 mL.

Surgical Fluid Losses

Surgical Fluid LossesBlood LossOther Fluid Losses

Intraoperative Fluid ReplacementReplacing Blood LossIdeally, blood loss should be replaced with crystalloid or colloid solutions to maintain intravascular volume (normovolemia) until the danger of anemia outweighs the risks of transfusion. further blood loss transfusions of red blood cells to maintain hemoglobin concentration (or hematocrit). For most patients, that point corresponds to a hemoglobin between 7 and 8 g/dL (or a hematocrit of 2124%).

Patients with a normal hematocrit should generally be transfused only after losses greater than 1020% of their blood volume.

The amount of blood loss necessary for the hematocrit to fall to 30% can be calculated as follows:1. Estimate blood volume. 2. Estimate the red blood cell volume (RBCV) at the preoperative hematocrit (RBCVpreop). 3. Estimate RBCV at a hematocrit of 30% (RBCV30%), assuming normal blood volume is maintained. 4. Calculate the red cell volume lost when the hematocrit is 30%; RBCVlost = RBCVpreop RBCV30%. 5. Allowable blood loss = RBCVlost x 3.

Estimate blood volumeAverage Blood VolumesAgeBlood Volume

Neonates Premature Full-term95 mL/kg85 mL/kgInfants80 mL/kgAdults Men Women75 mL/kg65 mL/kg

ExampleAn 85-kg woman has a preoperative hematocrit of 35%. How much blood loss will decrease her hematocrit to 30%?Estimated blood volume = 65 mL/kg x 85 kg = 5525 mL. RBCV35% = 5525 x 35% = 1934 mL. RBCV30% = 5525 x 30% = 1658 mL. Red cell loss at 30% = 1934 1658 = 276 mL. Allowable blood loss = 3 x 276 mL = 828 mL.

Therefore, transfusion should be considered only when this patient's blood loss exceeds 800 mL. Transfusions are not recommended until the hematocrit decreases to 24% (hemoglobin < 8.0 g/dL)

Other useful guidelines 1U of red blood cells will hemoglobin 1 g/dL and the hematocrit 23% (in adults); 10-mL/kg transfusion of red blood cells will hemoglobin concentration by 3 g/dL and the hematocrit by 10%.

Replacing Redistributive & Evaporative Losses

Redistribution and Evaporative Surgical Fluid LossesDegree of Tissue TraumaAdditional Fluid Requirement

Minimal (eg, herniorrhaphy)02 mL/kg

Moderate (eg, cholecystectomy)24 mL/kg

Severe (eg, bowel resection)48 mL/kg

Intraoperative Transfusion PracticesPacked Red Blood Cellsideal for patients requiring red cells but not volume replacement (eg, anemic patients in compensated congestive heart failure). Surgical patients require volume as well as red blood cells crystalloid can be infused simultaneously through a second intravenous line for volume replacement.

Fresh Frozen Plasma (FFP) contains all plasma proteins, including all clotting factors. indicated in the treatment of isolated factor deficiencies, the reversal of warfarin therapy, and the correction of coagulopathy associated with liver disease. Each unit of FFP generally increases the level of each clotting factor by 23% in adults. The initial therapeutic dose is usually 1015 mL/kg. The goal is to achieve 30% of the normal coagulation factor concentration.may also be used received massive blood transfusions and continue to bleed following platelet transfusions, antithrombin III deficiency/thrombotic thrombocytopenic purpura.Each unit of FFP carries the same infectious risk as a unit of whole blood.

Plateletsshould be given to patients with thrombocytopenia / dysfunctional platelets in the presence of bleeding. Prophylactic platelet transfusions platelet counts