Fluid and Electrolyte Management

FLUIDS ELECTROLYTES AND TOTAL PARENTERAL NUTRITION

FLUID AND ELECTROLYTE MANAGEMENT IN SURGICAL PATIENTSDATE : 11 OCT 2013INTRODUCTION: Fluids and electrolyte management are paramount to the care of the surgical patients.Review of the normal physiology of body fluids, electrolyte composition & concentration abnormalities and treatments.Changes in both fluid volume and electrolytes occur pre, intra and postoperatively.Review of principles of fluid therapy in surgical patients. BODY FLUIDSTOTAL BODY WATER :Water constitutes approximately 50 to 60% of total body weight.Lean tissues such as muscle and solid organs have higher water content than bone and fat.TBW is more in males compared to females due to higher percentage of adipose tissue in females.The highest percentage of TBW is found in newborns approx 85% of their total body weight. This decreases to about 65%by 1 yr and thereafter remains fairly constant.TBW is calculated using formula: TBW= 0.6*Kg Body weight.

TBW PERCENTAGE

FLUID COMPARTMAENTSTBW is divided into two functional compartments, EXTRACELLULAR AND INTRACELLULAR.Extracellular fluid compartment comprises about one third of the TBW and the intracellular compartment remaining two thirds.Extracellular compartment comprises 20% of body weight and is divided between plasma(5% of body weight) and interstitial fluid (15% of body weight).TBW DISTRIBUTION

COMPOSITION OF FLUID COMPARTMENTSThe extracellular fluid compartment is balanced between the principle cation sodium and anions chloride and bicarbonate.The intracellular compartment is comprised primarily of cations potassium and magnesium and anions , phosphate and proteins.

COMPOSITION OF FLUID COMPARTMENTSSodium is confined to ECF and because of its osmotic and electrical properties it remains associated with water. Therefore, sodium containing fluids are distributed through out the ECF.While the administration of sodium containing fluids will expand the intravascular volume, it also expands the interstitial space by approx 3 times as much as the plasma

CLASSIFICATION OF BODY FLUID CHANGESThe normal person consumes an average of 2000ml of water per day, approx 75% from oral intake and rest is extracted from solid foods.Daily water losses include about 1L in urine, 250ml in stool, and 600ml as insensible losses.Insensible losses occur through both the skin(75%) and lungs (25%).Insensible losses can be increased by such factors as fever, hyper metabolism and hyperventilation.CLASSIFICATION OF BODY FLUID CHANGESSweating is an active process and involves loss of electrolytes and water .To clear the products of metabolism, the kidneys must excrete a minimum of 500 800ml of urine per day regardless of amount of oral intake.

Electrolyte composition

OSMOTIC PRESSUREThe movement of water across the cell membrane depends upon osmosisOsmotic pressure is measured in terms of osmoles, that refers the actual number of osmotically active particles.Normal osmolality of TBW is 280-300 mosm.Calculated serum osmolality = 2[Na] + [Glucose] / 18 + [BUN]/2.8

Sodium Normal Na levels of plasma is 135-145meq per L.Of the 4200 mmol of Na in a healthy adult male only 2.4% is intracellular and 70% of it is exchangeable.A normal person consumes 3 5 g of salt per day, with the balance maintained by the kidneys .With hyponatremia, sodium excretion can be reduced to as little as 1 mEq/d or maximized up to 5000 mEq/d to achieve balance in lieu of salt wasting kidneys.HyponatremiaDefined as serum Na level 160 altered consciousnessNormal renal response generate hyperosmolar urine and retain water .. Endocrine failure Severe hypernatremia rare in conscious patients ( compelled to drink).. Delirium tremens

19Clinical Features Symptoms of hypernatremia are mainly neurological includes lethargy, weakness , irritability may progress to fasciculations, seizures, coma, and, irreversible neurologic damage.

Nephrogenic DI inability of kidney to respond to ADHHot and aridGeratric patients20TreatmentWater deficit associated with hypernatremia should be corrected One half of the water deficit should be corrected over 24 hrs and remainder been corrected over the following 2-3 days. D5W or D5NS or 0.45% NaCl can be used.Rapid correction of hypernatremia leads to cerebral edema and permanent neurological damage.Water used to treat.. Isotonic NS.. Should be 3 mmol/l , 98% intracellularIf aldosterone increases, potassium concn increases22HypokalemiaDefined as serum K level 5.5mmols /L Caused by excessive K uptake, blood transfusions, GI haemorrhage, crush injuries, hemolysis, renal failure, K sparing diuretics Clinical features include GI , neuromuscular and cardiovascular.GI symptoms include nausea,vomiting, intestinal colic and diarrhoea.Neuromuscular symptoms range from weakness to ascending paralysis to respiratory failure.HyperkalemiaCVS manifestations range from ECG changes to arrhythmias to arrest.ECG changes peaked T waves , flattened P waves , prolonged PR interval, widened QRS complex and ventricular fibrillation.TreatmentSevere hyperkalemia requires emergent treatment directed at minimising membrane depolarisation shifting K into cells and promoting K loss.Administration of Ca gluconate, decreases membrane excitability . The usual dose is 10ml of 10% solution infused over 2-3 mins. And the dose can be repeated if there is no change in ECG after 5-10 mins.Insulin causes K shift into the cells, a commonly recommended combination is 10-20U in 25-50gms of glucose.

Severe : ca gluconate, nahco3 50-100 meq over 15 min50 ml 50 dGlucose,10 u insulin ; hemodialysisK bind, loop diuretics28TreatmentAlkali therapy with IV Na HCO3 can also shift K into cells.Beta adrenergic agonists promote cellular uptake of K.Removal of K can be achieved using diuretics, cation exchange resins or dialysis.Calcium AbnormalitiesSerum calcium is distributed mainly in 3 forms- protein bound[40%], complexed to phosphate 10%, ionized 50%.It is the ionized fraction that is responsible for neuromuscular stability.For measuring total serum calcium level, the albumin concentration must be taken into consideration.Adjust total serum Ca down by 0.8mg/dL for every 1 gm /dL decrease in albuminCoagulation cascade, 8.5 10.5PTH, Vit D, calcitonin30HypocalcemiaDefined as serum Ca level might below 8.5mEq/L.Causes of hypocalcemia include pancreatitis, massive soft tissue infections such as necrotizing fasciitis, renal failure, small bowel and pancreatic fistulae, hypoparathyroidism, toxic shock syndrome, malignancies associated with osteoclastic activity such as breast cancer, massive blood transfusions, CKDTumor lysis, ICU Severe pancreatitis ca links to peripancreatic fat in inflammatory phlegmon31Clinical FeaturesThey are mainly neuromuscular and cardiac.Paraesthesia of the face and extremities, muscle cramps, carpopedal spasm, stridor, tetany, and seizures.Positive Chvosteks sign and Trousseaus sign.Decreased cardiac contractibility and heart failure, heart blocks, ventricular fibrillations,. Muscle spasm,

32TreatmentSymptoms such as overt tetany, laryngeal spasm, seizures are indications of parenteral therapy .Approx. 200 mg of elemental Ca is needed to abort an attack of tetany.Initial therapy consists in the administration of ca bolus[10-20ml of 10%ca gluconate over 10 min] followed by 1-2 mg/kg elemental Ca.Oral therapy:1250 mgs of ca carbonate and 1000mg tab of ca gluconate are available.Cacl2 272 ca gluconate 90Caustic so slow correction, thru CVC 33HypercalcemiaDefined as calcium level > 10.5 meq/L.Caused by malignancy, hyperparathyroidism,vitamin D intoxication, immobilization, long term parenteral nutrition, thiazide diuretics.

Adenoma > hyperplasia, sudden immobilityMultiple myeloma, lymphoma, endocrine publek, drugs vit a vit d, thiazides,>17 hyper Ca crisis

34Clinical FeaturesAltered mental status,diffuse weakness, dehydration, adynamic ileus, nausea, vomiting, and severe constipation.Cardiac effects of hypercalcemia include QT shortening and arrhythmiasSevere > 15Stupor CNS dysfnpolyuria

35TreatmentMild hypercalcemia can be managed conservatively by restricting Ca intake and treating underlying disoder. severe hypercalcemia requires 1) NaCl 0.9% and loop diuretics 2) salmon calcitonin is used in hypercalcemia associated with malignancy and primary hyperparathyroidism. 3) pamidronate disodium 4) plicamycimPTHRP 8 0f 13AACorrection of primary problem.. Etidronate decrease osteoclast mediated ca release from boneCalcitonin tachyphylaxis, EDTA and chelators like phosphate salt36ChlorideIn a 70 kg healthy male there are approximately 2300 mmol of chloride.Of this approx. 70% is exchangeable and most is contained within plasma, interstitial fluid and lymph.Hence chloride is used as an index of ECF volume. Magnesium & ZincMg has an important role in functioning of enzyme systems and depletion of Mg manifests with signs of CNS and neuromuscular excitability.Zinc appears to have an important role in wound healing.

Increased Mg antacids, blocks ca shift into myocardiumDecreased Mg diarrhea, loop diuretics, alcohol, diabetic glycosuriaTreatment iv mgso4 and mg containing iv fluids 38ACIDBASE DISORDERSCLINICAL TERMINOLOGYCRITERIANormal pH7.4AcidosisPH < 7.35AlkalosisPH > 7.45Normal HCO324 (22-26) mEq/LMetabolic acidosisHCO3 26 mEq/L & high pH

Normal PaCO240 (35-45) mm of HgRespiratory acidosisPaCO2 >45 & low pH Respiratory alkalosisPaCO2 30.Anticoagulant effect of heparin is enhanced by dextran.Dehydrated patient.Dextran Regimen for thromboembolism: Day 1 : 500-1000ml over 4-6 hrs. Day 2 : 500ml over 4-6 hrs Upto 10 days : 500ml over 4-6 hrs on alternate daysHE STARCHSynthetic colloid available as 6% solution.Expands circulatory volume like albumin and dextran.Osmolarity 300 mOsm/LAdvantageNonantigenicDoes not interfere with blood grouping and matching.Less expensivePlasma volume expansion is greater than 5% albumin.Volume expansion lasts longer .DisadvantagesIncreases serum amylase concentration.No oxygen carrying capacity.Anaphylactic reactions

FLUID THERAPY SUMMARY1. Isotonic saline: best agent to treat shock and salt depletion.2. 5% Dextrose: provides fluids & calories without electrolytes, best agent to correct intracellular dehydration.3. DNS: suitable to treat salt depletion with calorie supply.4. RL: most physiological, glucose free fuid used in diarrhoea, diabetic, surgical and burns patients.5. Isolyte-M: best agent to provide potassium.6. Isolyte-G: only fluid to correct metabolic alkalosis.7. Isolyte-P: provides less electrolytes and more water, used chiefly in children.

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