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FLUID AND ELECTROLYTE MANAGEMENT OF THE SURGICAL PATIENT

FLUID AND ELECTROLYTE MANAGEMENT OF THE SURGICAL PATIENT. Wei Yonggang Dept. Liver Surgery & Liver Transplantation. Management of fluids and electrolytes is an integral part of care of surgical patients, and it may be critical factor in certain patients.

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FLUID AND ELECTROLYTE MANAGEMENT OF THE SURGICAL PATIENT

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  1. FLUID AND ELECTROLYTE MANAGEMENT OF THE SURGICAL PATIENT Wei Yonggang Dept. Liver Surgery & Liver Transplantation

  2. Management of fluids and electrolytes is an integral part of care of surgical patients, and it may be critical factor in certain patients. Many diseases, injuries, and operative trauma have a great effect on the physiology of body fluids and electrolytes, a thorough understanding of the metabolic responses is essential to the care of surgical patient.

  3. Basic concepts

  4. Anatomy of Body Fluid Compartment • Total body water: Water constitutes between 50%-70% of total body weight • The average normal value is 60% of body weight for young adult males,50% for young adult females. A normal variation of ±15% applies to both groups • Extremely obese individual may have 25%-30% less body a lean individual of the same weight • In the newborn infant ,with a maximum of 75% to 80%;at 1 year of age, the total body water averages approximately 65% of body weight.

  5. Anatomy of Body Fluid Compartment • The water of body is divided into three functional compartments. • The fluid within the body’s diverse cell population, intracellular water ,represents between 30% and 40% of body weight. • The extra-cellular water represents approximately 20% of body weight and is divided between intravascular fluid, or plasma(5% of body weight), and interstitial, or extra-vascular, extra-cellular fluid(15% of body weight).

  6. Anatomy of Body Fluid Compartment • Intracellular Fluid: (ICF) • Measurement of intracellular fluid (ICF) is determined indirectly by subtraction of measured extra-cellular fluid (ECF) from the measured total body water. • 30%-40% of body weight • Chemical composition of ICF With potassium and magnesium the principal cations And phosphates and proteins the principal anions.

  7. Anatomy of Body Fluid Compartment • Extra-cellular Fluid (ECF) : • The total ECF volume represents approximately 20% of body weight. The ECF compartment has two major subdivisions. The plasma volume is approximately 5% of body weight in the normal adult. The interstitial, or extra-vascular, obtained by subtracting the plasma volume from the measured total ECF volume, accounts for approximately 15% of body weight.

  8. Anatomy of Body Fluid Compartment • The normal constituents of ECF : With sodium the principal cation And chloride and bicarbonate the principal anions

  9. Osmotic pressure • The differences in ionic composition between ICF and ECF are maintain by the cell wall, which function as a semi-permeable membrane • The total number of osmotically active particles is 290 to 310 mOsm in each compartment • The dissolved protein in the plasma are primarily responsible for effective osmotic pressure between the plasma and the interstitial fluid compartment ;this is frequently referred to as the colloid osmotic pressure • The effective osmotic pressure between ICF and ECF compartment is contributed to by sodium, which is the principal cation of ECF ,contributes a major portion of the osmotic pressure, and glucose and BUN.

  10. Osmotic pressure • Posm (mOsm/kg)=2[Na+(mmol/L)+K+(mmol/L)]+[blood urea nitrogen(mg/dl)/2.8]+[glucose(mg/dl)/18]

  11. Osmotic pressure • Since the cell membranes are completely permeable to water ,the effective osmotic pressure in the two compartment are considered equal. Any condition that alters the effective osmotic pressure in either compartment causes redistribution of water between the compartment. • Thus ,an increased in effective osmotic pressure in ECF, which would occur most frequently through increased sodium concentration ,causes a net transfer of water from the ICF to the ECF compartment. The transfer of water continues until the effective osmotic pressure in two compartments are equal.

  12. Classification of body fluid changes The disorder in fluid balance may be classified into three general categories: • Volume changes • Concentration changes • Composition changes

  13. Volume changes If an isotonic salt solution is added to or lost from the body fluids, only the volume of the ECF is changed. The acute loss of an isotonic extra-cellular solution ,such as intestinal juice, is followed by a significant decrease in ECF volume and little, if any, change in ICF volume. Fluid is not transferred from the intracellular space to refill the depleted extra-cellular space as long as the osmolality remains the same in two compartment. Volume changes: • Volume deficit; • Volume excess

  14. Volume deficit • ECF volume deficit is by far the most common fluid disorder in the surgical patient. • The loss of fluid is water and electrolytes in approximately the same proportion as that in which they exist in normal ECF.

  15. cause • The common disorders leading to an ECF volume deficit include losses of gastrointestinal fluid due to vomiting, naso-gastric suction, diarrhea, and fistula drainage. • Other causes include sequestration of fluid in soft tissue injuries and infections ,intra-abdominal and retroperitoneal inflammatory processes, peritonitis ,intestinal obstruction ,and burns.

  16. Signs and symptom • Central nervous system: • Moderate :sleepiness, apathy, slow responses, anorexia, cessation of usual activity. • Severe: decrease tendon, anesthesia of distal extremities, stupor, coma, • Gastrointestinal: • Moderate: Progressive decrease in food consumption • Severe: nausea, vomiting, refusal to eat, silent ileus and distention

  17. Signs and symptom • Cardiovascular • Moderate: orthostatic hypotension, tachycardia, collapsed veins, collapsed pulse • Severe: cutaneous lividity, hypotension, distant heart sounds, cold extremities, absent peripheral pulses • Tissue signs : • Moderate: soft, small tongue with longitudinal wrinking, decreased skin turgor • Severe: atonic muscles, sunken eyes • Metabolism: • M, mild decreased of temperature • S, marked decreased of temperature

  18. oliguria • pre-renal renal • Urine osmolality(mOmsm/kg.H2O) >500 <350 • Urine sodium (mEq/L) <20 >40 • BUN/serum creatinine >15 <10 • Urine /plasma urea >8 <3 • Urine /plasma creatinine >40 <20 • Renal failure index <1 >1.5 • RFI=urine Na/(U/P creatinine) • Fractional excretion sodium <1 >1.5 • FE Na=[(U/PNa)/(U/PCr)]*100

  19. Volume excess • ECF volume excess is generally iatrogenic or secondary to renal insufficiency. • Both the plasma and the interstitial fluid volume are increased • Healthy young, circulatory overload, primary in pulmonary circulation ;of excessive fluid in other tissue • Old patient, congestive heart failure with pulmonary edema may be develop rather quickly with a moderate volume excess.

  20. Signs and symptoms • Gastrointestinal : at operation, edema of stomach, colon, lesser and greater omenta and small bowel mesentery. Severe: vomiting, diarrhea • Cardiovascular: Moderate : elevated venous pressure, distention of peripheral veins, increase cardiac output, loud heart sounds, functional murmurs ,bounding pulse, high pulse pressure, increased pulmonary sound, gallop; Severe: pulmonary edema Tissue signs: • Moderate: subcutaneous pitting edema, basilar rales • Severe: anasarca, moist rales

  21. Concentration changes • If water along is added to or lost from the ECF, the concentration of osmotically active particles changes. • Sodium ions account for most of the osmotically active particles in ECF and generally reflect the tonicity of other body fluid compartment. • If ECF is depleted of sodium, water passes into the intracellular space until osmolality is again equal in the two compartment. • Concentrantion changes: causes? • 1)hypernatremia; • 2)hyponatremia

  22. Acute changes in Osmlar concentration Hypo-natremia: • Central nervous system: • Moderate: muscle twitching, hyperactive tendon reflexes, increased intracranial pressure (compensated phase) • Severe: convulsion, loss of reflexes, increased intracranial pressure (de-compensated phase) • Cardiovascular: changes in blood pressure and pulse secondary to increased intracranial pressure • Tissue signs: increased salivation, lacrimation ,water diarrhea, ‘fingerprinting’ of skin • Renal: oliguria progressing to anuria

  23. Acute changes in Osmlar concentration Hypernatremia: • Moderate: restlessness ,weakness, • Severe: delirum, maniacal behavior Cardiovascular : • Tachycardia, hypotension (if severe) • Tissue signs: decreased saliva and tears. dry and sticky mucous membranes,red swollen tongue, flushed skin • Renal: oliguria • Metabolic: fever

  24. Mixed volume and concentration abnormalities • ECF deficit and hyponatremia :this state is readily produced in a patient who continues to drink water which losing large volume of gastrointestinal fluid. It may also occur post-operatively when gastrointestin al losses are replaced with only 5%dextrose in water or a hypotonic sodium. • ECF volume deficit and hypernatremia: the loss of a large amount of hypotonic salt solution, such as an osmotic diuresis due to glucosuria in a hyperglycemic patient.

  25. Mixed volume and concentration abnormalities • ECF volume excess and hypernatremia: the prolonged administration of excessive quantities of sodium salt, this may also occur when pure water losses (such as insensible loss of water from the skin and lungs) are replaced with sodium-containing solution • ECF volume excess and hyponatremia: excessive administration of water or hypotonic salt solution to a patient with oliguric renal failure.

  26. Sodium abnormalities • physiology. The normal individual consumes 3-5g (4.5g)NaCl (50-90mmol/d,Na+) • Balance is maintained primarily by the kidneys • Normal Na+ concentration is 135-145 mmol/L • Potential sources of significant Na+ loss include sweat, urine, and GI secretions. • Na+ concentration largely determines the plasma osmolality (Posm) ,which can be approximated by the following equation: Posm (mOsm/kg)=2[Na+(mmol/L)+K+(mmol/L)]+[blood urea nitrogen(mg/dl)/2.8]+[glucose(mg/dl)/18]

  27. sodium • Normal Posm is 290-310 mOsm/L. • In general, hypotonicity or hypertonicity coincides with the presence of hyponatremia or hypernatremia. • However ,Na+ concentration and total body water are controlled by independent mechanism. As a consequence ,hyponatremia or hyponatremia may occur in the setting of hypovolemia, hypervolemia or euvolemia.

  28. hyponatremia • A. cause and diagnosis.hyponatremia may occur in the setting of hypertonicity,isotonicity, or hypotonicity. consequently, it is necessary to measure the serum osmlality to evaluate patients with hyponatremia. Isotonic hyponatremia. • hyperlipidemic and hyperproteinemic states result in an isotonic expansion of the circulating plasma volume and cause a decrease in serum Na+ concentration. • Isotonic ,sodium-free solution of glucose,mannitol ,and glycine are restricted intially to the extracellular fluid and may similarly result in transient hyponatremia.

  29. hyponatremia hypertonic hyponartremia hyperglycemia may result in transient fluid shift from the intracellular to the extracellular compartment,thus diluting the serum Na+concentration. • The expected decrease in serum Na+ is approximately 1.3-1.6mmol/L for each 100mg/dLincrease in blood glucose above 200md/dL. • rapid infusion of hypertonic solution of glucose mannitol ,or glycine may have a similar effect on Na+concentration

  30. hyponatremia hypotonic hyponatremia is classified on the basis of extracellular fluid volume . Hypotonic hyponatremia generally develops as a consequence of the administration and retention of hypotic fluids (e.g.,D5W,0.45%NaCl) and rarely from the loss of salt-containing fluids alone. • hypovolume hypotonic hyponatremia in the surgical patient most commonly results from replacement of sodium rich fluid losses(e.g.from the GI trate,skin,or lungs) with an insufficient volume of hypotonic fluid(e.g.,D5W,0.45%NaCl)

  31. hyponatremia • hypervolume hypotonic hyponatremia. the edematous states of congestive heart failure,liver disease,and nephrosis occur in the setting of inadeequate ciculating blood volume. • This serves as a stimulus for the renal retetion of sodium and of water. disproportionate accumlation of water results in hyponatremia • C) Isovolemic hypotonic hyponatremia • (1)water intoxication typiclly occurs in the patient who comsume larger quantities of water in the setting of mildly impaired renal function (primary polydipsia). Alternatively,it may be the result of administration of large quantities of hypotonic fluid in the patient with generalized renal failure.

  32. hyponatremia • (2)K+loss.either from GI fluid loss or secondary to diuretics, may result in isovolumic hyponatremia • (3)reset osmostat. Normally, the serum “osmostat” is set at 285mOsm/L. in some individuals ,the osmostat is “reset” downward, thus maintaining a lower serum osmolality. Several chronic disease (e.g., tuberculosis and cirrhosis) predispose to this condition. Patients thus affected respond normally to water loads with suppression of antidiuretic hormone (ADH) secretion and excretion of free water. In contrast to the syndrome of inappropriate ADH secretion (SIADH), the administration of exogenous water does not worsen the hyponatremia.

  33. hyponatremia clincal manifestations • Symptoms associated with hyponatremia are predominantly neurological and result from hypoosmolality. • A decrease in Posm causes intracellular water influx, increased intracellular volume and cerebral edema. • Symptoms include lethargy, confusion, nausea, vomiting, seizures, and coma.

  34. Hyponatremia-treatment • (1) isotonic and hypotonic hyponatremia correct with resolution of the underlying disorder. • (2)hypovolumic hyponatremia can be managed with administration of 0.9%NaCl to correct volume deficits and replace ongoing losses. • (3) water intoxication respond to fluid restriction (1000ml/day)

  35. Hyponatremia-treatment • hypervolumic hyponatremia may respond to water restriction (1000ml/day) to return Na+ to greater than 130mmol/L. • In the setting of severe congestive heart failure , optimizing cardiac performance (e.g., with nitrates or angiotensin-converting enzyme inhibitors) may assist in Na+ correction • If the edematous hyponatremic patient becomes symptomatic, plasma Na+ can increased to a safe level by the use of a loop diuretic(furosemide20-200mg i.v.Q6h.) while replacing urinary Na+ losses with 3% NaCl. Hypertonic saline should not be administrered to these patients without concomitant diuretic therapy

  36. Hyponatremia-treatment • The plasma Na+ should be increased by no more than 12mmol/L over the first 24 hours of treatment (i.e. Na+ <0.5mmol/h). • The patient’s volume status should be carefully monitored over this time, and the serum Na+ should be determined frequently (every 1-2 hours). • Once the serum Na+ concentration reaches 120mmol/L,administration of hypertonic saline can be discontinued. Water restriction(1000mL per day) should be continued until serum Na+ concentration normalizes.

  37. hypernatremia • A. diagnosis hypernatremia is uniformly hypertonic and typically the results of water loss in excess of solute . • Patient are categorized on the basis of their extracellular fluid volume state. 1.hypovolume hypernatremia 2.hypervolume hypernatremia 3.isovolume hypernatremia

  38. Hypernatremia-hypovolume • hypovolume hypernatremia. any net loss of hypotonic body fluid results in extracellar volume depletion and hypernatremia. • Common cause in surgical patient include diuresis as well as GI, respiratory (especially patient with who are breathing umhumidified air), cutaneous (particularly burn) fluid loss. • chronic renal failure and partial urinary tract obstruction also may cause hypovolemic hypernatremia.

  39. Hypernatremia-hyper and isovolume • hypervolume hypernatremia in the surgical patient is most commonly iatrogenic and results from the paraenteral administration of hypertonic solution(e.g.,NaHCO3,saline,medications,nutrition). • isovolumic hypernatremia Inappropriate use of isotonic fluid in patients with net water loss is the common cause of isovolumic hypernatremia in the hospitalized surgical patient.

  40. Hypernatremia- clinical manifestations • Symptoms of hypernatremia are primarily neur-ologic and include lethargy, weakness, and irritability .Initially, these may progress to fasciculation, seizures, coma ,and irreversible neurologic damage • water deficit associated with hypernatremia can be estimated: • Water deficit (L)= 0.60 * total body weight (kg) * [(serum Na+ [mmol/L ]/140)-1]

  41. hypernatremia • Rapid correction of hypernatremia can result in cecebral over-hydration and permanent neurologic damage. (risk of myelinolysis) • Consequently ,only one half of the water deficit should be corrected over the first 24 hours, with the remainder corrected over the following 2-3 day. • Serial Na+ determinations are necessary to ensure that the rate of correction is adeqaute but excessive. • Oral fluid intake is acceptable for replacing water deficits. • If oral fluid intake is not possible,D5Wor D5/0.45%NaCl can be substituted. • In addition to the actual water deficit, insensible losses and urinary output must be replaced.

  42. potassium • K+ is the major intracellar cation ,with only 2%(60-80mEq)of total body(3000-4000mEq;35-55mEq/kg body weight) K+ located in the extracellular space. • Normal serum concentration is 3.5-5.3mmol/L . • Approximately 50-100mmol K+ is ingested and absorbed daily • Ninely percent of K+ is renally excreted, with the remainder eliminated in stools.

  43. Potassium abnormalities • Total extracellular potassium : • (70kg:4.5mEq/L*14L) • Hyper-kalemia:>5.5mmol/L; • Hypo-kalemia:<3.5mmol/L. • Normal plasma potassium:3.5-5.5mmol/L

  44. hyperkalemia • cause and diagnosis • Hyperkalemia may occur with normal or elevated stores of total body K+. • Pseudo-hyperkalemia is a laboratory abnormality that reflects K+ release from leukocytes and platelets during coagulation • Abnormal redistribution of K+ from the intracellular to the extracellular compartment may be occur as the result of insulin deficency,beta-adrenergic receptor blockade, acute acidemia, rhabdomyolysis, cell lysis (after chemotherapy), digitalis intoxication, reperfusion of ischemic limbs 、organs

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