Fluid and Electrolyte General Surgery Review Course.

Electrolyte Disturbances

Fluid & Electrolytes Imbalance Ali Hallal, MD, FRCS

Assistant Professor of Clinical SurgeryAUBMC1Fluids and Electrolytes ImbalanceCommon to all medal services.Frequently encounteredChanges in both occur (pre intra and post op) as well as in trauma and sepsisCan be difficult to treat.Needs monitoring and close follow up.Life threatening when severe.2Total Body Water: Weight /relationshipLean tissues and muscle and solid organ have the highest content of water. Lower content of water in female as opposed to male

The relation ship of total body water and weight is constant and is reflective of body fat. The higher the body fat the lower the proportion of body water. Lean tissue such as muscle ans solid organ have the highest water content when compared to fat and bone. There is lower percentage in femlae which correlate with a higher adipose tissue when compared to males. ECF is measured using the indicator dilution technique

3Functional Body Fluid Compartments.Total Body Water =TBW% TBWVolume of TBWMale (70 Kg) (60%) mlFemale (60 Kg) (50%)mlPlasma 5%Plasma35002500Interstitial Fluid 15%Interstitial105007500Extracellular ECF1400010000Intracellular Volume 40%

Intracellular280002000042000300008%4Body weight %Total Body Water %Total60100Intracellular4067Extracellular2033Intravascular58Interstitial1525Transcellular24Chemical Composition of Body Fluid Compartments200 mEq/L200 mEq/LCationsAnions153 mEq/L153 mEq/L153 mEq/L153 mEq/LK+150HPO43- 150Cations

Anions

CationsAnionsSO42-Na+142Cl-103Na+144Cl-114 HCO3-27SO42-3HCO3-30HCO3-10PO43-K+4SO42-3K+4PO43-Ca2+5Organic acids4Ca2+

3Organic acids5Mg2+

40Protein40Mg2+3Protein16Mg2+2Protein1Na+10PlasmaECFInterstitial FluidIntracellular FluidNa/KPumpThe ECF is balanced between Na the principal cation and Cl and Hco3 the principal anion . The intracellular compartment on the other hand is composed of K as the principal cation as well as Mg++ while the principal anions are hpo4-- and so4-- and the anion proteins . The concentration between the ECF and ICF is maintained by na/k atp pump. The composition of the interstitial space and the plasma differs slightly in ionic composition. You can note that the protein concentration is higher in the plasma which is a neccessity to maintain oncotic pressure. Although the movement of ions and protein between differnt compartment is restricted the movement of h2o is not and water diffuse freely between compartments. Clinical implication is that if you add water to plasma then only 8% will stay in the intravascular space and the reest will diffuse to the other compartments. That is why when we need to increase the intravascular volume an isotonic solution or hypertonic solution is added. Na however is confined to the ECF and because of its osmotic and electrical properties it remains associated with water.therefore Na containing fluid are distributed throughout the ECF and add to the volume of both intravascular and intersititial spaces. The ration in normal subject is 1:3 However what you need to know is that the addition of Na expand the interstitiumby a factor of 3 and intravascular6Osmotic Activity of Body FluidsOsmotic activity = the molar concentration of the substance by the number of particles into which it can freely dissociate in water . One mole of NaCl dissociate into Na + Cl and produce 2 Osm. The movement of water across cell membrane depends primarily on osmosisPosm=2xNa + Glucose/18 + Bun/2.8The osmolality of intracellular and extracellular fluids is maintained between 290 and 310 mOsm

Free water added to the ECF will initially expand ECF then redistribute. Similarly loss of water from ECF leads to shift of water from the intracellular to the ECF. 7Normal Exchange of Fluid and ElectrolytesThe healthy person consumes 2000 ml of H2O/ day (75% liquid, 25% solid)Daily water loss (1200 urine, 250 stool 600 insensible loss) Insensible loss occurs through skin (75%) and the lungs (25%)To clear the products of metabolism the kidney must excrete 500-800 ml/ day

Adding NS to ECF will have little effect on ICF but will expand ECF volumeAdding H2O will to ECF will casue water to shift between ECF and ICF and thus changing the concentration of electrolytes in compartmentsAdding K+ will affect neither volume nor concentration of other solute but will have major effect on myocardial functionAlthough each of these may occur simultaneously each is a separate entity with unique mechanism. Isotonic gain or loss results in extracellular volume change with little change in ICF. If free water is added or lost from the ecf water will pas between ecf and icf. Unlike na the concentration of other ion in the ecf can be altered without any change in the total numbe rof osmoticaaly active particles producing only compositional changes. For example doubling the potassium concentration will profoundely alter MI function without significantly altering volume or concentration of the fluid spaces. 9Disturbance in fluid balanceECF volume deficit is the most common fluid disorder in surgical patients. Signs and symptoms varies Extent of volume gain or lossGrade of shock Acute v/s chronic losses Cardiovascular neurologicalSkin turgor , sunken eyes etc Extreme of ages. Signs & Symptoms of Volume DisturbancesSystemVolume deficitVolume gainGeneralizedWeight lossWeight gainDecrease skin turgorPeripheral edemaCardiacTachycardiaIncreased COOrthostasisIncreased CVPCollapsed Neck VeinDistended Neck VeinMurmurRenalOliguriaAzotemia, urine Na < 20meQ/ LUrine Osm > Plasma OsmGIIleusBowel edemaPulmonaryCongestionCauses of volume excess IatrogenicRenal DysfunctionCongestive heart failureCirrhosis

Signs of Extracellular Fluid Volume Depletion10% ECF: 2% wt loss, thirst, U/O less, Hct mild increase.20% ECF: 4% wt loss, drowsiness, dry mucous membranes, HR high, orthostatic hypotension, oliguria 10:113Signs of Extracellular Fluid Volume Depletion30% ECF: Extreme findings:-6% wt loss-stupor or comapale, cyanotic, cooleyes sunkenpulse rapid, weak, hypotension-oliguria advanced: 65 yVascular volumePostural hypo, HR,pulse, CVP,oliguriaAll affectedInterstitial volumeDry skin, MM, tongue,eyesAll affectedmiscellaneousLess DTR, drowsy, ileus anorexia, coma Infection,drugs depression, hypothyroidMINIMAL CHANGE IN OSMOLALITY WILL CAUSE A DRIVE IN THIRST AND DIURESIS WATER RETENTION. 16Causes of volume deficit in surgical patients NG LossesVomittingDiarrheaEnterocutaneous Fistula Sequestration Soft tissue injuriesBurnsPeritonitisObstructionPostoperative bleeding concentration changes 17Composition of Body FluidsVolume/24hrs [Na+][K+][Cl-][HCO3-]Plasma135-1503.5-598-10622-30Stomach1000-200010-1504-12120-1600Bile300-800120-1703-1280-12030-40Pancreas600-800135-1503.5-560-10035-110S.Intestine2000-300080-1502-870-13020-40Colon50-10010-3080-12025-30Perspiration30-50530-500Diarrhea25-13010-6020-9020-50Fluid and Electrolytes Daily MaintenanceCalculated by Surface area

fluid1500mL/m2sodium50-75mEq/m2potassium50mEq/m2chloride50-75mEq/m2Calculated by body weightChildren1st 10kg:100mL/kg2d 10kg:50mL/kg>20kg: 20mL/kgAdults25-55yr:35mL/kg55-65yr:30mL/kg>65yr:25mL/kgSodium1.0-1.5 mEq/kgPotassium0.5-0.75mEq/kgChloride1.0-1.5mEq/kgElectrolyte Composition (mEq/L)SolutionNaClKHCO3-CaMgmOsmECF14210342753280-310LR13010942852730.9% NaCl154154308D5 0.45% NaCl7777407D5W002533% NaCl513513102621Osmolality / TonicityOsmolalityThe concentration of osmotically active particles in SolutionPermeant solute that can freely cross across cell membranePermeant solute contribute to osmolality but they do not contribute to tonicityUrea,ethanolTonicityEffect of the particle on cell VolumeImpermeant solute that cannot freely cross cell membranesImpermeant solute contribute to oncotic pressure across cell membrane as well as alteration in cell volumeNaEthanol and urea distribute equally across cell membrane 22Both impermeant and permeant solute can contribute to hyperosmolar or hyoposmolar state. However hypososmolar states are always accompanied by hypotonicity, whereas hypersomolar state are not always associated with hypertonicity Osmolality / TonicityUREAPseudohyponatremia 2ry to hyperglycemia from DMHyponatremia 26SodiumNa+ is main cation of ECFAlways coupled to waterNormal serum [Na+] = 135 145 mEq/L27Hyponatremia can result form direct sodium loss or from dilution by excessive water inteake under hypovolemic, euvolemic or hypervolemic condition.Frequently seen in postoperative because of increase ADH secretion(usually self limited) .SIADH is bit difffernet as there is abnormal secretion of AHD (Na goes below 130 . Hyponatremia occurs in euvolemic and hypervolemic, . The patient will have low serum osmolallity low na. High urine osmolality beciuse of High urinary na excretion in low urine volume. It is ususaly treated with diuretic and water restriction and sometime V2 (vasopressin ) antagonists. 28Hyponatremia - CausesCommon surgical causes includeIatrogenic SIADH: closed head injury(CHI), post craniotomy, post bleedingGI obstructionGI fistulaeAcute gastric dilatationSevere protracted diarrheaAcute pancreatitis. Peritonitis.Pleural effusion

R/O hypothyroidism and adrenal insufficiency,since they mimic SIADHmost commonPREVENTABLE

29Symptoms and SignsDependent on the degree (120)and the rapidity of Hyponatremia . Clinical manifestations primarily have a central nervous system origin and a re related to water intoxication and associated increase in ICP Differentiating the cause of hyponatremia can be difficultExclude hyperosmolar hyponatremia (hyperglycemia, mannitol contrast agent) , pseudohyponatremia.Make a decision Low VolumeHigh volumeLow VolumeGI losses(Urine Na < 20 mEq/L)Renal Losses(Urine Na > 20 mEq/ L) High volume SIADH

Hyponatremia can result form direct sodium loss or from dilution by excessive water inteake under hypovolemic, euvolemic or hypervolemic condition.Frequently seen in postoperative because of increase ADH secretion(usually self limited) .SIADH is bit difffernet as there is abnormal secretion of AHD (Na goes below 130 . Hyponatremia occurs in euvolemic and hypervolemic, . The patient will have low serum osmolallity low na. High urine osmolality beciuse of High urinary na excretion in low urine volume. It is ususaly treated with diuretic and water restriction and sometime V2 (vasopressin ) antagonists. 31Hyponatremia correction Na should not exceed 8-12 mEq / day (actual Na 120; then maximum correction till 132)The rate of correction should be 0.5-1 mEq/L(body weight)/hourNa required= (desired Na-actual Na ) x TBW Choose the correcting Solution and calculate the corresponding volume for the Na required. Administer either based on rate if symptomatic or based maximal allowed correction

Na =120Correct to Na=13070 Kg male ; TBW =42 LNa that need to added =42 x10 meQ =4203% solution 513 meQ Na/liter420/513 = 818 cc of 35 NaCl / 24 hrs 818 cc / 24 = 34 cc / hour The rate allowed 1mEq/L/Hr=42 mEq/hr(42 /513 ) X 1000= 81 cc /hour

Hyponatremia - ManagementWhat rate of infusion must be followed?Rapid correction < 1mEq/L/hrSlow correction 48 hrsRapid aggressive correction and improved mental status of patient48 72 hrs post Rx, patient suffers from confusion, gaze paralysis, spastic quadriplegia & seizures MRI detects the diagnosis

37Central Pontine Myolinolysis-CPM

T2-weighted MRI scan of the brain 38Hyponatremia - CPMCPM is unlikely to occur following rapid correction of acute hyponatremiaLohr, Am J Med (1994), vol 96 : HYPOKALEMIA predisposes patients to CPM following correction of hyponatremiaCorrect hypokalemia PRIOR to correction of Na+ in neurologically stable patient39Hyponatremia - ManagementHourly monitoring of the patients electrolytes is essentialSIADH can be treated with water restriction (800 ml/day), loop diuretics, or 600 1200 mg qd Demeclocycline (V2 receptor antagonist)40Hypernatremia 41Hypernatremia can either occur because of loss of free water or gain of Na in excess of water. Like hyponatremia it can be associated with differen volume. 42HypernatremiaClinical conditions associated with predominant water loss include:Diabetes mellitus (uncontrolled)Water deprivationSunstrokeHypercalcemiaHypocalcemiaHypophosphatemia BurnsIntracranial traumaTracheostomy HyperventilationFeverDiabetes insipidus43HypernatremiaPeople at most risk are: -the intubated -the elderly -patients with altered mental statusSince their thirst or access to water is impaired44Signs & Symptoms

47Hypernatremia - ManagementWhat solutions must be used?Select the most hypotonic infusate appropriate so as to use the least amount of fluid.

The more hypotonic the infusate is, the lower the infusion rate required 48Hypernatremia - ManagementCommonly used infusatesFree Water5% dextrose in water0.2% NaCl in 5% dextrose in water0.45% NaCl in water ( NSS)Ringers lactate 0.9% NaCl in water (NSS) 003477130 154 Infusate[Na+] mmol/LAvoid hyperglycemia when using dextrose solution, because it would aggravate the hypertonicity49Hypernatremia - ManagementReassess blood electrolyte at intervals of at least 6 to 8 hrsTreat DI with desmopressin (ADH analog)Correct hypernatremia due to hypertonic Na+ gain with both furosemide and waterRenal failure => hemodialysis, hemofiltration, peritoneal dialysis

50Hypokalemia51HypokalemiaK+ is the main cation in ICFNormal [K+] = 3.5 5.0 mEq/LIntake = 40 120 mEq/dayExcretion80% by kidneys15% by GI5% by sweat52Signs and Symptoms EKG changes do not correlate with hypokalemiaFlattened / inversion of T waveProminent U wave ST segment depressionProlongation of QT interval

Hypokalemia - CausesHypomagnesemiaDelays the correctionAssociated with increased frequency of arrhythmiasMg is the co-factor of Na/K ATPase

56HypokalemiaK level

Serum K in mEq/L

EKG changes and arrhythmias

Estimate of K deficit in mEq

Mild

3.5-3.0

None or minimal

100-200

Moderate

3.0-2.5

Yes, variable

00- 400

2Severe

2.5-2.0

Yes, dangerous

400-800 or more

With severe hypokalemia, K+ loss from the cells keeps serum K at or above 2.0 mEq/L.

57HypokalemiaManagement:K+ level = 4 to 3.0 mEq/L-fresh fruit, vegetables, meat-K+ replacement not necessary58HypokalemiaManagement:K+ level < 3.0Potassium replacement is necessary59Hypokalemia - ManagementWhat salts should be used?Potassium chloridePotassium phosphatePotassium bicarbonate (or precursor)Salt of choice, esp. with Cl- depletionPreferred if phosphate is depletedUsed if metabolic acidosis is present60Hypokalemia - ManagementThrough what route must the salt be administered?-Oral, except in emergencies or if oral route is not feasible => IV61Hypokalemia - ManagementOral route:Risk of ulceration and GI bleedingDose = 20 60 mEq, 2- 4 times/dayMust be monitored with daily K+ measurementsIf serum K+ does not rise by 96 hours => Mg depletionIf Mg< 1.0 mEq/L => 2 ml 50% MgSO4 IM bid 1st day, bid 2nd day, and qd 3rd day.62Hypokalemia - ManagementIV:-Peripheral vein

-Central vein

For maintenance of daily requirementsInfusate concentration = 20 40 mEq/LMaximum= 60 mEq/LFor moderate and severe hypokalemiaMaximum rate 40 mEq/hr63Hypokalemia - ManagementWhat solutions must be used for the correction?- Quarter or half NSSDextrose induces insulin response that drives K+ into cellsAdd 40 mEq/L to D5W to prevent the drop in serum K+64Hypokalemia - ManagementIn what rate must the solutions be infused?Usual maximum rate = 1020 mEq/hr40 mEq/hr can be used for only 2-3 hrsHigher rates predispose the patient to hyperkalemia and cardiac arrhythmiasMonitor serum K+ every 2-4 hrs and ensure adequate urine output65Hypokalemia - ManagementK+ sparing drugs: 1- spironolactone 2- triamterene 3- amilorideIf used, normal renal function must be ensured66Hypokalemia - ManagementMetabolic alkalosis must be corrected if present along with the hypokalemia, especially if serum K+ < 2.5 mEq/LDehydration must also managed, since further stress would aggravate the hypokalemia.67Hyperkalemia68Etiology Drugs that can cause Hyperkalemia Family of agentsIndividual drugsK-sparingSpironolactone,Triamterene, AmilorideACE inhibitorsCaptopril, Enalapril, FosinoprilNSAIDSIndomethacin, Ibuprofen, KetorolacAnti-infectiveTrimethoprim-sulfamethoxazole (Bactrim), PentamidineAnticoagulantHeparinCardiac glycosideDigitalisAntihypertensives-blockers, and - blockers (labetolol)70Hyperkalemia - CausesHeparin:Unfractionated nativeLMWHHeparinoidsCause reversible Aldosterone production inhibition => hyperkalemia in 7 to 8 % You should rule out heparin-induced adrenal hemorrhage by cortisol level and CT71Signs and Symptoms EKG changes ECG changes do not correlates closely with K levels. Peaked T wave Prolonged Pr and QRS AV conduction delay Sine wave that might terminate in VF or asystole

Treatment of Hyperkalemia Is hyperkalemia associated with physiologic effect such as cardiac arrhythmias ??Treatment of Hyperkalemia Treatment of Hyperkalemia DrugDoseOnset of ActionCalcium gluconate10-30 ml of 10% solution at 2 ml/min over 2 3 minFew minutesNaHCO344-132 mEq4 hoursGlucose and insulinGlucose: 25-50 gm/hr by continuous IV drip; regular insulin: 5U IV q 15 min15-30 minAlbuterolIV: 0.5 mg in 100 ml D5W over 10 15 minNebulized: 20 mg in 4 ml NSS over 10 min20 30 min30 minKayexalateEnema (50 100 gm)Oral (40 gm)60 min120 minTreatment of Hyperkalemia Hyperkalemia- MnemonicCBIGKDalciumicarbonatensulinlucoseayexalateialysisSee Big Potassium Drop78HypochloremiaRespiratory acidosis: tubular resorption of bicarbonate and less Cl-Causes: loss of gastric acid by vomiting or NG, renal losses from diuretics, ARF and CRF non-oliguricImportant to correct deficit with other deficits like hypochloremic hypokalemic metabolic acidosis 79Hyperchloremia Uncommon in surgical patientsIn association with hypernatremia, in RTA, excess KCL intake or ammonium chloride.Ileal urinary conduits, ureterosigmoidostomy. Mucosa absorbs Cl- in exchange of Bicarb.80Calcium40% of Ca++ in ECF bound to proteins, 10% complex with bicarb, citrate, and phosphate50% ionized, hormonally regulated are active. Neuromuscular activity8.5-11.0 Nl, ionized: 4.75-5.3.Most are bound to Albumin. PTH regulatedCorrected total Ca++ =[ 0.8 x (4- alb)] + total serum Ca++ 81Hypocalcemia Artifactual : low AlbuminAcute pancreatitisSurgically inducedNecrotizing fasciitisInadequate intestinal absorptionFistulae with excessive lossesChronic diarrheaRenal insufficiencyLow Mg++, high PO4--82Hypocalcemia Circumoral tingling, numbness fingertips crampsHyperactive DTRs, Chvostek sign, tetany and Trousseaus sign. Seizures .Confused or Depressed. Prolonged Q-T Calcium gluconate or chloride IVOral calcium lactate. Vitamin D. Thiazide diuretics 83Hypercalcemia - CausesHyperparathroidismMalignancyGranulomatous diseaseExcessive dietary intakeThiazide DiureticsImmobilizationEndocrine: thyrotoxicosis, adrenal insuf.84Hypercalcemia - TreatmentCalcium intake restrictedHydrationLoop diureticsOral or IV Phosphate supplementsCorticosteroids Plicamycin (mithramycin), DNA- binding antibiotic85Hypomagnesemia Low Mg++: common with starvation, GI losses, alcoholism and Drugs. Accompanied with low K+, PO4 and low Ca++Neuromuscular problems: cramps, fasciculations, tetany,confusion and arrythmias.Oral or IV magnesium sulfate. 1-2 mEq/kg/day

86Hypermagnesemia Renal failure Crush injury, burns: rhabdomyolysisDehydration, acidosis, adrenal insuff., cathartics, eclampsia and antacidsNausea, weakness, hypoventilation, decreased DTRs. Then hypotension, bradycardia, paralysis, respiratory dep. And comaRx: hydration, IV calcium, diuretics, dialysis87PhosphorusPhosphorus is important in energy production during glycolisisThe level is tightly controlled by renal excretion HypophosphatemiaEtiologyInadequate uptake increased renal excretion or compartmental shifts as result of insulin release, resp. alkalosis, alcoholism, burns , parathyroidectomy Treatment of DKARefeeding syndrome

Effect Platelet aggregationImpaired WBC chemotaxis and phagocytosisImpairs 02 release to tissue due to decrease in 2-3 DPGCardiac dysfunctionBone pain, anorexiaTremors

HypophosphatemiaTreatment Adequate nutritionCorrection depends on the level of depletion and tolerance to oral supplementation

HypophosphatemiaPO4 < 1 md/dLTolerating enteral nutritionKPHO4 or NaPO4 0.25mmol/kg over 6hrs x1 doseNot tolerating enteral nutritionKPHO4 or NaPO4 0.25 mmole/kg IV x 1dose . Recheck level 0.15mmole/kg if PO4 < 2.5mg/dLPO4 level 1.0-2.5 mg/dl Tolerating enteral nutritionNeutra-Phos 2 pack Q 6hrs per NGNot tolerating enteral nutritionKPHO4 or NaPO4 0.15mmole/kg IV Hyperphosphatemia EtiologyLow renal excretion, increased GI absorption or iatrogenicHyperthyroidism or HyperparathyroidismClinical condition associated with cell destructionRhabdomyolisisTumor lysis syndromeHemolysisSepsisSevere hypothermiaMalignant hyperthermia Excessive PO4 administration in hyperalimentation92Hyperphosphatemia Treatment: Aluminum-based antacids, diureticsCalcium acetate tablet when hypocalcemia is presentHemodialysis

Conclusion Proper management of fluid and electrolytes facilitates crucial homeostasis that allows cardiovascular perfusion, organ system function and cellular mechanism to respond to surgical illness

Knowledge of the compartmentalization of body fluid forms the basis for understanding pathologic shifts in theses fluid spaces in disease states. Although difficult to quantify a deficiency in the functional ECF fluid compartment often requires resuscitation with isotonic fluids in surgical and trauma patients. ConclusionAlteration in the concentration of serum Na have profound effects on cellular function due to water shifts between intracellular and extracellular spacesQuestions? Thank you