Fluid & Electrolyte in Surgical Patient

Dr.Mohammad Amin Mirza

Objectives :

1. Anatomy of Body Fluids

2. Normal Exchange of Fluid & Electrolyte

3. Classification of Body Fluid Changes

4. Fluid and Electrolyte Therapy in Surgical Patients

Total Body Water

body wt% Total bodywater%

total 60 100intracellular 40* 67extracellular 20 33

a-intravasc 5 8

b-interstitial 15 25

Total body water

Water 50-70% of TBW Sex : 60% of TBW young male 50% of TBW young female Age : Decrease wt aging Highest wt newborn 75-80%at 1year 65% elderly 52% M, 49%F

Composition of Fluids

plasma interstitial intracellular

Cations T=154 T=153 T=200Na 142 144 12K 4 4 150Ca 5 3 10Mg 3 1 40

Anions T=154 T=153 T=200Cl 103 104 3HCO3 27 27 10SO4 1 1 -HPO4 2 2 150Protein 16 5 40

OsmolalityPosm(mOsm/l)=2x serum [Na] + glocose/18 + BUN/2Case : post op pt serum Na 125meq/l RBS 500mg/dl,what is serum Na?

General role , each 100mg/dl rise RBS above normal equivalent to 1.6-3meq/l fall in Na , in this case if excess extracellular water eliminated Na 137meq/l

Osmotic Pressure

Total osmotic pressure of fluid :

Is sum of partial P of each solute in that fluid Osmotic pressure ECF=ICF why ?

The total no. of osmotic active particles 290-310 mOsm in each compartment

Bec, the cell membrane completely permeable to water any change in osmotic P in either compartments redistribution of the water between the compartments

Water exchange1-Water Intake

Normal total intake 2-2.5L/day

1- Sensible Oral fluids 800-1500 Solid foods 500-700

2- Insensible Water of oxidation 250 Water of solution 0-500

Normal Water Exchange2-water loss

1-Sensibleurine 800-1500intestinal 0-250sweat 0

2-Insensiblelungs/skin* 600

skin 75% lung 25%

The insensible water loss from the skin from water vapor in the body not sweats

Wt excess heat capacity for insesible loss >>sweating occur >250ml/day per degree of fever

Unhumidified tracheostomy wt hyperventilation >> loss throgh the lung 1.5L/day

Salt Gain & LossNa Exchange60-80 Kg man

Average mEq/day

MinimalmEq/day

Maximal

1-Na gain Diet

50-903-5 g NaCl

0 75-100 mEq/h

2-Na loss a-skin (sweat) 10-60

0 300mEq/h

b- urine 10-80 <1 mEq/day

110-200mEq/L

C-intestine 0-20 0 300 mEq/h

Composition of GIT SecretionType of secretion

Volumeml/24h

NaMeq/l

KMeq/l

ClMeq/l

HCO3Meq/l

salivary 1500 10 26 10 30

stomach 1500 60 10 160 0

duoden 100-2000

140 5 104 0

ileum 3000 140 5 104 30

colon 100-9000

60 30 40 0

pancreas 100-800 140 5 75 115

bile 50-800 145 5 100 35

Classification of Body Fluid Changes

1-volume changes2-concentration changes3-Compositional changesWhat would happen if ?*If isotonic salt lost or added from the body fluid*if water alone added or lost ECF?*If concentration of other ions than Na in ECF

changed without changes in osmotic active particles ?

1-volume changes Lab tests reflect changes ECF :BUN ,creatinine , HctA-volume deficit ECF deficit most common disorder in surg. PtLoss of water + electrolyte same prop.ECFCauses :Clinical:B-volume excessInc. in ECF ( plasma + interstitial volume)Causes :Clinical :

2-concentration changes

Na mainly responsible of ECF osmolarity , determination of serum Na indicate tonicity of the body fluid

1- Hyponatremia C/P

*acute symptomatic (Na<130meq/L)

*chronic asymptomatic till ( Na <120meq/L)

2- Hypenatremia C/P

* Only state in which dry sticky mucous membrane characteristic

3-compositional changes :

Compositional abnormalities include:

1. Changes in acid–base balance

2. Changes K, Ca, Mg Acid – Base Balance :

The PH of the body fluid maintained within narrow limit 7.4 (7.34 -7.43 )

PH=Pk +log BHCO3 = 27 meq/l =20 =7.4

H2CO3 1.33meq/l 1

1-Respiratory Alkalosis

Cause : hyperventilation ABG:PH , CO2Compens HCO3 Complication : CardiacCerebralhypo K , Ca Treatment : Cause ventilaton

2-Respiratory Acidosis

Cause :Inadequate

ventilation ABG:PH , CO2Compens,HCO3 Treatment : Causeventilation

3-Metabolic AcidosisCause :Gain an acidRetention of bicarb1-Normal anion gap2-high anion gapABGPH , HCO3Comp. CO2TreatmentCauseNa Hco3 indication and

contraindication

4-Metabolic AlkalosisCauseGain Bicarb,Loss of acidCommonest exampleABGPH , HCO3Compens . CO2 TreatmentCause ( Rxpyloric obst.)Treat hypo KNo need dec. ventilation

Pyloric obstruction

1. Resuscitation wt isotonic saline 2. replacement of K3. Correction of Cl in case of resistant metabolic

alkalosis Cl infusion : 150ml 0.1N hydrochloride in 1L N.S or D5% over 4-6h,wt

ABG+chemistry q4-6h, this wt D5%give 300meqHCL Chloride deficit in 70kg man, Cl level 80meq As chloride distributed in ECF

( plasma volume =20% body weight) Cl Deficit =20%BWx [normal Cl level – observed Cl ] (0.2x70)x ( 103-80 ) = 322 meq

3- Composition Changes: Hyperkalemia

Causes : ( intracellular extracellular ) Clinical : 1-GIT

2-CVS Treatment : 1. IV 1 gm 10% Ca gluconate over 10-15min2. Bicarb + insulin + Gluc

(45meq NaHCO3 in 1 L / D10W + 20 unit Regular insulin )

3. Definitive : Kayexalate or dialysis

3- Composition Changes: Hypokalemia

Causes in surgical pt: Decrease Input : 1. K free IVF wt renal loss >- 20meq/day2. TPN inadequate k

Increase Output: 1. GIT loss2. Renal loss3. Movement into cells

C/P of Hypo K: failure of normal contractility of Smooth M paralytic ileus Cardiac M ECG (flat T, depressed ST), charac. Skeletal M weaknessflaccid paralysis Treatment : Give K : No >40meq / L should be added to IVF No >40meq / h should be the rate of admin. Contraindication to give K : Oliguric pt During first 24h after severe surgical stress

3- Composition Changes

Ca Abnormalities : Intake : Normal daily intake of Ca 1-3 g Excretion : majority GIT, 200mg in urine Normal serum level 8.5-10.5 mg/dl

55% non- ionized bound to protiens 45% ionized for neuromuscular stability

The ratio of ionized:non-ionized related to PH acidosis inc,ionized + alkalosis dec,ionized

No indication to give Ca in surgical pt except in specific situations

Hypocalcemia

Causes in surgical pt : acute Pancreatitis, Pancreatic & SI fistula acute &chronic renal failure, massive soft tissue infection (NF) Hypo parathyroid Transient after surg of parathyroid adenoma

in pt wt hyperparathyroidism

Symptomatic if Ca < 8 mg/dl Neuromuscular signs : Numbness at circumoral, tips of finger or toes Muscle & abdominal cramp Tetany wt Carpopedal spasm ,convulsion Chovestek sign, Hyperactive tendon reflex ECG ( prolong QT )

Hypocalcemia C/P :

Acute symtoms : IV Ca gluconate or CaCl2 Chronic replacement : oral Ca lactate + or - vitD

Does the pt receiving blood transfusion need Ca ? NO except in pt receiving blood as rapid as 500ml

every 5 -10 min , Ca recommended Dose : IV Ca gluconate 0.2 g (2ml in 10%CaCl2 sol ),

for every 500cc blood , in separate line from the transfusion site, only when the blood transfused by the rate mentioned above & total Ca not >3gm.

Hypocalcemia treatment :(Ca)

Hypercalcemia Causes in surgical pt :1. Hyperparathyroidism2. Cancer wt bony metastasis (metastatic

breast CA on estrogen replacement ) C/P : GIT,Neuromuscular,Polyurea, polydepsia Treatment : Critical level when Ca >15 mg/dl med ER1. Diuresis (salt solution )2. Diuretic (furosemide)

Mg Abnormalities

Total body content of Mg 2000meq 50% in the bone , slowly exchangable Majority excreted in feces, rest in urine Serum Mg(1.5-2.5meq/l), bec mainly ICF

1-Mg Excess : Causes ; intake , gain C/P : as hyper K Rx: IV 5-10 meq CaCl, or Ca Gluc dialysis

Mg deficiency Causes : C/P ; same as hypo Ca diagnosis Routine administration considered in TPN pt

, or long term parentral fluid wt GIT dysfunction

Management : IV MgSO4,MgCl2, 2meq/kg/day severe def. TPN 12-24meq/day

Fluid & Electrolyte Therapy in surgical patient

Parenteral solutions Preoperative fluid therapy Intraoperative fluid therapy Postoperative fluid therapy

1. Immediate post OP

2. Late post OP

3. Special consideration in post OP

4. Acute renal failure

Parenteral solutoin Cations(mEq/L) Anions(mEq/L)

Solutions Na K Ca Mg Cl HCO3 mOsmExtracellular Fluid

142 4 5 3 103 27* 280-310

RL 130 4 3 - 109* 28* 2730.9%NaCl 154 154* 308D5 45%NaCl 77 77 407D5W - - 253M/6Na lactate 167 167 334

3% NaCl 513 513 1026

Parenteral Solutions

RL : ideal for replacement of GIT loss, ECF loss, in absence of gross abnormality in concentration or composition

(physiologic solution , minimal effect on the fluid composition or PH even in inf. Large amount)

NaCl :ideal for initial correction of ECF deficit in presence of hypo Na , hypo Cl, metabolic alkalosis ( dilutional acidosis)

Parenteral Solution

M/6 Sodium Lactate :

Alternative fluid hyponatremic, hypochloremic moderate metabolic acidosis

3% NaCl ( Molar Na lactate ) :

for rapidly correcting symptomatic hyponatremia The choice of lactate or chloride depend on

accompanying acid-base disorder

*Chloride for alkalosis

*lactate for acidosis

Pre OP Fluid Therapy if pre op replacement of ECF volume is

incomplete hypotension wt induction of anesthesia ( compensatory mech. Abolished)

Prevented by replacement of deficit + keeping baseline maintenance to do so

Body Fluid Disorders Categorized into

1. Volume Abnormalities

2. Concentration changes

3. Compositional & miscellaneous changes

Pre OP fluid correction1-volume correction

Depletion of ECF without change in the composition or concentration

Diagnosis clinically : Mild moderate, severe deficit(4,6-8,10%BW) Replacement : balanced salt solution as RL Rate : severe volume depletion 2 L/h ,

reassess ,in elderly need monitoring even CVP

Pre OP fluid correction2-concentration changes

General Role : Correction of concentration changes

depend whether the pt is symptomatic If symptomatic hyper or hypo Na , attention

to correct the concentration abnormality to the point that symptoms relieved, then attention shifted to correct ass. volume abnormality

Pre OP fluid correction2-concentration (hypo Na)

Case : 70kg women symptomatic hypoNa Na level (120meq/l),calculate Na deficit ?

Na deficit = (normal serum Na – observed Na) X total B water (TBWater= is 50% BW in F, 60% BW in M) This case total body water = 70 x 0.5=35L Na deficit = (140-120meq/L) x 35L = 700meq Replacement : initially ½ of calculated Na infused by

3% NaCl ,slowly ,rapid infusion cerebral myelinosis once the symptoms alleviated the pt reassessed

Continue Pre OP fluid correction

2-concentration Na1. If Profound hypo Na

( correction no > 12meq/L/24h )

2. If hypo Na +Volume deficit: the remainder of ressucitation continued

wt isotonic (Nacl in akalosis, M/6 lactate in acidosis), till symp,if Na normalized RL

3. If hypo Na + Volume Excess (care) after small amount of hypertonic saline

to relive the symptoms water restriction Rx of choice

Continue Pre OP fluid correction

2-concentration Na Severe symptomatic Hypernatremia wt

volume deficit : Safest method :

½ strength NaCl or ½ strength RL D5W may infused slowly till symptomatic relieve, if

ECF osmolarity dec.too rapidly convulsion & coma In absence of significant volume deficit: Water adm. in caution to avoid hypervolemia

Intra OP Fluid Therapy

Clinical Guide Lines for Intra OP fluid Administration:

1. Blood should be replaced as it is lost to maintain acceptable RBC mass irrespective of any fluid or electrolyte

2. The replacement of ECF should begin during OP

3. Balanced salt solution needed during OR 0.5-1L/h

to maximum 2-3L during 4h major abdominal OP, unless other measurable losses

4. Crystalloid not albumin ?

Post OP Fluid Therapy1-Immediate Post OP

Assessment of the post OP at recovery room:

1. Quantitative : OP loss estimated by surgeon <15-40% than the actual loss

2. Qualitative : V/S + urine out put ,etc Optimal Accepted parameters in post op:

1. BP 90/60 mmHg

2. pulse < 120bpm

3. urine out put 30-50ml/h.

1-Immediate Post OPVolume Replacement

Deficit + maintenance For pt wt circulatory instability , add 1Lisotonic

salt stat, wt frequent check to clarify the situation For maintenance : D5 0.45% NS ( k? ) K : unnecessary to add K during the 1st 24h after OR,

unless definitive deficit exist. K : can be added for maintenance in pt without

complication and need short term IVF K : contraindicated for pt wt prolong OP trauma had

>1 episode of hypotension or post traumatic hemorrhagic hypotension all oliguric renal failure

2-Late Post OP Accurate measurement and replacement of all

losses (sensible + insensible loss) 1-Estimated Insensible loss (skin & lung)

600ml/day ,increased by hyperventilation , hyper metabolism and fever upto 1.5L/day

Replacement wt D5W 2-Measures sensible loss

A- GIT loss : usually the loss isotonic or hypotonic

Replaced by isotonic salt solution ,replace losses volume for volume

2-Late Post OP 2-Cont,Sensible loss:

B-Sweat : not a problem except in febrile pt water loss 250ml/day per degree fever

But excessive sweating cause considerable Na loss in unacclimatized pt

C-Urine : volume not replaced in ml/ml basis usually 1L of maintenance IVF given to replace daily UOP Replacement : in healthy by D5W+minimal salt but in elderly wt salt losing kidney or head injury water alone can hyponatremia , salt added acc.to urinary Na loss

Fluid and Electrolyte Therapy

Surgical patients have Maintenance volume requirements On going losses Volume excess/deficits Maintenance electrolyte requirements Electrolyte excess/deficits

Fluid and Electrolyte Therapy

Normal maintenance requirements use BW formula

On going losses measure all losses in I/O chart estimate third space losses

Deficits estimate using vital signs estimate using HCT

Maintenance RequirementsThis includes: insensible

urinarystool losses

Body weight Fluid required0-10Kg 100ml/kg/dnext 10-20kg 50 ml/kg/dsubsequent 20 Kg 20ml/kg/d

15ml/Kg/d for elderly

Maintenance 70 Kg Man Needs

10 x 100 = 1000

10 x 50 = 500

50 x 20 = 1000

2500 mls / d

Maintenance Electrolyte Requirements

Na 1-2 meq/Kg/day

K 0.5-1 meq/Kg/day

Usually no K given until after urine output is

adequate and U/E done. K should be given

with care, by infusion slowly - never bolus Ca, PO4, Mg not required for short term

On Going Losses

NG drains fistulae third space losses

Concentration is similar to plasma

Replace with isotonic fluids

Time Frame for Replacement

Usually correct over 24 hours

For ill patients calculate over shorter period and reassess e.g. 12 hours or 3 hours for e op cases

Deficits - correct half the amount over the period and reassess

Special consideration in post OP pt

Volume Excess1. Early & late signs

Hypo Na1. Endogenous water release

2. Intracellular shift Hyper Na

1. Excessive external water loss

2. Increased renal water loss

3. Solute loading

Acute Renal Failure ( ARF )

ARF after trauma or surgical stress is lethal complication

Diagnosis :

1. Clinically : persistent oliguria UOP <500ml/day

2. Chemically : uremia after stabilization of circulation Clinical course :

characterized by oliguria lasting from several days to several weeks followed by progressive raise in daily urine volume until concentrating and excretory function of the kidney are gradually restored

Classification of ARF in surgical pt

Prerenal

Intrarenal

Postrenal

Hypovolemic shock (3rd space loss*) Hypertensive shock (hemorrhagic) Arterial occlusion (renal art stenosis) Cardiac failure

Trauma Toxins ( endotoxin sepsis , contrast) Drug ( NSAID, aminoglycoside ) Pigment (myoglobin , destabilized HGB)

Urethral obstruction Ureteral obstruction or disruption Bladder dysfunction ( anesth,nerve inj,drug)

Predisposing Factors to ARF

Trauma Sepsis Cardiopulmonary bypass Renal transplantation Urologic surgery Vascular disease Preexisting renal disease Radiographic contrast agents Drugs :aminoglycoside, NSAIDs, amphoteracin B,

cyclosporine, chlorinated inhalation anesthsia

Laboratory Diagnosis

Prerenal azotemia

Tubular injury

obstruction

Urine osmolality >500 <350 variable

U/P osmolality >1:25 <1:1 variable

U/P urea >8 <3 variable

U/P creatinine >40 <20 <20

Urine Na <20 >40 >40

Fraction excretion Na <1 >3 >3

Management of ARF Directed to the cause Directed to the biochemical abnormalities

in the blood : Metabolic acidosis Hyper K Hypo Na Hyper PO4

Hypo Ca Hyper Mg

Indication for dialysis Absolute : Volume overload refractory to medical Electrolyte abnormalities ( severe hyper K , hypo NA <120) Severe Acidosis refractory to medical Uremia ( uremic pericarditis, or encephalopathy)

Relative : BUN >100mg/dl in ARF Need for enternal feeding or hyperalimentation inARF Need for multiple blood transfusion Hemorrhagic complication wt ARF Drug intoxication wt hemodialyzable substance

Types of dialysis in ARF

1. Hemodialysis

2. Peritoneal dialysis

3. Continuous Art-Ven dialysis

4. Continuous Ven-Ven ultrafiltration

High output Renal Failure

Def : uremia occurring without a period of oliguria and accompanied by daily urine volume loss >1-1.5L / day up to 3-5 L/day

Cause : ??Less severe form of renal injury > oliguric ARF charact, by GFR < 20% of normal

Course : Urea raise 8-12 days before downward trend , P/U urea 1:1 until decrease in blood urea

The primary danger in this type is delayed in recognition because of normal urine output

Fluid Therapy in High output Renal Failure

Normal ECF volume & Na concentration can be maintained when accurate daily output replaced

An attempt to decrease UOP by water restriction hyper Na without change in urine volume

Na containing fluids wt lactate can be given to control mild metabolic acidosis , if isotonic loss from GIT or renal excretion of Na replaced wt NaCl can severe acidosis

K administration as little as 20meq may rapidly produce K myocardial intoxication

Thank You !!

Good Luck !!