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Post-operative management

Fluid balance & Electrolyte abnormalities

P. Van der Niepen

Dept. Nephrology & Hypertension

Universitair Ziekenhuis Brussel (VUB)

Brussel, 20 maart 2018

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Outline

Introduction

Fluid management (volume disturbances)

Hypo- and hypernatremia (concentration disturbances)

Hypo- and hyperkalemia

Hypo- and hypercalcemia

Mg/Phosphate

Acidosis and alkalosis

Conclusions - THM

composition disturbances

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Introduction

Fluid and electrolyte management are paramount

to the care of the surgical patient.

Changes in both fluid volume and electrolyte

composition occur

preoperatively,

intraoperatively, and

postoperatively,

as well as in response to trauma and sepsis.

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Introduction

Three principles of management of fluid &

electrolyte balance

1. Correct any abnormalities before surgery

2. Provide the daily requirements

3. Replace any abnormal and ongoing losses

(peri-operative)

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How to calculate a patient's fluid

requirements?

There is a distinction to be made between

1. the volume required to maintain the body's

normal functions and

2. the volume required to replace any

abnormal losses

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The normal maintenance fluid requirements will

vary depending on patient's

age,

gender,

weight and body surface area

Total Body Water

The estimated total body water is calculated as

a fraction (45 - 60%) of total body weight

gender and age

The fraction is

0.6 in non-elderly men and 0.5 in elderly men

0.5 in non-elderly women, 0.45 in elderly women(1)

6 Spasovski et al. Eur J Endocrin 2014; 170: G1–G47

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Total Body Water

Muscle and solid organs: higher water content

than fat and bone

Higher proportion of water in:

Young

Lean

Males

Obese individuals 10 – 20% less TBW (estimates)

Malnourished individuals 10% more TBW

7 Spasovski et al. Eur J Endocrin 2014; 170: G1–G47

Total Body Water: Three fluid compartments

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Intracellular compartment

Extracellular compartment

40%

20%

Plasma 5%

Interstitial fluid 15%

2/3

1/33/4

1/4

Male (40 j) 70 kg x 0.6 42 L

ECF: 70 kg x 20% = 14 L

PV: 70 kg x 5% = 3.5 L

IF : 70 kg x 15% = 10.5 L

ICF : 70 kg x 40% = 28 L

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Basic requirements - Fluid

Normal daily fluid requirement to maintain a

healthy 70 kg adult is between 2 and 3 L.

The individual will lose about 1500 mL (800 –

1200 mL) in the urine and

about 600 mL from the skin, lungs (insensible

loss) and 250 mL stool (loss from the skin will vary with the ambient

temperature)

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The electrolyte composition of intracellular (ICF)

and extracellular fluid (ECF) varies:

Electrolyte Extracellular fluid

(mmol/L)

Intracellular fluid (mmol/L)

Sodium 135 10

Potassium 4 150

Calcium 2.5 2.5

Magnesium 1.5 10

Chloride 100 10

Bicarbonate 27 10

Phosphate 1.5 45

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Only small between PV & IF

Sodium is the predominant cation in the ECF

Potassium predominates in the ICF

proteins

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Replacement if deprived of normal daily intake of

fluid & electrolytes

Volume depletion

without electrolyte disturbances (fever, intake)

accompanied by electrolyte deficit (e.g. vomiting,

ileus, fistula, diarrhea)

Source of fluid loss determines type of electrolyte lost

< considerable variation in electrolyte content of different

gastrointestinal secretions:

Loss from upper digestive tract: rich in acid (severe

prolonged vomiting from gastric outlet obstruction metabolic

alkalosis

Loss from lower tract: high in sodium and

bicarbonate ( metabolic acidosis)

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Composition of Gastrointestinal Secretions

Normal daily requirements of sodium (100 – 150

mmol/d) and of potassium (60 – 80 mmol/d) will balance

daily loss of these two cations in the urine.

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Stomach: H+ 70 mmol/l

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Management of fluid requirements

Can be done on a daily basis, but

Fluid and electrolyte replacements of an acutely ill

surgical patient necessitates close monitoring and

adjustment.

Clinical assessment and appreciation of type of fluid loss will

give an approximate guide to the scale of the problem, but

Biochemical electrolyte estimations will be required to

determine the precise needs of what needs to be replaced.

In most instances: measurement of plasma electrolyte

concentrations provides sufficient information,

Occasionally: it may be necessary to estimate the

electrolyte contents of the various fluids being lost.

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Disturbances in Fluid Balance

Most common in surgical patients

Extracellular volume deficit:

Acute

Cardiovascular signs (TC, OH)

Central nervous system signs

Chronic (Next slide)

OsmU > OsmPl

[Na+]u < 20 mEq/l and [Na+]pl N – () – ()

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Water depletion / dehydration

Clinical features

Thirst

Dryness of mouth

Dry loose skin

Sunken eyes

Oliguria

Hypotension

Delirium

Hemoconcentration(PCV)

Oliguric AKI

Causes

Low intake

Poor absorption

Increased loss (GI)

Diarrhea

Vomiting

Nasogastric suction

Enterocutaneous fistula

Sequestration (burns,

peritonitis, obstruction, …)

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Oliguria (<30 mL/h)Normal urine output: 0.5 - 2 ml/kg/h (bv. 70 kg: 35 – 140 ml/h)

Common problem in post-operative period

output of urine may be due to:

poor renal perfusion (pre-renal failure: hypovolaemia

a/o pump failure)

renal failure (acute tubular necrosis < hypotension)

renal tract obstruction (post-renal failure)

Treatment of oliguria depends on the cause.

Most cases of post-operative oliguria are secondary to

hypovolaemia, and should be considered to be due to

hypovolaemia until proven otherwise.

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Hourly maintenance fluid requirement

Useful tool for approximation of hourly maintenance fluid

requirement based on body weight:

The 421 RULE - Estimates maintenance fluid requirement

for an adult per hour

1st 10 kg BW, 4 mL/kg/h

2nd 10 kg BW, 2 mL/kg/h

For each remaining kg of BW, 1mL/kg/h

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Example: for a 70 kg patient:

1st 10 kg BW, 4 ml/kg/h: 4 ml/kg/h x 10 kg = 40 ml/h

2nd 10 kg BW, 2 ml/kg/h: 2 ml/kg/h x 10 kg = 20 ml/h

Remainder BW, 1ml/kg/h: 1 ml/kg/h x (70 kg – 20 kg) = 50 ml/h

Hourly maintenance fluid requirement:

40 ml/h + 20 ml/h + 50 ml/h = 110 ml/h x 24h = 2,640 L/24h

(adjusting based on increased losses,…)

Daily maintenance fluid requirement

Useful tool for approximation of daily maintenance fluid

requirement based on body weight:

The 100,50,20 - Estimates maintenance fluid requirement

for an adult over 24 hours

1st 10 kg BW, 100 mL/kg/d

2nd 10 kg BW, 50 mL/kg/d

For each remaining kg of BW, 20 mL/kg/d

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Example: for a 70 kg patient:

1st 10 kg, 100 ml/kg/d: 100 ml/kg/d x 10 kg = 1000 ml/d

2nd 10 kg, 50 ml/kg/d: 50 ml/kg/d x 10 kg = 500 ml/d

Remainder BW, 20 ml/kg/d: 20 ml/kg/d x (70 – 20 kg) = 1000 ml/d

24h maintenance fluid requirement:

1000 + 500 + 1000 = 2500 ml/day = 104 ml/h (adjusting based on

increased losses, …)

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Daily maintenance fluid requirement

Cave

Obese patiënten:

Bereken op IDEAAL LG (zelden heeft een pt

>3L/dag nodig) (ex. 130 kg: 3700 – 4200 mL/d)

Oudere patiënten/ NI of HF/ ernstige malnutritie (cave refeeding S)

20 – 25 mL/kg/dag

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24h maintenance fluid requirement:

Example: for a 70 kg patient:

20 - 25 mL/kg/d: 20 mL/kg/d x 70 kg = 1400 mL/d à 25 mL/kg/d x

70 kg = 1750 mL/d or 58 – 73 ml/h (adjusting based on increased

losses, …)

Basic daily electrolyte requirements

Na+: 100 - 150 mmol/day – K+: 60 - 80 mmol/d

Requirements may be considerably higher in ill,

post-op patients (e.g. severe vomiting, fluxing stoma, …)

Daily requirements of major electrolytes

Sodium: 1 mmol/kg/d

Potassium: 1 mmol/kg/d

Chloride: 1 mmol/kg/d

Calcium: 2 g/d

Magnesium: 20 mEq/d (10 mmol/kg/d)

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Composition of common replacement fluids

Normal saline (0.9%) solution (1L): pH 5.7 – Osm 308

Na 154 mmol

Cl 154 mmol

K 0 mmol

5% Dextrose solution (1L): pH 3.5 – 6.5 – Osm 278

50 g of Dextrose (170 kcal/L)

Hartmann's (Ringer Lactate) (1L): pH 6.4 – Osm 273

Na 131 mmol/L

Cl 111 mmol/L

K 5 mmol/L

Lactate 29 mmol/L (metabolized to HCO3- in the liver)

Trace Calcium (2 mmol/L)

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Electrolyte solutions for parenteral adm.

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Electrolyte composition (mEq/l)

Solution Na Cl K HCO3 Ca Mg mOsm

ECF 142 103 4 27 5 3 280-310

Lactate Ringer* 130 109 4 28 3 273

Plasmalyte** 140 98 5 acetaat 27

gluconaat 23

3 295

0,9% NaCl* 154 154 308

0,45% NaCl 77 77 154

3% NaCl 513 513 1026

5% glucose(*) 278

*isotonic; **pH: 7,4 (6,5 – 8,0) cave alkalose en hypocalciëmie

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Sodium

75 - 85% of Na+ is in the extracellular space (¼

plasma + ¾ interstitium)

Exogenous fluid administration follows the

same distribution

If 1L Saline is given:

250 mL will remain within the intravascular system

750 mL will go to the IF

sodium-containing fluids expand the

interstitium space by 3 times as much as the

plasma!

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Natrium: 135-145 Mmol/L

Hypernatremia

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Hypernatremia

Hypernatremia in the post-operative patient is a less

common problem than hyponatremia.

Acute hypernatremia = rare (salt intoxication, DI, …)

Any hypernatremia is usually relative rather than

absolute and occurs

secondary to diminished water intake, or

secondary to increased water loss (severe burns, high fever)

plasma [Na+] loss of ECF volume and relative

intracellular desiccation.

The first clinical manifestation is thirst and if

hypernatremia persists neurological problems (e.g.

confusion, convulsions, coma)

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Hypernatremia: [Na+] > 145 mmol/LCauses

Assess volume status

High Normal* Low*

Iatrogenic sodium adm** Non-renal water loss Non-renal water loss

Mineralocorticoid excess Skin Skin

Aldosteronism GI GI

Cushing’s disease Renal water loss Renal water loss

Cong. adrenal hyperplasia Renal disease Renal (tubular) disease

Diuretics Osmotic diuretics

Diabetes insipidus

(ADH)

Diabetes insipidus

(ADH)

Adrenal failure

Hypervolemic

hypernatremia

Normovolemic

hypernatremia

Hypovolemic

hypernatremia

*less fluid intake

**Hypertonic fluids

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HypernatremiaDiagnostiek

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ADH te kort

HypernatremiaSymptomen en tekens

Enkel symptomatisch als verstoord dorstgevoel

of vochtrestrictie, want dorst water inname

Klinische verschijnselen als [Na+] >160 mmol/L:

Vaak opmerkelijk weinig klinische symptomen,

vooral bij ouderen

Neurologische symptomen tgv. hyperosmolariteit

Rusteloosheid, lethargie, … delirium, E, coma

Polyurie – oligurie ( oorzaak)

Dorst

Droge mucosae

Orthostatische hypotensie, TC

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HypernatremiaGevaren

Acuut:

Risico op cerebrale bloedingen, bij een

hypernatriëmie die zich in korte tijd (< 48 uur)

heeft ontwikkeld met cerebrale verschijnselen (Osmpl onttrekt water uit cellen tractie …)

Chronisch:

Risico op hersenoedeem en inklemming, bij

te snelle correctie v/e langer bestaande (> 48 u)

hypernatriëmie, vanwege adaptatie v/d

hersenen (Osmpl drijft water naar cellen

opzwellen …)

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Hypernatriëmie hersenoedeem

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Correction of Hypernatremia

In normovolemic patients: replace water deficit

with hypotonic fluid (5% dextrose) or oral water

supplementation

In hypovolemic patients: restore volume with

normal saline (hypotonic if DM decompensation)

Water deficit (L) = ----------------------------- x TBW*

*Estimate TBW as 45 - 60% of lean body mass ( gender and age)

However, use values 10 % lower in hypernatremic patients who are

water depleted!

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Serum sodium - 140

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Correction of Hypernatremia

Rate of fluid administration:

Acute hyperNa: in Na+] <1 mEq/L/h

5% dextrose; 3 – 6 mL/kg/h; control Na+] each 1-2h 145 mEq/l

5% dextrose: 1 mL/kg/h nprmonatremia

Chronic (>48h) hyperNa: 8 mEq/L/d – 12 mEq/L/d (Na+] ,

symptoms, age, …)

Cave cerebral edema and herniation

(too rapid correction)

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CT- scan acuut hersenoedeem

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Casus 1: 70 j v – 4 dagen post GI ingreep – 60 kg

Water deficit: TBW* x ----------------------------

(*TBW = 40% v/h LG (60 kg) = 24L)

24L x (164 – 140)/140 = 4,114L deficit

Eerste 24 u: (8 mEq/d corrigeren)

24L x (164 -156)/156 = 1,231L glucose 5% + …

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Serum sodium - 140

140

Comateus - koorts

[Na+] 164 mmol/l

Diurese: ? Oligurie en Osmol in urine

*estimate TBW as 50% of lean body mass in men and 40% in women

Casus 1: 70 j v – 4 dagen post GI ingreep – 60 kg

Dag 2

Waterdeficit: 24 L x (156 - 140)/140 = 2,743 L

Glucose 5%: 24 L x (156 - 148/148)= 1,297 L

Normale behoefte: 100 mL + 50 mL + (40 kg x 20 mL

= 800 mL) = 950 mL 0,9% NaCl + bijkomend verlies

Dag 3

Waterdeficit: 24 L x (148 - 140)/140) = 1, 371 L

Glucose 5%: 24 L x (148 - 140/140) = 1,371 L

Normale behoefte: 100 mL + 50 mL + (40 kg x 20 mL

= 800 mL) = 950 mL 0,9% NaCl43

[Na+] 164 mmol/l 156 mmol/l 148 mmol/l 140

mmol/l

Dag 1 Dag 3Dag 2

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EXCESS OF EXTRACELLULAR WATER RELATIVE TO SODIUM

Hyponatremia

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ECV kan hoog, normaal of laag zijn

Hyponatremia: [Na+] < 136 mmol/L Causes

Assess volume status

High Normal Low

Dilutional Depletional

intake Hyperglycemia* intake

Post-op ADH secretion Plasma lipids/proteins GI losses/ Burns

Drugs () ADH (SIADH) Renal losses

CHF/Hepatic failure/CRF Water intoxication - Diuretics

Diuretics - Renal disease

Hypervolemic

hyponatremia

Normovolemic

hyponatremia

Hypovolemic

hyponatremia

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* For every 100 mg/dl plasma glucose plasma sodium 1.6 mEq/l

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Hyponatremia

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Fluids Commonly Lost Sodium Concentration

(mEq/L)

Urine variable

Diarrhea 40

Gastric secretions 55

Furosemide diuresis 75

Sweat 80

Small bowel secretions 145

HyponatremieKlinische symptomen

Naargelang ernst van hyponatremie (Na+ < 136

mmol/L)

Milde hyponatremie (130 – 135 mmol/L)

Matig ernstige hyponatremie (125 – 129 mmol/L)

Na+ < 125 mmol/L: ernstige symptomen (onmiddellijk

behandelen met hypertoon saline)

Naargelang snelheid van ontstaan

Acute hyponatremie <48u

Vnl. CZS, en tgv.

Cellulaire waterintoxicatie en

intracraniële druk

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HyponatremieKlinische symptomen

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Systeem Hyponatriëmie

CZS Hoofdpijn, verwardheid, hyper- of hypoactieve

peesreflexen, E, coma, intracraniële druk

MusculoskeletaalZwakte, vermoeidheid, spierkrampen/ -

trekkingen

GI Anorexie, nausea, braken, waterige diarree

Cardiovasculair HT + BC tgv. intracraniële druk

Mucosae speeksel- en traanproductie

Nier Oligurie/ nl / polyurie oorzaak

Management of Hyponatremia

Exclude hyperosmolar causes (mannitol, glycemia)

Depletion versus dilution

Dehydration or over hydrated

Normal volume evaluate ADH (ISADH)

Na losses

Urine Na <20 mEq/L = Extrarenal sodium loss

Urine Na >20 mEq/L = Renal sodium loss

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HyponatremiaTreatment ~ etiology

Hyponatremia due to overhydration:

fluid restriction

Hyponatremia due to losses:

Correction with saline infusion (154 mmol/L)

Hypertonic saline

150 ml 3% (513 mmol/L: 77 mEq/150 mL) over 20 min if

severe symptoms

Cave: too rapid correction can lead to central

pontine myelinolysis

Aim for 0.5 mEq/L/h (<1 mEq/L/h)

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MRI osmotische demyelinisatie syndroom

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Weakness, paresis, E, akinetic

movements, unresponsiveness,

ev. permanent brain damage &

death

Osmotic stress caused by rapid

correction of hyponatremia results

in focal loss of oligodendrocytes

and myelin, with sparing of

neurons and axons, and can

cause transient BBB disruption.

Hyponatremia due to lossesTreatment

Acute hyponatremie:

Onmiddellijk met hypertoon zout behandelen ongeacht

de oorzaak. Bereken hoeveelheid hypertoon zout (3%

NaCl: 513 mEq/L) met Adrogué-Madias formule:

Chronische hyponatremie:

Vermijdt te snelle correctie en richt behandeling op

onderliggende oorzaak.

Toename in Na+ max 0,5 mmol/L/u

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Vb. 120 mmol/L – 56j vr – 90 kg

(513 – 120)/ (0,5 x 90) + 1 = 8,543 mmol

(5)/ (8,543) = 0.585 L of 585 mL over 10 u

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Hyponatremia due to lossesTreatment

How much sodium needs to be given?

[Na+] needed = (target [Na+] - actual [Na+] ) × TBW (45 -

60% BW)

Rate of infusion (ml/h) = ([Na+] needed (mmol) x 1000)/

infusate [Na+] (mmol/l) x time (hours)

Example: 56 j woman 90 kg & [Na+] 126 mEq/L

[Na+] needed = (140 - 126) × 0.5 (90) = 630 mEq Na

4,09 L of saline (1 L 0.9% = 154 mmol: 630/154 = 4,09 L) or

Rate of infusion (ml/h) = (630 mEq x 1000)/(154 mEq/L

x 72h) = 57 ml/h

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Aim for 0.5 mEq/L/h (<1 mEq/L/h if symptomatic)

http://www.medcalc.com/sodium.html

www.medcalc.com/sodium

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Iso- en Hypervolemische hyponatremieWaterrestrictie

Hartfalen, nierfalen, leverfalen,

SIADH,

Primaire polydipsie

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Potassium

Average daily intake: 50 – 100 mEq/l

Extracellular K+: narrow range

Principally by renal excretion: 10 – 700 mEq/day

Normal [K+]pl: 3,5 – 5,0 mEq/l

Only 2% of total body K+ is located in EC

compartment

Critical to cardial & neuromuscular functions

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Hyperkalemia

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Hyperkalemia

Hyperkaliëmie: [K+] > 5,0 mmol/L

Risicogroepen:

Patiënten met nierinsufficiëntie

Hyperglycemie

Kaliumsupplementen of medicatie die de

kaliumhuishouding beïnvloeden

Ouderen

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HyperkalemiaOorzaken

Pseudohyperkaliëmie, bv. onzorgvuldige bloedafname

intake:

Supplements (oraal, IV)

Blood transfusion(red cell lysis)

Release from cells (Redistribution)

Hemolysis, rhabdomyolysis, tumor necrosis, GI bleeding

Acidosis; hyperglycemia (Osm shift)

Impaired potassium excretion

Renal failure

Potassium sparing diuretics (spironolacton) or RAAS blockers, NSAID

Hypoaldosteronism or aldosteron resistance, Adrenal insufficiency,

salt wasting

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HyperkalemiaKlinische verschijnselen en Gevaren

Meestal geen symptomen

GI symptomen:

nausea, vomiting, intestinal colic, diarrhea

Neuromusculaire symptomen:

Slecht reagerende patiënt/ lethargie, slap - zwak paralyse

dyspneu - respiratory failure

CV symptomen:

Hypotensie (< 90 mm Hg)

ECG-afwijkingen: Peaked T waves, widened QRS complex,

prolonged PR interval VF or asystole

Ernstige hyperkaliëmie: potentieel levensbedreigend <

hartritmestoornissen, acute hartstilstand of

spierverlammingen.

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Hyperkalemia

With normal renal function, severe and life-threatening

hyperkalemia is rare (may occur in severe trauma, sepsis and

acidosis)

High [K+] in the ECF can be associated with cardiac

rhythm disturbances and asystole

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HyperkalemiaBehandeling

Exogene bron STOPPEN

Acuut:

Shift van kalium van ECF IC

NaHCO3- (100 ml 8.4%): werkt na 5 à 10 min, gedurende 2 u

en kan na 2 u herhaald worden

Insuline en Glucose: 50 à 100 ml glucose 50% met 10 - 20 E

AR, gevolgd door drip en glucose-infuus: werkt na 15 min,

ged. 4 u

Nebulized albuterol/ salbutamol 10 - 20 mg (ventolin)

Potassium removal

Lasix 1 mg/kg IV (cave: polyurie)

Kayexalaat peroraal of lavement: 15 à 30 g in 50 à 100 ml

sorbitol 20% (max effect na 6 u) of 50 g in 200 ml 20% sorbitol

Hemodialyse

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HyperkalemiaBehandeling

Acuut:

Bij ECG veranderingen: Ca2+: vermindert de

verhoogde membraanexcitabiliteit; werkt slechts 5 min,

kan herhaald worden (1 g Ca2+): 5 – 10 ml 10%

calciumgluconaat

Subacuut:

Insuline (drip aan 4 E/h) en Glucose 20% aan 100 ml/h

Zo nodig hemodialyse

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Hypokalemia

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Hypokaliëmie

Laag K+ postoperatief is frequent, maar hypokaliëmie

is zelden zo ernstig om spierzwakte, ileus of aritmieën

te veroorzaken.

Risicogroepen

Gebruik van diuretica

Patiënten met braken en diarree

Ouderen

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HypokaliëmieOorzaken:

Vals: tgv leucocytose (>100.000/µl)

Verminderde intake door alcoholisme, anorexie;

kaliumvrije infusen

Verlies:

Excessieve renale kalium excretie (Ku>20 mmol/L): diuretica, hypomagnesiëmie, overmaat mineralocorticoïden,

hyperaldosteronisme, genetische renale tubulaire defecten, polyurie

GI verlies (Ku <20 mmol/L): braken/ maagdrainage,

diarree, malabsorptie, laxativa

Huid: zweten, brandwonden

Transcellulaire shift: alkalose* (hyperventilatie), verhoogde

insuline-beschikbaarheid, ß-adrenerge activiteit, hypothermie

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*K+ met 0,3 mEq/L voor elke 0,1 in pH

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Neurologisch/neuromusculair: spierzwakte, paralyse,

krampen, myalgie, paresthesieën, rhabdomyolyse, verminderde

peesreflexen

Gastrointestinaal: ileus, obstipatie, nausea/vomitus

Cardiaal: ECG-afwijkingen (U-golven) met of zonder ritmestoornis

(ES, sinusBC, AVB, VF) (cave combinatie hypokaliëmie en digoxine)

Renaal: concentratiestoornis (nefrogene DI): polyurie/ polydipsie

Endocrien: Hyperglycemie

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HypokaliëmieSymptomen:

HypokaliëmieGevaren

Paralyse ademhalingsspieren, respiratoire insufficiëntie

Hartritmestoornissen

Rhabdomyolyse

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U-golf Vlakke T-golf ST-segment veranderingen

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HypokaliëmieBehandeling ~ (a)symptomatisch

Orale supplementen zo asymptomatisch

40 mEq KCl

Parenterale supplementen

1 g KCl = 13 mEq K

Maximaal 2 x 10 à 20 mEq over 1 à 2 uur (uitz. tot 4x; nooit >10

mEq/u in niet gemonitorde setting)

Bij continue ECG monitoring: tot 40 mEq/u

Gemiddeld extra over 12 uur: 20 – 40 – 60 mEq volstaan.

Maximaal 60 mmol/L via centrale catheter of 40 mmol/L via

perifeer infuus

Maximale infusiesnelheid 20 mmol/uur en max. 2 – 3 mmol/kg

lichaamsgewicht/24 uur

*Faster rates may precipitate arrhythmias and should only be undertaken on a unit

where the patient can be monitored for any ECG changes. 82

HypokaliëmieBehandeling ~ (a)symptomatisch

Opmerkingen:

Chronische hypokaliëmie bij asymptomatische patiënten moet

niet onmiddellijk genormaliseerd worden

Overcorrectie kan meer schade aanrichten dan de hypokaliëmie

zelf. Doses van 10 - 20 mEq/u kunnen snel leiden tot

hyperkaliëmie, vnl. bij begeleidende acidose, diabetes mellitus,

renale tubulaire acidose en in aanwezigheid van NSAID, RAAS

blokkers en -blokkers.

Kalium via een perifeer infuus is caustisch en doet pijn.

Het kaliumdeficit bedraagt ongeveer

300 mEq bij K+ < 3 mEq/L

700 mEq bij K+ < 2 mEq/L

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Treatment - Potassium replacement

Rule of thumb:

10 mEq IV replaces 0.1 mmol/L in serum

e.g. K+ 2.6 mmol/L 3.8 mmol/L

1.2 mmol/L correction

Als 0.1 mmol/L = 10 mEq

1.2 x 10/0.1 mmol/L = 120 mEq

Correct for

Ongoing losses

Correct hypomagnesemia

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Take Home Messages

Corrigeer vocht- en elektrolytenstoornissen

preoperatief

Meestal gecombineerde vocht-

elektrolytenstoornissen

Hypovolemische hyponatremie (depletie zout en water)

Hypovolemische hypernatremie (rel. water > zout;

zweten, diarree, brandwonden)

Bereken dagelijkse behoefte

Hou rekening met ev. verliezen

Vochtbilan/ G/ BD – HR/ T°

85

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Calcium

<1% of total body calcium is located in EC compartment

Three forms:

1. 40% protein bound

2. 10% complexed to phosphate and other anions

3. 50% ionized: responsible for neuromuscular stability

For every 1 g/dl in albumin adjust total serum calcium

down by 0.8 mg/dl

in pH affect ionized Ca: acidose protein binding

ionized calcium

Daily intake: 1 – 3 g/day

Excretion: bowel & (renal)

[Ca2+]: 8.5 – 10.5 mg/dl or 2.15 – 2.60 mmol/l

86

Hypocalcemia

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Hypocalcemia: sCa<8.5 mg/dl; [Ca2+ ]<4.2 mg/dl

Symptoms & Causes

Paresthesia, Cramps, Neuromuscular spasms

Hyperreflexia - Tetany – Chvostek’s/ Trousseau’s sign - E

Increased QT interval VF

Cardiac depression – heart failure

Pancreatitis, pancreatic and small bowel fistulas

Chronic Renal Failure

Decreased Vitamin D

Hypoparathyroidism or post thyroid surgery

Massive soft tissue infections (necrotizing fasciitis),

Sepsis, toxic shock syndrome,

Polytransfusion (citrate)

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[Ca2+ ] <2.5 mg/dl

Hypocalcemia: sCa<8.5 mg/dl; [Ca2+ ]<4.2 mg/dl

Treatment

Calcium and Vitamin D replacement

Asymptomatic

Calcium carbonate PO 1250 mg 4x/d

Calcium gluconate IV (2 g over 1u)

Acute symptoms

Calcium gluconate IV (10%); doel: sCa 7 – 9 mg/dL

Correct associated deficits in Mg and K, correct acidosis

Refractory hypocalcemia if coexisting hypomagnesemia

89

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Hypercalcemia

90

Hypercalcemia: sCa>10 mg/dl; [Ca2+ ]>4.8 mg/dl

Causes

Hyperparathyroidism (primary or 2nd)

Cancer-bony metastases

91

These 2 reasons account for 90% of

hypercalcemia

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Hypercalcemia: Total [Ca2+] > 10.5 mg/dlSymptoms

Anorexia, nausea & vomiting common, ileus,

constipation, abdominal pain, & thirst (polydipsia)

Hypovolemia, hypotension

Zwaktegevoel, confusion, coma

Arrythmia: shortened QT interval, prolonged PR & QRS

AVB … arrest

Hypertension

Polyuria and nephrolithiasis

Symptoms usual occur [Ca2+] > 12 mg/dl

Critical level: [Ca2+] > 15 mg/dl

92

Hypercalcemia: Total [Ca2+] > 10 mg/dlTreatment

Replace fluid deficit

Normal Saline diuresis with or without furosemide

(lasix®)

Calcitonin

Given as 4 U/kg q 12

Mild effect (decreases Ca2+ by 0.5 mmol/L)

Biphosphonates

Etidronate 7.5 mg/kg in 250 ml NS over 2 hours for 3 days

Zometa 4 mg IV infusion over 15 minutes, repeat in 7 days

Hemodialysis

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Phosphate

Intracellular anion

Renal excretion

Is involved in energy produced during glycolysis

Daily intake: 0.8 - 1 gram phosphate

94

Hypophosphatemia

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Hypophosphatemia: PO4- < 2.6 mg/dl

Causes

intake

Decreased GI absorption (malabsorption, phosphate

binders, malnutrition)

excretion

Diuretics (carbonic anhydrase inhibitors)

Hyperparathyroidism

Metabolic acidosis (diabetic ketoacidosis), …

Intracellular shift

Refeeding syndrome, hungry bone syndrome

Glucose loading + insulin

Respiratory Alkalosis

96

Hypophosphatemia: PO4- < 2.6 mg/dl

Symptoms

Often silent; however

Exacerbate Chronic Heart Failure

Anemia

Decreases 2,3-diphosphoglycerate (shifts the

oxyhemoglobin dissociation curve to the left)

Muscle weakness

Cardiac dysfunctions

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Hypophosphatemia: PO4- < 2.6 mg/dL

Treatment

Oral or IV replacement for values 1 – 2.5 mg/dL

Recommendation: 1200 – 1500 mg/day (kaliumfosfaatdrank)

0.08-0.16 mmol/kg IV over 6 hours (kalium/natriumfosfaat )

Oral or IV replacement for values < 1 mg/dL

0.25 mmol/kg IV over 6 hours (kalium/natriumfosfaat); recheck

phosphate 4h after end infusion: if <2.5 mg/dL

Tolerating enteral nutrition oral

Not tolerating enteral nutrition 0.15 mmol/kg IV over 6h

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Hyperphosphatemia

99

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Hyperphosphatemia: PO4- > 4.8 mg/dl

Symptoms: ?

Itching

Chronic: metastatic calcifications

Causes

Renal excretion: CKD, hypoparathyroidism,

hyperthyroidism

Excessive administration: IV hyperalimentation,

Phosphate containing laxatives

Cell destruction: rhabdomyolysis, Tumor necrosis,

hemolysis, sepsis, severe hypo – or hyperthermia

Treatment

Phosphate binders: Sucralfate, calcium & non-Ca

Hemodialysis if RF100

Magnesium

Primarily IC cation

½ of the total body Mg content = bone

In EC compartment: 1/3 is bound to serum

albumin

Daily intake: 20 mEq/day

Excretion: Feces & urine

101

2000 mEq

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Hypomagnesemia

102

Hypomagnesemia: Mg2+ < 1.5 mg/dlCauses

Common in hospitalised patients (critically ill)

intake: alcoholism, starvation, prolonged IV fluids,

TPN with inadequate Mg supplementation

renal excretion: alcohol, diuretics (furosemide),

aminoglycosides, cisplatin, diabetes mellitus, primary

hyperaldosteronism

Pathologic losses: diarrhea, malabsorption, acute

pancreatitis, …

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Hypomagnesemia: Mg2+ < 1.5 mg/dlSymptoms

Mg is essential for function of many enzyme systems

Neuromuscular & CNS hyperactivity(~ hypocalcemia): hyperreflexia, muscle tremor, tetany,

Chvostek’s & Trousseau’s signs, delirium, seizures

Arrhythmias (prolonged QT & PR, ST … torsades de

pointes)

Can also cause

Decreased K+ (40%)

Decreased PO4- (30%)

Decreased Na+ (27%)

Decreased Ca2+ (22%)104

Hypomagnesemia: Mg2+ < 1.5 mg/dlTreatment

Oral replacement

Magnesium oxide 400 mg (Magnetop, Promagnor)

Magnesium gluconate 500 mg (Ultra Mg)

IV replacement 1 - 2 g over 1 h infusion (MgSO4)

If Mg <1 mEq/l (<1.2 mg/dl or <0.5 mmol/l)

1 mEq/kg in 250 ml saline over 24h during 1 day, then

0.5 mEq/kg ….. during 2 days

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Hypermagnesemia

106

Hypermagnesemia: [Mg2+] > 2.5 mg/dlCauses & Symptoms

Is rare

Hemolysis

Renal insufficiency (cave Mg containing anti-acids &

laxatives)

Nausea, vomiting,

Weakness, lethargy, hyporeflexia (4 mg/dl or 1.74

mmol/l)

Complete heart block – (10 mg/dl or 4.35 mmol/l)

Cardiac arrest – (13 mg/dl or 5.65 mmol/l)

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Hypermagnesaemia: [Mg2+]> 2.5 mg/dlTreatment

Calcium gluconate 1 g IV over 2 - 3 minutes

Volume replacement and furosemide

Correct acidosis

Hemodialysis

108

Acid-base homeostasis

109

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Acid-base homeostasis

pH of body fluids is maintained within a narrow range

despite

Large endogenous acid load (by-product of metabolism)

neutralized by buffer systems (intracellular proteins and

phosphates and extracellular bicarbonate-carbonic acid system)

and

excreted by lungs and kidneys

110

Acid-base homeostasis

In response to metabolic abnormalities

Changes (fast) in ventilation are mediated by hydrogen-

sensitive chemoreceptors (ChR) (carotid body and brain stem)

metabolic acidosis stimulates ChR ventilation

metabolic alkalosis decreases ChR activity ventilation

In response to respiratory abnormalities

Kidneys increase or decrease bicarbonate reabsorption

(begins after 6h)

respiratory acidosis stimulates bicarbonate reabsorption

respiratory alkalosis decreases bicarbonate reabsorption

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Metabolic acidosis

112

Acute

(uncompensated)

Chronic

(partially

compensated)

pH

PCO2 N

Plasma HCO3-

Anion gap = (Na+) – (Cl- + HCO3-): index of unmeasured anions

Normal AG < 12 mmol/L

Hypoalbuminemia decreases AG

AGcorrected = AGactual - 2.5 (4.5 – albumin)]

High AG exogenous acid ingestion or endogenous acid production

Increased AG

Exogenous acid ingestion

Ethylene glycol

Salicylate

Methanol

Endogenous acid

production

Ketoacidosis

Lactic acidosis

Renal insufficiency

Normal AG

Acid administration (HCl)

Loss of bicarbonate

GI losses (diarrhea,

fistulas, or

ureterosigmoidostomy)

Renal tubular acidosis

Carbonic anhydrase

inhibitor

113

Metabolic acidosisEtiology

Anion gap = (Na+) – (Cl- + HCO3-)

index of unmeasured anions

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Metabolic acidosis

114

Acute

(uncompensated)

Chronic

(partially

compensated)

pH

PCO2 N

Plasma HCO3-

Increased intake or increased generation of acids or increased loss of

bicarbonate

Body

produces buffers (extracellular bicarbonate, intracellular buffers

from bone and muscle),

increases ventilation (Kussmaul),

increases renal reabsorption and generation of bicarbonate

Increases renal excretion of H+ (NH4+)

Metabolic alkalosis

115

Acute

(uncompensated)

Chronic

(partially

compensated)

pH

PCO2 N ()

Plasma HCO3-

Increased bicarbonate generation

Decreased renal bicarbonate excretion

Loss of acids

Worsened by K+ depletion (K+ exchange with intracellular H+)

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Increased bicarbonate

generation

Chloride losing (>20 mEq/l)

Mineralocorticoid excess

Profound K+ depletion

Chloride sparing (<20 mEq/l)

Loss from gastric

secretions (emesis or NG

suction)

diuretics

Excess administration of alkali

Acetate in parenteral nutrition

Citrate in blood transfusion

Antacids

Bicarbonate

Milk-alkali syndrome

Impaired bicarbonate

excretion

GFR

Increased bicarbonate

reabsorption (hypercapnie,

K depletie)

116

Metabolic alkalosisEtiology

Respiratory acidosis

117

Acute

(uncompensated)

Chronic

(partially

compensated)

pH

PCO2

Plasma HCO3- N

Retention of CO2 secondary to alveolar hypoventilation

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Respiratory acidosisEtiology: hypoventilation

Narcotics

CNS injury

Pulmonary, significant

Secretions, mucus plug, atelectasis

Pneumonia, pleural effusions

Pain from abdominal or thoracic injuries or incisions

Limited diaphragmatic excursion from intra-abdominal

pathology

Abdominal distention

Abdominal compartment syndrome

Ascites

118

Respiratory alkalosisEtiology: hyperventilation

119

Acute

(uncompensated)

Chronic

(partially

compensated)

pH

PCO2

Plasma HCO3- N

Secondary to hyperventilation due to• Pain, Anxiety

• Pulmonary embolism

• Neurologic disorders (CNS injury, assisted ventilation)

• Salicylates, fever, gram-negative bacteremia, thyrotoxicosis,

hypoxemia

Acute hypocapnia hypokalemia, hypophosphatemia,

hypocalcemia arrhythmias, paresthesias, muscle cramps and

seizures

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Take Home Messages

Corrigeer vocht- en elektrolytenstoornissen

preoperatief

Meestal gecombineerde vocht-

elektrolytenstoornissen

Hypovolemische hyponatremie (depletie zout en water)

Hypovolemische hypernatremie (rel. water > zout;

zweten, diarree, brandwonden)

Bereken dagelijkse behoefte

Hou rekening met ev. verliezen

Vochtbilan/ G/ BD – HR/ T°

121