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Fluid and Electrolytes
Review
Topics
• Body/fluid compartments • Body/fluid/electrolyte changes • Fluid/electrolyte therapy • Electrolyte abnormali:es in specific disease states
BODY/FLUID COMPARTMENTS
Body compartments in health and disease
WATER (60%)
FAT (25%)
PROTEIN (14%)
WATER (72%)
FAT (15%)
PROTEIN (12%)
WATER (70%)
FAT (23%)
PROTEIN (6%)
CARBO + OTHER (1%)
NORMAL STARVATION CRITICAL CARE
WATER (55%)
FAT (30%)
PROTEIN (14%)
OBESE
Compute fluids of a 70 kg person
• TBF=70kg x 60% = 42L (total body fluid) – ECF=70kg x 20% = 14L (extracellular fluid) – ICF=70kg x 40% = 28L (intracellular fluid)
• Total plasma volume = 70kg x 5% = 3.5L • Total blood volume (hct=38) = 5.6L
– Total inters::al fluid = 14L – 5.6L = 8.4L • Computa:on of usual fluid requirement per day:
– 30 ml/kg body weight (e.g. 70 kg) = 1.5 to 2.5 L/day (2.1 liters per day)
How to compute for total blood volume
– Plasma volume is 5% of actual body weight – Weight=70 kg; hematocrit = 38 – Total plasma volume = 5% x 70kg = 3500 ml – Total blood volume = 3500ml x (100/[100-‐38]) – TBV = 3500 ml x (100/62) = 3500ml x 1.61 – Total blood volume = 5645 ml or 5.6 liters
BODY/FLUID/ELECTROLYTE CHANGES
The circula:on Blood Volume in total
circula:on (5.6L): 70kg male • Systemic circula:on: 84%
(4.7L) – Arteries: 13% (0.7L) – Arterioles and capillaries: 7%
(0.4L) – Veins, venules, venous
sinuses: 64% (3.6L) • Heart and Lungs: 16% (0.9L)
– Heart : 7% (0.4L) – Pulmonary circula:on: 9%
(0.5L)
Reference: Chap 14: Guyton’s textbook of physiology
The circula:on Vessel Cross secWonal
area (cm2) Aorta 2.5 Small arteries 20 Arterioles 40 Capillaries 2500 Venules 250 Small veins 80 Venae cavae 8
Reference: Chap 14: Guyton’s textbook of physiology
Normal routes of water gain and loss at room temp (=230C)
Water intake ml/day Water loss ml/day Fluid 1200 Insensible 700 In Food 1000 Sweat 100 Metabolically produced from food
300 Feces 200
Urine 1500 Total 2500 2500
From: Berne R, ed. Physiology 5th ed. St. Louis, Missouri: Mosby 2004: p. 662.
Posi:ve ions Electrolyte Extracellular
mEq/L Intracellular
mEq/L FuncWon
Sodium 142 10 • Fluid balance • Osmo:c pressure
Potassium 5 100 • Neuromuscular excitability
• Acid base balance Calcium 5 -‐ • Bones
• Blood clohng Magnesium 2 123 • Enzymes Total 154 205
Nega:ve ions Electrolyte Extracellular
mEq/L Intracellular
mEq/L FuncWon
Chloride 105 2 • Fluid balance • Osmo:c pressure
Bicarbonate 24 8 • Acid base balance Proteins 16 55 • Osmo:c pressure Phosphate 2 149 • Energy storage Sulfate 1 -‐ • Protein
metabolism Total 154 205
Osmolality
• Normal cellular func:on requires normal serum osmolality
• Water homeostasis maintains serum osmolality • The contribu:ng factors to serum osmolality are: Na, glucose, and BUN
• Sodium is the major contributor (accounts for 90% of extracellular osmolality)
• Acute changes in serum osmolality will cause rapid changes in cell volume
How to compute for plasma osmolality
Osmolality = 2 x [Na] + [glucose]/18 + [BUN]/2.8
Na = 140 mmol/L Glucose = 110 mg/dL BUN = 20 mg/dL
Osmolality = (2x140) + (110/18) + (20/2.8)
Osmolality = 280 + 6.1 + 7.1
Osmolality = 293.2 mmol/L
Division of glucose and BUN by 18 and 2.8 converts these to mmol/L
Regula:on of sodium and water balance
An:-‐diure:c hormone
Aldosterone
ANH
ELECTROLYTE ABNORMALITIES
Hyponatremia VOLUME STATUS
HIGH NORMAL LOW
Increased intake
Post-‐opera:ve ADH Secre:on
Drugs (diure:cs)
Hyperglycemia
é Plasma lipids/proteins
SIDH
Water intoxica:on
Diure:cs
ê Sodium intake
GI losses
Renal losses
Primary renal disease
Schwartz’ Principles of Surgery 10th ed; G. Tom Shires III
Hypernatremia VOLUME STATUS
HIGH NORMAL LOW
Iatrogenic sodium administra:on
Mineralocortocoid
excess
Aldosteronism
Cushing’s disease
Congenital adrenal hyperplasia
Non-‐renal water loss
Skin, GI
Renal water loss
Renal disease
Diure:cs
Diabetes insipidus
Non-‐renal water loss
Skin, GI
Renal water losses
Renal (tubular) disease
Osmo:c diuresis
Diabetes insipidus
Adrenal failure
Schwartz’ Principles of Surgery 10th ed; G. Tom Shires III
Clinical Manifesta:ons Body System Hyponatremia Hypernatremia
Central nervous system
Headache, confusion, hyperac:ve or hypoac:ve deep tendon reflexes, seizures, coma, é intracranial pressure
Restlessness, lethargy, ataxia, irritability, tonic spasms, delirium, seizures, coma
Musculoskeletal Weakness, fa:gue, muscle cramps/twitching
Weakness
Cardiovascular Hypertension and bradycardia if ICP increases
Tachycardia, hypotension, syncope
Tissue Lacrima:on, saliva:on Dry s:cky mucous membranes, red swollen tongue, decreased saliva and tears
Renal Oliguria Oliguria
GI: Anorexia, nausea, vomi:ng, watery diarrhea
Metabolic: Fever
Schwartz’ Principles of Surgery 10th ed; G. Tom Shires III
Clinical manifesta:ons: High K, Mg, Ca
System Potassium Magnesium Calcium
>5.5 mEq/L >2.1 mEq/L >10.4 mg/dL
GI Nausea, vomi:ng, colic, diarrhea
Nausea, vomi:ng Anorexia, nausea/vomi:ng, abdominal pain
Neuromuscular Weakness, paralysis, respiratory failure
Weakness, lethargy, decreased reflexes
Weakness, confusion, coma, bone pain
Cardiovascular Arrhythmia, arrest Hypotension, arrest Hypertension, arrhythmia, polyuria
Renal -‐ -‐ Polydipsia
Increased Serum Levels
Schwartz’ Principles of Surgery 10th ed; G. Tom Shires III
Clinical manifesta:ons: Low K, Mg, Ca
System Potassium Magnesium Calcium
<3.5 mEq/L <1.4 mEq/L <8.8 mg/dL
GI Ileus, cons:pa:on -‐ -‐
Neuromuscular Decreased reflexes, fa:gue, weakness, paralysis
Hyperac:ve reflexes, muscle tremors, tetany, seizures
Hyperac:ve reflexes, paresthesias, carpopedal spasm, seizures
Cardiovascular Arrest Arrhythmia Heart failure
Decreased Serum Levels
Schwartz’ Principles of Surgery 10th ed; G. Tom Shires III
Acid-‐Base disorders
Disorder pH pCO2 (respiratory component)
Plasma bicarb (metabolic component)
Respiratory acidosis êê éé N
Respiratory alkalosis éé êê N
Metabolic acidosis êê N êê
Metabolic alkalosis éé N éé
Disorder pH pCO2 (respiratory component)
Plasma bicarbonate (metabolic component)
Respiratory acidosis ê éé é
Respiratory alkalosis é êê ê
Metabolic acidosis ê ê ê
Metabolic alkalosis é é? é
ACUTE UNCOMPENSATED
CHRONIC PARTIALLY COMPENSATED
FLUID AND ELECTROLYTE MANAGEMENT
Targeted compartments for IV therapy Use Compartment Composition Examples
Volume Replacement
Intravascular fluid volume
Iso-oncotic Isotonic Iso-ionic
6% HES 130 in balanced solution
Fluid Replacement
Extracellular fluid volume
Isotonic Iso-ionic
Balanced solution (obsolete) normal saline; ringer’s lactate
Electrolyte or osmotherapy (solutions for correction)
Total body fluid volume
According to need for correction
KCL Glucose 5% Mannitol
Reference: Zander R, Adams Ha, Boldt J. 2005; 40; 701-‐719
Composi:on of IV fluids
30
Parameters Plasma NSS LRS Sterofundin Na+ 142 154 130 140
K+ 4.5 0 5 4
Ca2+ 2.5 0 1 2.5
Mg2+ 0.85 0 1 1
Chloride 103 154 112 127
HCO3 24 0 0 0
Lactate 1.5 0 27 0
Acetate Malate
0 0 0 24 5
Colloid Albumin (30-50) 0 0 0
Osmolarity (mosmol/l)
291 308 276 304
30
Volume and electrolyte changes • Electrolytes = normal • Albumin = normal
ECF = loss • Intravascular loss • Inters::al = normal
• Balanced electrolyte solu:ons
• colloid
• Electrolytes = normal • Albumin = low
ECF = loss • Intravascular loss • Inters::al = swollen
• Balanced electrolyte solu:ons
• Colloid • Hypernatremia • Albumin = normal
ECF = loss/none • Intravascular loss • Cell shrink
• D5W • colloid
• Hyponatremia • Albumin = low
ECF = loss/none • Intravascular loss • Cell swell
• Hypertonic saline (3%SS)
• colloid
• Avoid D5W • Avoid 0.3% SS Cerebral edema
Crystalloids
Peri-‐opera:ve fluid therapy: effect of solu:on types
• 5% dextrose – is beser than sodium containing solu:on in inducing diuresis (Heller MB et al. 1996)
• Crystalloid (Ringer’s lactate) – Rapid infusion may increase the albumin escape rate from the intravascular space.
• Saline (0.9%) – Large volumes (50 mL/kg over 1 hr) in volunteers can produce abdominal discomfort and pain, nausea, drowsiness and decreased mental capacity to perform complex tasks → changes not noted auer infusion of iden:cal volumes of lactated Ringer’s solu:on (Willams EL et al. 1999)
– Saline infusions were also associated with a persistent acidosis and delayed micturi:on.
Fluid management in surgery
• Average periopera:ve fluid infusion: – Intra-‐op = 3.5 to 7 liters – 3 liters/day for the next 3 to 4 days – Average gain post-‐op = 3 to 6 kg weight gain
• Leads to: – Delay of gastrointes:nal func:on – Impair wound anastomosis healing – Affects :ssue oxygena:on – Prolonged hospital stay
Lassen et al. Arch Surg 2009
Surgery: fluid loss Fluid Loss Insensible perspira:on
• 10 ml/kg/day -‐ 2/3 skin, 1/3 lungs • Ven:la:on with 100% water = almost zero loss • Ven:la:on in dry air = 0.5 ml/kg/day
Evapora:ve loss • minor incisions with slightly exposed but non-‐exteriorised viscera = 2.1 g/hour
• moderate incisions with partly exposed but non-‐exteriorised viscera = 8.0 g/hour
• major incisions with completely exposed and exteriorised viscera = 32.2 g/hour
• Loss from completely exteriorised viscera decreases by 50% auer 20 minutes,
• Wrapping the exteriorised viscera in plas:c reduces the evapora:on loss by 87.5%.
Brandstrup B. Fluid therapy for the surgical pa:ent. Best Pract Res Clin Anaesthesiology 2006; 20(2): 265-‐83
Surgery: fluid loss Fluid Loss Third space loss: a) pathological fluid accumula:ons
• A volume of asci:c or pleural fluid emp:ed through drains or during surgery can be accurately measured
• 2.5–5 mL may accumulate around a large bowel anastomosis if no fluid is administered;
• 5–10 mL may accumulate if 15 mL/kg/hour fluid is given;
• Edematous en:re colon, the accumula:on would be 150–300 mL, depending on the volume/type of IVF
Third space loss: b) non-‐anatomical third space loss (or deficit in func:onal extracellular volume).
• U:lizing labelled bromide tracer: corrected for lost blood, expansion of ECV instead of a contrac:on was found following surgery.
• Volumes up to 15 mL/kg/hour are recommended in the first hour of abdominal surgery, with decreasing volumes in subsequent hours.
Brandstrup B. Fluid therapy for the surgical pa:ent. Best Pract Res Clin Anaesthesiology 2006; 20(2): 265-‐83
Surgery: fluid loss Fluid Loss Replacement of blood loss
• Replacement with crystalloids – expansion of the inters::al space, with postopera:ve oedema forma:on and body weight gain.
• Replacement with colloids – current advice: a colloid that stays in the vascular space for a longer :me seems to be a more expedient choice for replacement of lost blood.
Exuda:on from surgical wound
• Can be measured
Brandstrup B. Fluid therapy for the surgical pa:ent. Best Pract Res Clin Anaesthesiology 2006; 20(2): 265-‐83
How much fluid loss in surgery? Fluid Loss 60 kg wt Insensible perspira:on
Ven:la:on with 100% water = almost zero loss
0 ml
Evapora:ve loss • moderate incisions with partly exposed but non-‐exteriorised viscera = 8.0 mlhour
• major incisions with completely exposed and exteriorised viscera = 32.2 mlhour
8-‐30 ml per hr
Third space loss • Ascites or other fluids – measurable • Volumes up to 15 mL/kg/hour are
recommended in the first hour of abdominal surgery, with decreasing volumes in subsequent hours.
• Measure • 300 ml
Total • Within one hour (crystalloids not recommended)
350 first hour
Adapted from: Brandstrup B. Fluid therapy for the surgical pa:ent. Best Pract Res Clin Anaesthesiology 2006; 20(2): 265-‐83
Fluid and electrolyte imbalance INJURY = SURGERY
↑albumin escape from intravascular
space
Inflammatory mediators ↑vasodila:on effect of anesthe:c agents
↑K+ release from cells
↓K+ and ↑ Na intracellular
Sick cell syndrome of cri:cal illness
↑hypotonic fluid infusion
90% cause of hyponatremia in
surgery
Fluid RetenWon + Electrolyte Imbalance
Lobo D, Macafee DL, Allison S. How periopera:ve fluid balance influences postopera:ve outcomes. Best Pract Res Clin Anaesthesiology 2006; 20(3): 439–55.
Ileus and dehiscence Salt and water overload
↑intra-‐abdominal pressure
↓mesentery blood flow
Intes:nal edema
↓:ssue OH-‐proline
STAT3 ac:va:on ↓myosin phosphoryla:on
ILEUS
Impaired wound healing
DEHISCENCE
Intramucosal acidosis
↓muscle contrac:lity
Chowdhury and Lobo. Curr Opinion Clin Nutr Metab 2011
Anastomosis Leak
• Points to bowel prepara:on: – meta-‐analyses show that bowel prepara:on is not beneficial
– in elec:ve colonic surgery, and 2 smaller recent RCTs suggest that it increases the risk for anastomo:c leak
– Promote longer ileus dura:on
• Points to fluid management Lassen K et al. Consensus Review of Op:mal Periopera:ve Care in Colorectal Surgery: Enhanced Recovery Auer Surgery (ERAS) Group Recommenda:ons.
Arch Surg 2009; 144 (10): 961-‐9.
What is the worst fluid to give?
Plasma 0.9% saline Na (mmol/L) 135 – 145 154 Cl (mmol/L) 95 – 105 154 K (mmol/L) 3.5 – 5.3 0 HCO3 (mmol/L)
24 – 32 0
Osmolality (mOsm/kg) 275 – 295 308 pH 7.35 – 7.45 5.4
Lobo D, Macafee D, and Allison S. How periopera:ve fluid balance influences postopera:ve outcomes. Best Pract Res Clin Anaesthesiology 2006; 20(3):
439-‐55.
Peri-‐opera:ve fluid therapy: effect on organ func:ons and outcome
• (Lowell et al 1990) Post-‐op ICU pa:ents who gained >10% weight from preopera:ve or premorbid records, indica:ve of fluid overload : – Had significantly greater morbidity and length of ICU stay – Higher mortality with 100% mortality to those who gained >20%
weight
• (Arieff et al 1999): Post-‐opera:ve pulmonary edema : – Occurs within 36 hrs when net fluid reten:on exceeds 67 ml/kg/day
• (Alsous et al 2000): – at least 1 day of net nega:ve fluid balance on the first 3 days of
treatment strongly predicted survival.
Peri-‐opera:ve fluid therapy: effect on organ func:ons and outcome
• Moller et al 2002: – posi:ve fluid balance exceeding 4 Liters during anaesthesia was
associated with a higher risk of postopera:ve complica:ons than blood loss exceeding 1 Liter, and was the strongest risk factor for postopera:ve pulmonary complica:ons and mortality
• Mitchell et al (1992): – pulmonary edema management based on extravascular lung water
compared to pulmonary wedge pressure had less ven:lator days and shorter ICU stays
• Woods and Kelley (1993): – salt and water balance, and not the serum albumin concentra:on per
se, that is the determinant of recovery from postopera:ve ileus
Goal = zero fluid balance
• Brandstrup et al 2003 – A dose–response rela:onship was noted between postopera:ve complica:ons and increased volumes of intravenous fluid causing postopera:ve weight gain () – please see next two slides for the methodology
– fewer complica:ons and beser outcome than a group given standard periopera:ve fluids which had a 3–7-‐kg increase in body weight
Complica:ons
Brandstrup B et al. Effects of intravenous fluid restric:on on postopera:ve complica:ons: comparison of two periopera:ve fluid regimens: a randomized assessor-‐
blinded mul:center trial. Annals of Surgery 2003; 238: 641–648.
FLUID/ELECTROLYTE ABNORMALITIES IN SPECIFIC SURGICAL CONDITIONS
Specific surgical condi:ons
Refeeding syndrome • Elderly • Severely malnourished • Low normal values of Na, K,
Mg, P • Occurs in parenteral
nutri:on not delivered slowly
• Needs: high degree of suspicion
Neurologic paWents • Inappropriate secre:on of
ADH – Secondary to head injury or
surgery to the CNS – Loop dire:cs
• Diabetes insipidus – Vasopressin 5U
subcutaneously every 6 to 8 hours
Specific surgical condi:ons
Acute Renal Failure • Pre-‐renal azotemia –
correct • With Acute Tubular
Necrosis – fluid restric:on • With dialysis: no restric:ons
to nutrients and electrolytes; careful of phosphorus levels
• Electrolyte monitoring
Cancer paWents • Nutri:on management • Fluid and electrolyte
abnormali:es secondary to surgery and chemotherapy – Potassium – Calcium (malignancy most
common cause of hypercalcemia)
– Phosphorus – Magensium
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