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large swelling which is soft, smooth, fluctuant, brilliantly transilluminant, and compressible (For detail refer
Chapter 5—Neck).
LYMPH CYST (LYMPHATIC CYST)
It is an acquired type of distension cyst wherein lymphatics
form a localised swelling with a capsule around it.
It usually occurs in subcutaneous plane, which is smooth,
soft, nontender, mobile, and brilliantly transillu minant. It is
usually not adherent to the skin.
Common sites are neck and limbs.
It can get infected and form an abscess.
Differential diagnosis: Cold abscess, dermoid cyst.
SRB's Manual of Surgery
Treatment: Excision.
CALCINOSIS CUTIS
It is a type of calcification (dystrophic) in or under the skin.
Usually presents as a circumscribed lesion in the skin.
Commonly seen in females. Common site is in the waist
(Fig. 1.188)
Usually bilateral.
It is said to be due to friction causing degeneration of skin
and immediate deeper structure with increa
of the tissue causing precipitation of the calcium leading to
solid, hard, swelling in the skin. Cut section shows hard,
yellowish material.
It may mimic calcified lipoma or neurofibroma.
Treatment is excision and closure of defect often with local
flaps.
sed local alkalinity
EPIGNATHUS
This is a type of growth anomaly seen in neonates wherein
growth from the base of skull protrudes through the mouth.
Fig. 1.188: Epignathus.
Note:
• Enucleation is removal of the swelling within the tissue of origin with normal
part of tissue of origin is being retained, e.g. enucleation of prostate in
benign prostatic hyperplasia (BPH).
• Excision is removal of tissue/tumour entirely with its capsule.
• Wide excision is removal of tumour with surrounding tissue margin
adequately for clearance.
• Compartment excision is removal of tumour/diseased tissue with all
adjacent soft tissues in one compartment except neurovascular bundle.
It is done in limbs for soft tissue sarcoma as a curative but limb saving
procedure.
• Radical excision/radical block dissection is removal of tumour widely with
adjacent soft tissues with lymph node dissection.
Fig. 1.187: Calcinosis cutis near waist is a common site. It is
CHORDOMA
Chrodoma is a slow growing tumour arising from notochord.
It can be classical, chondroid and dedifferentiated. It is
commonly seen in sacrococcygeal, sphenoid sinus (clivus)
and foramen magnum region. It invades the surrounding
structures. It often attains large size. MRI is diagnostic.
Treatment is wide excision. Radiotherapy is less useful but
highly focused proton or carbon ion radiation is effective than
conventional X-ray radiation.
common in females.
Fig. 1.189: Different incisions used in surgical
approaches to remove swelling.
SWELLINGS WHICH ARE CROSS FLUCTUANT
B
x Psoas abscess x Bilocular hydrocoele
x Ranula (plunging) x Compound palmar ganglion
F. Electrolyte and Nutrition
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C hapter Outline
·
Normal Physiology
·
Water Loss (Volume Loss)
·
Water Excess (ECF
Volume Excess)
·
Hyponatraemia
·
Hypernatraemia
·
Hypokalaemia
·
Hyperkalaemia
·
Hypermagnesaemia
·
Hypomagnesaemia
·
Acid-Base Balance
·
Metabolic Alkalosis
·
Respiratory Alkalosis
NORMAL PHYSIOLOGY
Total body water is 60% of body weight in males, 50% of body
weight in females, i.e. 30 litres.
Intracellular water—20 litres (2/3).
Extracellular water—10 litres (1/3).
¾
Plasma (1/4) (2.5 litres).
¾
Interstitial fluid (7.5 litres).
Ion ICF ECF and plasma
Sodium 10 mmol/L 140 mmol/L
Potassium 150 mmol/L 4.5 mmol/L
Chloride Trace only 105 mmol/L
ECF volume and osmolality regulation is controlled by three
hormones. Aldosterone, ADH, atrial natriuretic hormone.
WATER LOSS (VOLUME LOSS)
It is decrease in the whole body fluid volume which includes
both ECF and ICF. It is usually ECF loss which is more important
and assessed. It can be isotonic volume depletion with both salt
and water loss leading into hypovolaemia, or only water loss
with only minimal loss of electrolytes leading into dehydration.
Causes and Features
Isotonic volume depletion occurs due to diarrhoea, vomiting,
and excess diuresis. Here normal or decreased sodium is
observed. Fluid loss is only of ECF and so early intravascular
volume reduction occurs. This causes hypotension and
decreased tissue perfusion. Features are—dry tongue, rapid
pulse, cold clammy extremities, sunken eyes, hypotension,
oliguria, raised blood urea, decreased urinary sodium. Hypovolaemia can be mild (<2 L fluid loss); moderate (2–3 L fluid
loss); severe (>3 L fluid loss).
·
Metabolic Acidosis
·
Respiratory Acidosis
·
Anion Gap
·
Fluid Therapy
·
Nutrition
·
Gastrostomy
·
Jejunostomy
·
Total Parenteral
Nutrition
·
Refeeding Syndrome
·
Obesity and Morbid
Obesity
x Different Surgeries
Only pure water loss occurs due to poor fluid intake and diabetes
insipidus. It causes dehydration with proportionate decrease
in total body water (2/3rd ICF, 1/3rd ECF). As ECF including
intravascular fluid loss is less, hypotension is less. Features here
are—severe thirst, confusion and convulsions due to hypernatraemia; blood pressure is relatively normal. Dehydration
can be mild (weight loss 5%); moderate (10%); severe (15%).
Management
Evaluation is done by estimating serum sodium, urinary
sodium, and blood urea.
Isotonic volume depletion is corrected by infusion of 0.9%
normal saline.
Pure water depletion is corrected by more water intake/
intravenous 5% dextrose.
Monitoring fluid therapy by skin and tongue examination,
weight gain, pulse, blood pressure, CVP, PCWP.
WATER EXCESS (ECF VOLUME EXCESS)
It can be divided into water and salt excess or predominantly
water excess called as water intoxication.
Water and salt excess occurs in CCF, cirrhosis, nephrotic
syndrome, hypoproteinaemia, renal failure, excessive saline
infusion.
Water intoxication occurs in TURP, excess infusion of 5%
dextrose only, SIADH secretion, psychogenic polydypsia. It
is managed by stopping fluid infusion or procedure (TURP);
fluid restriction, and treating the cause.
Causes
¾
Excessive amount of intravenous dextrose (5%).
¾
During colorectal bowel wash for preparation of large bowel
for surgery, if water is used instead of saline, especially in
children.
¾
In transurethral resection of prostate (TURP) when
excess irrigating fluid water or glycine is used (commonly
used).
¾
In syndrome of inappropriate antidiuretic hor mone
(SIADH) which is commonly associated with lobar pneumonia, empyema, oat cell carcinoma and head injury.
CLINICAL FEATURES
B
Drowsiness, weakness; Convulsions and coma
Nausea, vomiting; Passage of dilute urine
Distended neck veins; Pedal oedema
Gain in body weight—most sensitive and consistent sign
Circulatory overload—tachycardia, pulmonary oedema, hypertension
Bilateral basal crepitations, ascites; Raised CVP, PCWP
Investigations: Haematocrit and sodium level (will show fall
in level); Low potassium. Low blood urea.
Treatment:
¾
Water and salt restriction and observation.
Move to the rhythm of soul and you’ll never miss a beat.—Vicki Virk
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¾
Monitoring in ICU.
¾
Management of fluid and electrolyte balance.
¾
Infusion of hypotonic sodium chloride.
Note:
• Administration of diuretics and hypertonic saline should beavoided, as
it may cause rapid changes in serum sodium and water level which will
lead to neuronal demyelination and fatal outcome.
• ECF loss: Here only ECF loss is present with normal ICF.It is seen in
vomiting, diarrhoea, intestinal obstruction. Treatment is infusion of
normal saline.
• ECF excess: Only ECF excess without an ICF excess. Features are—
excessive infusion of saline with impaired excretion; raised JVP (earliest
and best clinical sign), cardiac failure and peripheral oedema. Treatment
SRB's Manual of Surgery
is fluid restriction and diuretics like frusemide.
HYPONATRAEMIA
Sodium level is less than 130 mEq/L. Hyponatraemia is said to
be severe if serum sodium becomes lesser than 100 mEq/
acute type; and lesser than 115 mEq/
due to water overload (dilutional) or sodium loss.
TYPES OF HYPONATRAEMIA
B
Acute—presents as neurological manifestations.
Chronic—causes pontine myelinolysis. It presents as behavioural
changes, progressive weakness, and cranial nerve palsies.
Types also may be:
Hypervolaemic hyponatraemia wherein rapid absorption of fluid
occurs into intravascular compartment leading into pulmonary and cerebral oedema. It is due to decreased osmolality
causing movement of ECF into the cells. Serum sodium level
lesser than 100 mmol/L is called as severe hyponatraemia,
causes convulsions. Here urinary sodium will be less than 15
mmol/L. Acute hyponatraemia is corrected by fluid restriction,
hypertonic saline, loop diuretics like frusemide. Monitoring the
serum sodium level of the patient is essential. Sodium should
be corrected up to above the level of 125 mmol/L. Correction
should be slow and gradual at a rate of 2 mEq/L/h with up to
20 mEq/L correction in 24 hours with 4th hourly assessment
of serum sodium. Overcorrection of sodium should not be
done. Rapid correction can lead into irreversible myelin lysis
of pontine.
Hypovolaemic hyponatraemia: It is due to hypovolaemia by
diarrhoea, vomiting, wherein urine sodium level is less than 20
mmol/L; due to diuresis or renal causes wherein urine sodium
level is more than 20 mmol/L or it may be due to correction of
hypovolaemia using hypotonic fluid like 5% dextrose. Condition
can be treated well using isotonic normal saline.
Normovolaemic hyponatraemia: It may be due to renal failure
or syndrome of inappropriate ADH secretion (SIADH). In
mild asymptomatic patients it is corrected by fluid restriction
(1 L/day will raise the serum Na). Vasopressin antagonist
demeclocycline which increases the diluting ability of kidney
is used in severe cases.
Pseudohyponatraemia: Plasma osmolality is mainly achieved
by serum sodium; but small proportion, i.e. 25% of osmolality
is due to other solutes like glucose, lipids, plasma proteins,
urea which will not move easily between intracellular and
extracellular spaces. When concentration of these molecules
L in chronic type. It can be
L in
raise due to some pathology, proportionately relative concentration of sodium will drop causing pseudohyponatraemia.
Here condition causing related to specific solutes mentioned
above is treated, than hyponatraemia.
Causes
Intestinal obstruction.
Intestinal fistulas—biliary, duodenal, gastric, pancreatic.
Gastric outlet obstruction with severe vomiting.
Ryle’s tube aspiration; Severe diarrhoea due to viral cause,
in colitis, colorectal polyps.
Syndrome of inappropriate antidiuretic hormone (SIADH).
Immediately after surgery and trauma, sodium depletion occurs.
Stroke.
CLINICAL FEATURES
B
Dry coated tongue; Sunken eyes; Dry wrinkled skin
Hypotension; Dark scanty urine; Convulsions
Irritability, disorientation and neurological manifestations
In chronic hyponatraemia—hypothermia, reduced tendon
reflexes, pseudobulbar pasly
Investigations: Serum electrolytes. Urinary sodium is low;
Sodium deficit is calculated by: (125 – present serum sodium)
× body weight in kg × 0.6.
Treatment
¾
Intravenous infusion of normal saline as a slow and
gradual correction at a rate of 2 mEq/L/hour in acute cases
and <1 mEq/L/hour in chronic cases. Correction should
not exceed more than 20 mEq/L/day in acute cases and
more than 10 mEq/L/day in chronic cases. Hypertonic
saline of 1.6% or 3% also can be used in severe cases.
0.9% normal saline contains 154 mEq of NaCl; 3% saline
contains 500 mEq of NaCl.
¾
The cause is treated.
HYPERNATRAEMIA
Serum sodium level >150 mEq/L. Excess infusion of normal
saline causes overload in circulating salt and water. It is
usually due to water deficit.
Causes: Renal dysfunction; Cardiac failure; Drug induced like
NSAID, corticosteroids.
It may be either primary sodium excess or primary potassium
excess or primary water deficit.
TYPES OF HYPERNATRAEMIA
B
Euvolemic (pure water loss): It is due to failure of water intake like
in comatous patients, bedridden people, postoperative patients
and in patients with high fever leading into extrarenal loss of
water. It can occur in diabetes insipidus or chronic renal failure
as renal loss of water.
Hypovolaemic (among loss of water and sodium, more water is
lost than sodium): It is due to vomiting, diarrhoea, more undue
sweating (extrarenal); osmotic diuresis by glucose/mannitol (renal).
Hypervolaemic (both sodium and water gain but sodium gain is
more than water gain) as seen in more salt intake, excess steroids,
sodium bicarbonate/hypertonic saline infusion (salt gain).
Features: Pitting oedema; Puffiness of face; Increased
urination; Often dilated jugular veins; Features of pulmonary
oedema.
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Investigation: Serum electrolytes, plasma and urine osmo-
lality, renal function tests, haematocrit.
Management:
¾
Restriction of saline and sodium. Treatment of pulmonary
oedema.
¾
Hypernatraemia should be corrected slowly as follows:
–
Initial infusion of normal saline, then infusion of half
strength saline (0.45%) and later with 5% dextrose,
i.e. gradual controlled correction is done. Otherwise
cerebral oedema and hyperglycaemia can develop.
–
Oral and nasogastric administration of water/fluids.
HYPOKALAEMIA
Sudden Hypokalaemia
Serum potassium level less than 3.5 mEq/L. It occurs in patients
in diabetic coma treated by insulin and saline infusion.
Gradual Hypokalaemia
Causes
Diarrhoea of any causes, villous tumour of the rectum, ulcera-
tive colitis; After trauma or surgery.
Pyloric stenosis with gastric outlet obstruction.
Duodenal fistula, ileostomy; After ureterosigmoidostomy.
Insulin therapy; Poisoning; Drugs like beta agonists.
Familial periodic paralysis.
Features
Slurred speech; Muscular hypotonia—physical sign.
Depressed reflexes; Paralytic ileus.
Weakness of respiratory muscles; Cardiac arrhythmias.
Inability to produce concentrated urine and so causes
nocturia and polyuria.
ECG shows prolonged QT interval, depression of the ST
segment and inversion of T wave, prominent U wave.
Often hypokalaemia is associated with alkalosis.
Serum potassium will be decreased.
Treatment
¾
Oral potassium 2 g 6th hourly, 15 mL potassium chloride
syrup (20 mmol of K).
¾
IV KCl 40 mmol/L given in 5% dextrose or nor mal saline
slowly, often under ECG monitoring [Total dose is 40
mmol (0.2 mmol/kg/hour). Maximum dose per hour is
20 mmol].
¾
Hypokalaemic alkalosis which occurs in pyloric stenosis
should be treated carefully by IV potassium as there will
be severe potassium loss.
HYPERKALAEMIA
Normal range of potassium is 4.0 to 4.5 mEq/L. Hyper-
kalaemia manifests when potassium exceeds 6 mEq/L.
Causes
¾
Renal failure; Rapid infusion of potassium.
¾
Transfusion of stored blood; Diabetic ketoacidosis.
¾
Adrenal insufficiency; Metabolic acidosis.
¾
Potassium sparing diuretics, cyclosporine, beta blockers.
¾
Insulin deficiency.
¾
Tissue destruction, burns, trauma, tumour necrosis, crush
injury.
¾
In vitro haemolysis, thrombocytosis, tourniquet applica-
tion, exercise—pseudohyperkalaemia.
¾
Familial hyperkalaemic periodic paralysis.
Note:
Potassium excess is a dangerous condition which can cause sudden
cardiac arrest.
Management
High serum potassium level. Peak ‘T’ wave in an ECG.
IV administration of 50 mL of 50% glucose with 10 units of
soluble insulin, slowly.
Infusion of 10% calcium gluconate slowly (as cardio-
protection) intravenously.
Calcium chloride is given in severe cases as calcium in this
form is released immediately without hepatic metabolism.
Diuresis using frusemide injection.
Haemodialysis when required—very useful.
Continuous ECG monitoring is a must.
Polyesterene sulphonate ion exchange resin 30 g/hour in
50 mL of 70% sorbitol as an enema.
Salbutamol nebulisation or intravenously 0.5 mg in 4 mL of
saline/Albuterol nebulisation.
IV sodium bicarbonate—shifts potassium in to cells. 7.5%,
with 50–100 mL intravenously in 10 minutes.
HYPERMAGNESAEMIA
It is rare. Serum magnesium >2.5 mEq/L. Normal serum
magnesium is 1.5–2.5 mEq/L and intracellular magnesium
which is more (2nd higher) is 26 mEq/L. Magnesium is
mainly deposited in bone (60%). It is a cofactor for many
enzymes necessary in phosphorylation of glucose in the cell
and ATP utilisation in muscle fiber. Daily required dietary
intake of magnesium is 0.4 gram. It is reabsorbed well in
proximal renal tubule.
Causes: Advanced renal failure treated with magnesium
containing antacids, diabetic ketoacidosis; Intentionally
produced hypermagnesaemia while treating pre eclampsia.
Features:
¾
Loss of tendon reflexes (most common).
¾
Neuromuscular depression; Flaccid quadriplegia.
¾
Respiratory paralysis; Somnolence; Hypotension.
89
CHAPTER 1F General Surgery: Electrolyte and Nutrition
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90
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HYPOMAGNESAEMIA
Serum magnesium <1.5 mEq/L.
Causes: Malnutrition, alcohol; Large GI fluid loss; Patients
on total parenteral nutrition.
Features:
¾
Hyperreflexia; Muscle spasm; Paraesthesia; Tetany.
¾
It mimics hypocalcaemia. It is often associated with
hypokalaemia and hypo calcaemia.
Treatment: Two gram (16 mEq) of magnesium sulphate
slow intravenously, in 10 minutes. Later maintenance dose
of 1 mEq/kg/day as slow continuous infusion is given/oral
SRB's Manual of Surgery
magnesium is needed.
ACID-BASE BALANCE
Normal pH (– log 10 of H+) is 7.36–7.44.
FACTORS WHICH CONTROL THE PH
B
Buffer system
– Bicarbonate buffer
– Protein buffer
– Phosphate buffer
Renal control of pH
Respiratory control of pH
Note:
• When H
• An acid is a substance that dissociates water to release hydrogen ion.
• Acidosis is pH of blood less than 7.35. Alkalosis is pH more than 7.45.
+
increases pH decreases.
A base is a substance that takes hydrogen ion. A buffer is a combination of weak acid and conjugate base. These buffers maintain the H
concentration in blood within fine limits. Natural buffers are extracellular
or intracellular. Bicarbonate/carbonic acid buffer, phosphate buffer
and plasma proteins are extracellular natural buffers. Haemoglobin
and other proteins are intracellular buffers. Bicarbonate/carbonic acid
buffer is most important as carbonic acid levels are regulated by lungs
which eliminates excess of it
controlled by kidney.
. Bicarbonate part is separately
as CO
2
HENDERSON-HASSELBALCH EQUATION(USED TO
B
ASSESS pH)
It is used to find out pH of the blood using logarithm. Negative
logarithm of constant K (800 for carbonic buffer) is called as pKa. It
is 6.1 for H
p
H = pKa + log
2CO3
–
/HCO
buffer system.
3
−
HCO
3
means 6.1 + log 24 divided by 1.2 = 6.1 + log
HCO
20 = 6.1 + 1.3 = 7.4
METABOLIC ALKALOSIS
Primary base excess, i.e. HCO
27 mmol/L.
Causes:
¾
Repeated vomiting due to any cause. Commonly seen in
cases of pyloric stenosis. Here hypokalae mic alkalosis
occurs which is an important aspect for managing the
patient.
¾
Excess alkali ingestion, e.g. antacids.
¾
Cortisol excess either due to over administration or Cushing’s syndrome.
Features:
¾
Cheyne stokes breathing with period of apnoea of 5–30
seconds.
¾
Tetany due to alkalosis. More often latent tetany which
is revealed by Trousseau’s sign.
Investigations: Serum electrolytes, arterial blood gas
analysis.
Treatment:
¾
+
Normal saline or double strength normal saline IV infusion,
with slow IV potassium chloride 40 mmol/L in saline, slowly
under ECG monitoring.
¾
pH more than 7.7 causes life-threatening alkalosis which
requires rapid correction by infusing dilute hydrochloric
acid or ammonium chloride, however, with care and
monitoring.
–
. A standard bicarbonate above
3
RESPIRATORY ALKALOSIS
HENDERSON EQUATION (USED TO ASSESS
B
HYDROGEN ION CONCENTRATION)
HCO
HCO
HCO
23
α PCO
−
3
+
H
(nmol/L) = K ×
OR
K ×
Here constant K is 800 (for H2CO3 / HCO
Carbonic acid (H
2CO3
multiplied by partial pressure of CO
mL of blood; PCO
is 40 mmHg. H2CO3 = αPCO2 = 0.03 × 40 = 1.2
2
mL. Normal blood bicarbonate/HCO
× 1.2 divided by 24 = 40 mmol/L.
mmol/L
−
mmol/L
3
2
mmol/L
–
buffer).
) is solubility coefficient of CO2 in blood (α)
3
(PCO2). α is 0.03 mL/mmHg/100
2
level is 24 mmol/L. so H+ is 800
3
Arterial PCO
Causes:
¾
Hyperventilation during anaesthesia, due to head injury/
severe pain;
¾
Encephalitis, hypothalamic tumours, drugs like salicy-
is below normal.
2
High altitude; Hyperpyrexia;
Hysteria.
lates, due to cirrhosis of liver.
Features and management:
¾
Headache, tingling, circumoral anaesthesia, tightness in
chest, tetany, arrhythmias are the features.
¾
Low PaCO2, low HCO3, high alkaline pH are typical. Serum
will not fall below 15 mEq/L.
HCO
3
¾
It can be acute or chronic.
¾
It is managed by oxygen therapy, treating the cause,
acetazolamide in high altitude.
¾
Respiratory suppression due to alkalosis is treated by
CO
.
2
METABOLIC ACIDOSIS
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It is an excess acid or base deficit. A standard bicar bonate
below 21 mmol/
CAUSES OF METABOLIC ACIDOSIS
B
Increase in fixed acid:
Diabetic ketoacidosis; starvation; hypoxia
Renal insufficiency; cardiac arrest; excessive exercise
Intestinal strangulation. Here anion gap is increased
Loss of base:
Diarrhoea; ulcerative colitis
Gastrocolic or intestinal fistula
Ureterosigmoidostomy causes hyperchloraemichypokalaemic
acidosis. Here anion gap is normal.
L.
Features
Rapid, deep, noisy breathing (air-hunger)—Kussmaul’s
breathing.
Cold clammy skin, tachycardia, right heart strain, altered level
of consciousness.
Cardiac arrhythmias, hypotension.
Anorexia, muscle weakness, vomiting.
pH below 7.2 is dangerous and life-threatening.
Capillary stasis; Urine is strongly acidic; Low standard HCO
level; Base deficit.
It is evaluated by doing arterial blood gas analysis (ABG) which
shows low HCO
, low pH; anion gap; urinary anion gap (UAG).
3
Normal UAG is zero or positive. In metabolic acidosis due to GI
cause, UAG becomes negative due to increased NH
Cl excre-
4
tion; if it is due to renal cause, UAG will be positive.
Treatment
Correction of hypoxia.
50 mmol of 8.4% sodium bicarbonate infusion IV.
Sodium bicarbonate required in mEq/L = Body weight in kg
× Base deficit × 0.3.
Correction of electrolytes.
Specific treatment for lactic acidosis (type A [shock /
respiratory/CO/cyanide/anaemia]; type B [diabetes/hepatic/
toxins/drugs])—only careful use of NaHCO3 in severe cases,
dichloracetate which stimulates pyruate dehydrogenase to
reduce lactate.
Specific therapies for diabetic ketoacidosis, alcoholic
acidosis, aspirin poisoning, renal causes.
ASTRUP FORMULA
B
Total base excess or deficit = Base excess/base deficit × body weight
in kg × 0.3
RESPIRATORY ACIDOSIS
It is a feature of respiratory failure with high arterial PCO
causing fall in pH.
Causes:
¾
During and after anaesthesia.
¾
Chronic bronchitis; Emphysema; Thoracic diseases.
¾
Upper abdominal surgeries and diseases.
¾
Respiratory airway obstruction.
¾
Myasthenia gravis; Poliomyelitis.
¾
Stroke, infection, obesity, hypoventilation.
Features and treatment:
¾
Features of hypercapnia like dyspnoea, confusion,
psychosis, hallucinations, sleep disturbances, tremor,
jerks, and personality changes. CNS manifestations are
more severe in respiratory acidosis than in metabolic
acidosis as lipid soluble CO2 crosses blood-brain barrier
easily than HCO3.
¾
Acute respiratory acidosis is managed by oxygen
therapy, ventilator support. Oxygen therapy should
not be used in chronic hypercapnoea unless it is really
indicated as hypoxia stimulated respiration may be
suppressed. Alkali therapy also is not usually used
unless acidosis is very severe (below 7.15) or there is
severe bronchospasm.
ANION GAP
It is calculated estimation of the undetermined or unmeasured
3
anions in the blood.
It is (Na
Normal anion gap is 10–16 mmol/L.
Anion gap is charge difference between unmeasured anion
+
+ K+) — (HCO3¯ + Cl¯).
and cation. Important unmeasured anions are anionic protein,
phosphate, sulphate, organic acids. Unmeasured cations are
calcium and magnesium. Albumin is the main component of
anion gap. When albumin decreases by one g/dL then anion
gap decreases by 2 mEq/L.
Increased anion gap is seen in Normal anion gap is seen in
• Metabolic acidosis due to
ketoacidosis
• Lactic acidosis • GIT fistulae
• Poisoning • Hyperchloraemic acidosis
• Renal failure
• Diarrhoea
FLUID THERAPY
Osmolality of a solution is assessed by the amount of
solute dissolved in a solvent like water measured in
weight (kg).
Osmolarity of a solution is assessed by the amount of
solute dissolved in a solvent like water measured in
volume (litre).
2
Normal plasma Osmolality is 285 mOsm/kg (275–295).
91
CHAPTER 1F General Surgery: Electrolyte and Nutrition
Sir, it is plain that if he is too fat he has eaten more than he should have done.— Samuel Johnson
92
()()Glucosemg% Blood urea mg%
18 6
+
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OSMOLALITY IS CALCULATED BY TWO METHODS
B
× 10
3
mOsm/kg
a. Osmolality of plasma =
It is based on the fact that solution of 1 mOsmol/kg freezes at –
1.86°C; whereas normal plasma freezes at – 0.54°C.
b. Osmolality of plasma = 2 × (Na) +
It is based on the concentrations of major solutes in plasma.
054
186..
So sodium concentration contributes mainly to the osmolality.
SRB's Manual of Surgery
Colloidal osmotic pressure is difference in plasma osmotic
pressure and interstitial fluid pressure which is normally
25 mm Hg, which is mainly by plasma albumin concentration. Plasma proteins do not go out of capillary wall into the
interstitium.
Principles of Fluid Therapy
Indications
For rapid restoration of fluid and electrolytes in dehydration
due to vomiting, diarrhoea, shock due to haemorrhage or
sepsis or burns.
Total parenteral nutrition.
Anaphylaxis, cardiac arrest, hypoxia.
Post-gastrointestinal surgeries.
For maintenance, replacement of loss or as a special fluid.
Advantage
Controlled, accurate and adjustable, rapid and predictable.
PROBLEMS IN FLUID THERAPY
B
Needs hospitalisation; costly; needs asepsis
Fluid overload; pulmonary oedema and cardiac failure; infection
Thrombophlebitis; haematoma; cellulitis in local area
Pyrogenic reaction; air embolism; bacteraemia
Discomfort; poor patient acceptance
Calculation of Drop Rate of IV Fluids
b. Fluid volume in mL to be infused in one hour divided by four
= Number of drops/minute. Example: 100 m
L/hour means
25 drops/minute.
Number of microdrop/minute = Volume in mL/hour (50
c.
microdrop/minute = 50 m
Note:
• Daily requirement of sodium is 100 mEq; potassium is 60 mEq; calcium
is 5 mEq; magnesium 1 mEq.
• One litre of normal isotonic saline contains 154 mEq of sodium.
• Ringer’s lactate is the most physiological fluid (crystalloid) containing
sodium—130 mEq/L; potassium—4 mEq/L; chloride—109 mEq/L;
lactate (bicarbonate)—28 mEq/L; and calcium—3 mEq/L. It should be
avoided in liver failure patients. As it does not contain glucose it can be
used in diabetics.
• Other crystalloid fluids—normal saline, dextrose saline, 5% dextrose,
isolyte P, isolyte G, isolyte M.
• Colloids are of large molecules which shift the fluid from interstitial
compartment to intravascular compartment and are used as plasma
expanders. Haemaccel, hetastarch, pentastarch, dextran 40/70 are
colloids.
• Special purpose fluids are sodium bicarbonate 7.5% and 8.4% used in
metabolic acidosis, forced diuresis, hyperkalaemia; mannitol 10/20%
used as an osmotic diuretic agent; hypertonic saline 1.6%, 3%, 5%
and 7.5% used in hyponatraemia of different severity; albumin 4.5% as
plasma expander; albumin 20% in severe hypoalbuminaemia.
• Weight loss more than 10% of individual’s weight in 6 months is called
as significant weight loss.
• Body mass index (BMI) is body weight in kilograms divided by height
in meters squared. BMI less than 18.5 signifies nutritional impairment
and below 15 signifies severe malnutrition.
• Daily fluid loss from kidneys is 1500 mL; from lungs is 400 mL; from
skin is 800 mL; from stool is 60–150 mL.
• Energy requirement per day is 20–30 kcal/kg, i.e. around 2000 kcal/
day total.
• Glucose requirement is 200 g per day; fat requirement is 200 g per
week; nitrogen (protein) requirement is 0.15 g/kg per day. Nitrogen
need increases to 0.25 g/kg/day in hypercatabolic status.
• Transit time is rapid in jejunum; three times slower in ileum; still slower
in colon.
• Fluid absorption capacity is 40% in jejunum; 70% in ileum; 90% in colon.
• Electrolyte and vitamin B
occurs in ileum and so ileum is more important than jejunum.
L/hour).
absorption and enterohepatic circulation
12
1 mL =16 drops in usual drip set. For microdrip set one mL =
60 drops.
a. Quantity of fluid required in liters per day × 10 = Drop rate/
minute. 2.5 litres is usually used quantity of fluid/day. So
2.5 × 10 = 25 drops/minute.
Crystalloids
Crystalloids are aqueous solutions of mineral salts or other water
soluble molecules. They are used mainly to improve the volume
and electrolyte supplementation.
Crystalloids Commonly Used
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Type Content Indications Contraindications and problems
5% dextrose One litre contains 50 gram of
glucose. It is hypotonic; pH is
4.5; provides 170 kcal/
Normal saline (isotonic
saline— 0.9% NaCl/ NS).
3% normal saline
(hypertonic) contains
513 mEq/L of sodium; is
used in hyponatraemia
due to SIADH or water
intoxication or severe
hyponatraemia
Dextrose (5%) with
normal saline (0.9
NaCl), (DNS)
Dextrose with 0.45%
normal saline
Ringer’s lactate
(Hartmann’s/ balanced
salt) solution
Isolyte M (Maintenance) One litre contains 50
One litre contains 154 mEq
each of sodium and chloride
One litre contains 50 grams
of glucose, 154 mEq each of
sodium and chloride; pH 4.2;
osmolarity 585 mOsm/litre
One litre contains 50 grams
of glucose; 77 mEq each of
sodium and chloride
One litre contains 130 mEq
sodium (as sodium lactate);
109 mEq of chloride; 4
mEq potassium; 28 mEq
of bicarbonate; 3 mEq of
calcium. It is devoid of
glucose
grams of glucose; 40 mEq
sodium; 38 mEq chloride;
35 mEq potassium; 15 mEq
phosphate; 20 mEq acetate
L
Used in pre- and postoperative fluid
therapy; 5% and 10% dextrose is used
as protector of liver in obstructive
jaundice, preoperative preparation in
biliopancreatic surgeries, clear toxic
substances. It is useful in correction of
hypernatraemia due to pure water loss
like diabetes insipidus, excess use of
electrolytes; 5% dextrose is infused with
frusemide
• It mainly exists in ECF to maintain
osmolality; it increases the
intravascular volume and is so very
useful to stabilize the blood pressure
in hypovolaemia
• It is used in diarrhoea, vomiting,
excessive sweating; in treatment of
alkalosis; in hyponatraemia; diabetic
ketoacidosis; hypercalcaemia; brain
surgery and injuries
• It is used in giving wash to body
cavities like peritoneum or any
wounds (warm NS)
• Many drugs are given using NS as
vehicle
• It is safer in renal failure as it does not
contain potassium
It corrects hypovolaemia and
hyponatraemia. It is used alkalosis due
to vomiting and nasogastric aspiration
It is commonly used in fluid therapy;
treatment of severe hypernatraemia as
it corrects it gently; to avoid cerebral
oedema. It is used in maintenance
therapy and in postoperative period
• It is used in corrections of severe
hypovolaemia as it expands
intravascular volume rapidly
• It is useful in managing metabolic
acidosis as lactate in liver is
metabolized to bicarbonate
• It is useful fluid for therapy in postoperative period, burns, diarrhoea.
It also corrects hypokalaemia. It
maintains normal ECF fluid and
electrolyte balance
• In diabetic ketoacidosis it provides
glucose free fluid
• It gives calories, water, electrolytes,
pH. Rich potassium in it is useful in
correcting the hypokalaemia provided
renal function is good. It can correct
acidosis also
• It is useful in diarrhoea, bilious
vomiting
Cerebral oedema as it is
hypotonic; cranial surgeries;
stroke; hypovolaemic shock as it
may cause hyperglycaemia and
osmotic diuresis; hyponatraemia;
water intoxication; it should not
be used for rapid correction of
hypernatraemia; diabetes and
hyperglycaemia.
Note: Intravenous administration of
dextrose can cause low potassium,
magnesium and phosphate; and
causes thrombophlebitis
• It is avoided in hypertension, preeclampsia, elderly, dehydration
with hypokalaemia
• Large volume infusion may
cause sodium retention and
hyperchloraemia
It is not used in cardiac and renal
failure. Used in shock but not used
in severe hypovolaemic shock
It is not used in hyponatraemia, and
in diarrhoea and vomiting
• It can cause lactic acidosis, so
contraindicated in hypoxia, severe
shock, liver diseases, in vomiting
and nasogastric aspiration, in
metabolic alkalosis
• It cannot be used along with
blood transfusion as calcium
in Ringer lactate can bind with
citrate of transfusing blood
precipitating clotting of the donor
blood. Blood products and RL
cannot be infused simultaneously
It is not useful in correcting
hyponatraemia as sodium
concentration in it is low
Contd...
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CHAPTER 1F General Surgery: Electrolyte and Nutrition
Less you eat, you are malnourished. More you eat, more you are diseased.
94
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Contd...
Isolyte G (Gastric) • One litre contains 50
grams of glucose, 63
mEq of sodium, 130 mEq
of chloride, 17 mEq of
potassium, 69 mEq of
ammonium
• Gastric juice contains
nearly similar contents
of Isolyte G. In liver
ammonium converts into
urea and hydrogen ion.
Hydrogen ion neutralizes
SRB's Manual of Surgery
Isolyte E (Extracellular
replacement)
Isolyte P (
Paediatric) One litre contains 50 grams of
alkalosis
One litre contains 50 grams
of glucose; 140 mEq of
sodium; 103 mEq of chloride;
5 mEq of calcium; 10 mEq
of potassium; 47 mEq of
magnesium; 3 mEq of acetate;
8 mEq of citrate
glucose; 25 mEq of sodium;
22 mEq of chloride; 20
mEq of potassium; 3 mEq
of magnesium; 23 mEq of
acetate
Gastric juice vomiting or continuous
nasogastric aspiration which causes
hypochloraemic, hypokalaemic,
metabolic alkalosis which is corrected by
Isolyte G
It is used mainly to replace extracellular
fluid. It contains double the ECF
concentrations of potassium and acetate
(rest similar). It gives energy, water,
magnesium, corrects acidosis
It is used in fluid therapy in paediatric
age group
It is not used in metabolic alkalosis
due to vomiting, due to diuretics
It is not used in hyponatraemia,
renal failure, hyperkalaemia,
hypovolaemic shock
Colloids
Colloids are of up to 20 u sized large molecules, which retain in the intravascular space for longer time and so raise the intravascular volume (3 times > than crystalloids). They improve cardiac output but not oxygen carrying capacity. Colloids should maintain
oncotic pressure equal to that of plasma; should be stable and inert; non-toxic, non-antigenic, non-pyrogenic; should be easily
sterilisable; should not interfere with blood grouping.
Colloids Commonly Used
Colloid Content Indications Problems
Albumin (Heat treated human
albumin)
It maintains 75% of plasma
oncotic pressure. It is the vehicle
to transport many low molecular
substances including drugs
Dextran
Bacteria (Leuconostoc
mesenteroides and
Streptococcus mutans)
incubated in sucrose media
produces complex branched
glucan polymers as dextrans
• 5% human albumin (50 grams/L) has
colloid osmotic pressure of 20 mm
of Hg (that of plasma pressure); its
effects last for 18 hours. It increases
the volume 1:1
• 25% human albumin (250 grams/L)
has got colloid osmotic pressure of
70 mm Hg; expands the intravascular
volume 5 times more by shifting the
fluid from extravascular (interstitial)
space to intravascular space; should
not be used in hypovolaemia
• Dextran was first discovered by Louis
Pasteur in wine
• It is used to expand intravascular
volume
• Dextran 70 has got molecular weight
of 70,000. Its excretion through
kidney is poorer and so remains in
the blood for weeks. It is used as 6%
solution
• It is used—when rapid
plasma volume expansion
is needed like burns in
correcting hypovolaemia
sometimes; in plasmapheresis as exchange fluid
• 500 m
• It is used as volume
• It is also used as
L of 5% albumin is
infused at a rate of 2 mL
per minute
expander in hypovolaemia.
It increases the blood
sugar also
antithrombotic agent.
Dextran is a plasminogen
activator; inhibits
erythrocyte aggregation
and platelet adhesiveness
• It is contraindicated in
cardiac failure, anaemia
• It can cause allergic
reactions, nausea, febrile
reactions
• It causes electrolyte
disturbances and
hyponatraemia
• It causes acute renal
failure by direct toxicity to
glomerulus and tubules
and by intraluminal
hyperviscosity
Contd...
Contd...
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Haemaccel
L bottle with active
500 m
ingredient polygeline
Hetastarch (hydroxyethyl starch)
It is nonionic starch derivative,
which is ethoxylated
amylopectins which is a plasma
volume expander
Pentastarch
It is a subgroup of hetastarch
with five hydroxyethyl groups
with 50% esterification. It is a
low molecular weight derivative;
it is more effective plasma
volume expander
• Dextran 40 has got molecular
weight of 40, 000. It is used as 10%
solution; its action is faster but
shorter than dextan 70 due to faster
excretion through kidney compared
to dextran 70
• 1000 m
• It also contains sodium and chloride
• Haemaccel should be stored in
• Haemaccel does not induce antibody
• It is a synthetic colloid available as
• Total dose per day should be 1500
It is available as 3%, 6% and 10% in
normal saline
L of haemaccel contains
polypeptides of degraded gelatin
(origin—bovine bone; cross
linked via urea bridges), 35 grams
(equivalent of 6.3 gram of nitrogen)
of 145 mmol (0.85 gram); calcium
6.25 mmol (0.25 gram); potassium
5.1 mmol (0.20 gram); traces of
phosphate, sulphate and anionic
polypeptides. Its molecular weight is
30,000 with 1.7 viscosity
2–25°C
formation
6% solution in 0.9% normal saline
(30 gram hetastarch in 500 mL of
isotonic saline). It is administered
IV only using infusion pump; 20
mL/kg/hour; it is stored in room
temperature. It is enzymatically
degraded and causes rise in serum
amylase level
mL only
• It improves
microcirculation and blood
flow
• Dextran 40 is commonly
used
• It is used for rapid volume
replacement in circulatory
collapse like shock, burns
and trauma. It is infused
rapidly at a rate of 125
drops/minute. H2 blocker
like cimetidine or ranitidine
should be given along with
haemaccel as it releases
histamine
• It improves the plasma
volume rapidly and
remains like that for 5
hours
• It will not interfere with
coagulation, blood
grouping and cross
matching
• It is used also in heart lung
machine
• Haemaccel can be mixed
with other IV fluids and
drugs
• Haemaccel can be infused
up to 2000 m
• It is used in
hypovolaemia—shock,
burns, trauma.
• It is also used in
leukapheresis
• It is nonantigenic; does
not interfere with blood
grouping
• It shows greater plasma
volume expansion for
longer period compared to
5% albumin
• It is used in hypovolaemia
• It is useful in cardiac
surgeries
L
• It should be used
carefully in diabetic
patients
• It can cause pulmonary
and or cerebral oedema
due to hyperosmolarity
• It can cause anaphylaxis
(being a potent
antigenic)
• It can interfere with blood
grouping and cross
matching
• It prolongs the bleeding
time and so may
precipitate bleeding
Rapid histamine release and
anaphylactoid reaction
• Anaphylactoid reactions
can occur
• Renal impairment should
be observed
• It has no O
capacity; so should not
allow haematocrit to fall
below 30%
• Impairment of
coagulation is possible
carrying
2
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CHAPTER 1F General Surgery: Electrolyte and Nutrition
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