neurology of electrolyte imbalance
TRANSCRIPT
Dr Sankalp Mohan
Senior Resident
Dept of Neurology
Govt Med college,Kota
SODIUM - Hyponatremia
-Hypernatremia
POTASSIUM - HypokalemiaHyperkalemia
CALCIUM - Hypercalcemia Hypocalcemia
MAGNESIUM - Hypomagnesemia Hypermagnesemia
Sodium Disorders
Abnormalities in water homeostasis that lead to changes in the relative ratio of Na+ to body water
Water intake and circulating AVP
AVP secretion is stimulated as systemic osmolalityincreases above a threshold level of 285 mosmol/kg
Thirst and thus water ingestion also are activated at 285 mosmol/kg,
Hyponatremia DEFINITIONS
Defined as sodium concentration < 135 mEq/L
MILD – 130 -135 mEq/L
MODERATE – 125-129 mEq/L
PROFOUND - <125
ACUTE - <48 HRS . CHRONIC > 48 HRS
EPIDEMIOLOGY incidence is 0.97% and prevalence is 2.48% in
hospitalised
Age - more common in elderly persons
Sex- No sex prediliction. Symptoms more in younger women
Mortality – Severe hyponatremia –high mortality .
less than 105 mEq/L, the mortality is over 50%
Overview
normal
measure lipids, proteins
volume expanded
CHF
Cirrhosis
nephrotic
Volume Depleted
adrenal insuff
extrarenal losses
renal salt wasting
Euvolemic
polydipsia
SIADH
low (<280)
Assess ECF Clinically
High (>>280)
glucose
mannitol, sorbitol, glycine
serum osm (measured)
Pseudohyponatremia and Translocational hyponatremia Pseudohyponatremia -high concentrations of lipids
or proteins in the blood interfere with the accurate measurement of sodium
Measurement of serum osmolarity
---hypotonic, isotonic or hypertonic,
- High osmolarity – glucose or hypertonic solutions
HYPONATREMIAHYPOVOLEMIC
EUVOLEMIC
HYPERVOLEMIC
Hypovolemic Hyponatremia
Hypovolemia causes a marked neurohumoralactivation, increasing circulating levels of AVP
increase in circulating AVP helps preserve blood pressure via vascular and baroreceptor V1A receptors and increases water reabsorption via renal V2 receptors
Nonrenal causes –
gastrointestinal (GI) loss (vomiting, diarrhea, tube drainage, etc.) and insensible loss (sweating, burns) of Na+-Cl– and water
urine Na+ concentration is typically <20 mM.
Renal causes –
deficiency in circulating aldosterone
SalT-losing nephropathies include reflux nephropathy, interstitial nephropathies, post-obstructive uropathy, medullary cystic disease, recovering ATN
Thiazide diuretics
"cerebral salt wasting – volume depleted state
most patients with CSW have elevated circulating levels of ADH
Hypervolemic Hyponatremia
proportionately greater increase in total body water, leading to a reduced plasma Na+ concentration
congestive heart failure (CHF), cirrhosis, and nephroticsyndrome
Arterial underfilling
Urine Na+ concentration is typically very low
Euvolemic Hyponatremia moderate to severe hypothyroidism - after the
achievement of a euthyroid state
secondary adrenal insufficiency due to pituitary disease , Glucocorticoid
syndrome of inappropriate antidiuresis –
erratic AVP secretion is seen in about a third of patients
CAUSES OF SIADH
SIADH Diagnosis of Exclusion CRITERIA Laboratory findings : Euvolemic hyponatremia <134 mEq/L, and POsm <275 mOsm/kg Urine osmolality >100mOsm/kg of water during hypotonicity[2]
Urine sodium concentration >40 mEq/L with normal dietary salt intake
Other findings: Clinical euvolemia without edema or ascites Low blood urea nitrogen (BUN) Normal serum creatinine Low uric acid Normal Acid-Base, K+ balance Normal Adrenal, Thyroid function
Low Solute Intake and Hyponatremia –
very low intake of dietary solutes-
Alcoholics –beer potomania
Approach to hyponatremia
Pathogenesis of cerebral Edema
brain needs ∼48h to adapt to a hypotonic environment
once adaptation is completed, brain cells can again sustain damage if the serum sodium concentration increases too rapidly.
breakdown of the myelin sheath insulating individual neurons can result in what is called the osmotic demyelination syndrome
CLINICAL FEATURES Acute or Chronic
incidental
many patients present due to manifestations of other medical comorbidities
Mild – nausea malaise ,lethargy,concentrationdifficulties
DIAGNOSISSTEP 1
STEP 2 – To Exclude pseudohyponatremia or hypertonic hypernatremia
Non hypotonic hypernatremia does not cause brain edema .
Psuedohyponatremia – laboratory artefact .use of ion specific electrodes
MEASURE SERUM OSMOLARITY – variable
Other – judge clinical scenario –like mannitol infusion
measure glucose.lipids ,proteins urea and
For hyperglycemic
hyponatremia
- or Add 2.4 mmol/l for every 100 mg/dl glucose
Volume status measurement . However not very accurate – low sensitivity and specificity
Measurement of urine osmolarity .less than 100 –excess water intake (polydipsia)
Urine sodium concentration - urine sodium concentration ≤30mmol/l suggests low effective arterial blood volume
Patient on diuretics – interpretation difficult
TREATMENT
Hyponatraemia with severe symptoms
Prompt infusion of hypertonic saline 3 % or 1.6 %
Change in Serum Sodium = (Fluid Sodium - Serum Sodium) / (Total Body Water + 1)Total Body Water = (Wt in kg * % Water)
hyponatremia should be corrected at a rate not exceeding 10 mmol/L/24 h or 0.5 mEq/L/h;
Chronic hyponatremia - plasma Na+ concentration is corrected by >8–10 mM within the first 24 h and/or by >18 mM within the first 48 h
Hypovolemic hyponatremia will respond to intravenous hydration with isotonic normal saline,
Hypervolemic hyponatremia due to congestive heart failure often responds to improved therapy of the underlying cardiomyopathy
CHRONIC HYPONATREMIA Fluid restriction
Vassopressin-2 receptor antagonists
Conivaptan and tolvaptan - fda approved
indicated for hypervolemic and euvolemichyponatremia (ie, serum Na level < 125 mEq/L )
Demeclocycline- a 2–3 day delay in onset .Nephrotoxic
Hypernatremia
plasma Na+ concentration to >145 mM
losses of H2O in excess of those of Na+.
or iatrogenic administration of excess Na+
ETIOLOGY Elderly individuals with reduced thirst
renal water loss include osmotic diuresis secondary to hyperglycemia, excess urea, postobstructive diuresis, and mannitol
Insensible losses of water may increase in the setting of fever, exercise, heat exposure, severe burns,
Diarrhea is the most common gastrointestinal cause of hypernatremia
Nephrogenic DI (NDI) is characterized by renal resistance to AVP
Central DI
Clinical Features Altered mental status is the most common
manifestation, ranging from mild confusion and lethargy to deep coma
parenchymal or subarachnoid hemorrhages and/or subdural hematomas – more in children
Osmotic damage to muscle membranes also can lead to hypernatremic rhabdomyolysis
chronic hypernatremia are less likely to develop severe neurologic compromise.
APPROACH TO HYPERNATREMIA
Treatment: Hypernatremia replacing the calculated free-water deficit over 48 h.
no more than 10 mM/d
free water orally or through RT
free water in dextrose-containing IV solutions
hypotonic saline solutions (1/4 or 1/2 normal saline);
Patients with central DI -ddavp
NDI due to lithium may reduce their polyuria with amiloride (2.5–10 mg/d),
HYPOKALEMIA
ETIOLOGY
CLINICAL FEATURES Acute onset quadriparesis
Consiousness preserved
Respiratory and Bulbar involvement – rare and mild
Attacks of periodic paralyses
Examination- Proximal > distal muscle weakness,Legsmore than arms,hypotonia, hyporeflexia
In between attacks examination is normal
Progressive Proximal Myopathy develops usually at the age of 50 years
Paralytic Ileus
Associated features – metabolic alkalosis ,polyuria
Approach in general
- To exclude pseudohypokalemia
- Redistribution hypokalemia
- Urine potassium, Acid base status
INVESTIGATIONS Serum potassium – mean 2.4 . Hypokalemic PP- K
normal between attacks
ECG changes of Hypokalemia – ST depression,U waves ,decreased T wave amplitude
T3,T4,TSH
ABG ,Other Electrolytes –Ca ,Po4
CPK may be elevated
Electromyography (EMG)- during attack
CMAP may be reduced
TREATMENT
ACUTE TREATMENT – Oral potassium chloride 60 -120 meq incrementally
30 meq orally every 30 min
Iv potassium is reserved for cardiac arrhythmia or airway compromise due or accessory respiratory muscle paralysis.
iv dose is usually 20–40 mmol of K+-Cl– per liter;
Very severe – iv line -10-20 meq/hr with iv monitoring
Cardiac monitoring recommended
HYPERKALEMIA plasma potassium level of 5.5 mM
10% of hospitalized patients . 1 % more than 6 mM
Pseudohyperkalemia
Redistribution and Hyperkalemia
Excess Intake or Tissue Necrosis
Hypoaldosteronism and Hyperkalemia
Renal Disease and Hyperkalemia
Medication-Associated Hyperkalemia
CLINICAL FEATURES Cardiac arrhythmias associated with hyperkalemia
include sinus bradycardia, sinus arrest, slow idioventricular rhythms, ventricular tachycardia, ventricular fibrillation
begins in the legs, thighs, and lower back and spreads to the hands, forearms, and shoulders
Respiratory muscles are usually spared
TREATMENT Immediate antagonism of the cardiac effects of
hyperkalemia - 10 mL of 10% calcium gluconate (3–4 mL of calcium chloride), infused intravenously over 2 to 3 min with cardiac monitoring
Rapid reduction in plasma K+ concentration by redistribution into cells - 10 units of IV regular insulin followed immediately by 50 mL of 50% dextrose
B2-agonists
Intravenous bicarbonate has no role
Removal of potassium - SPS 15-30 g/day
Diuretics ,dialysis
Calcium abnormalities Calcium stabilizer of electrically exictable tissue
HYPERCALCEMIA
Clinical Manifestations Mild hypercalcemia (up to 11–11.5 mg/dL) is usually
asymptomatic CNS -vague neuropsychiatric symptoms, including trouble
concentrating, personality changes ,proximal muscle fatigue
Occasionally symptoms like MND, bradykinetic disorder like parkinsonism
OTHER -peptic ulcer disease or nephrolithiasis, and fracture risk
severe hypercalcemia (>12–13 mg/dL), particularly if it develops acutely, may result in lethargy, stupor, or coma, gastrointestinal symptoms
bradycardia, AV block, and short QT interval
DIAGNOSIS IONISED calcium and Albumin levels
Correction - adding 0.2 mM (0.8 mg/dL) to the total calcium level for every decrement in serum albumin of 1.0 g/dL
PTH level .phosphate levels
Increased PTh – primary hyperparathyroid ..
Decreased pTH with hypercalcemia – malignancy
Serum Vit D3 levels – granulomatous disorders
TREATMENT MILD / asymptommatic – does not require therapy Severe symptommatic- 4–6 L of intravenous saline may be
required over the first 24 h . may be given with loop diuretics Severe hyperparathyrid/malignancy – Zoledronic acid (e.g., 4 mg intravenously over 30 min),
pamidronate (e.g., 60–90 mg intravenously over 2–4 h), and etidronate (e.g., 7.5 mg/kg per day for 3–7 consecutive days)
25(OH)2D-mediated hypercalcemia –GLUCOCORTICOIDS – iv Hydrocortisone , oral prednisolone
HYPOCALCEMIA
Clinical Manifestations may be asymptomatic if mild or chronic
Moderate to severe hypocalcemia is associated with paresthesias, usually of the fingers, toes, and circumoralregions – lips tongue
Cramps ,fasciculations ,spasms
Chovstek s sign
Trosseau sign
Severe hypocalcemia can induce seizures- generalised or focal
carpopedal spasm. choreoathetosis
, bronchospasm, laryngospasm
DIAGNOSIS Ionised calcium ,albumin, phosphorus, and
magnesium levels.
PTH levels and Vit D levels
ECG – QT prolongation
EEG –generalised /focal slowing or triphasic waves –s/o metabolic encephalopathy
TREATMENT Acute, symptomatic hypocalcemia –
calcium gluconate, 10 mL 10% wt/vol (90 mg or 2.2 mmol) intravenously, diluted in 50 mL of 5% dextrose or 0.9% sodium chloride, given intravenously over 5 min
constant intravenous infusion - calcium gluconate or 900 mg of calcium in 1 L of 5% dextrose or 0.9% sodium chloride administered over 24 h
Chronic hypocalcemia due to hypoparathyroidism is treated with calcium supplements (1000–1500 mg/
of vitamin D (50,000 U, 2–3 times per week for several months)
MAGNESIUM
NORMAL mg - of 0.7–1 mmol/L (1.5–2 meq/L )
crucial for normal neuromuscular activity
HYPOMAGNESEMIA
ETIOLOGY -intestinal malabsorption; protracted vomiting, diarrhea, or intestinal drainage; defective renal tubular magnesium reabsorption
HYPOMAGNESEMIA
Symptoms similar to hypocalcemia
Hypomagnesemia may cause generalized alterations in neuromuscular function, including tetany, tremor, seizures, muscle weakness, Headache blurred vision
ataxia, nystagmus, vertigo, apathy, depression, irritability, delirium, and psychosis ,auditory changes
sinus tachycardia, other supraventricular tachycardias, and ventricular arrhythmias
prolonged PR or QT intervals, T-wave flattening
Treatment: Hypomagnesemia Mild, hypomagnesemia -with oral magnesium salts
[MgCl2, MgO, Mg(OH)2] in divided doses totaling 20–30 mmol/d (40–60 meq/d
severe hypomagnesemia -with IV MgCl2, continuous infusion of 50 mmol/d (100 meq Mg2+/d) if renal function is normal. Iv Mgso4 can cause hypocalcemia
Hypermagnesemia rarely seen in the absence of renal insufficiency
CLINICAL FEATURES - vasodilation and neuromuscular blockade >2 mmol/L
Hypotension that is refractory to vasopressors
respiratory failure, paralysis, and coma, with hypoactive tendon reflexes, at serum magnesium levels >4 mmol/L
prolongation of PR, QRS, and QT intervals; heart block
TREATMENT - Use of magnesium-free cathartics or enemas , vigorous iv hydration ,hemodialysis
THANK YOU
REFERENCES Clinical practice guideline on diagnosis and
treatment of hyponatraemia - Eur J Endocrinol March 1, 2014 170G1-G47
New European guidelines management of Hyponatremia 2014
Neurology Clinics – neurology and systemic disease Feb 2010 .vol28
Harrison s principles of internal medicine 18 th