Hypokalaemia

(Serum potassium level-<3.5mEq/L)

Causes:

• Vomiting, diarrhoea
• Loop diuretics
• Inadequate intake
• Diuretic phase of ARF
• On IV fluids without potassium supplementation
• Hypomagnesemia
• Insulin
• Drugs like salbutamol, terbutaline, aminophylline, amphotericin B
• Increased blood cell production. Ex: Treatment of megaloblastic anemia, bone marrow recovery after chemotherapy etc

ECG Changes:

• T wave flattening/ inversion
• ST depression
• Low voltage QRS
• Bradycardia (Prolonged PR interval)

Clinical features:

• Muscle weakness
• Absent deep tendon reflexes
• Diminished bowel sounds (Paralytic ileus)

Management:

• Mild(3-3.5mEq/L) 
  • Potassium rich diet- Fruits, tender coconut
  • Kesol/ Potchlorsyrup-2tspwith50mlwater-TDSorPotratetablets
• Severe(<3mEq/L)
  • Never give potassium as bolus
  • KCl- 40-60mEq in 500ml NS over 6hrs
  • Avoid dextrose drip
  • Correct hypomagnesemia- MgSO4- 50%- 2ml- in100ml NS over 2-3hrs -6^thhrly. Magnesium infusion is contraindicated  in case of renal failure.

Hyperkalaemia

(Serum potassium level >5.5mEq/lit)

Causes: 

• Renal failure
• Haemodialysis
• Unmonitored potassium supplementation
• Drugs: potassium sparing diuretic, ACEinhibitors, Betablockers
• Increased cell lysis in the body- Tumour lysis syndrome, haemolysis
• Acidosis
• Hyperglycaemia

Spurious causes of hyperkalemia:

• Hemolysis
• Leucocytosis
• Thrombocytosis
• Repeated clenching of fist during phlebotomy
• Traumatic venepuncture

Clinical features:

• Weakness later leading to flaccid paralysis
• Ventricular fibrillation, bradycardia or asystole

ECG Changes:

• Tall and peak T wave
• Wide QRS complex
• Absent P wave
• Need to rule out pseudohyperkalemia which occurs due to hemolysed sample, tight tourniquet or marked leucocytosis/ thrombocytosis

Management:

• Stop all potassium containing foods and fluids (Fruits, tender coconut water, fresh vegetables, coffee)
• Stop medications that increase potassium levels
• Potassium binding resin: ResoniumA -15-30gm-TDS-PO
• Mild(5-6mEq/L)
  • Correct acidosis: 8.4% HCO3-100mlStat-IV
  • Inj.Furosemide:40-80mg-IV
• Moderate(6-8mEq/L)
  • 50% Glucose- 50ml with 8units of plain insulin over 1hr OR 5% dextrose- 500ml with 8units plain insulin over 6hrs.
  • In children- 1gm/kg Glucose with 0.3units/kg plain insulin- Infused over 30min
  • Beta2 Agonist Nebulization over 10min (Salbutamol)
• Severe (>8mEq/L)/ If ECG changes
  • To reverse cardiac effects (To decrease membrane excitability): 10% calcium gluconate-10ml-IV over 30min. Repeat after 5min, till ECG normalizes. Avoid this in case of tumour lysis syndrome.
  • Haemodialysis: If all above measures fail/ Patient has renal failure

Hyponatremia

(Serum sodium levels<135mEq/L)

Clinical Features:

• >125mmol/L-Asymptomatic
• 115-125mmol/L-Lethargy, weakness, ataxia, vomiting
• <115mmol/L-Confusion, headache, convulsions, coma (Due to cerebral edema)- These are common with patients with acute hyponatremia.

Pathophysiology:

• Upon excess water ingestion, there is suppression of both thirst and ADH (vasopressin).
• ADH is produced from hypothalamic neurons that receive inputs from 
  • Osmoreceptors which respond to S. Sodium concentration
  • Baroreceptors which respond to status of circulation
• High levels of ADH results in insertion of water channels in collecting duct, which results in reabsortion of water.

Causes: 

Hypotonic hyponatremia (Increased water intake or impaired water excretion):

• ADH Levels are normal (Unimpaired urine dilution)
  • Primary polydipsia due to psychosis
  • Low dietary salt intake
• Impaired urine dilution but normal suppression of ADH
  • Advanced renal impairment
  • Diuretic induced hyponatremia
• Impaired urine dilution due to unsuppressed ADH secretion
  • Reduced effective arterial blood volume: Ture volume depletion (hypovolemic hyponatremia), Heart failure and cirrhosis (Hypervolemic hyponatremia), Addison’s disease
  • Syndrome of inappropriate ADH secretion(SIADH)- Euvolemic hyponatremia 
    • Pneumonia, Tuberculosis, Empyema
    • AIDS
    • Solid tumours- mainly lung
    • CNS disturbances: CVA, SAH, SDH, Meningitis
    • Post surgery
    • Drugs: Phenothiazines, Carbamazepine, Tricyclic antidepressants, Vincristine, Cyclophosphamide, Morphine
    • Hormonal deficiency: Secondary adrenal insufficiency, hypothyroidism
    • Hormone administration: Vasopressin, desmopressin, oxytocin
• Impaired urine dilution due to abnormal V2 receptor (Nephrogenic SIADH)
• Abnormally low osmostat
  • Acquired reset osmostat of chronic illness
  • Genetic reset osmostat
  • Reset osmostat of pregnancy
• Exercise induced hyponatremia
• Cerebral salt wasting
• Other causes
  • Hyperglycaemia, hyperlipidaemia, hyperproteinaemia

Diagnosis of SIADH

• Decreased sodium levels
• Decreased urea, creatinine, uric acid
• Decreased serum osmolality
• Increased urine sodium (>20mEq/L)
• Increased urine osmolality
• No edema/ Dehydration clinically
• Normal thyroid and adrenal functions

Treatment: (Correct hyponatremia only if patient is symptomatic/ Na levels <120mEq/L)

• Treatment depends on the cause
• Send RFT including electrolytes, urine osmolality and urinary sodium, thyroid function tests and get reference of nephrologist/ intensivist.
• Normal saline if there is hypovolemia/ dehydration. Avoid this in edematous patients and SIADH patients.
• Water restriction to 500ml to 800ml per day/ Diuretics if there is hypervolemia/ edema
• If hyponatremia is due to decreased salt intake, increase dietary salt intake, up to 15 gm/day, and increase protein intake. Avoid salt in patients with edema.
• Correction with hypertonic saline:
  • 3% NS, only if the patient is drowsy/ unconscious/ seizures-First 100 ml infusion may be given over 10 min. Further doses must be prescribed by nephrologist/ intensivist after calculating sodium deficit)
  • Correction should be very slow - 0.5-1 mEq/L/hr or  4-8 mEq/day
  • Rapid correction leads to central pontine myelinolysis (Flaccid quadriplegia)
•  IV-Frusemide - 20 mg
• Correction of hypokalemia by potassium replacement
• Chronic cases:
  • Demeclocycline - PO - 600-1200 mg/day - in 2-3 divided doses for 2-3 weeks
  • Vasopressin Receptor antagonists: Tolvaptan - 15 mg - PO - OD (Slowly increase to 30 mg)
• In all resistant cases, rule out hypothyroidism and hypoadrenalism

Hypernatremia 

(Sodium levels- >145mmol/L)

Causes:

• Decreased oral intake with fluid loss
• Hypotonic fluid loss - Excess sweating, diarrhea, vomiting, Diabetes insipidus, osmotic diuretic agents, hyperglycemia, hypercalcemia, chronic renal failure
• Increased salt load - Cushing syndrome, hyperaldosteronism, increased salt intake

Clinical features:

• Increased thirst
• Weakness, lethargy
• Irritability
• Altered mental status
• Ataxia, tremors
• Focal neurological deficits
• Seizures
• Coma

Treatment (Treat only if patient is symptomatic)

• Send Spot Urine/Plasma osmolality and urinary sodium and take reference of nephrologist/ intensivist
• Correction with IV 5% Dextrose/0.45% saline
  • Correction is given up to 140 mEq/L
  • Calculation of water deficit
  • Deficit = Desired total body water - Current total body water
  • Current total body water = 0.6 x Weight
  • Desired total body water = (S. Sodium x Current total body water) / (Ideal S. Sodium)
• Rate of correction (5% dextrose)
  • 50% of deficit should be corrected in 24 hrs
  • Remaining 50% should be given over the next 24 hrs
  • Rapid correction can lead to cerebral edema
• Change in plasma osmolality not to exceed 2 mEq/L/hr
• Change in S. Sodium not to exceed 1 mEq/L/hr
• Oral fluids can be started once the patient is better

Hypocalcaemia

(Calcium<8.7mg/dL)

Causes:

• Sepsis
• Alkalosis
• Drugs
• Renal failure
• Pancreatitis
• Tumour lysis syndrome
• Rhabdomyolysis
• Hypoparathyroidism
• Hypomagnesemia

Clinical Features:

• Tingling and numbness around mouth
• Tetany/ carpopedal spasms (Trousseau's sign)
• Hyper-reflexia
• Convulsions
• Laryngospasm
• Chvostek's sign (Percussion over pre-auricular region causes facial muscle twitching)
• ECG-Prolonged QT interval

Note:

• If albumin is low, hypocalcaemia may be over estimated
• With every gram decrease in albumin level, calcium level apparently decreases by 0.8mg/dL. Hence add 0.8mg/dl to S. calcium level for every 1gm/dL by which the S. Albumin level is below 4gm/dL

Management (Treat only symptomatic/severe hypocalcaemia)

• 10% Calcium gluconate - 20ml in 100ml NS over 10 min - Followed by infusion - 10% Calcium gluconate - 60ml in 500ml NS over 5 hrs
• Adjust the drip rate to maintain calcium at 8-9 mg/dL
• Taper and stop IV infusions slowly
• Avoid giving IV calcium in tumor lysis syndrome
• Correction of cause
• Long-term management -
  • Oral calcium - 1-2 gm/day
  • Vitamin D (Alfacalcidol) - 0.25-1 microgram/day
• Correct associated hypomagnesemia

Hypercalcemia

(Calcium->11mg/dL)

Causes:

• Hyperparathyroidism
• Drugs-Thiazides, Lithium, VitaminD
• Malignancies-Multiple myeloma, leukemia, lymphoma, metastatic tumor etc
• Immobilization
• Renal failure
• Hyperthyroidism
• Granulomatous diseases

Clinical features (Stones, bones, abdominal groans, psychic moans)

• Polyuria
• Renal colic
• Anorexia
• Vomiting
• Constipation
• Fatigue
• Dehydration
• Stupor
• Seizures
• Coma
• ECG: Short QT interval with widened QRS complex

Treatment:

• Hydration (To enhance urinary calcium excretion): 3-4 liters of fluid given over 24 hrs - NS with initial drip rates of up to 500 ml/hr
• Frusemide: 20-40 mg - IV Stat, after hydration - To promote calcium excretion
• Measure Ca, Na, K, Phosphate, Mg twice a day
• Avoid thiazides
• Bisphosphonates: Zoledronic acid 4 mg - IV - Over 15 min or Palmindronate - 60-90 mg in 500 ml NS IV over 4 hrs
• Steroids: Prednisolone - 1 mg/kg/day - Useful especially in hypercalcemia related to malignancy
• Calcitonin - 4-8 IU/kg - IM/SC - 6-12 hrly - Not useful after 48 hrs due to downregulation of receptors
• Oral phosphate: 0.5-1 gm - TDS - Use only if phosphate levels are low and renal functions are normal
• Propranolol - useful in preventing cardiac adverse effects
• Hemodialysis: If all measures fail
• Treatment of cause

Hypomagnesemia

(Magnesium levels <1.8mg/dL)

Causes:

• Increased loss: Vomiting, diarrhea, ATN, CRF
• Drugs - Alcohol, diuretics, gentamycin, digoxin
• Decreased intake - Starvation, malnutrition, chronic alcoholism
• Malabsorption syndrome
• Metabolic - Hypocalcemia, hypokalemia
• Endocrine - Diabetic ketoacidosis, thyrotoxicosis, hyperparathyroidism

Clinical Features:

• Tremors, paraesthesia
• Tetany
• Altered mental status
• Ataxia
• Nystagmus
• Seizures
• ECG-ProlongedPRandQTinterval,STdepression,widenedQRS,Torsadesdepointes

Note: Prolonged hypomagnesemia produces hypocalcemia and hypokalemia.

Treatment:

• Rehydrate with NS - 250ml/hr
• Treatment of underlying cause
• Mild - Oral magnesium supplementation - 250-500mg - OD/BD
• Severe - MgSO4 - 1-2gm IV - Over 30-50 min - then, 6g in 1 lit NS over 24 hrs

Hypermagnesemia

(Magnesium level- >3mg/dL)

Causes:

• Renal failure
• Iatrogenic
• Rhabdomyolysis
• Tumour lysis syndrome

Clinical features:

• Muscular weakness
• Respiratory depression
• Confusion
• Ataxia
• Hypotension

Treatment: (Treat only if symptomatic/ Magnesium levels >3mg/dl)

• IV Hydration with NS - 500ml/hr
• 10% calcium gluconate - 10ml in 100ml 5% dextrose
• IV Frusemide - 40-80mg - 2-4 hrly - Increases renal excretion
• Hemodialysis: in case of renal failure or if there is severe toxicity

Intravenous Fluid Therapy

• 2-2.5lit of fluid is required per day
• If patient is unable to take orally, this much fluid needs to be given.
• IV fluids have to be given if patient has fluid loss due to vomiting or diarrhea. Other indications include, hyperhydration as part of tumor lysis syndrome prophylaxis and along with administration of high dose chemotherapy (especially methotrexate, cyclophosphamide etc)
• CVP helps to adjust fluid infusion. If it is not available, use BP and urine output as guide. (Systolic BP >90mmHg and Urine output 20-30ml/hr, indicate just adequate hydration)
• In dehydrated patients for immediate volume expansion, NS or RL can be used
• Use IV fluids with caution, in elderly with cardiac ailments
• Increased JVP and basal crackles indicate fluid overload
• In the presence of edema (of any cause) IV fluid must be used with extreme caution. 
• If patient needs nutrition through IV fluids, give IV fluid containing glucose.
• In diabetics/ in those who have hyperglycemia (>300mg/dL)- Use NS with insulin. Once glucose level is <300mg/dL, change to 5% dextrose or DNS.
• When using dextrose containing IV fluids add neutralizing dose of insulin to fluids. (1lit of 5% dextrose/ DNS requires 20 units of plain insulin)
• If patient is on IV fluids for more than couple of days, add multivitamins, minerals and trace elements to the infusion.
• Unnecessary use of IV fluids must be avoided keeping in mind limitations and complications.
• Frequently review all NPO order and consider oral/ RT feeds at the earliest.
• D5 contains 50gm glucose/L = 170 cal/lit
• DNS contains 50g glucose + 154mEq Sodium per Lit
• RL Contains- Potassium 4mEq/L, Calcium- 3mEq/L, Lactate- 24mEq/L
• NS contains 154mEq Sodium per Lit
• Avoid IV fluids in patients with severe anemia, as it can precipitate congestive cardiac failure.