Mannitol (Osmitrol) is contraindicated in severe pulmonary oedema, severe heart failure, active intracranial hemorrhage, disruption of blood brain barrier, severe dehydration and anuria.
A TEST DOSE of Mannitol should first be administered in patients with renal impairment, to ascertain renal function and the ability of the kidneys to eliminate Mannitol and other toxic substances from the body.
A test dose of about 0.2-0.25g/kg body weight is usually administered between 3-5minutes. The nurse monitors patient’s urinary output every hour (urethral catheter must be passed to ensure this) for 3-4hrs. The urinary output must range between 30-50ml/hr. If patient does not make up to that range, the second test dose is given. If patient still does not make up to the set range, discontinue Mannitol, and call the attention of the physician to review the patient.
Mannitol crystalizes at low temperatures. Therefore the nurse must examine the mannitol solution in bright light to ensure it is clear and free of crystals. The infusion giving set to be used in administering Mannitol should have micro-filters to help in filteration of unidentified crystals. Also, the solution should be warmed close to body temperature (37 degrees celcius) if crystals are seen, to dissolve the crystals.
A large peripheral line or central line should be used to administer Mannitol, especially the concentrations of 20% and above, because of its high risk of venous irritation.
The nurse must constantly assess the cardiovascular, respiratory, neurological and renal function of a patient on Mannitol therapy, by monitoring patient’s blood pressure, heart rate and rhythm, respiratory rate and pattern, breath sounds, hourly urinary output, level of consciousness and the intravenous site (check for any sign of inflammation or irritation).
The nurse also monitors the Mannitol flow rate. Mannitol is usually infused over 30-60minutes. Proper documentation of all nursing activities must be done. Regular monitoring of serum electrolytes, blood urea nitrogen and creatinine must be ensured.
Do not administer Mannitol simultaneously with blood and blood products, to prevent hemolysis or pseudoagglutination. If it is very essential to do so, add 20mEq (same as 20mmol) of sodium chloride to one liter of Mannitol.
Other uses of Mannitol include:
1) Bladder irrigation especially in transurethral surgeries, to minimize the risk of intravascular hemolysis during surgery.
2)Inhaled Mannitol is a bronchoconstrictor used to test for bronchial hypersensitivity/hyperreactivity.
3) Mannitol helps in the measurement of glomerular filteration rate (GFR) because of its ability to pass through the glomerulus freely.
A test dose of 0.2g/kg of IV 10% Mannitol was ordered for a patient weighing 60kg.
i) Calculate the dosage of the drug.
ii) How many milliliter of the drug will the nurse administer?
i) Weight= 60kg
Test dose= 0.2g per kilogram
Test dose= 0.2g * 60 = 12g
Test dose = 12g of IV 10% Mannitol.
‘10% Mannitol’ means ‘Each 100ml of solution contains 10g Mannitol’
If ‘Each 100ml of solution contains 10g Mannitol’;
…………ml of solution will contain 12g Mannitol?
(100*12) ÷ 10 = 120ml
The nurse will administer 120ml of IV 10% Mannitol
IV 20% Mannitol 60g stat was ordered for a head injured patient with raised ICP in the emergency unit.
i) How many milliliter of the drug will the nurse administer?
ii) Assuming 20% Mannitol is out of stock, and the available concentration is 25% Mannitol. Calculate the amount of IV 25% Mannitol the nurse will administer, using the original order.
LET’S WORK IT OUT!
i) IV 20% Mannitol 60g stat
Each 100ml of solution contains 20g Mannitol (20% Mannitol);
…………ml of solution will contain 60g of Mannitol
The nurse will administer 300ml of IV 20% Mannitol
ii) Ordered concentration is 20%
Available concentration is 25%
Ordered dose is 60g
New dosage = (ordered concentration ÷ available concentration)*ordered dosage
The new dosage is 48g of IV 25% Mannitol.
Each 100ml of solution contains 25g Mannitol (25% Mannitol);
…………ml of solution will contain 48g Mannitol
The nurse will administer 192ml of 25% Mannitol
Ogunlabi, David (RN).