Freely filtered at the glomerulus and not reabsorbed. It increases tubular-fluid osmolality and urine volume. Because it does not cross an intact blood-brain barrier, it also draws extracellular water from brain into plasma and reduces CSF volume and pressure.

osmotic agent. inc plasma osmolality and draws water out of the CSF and vitreous body. Freely fi¬ltered at the glomerulus but poorly reabsorbed. Because
the PCT is involved in the reabsorption of 60-70% of the -filtered load
this is the most important site of action

• increases the osmolarity of the glomerular
filtrate -> increasing urinary volume
• decreases CSF volume & pressure by
(1) decreasing rate of CSF production
(2) withdrawing brain extracellular water across
the BBB into plasma

Increased serum sodium concentration. Leads to increase in serum tonicity, leading to diffusion of intracellular fluid into the intravascular space, decreasing cerebral oedema.

↓ICP/IOP

CNS: Decreased cerebral oedema, decreased ICP, may cause central pontine myelinolysis

CVS: Fluid shift into intravascular compartment increases plasma volume and may improve preload
? increase cardiac output
? increase BP

IV only.

IV.

Biphasic – plasma and ECF.
Does not cross BBB

0.47 L/kg

Not metabolised to a clinically significant extent. Excreted unchanged in urine.

Minimally hepatic to glycogen

Unmetabolized

Unmetabolized

Urine (~55% to 87% as unchanged drug)

renally excreted

Term half life: 4.7 hrs

Usually rare and idosyncratic. It may cause symptoms of pulmonary hypertension.

1. Central pontine myelinolysis
2. Hypernatraemia and hyperosmolarity
3. NAGMA
4. Thrombophlebitis
5. Seizures

Osmotic Diuretic

Diuretic - Osmotic

Crystalloid

Used to reduce CSF pressure and volume, for short-term management of acute glaucoma, as an osmotic diuretic in selected renal indications, for bowel preparation and in rhabdomyolysis.

osmotic diuretic
(to ↓intracranial pressure or introccular pressure).
Used to test for airway hyperresponsiveness

1. reduce CSF volume -> reduce ICP
2. preserve renal function during perioperative
period in jaundice patients under going major
vascular surgery.
3. acute management of glaucoma
4. bowel prep
5. initiate diuresis in transplanted kidney
6. treatment for rhabdomyolysis

1. Treatment of severe, symptomatic hyponatraemia
2. Management of raised ICP
3. In nebulized form as an expectorant

Mannitol is a low-molecular-weight polyol (molecular weight 182) used as an osmotic agent.

polyhydric alcohol MW 200, synthesized by redn of mannose

an alcohol derived from Dahila tubers (6 carbon
sugar)

decrease ICP: 0.25g/kg over 15min to 1g/kg

PROS & CONS – See BELOW

Hypertonic Crystalloid

PROS & CONS – See BELOW

Level 3

Level 1

Sterile 10% and 20% aqueous solutions. Crystallisation may occur at low temperatures.

1-% or 20% (100gm in 1000ml or 500ml)
Crystallizes at ↓temp

sterile solution
10-20% in water

3%, 5% and 23.4%
Should be administered through CVC due to thrombophlebitis

1-2gm/kg IV

Osm (20%) 1100

ADVANTAGES:
Still fairly cheap
• Rapid effect (onset – minutes, duration – 3
hrs)
• Seems to have some sort of rheological
benefit (increases red cell deformability)
• Acts as a transient volume expander
• May have a better effect on cerebral blood
flow for a given reduction in ICP.

DISADVANTAGES:
Unstable in storage: at low temperatures
and at altitude, it precipitates.
• Medium for bacteria and fungus.
• Causes a brief state of volume overload
• Causes torrential diuresis and hypovolemia
• Causes hyponatremia while in the serum,
and hypernatremia after the inevitable
diuresis
• washes out medullary interstitial gradient -
> decreased ability to concentrate urine
• Endpoint is serum osmolality(320), which is
cumbersome to measure
• May cause ICP to "rebound" after
prolonged use
• should be discontinued if Na+ > 160 or
osmolarity > 320mosmol/kg

Osm 900

Na 450
Cl 450

ADVANTAGES:
Cheap
• Stable in storage
• Easy to transport (small volume)
• Very rapid effect (peak @ 10 min, lasts 1
hour)
• Seems to have some sort of intrinsic antiinflammatory effect (may decrease MODS)
• May also have some rheological benefits
At least as potent as mannitol when it
comes to reducing intracranial pressure
• Less potential for hypovolemia than with
mannitol- the diuretic effect is less potent
• rapid restoration of intravascular volume,
BP and decreases ICP
• May have a better effect on cerebral blood
flow for a given reduction in ICP.
• Safe endpoint (serum sodium around 145-
155) is easily monitored with serial ABGs.
• doesn’t need osmolality testing
• higher reflection coefficient at the blood
brain barrier than mannitol
• can be used as a continuous infusion

DISADVANTAGES:
Need for central venous access
• No standards for which concentration to
use, or how to give it
• Hypokalaemia
• Hyperchloraemic acidosis
• Hypernatremia
• Should not be used if the patient is
chronically hyponatremic
• Phlebitis
• Tissue necrosis if extravasates
• central pontine myelinosis if Na+ corrected
too quickly in hyponatraemia
• Increase in circulating volume with risk of
fluid overload.
• Coagulopathy (APTT and INR)
• Altered platelet aggregation.
• May affect normal brain more that injured
brain which theoretically may worsen
herniation
• Rebound intracranial hypertension