1 fluid and electrolyte therapy dr ashoka acharya consultant paediatrics warwick hospital
TRANSCRIPT
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Fluid and electrolyte therapy
Dr Ashoka Acharya
Consultant Paediatrics
Warwick hospital
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Dehydration
Abnormal fluid losses overcoming renal compensating mechanisms
Main aim of compensation is maintaining plasma volume and BP at all cost
Loss of homeostasis –hypovolaemic shock
Principal causes: diarrhoea and DKA
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Definition
Parenteral or oral fluid therapy Maintain/restore volume/composition of
body fluids Takes account of corrective
physiological mechanisms
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Fluid therapy: Goal
Achieve normal intracellular and extracellular chemical environment
Thereby optimise cell and organ function
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Factors determining requirements
Maintenance fluid: replaces usual losses of fluid and electrolytes
Deficit replacement fluid: designed to replace abnormal losses due to disease
Supplemental fluid: replaces measured or estimated continuing abnormal losses
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Factors determining requirements
Each component is calculated separately
Fluid therapy often based on gross estimates. Deficit often overestimated.
Repeated clinical reassessment and adjustment needed
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Maintenance fluid
Directly related to metabolic rate endogenous water production urinary solute excretion, heat production- 25% lost through
insensible water loss)
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Maintenance therapy
Generally 100ml per 100 calories used Urine: obligatory loss = 65 ml Insensible water loss = 35 ml Sweating =23 ml pulmonary =12 ml
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Maintenance therapy: increased requirements Increased activity (30%) Fever (1°C increases by 12%) Dry environment Hyperventilation ELBW- transcutaneous losses 100-
200ml/kg/day Overhead heaters, phototherapy units
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Maintenance fluid-decreased requirements Comatose Hypothermia Highly humidified atmospheres Humidified ventilator circuits
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Maintenance fluid: increased renal losses High solute load (DM, Mannitol, high
protein diets) ADH insufficiency Central Nephrogenic Primary Secondary: sickle cell, obstructive uropathy, chronic
PN, reflux nehropathy, hypokalemia, hypercalcemia, drugs, psychogenic polydipsia
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Maintenance fluid: decreased urinary losses SIADH Renal failure
Replace insensible water loss +urine output ml/ml with free water
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Maintenance sodium needs
Increased: CF, salt losing nephropathy, chronic PN, obstructive uropathy, diuretics, fistulas, diversions, NG drainage
Decreased: Hepatic failure, cardiac failure, renal failure, nephrotic syndrome
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Maintenance potassium needs
Increased: Chronic renal disease, gastric and intestinal drainage, chronic diuretics, laxative abuse
Decreased or nil: Acute renal failure, adrenal insufficiency, severe metabolic acidosis
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Normal maintenance requirements (holiday and segarWt (kg) H20(ml/k
g/dy) Na(mmol/kg/dy)
K(mmol/kg/dy)
Energy(kcal/Kg/dy)
First 10 kg
100 2-4 1.5-2.5 100
Second 10 kg
50 1-2 0.5-1.5 75
Subsequent kg
20 0.5-1 0.2-0.7 30
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Maintenance fluids: route
Oral or parenteral Calories: usually as 5% dextrose TPN
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Deficit Therapy: factors affecting
Oral or parenteral intake Pathologic body losses Physiologic body losses compensatory attempts to modify volume
and composition Net effect- Deficits from different causes
often similar in magnitude and composition
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Infant: moderately severe dehydrationCondition H2O
(ml)Na(mmol)
K(mmol)
Cl(mmol)
D and VIsonatremic
100-200 8-10 8-10 8-10Hypernatremic
100-200 2-4 0-4 -2 to –6Hyponatremic
100-200 10-12 8-10 10-12Pyloricstenosis
100-200 8-10 10-12 10-12DKA 100-200 8-10 5-7 6-8Fasting andthirsting
100-200 5-7 1-2 4-6Per kg body weight
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Deficit therapy
Severity: Magnitude and rapidity Estimated from recent weight or clinical
features Type: Relative loss of water and
electrolytes mainly sodium pathophysiology therapy prognosis
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Deficit therapy: Types
Isotonic: sodium 130-150 mmol/l, no fluid shifts, 80% of cases
Hypotonic: sodium <130mmol/l, ECF to ICF, 10% cases
hypertonic:sodium>150 mmol/l, ICF to ECF, 10% cases
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Deficit Therapy:types and history
D and V for days, good intake, low salt Cholera, bacillary dysentery High fever, poor intake Infant with NDI, poor water intake Intake of dilute milk formula Intake of boiled semiskimmed milk wrongly prepared ORS
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Assessment of deficit severity
Signs &symptoms
Mild dehydration Moderatedehydration
Severedehydration
Body weightloss(%)
3-5% 6-9% 10%or more
General app,infant
Alert, restless Thirsty, restless/lethargic/irritable
Lethargic/comatoseFloppy,cold,sweaty
Older child- Thirsty, alert,restless
Thirsty, alert,posturalhypotension
Lethargic,cold,sweaty,cyanosed,wrinkled skin, musclecramps
Radial pulse Normal Rapid and weak Rapid,thready/impalpable
Respiration Normal Deep Deep and rapid
Anterior fontanel Normal Sunken Very sunken
contd
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Assessment of severity: contd
Systolic BP Normal Normal/orthstatichypotension
Low/unrecordable
Skin elasticity Retractsimmediately
Retracts slowly Retracts veryslowly
Eyes Normal Sunken Grossly sunken
Tears Present Absent/reduced absent
Mucosa Moist Dry Very dry
Urine Normal Reduced and dark Anuria/severeoliguria
CRT Normal +/- 2 sec >3 sec
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Calculation of deficit fluid
Percentage dehydration x wt in kg x 10= ml of fluid
eg: 7% dehydration of infant weighing 10 kgs = 7x10x10=700 ml
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Clinical features
Signs represent depletion of ECF Plasma: tachycardia, fall of BP, postural
hypotension, cool extremities, increased CRT, decreased urine
Interstitial fluid: Tenting of skin Transcellular fluid: dry mouth, sunken eyes,
decreased tears, sunken fontanel
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Signs of dehydration
Mild dehydration: no signs Severe dehydration: Prolonged capillary refill
time,dry mucosa, decreased skin turgor, general appearance are the most sensitive and specific
Acidosis: Kussmaul’s breathing Hypokalemia: weakness, abd dist, ileus,cardiac
arrhythmias hypocalcemia and magnesemia: tetany, muscle
twitching
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Signs V's type of deficit
Hyponatremic: increased severity of signs for amount of fluid loss
Hypernatremic: Less signs, irritable, hypertonic, hyperreflexic, warm extremities, doughy skin
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Lab tests
FBC: Increased Hb, PCV Serum Na: type of dehydration serum K: gut loss, acidosis; needs ECG monitoring Serum HCO3: acidosis- D&V, DKA: alkalosis-Pyloric
stenosis, NG drainage Serum chloride: changes with Na, chloride diarrhea Urea/creatinine: elevated with decrease in GFR, may
be normal! Urine: infection screen, specific gravity, electrolytes stool: culture, electrolytes
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Treatment
Oral therapy: mild to moderate dehydration
Parenteral therapy: severe dehydration Persistent vomiting Refusal of oral intake Abdominal distension No caregiver to give close attention
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Stages of treatment
Initial therapy: expand ECF volume Subsequent therapy: replace
deficit/maintenance/ongoing losses Final therapy: Return to normal
composition/establish oral feeds/correct potassium deficit
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Commonly available crystalloids: isotonicFluids Na (mmol/l) K (mmol/l) Cl (mmol/l) Energy(kcal
/l)other
saline0.9% 150 0 150 0 0
saline0.45%dextrose 2.5%
75 0 75 100 0
Saline 0.18% dextrose 4%,KCl 20mmol/lit
30 20 30 160 0
Dextrose 5%
0 0 0 200 0
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Isotonic crystalloid fluids
Fluid Na K Cl Energy Other
Saline 0.18% dextrose 4%
30 0 30 160 0
Hartmann’s solution
131 5 111 0 lactate
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Hypertonic crystalloids
Fluid Na K Cl Energy Other
Saline 0.45% dextrose 5%
75 0 75 200 0
Dextrose 10%
0 0 0 400 0
Saline 0.18% dextrose 10%
30 0 30 400 0
Dextrose 20%
0 0 0 800 0
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Colloid fluids
Fluids Na K Ca Duration of action
comments
Albumin 4.5%
150 1 0 6 Protein buffers
Gelofusine 154 <1 <1 3 Gelatine
Haemaccel 145 5 12.5 3 Gelatine
Pentastarch 154 0 0 7 Hydroxyethyl starch
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Initial therapy
Normal saline or Hartmans solution regardless of type of deficit
20 ml/kg rapid bolus, repeat if needed IV, intraosseous line Never use hyponatremic fluids Adequate crystalloid dose better than colloid No potassium till urine output established
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Subsequent therapy
Calculate over 8 hour intervals Deficit replaced over 24 hours but can
be done over 8 to 12 hours except HYPERNATREMIA
Early K+ replacement after urine output Maximum K+, 40 mmol/l (ITU 80
mmol/l)
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Isonatremic dehydration
Deficit plus maintenance plus ongoing losses calculated
Use 0.45%saline with 2.5% or 5% dextrose for subsequent therapy
Give 50% in first 8 hours and remaining over 16 hours
Subtract boluses from total fluid Assess clinical state regularly and modify if
needed
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Hyponatremic dehydration
Extra Na deficit (mmol/l)=desired Na-actual Na x 0.6 x Wt kgs
Manage as for isonatremic dehydration but replace deficit Na over 12-24 hours
Raise serum Na by 10 mmol/l/day If Na <120mmol/l and seizures give 3%
Nacl 1ml/min max 12ml/Kg
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Hypernatremic dehydration: complications Cerebral haemorrhage, thrombosis,
subdural effusion- permanent handicap, renal vein thrombosis
During treatment- cerebral oedema, seizures, hypocalcemia
High mortality if Serum Na >160mmol/l
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Hypernatremic dehydration
Always use isonatremic boluses Slow correction of deficit over 48 to 72 hours Aim to decrease serum Na by 10 mmol/l/day Use 0.18saline or 0.45% saline with dextrose
for subsequent therapy Seizures: 3% saline, mannitol,
hyperventilation, calcium gluconate
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Supplemental fluids
Consider composition of fluid lost D&V: 0.45% saline Cholera:0.9% saline NG tube aspiration: 0.45 to 0.9% saline
plus potassium Gut losses: same
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Composition of external losses
Fluid Na (mmol/l) K (mmol/l) Cl (mmol/l) Protein (g/dl)
Gastric 20-80 5-20 100-150
Small bowel 100-140 5-15 90-130
Ileostomy 45-135 3-15 20-115
Diarrhoea 10-90 10-80 10-110
Burns 140 5 110 3-5
Sweat 10-30 3-10 10-35
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Assessment of response
Appearance, activity Skin turgor BP Intake/output chart U&E, glucose blood gas CVP monitoring
Eyeballs, tears CRT Weight Urine Specific
gravity Urine output ECG monitoring
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Oral rehydration therapy
Mild to moderate dehydration Types of ORS: high sodium- 90mmol/l,
low Na- 50 mmol/l Glucose facilitated sodium absorption,
sucrose less effective, rice based effective
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ORS
Use 50ml/kg in mild and 100ml/kg in moderate dehydration.
Give over 4 hours. Allow breast feeds and formula after rehydration. Reassess regularly. Small frequent feeds decrease vomiting. Consider NG tube.
Maintenance with 100ml/kg/day till diarrhoea stops
For on going losses add 10-15ml/kg/hr
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Hyponatremia: sodium depletion
Renal losses: Preterm, ATN, Diuretics, mineralocorticoid deficiency, RTA
Extra renal loss: D&V, Burns, ascites, pleural effusion,csf drainage, NG drainage, CF
Nutritional deficits: Inadequate Na in TPN, oral intake
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Hyponatremia: water excess
SIADH Glucocotricoid deficiency Hypothyroidism Excess parenteral fluid Psychogenic polydipsia Tap water enema
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Hyponatremia: excess Na and water Nephrotic syndrome Cirrhosis Cardiac failure Acute and chronic renal failure
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Hyponatremia: asymptomatic
Water Excess: (urinary Na usually >20 mmol/l) fluid restriction, may be needed for days
Salt deficiency: (urinary Na <10 mmol/l, except in renal salt loss) Add salt to diet
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Hypernatremia: sodium excess
Improperly mixed ORS or formula Accidental or deliberate swap of salt for
sugar in feeds Excess Bicarb during resus Hypernatremic enemas Drugs: penicillin, gaviscon
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Hypernatremia: water deficit
Diabetes insipidus Solute diuresis D&V Inadequate breast feeds Intentional water with holding Insensible loss in prematures
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Hypernatremia: treatment
Salt poisoning: peritoneal dialysis Phenobarbitone for seizures Inotropes for heart failure
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Hypokalemia: causes
Diarrhoea Alkalosis Volume depletion Primary hyperaldosteronism,cushing syn,
thyrotoxicosis Diuretic abuse DKA Bartters syndrome
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Hypokalemia: consequences
Cardiac: flat T wave and prolonged QT interval Orthostatic hypotension, tetany, hypotonia,
muscle weakness, death from resp failure Paralytic ileus, gastric distension Failure to thrive Rhabdomyolysis Nephrosclerosis and interstitial fibrosis: polyuria alkalosis
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Hypokalemia: treatment
Replacement potassium orally or parenterally
3 mmol/kg/day in Bartter syn/indomethacin
Up to 10 mmol/kg/day in RTA/hyperaldosteronism
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Hyperkalemia: causes
Renal failure Acidosis Adrenal insufficiency Cell lysis (trauma, surgery, tumour lysis) Excessive intake Sampling error!
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Hyperkalemia: consequences
Paresthesias, flaccid paralysis Tall T waves, increased P-R interval,
wide QRS complex, VF
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Hyperkalemia:management
If cardiac rhythm affected give calcium 1 mmol/kg iv/specific anti arrhythmic drug
If normal rhythm, give nebulised salbutamol 2.5 to 5 mg. Check K and pH.
If falling K- give calcium resonium 1g/kg po or pr- plan dialysis if needed
If still high (6.5 or more) give dextrose infusion 0.5g/kg/hr and iv insulin infusion, 0.05units/kg/hr if pH <7.34
If pH >7.35 give sodium bicarbonate 2.5 mmol/kg iv
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Hypocalcemia
Septicemia, rickets,hypoparathyroidsm, pancreatitis, massive blood transfusion, renal failure
Weakness, tetany, convulsions, hypotension and arrhythmias
Calcium infusion, phosphate binders/dialysis, treatment of cause
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Hypercalcemia
Hyperparathyroidism, Hypervitaminosis D&A, Idiopathic hypercalcemia, malignancy thiazide diuretic abuse,skeletal disorders,immobilisation
Polyuria, polydypsia Volume expansion with saline,
treatment of cause
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Hypomagnesemia
Chronic diarrhoea, sprue, celiac d, prolonged TPN low in Mg, hyperaldosteronism, Gitelman’s syndrome, cisplatin and aminoglycosides
Convulsions, tetany athetoid movements, hyperaccusis
Im or iv magnesium replacement as magnesium sulphate
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Hypermagnesemia
Usually in renal failure, Addison disease, toxemia of pregnancy, enemas in megacolon
Drowsiness, coma if levels exceed 10 meq/l. Intra ventricular and atrioventricular conduction defects at 5 meq/l
IV calcium gluconate rapidly reverses effects on heart and CNS
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Case 1
8 week old infant Weight 4 kgs, poor wt gain in last 4
weeks, Vomiting from 3 weeks of age, now after
most feeds, forceful, not passing urine well last 24 hours
Moderate dehydration on examination Na 130, Cl 94, K 2.6, HCo3 29.8
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Case 1
Maintenance: 100 x 4= 400 ml On going losses: Ng aspirate volume for volume with normal
saline Start 0.45% saline dextrose 5% to give 400 ml over 8 hours and
remaining 400 ml over 16 hours Add Kcl 4 mmol/100ml once urine output noted Monitor weight, urine output, Nasogastric aspirate, blood gas
and electrolytes,ECG. Once serum K rises to 3.5 decrease Kcl to 2 mmol/100ml Deficit fluid: 10 x10 x4= 400 ml Once stable, send for surgery
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Case 2
One year old, 10 Kgs with 2 days of D&V. Given clear fluids at home. No urine in last 6 hours. Some fever. Not drinking ,lethargic last 2 hours.
Severe dehydration on examination Blood: Na 136, K 2.2, Hco3 8, pH7.35
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Case 2
Bolus 20 ml/kg- 0.9%saline, repeat if still shocked Deficit fluid: 15 x10 x10=1500 ml – 400ml bolus = 1100ml Maintenance fluid: 100 x10= 1000 ml Give 1050ml in 8 hours and 1050 remaining in 16 hours as
0.45% saline 5% dextrose Add Kcl 40 mmol/l after urine output Monitor ECG, weight, urine output, electrolytes, continuing
losses for replacement Once rehydrated offer ORS, milk and review fluids
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Case 3
Four year old weighing 14 Kgs, lethargic, vomiting, rapid breathing since 12 hours. Producing urine. Normal stools. Over 2 weeks, since a cold has been drinking a lot, eating a lot and bed wetting again.
Moderate dehydration Glucose 30 mmol/l, Na 128 mmol/l, K 4.8
mmol/l, HCO3 8 mmol/l, pH 7.28
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Case 3
Start normal saline infusion, 20 ml/kg over 1 hour Start insulin infusion 0.05u/kg/hr 0.45 saline+Kcl 20mmol/500 ml, 20 ml/kg over 2nd hour 0.45 saline+KCL or Pot phos 30mmol/l over 10 hours Maintenance fluid for 36 hours:1000+50x4=1200+600=1800ml Deficit fluid: 10x10x14= 1400 ml Correct 50% deficit in first 12 hours Monitor ECG, glucose, U&E, blood gas, weight, urine output, GCS hourly
to 2 hourly Change fluid to 0.18 saline 5% dextrose when blood glucose reaches 16 to
17 mmol/l. Adjust K and insulin infusion rates as needed. Consider an Antibiotic.
When blood gas normal, blood glucose stable, patient drinking, give subcutaneous insulin 0.2 to 0.4 units/kg qds and stop iv infusions.
Start regular insulin dose after another 24 hours
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DKA: complication
Cerebral edema: headache, change in consciousness,unequal dilated pupil, vomiting,incontinence,delirium,bradycardia
Reduce iv rate, mannitol 1gm/kg iv, repeat in 2-4 hours