I.V. Heparin When to Use it, and How
Situations where IV Standard Heparin is the Preferred
Treatment Include :
1.
When the rapid
offset of action associated with the shorter half life is an advantage, eg
presurgery, peripartum
2.
Post
thrombolysis
3.
Severe renal
failure (creatinine clearance < 0.5 mL/sec).
Enoxaparin can be used, but requires dose adjustment to 1 mg / kg sc
daily for treatment or 20mg sc daily for prophylaxis.
If the 24 hr dosage of Heparin in the first 24 hrs is 30 – 35,000 iu, the rate of recurrence/extension of thrombosis is 5-6% and the bleeding rate 0 - 2%, independent of the APTT achieved.
Commencing
I.V. Heparin
1. All patients
should commence therapy with a bolus dose of 5,000 iu IV or the appropriate weight based dose, if they are
very small (< 50 kg), or very large (> 80 kg).
|
|
Standard Protocol |
Weight Based Protocol |
|
BOLUS |
5,000 iu |
80 iu/kg |
2. Following a
bolus dose immediately commence the heparin infusion.
Standard Protocol
|
Weight Based Protocol |
|
1200 iu/hour |
18 iu/kg/hr |
|
|
Important The target APTT is generally 60 – 85
seconds, or twice the baseline APTT. |
3. Check the
APTT 6 hours after commencing the
heparin infusion. Adjust the infusion rate
according to the following guide.
Standard Heparin Dosage Guidelines Rate Change
Standard Heparin Dosage Guidelines: Based on Heparin Concentration of
100 iu / mL
|
APTT |
Instruction |
Standard Protocol |
Weight Based Protocol |
Recheck APTT |
|
|
Rate Change (mL / hr) |
Rate Change (iu / hr) |
Rate Change (iu / kg / hr) |
|||
|
< 50 |
Repeat 5000 iu bolus |
+2 |
+200 |
+4 |
6 hours |
|
50 – 59 |
|
+1 |
+100 |
+2 |
6 hours |
|
60 – 85 |
|
0 |
0 |
0 |
next a.m. |
|
86 – 95 |
|
-1 |
-100 |
-1 |
next a.m. |
|
96 – 120 |
stop infusion for 30 minutes |
-1 |
-100 |
-2 |
6 hours |
|
> 120 |
stop infusion for 60 minutes |
-2 |
-200 |
-4 |
6 hours |
4. When 2
consecutive APTT have been within the therapeutic range, decrease monitoring of
APTT to early am on phlebotomy round.
5. Full blood counts should be checked on alternate days in
patients on heparin to monitor for heparin-induced thrombocytopenia, a
potentially serious complication of heparin therapy. If the platelet count falls to less than 50% of
baseline, discuss testing for heparin-induced antibodies, and further
management with a Haematologist.
6.
For very large
or very small patients (< 50 kg or > 80 kg) consider using a weight-based
protocol. Weight based dosages can be
calculated using the above guidelines.
7.
Those patients
requiring > 35,000 iu of UFH per 24 hrs are heparin resistant. They should have an anti-Xa level performed
and the heparin dose adjusted to maintain anti-Xa levels of 0.35 – 0.7 iu / mL.
Nursing Instructions For Setting Up A Heparin Infusion :
1.
Set up an
infusion pump with a burette and use a 1000 mL bag of
2.
Fill the
burette with 147 mL normal saline and add 15,000 units of heparin (3 mL of
5,000 unit / mL) to the fluid in the
burette. The heparin concentration is now 1 mL = 100 u heparin.
3.
Prime tubing.
4.
Check the
burette level at least hourly to assess whether desired amount is being
delivered.
5.
The rate of
infusion is prescribed by the doctor.
Any alterations in dose rate must be noted on the anticoagulant chart.
6.
IV site to be
left exposed and observed for extravasation.
7.
Monitor BP,
pulse, temperature and respiratory rate at least 4 hourly whilst the patient is
on heparin therapy.
Unfractionated Heparin Infusion Rate |
|
|
RATE (mL/hr) |
iu /hr |
|
1 |
100 |
|
2 |
200 |
|
3 |
300 |
|
4 |
400 |
|
10 |
1000 |
|
15 |
1500 |
