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Guidelines for Heparin Dosage for Heparinisation for Thrombotic Conditions
Take baseline PT APTT. Give 5,000 iv bolus then start pump at 30,000 units over 24 hours (eg. 30,000 units in 24mls of N saline and set pump at 1ml per hour). Repeat APTT after six hours.
| APTT ratio | Bolus | Rate | Repeat APTT |
| APTT Ratio <1.5 | 5,000 | +2,500 units over 24 hrs | 6hr-12hr |
| APTT Ratio 1.5-2.0 | Nil | +2,500 units over 24 hrs | 6hr-12hr |
| APTT ratio 2.0-3.0 | Nil | Same dose | Next Morning |
| APTT Ratio 3.0-3.5 | Nil | -2,500 units over 24 hrs | Next Morning |
| APTT Ratio 3.5-4.0 | Nil | Stop for 1hr then -2,500 units over 24 hrs | 6hr-12hr |
| APTT Ratio >4.0 | Nil | Stop for 2hr then -5,000 units over 24 hrs | 6hr-12hr |
For S C Heparin 250 iu/kg b.d. [200 for females > 60yrs]. Take specimen four to six hours post injection.
| APTT ratio | Dose adjustment | Repeat APTT |
| <1.5 | +2,500 units b.d. | Next Morning |
| 1.5-2.0 | +1.250 units b.d. | Next Morning |
| 2.0-3.0 | No change | Next Morning |
| 3.0-3.5 | -1,250 units b.d. | Next Morning |
| 3.0-4.0 | -2,500 units b.d. | Next Morning |
| >4.0 | -5,000 units b.d. | Next Morning |
(Last reviewed January 2023)