Guidance for medical examiners when assessing a patient for either a general topic or condition – Anticoagulation, Warfarin.
Aeromedical Implications
Effect of aviation on treatment
- Variable INR control due to potential impacts from occupational demands of shift work / long haul flying / irregular food intake / medication timing and/or or changes in diet that can affect the INR due to varying vitamin K levels within different foods (e.g., green leafy vegetables are high in vitamin K).
Effect of treatment on aviation
- Overt incapacitation
- Distracting pain from gastrointestinal haemorrhage or cerebrovascular bleed
- Loss of consciousness from cerebrovascular bleed
- Sudden death
Approach to medical certification
Based on the condition
- Based on the underlying condition necessitating anticoagulation
Based on treatment
- Acceptable, stable treatment without significant side effects
Demonstrated stability
- When commencing warfarin, a minimum of six weeks of observation on ground is required, and last four INRs at least one week apart must be within the therapeutic target range
Risk assessment protocol - Information required
A report from the treating doctor will be required.
- When commencing warfarin, a minimum of six weeks of observation on ground is required, and last four INRs at least one week apart must be within the therapeutic target range. Subsequent serial INR results performed at least monthly or more frequently if operationally appropriate
- INR therapeutic target range recommendation from the treating doctor based on the underlying condition
- For recertification –Serial INR levels and the percentage of time in the therapeutic range (TTR)
- Bleeding prediction scores, such as HAS-BLED with comment from the treating doctor on whether modifiable risk factors are adequately managed
- Monitoring regime including compliance with and stability of anticoagulant medication
- Any side-effects
- Estimate of annualised percentage risk of incapacitation taking into consideration the underlying medical condition, co-morbidities and Warfarin anticoagulation
- Follow-up plan
Indicative outcomes
- Warfarin and Novel Oral Anticoagulants (NOACs) are approved by CASA AVMED for use by pilots and controllers whilst exercising the privileges of their medical certificate. However, Class 1 and Class 3 medical certificate holders using anticoagulation medication will be subject to multi-crew/proximity restrictions (see separate guideline on NOACs)
- Pilots and controllers on Warfarin are to be grounded if their INR is outside the certifiable range of 1.8 to 4.0 or if persistently outside designated therapeutic target range for anticoagulant treatment
- Pilots and Controllers prescribed Enoxaparin or other low molecular weight heparin will not be cleared to exercise the privileges of their certificate. (Enoxaparin may be used in combination with Warfarin during the initial treatment while grounded)
- Initial notification to CASA and grounding is required on diagnosis of the underlying condition and commencement of Warfarin anticoagulation
- Clearance by CASA is required before exercising privileges
- Permanent multi-crew restriction will be likely if anticoagulation is required long term
- Cumulative risk assessment performed by CASA includes:
- risks associated with the medication
- risks due to the condition for which anticoagulation is indicated
- additive risks due to other co-morbid conditions.
Favourable
- Stabilised therapeutic warfarin treatment (within target INR range)
- Modifiable risk factors for bleeding are well controlled
- INR levels- percentage of time in the therapeutic range (TTR) > 65% [therapeutic target range as recommended by the treating physician based on the underlying condition]
- Class 1 - multi-crew operations only
- Class 3 - proximity restriction required
- Class 2 - unrestricted
Unfavourable
- Enoxaparin or other low molecular weight heparin
- Significant side-effects
- INRs percentage of time in the therapeutic range (TTR) < 65% [therapeutic target range as recommended by the treating physician based on the underlying condition; typical INR goals are in the range of 2 to 3 and could be higher in some cases]. INR level outside the certifiable range of 1.8 to 4.0 requires grounding and must be reported to the DAME or CASA
- Non-compliance
Pilot and Controller Information
- Any change in condition must be reported to the DAME
- Anticoagulation is an aero-medically significant treatment
- The conditions which require warfarin treatment are aero-medically significant. Poor control of warfarin can cause a large increase in health risks. There is an increased risk of bleeding when INRs are above the therapeutic target range and increased risk of thromboembolic events when INRs are below the target range. Therefore, it matters that it is very carefully managed.
- Pilots and controllers who are commenced on anticoagulation are required to ground themselves and notify this treatment to their DAME and CASA
- Permanent multi-crew restriction will be likely if anticoagulation is required long term
- Pilots or controllers considering point of care INR testing should receive training and education in operating the monitor and managing warfarin dosing. Point of care testing device should be approved by the Therapeutic Goods Administration (TGA) or the treating doctor and the accuracy of readings should be verified with the standard laboratory testing every 3 months