Swansea Out Of Hours Service (SOS)
Patient Pathway for the Diagnosis and Management of Suspected Deep Vein Thrombosis in GP led Minor Injury Unit
Dr Chris Johns- General Practitioner-
Overview
Since January 2009 Swansea Out of Hours Service (SOS) has taken over the running of Singleton Hospital Minor Injury Unit (MIU). This has led to changes in the delivery of Emergency Care across Swansea. There is now direct admission of ambulance cases to the Singleton Assessment Unit (SAU) which is often extremely busy and overstretched. The current workload of the SAU includes approximately 3 patients a day with suspected deep vein thrombosis (DVT).
SOS believes that it can provide a quality service for the initial diagnosis and management of DVT in the environment of the MIU that would provide benefit for patients. Joint working between Primary and secondary care on this clinical problem will enhance relationships as Singleton goes forward with plans for an Ambulatory Care Centre.
Background
DVT is the 3rd most common cardiovascular event after acute coronary syndrome and stroke. The incidence ranges between 1:3000 under the age of 40 up to 1:500 in those over 80 years. DVT is a potentially serious condition, but not a medical emergency.
Suspected DVT is currently assessed and managed in secondary care in Swansea. There are many pathway models where DVT is delivered on an outpatient basis by suitably trained nurses by Primary Care led service.
For full background on management of DVT please refer-
http://cks.library.nhs.uk/deep_vein_thrombosis
Patient numbers
On a review of data kept at MAU in Singleton over the past 6 months, activity generated through GP referral/MIU walk-in/exclusions would be 3 new patients per day and 6 reviews. This would lead to generation of approximately 2 ultrasound requests a day and a similar number of
D-dimer assays.
Timescales
It is planned to start on 1st February 2010.
Process
Patients will be referred into the MIU DVT pathway through GP referral. GPs can ring directly to speak to the MIU doctor or nurse on 01792 281582. Occasionally patients may present directly to MIU and these will also be accepted. The MIU Doctor or Nurse can review the exclusion criteria and accept or decline the case. Any cases not fitting the criteria will be referred to the admitting Medical Registrar on call. The management of inpatients with suspected DVT will remain unchanged.
The service will run initially in Office hours 8.30-6.00pm Monday to Friday (75% of DVT present in this period). Outside these hours GP will refer patients to the Medical Registrar on call as previously.
Patients will be assessed using a combination of Wells scoring and serum D-Dimer where required. See flow chart and clinical pathway below.
Patients who are negative are referred back to their General Practitioner for further assessment and advice. Where possible an alternative diagnosis will be offered. Patients with a high probability and a negative scan will be offered follow up in 1 week in MIU to assess the need for a second scan.
Positive patients will be started on anticoagulation treatment and referred to Anticoagulant Clinic as early as an appointment is available. The anticoagulation therapy will be managed according to existing ABMU LHB protocols.
Clinical Leads
Medical-Dr Chris Johns Singleton MIU.
Nursing-Ms. Janice Jones Singleton MIU.
Radiology-Ms. Delyth Pirotte Singleton Radiology.
Anticoagulation-Ms Collette Hill Singleton Haematology.
Clinical Issues
1) Patient Presentation and Assessment
Patients with DVT present to both their GP and to Accident and Emergency. Across the UK DVT assessment is generally using the Wells criteria plus D-Dimer blood testing if low probability.
This is a structured scoring system which allows relatively simple assessment and clinical pathways for referral for Doppler ultrasound scanning for definitive diagnosis.
Wells Criteria
Assessing Clinical Probability of DVT- Wells CriteriaAdd Total and Confirm Probability
Assess Clinical Probability / Score / Tick
Active cancer (ongoing treatment or within last 6 months of palliative) / 1
Paralysis, paresis or recent plaster immobilisation of leg / 1
Bed ridden >3 days or major surgery within 4 weeks / 1
Local tenderness / 1
Thigh and calf swollen / 1
Calf swelling 3cm > asymptomatic side (measured 10cm below tibial tuberosity / 1
Pitting oedma in symptomatic leg only / 1
Dilated veins (non-varicose) in symptomatic leg only / 1
Alternative diagnosis, as or more, likely than DVT / -2
TOTAL
Clinical Probability: LOW ≤ 0,1 or 2 HIGH ≥ 3
High = Direct for Scan; Low = DD and Scan if +ve
Probability of DVT / % DVT confirmed / Score
High / 75% Probability of DVT confirmed by Doppler / Score of >3
Moderate / 17% Probability of DVT confirmed by Doppler / Score 1 to 2
Low / 3% Probability of DVT confirmed by Doppler / Score 0 or less
2) High Risk Exclusions to MIU Assessment for DVT Diagnosis and Management
· Suspected PE
· Significant co-morbidity requiring admission
· Pregnancy
· Known bleeding disorder
· Severe uncontrolled hypertension
· Alcohol dependency
· Under 18
· Recent neurological/neurosurgical complications
· Patients already on Warfarin
· Oncology Outpatient referrals
Investigations
D-Dimer
D-Dimers are a specific breakdown product of cross-linked fibrin, released during clot dissolution or fibrinolysis. The main object of the D-Dimer test is to detect situations of thrombin activation and in vivo fibrin formation. Venous thrombotic embolism (VTE) results in raised levels of D-Dimers. The D-Dimer test is available at Singleton Hospital and requires the collection of venous blood to be sent to the pathology laboratory.
D-Dimer is performed on a standard citrated blood sample (prothrombin tube – pale blue top).
A positive D-Dimer score is considered to indicate a possible diagnosis of DVT. However, a positive D-Dimer does NOT confirm the diagnosis of DVT. Fibrin is produced by a wide variety of conditions such as cancer, inflammation, infection and necrosis and the D-Dimer test is therefore
not very specific for VTE. It is however, used as an aid to diagnosis.
Points to note:
• D-Dimers are of less value in very elderly patients
• D-Dimers are of no value in the immediate post-operative period (within 2 weeks of any significant surgery)
• Patients with a high clinical probability score should be referred for
ultrasound scan without D-Dimer testing
• Patients with a low clinical probability score if they are elderly, or have an obvious alternative diagnosis should be observed if appropriate or have further investigation if their risk status changes. These patients will only require Doppler scanning if their clinical probability score changes.
The D-Dimer test for this pathway will be the D-dimer ELISA lab based test.
Pre-Test Probability of DVT (PTP-DVT) & D-Dimer Assay
PTP-DVT / D-Dimer Assay / Expected Doppler Scan result :Low / Negative / 99.5 % of Doppler scans negative
Moderate / Negative / 96.6 % of Doppler scans negative
High / Negative / 85.7 % of Doppler scans negative
On all requests for D-dimer assay a Wells score will be given as clinical information to the Haematology Dept
Imaging for DVT
Doppler ultrasound scan has become the investigation of choice in diagnosis of DVT.
It will detect more than 90% of proximal DVT’s (i.e. popliteal vein and above).
It is less sensitive for calf vein thrombosis (about only 50% are detected) but pulmonary embolism from this site is rare and unlikely to cause significant haemodynamic disturbance even if it occurs. Venography is considered the reference standard investigation for DVT and is considered when ultrasound studies are equivocal for proximal vein thrombosis.
Doppler ultrasound can be arranged by telephoning Singleton Radiology or using the direct booking slots that are available in Singleton SAU. The Ultrasound booking slots will be kept in MIU during pathway hours. It may be easier for some patients to have Doppler ultrasounds performed at Morriston Hospital for geographical reasons or if there are open slots at Morriston if Singleton lists are full. This can be arranged through consultation with Radiology
3) Interim Treatment – pending Definitive Diagnosis:
Commencing Low molecular weight heparin (LMWH). 1.5mg/kg sc
The preferred LMWH locally for this is currently Clexane and will be commenced by the MIU doctor.
It is recommended that Clexane is given once daily until the DVT is excluded or the patient has commenced Warfarin; then it is administered for at least 5days, and until Warfarin has brought the INR into the therapeutic range for 2successive days. Target INR 2.5 (range 2-3)
DOSE RANGE
The dose is 1.5mg / Kg sc (as per BNF), preferably into the anterior abdominal wall.
MECHANICS OF ADMINISTRATION
MIU will initiate management and then continue treatment until patients have been referred and seen in Anticoagulant Clinic and discharged back to General Practice.
Clexane can cause some local discomfort and local bruising and the area should not be rubbed after administration.
Many patients are happy to self administer. (If patients are unable to self administer then this service will need to be made available via their GP, or practice nurse)
HOUSEBOUND PATIENTS
If patients are unable to self administer or attend MIU, and genuinely housebound then they should not be considered eligible for this ambulatory care model
NB: POSSIBLY A SINGLE DOSE ONLY NEEDED
As many dopplers are NEGATIVE, majority of patients will get a single dose at most.
4) The Doppler Result
If NEGATIVE then the appropriate clinical action needs to be taken.
… another cause for the swollen leg should be assumed. However if the patient is in a high risk probability group on Wells score then a review should take place in 1 week in MIU. There is evidence that some patients in this category based on clinical symptoms and signs require a second scan after 7 days
If POSITIVE, diagnosis of DVT now confirmed - patient needs to commence Warfarin (see below for referral mechanisms) ….. and some thought should be given to the underlying cause ….
If the patient is under 45 with a “spontaneous DVT” i.e no obvious cause then on discharge back to GP it should be suggested that a General Medical referral to outpatients is made for assessment of underlying cause and consideration of thrombophilia screening.
In the cases of recent surgery or recent inpatient admission the relevant surgical and/or admitting team will be informed for audit purposes. If very recent surgery it may be necessary to discuss with the consultant team before starting Warfarin-but continue Clexane to provide prophylaxis against extension of clot, PE etc.
Commencing WARFARIN
This will be done through direct referral to anticoagulant clinic at Singleton or Morriston Hospital. The appropriate referral forms will be completed by MIU including diagnosis, duration of anticoagulation, target INR, and responsible clinician. Referral form in Appendix 1.
The patient needs to have a baseline FBC, coagulation profile, eGFR*, and LFT and baseline INR
Check no contra-indications to Warfarin therapy and check current prescribed & OTC Rx
Decide duration of anticoagulation usually 3 months if this is “first ever” calf vein DVT, and no persistent risk factors. Usually 6 months if this is “first ever” proximal vein DVT, and no persistent risk factors*
*risk factors, e.g.: swelling & pain … to be reassessed at end of 3 or 6-month period
Decide on target INR – usually 2.5.
If recurrent DVT WHILST ON WARFARIN, target INR = 3.5
Continue on same dose of Clexane, until INR is above 2.0, on 2 consecutive checks (days)
The Anticoagulant Clinics will accept patients when the INR is above 2 and patients have withdrawn from Clexane injections. Patients will need to attend MIU for daily INR and dosing prior to this. Patients will be counselled by a Pharmacist prior to Warfarin initiation and given the information package and anticoagulant record.
Further Information-BSH Guidelines on Oral anticoagulation. 3rd Edition (1998)-British Journal of Haematology 101, p-374-387
Compression Stockings
Most people who are diagnosed with DVT require below-knee compression stockings (grade2, 18mmHg to 24mmHg) for a duration of 2years (unless there are contraindications). The prescription for compression stockings should be renewed every 3–6months or so if the stockings are used every day. People with established post-phlebitic symptoms will probably benefit from ongoing use of compression stockings (that is, for more than 2years).
Resource implications
Resource implications will be minimal as the service is already being provided by ABMU NHS Trust. The D-dimer ELISA costs £1.50 more than the present Simpliread test. Swansea SOS will need to invest approximately £2000 in an Adastra upgrade and DVT template
It is anticipated that up to 40% of Doppler ultrasounds could be avoided using the pathway. This will release Doppler ultrasound slots in radiology that can be used for inpatients allowing earlier discharge from hospital saving bed days.
Clinical Responsibilty
Clinical responsibility will rest with SOS and MIU doctors. Once discharged back to General Practice ongoing management then transfers to General Practice. Responsibility for anticoagulation monitoring, (not decision on length of treatment, adverse reaction to Warfarin or other clinical issues) lies with the Anticoagulation Clinic.
Information Technology and Record Keeping
The written pathway document will be used as part of written notes which will include
· GP Referral Document
· Pathway Document
· Hospital Treatment Card
· Test Results
· Anticoagulant Referral
· Adastra GP Discharge Record
An electronic pathway has been established by Adastra the system presently being used by Swansea SOS. It has a DVT template allowing staff to easily input the data required and a quality discharge summary for GPs. The electronic pathway is easy to use and allows for booking of follow ups which is presently done manually.
Discharge procedures and follow up
GP’s will need a robust discharge summary for each patient. Discharge information will need to include diagnosis, investigations, anticoagulation, and need for follow up and further investigation. It is just as important that negative results are reported to GP’s with a possible alternative diagnosis and need for follow up. A DVT discharge summary will be faxed and sent with each patient. All patients will be booked an appointment with their GP for follow up with one week after discharge by MIU receptionist.
Patient discharge information-http://www.patient.co.uk/showdoc/23068982
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