High Risk Groups for Deep Venous Thrombosis (DVT) and
Pulmonary Embolus (PE) in General Surgery, Orthopedic Surgery and Trauma, to
Include Combat Injury Considerations
Submitted by Donald H Jenkins, MD, FACS, Lt Col, USAF, MC
Surgery and Trauma Patient Population
Typically, trauma and surgical patients have no underlying clotting disorder but are at 12-18 times more likely to develop DVT/PE than they were at baseline. Injury to body tissues, whether by surgery or trauma, increases the risk of DVT which can occur within hours; even during operation (some reported < 2 hours). Over 50% of DVT occur within 7 days and 90% occur within 21 days of the „event‟. There are certain surgical sub-groups which can have
even higher risk.
Acquired and Inherent Risk Factors in Surgery and Trauma
Non-surgical factors which increase the risk of venous thromboembolism (VTE) in surgical patients include: obesity, cancer, prior DVT/PE, pregnancy, certain medications (birth control), IV line placed in large central vein, > 72 hour ICU stay, and kidney failure. Surgical factors which increase the risk of VTE include: pelvic surgery (gynecology and urology surgery), orthopedic surgery (hip/knee replacement or fracture repair), and prolonged immobilization (similar to long plane flight, 3 or more days in hospital). Trauma-specific VTE risk factors include: spinal cord paralysis injury, multiple limb fractures, pelvis/hip socket (acetabulum) injury, use of clotting medications (rVIIa) or transfusions (platelets). This is the ultimate conundrum for the surgeon: stop bleeding without causing unnecessary and unwanted excess clotting.
Screening for DVT
Physical exam is less than 50% accurate in determining whether or not the patient has a DVT. Therefore, one must rely on other means of determining the presence of DVT. The primary screening tool is Duplex Ultrasound of major veins. Using this technique, US waves can show blood clots in major veins of legs, groin, arms, neck and abdomen. The exam is ideally done at the patient‟s bedside, is essentially risk free, and is repeatable. A recent study in a medical/surgical ICU population, using DVT prevention measures in over 90% of their patients, showed 10% of patients with DVT and 10% of those developed lung blood clot (pulmonary embolus-PE) using this screening method. X-ray studies (CT scan, venogram) can also be used but there are caveats: requires contrast dye use, is not more sensitive, can cause kidney injury and must be done in x-ray department.
Risk Factor Modification in Surgery/Trauma
Risk stratification in DVT/PE has been well defined in surgery and trauma. This stratification includes: any surgery or injury, any additional risk factors (previously outlined), more than one risk factor. Dependant on the presence of and number of these risk factors, the patient is placed into a high, medium or low risk group. Then prevention measures are based on risk group. Guidelines for prevention and risk stratification are well outlined in the literature: Eastern Association for Surgery of Trauma and American College of Chest Physicians are two examples of guidelines for surgery and trauma patient risk stratification and prophylaxis.
Early ambulation is the easiest mechanical preventive strategy but is not possible in OR and is not possible for many of highest risk patients undergoing lower extremity surgery. Sequential compression devices (inflatable stockings worn on legs) are essentially risk free but can‟t be used for all patients (leg injury or surgery). These devices can be used during and after operations and are quite effective. The most controversial mechanical preventive strategy is use of Vena Cava (main abdominal and chest vein) filters. These filters are small wire cages placed in the vena cava to prevent PE. It is inserted by radiologists or surgeons in special x-ray suites and the latest technology allows removal of filter once risk of PE minimal (~3 weeks after injury or surgery). Filters do not prevent DVT; in fact they may increase the risk of DVT formation. Filters remain controversial due to long term complication risks, lack of data to show decrease in mortality but effective in PE prevention in patients unable to get other prophylaxis (risk of hemorrhage and both legs injured).
Heparin is a „blood thinner‟ anticoagulant medication with rapid onset (within minutes)
and is given by IV or subcutaneous injection once or twice a day or by an IV drip. It is now available in various low molecular weight versions which are equally potent with lower side effect (bleeding) profile but may require blood tests to monitor and can be used during operations as well as at home. Coumadin is a daily pill anticoagulant that is slow in onset (days), must be monitored with frequent blood tests, has increased risk of bleeding complications compared to heparin but does have a long track record of success. Coumadin is typically not administered during operation (stopped several days before surgery) due to the bleeding risk.
Combination Preventive Strategies
The combination of mechanical and chemical measures may yield the best results as the preventive effects are additive. Combination prevention is recommended in higher risk groups, are best used in OR at beginning of operation or as soon after injury as feasible (within hours/days) but are limited, as one cannot always use anticoagulants due to risk of bleeding in this patient population.
Complications of prophylaxis
Risks associated with preventive measures are dependent on the type of preventive strategy. Mechanical stockings cannot be use in all patients and are less effective than chemical or combined treatment; therefore, the risk of DVT/PE is higher. Vena Cava filters decrease PE but increase risk of DVT long term and have no proven decreased death rate. Removable filters may be best temporary measure in highest risk group unable to use other measures but should be removed when the risk is decreased or when other preventive strategies can be implemented. Chemical preventive strategies can cause hemorrhage. Bleeding is a problem after operation or injury, especially with organ injury or brain/spine surgery; and limits or delays the ability to use this form of prevention. Rarely, a platelet decrease disorder occurs (heparin induced thrombocytosis or HIT) and chemical prophylaxis must be discontinued.
Bottom line up front, I think that clinical teams need reminding about the importance of DVT/PE prevention and that we need pneumatic compression devices added to the inventory for Level II and III facilities (field surgical hospitals) and in the Critical Care Air Transport Team/Aeromedical Evacuation (CCATT/AE) system. The quick tempo of injury, surgical intervention and evacuation out of theater often does not allow DVT/PE preventive strategy to „kick in‟ prior to evacuation. Several categories of patients (ambulatory, severe brain injury, etc) may not routinely get prophylaxis and some of them (ambulatory with minor injury) don't need it. Sometimes, however, physicians just simply forget.
Blast injury seen in theater today is a unique injury mechanism not often seen in the civilian environment. High-explosive (HE), thermobaric, and nuclear detonations cause extreme compression of molecules in surrounding air or water creating thin bands of locally high overpressure, which are propagated away from the origin of the explosion as a blast shock wave. Most casualties within the injury radius of a HE detonation will have common penetrating, blunt, and burn injuries managed no differently than similar non-blast trauma. When the blast wave arrives at the surface of an object (vehicle, structure, or human body), it is transmitted into that object as a stress wave. As the blast wave separates from the stress wave due to the latter moving slower through objects than the blast wave moves around them, pressure differentials cause forces that accelerate surfaces. When transmitted into the human body, the shock wave causes stress-induced tears at air-tissue interfaces, which result in internal bleeding, weakening of tissue resistance to additional insults, and possible rupture with escape of air from the respiratory tract or spillage of gastrointestinal contents. This HE blast effect may cause increased risk of DVT/PE formation in combat casualties.
The problem often times precedes entry into the AE system. There are several civilian case reports of patients dying of PE within 6 hours of injury. In another scenario, if a patient with liver fragmentation wound is operated upon, put into ICU, CCATT mission generated, the post-operative orders most often state to start low molecular weight heparin (LMWH) 24 hours post-op (many surgeons don't want to give it in solid organ injury, or brain injury, right away). CCATT often times has that patient out in 6 hours and to Germany before the first scheduled dose of LMWH can be given. The standard order set at the Air Force Theater Hospital in Balad, Iraq specifically calls for LMWH to begin at 24 hour point for the severely brain injured patients.
Information that is missing from our military system as it relates to DVT/PE includes several things: the number of thrombotic and thromboembolic events, information on what, if any, prophylaxis was used in those cases (including timing) and surveillance mechanism at Level IV and V (major hospitals in Germany and the USA) to detect asymptomatic DVT to define the true incidence in our combat casualties. I suspect several of the patients who developed DVT/PE did get prophylaxis. The question would involve timing and dose and combination preventive strategy and screening. Also, no real data exists on AE-system related stressors which may exacerbate DVT/PE rates other than immobility (accelerative/decelerative forces, lower ambient oxygen tension, dehydration, vibration, immobility for extended periods during AE process, elevation in thrombin-antithrombin complex, etc) which may not affect patients in the regular hospital setting but do affect the combat casualty in our echelons of care system.
In the DoD CONUS trauma system, intermittent pneumatic compression devices are used routinely, beginning in the OR. Unfortunately, we don't have that in theater and we also don't have a great body of trauma literature about use of LMWH without pneumatic devices, as it is
such a routine part of care back home. There also are not any pneumatic devices currently in use or even approved for flight. While the exact impact pneumatic compression device use might have is unknown, based on the CONUS trauma experience, suspect it could be of great benefit for those patients not immediately put on LMWH prophylaxis, at a minimum. All military field hospitals in theater have procured pneumatic compression devices for use on combat casualties but these devices are not a part of the standard inventory.
Regarding policy formation on DVT/PE prevention, a theater-wide policy is in place (attached) which is a strong statement about use of DVT/PE prevention for all at-risk patients (every litter patient with an injury and any litter DNBI patient with usual/standard risk factors). This protocol includes drug/dose of choice. Another avenue is the use of a template AE request form (3899) to facilitate and remind the providers regarding the use of DVT/PE prevention; it is pre-printed on the form, along with many other commonly used medications for the combat casualties and is thus used or simply deleted from the e-form when not applicable, as it is easier than typing in all the medications being used.
Vena Cava filters are available for very select use in theater. There are clear indications for IVC filter placement for treatment and controversial indications for prophylactic IVC filter placement. The two DoD CONUS Level I trauma centers (Brooke Army Medical Center and Wilford Hall Medical Center) base DVT/PE preventive measures on the EAST guidelines, including indications for IVC filter placement. IVC filters are a tiny part of the answer and would require a tremendous increase in interventional radiology footprint in theater but would rarely be indicated in US casualties. The vast majority of casualties transported out of theater have no indication for IVC filter placement. Unfortunately, little/ no information exists on those casualties who developed DVT/PE at CONUS facilities; a clear priority for further research. Another area of research interest would be the long-term outcome (morbidity and mortality) of those casualties who develop DVT/PE.
DVT and PE can be prevented in 90% or more of surgical and trauma patients without additional risk factors by use of a systematic preventive strategy. The risk of DVT, PE and death related to PE in high risk surgical and trauma patients is significantly reduced by 60-70% using a preventive strategy. Mechanical and/or chemical preventive strategies should be individualized based on patient risk factors found in existing guidelines. Screening for DVT in high risk groups using Duplex US is cost-effective and should be part of comprehensive DVT prevention strategy. Combat casualties are at higher risk of DVT/PE for numerous reasons and should be further studied.
Timing of Pulmonary Emboli after Trauma: Implications for Retrievable Vena Cava Filters. Sing RF, Camp SM et al; J Trauma 2006; 60:732-735
Deep Venous Thrombosis in medical-surgical critically ill patients; prevalence, incidence and risk factors. Cook D, et al. Crit Care Med 2005; 33:1565-1571
www.east.org (trauma practice guidelines)
Sixth ACCP Consensus Conference on Antithrombotic Therapy, CHEST; 119:1(Supplement) January 2001
Blast Injuries: Recognition and Management Lt Col John Wightman, USAF, MC in Operational Medicine 2001, Health Care in Military Settings NAVMED P-5139 May 1, 2001
Use of Emboli-blocking Filter Increases, but Rigorous Data are Lacking, Brender E, JAMA March 1, 2006, V 295 N 9
Retrievable vena cava filters in trauma patients for high-risk prophylaxis and prevention of pulmonary embolism, Allen TL, Carter JL, et al: Am J Surg 189 (2005) 656-661
Medical Literature and Vena Cava Filters: So Far So Weak, Girard P, Stern JB and Parent F: Chest 2002; 122; 963-967
Eight-year Follow-up of Patients with Permanent Vena Cava Filters in the Prevention of Pulmonary Embolism, The PREPIC Randomized Study, The PREPIC Study Group: Circulation 2005; 112:416-422
A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein throbosis, Decousus H, Leizorovicz A, et al: N Eng J Med Feb 12 1998 V 338, Iss 7, 409-415
Thromboembolic Adverse Events After Use of Recombinant Human Coagulation Factor VIIa, O‟Connell KA, Wood JJ, et al: JAMA Jan 18, 2006 V295 N 3; 293-298
Use of Recombinant Activated Factor VII to Treat the Acquired Coagulopathy of Trauma, Holcomb JB: J Trauma 2005; 58: 1298-1293
Treatment of Deep-vein Thrombosis, Bates SM and Ginsberg JS: N Eng J Med 2004:351; 268-277
Schreijer AJ et al, Lancet 2006; 367:832-838
ANTITHROMBOTIC THERAPY FOR THE PREVENTION AND TREATMENT OF
THROMBOSIS IN A THEATER OF OPERATIONS
a. Sixth ACCP Consensus Conference on Antithrombotic Therapy, CHEST; 119:1(Supplement) January 2001.
b. Scurr JH; Machin SJ; Bailey-King S; Mackie IJ; McDonald S; Smith PD, “Frequency and
Prevention of Symptom-less Deep Venous Thrombosis in Long Haul Flights: A Randomized Trial, Lancet 2001 May 12;357(9267):1485-9
c. JCAHO Accreditation Manual for Hospitals, current edition
2. PURPOSE. The purpose of this memorandum is to establish guidelines for antithrombotic therapy for the prevention and treatment of thrombosis.
3. APPLICABILITY. This memorandum applies to personnel assigned or attached to OIF intra-theatre medical facilities who are involved in the management of patients.
a. The Sixth American College of Chest Physicians Conference recommended that, “every hospital should develop a written policy or other formal strategy for preventing thromboembolic complications, especially for high-risk patients.”
b. Proximal deep venous thrombosis (DVT) continues to be a frequent illness in hospitalized patients. Pulmonary Embolism, a very serious potential outcome has been seen in up to 20% of patients hospitalized with DVTs in national reviews.
c. There is an increasing recognition of deep venous thrombosis in individuals who complete an extended period on an airplane. One study noted a 10% prevalence of asymptomatic DVT in individuals undergoing flights of 8 hours or more.
a. All Health Care Providers will:
(1) Become familiar with the guidelines for the prevention of venous thromboembolism (see Appendix A).
(2) Appropriately manage patients who may be at risk of a thromboembolism.
(3) Provide feedback on these guidelines and suggestions for changes to the Chief of Professional Services of the MEDCOM (Medical Command).
b. Chief, Surg/Med QA Committee
(1) Review all thromboembolic events in the Level III facility to assess ways to reduce the risk to the patient.
(2) Coordinate with the CPS of the MEDCOM or Theatre Trauma Coordinator, on the appropriateness of the guidelines being used and update on an as needed basis.
c. Chief of Professional Services of the MEDCOM and Theatre Trauma Coordinator will:
(1) Be the subject matter experts on the guidelines to be used in the entire OIF theatre
for antithrombotic therapy for the prevention and treatment of thrombosis.
(2) Coordinate with the Chief Med/Surg QA of the particular Level III facility, on the
appropriateness of the guidelines being used and update on an as needed basis.
APPENDIX A: Prevention and Treatment of Thrombosis Guidelines
Risk Group Recommended Prophylaxis
Low Risk (minor procedure in patients < 40 yr, no Early ambulation
additional risk factors
Moderate Risk (minor procedure with additional Low molecular weight heparin (LMWH) 30-40
risk factors for thrombosis; non-major surgery in mg sc BID and intermittent pneumatic patients 40 to 60 yrs, with no additional risk factors; compression (IPC) device
major surgery in patients < 40 yrs with no additional LDUH (low dose unfractionated heparin) only if
risk factors LMWH not available
Early ambulation, as possible
Higher risk (non-major surgery in patients >60 yr, or LMWH and IPC device
with additional risk factors, major surgery in Early ambulation, as possible
patients > 40 yrs, or with additional risk factors)
All litter patient transfers out of theatre
Higher risk, with greater than usual risk for bleeding Mechanical prophylaxis with IPC device, at least
Very High Risk (multiple risk factors) Effective pharmacologic method (LMWH)
combined with mechanical methods (IPC
Emergency trauma surgical procedures in all Low molecular weight heparin (LMWH) and patients, if not contraindicated intermittent pneumatic compression (IPC) device
Low-dose unfractionated heparin (LDUH) if
LMWH not available
Very high risk trauma emergency surgery as Higher doses of LMWH and IPC device, possible determined by the operating surgeon (spinal cord IVC filter
injury, pelvic fracture with long bone fracture, multiple long bone fractures)
Transurethral surgery, or other low-risk procedure Prompt mobilization
Major open urologic procedure Routine prophylaxis: LDUH, ES, IPC device, or
Highest-risk patients Elastic Stockings (ES) with or without IPC
device PLUS LDUH or LMWH
MAJOR ORTHOPEDIC TRAUMA SURGERY
Emergency major orthopedic surgery of extremities, LMWH therapy if not contraindicated
pelvis and spine. Mandatory IPC device if technically possible.
Higher doses of LMWH and IPC device, possible
IVC filter (We do not recommend sole therapy
with LDUH, aspirin, dextran, or IPC device)
Risk Group Recommendations
Prophylactic anticoagulant therapy is recommended
for at least 7 to 10 d after surgery
Recommend outpatient prophylaxis with LMWH be
offered beyond 7 to 10 d after major orthopedic
surgery, at least for high-risk patients
Do not recommend routine duplex ultrasonography Do recommend routine duplex at the receiving screening at hospital discharge or during outpatient institution after evacuation to LRMC and/or
follow-up in asymptomatic patients. CONUS, especially for highest risk groups
despite signs/symptoms (present in < 50%)
NEUROSURGERY, TRAUMA, AND ACUTE
SPINAL CORD INJURY
Intracranial neurosurgery IPC device
High-risk patients: IPC device with postoperative
LMWH may be more effective than either
prophylactic modality alone; timing of
chemoprophylaxis on case-by-case basis
Neuro trauma, with identifiable risk factor for Prophylaxis with LMWH, as soon as considered thromboembolism safe; if delayed, or contraindicated because of
bleeding concerns: initial use of IPC device, or
If prophylaxis is suboptimal, offer weekly
screening of high-risk patients with duplex
If proximal DVT is demonstrated and
anticoagulation is contraindicated, we
recommend inferior vena cava (IVC) filter
insertion, but we do not recommend IVC filter
insertion as primary prophylaxis
Acute spinal cord injury Prophylaxis with LMWH and IPC
We do not recommend LDUH, ES, or IPC as
In the rehabilitation phase, we recommend
continued LMWH therapy, or full-dose oral
Acute myocardial infarction Most patients: prophylactic or therapeutic
anticoagulant therapy with SC LDUH or IV
Ischemic stroke, with impaired mobility Routine use of LDUH, LMWH, or danaparoid
If anticoagulant prophylaxis is contraindicated:
General medical patients with risk factors for VTE LDUH or LMWH (with IPC for litter and bed (eg, cancer, bed rest, heart failure, severe lung ridden patients)
disease) especially consider for patients arriving
after >8 hr air evacuation
Sample of Standard Order Set to Enhance DVT Prevention Algorithm Compliance
Date/Time of Order
and Signed Antibiotics.
Patient with Open Fx,
Shock, Active Infection,
Transport, or Heavy
?Imipenum 500 mg IV q 6hr x
48hrs or Meropenum 1 gm IV q
8hr x 48hrs (select according to
Major Soft Tissue Wounds
?Unasyn 3gm IV q6hrs x 24hrs &
Amikacin 15mg/kg IV qd x 1
dose (estimate weight ________)
?Levofloxacin 500mg IV qd x
24hrs & Amikacin 15mg/kg IV
qd x 1 dose (For PCN Allergic
Patients Only) (est weight _____)
GI Prophylaxis. ? Zantac 50 mg IV q 8 hrs.
? Protonix 40 mg IV q day.
DVT Prophylaxis. ? Heparin 5000 units SC BID.
? Lovenox 30 mg SC BID.
? Lovenox 40 mg SC q day.
? IV Insulin gtt, titrate to BG Other Medications.
<140 & >100.
? Tetanus 0.5 cc SC x 1.
? Epogen 40,000 units SC q week
REPLACES EDITION OF
1 JUL 77, WHICH MAY Subject to the Privacy Act of 1974
BE USED Page 4 of 4