Venous Thromboembolism: Pneumatic Compression Devices in the Prevention of DVT/PE

Authors

Rogers, Frederick B. MD; Cipolle, Mark D. MD, PhD; Velmahos, George MD, PhD; Rozycki, Grace MD; Luchette, Fred A. MD

Author Information

From the University of Vermont, Department of Surgery, Fletcher Allen Health Care (F.B.R.), Burlington, Vermont, Department of Surgery, Lehigh Valley Hospital (M.D.C.), Allentown, Pennsylvania, Department of Surgery, Division of Trauma and Critical Care, University of Southern California (G.V.), Los Angeles, California, Department of Surgery, Emory University School of Medicine, Atlanta, Georgia, and Department of Surgery, Division of Trauma, Critical Care, and Burns, Loyola University Medical Center (F.A.L.), Maywood, Illinois.

Submitted for publication September 1, 2001.

Accepted for publication March 15, 2002.

Any reference in this guideline to a specific commercial product, process, or service by trade name, trademark, or manufacturer does not constitute or imply an endorsement, recommendation, or any favoritism by the authors or EAST. The views and opinions of the authors do not necessarily state or reflect those of EAST and shall not be used for advertising or product endorsement purposes.

Address for reprints: Frederick B. Rogers, MD, University of Vermont Department of Surgery, Fletcher Allen Health Care, 111 Colchester Avenue, Burlington, VT 05401; email: frederick.rogers@vtmednet.org.

Statement of the Problem

The role of intermittent PCDs for prophylaxis against DVT has been studied and increasingly used in general surgery patients,^[32] orthopedic patients,^[33][34] and trauma patients.^{[4][5][7][22][35][36]}

Attacking the long-recognized risk factor of stasis, PCDs have been shown to increase mean and peak femoral venous blood velocities in the lower extremity.^[37] In addition, PCDs have been shown to have a direct effect on the fibrinolytic pathway that acts to shorten the euglobulin lysis time, increases levels of coagulation cascade inhibitor molecules, and affects the balance of plasminogen activation.^[38][39] In a number of prospective randomized studies, PCDs have been shown to reduce the incidence of both DVT and PE.^[7][36][40] Unanswered questions regarding the use of PCDs include the mechanism by which PCDs act, the efficacy of PCDs worn on the upper extremities or a single lower extremity compared with both lower extremities, the nature of risk involved in discontinuing PCDs periodically during use, and the duration of PCD use. Reports suggest that PCDs should be worn with thromboembolism-deterrent stockings (TEDS); however, this practice has not been widely used. Complications of PCDs have been noted in case reports and have been associated with improper positioning of the lower extremity during surgery, which should be avoided.

Process

A MEDLINE search from 1986 to the present produced a large number of articles on this topic. Those articles pertinent to trauma-related thromboembolism prevention were reviewed. Twenty-three of these trauma-related articles were evaluated to formulate the following guidelines (Table 4).

Recommendations

A. Level I: A Level I recommendation on this topic cannot be supported because of insufficient data.

B. Level II: A Level II recommendation on this topic cannot be supported because of insufficient data.

C. Level III: In a meta-analysis of pooled studies on the benefit of PCDs in trauma patients, no benefit of the use of PCDs over no prophylaxis was reported.^[22] In the subset of head-injured patients,^[3][41] PCDs may have some benefit in isolated studies.

Scientific Foundation

The factors that are felt to form the basis of the pathophysiology of venous thromboembolic disease are stasis (reduction of blood flow in the veins), injury (to the intimal surface of the vessel), and hypercoagulability. Scientific and clinical evaluations of PCDs strongly suggest that the nature of the effect on DVT prophylaxis derives from their ability to increase mean and peak femoral vein velocity and possibly affect the systemic coagulation and fibrinolytic mechanisms.

Keith et al.^[37] measured peak venous velocity (PVV) at the common femoral vein using Doppler ultrasound in postoperative nontrauma patients and in healthy control subjects. In the control subjects, PVV was increased from a mean velocity of 23.8 cm/s at rest to 45.5 cm/s with knee-high PCDs and 53.2 cm/s with thigh-high PCDs. In postoperative patients, the PVV was similarly raised from a resting velocity of 21.8 cm/s to 55.1 cm/s. In both of these evaluations, the differences were statistically significant when compared with controls and were not further augmented by the concomitant use of TEDS. Spectral recording of blood flow velocity during inflation and deflation of the PCDs revealed a temporal association with inflation and increased PVV that suggested a mechanical effect derived from inflation of the PCDs.

Studies^[38][39] have evaluated in vivo fibrinolytic effects of PCDs. In a well-designed study, Jacobs et al.^[39] showed that euglobulin lysis times were not reproducible as a marker for fibrinolytic activation. Their study focused on measured changes in tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI-1), and tPA-PAI-1 complex. They demonstrated a significant increase in tPA-PAI-1 (hence an obligatory decrease in PAI) in patients undergoing pneumatic compression and postulated a (complex and incompletely proven) role of PCDs in the systemic balance of plasminogen activation and inhibition. They found that fibrinolytic activity began to decay within minutes of discontinuing PCDs. This observation proved to have important clinical implications in that PCDs must be worn continuously to avoid rapid decay in fibrinolytic activity. A recent study documented patients in whom PCDs have been ordered, but who spent less than 50% of the time actually wearing the devices, which possibly decreased their effectiveness.^[31] Another important finding in the study by Jacobs et al. was that there appeared to be an incremental decrease in fibrinolytic activity when blood was sampled in sites remote from the area of PCD placement. This difference in local and systemic effects has important implications on the ability of PCDs worn on the arms to prevent DVT in the legs.

A paucity of studies exists specifically regarding the use of PCDs in trauma patients with multiple injuries. In a prospective study by Knudson et al.,^[15] 113 trauma patients received either PCDs and TEDS or LDH. This study showed a 12% rate of VTE in the PCD group versus 8% in the LDH group, which was not significantly different. This study did not demonstrate that either method of attempted prevention (LDH or PCD) was better than no prophylaxis. Dennis et al.^[7] conducted a prospective, nonrandomized study of 395 trauma patients admitted with an ISS > 9 who received either PCDs, LDH, or no prophylaxis, and who underwent serial ultrasound screening for DVT at 48 hours, 5 days, and 10 days after admission. They demonstrated a VTE rate of 8.8% in the no-prophylaxis group, 2.7% in the PCD group, and 3.2% in the LDH group. No statistically significant difference was noted in VTE rates in the prophylaxis groups, but a significant difference was seen in those who received prophylaxis versus no prophylaxis (p < 0.02). Head- and spinal cord-injured patients, two very-high-risk groups, seemed to benefit greatly from prophylaxis. Overall, risk reduction of VTE with prophylaxis was from 16.7% to 1.4% in head-injured patients and 27.3% to 10.3% in spinal cord-injured patients. However, problems occurred during the course of this study in that 67 patients (37%) originally assigned to receive no prophylaxis were switched to receive some sort of prophylaxis at the discretion of the attending surgeon. This may have confounded the DVT rates for each prophylactic modality assignment. In a prospective trial, Knudson et al.^[3] compared PCD, LDH, and no prophylaxis. Neither LDH nor PCD appeared to offer any protection to trauma patients with multiple injuries, except in the specific subgroup of patients with neurotrauma in which PCD was more effective in preventing DVT than control (p = 0.057). In contrast to the study by Knudson et al., Gersin et al.,^[35] in a nonrandomized prospective study, looked at the incidence of VTE in a group of 32 severely head-injured patients with Glasgow Coma Scale (GCS) scores < 8. Fourteen patients received PCDs and 18 did not because of concomitant lower extremity fractures. Within the group receiving PCDs, four (28%) developed PE and none developed DVT. In the group not receiving prophylaxis, two developed PE and two developed DVT. Although the study population was small, the findings in this study questioned the efficacy of PCD even in severe head-injured patients. In a group of 304 orthopedic trauma patients with hip and pelvic fractures, PCDs were found to reduce thromboembolic events significantly over those who had no prophylaxis (11% vs. 4%;p = 0.02). In subgroup analysis, PCDs were only effective in the hip fracture group, not in those with pelvic fractures.

Compression devices appear to be well-tolerated, with minimal side effects. Isolated cases of pressure necrosis from a too tightly fitted PCD have been reported.^[42] Also, peroneal palsy and compartment syndromes have been reported with PCDs.^[43] A potential complication of PCDs is elevated intracranial pressure (ICP) in patients with severe head injury. This was addressed by Davidson et al.^[41] in 24 severely brain-injured patients (mean GCS score of 6) who had ICP and cerebral perfusion pressure (CPP) calculated after 0, 10, 20, and 30 minutes of intermittent pneumatic leg compression. The authors found no significant increase in ICP or CPP with the use of PCDs at any time points, and concluded that PCDs can be used safely in stable head-injured patients.

In an evidenced-based meta-analysis sponsored by the Agency of Healthcare Research and Quality on the incidence of DVT after trauma, Velmahos et al.^[22] found that PCDs offered no benefit over no prophylaxis in both pooled randomized control studies (OR, 0.769; 95% CI, 0.265-2.236) and in pooled nonrandomized controlled studies (OR, 0.527; 95% CI, 0.190-1.460). In another study, Velmahos et al.^[5] compared PCD, LDH, and a combination of PCD and LDH in a prospective study of 200 critically injured patients followed by weekly Doppler ultrasound to detect proximal DVT. In all three groups, the proximal DVT rate was 13%, leading the authors to question whether any of the three prophylactic regimens were sufficient in the high-risk patient.

Summary

Clinical studies demonstrating the effectiveness of PCDs in trauma patients are few. Although the exact mechanism of action of PCDs is unknown, their effect is believed to be based on a combination of factors addressing stasis (which is well accepted) and the fibrinolytic system (which is less clear). Until these mechanisms are better studied and understood, answers to specific questions regarding the appropriate use of PCDs are forthcoming.

Future Investigation

More studies need to be performed specifically relating to the use of PCDs in trauma patients at risk for VTE. Questions regarding the efficacy of using the device on one lower extremity versus two, and whether an arm versus a leg provides equal protection, all need to be addressed. A number of commercial vendors supply compression devices. Whether all compression devices provide equal protection or whether one vendor's brand is superior needs to be determined. PCD effects on the fibrinolytic system need to be better elucidated and the contribution (if any) of the changes of PCDs on the fibrinolytic system in the prevention of VTE needs to be further delineated. Finally, the role of multimodality therapy (mechanical and pharmacologic) to provide any additional protection from VTE needs to be ascertained.

Acknowledgment

We thank Jody Ciano for her help in the preparation of this article.

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Table

Pneumatic Compression Devices