Postoperative venous thromboembolism causes substantial morbidity and mortality. Thrombosis occurs in as many as 15–30% of major gynecologic surgeries, and cesarean delivery is associated with a fivefold to 10-fold increased risk of thrombosis compared with vaginal delivery.1–3 The annual incidence of venous thromboembolism in women is 110 per 100,000.4 The American College of Chest Physicians and the American College of Obstetricians and Gynecologists (the College) both have guidelines for risk stratification and prevention strategies.5,6 Mechanical prophylaxis with sequential compression devices or compression stockings and pharmacologic prophylaxis with low-molecular-weight or unfractionated heparin are well-established methods for venous thromboembolism prevention.
Although use of sequential compression devices is included in major Society recommendations, compliance in postoperative benign gynecology surgery and cesarean delivery settings has not been well studied. Studies in gynecologic oncology patients show external pneumatic calf compression and low-dose heparin are similarly effective in preventing postoperative venous thromboembolism with unfractionated heparin associated with a higher rate of bleeding complications compared with low-molecular-weight heparin.7–9 The College recommends that pneumatic compression devices “should be used continuously until ambulation and discontinued only at the time of hospital discharge,”6 a recommendation based on Level III evidence from the 2004 American College of Chest Physicians guidelines. Recommended timing of sequential compression device use is placement “before initiation of surgery and [continuation] until the patient is fully ambulatory.”6 The purpose of this study was to determine sequential compression device compliance and assess if nursing and patient education about venous thromboembolism prevention improves compliance in patients undergoing benign gynecologic surgery and cesarean delivery.
MATERIALS AND METHODS
We conducted a prospective observational study of postoperative patients on the gynecology and postpartum services at the Virginia Commonwealth University Health System. The protocol was approved by the health system's institutional review board. All English-speaking patients who underwent benign gynecologic surgery or cesarean delivery and were prescribed to wear sequential compression devices postoperatively were included in the study. Non–English-speaking patients and patients who had surgery for a gynecologic malignancy were excluded. Nine percent of patients undergoing cesarean delivery were non–English-speaking. There were no exclusions in the gynecologic surgery group because all spoke English.
It is the practice at the study institution that all patients undergoing cesarean delivery are prescribed knee-length sequential compression devices throughout hospitalization. Similarly, patients undergoing gynecologic surgery are prescribed prophylaxis per College guidelines with sequential compression devices being favored for moderate-risk and high-risk patients until discharge. The electronic medical record order at the study institution reads “Intermittent venous compression hose, knee length, both legs.” Typical reapplication of a patient's sequential compression device may be by a nurse, either at the nurse's or patient's request, by a family member, or by the patient herself depending on her pain level and mobility.
The study was divided into four 30-day segments. This amount of time was arbitrarily chosen based on feasibility. The first segment consisted of baseline observations of compliance by a coauthor. During the second segment, the College’s patient pamphlet “Preventing Deep Vein Thrombosis” was distributed and explained to each patient by an investigator before initiation of observations. This explanation occurred on the postpartum or women's postsurgical care unit at least 4 hours after surgery. A typical interaction consisted of a coauthor giving the patient a pamphlet, explaining the consequences of venous thromboembolism, and the role of sequential compression devices in preventing thromboembolic complications. Patients were instructed how to unsnap the tubing from the sleeves to allow ambulation. This interaction was focused and took approximately 3 minutes. The third month's observations took place after nursing staff individually viewed a 19-slide educational PowerPoint presentation created by the authors about venous thromboembolism incidence, prevention, and consequences. Material for this presentation was collected from the American College of Chest Physicians and College guidelines.5,6 The final month included both interventions with nursing staff having previously viewed the PowerPoint presentation and patients again receiving educational pamphlets and focused explanations.
All observations were made by the same two investigators. They made twice-daily patient observations at least 4 hours apart on all study patients and assessed if sequential compression device sleeves were applied, if the tubing was attached to the sleeve, and if the machine was powered on. Observations occurred between 5 AM and midnight. Observations continued twice daily until the patient was discharged. Neither patients nor nurses were made aware of the study observations to avoid bias.
A patient was defined as “compliant” if she was lying in bed with sequential compression devices applied, tubing attached, and machine powered on or ambulating or sitting in a chair (with or without sequential compression devices applied). All other observations were categorized as noncompliant. A patient lying in bed without sequential compression devices on and functioning properly was categorized as noncompliant. If sequential compression devices were not being worn while a patient was in bed, the observer asked the patient for a reason and offered to assist with reapplication of the device. If the patient declined reapplication, it was recorded as a refusal.
Continuous data among the four intervention months were analyzed by analysis of variance and Tukey’s honest significant difference post hoc tests. Categorical data were analyzed by χ2 tests. Compliance rates were analyzed using all of each patient's observations. Because the serial observations were not independent, a confirmatory analysis was performed with only the first observation from each patient. Logistic regression was used to evaluate whether compliance and refusal of reapplication of sequential compression device changed with each successive postoperative day.
To evaluate whether the relationship between postoperative day and compliance was independent of the specific intervention month, multivariate logistic regression was performed with the intervention month as a covariate. Variables were included as potential covariates if their univariate P values were <.25 or if inclusion changed the main effect odds ratio (OR) estimate by more than 20%. Variables included were age, body mass index (calculated as weight (kg)/[height (m)]2), insurance type, postoperative day, total number of observations, and time of day at observations. Time of day was categorized as morning (5 AM to 11:59 AM), afternoon (noon to 5:59 PM), and evening (6 PM to midnight). Preliminary multivariate models were compared using −2 log likelihood tests before a final multivariate model was constructed. Values <.05 were deemed statistically significant.
Based on the limited previously published prospective observational studies,10,11 it was assumed the adherence rates in the no-intervention, patient education, nurse education, and combined education segments would be 50, 60, 70, and 80%, respectively. Given the low cost and easy implementation of the chosen interventions, even a 10% increase in compliance per intervention would be meaningful. Dual interventions would not necessarily be additive. Nursing intervention was hypothesized to have a greater association than patient education given patients often follow suggestions of the nurses who make multiple contacts with them throughout the day. Using these proportion assumptions, the average adherence rate was 0.65 with a trend of 0.224 and variance of 0.207. For a two-sided test for linear trend (logistic model) and an α of 0.05, 35 patients for each month would be needed to achieve a power of 80%.
A total of 859 observations was recorded for 228 patients during the study period of October 2012 to April 2013. The number of hospitalization days ranged from 1 to 13. The mean was 2.40 days with a median of 2 days. Race, age, body mass index, insurance, and surgery type were not different among the four segments (Table 1). Ninety-two percent of nurses completed the educational program during the nursing intervention segment. There was no difference in compliance among the months with 141 of 230 (61.3%), 106 of 194 (54.6%), 155 of 277 (56.0%), and 95 of 158 (60.1%) compliance for each consecutive month (P=.44; Table 2). There was also no difference between months in the analysis including only the first observation for each patient (P=.085). Only 4.4% of patients had additional venous thromboembolism prophylaxis such as compression stockings or heparin ordered.
Overall, cesarean delivery was associated with fewer compliant observations compared with gynecologic surgeries (272/519 [52.4%] compared with 225/340 [66.2%], P<.001). Among the benign gynecologic surgeries, patients undergoing laparoscopy had the most compliant observations (n=41 [73.2%]), whereas patients undergoing vaginal surgery had the fewest (n=35 [61.7%]). Combining all four segments of data, noncompliance increased with each successive postoperative day (adjusted OR 1.18 per day, 95% confidence interval [CI] 1.07–1.30; P=.001). The association of postoperative day on compliance was independent of intervention. After adjusting for the intervention segment, postoperative day remained significantly associated with noncompliance (adjusted OR 1.17, 95% CI 1.06–1.30, P=.002; Fig. 1).
We examined whether time of day was different for the four segments and there were differences among months (P=.002; Table 1). Month 1 has the most afternoon observations (45.7%) and month 3 has the most morning observations (54.5%).
The relationship between postoperative day and compliance was evaluated for potential cofounders. Univariate analyses of potential confounders and compliance are presented in Table 3. The final model contained the terms postoperative day, age, surgery type, and intervention segment. Postoperative day remained significantly associated with noncompliance (adjusted OR 1.17, 95% CI 1.07–1.29, P<.001).
When noncompliant patients were asked why they were not wearing their sequential compression devices (n=362), the most common reason was “the nurse said I don't need them anymore” (n=82 [22.6%]). This was followed by “I just got back in bed and no one has reapplied them” (n=59 [17.1%]) and “I've been walking” (n=63 [16.3%]) (Fig. 2). We did not awaken patients who were sleeping to ask this question. Women who were lying in bed and noncompliant were asked if they would allow the investigator to reapply the sequential compression devices properly. These patients were more likely to refuse reapplication of sequential compression devices on each successive postoperative day, with an OR of refusal of 1.21 per day (95% CI 1.02–1.45, P=.03).
Of the 497 compliant observations, 159 (34.6%) were while the patient was sitting, whereas 125 (27.2%) were while the patient was ambulating. Although the patient ambulated to get to her chair, patients who are sitting are not actively ambulating. A secondary analysis was performed to account for those sitting during observations because they were considered compliant in the analysis, but some may argue sitting in a chair does not constitute ambulation, necessitating venous thromboembolism prophylaxis. In this analysis, sitting patients were reassigned to the noncompliant group. There was still no difference in compliance between segments (P=.59). Similarly, greater noncompliance with each successive postoperative day persisted, and this association was independent of intervention (OR 1.42, 95% CI 1.21–1.62, P<.001).
No cases of venous thromboembolism were diagnosed in study participants during the study period.
The study shows that compliance with prescribed sequential compression devices is approximately 58% in patients who have undergone cesarean delivery or major benign gynecologic surgery, and neither patient nor nursing education interventions alone or in combination improved compliance.
The observed compliance rate is comparable to other prospective observational studies. Trauma patients at a tertiary medical center, approximately half of whom were postoperative, had 53% compliance with sequential compression devices.11 Another study noted compliance of 61.5% on a surgical and 48% on a nonsurgical unit. Patient education with a pamphlet that instructed a patient to notify the nurse if sequential compression devices were not applied did not improve compliance rates. Nursing education with a single resident–nursing educational meeting improved compliance on the surgical unit to 65%, an increase that was statistically significant but probably had little clinical relevance.10
Strengths of this study include its prospective design and clear, easy-to-implement, reproducible interventions. The project took place at a tertiary medical center with a patient population characteristic of large teaching hospitals, so results are likely generalizable to other similar populations. The study also recorded patient-reported reasons for noncompliance, which suggest interventions.
Weaknesses pertain to the interventions, which because of their reproducible, inexpensive, and easy-to-implement nature, were also limited in scope. Although 92% of nurses completed the individual educational presentation, comprehension was not evaluated. Patient education may have been limited by being done so soon after surgery. Limiting observations to two per day may underestimate noncompliance because there may have been more episodes that were not observed. However, we would not expect the accuracy to vary by study intervention.
There are contradictory recommendations regarding cesarean delivery. It is the practice at the study institution that all patients are prescribed sequential compression devices as per College recommendations.12 The American College of Chest Physicians has different recommendations in which a patient without other risk factors should not receive prophylaxis other than early ambulation.5 A recently published study identified more than 1 million patients through a multihospital database who had undergone cesarean delivery over an 8-year period. Seventy-five percent of these patients received no venous thromboembolism prophylaxis. Although the rate of prophylaxis increased from 8.4% in 2003 to 41.6% in 2010, use of postcesarean thromboembolism prophylaxis remains inconsistent across the United States.13
There are a number of unanswered questions about sequential compression device use. It is unlikely that 100% compliance is necessary to prevent venous thromboembolism. However, it is unclear how many days of postoperative sequential compression device use are required to reduce incidence of venous thromboembolism, and there is ambiguity in the current recommendations. The College recommends the devices be “used continuously until ambulation and discontinued only at the time of hospital discharge” but the same practice bulletin suggests the devices “be continued until the patient is fully ambulatory.”6 The first recommendation says the patient should wear the device at all times when not ambulating, whereas the second implies the patient need wear the device only until she is able to ambulate. Whether a patient is “fully ambulatory” is vague because being able to ambulate does not imply she is actually ambulating. The hours per day patients must wear the devices to receive the maximum thromboprophylaxis benefit are also not known and not addressed in the guidelines.
Our study used limited scope education strategies to maximize ease of implementation. More elaborate strategies could be more effective and might include preoperative patient education, nurse education with pre- and posttests, conducting the patient education later after surgery when less affected by the anesthetic, educating family members, or increasing staffing.
The observed compliance rates appear low given the morbidity and mortality caused by postoperative venous thromboembolism. No deep vein thromboses occurred during the study period, so recommendations about the adequacy of the observed compliance cannot be made. Because patient and nursing education did not improve sequential compression device compliance, it is unlikely that other similar easy-to-implement interventions will overcome noncompliance. In instances in which guidelines allow use of compression devices or pharmacologic prophylaxis, health care providers need to balance concerns regarding bleeding with concerns of possible limitations in effectiveness related to compliance. For patients of particular concern, the compliance issues may make pharmacologic prophylaxis preferable.
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© 2015 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.
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