Don't Fear the Bleed: Assessing Postoperative Bleeding Incidence After Instituting a Standardized Prophylactic Heparin Protocol in Bariatric Patients

Abstract

Background:

Bariatric surgery is a frequently performed procedure in the United States, accounting for ∼40,000 procedures annually. Patients undergoing bariatric surgery are at high risk for postoperative thrombosis, with a venous thromboembolism (VTE) rate of up to 6.4%. Despite this risk, there is a lack of guidelines recommending postoperative VTE prophylaxis and it is not routine practice at most hospitals. The postoperative bleeding rate after bariatric surgery is only 1.5%; however, the risk of bleeding may lead to hesitancy for more liberal VTE prophylaxis.

Methods:

This is a retrospective analysis of bariatric surgeries at a single institution in 2019 and 2021. Data were obtained from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) and electronic medical record review for all patients undergoing sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or conversion to RYGB. The primary outcomes were composite bleeding events, which included postoperative transfusion, postoperative endoscopy or return to operating room (OR) (for bleeding), intra-abdominal hematoma, gastrointestinal (GI) bleeding, or incisional hematoma.

Results:

There were a total of 2067 patients in the cohort, with 1043 surgeries in 2019 and 1024 surgeries in 2021. There was no difference between bleeding events after instituting a deep venous thrombosis (DVT) prophylaxis protocol in 2021 (27 versus 28 events, P = .76). There was no difference in individual bleeding events between 2019 and 2021. Additionally, there was no significant difference in the rate of VTE between 2019 and 2021 (2 versus 5 events, P = .28).

Conclusions:

After instituting a standard protocol of prophylactic heparin postdischarge, we did not find an increased rate of bleeding events in patients undergoing bariatric surgery. Thus, surgeons can consider prescribing postdischarge chemical VTE prophylaxis without concern for bleeding.

Introduction

Bariatric surgery is relatively common in the United States, with over 260,000 surgeries performed in 2021.¹ The two most popular types of bariatric surgeries are sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB), both of which continue to grow in popularity.^1,2 While these operations can yield excellent results in terms of weight loss and improvement in metabolic health, they also present a unique set of operative and perioperative challenges.

The bariatric patient population is at particular risk for perioperative venous thromboembolism (VTE) given their elevated body–mass index (BMI), underlying comorbidities, and high-risk abdominal surgery.^3–5 The incidence of postoperative VTE in the bariatric surgery population is ∼1%–3%.^6–8 Although rare, postoperative deep venous thrombosis (DVT) or pulmonary embolism (PE) is a concerning source of mortality in this population, with a mortality risk of 0.06%–0.88% and average mortality of 0.18%.^6,9

Conversely, bariatric patients are also at risk of postoperative bleeding in both SG and RYGB. In fact, postoperative bleeding events occur in ∼1.5%–3% of all bariatric surgery cases.¹⁰ With the risk of bleeding from the staple line in SG and the anastomoses in RYGB, the surgeon must weigh the risk of bleeding against the risk of VTE. Given this delicate balance between preventing both postoperative bleeding and VTE, no guidelines exist regarding administration of postoperative chemical VTE prophylaxis.¹¹

Several methods have been used to estimate the risk of postoperative VTE in bariatric populations. Traditionally, the risk of VTE is calculated with the Caprini score based on age, BMI, type of surgery, and medical comorbidities.³ However, this calculator may not be completely generalizable to the bariatric population, which led Aminian et al. to develop a risk calculator specifically for bariatric surgery patients. They found that the highest risk of VTE was in patients with congestive heart failure (CHF), dyspnea at rest, and paraplegia.⁷

Although the benefits of long-term DVT prophylaxis in high-risk surgical patients are well established, it must be balanced with the risk of hemorrhage. For instance, more than 2 weeks of chemical DVT prophylaxis can significantly reduce the incidence of DVT, but this comes with a postoperative bleeding incidence of ∼1%.¹² In fact, for SG, a study demonstrated a slightly increased rate of postoperative bleeding at 0.68% without staple line reinforcement.¹³ Thus, the majority of patients undergoing bariatric surgery have an inherent risk of a bleeding event without DVT prophylaxis.

Another complicating variable is the fact that outcomes for different types of DVT prophylaxes are variable within the literature. The lowest bleeding rates are associated with enoxaparin compared with fondaparinux.¹⁴ However, additional variability in bleeding rates is observed when using different types of heparin derivates for prophylaxis. Enoxaparin use alone is associated with less postoperative transfusion requirement compared with mixed use of enoxaparin and unfractionated heparin regimens. Furthermore, some surgeons have used low-dose, novel oral anticoagulants (NOACs) as DVT prophylaxis.

While a wide variety of NOACs have been used for VTE prophylaxis, there is no difference in efficacy, but apixaban has the best bleeding safety profile.¹⁵ Given the wide availability of agents for VTE prophylaxis, there are no guidelines to suggest a single or mixed regimen, and this selection is often based on surgeon preference.

Conversely, these studies suggest that careful selection of DVT prophylaxis is also essential in reducing bleeding risk.¹¹ However, data remain mixed as some studies have shown increased risk of bleeding with the use of postoperative chemical DVT prophylaxis.^16,17 However, many of the studies on DVT prophylaxis in bariatric patients, which analyze a mix of anticoagulation regimens, have no consensus.

The primary objective of this study was to examine the effects a new, standardized, postdischarge DVT prophylaxis protocol that uses enoxaparin in a bariatric population. We sought to evaluate the incidence of both major and minor postoperative bleeding related to a more aggressive approach to DVT prophylaxis.

Methods

Study design

This was a descriptive retrospective study of all patients undergoing primary SG, primary RYGB, or conversion of SG to RYGB at a single, tertiary academic center from 2019 and 2021. Cases from 2020 were excluded due to significant decrease in case volume during the COVID-19 pandemic and possible confounding factors related to COVID-19 and clotting. Cases were identified through the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database, which was also used to obtain patient outcome data; additional data were obtained based on chart review.

This study was approved by our institutional ethics review board. No funding was received for this study. For this type of study, formal consent was not required. Thus, informed consent does not apply.

This study compared outcomes in the above patient population after instituting a standardized, postdischarge chemical DVT prophylaxis protocol. The protocol was instituted in January 2021 and stated that all patients undergoing primary or revisional bariatric surgery should receive 40 mg of enoxaparin, subcutaneously, twice daily for 14 days upon discharge, unless the patient had an absolute contraindication to anticoagulation (including active gastrointestinal [GI] bleed, known coagulopathy, or allergy). All patients received 5000 units of unfractionated heparin preoperatively and then the same dose of unfractionated heparin every 8 hours postoperatively while admitted.

This protocol was applied for all patients regardless of BMI and other comorbidities. Risk calculators were not used to further tailor individual regimens. This protocol was not applied to patients who were on therapeutic anticoagulation preoperatively. Before instituting this protocol, postdischarge DVT prophylaxis was left to the surgeon's discretion. At our institution, the individual surgeon protocol was variable and based on different risk calculators, including the Cleveland Clinic risk calculator, Caprini score, or clinical judgment.

The inclusion criteria for this study included all patients over the age of 18 undergoing SG, RYGB, or conversion of SG to RYGB. Exclusion criteria included the use of therapeutic anticoagulation or patients requiring greater than 14 days of prophylactic anticoagulation due other thrombotic risk.

Data collection

Data were collected in four areas, including patient demographics, preoperative data, intraoperative data, and postoperative outcomes. Patient demographics included age, sex, and BMI. Preoperative data included the American Society of Anesthesiologists (ASA) class and diabetes mellitus (DM), hypertension (HTN), hyperlipidemia (HLD), chronic kidney disease (CKD), chronic obstructive pulmonary disorder (COPD), prior pulmonary embolism (PE), prior DVT, gastrointestinal reflux disease (GERD), obstructive sleep apnea (OSA), and prior myocardial infarction (MI) rates.

Intraoperative data included the type of surgery, including whether it is primary or conversion, and the presence of sleeve staple line reinforcement (reinforced stapling versus oversewing). Postoperative outcomes included postoperative transfusion, postoperative endoscopy, return to operating room (OR) for bleeding, GI bleed, intra-abdominal hematoma, incisional hematoma, DVT, and mortality. All postoperative outcomes were examined 30 days postoperatively. We considered any event requiring procedural intervention (endoscopy or return to OR) as a major bleeding event; all other events were considered minor bleeding events.

The primary outcome was composite bleeding events. The secondary outcomes related to bleeding, which included incisional hematoma, GI bleeding, intra-abdominal hematoma, postoperative transfusion, postoperative endoscopy, and postoperative return to OR for bleeding. We also examined DVT rates and 30-day mortality as secondary outcomes. We also examined the total bleeding events in SG based on the type of gastric staple line reinforcement.

Statistical analysis

Categorical variables are displayed as counts with percentiles. Continuous variables whose distributions approximated normality are reported as mean with standard deviation; otherwise, medians and ranges were used. Chi-square and Fischer's exact tests were used to compare categorical variables. t-Test and Wilcoxon rank sum tests were used to compare continuous variables. Data were analyzed using SAS, v9.4 (SAS Institute, Cary, NC).

Results

There were noted differences in patient demographics and comorbidities between the 2019 and 2021 cohorts. While the BMI of each group was not significantly different (44.6 ± 8.0 versus 44.6 ± 7.7, P = .91), the 2021 group was younger (38.5 ± 11.7 versus 41.6 ± 12.3, P < .001). There were also differences in the presence of bariatric comorbidities between the two groups. In the 2021 group, there was a lower proportion of patients with HTN (58% versus 42%), HLD (56% versus 44%), GERD (57% versus 43%), and DM (61% versus 39%).

However, there was no difference in prior cardiac comorbidities, including MI (3 versus 7, P = .22) or percutaneous corony intervention/cardiac stent (4 versus 4, P = 1.0). More patients in the 2021 group had a history of DVT (13 versus 2, P = .004). The majority of patients were either ASA class 2 or class 3. There were more ASA class 3 and fewer class 2 patients in 2021 compared with 2019 (Table 1).

Table 1.

Patient Characteristics

	2019, n (%), N = 1123	2021, n (%), N = 1213	P
Age, years	41.6 (±12.3)	38.5 (±11.7)	<.001
Female	872 (49.9)	877 (50.1)	.27
BMI	44.6 (±8.0)	44.6 (±7.7)	.91
ASA class
1	1 (100)	0 (0)
2	237 (58.1)	171 (41.9)
3	795 (48.3)	850 (51.7)
4	6 (66.7)	3 (33.3)
CKD	2 (66.7)	1 (33.3)	1.00
COPD	11 (57.9)	8 (42.1)	.51
Diabetes mellitus	279 (61)	178 (39)	<.001
GERD	293 (57.1)	220 (42.9)	.004
HLD	202 (56.4)	156 (43.6)	.01
HTN	439 (58.1)	317 (41.9)	<.001
MI	3 (30)	7 (70)	.22
OSA	309 (51.4)	292 (48.6)	.54
PCI/stent	4 (50)	4 (50)	1.0
PE	2 (20)	8 (80)	.06
DVT	2 (13.3)	13 (86.7)	.004

ASA, American Society of Anesthesiologists; BMI, body–mass index; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disorder; DVT, deep venous thrombosis; GERD, gastrointestinal reflux disease; HLD, hyperlipidemia; HTN, hypertension; MI, myocardial infarction; OSA, obstructive sleep apnea; PCI, percutaneous coronary intervention; PE, pulmonary embolism.

During the 2 years that data were analyzed, a total of 2336 cases were performed. In 2019, there were a total of 1123 cases, including 685 SG, 354 RYGB, and 84 conversion cases. In 2021, there were a total of 1213 cases, including 675 SG, 349 RYGB, and 189 conversion cases (Table 2).

Table 2.

Type of Procedure by Year

	2019, n (%), N = 1123	2021, n (%), N = 1213	P
Sleeve	685 (50.4)	675 (49.6)	.99
Bypass	354 (50.4)	349 (49.6)
Conversion	84 (30.8)	189 (69.2)	<.001

After instituting the postdischarge DVT prophylaxis protocol in 2021, there were a total of 28 (2.6%) bleeding events compared with 27 (2.7%) bleeding events in 2019 (P = .84). There was no statistical difference in DVT rates between 2019 and 2021 (0.19% versus 0.49%, P = .28). Additionally, no statistical difference was detected in any of the individual bleeding events between 2019 and 2021.

After institution of the postdischarge heparin protocol, there were fewer major bleeding events, but this difference was not statistically significant. In 2021, there was 1 bleeding event (0.1%) requiring endoscopy compared with 2 events (0.19%) in 2019 (P = 1.0); in addition, in 2021, only 1 case (0.1%) required reoperation for bleeding, whereas 3 cases (0.29%) required reoperation in 2019 (P = .62) (Table 3). There was no 30-day postoperative mortality in either year.

Table 3.

Comparison of Postoperative Bleeding Events and Deep Venous Thrombosis Rates for All Sleeve Gastrectomy, Roux-en-Y Gastric Bypass, and Conversion of Sleeve to Roux-en-Y Gastric Bypass Cases

	2019	2021	P
	n (%), N = 1123	n (%), N = 1213
Composite bleeding events	27 (2.6)	28 (2.7)	.84
Incisional hematoma	17 (1.6)	13 (1.27)	.49
Postop transfusion	3 (0.29)	4 (0.39)	.72
Postop GI bleed	7 (0.67)	9 (0.88)	.62
Intra-abdominal hematoma	5 (8.3)	5 (5.3)	.51
Endoscopy for bleeding	2 (0.19)	1 (0.1)	1.0
Bleeding requiring OR	3 (0.29)	1 (0.1)	.62
Postop DVT	2 (0.19)	5 (0.49)	.28

The protocol of 14 days of prophylactic enoxaparin (40 mg twice daily) was instituted in 2021.

DVT, deep venous thrombosis; GI, gastrointestinal; OR, operating room.

A separate analysis of all bleeding events was performed to examine the rate of individual patients with multiple postoperative bleeding events. In 2019, there were 20 patients who had a single postoperative bleeding event compared with 24 patients in 2021. However, 7 patients had multiple (≥2) bleeding events in 2019 compared with just 4 patients in 2021 (P = .75, Table 4).

Table 4.

Incidence of Bleeding Events (Single or Multiple) in Patients Undergoing Primary or Conversion Bariatric Surgery

	2019	2021	P
	n (%)	n (%)
1 Event	20 (45.5)	24 (54.5)
≥2 Events	7 (62.5)	4 (37.5)	.75

Finally, we examined, for each year, bleeding in patients undergoing SG based on the staple line reinforcement technique. We compared the composite bleeding events between buttressed staple lines and oversewn staple lines before and after institution of the postdischarge DVT prophylaxis protocol. In 2019, there were 2 bleeding events for buttressed staple lines and 3 events for oversewn staple lines (P = .68). In 2021, there were 3 events for buttressed staple lines and 2 events for oversewn staple lines (P = 1.0) (Table 5).

Table 5.

Total Bleeding Events for Sleeve Gastrectomy Based on Sleeve Gastrectomy Reinforcement, by Year

	2019			2021
	Reinforced, n (%)	Oversewn, n (%)	P	Reinforced, n (%)	Oversewn, n (%)	P
n	338 (50.6)	346 (49.4)		447 (66.2)	228 (33.8)
Total bleeding	2 (0.58)	3 (0.89)	.68	3 (0.67)	2 (0.88)	1.0

Discussion

Perioperative VTE prophylaxis in bariatric surgery poses a difficult clinical challenge as DVT and PE can be lethal in these high-risk patients⁶; however, these same patients are also at an elevated risk of bleeding.¹⁸ This study found no statistically significant difference in 30-day postoperative bleeding events with more liberal use of postdischarge DVT prophylaxis. This study found a nearly identical number of total postoperative bleeding events after instituting a discharge protocol of prophylactic enoxaparin. Additionally, we found no statistically significant change in postoperative DVT rates after instituting this protocol.

However, this study was not powered to detect a difference in the DVT rate and this was not the object of the study. Thus, we decided not to further analyze this lack of statistical difference. Despite no reduction in the DVT rate, there is no evidence of increased bleeding risk with postdischarge chemical DVT prophylaxis. In fact, after instituting this protocol, a slightly lower number of bleeding events required procedural intervention, despite the lack of statistical significance.

Furthermore, the magnitude of bleeding events also decreased as there were fewer patients in the postprotocol group who had multiple bleeding events. Therefore, our data suggest that postdischarge enoxaparin can be safely administered without an increase in the rate of bleeding.

There was a slight clinical increase in the DVT rate in 2021 (0.49% versus 0.19%, P = .28) after instituting the postdischarge enoxaparin protocol, although the difference was not statistically significant. This rate was still below the reported DVT incidence of 1%–3%.^6–8,16 This slight increase in rate may be attributed to a slightly more comorbid population in the 2021 cohort as more patients were classified as ASA 3 compared with the 2019 cohort.

Additionally, significantly more patients in the 2021 group had a history of DVT or PE, increasing their risk for postoperative thrombosis. Finally, patients may have been at slightly higher risk of DVT or PE in 2021 as the COVID-19 pandemic had not yet concluded and the incidence of COVID-19 remained elevated in our patient population; prior exposure or infection was not tracked in this study, but it may have increased individual risk of thrombosis.¹⁹

Despite a lack of association of postoperative bleeding with postdischarge DVT prophylaxis, major bariatric surgeries lack guidelines on the use of outpatient chemical DVT prophylaxis.^11,20 However, the use of routine postoperative VTE prophylaxis remains a common practice among bariatric surgeons as the outcomes of postoperative VTE can be devastating.⁶ The results of this study can provide reassurance that the use of postoperative VTE prophylaxis will not increase the risk of postoperative bleeding events in a high-risk population.

A prior study performed by Fennern et al. found an increased risk of bleeding with the use of postdischarge low-molecular-weight heparin without a significant change in incidence of DVT.¹⁷ This study found a 2.47% bleeding event rate in the postdischarge heparin group, compared with a 1.8% bleeding rate in those discharged without DVT prophylaxis. Our study showed similar bleeding event rates in 2019 (2.6%) and 2021 (2.7%) as in the DVT prophylaxis group in the Fennern et al. study. While all of these rates remain higher compared with no postdischarge DVT prophylaxis, they remain below the estimated average risk.

The majority of patients in our study underwent SG, and Janik et al. found an estimated bleeding risk of 4% for SG²¹; however, we found an overall bleeding rate of 2.7% when increasing postdischarge DVT prophylaxis use. Even when comparing the risk of SG alone with the reported risk in the literature, a notably lower rate of bleeding (5 patients/0.7%) with SG was observed in the postprotocol group that had bleeding events. This suggests that with any type of staple line reinforcement, there is no added risk of bleeding with postdischarge enoxaparin use.

In a study performed by Altieri et al., they examined the rate of DVT and postoperative bleeding events after bariatric surgery. They found an overall lower DVT rate with any type of chemical DVT prophylaxis compared with no prophylaxis; however, a mix of unfractionated heparin and enoxaparin preoperatively and postoperatively was associated with a slightly increased risk of postoperative transfusion. This study found a 2.48% transfusion rate for all comers.¹¹ Comparatively, both groups in our study had a transfusion rate below 0.4%.

This difference may be explained by the fact that the majority of patients studied by Altieri et al. underwent RYGB, whereas most of the patients in our study underwent SG. The benefit of DVT prophylaxis is clear, but the results of our study suggest that there should be no concern for the increased rate of bleeding with routine use of a heparin-based regimen of DVT prophylaxis. Therefore, a similar mixed regimen of preoperative unfractionated heparin and postoperative enoxaparin may be considered safe.

This study also found no increased rate of bleeding in SG based on staple line reinforcement (buttressed versus oversewn). Our results are comparable with those of Golzarand et al. who found that oversewing the gastrectomy staple line decreased the risk of bleeding, compared with no reinforcement, where we found a low rate of bleeding with oversewing as well.²² However, our findings are consistent with other studies undertaking a similar analysis.

In fact, our results parallel the findings of Zafar et al. who found that any type of staple line reinforcement (buttressing versus oversewing) decreased the risk of postoperative bleeding and there is no difference in bleeding rates between buttressed staple lines and oversewing.¹³ Our results build on the results of this study as they did not analyze their patient sample in the setting of postdischarge DVT prophylaxis. Staple line reinforcement is a well-described method to reduce bleeding risk, and our study suggests that there is no additional risk of bleeding with the use of postdischarge heparin when including staple line reinforcement.^13,23

Evidence for the use of aggressive postdischarge DVT prophylaxis remains controversial as several studies have shown some associated risk of bleeding. However, this study shows no increased rates of bleeding with routine administration of postdischarge enoxaparin.

We recognize that there are several limitations to this study. This is a single-center retrospective study, with a relatively small number of cases compared with prior data. This study may have been underpowered to detect a difference in bleeding events or rates of DVT. There may have also been missed bleeding events as patients may have presented to another hospital. There is also a possible confounding factor as the COVID-19 pandemic was in effect for one of the two arms of the study.

There may have also been a Hawthorne effect after institution of the protocol as surgeons may have been more meticulous about hemostasis given the more aggressive administration of enoxaparin.

For future directions, this same patient population may be continued to be followed to also study the effect of the protocol on high-risk patients for both bleeding and thrombosis. We may also compare our protocol with other centers that use a similar protocol with a different discharge medication such as an NOAC.

Conclusions

Patients undergoing bariatric surgery are at increased risk of VTE, but there are no society guidelines regarding the use of postdischarge DVT prophylaxis. This article shows that the routine use of chemical VTE prophylaxis on discharge does not increase any bleeding events. There were no statistically significant differences in bleeding events after utilizing a standardized prophylactic heparin protocol at our institution.

Thus, surgeons who are considering the use of postdischarge VTE prophylaxis should not be deterred by concern for additional bleeding risk.

Footnotes

Acknowledgments

This article was also presented at IFSO World Congress 2023 (Naples, Italy) and its abstract was published in Obesity Surgery in July 2023 ().

Authors' Contributions

Study design was done by D.C. and R.C. Data collection and analysis were performed by X.P. and P.F. Article preparation and editing were performed by R.B., D.T., and R.C.

Disclosure Statement

None of the authors have financial relationships with industry or conflicts of interest to disclose.

Funding Information

No funding was received for this study.

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