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SN Comprehensive Clinical Medicine

, Volume 1, Issue 1, pp 26–29 | Cite as

An Analysis of the Efficacy of Continuous Bupivacaine Infusion Pump (On-Q® Pump) in Bariatric Surgery Patients

  • Nathalie Quach
  • Shiyi Geng
  • Y-Nha P. Nguyen
Medicine
  • 237 Downloads
Part of the following topical collections:
  1. Topical Collection on Medicine

Abstract

With an increasing obese population nationwide, there has been an increase in the number of laparoscopic surgeries performed. However, few studies have evaluated different methods to reduce pain in bariatric patients after laparoscopic surgery. Bupivacaine infusion pumps (On-Q® pumps) have shown efficacy in reducing postoperative pain in other surgical populations, such as orthopedic patients. Therefore, the purpose of this study was to investigate whether infusion pain pumps improve postoperative pain control and decrease length of hospital stay in bariatric patients. Between January 2015 and August 2016, 125 charts were retrospectively reviewed. Patients were divided into two groups: those who received infusion pain pumps and those who did not. The primary endpoints were hospital length of stay and the amount of postoperative narcotic use. Secondary endpoints included postoperative pain score, use of non-narcotics, and complications due to opioids or bupivacaine. There were 82 patients in the infusion pain pump group and 43 patients in the control group. Baseline characteristics were similar between both groups. There were no statistically significant differences in length of hospital stay (p = 0.39) or postoperative opioid use (p = 0.48) between the two groups. Although the median postoperative pain score was significantly reduced in the infusion pain pump group (3.5) compared to the control group (5) for the first 48 h (p = 0.002), this difference was not statistically significant for the first 24 h (p = 0.06). The use of infusion pain pumps did not significantly reduce the length of hospitalization and use of narcotics postoperatively.

Keywords

Bariatric surgery Bupivacaine Laparoscopic surgery Morbid obesity On-Q pump Postoperative pain 

Introduction

With an increasing obese population nationwide, there has been an increase in the number of laparoscopic surgeries performed. However, there have been few studies evaluating different methods of reducing postoperative pain and even fewer studies investigating different methods to reduce pain in bariatric patients after laparoscopic surgery. Bupivacaine infusion pumps have been shown to be effective in reducing postoperative pain in other surgical populations including orthopedic and arthroscopic patients [1]. Current published data revealed mixed results on the efficacy of continuous bupivacaine infusions in gastric bypass patients [2, 3, 4, 5, 6, 7]. Furthermore, bariatric patients are often accompanied by multiple co-morbidities, and so it is desirable to strive to minimize the morbidity associated with current procedures, such as reducing the incidence of respiratory failure from the overuse of opioids by using an alternative method that offers the same level of pain control as opioids but without their associated toxicities.

Therefore, the purpose of this project is to investigate whether the use of bupivacaine infusion pumps improves postoperative pain control and decreases length of hospital stay. The presumed benefit of infusion pain pump is reduced postoperative pain, which would enable earlier mobilization of bariatric patients, facilitate faster return to baseline activity, and decrease the risks of deep venous thrombosis [3]. Additionally, reducing the use of opioids in bariatric patients could potentially reduce the incidence of opioid-associated respiratory depression, especially when this patient population is already at high risk for obesity hypoventilation syndrome, chronic obstructive pulmonary disease, and obstructive sleep apnea [7].

Methods

Approval for this study was outsourced to the MetroWest Medical Center Institutional Review Board. Due to the retrospective nature of this study, no active intervention was performed and no altercation to therapy was anticipated to the subjects included in the study. Therefore, the board waived informed consent.

A retrospective electronic chart review was conducted on patients age 18 and above who underwent bariatric surgery from January 2015 to August 2016 at our institution. Exclusion criteria consisted of patients who received a prescription for opioids within 30 days prior to bariatric surgery, patients with incomplete information on their electronic medical charts, and patients deceased within the first 24 h after hospitalization. Of the 143 patients screened, 125 patients were included in the study (Fig. 1). Patients were then divided into those who received infusion pain pumps postoperatively and those who did not. The infusion pain pump used at our institution was the On-Q® pump device (Kimberly-Clark, Roswell, GA) filled with 0.2% bupivacaine solution and administered at a flow rate between 4 to 14 ml per hour. Patients in both groups received standard-of-care postoperative pain management, which included as needed intravenous and oral opioids and scheduled intravenous ketorolac. All surgeries were performed by a single bariatric surgeon.
Fig. 1

Patient flow chart

Demographic data, including age, gender, body mass index (BMI), comorbidities, and operative data, were collected. Primary endpoints were hospital length of stay and amount of postoperative opioids use. Secondary endpoints included postoperative pain score, inpatient daily use of non-narcotic pain medications, complications due to opioids (i.e., respiratory depression requiring naloxone use), and complications due to bupivacaine (i.e., bradycardia, cardiac arrest, heart block, ventricular arrhythmia). Postoperative pain scores were patient reported and documented by nursing staff on a scale from 0 to 10, with 0 being no pain and 10 the worst pain experienced. All postoperative opioid medications were converted to oral morphine equivalent dose for comparison. Opioid use, postoperative pain scores, and complications that may be attributed to study medications were collected and calculated in 24-h intervals for a total of 48-h post-bariatric surgery.

Duration of hospitalization was used to determine target sample size. We calculated a priori that 35 patients per group would be required to reach a power of 80% to detect a difference of 12 h between the two groups—a clinically significant result. Statistical analysis was performed using SigmaStat 3.5 with p < 0.05 considered statistically significant. The two treatment groups were compared using Student’s t test or Mann-Whitney rank sum for ordinal data, and chi-square test for nominal data.

Results

A total of 143 patient charts were identified during the study period, and 125 patients met study criteria. Eighty-two patients received infusion pain pumps and 43 did not. All demographics information between the two groups were comparable with no significant differences identified (Table 1). Average age of the bariatric patients was 46.4 years old in the infusion pain pump group and 45.7 years old in the control group. Both groups had a majority of female patients.
Table 1

Demographic data

Baseline characteristics

Infusion pain pump (n = 82)

Control (n = 43)

p value

Mean age (years)

46.4

45.7

0.71

Male (%)

28

19

0.35

Median BMI (kg/m2)

44.6

41.7

0.14

Comorbidities (%)

 Diabetes

43

63

0.05

 Hypertension

68

60

0.50

 Obstructive sleep apnea

34

16

0.06

 Hyperlipidemia

28

35

0.56

 Asthma

7

9

0.97

 Osteoarthritis

21

14

0.49

 Depression

20

21

0.96

Median operative time (minutes)

104.5

127

0.21

The median hospital length of stay for the infusion pain pump group was 37 h compared to 38 h for the control group (p = 0.391). The median postoperative opioid use in the infusion pain pump group was 25 mg of oral morphine equivalent compared to 37 mg in the control group in 24 h cumulative and 48 h cumulative after surgery. Although postoperative use of opioids in the infusion pain pump group was reduced, this difference failed to achieve statistical significance (Table 2).
Table 2

Primary outcomes

Outcomes

Infusion pain pump (n = 82)

Control (n = 43)

p value

Hospital length of stay (hours)

37

38

0.39

Postoperative opioid use (%)

82

88

0.48

Postoperative opioid use (morphine PO equivalent in mg)—within first 24 h

25

37

0.16

Postoperative opioid use (morphine PO equivalent in mg)—within first 48 h

25

37

0.10

None of the patients reviewed required naloxone for respiratory depression resulting from opioid use. Reported pain scores were similar between both groups in the first 24 h postoperatively (Table 3). However, statistical significance was detected in pain scores during the cumulative 48 h post-bariatric surgery (median 3.5 in the infusion pain pump group vs. 5 in the control group; p = 0.02). Interestingly, a greater percentage of patients in the infusion pain pump group had a documented heart rate of less than 60 beats per minute; however, none required intervention.
Table 3

Secondary outcomes

Outcomes

Infusion pain pump (n = 82)

Control (n = 43)

p value

First 24 h

 Median postoperative pain score (scale of 0–10)

4

5

0.06

 Respiratory depression requiring naloxone (%)

0

0

 Asymptomatic bradycardia (%)

22

5

*0.02

First 48 h

 Median postoperative pain score (scale of 0–10)

3.5

5

*0.002

 Respiratory depression requiring naloxone (%)

0

0

 Asymptomatic bradycardia (%)

27

5

*0.006

*p value < 0.05 indicates statistical significance

Discussion

We were not able to demonstrate statistical differences in both the amount of postoperative opioid use and the length of hospital stay between bariatric surgery patients who received infusion pain pumps and those who did not. However, patients who received the infusion pain pumps reported lower postoperative pain scores in the cumulative 48 h postoperative time period. Whether this reduction is clinically significant may be open for discussion and further investigation. None of the patients in our study required naloxone for respiratory depression resulting from opioid use. Bradycardia, defined as a heart rate less than 60 beats per minute, was documented more frequently in patients who received the infusion pain pumps, but none of the patients required intervention. Although this study was not designed as a cost-effective analysis, the extra cost difference in using an infusion pain pump should be considered relative to its impact on length of stay, postoperative opioid use, and medication-related side effect management.

This study was limited by the nature of a retrospective design. There were more patients in the infusion pain pump group than in the control group. The routine use of infusion pain pumps (On-Q® pumps) at our institution was stopped during our study period. Most patients who underwent bariatric surgery prior to the stop date received On-Q® pumps, whereas all bariatric patients after the stop date did not receive On-Q® pumps. Also, there were possible inconsistencies in frequency of pain assessment and documentation of admission and discharge times. Lastly, we were not able to assess baseline vital signs, infection rate, or other potential medication-related side effects, such as constipation or level of sedation, from our electronic health records.

Conclusion

This retrospective study was not able to demonstrate statistical differences in neither postoperative opioid requirements nor hospital length of stay between patients who received bupivacaine continuous infusion via a pain pump system and those who did not. Patients who received infusion pain pumps showed a reduction in self-reported pain scores in a cumulative 48 h post-surgery; however, larger prospective trials would be needed to further assess the clinical application of this difference and also other benefits of utilization of a continuous infusion pain pump device for the management of postoperative pain in bariatric patients.

Notes

Acknowledgements

We would like to thank Dr. Carlos A. Barba, Marcela Montemayor, and the bariatric team for their dedication in providing excellent patient care. A special thanks also to Mary Dobbs for her assistance in screening possible electronic records for our study and technological support.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Due to the retrospective nature of the study, informed consent was waived by the board.

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Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.Valley Baptist Medical Center, Department of PharmacyBrownsvilleUSA

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