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Evaluation of continuous infusion of 0.5% bupivacaine by elastomeric pump for postoperative pain management after open inguinal hernia repair
Evaluation of Continuous Infusion of 0.5% Bupivacaine by Elastomeric Pump for Postoperative Pain Management after Open Inguinal Hernia Repair Karl A LeBlanc, MD, MBA, FACS, Drake Bellanger, MD, FACS, V Keith Rhynes, MD, FACS, Mark Hausmann, MD, FACS Postoperative pain management and narcotic usage after inguinal hernia repair is an important concern for anesthesiologists and surgeons. Regional anesthesia incisional infiltration techniques may reduce the need for systemic medications. STUDY DESIGN: Double-blind study of 52 patients undergoing open hernia repair with the Prolene Hernia System prospectively randomized to receive either 0.5% bupivacaine or saline continuously for ˜ Q Pain 48 hours at 2 mL/hour through use of an elastomeric continuous infusion pump (ON Relief System). Outcomes measured over the 120 hours postoperatively were: narcotic use, Visual Analogue Scale pain scores, site inflammation (visual inspection), and side effects. Comparisons between the groups were made by applying the Mann-Whitney rank sum test and analysis of variance with treatment as a fixed effect in the model. RESULTS: In the bupivacaine group, 24% (versus 4% in the placebo group) required no narcotics (p ⬍ 0.05). Daily and total narcotic usages for all 5 study days were significantly less (p ⬍ 0.05) in the bupivacaine group. There were no reports of complications at the catheter-insertion site or surgical-wound site. CONCLUSIONS: Demonstrable benefits include reduction of narcotic usage and pain with no apparent increase in the risk of infection or complication. Continuous infusion of 0.5% bupivacaine at 2 mL/h ˜ Q pump is a safe and effective adjunct in postoperative pain management for through the ON open inguinal hernia repair. This represents a viable and possibly superior option for prolonged pain management, minimizing use of narcotics in patients undergoing this procedure. (J Am Coll Surg 2005;200:198–202. © 2005 by the American College of Surgeons) BACKGROUND:
and is associated with increased morbidity and mortality when compared with the outpatient setting. In response to the increased interest in hastening the time to discharge, efforts to develop anesthetic agents with more favorable recovery profiles and minimization of immediate postoperative symptoms (pain, nausea, emesis, dizziness, fatigue, and headache) have also increased. Of these immediate postoperative symptoms, management of postoperative pain remains a major issue in the acceptance of early discharge by patients and an important concern for anesthesiologists and surgeons. Incidence of moderate-to-severe postdischarge pain is approximately 40% to 70% in the outpatient setting.3 Despite major advances in surgical techniques, which have minimized surgical trauma and the interrelated postoperative incisional pain, postdischarge pain remains the most common reason for readmission to the hospital after outpatient operation.4 Mean incidence of
The first ambulatory inguinal hernia operation was reported in 1967.1 Since that time, the percentage of these operations performed in the ambulatory setting has grown to about 60%. In the United States, nearly 60% of all operations are performed in the ambulatory setting. In the United Kingdom, 68% of all operations are reported to be performed as day operations, with the goal of moving 75% of all elective operations to the ambulatory setting.2 The longer postoperative care needed for subjects admitted to the hospital is expensive
K LeBlanc owns options in I-Flow and is a member of the Ethicon Advisory Board. Supported by a grant from Ethicon Endo-Surgery and I-Flow Corporation. Received March 18, 2004; Revised October 8, 2004; Accepted October 19, 2004. From Surgical Specialty Group Inc, Baton Rouge, LA. Correspondence address: Karl A LeBlanc, MD, MBA, FACS, Surgical Specialty Group Inc, 7777 Hennessy Blvd, Ste 612, Baton Rouge, LA 70808.
© 2005 by the American College of Surgeons Published by Elsevier Inc.
198
ISSN 1072-7515/05/$30.00 doi:10.1016/j.jamcollsurg.2004.10.011
Vol. 200, No. 2, February 2005
LeBlanc et al
readmission because of pain is reported as 45%, reaching as high as 95% for certain gynecologic and orthopaedic procedures.5,6 It is clear that new ways to provide adequate pain relief in the outpatient setting while maintaining subject safety and comfort need to be developed. As an added benefit, patient satisfaction is increased with control of postoperative pain, promoting quicker recovery. The most common treatment for pain after operation is opioid analgesic drug administration, although opioids are associated with unwanted side effects, such as respiratory problems, nausea and vomiting, itching, increased duration of postoperative ileus, and others. These side effects can be decreased with a reduction in the amount of opioid drugs administered. Because a reduction of the daily consumption of narcotics is often associated with a decrease in analgesia, many other treatments for postoperative pain have been evaluated. One of the most effective is epidural analgesia, but the epidural catheter needs to be placed preoperatively, is a fairly invasive method, is not well suited for outpatient use, and maintenance of the epidural treatment can be time consuming and expensive. In the last few years, a new method of delivering continuous wound infiltration with a solution of local anesthetic through an indwelling irrigation apparatus has been used in an increasing percentage of ambulatory surgery patients. This method, which was described by Capelle5 and later by Blades and Ford6 for thoracotomy incisions, uses a fine catheter inserted into the wound before surgical closure. Because of the relatively limited experience with this type of analgesia, we sought to evaluate its use in management of postsurgical pain after open inguinal hernioplasty. This is one of the most commonly performed general surgical procedures in the world. If this was shown to be effective with this outpatient operation, expansion of the use of this methodology for other operative procedures, such as incisional hernia repair or laparotomy, could be recommended. METHODS After Institutional Board Review approval, written informed consent was obtained from 52 unilateral inguinal hernia patients undergoing primary open hernia repair with the Prolene Hernia System (Ethicon, Inc). Patients included in the study were those with an incision length ⬍ 20 cm, age older than 18 years, and able to
Pain Management after Inguinal Hernia Repair
199
give informed consent. Exclusion criteria included allergy to bupivacaine, significant liver or renal disease, candidates for outpatient hernia operation, and recurrent hernia. Patients were prospectively randomized in a double-blinded manner to receive either 0.5% bupivacaine (Marcaine Abbott Laboratories) or saline continuously for 48 hours at 2 mL/h. Ultimately, 23 patients were randomized into the saline group and 29 into the Marcaine group. ˜ Q Pain Relief System (I-Flow Corporation), The ON consists of a 20-gauge Soaker catheter attached to an elastomeric balloon pump that is capable of infusing a set volume of local anesthetic over a wide area of the surgical site for 2 to 5 days. As the reservoir is filled, the elastomeric membrane of ˜ Q pump creates sufficient pressure (10 pounds the ON per square inch) to push the medication through the connecting tubing, flow-restrictor orifice, catheter, and, finally, into the incision. The flow-restricting orifice prevents free flow of the medication, thereby allowing accurate infusion rate into the surgical field. The scrub nurse assigned to the patient injects the analgesic through the one-way fill port into the pump. The pump is filled with 100 mL of either 0.5% bupivacaine or saline solution as per a computer-generated randomization schema. No changes were made to the anesthesia protocols, surgical technique, or other standard patient care intraoperatively or postoperatively. All patients underwent general endotracheal anesthesia to avoid any bias in the use of differing anesthetic agents. We performed one or more of the hernia repairs without a resident or an assistant surgeon. The operation was performed in the standard manner required for use of the Prolene Hernia System. The ilioinguinal, iliohypogastric, and genitofemoral nerves were carefully manipulated, if necessary. None were divided in any patient. After surgical repair of the inguinal hernia and before wound closure, each surgical site was injected with 20 mL bupivacaine by the operating surgeon. The Soaker catheter was then placed at the superior aspect of the incision between the mesh and the external oblique aponeurosis. Particular attention was paid at the exit site of the catheter. The act of tearing away the sheath of the introducing catheter at the skin level will dilate the site, predisposing to leakage of the solution. This was done after the sheath was withdrawn from the skin level. The external oblique aponeurosis was closed with an absorb-
200
LeBlanc et al
Pain Management after Inguinal Hernia Repair
Table 1. Demographic Data on the Two Groups n Side of procedure Right Left Gender Male Female
Bupivacaine
Saline
29
23
19 10
15 8
29 0
21 2
able suture placed in a running fashion. Scarpa’s fascia was closed with interrupted absorbable sutures and the skin incision was reapproximated with a subcuticular absorbable suture. The introducer site of the catheter and the exposed catheter were covered with a transparent “op-site” dressing. Patients were released to the postanesthesia care unit after the operation and discharged to home according to the institutional standard procedures. Hydrocodone (7.5 mg) tablets were prescribed for breakthrough pain. Patients were evaluated at time of discharge from the postanesthesia care unit, and within the first postoperative week by the operating surgeon. Outcomes measured over the 120 hours postoperatively were: narcotic use, patient pain questionnaire, Visual Analogue Scale pain scale (1 to 5 scale where 1 ⫽ none and 5 ⫽ very severe), pain relief survey (1 to 5 scale where 1 ⫽ a lot, and 5 ⫽ none), site inflammation (visual inspection), and side effects. In this article, results are presented as mean and range unless otherwise stated. Demographics were compared using the Student’s t-test. Comparisons between the groups were made by applying the Mann-Whitney rank sum test and analysis of variance with treatment as a fixed effect in the model where most expected variances suggested that differences ⬎ 30% could be detected with 90% power and p ⬍ 0.05 was considered statistically significant. RESULTS There was no difference between the two groups with respect to gender and laterality of hernia (Table 1). There were no complications in any patient, including leakage of the solution from the catheter site of any significant degree. In the bupivacaine group, 24% (versus 4% in the placebo group) required no narcotics (p ⬍ 0.05) after the surgical procedure. Daily and total narcotic usage for all 5 study days was significantly less (p ⬍ 0.05) in the
J Am Coll Surg
bupivacaine group as well (Fig. 1). The percentage of patients not requiring supplemental hydrocodone was statistically significant for all 5 days (Fig. 2). There were no reports of catheter-insertion site or surgical complication. The pump was removed at 48 hours postoperatively, and the amount of narcotics needed to control pain remained significantly less through the fifth postoperative day. DISCUSSION Infiltration of the surgical wound site with local anesthetic is not a new technique and several trials have shown a benefit using continuous irrigation systems.7,8 Control of postoperative pain in the ambulatory care situation is of interest to surgeons, anesthesiologists, and hospital administrators alike. It is particularly important to control unexpected admissions to the hospital, which could impact the potential financial savings that outpatient surgery imparts on the system. Tension-free mesh repair of inguinal hernia is accompanied with less pain and permits patients to return to normal activities faster.9 Repair of inguinal hernias is largely performed in an ambulatory setting in most patients. Results of any study such as this one must show a meaningful difference in the amount of pain that is experienced by these patients rather than demonstration of a decrease in the length of hospital stay. This analysis revealed that use of ˜ Q pump allows the surgeon to decrease postopthe ON erative pain and use of narcotics even further with an ambulatory continuous infusion pump. There are other
Figure 1. Narcotic use and Visual Analogue Scores (VAS). Narcotic ˜ Q (bupivacaine) group (shaded bars) and placebo usage in the ON (saline) group (black bars) during the first 5 days after operation as assessed by determining morphine equivalency for all narcotics used. *p ⬍ 0.05. VAS scores between the two groups were not ˜ Q bupivacaine group, dotted line; placebo, solid line. significant. ON
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LeBlanc et al
Figure 2. Patients not requiring supplemental hydrocodone use. In ˜ Q (bupivacaine) group (shaded bars), the number of those the ON patients requiring no supplemental hydrocodone was significantly higher than the placebo (saline) group (black bars) at all time intervals (p ⬍ 0.05).
potential benefits that could be realized in this and other more extensive operative procedures, such as laparotomy or incisional hernia repair. Not only does pain decrease patient comfort, but it also affects inflammatory responses and increases catecholamine release. Increased catecholamine release decreases wound perfusion and oxygenation. It has also been shown that postoperative pain decreases subcutaneous tissue oxygenation. Low tissue oxygen values are associated with impaired wound healing and increased risk of surgical wound infections. Consequently, sufficient postoperative pain treatment should increase subcutaneous oxygen tension and subsequently enhance wound healing. Local anesthetic infiltration to the wound may very well provide adequate pain control with the added benefit of enhancing wound healing.10 Adequate pain management increases mobility and decreases risk of development of deep venous thrombosis and pneumonia. Systemic narcotics provide generalized analgesia but may be accompanied by side effects such as respiratory depression, excessive sedation, pruritis, constipation, ileus, nausea, and vomiting. Use of systemic narcotics may not optimize pain management in a specific region of the body because of its centralized effect.The surgeon treats the entire body to manage pain in a specific region. This may lead to decreased mentation, reduced mobility, and a slower return to normal activities. Regional anesthesia, such as single-shot nerve block or epidural, offers the surgeon good analgesia for a specific region of the body. Regional anesthesia may reduce
Pain Management after Inguinal Hernia Repair
201
the need for systemic narcotic medications, but may require painful injections and repeated dosing because of the relatively short half-life of the anesthetic agents. Several randomized trials have demonstrated that when compared with use of systemic narcotic analgesia, use of regional anesthesia with local anesthetics has led to a faster return of gastrointestinal function after lower abdominal operation.11 Infiltration of a surgical incision with a local anesthetic has been shown to provide adequate short-term analgesia and has been shown in some studies to effectively treat postoperative surgical pain. The limitation of this technique is the length of the effect. Long-acting local anesthetic drugs, such as bupivacaine hydrochloride, have renewed interest in use of these agents for local wound perfusion. Interestingly, saline perfusion of the wound has been found to be equally effective in providing pain relief by some, where others did not see a positive effect on pain treatment at all.4 Infiltration techniques with local anesthetics have included bathing the wound at closing (limited in duration), repeated injections (painful, increased risk of infection), and placement of an epidural-type catheter into the wound to allow for repeated bolus injections (time consuming for the caregiver). The pump used in this study is designed to deliver continuous site-specific analgesia for control of postoperative pain, appears to be cost effective, is disposable, and can be used either in an ambulatory or hospital setting. This study validates use of this analgesic technique for treatment of postoperative pain in the hernioplasty patient. There was a statistically significant decrease (p ⬍ 0.05) in the postoperative pain levels and use of narcotics to treat this pain in the patients who were treated with the bupivacaine. This effect was prolonged beyond the actual infusion of the medication. The cause of this finding was not evaluated in the study but one could postulate that diminution of early postoperative pain allowed the patient to minimize use of narcotics, thereby allowing earlier ease of movement and ambulation. Additionally, because the most severe pain that is experienced in the initial 2 days of the postoperative period is notably reduced, the patient has a better sense of well-being, which also promotes earlier return to normal activities. Anecdotally, patients in the treatment arm of this study appeared to return to their activities of daily living and work somewhat earlier than their placebo counterparts. This parameter could not be adequately evaluated during the course of this study because of the bias that
202
LeBlanc et al
Pain Management after Inguinal Hernia Repair
would have been caused by issues such as insurance, workmen’s compensation, type of employment, and safety concerns in these individuals. During the course of this trial, one of the patients underwent an additional hernia repair on the contralateral side of the initial hernioplasty. He agreed to participate in the study again. After the second procedure, the patient commented that he had significantly more pain after that operation. At the completion of the study, it became apparent that the initial infusion was bupivacaine but the second infusion was saline. This is another affirmation of the improvement of postoperative pain in a “blinded” patient. This prospective, double-blinded, and randomized ˜ Q pump has shown that its use evaluation of the ON results in a statistically significant decrease in the postoperative pain and subsequent narcotic usage after open inguinal hernia repair with the Prolene Hernia System. This occurred without an increase in the risk of infection or other complication. Continuous infusion of 0.5% ˜ Q pump is a safe bupivacaine at 2 mL/h through the ON and effective adjunct in postoperative pain management for open inguinal hernia repair. This represents a viable and possibly superior option for prolonged pain management, minimizing the use of narcotics in patients undergoing this and other surgical procedures. Author Contributions
Conception and design: LeBlanc Acquisition of data: LeBlanc, Bellanger, Rhynes, Hausmann Drafting of manuscript: LeBlanc
J Am Coll Surg
Critical revision: LeBlanc Obtaining funding: LeBlanc Supervision: LeBlanc REFERENCES 1. Rodriguez RW, Phillips JT. Inguinal herniorrhaphy as an outpatient procedure. Int Surg 1967;48:561–565. 2. Acute hospital portfolio—review of national findings. Day Surgery Audit Commission; 2001. 3. Chung F, Ritchie E, Su J. Postoperative pain in ambulatory surgery. Anesth Analg 1997;85:808–816. 4. Hendolin HI, Paakonene ME, Alhava EM, et al. Laparoscopic or open cholecystectomy: a prospective randomized trial to compare postoperative pain, pulmonary function and stress response. Eur J Surg 2000;166:394–399. 5. Beauregard L, Pomp A, Choiniere M. Severity and impact of pain after day-surgery. Can J Anaesth 1998;43:1121–1127. 6. Gold BS, Kitz DS, Lecky JH, Neuhaus JM. Unanticipated admission to the hospital following ambulatory surgery. JAMA 1989;262:3008–3010. 7. Vintar N, Pozlen G, Rawal N, et al. Incisional selfadministration of bupivacaine or ropivacaine provides effective analgesia after inguinal hernia repair. Can J Anesth 2002;49: 481–486. 8. Thomas DFM, Lambert WG, William KL. The direct perfusion of surgical wounds with local anaesthetic solution: an approach to postoperative pain? Ann R Coll Surg Engl 1983; 65:226–229. 9. Trabucco E, Campanelli P, Cavagnoli R. New polypropylene hernia prosthesis. Minerva Chir 1998;53:337–341. 10. Hopf HW, Hunt TK, West JM. Wound tissue oxygen tension predicts the risk of wound infection in surgical patients. Arch Surg 1997;132:997–1005. 11. Liu SS, Carpenter RL, Mackey DC, et al. Effects of perioperative analgesic technique on rate of recovery after colon surgery. Anesthesiology 1995;83:757–765.
and is associated with increased morbidity and mortality when compared with the outpatient setting. In response to the increased interest in hastening the time to discharge, efforts to develop anesthetic agents with more favorable recovery profiles and minimization of immediate postoperative symptoms (pain, nausea, emesis, dizziness, fatigue, and headache) have also increased. Of these immediate postoperative symptoms, management of postoperative pain remains a major issue in the acceptance of early discharge by patients and an important concern for anesthesiologists and surgeons. Incidence of moderate-to-severe postdischarge pain is approximately 40% to 70% in the outpatient setting.3 Despite major advances in surgical techniques, which have minimized surgical trauma and the interrelated postoperative incisional pain, postdischarge pain remains the most common reason for readmission to the hospital after outpatient operation.4 Mean incidence of
The first ambulatory inguinal hernia operation was reported in 1967.1 Since that time, the percentage of these operations performed in the ambulatory setting has grown to about 60%. In the United States, nearly 60% of all operations are performed in the ambulatory setting. In the United Kingdom, 68% of all operations are reported to be performed as day operations, with the goal of moving 75% of all elective operations to the ambulatory setting.2 The longer postoperative care needed for subjects admitted to the hospital is expensive
K LeBlanc owns options in I-Flow and is a member of the Ethicon Advisory Board. Supported by a grant from Ethicon Endo-Surgery and I-Flow Corporation. Received March 18, 2004; Revised October 8, 2004; Accepted October 19, 2004. From Surgical Specialty Group Inc, Baton Rouge, LA. Correspondence address: Karl A LeBlanc, MD, MBA, FACS, Surgical Specialty Group Inc, 7777 Hennessy Blvd, Ste 612, Baton Rouge, LA 70808.
© 2005 by the American College of Surgeons Published by Elsevier Inc.
198
ISSN 1072-7515/05/$30.00 doi:10.1016/j.jamcollsurg.2004.10.011
Vol. 200, No. 2, February 2005
LeBlanc et al
readmission because of pain is reported as 45%, reaching as high as 95% for certain gynecologic and orthopaedic procedures.5,6 It is clear that new ways to provide adequate pain relief in the outpatient setting while maintaining subject safety and comfort need to be developed. As an added benefit, patient satisfaction is increased with control of postoperative pain, promoting quicker recovery. The most common treatment for pain after operation is opioid analgesic drug administration, although opioids are associated with unwanted side effects, such as respiratory problems, nausea and vomiting, itching, increased duration of postoperative ileus, and others. These side effects can be decreased with a reduction in the amount of opioid drugs administered. Because a reduction of the daily consumption of narcotics is often associated with a decrease in analgesia, many other treatments for postoperative pain have been evaluated. One of the most effective is epidural analgesia, but the epidural catheter needs to be placed preoperatively, is a fairly invasive method, is not well suited for outpatient use, and maintenance of the epidural treatment can be time consuming and expensive. In the last few years, a new method of delivering continuous wound infiltration with a solution of local anesthetic through an indwelling irrigation apparatus has been used in an increasing percentage of ambulatory surgery patients. This method, which was described by Capelle5 and later by Blades and Ford6 for thoracotomy incisions, uses a fine catheter inserted into the wound before surgical closure. Because of the relatively limited experience with this type of analgesia, we sought to evaluate its use in management of postsurgical pain after open inguinal hernioplasty. This is one of the most commonly performed general surgical procedures in the world. If this was shown to be effective with this outpatient operation, expansion of the use of this methodology for other operative procedures, such as incisional hernia repair or laparotomy, could be recommended. METHODS After Institutional Board Review approval, written informed consent was obtained from 52 unilateral inguinal hernia patients undergoing primary open hernia repair with the Prolene Hernia System (Ethicon, Inc). Patients included in the study were those with an incision length ⬍ 20 cm, age older than 18 years, and able to
Pain Management after Inguinal Hernia Repair
199
give informed consent. Exclusion criteria included allergy to bupivacaine, significant liver or renal disease, candidates for outpatient hernia operation, and recurrent hernia. Patients were prospectively randomized in a double-blinded manner to receive either 0.5% bupivacaine (Marcaine Abbott Laboratories) or saline continuously for 48 hours at 2 mL/h. Ultimately, 23 patients were randomized into the saline group and 29 into the Marcaine group. ˜ Q Pain Relief System (I-Flow Corporation), The ON consists of a 20-gauge Soaker catheter attached to an elastomeric balloon pump that is capable of infusing a set volume of local anesthetic over a wide area of the surgical site for 2 to 5 days. As the reservoir is filled, the elastomeric membrane of ˜ Q pump creates sufficient pressure (10 pounds the ON per square inch) to push the medication through the connecting tubing, flow-restrictor orifice, catheter, and, finally, into the incision. The flow-restricting orifice prevents free flow of the medication, thereby allowing accurate infusion rate into the surgical field. The scrub nurse assigned to the patient injects the analgesic through the one-way fill port into the pump. The pump is filled with 100 mL of either 0.5% bupivacaine or saline solution as per a computer-generated randomization schema. No changes were made to the anesthesia protocols, surgical technique, or other standard patient care intraoperatively or postoperatively. All patients underwent general endotracheal anesthesia to avoid any bias in the use of differing anesthetic agents. We performed one or more of the hernia repairs without a resident or an assistant surgeon. The operation was performed in the standard manner required for use of the Prolene Hernia System. The ilioinguinal, iliohypogastric, and genitofemoral nerves were carefully manipulated, if necessary. None were divided in any patient. After surgical repair of the inguinal hernia and before wound closure, each surgical site was injected with 20 mL bupivacaine by the operating surgeon. The Soaker catheter was then placed at the superior aspect of the incision between the mesh and the external oblique aponeurosis. Particular attention was paid at the exit site of the catheter. The act of tearing away the sheath of the introducing catheter at the skin level will dilate the site, predisposing to leakage of the solution. This was done after the sheath was withdrawn from the skin level. The external oblique aponeurosis was closed with an absorb-
200
LeBlanc et al
Pain Management after Inguinal Hernia Repair
Table 1. Demographic Data on the Two Groups n Side of procedure Right Left Gender Male Female
Bupivacaine
Saline
29
23
19 10
15 8
29 0
21 2
able suture placed in a running fashion. Scarpa’s fascia was closed with interrupted absorbable sutures and the skin incision was reapproximated with a subcuticular absorbable suture. The introducer site of the catheter and the exposed catheter were covered with a transparent “op-site” dressing. Patients were released to the postanesthesia care unit after the operation and discharged to home according to the institutional standard procedures. Hydrocodone (7.5 mg) tablets were prescribed for breakthrough pain. Patients were evaluated at time of discharge from the postanesthesia care unit, and within the first postoperative week by the operating surgeon. Outcomes measured over the 120 hours postoperatively were: narcotic use, patient pain questionnaire, Visual Analogue Scale pain scale (1 to 5 scale where 1 ⫽ none and 5 ⫽ very severe), pain relief survey (1 to 5 scale where 1 ⫽ a lot, and 5 ⫽ none), site inflammation (visual inspection), and side effects. In this article, results are presented as mean and range unless otherwise stated. Demographics were compared using the Student’s t-test. Comparisons between the groups were made by applying the Mann-Whitney rank sum test and analysis of variance with treatment as a fixed effect in the model where most expected variances suggested that differences ⬎ 30% could be detected with 90% power and p ⬍ 0.05 was considered statistically significant. RESULTS There was no difference between the two groups with respect to gender and laterality of hernia (Table 1). There were no complications in any patient, including leakage of the solution from the catheter site of any significant degree. In the bupivacaine group, 24% (versus 4% in the placebo group) required no narcotics (p ⬍ 0.05) after the surgical procedure. Daily and total narcotic usage for all 5 study days was significantly less (p ⬍ 0.05) in the
J Am Coll Surg
bupivacaine group as well (Fig. 1). The percentage of patients not requiring supplemental hydrocodone was statistically significant for all 5 days (Fig. 2). There were no reports of catheter-insertion site or surgical complication. The pump was removed at 48 hours postoperatively, and the amount of narcotics needed to control pain remained significantly less through the fifth postoperative day. DISCUSSION Infiltration of the surgical wound site with local anesthetic is not a new technique and several trials have shown a benefit using continuous irrigation systems.7,8 Control of postoperative pain in the ambulatory care situation is of interest to surgeons, anesthesiologists, and hospital administrators alike. It is particularly important to control unexpected admissions to the hospital, which could impact the potential financial savings that outpatient surgery imparts on the system. Tension-free mesh repair of inguinal hernia is accompanied with less pain and permits patients to return to normal activities faster.9 Repair of inguinal hernias is largely performed in an ambulatory setting in most patients. Results of any study such as this one must show a meaningful difference in the amount of pain that is experienced by these patients rather than demonstration of a decrease in the length of hospital stay. This analysis revealed that use of ˜ Q pump allows the surgeon to decrease postopthe ON erative pain and use of narcotics even further with an ambulatory continuous infusion pump. There are other
Figure 1. Narcotic use and Visual Analogue Scores (VAS). Narcotic ˜ Q (bupivacaine) group (shaded bars) and placebo usage in the ON (saline) group (black bars) during the first 5 days after operation as assessed by determining morphine equivalency for all narcotics used. *p ⬍ 0.05. VAS scores between the two groups were not ˜ Q bupivacaine group, dotted line; placebo, solid line. significant. ON
Vol. 200, No. 2, February 2005
LeBlanc et al
Figure 2. Patients not requiring supplemental hydrocodone use. In ˜ Q (bupivacaine) group (shaded bars), the number of those the ON patients requiring no supplemental hydrocodone was significantly higher than the placebo (saline) group (black bars) at all time intervals (p ⬍ 0.05).
potential benefits that could be realized in this and other more extensive operative procedures, such as laparotomy or incisional hernia repair. Not only does pain decrease patient comfort, but it also affects inflammatory responses and increases catecholamine release. Increased catecholamine release decreases wound perfusion and oxygenation. It has also been shown that postoperative pain decreases subcutaneous tissue oxygenation. Low tissue oxygen values are associated with impaired wound healing and increased risk of surgical wound infections. Consequently, sufficient postoperative pain treatment should increase subcutaneous oxygen tension and subsequently enhance wound healing. Local anesthetic infiltration to the wound may very well provide adequate pain control with the added benefit of enhancing wound healing.10 Adequate pain management increases mobility and decreases risk of development of deep venous thrombosis and pneumonia. Systemic narcotics provide generalized analgesia but may be accompanied by side effects such as respiratory depression, excessive sedation, pruritis, constipation, ileus, nausea, and vomiting. Use of systemic narcotics may not optimize pain management in a specific region of the body because of its centralized effect.The surgeon treats the entire body to manage pain in a specific region. This may lead to decreased mentation, reduced mobility, and a slower return to normal activities. Regional anesthesia, such as single-shot nerve block or epidural, offers the surgeon good analgesia for a specific region of the body. Regional anesthesia may reduce
Pain Management after Inguinal Hernia Repair
201
the need for systemic narcotic medications, but may require painful injections and repeated dosing because of the relatively short half-life of the anesthetic agents. Several randomized trials have demonstrated that when compared with use of systemic narcotic analgesia, use of regional anesthesia with local anesthetics has led to a faster return of gastrointestinal function after lower abdominal operation.11 Infiltration of a surgical incision with a local anesthetic has been shown to provide adequate short-term analgesia and has been shown in some studies to effectively treat postoperative surgical pain. The limitation of this technique is the length of the effect. Long-acting local anesthetic drugs, such as bupivacaine hydrochloride, have renewed interest in use of these agents for local wound perfusion. Interestingly, saline perfusion of the wound has been found to be equally effective in providing pain relief by some, where others did not see a positive effect on pain treatment at all.4 Infiltration techniques with local anesthetics have included bathing the wound at closing (limited in duration), repeated injections (painful, increased risk of infection), and placement of an epidural-type catheter into the wound to allow for repeated bolus injections (time consuming for the caregiver). The pump used in this study is designed to deliver continuous site-specific analgesia for control of postoperative pain, appears to be cost effective, is disposable, and can be used either in an ambulatory or hospital setting. This study validates use of this analgesic technique for treatment of postoperative pain in the hernioplasty patient. There was a statistically significant decrease (p ⬍ 0.05) in the postoperative pain levels and use of narcotics to treat this pain in the patients who were treated with the bupivacaine. This effect was prolonged beyond the actual infusion of the medication. The cause of this finding was not evaluated in the study but one could postulate that diminution of early postoperative pain allowed the patient to minimize use of narcotics, thereby allowing earlier ease of movement and ambulation. Additionally, because the most severe pain that is experienced in the initial 2 days of the postoperative period is notably reduced, the patient has a better sense of well-being, which also promotes earlier return to normal activities. Anecdotally, patients in the treatment arm of this study appeared to return to their activities of daily living and work somewhat earlier than their placebo counterparts. This parameter could not be adequately evaluated during the course of this study because of the bias that
202
LeBlanc et al
Pain Management after Inguinal Hernia Repair
would have been caused by issues such as insurance, workmen’s compensation, type of employment, and safety concerns in these individuals. During the course of this trial, one of the patients underwent an additional hernia repair on the contralateral side of the initial hernioplasty. He agreed to participate in the study again. After the second procedure, the patient commented that he had significantly more pain after that operation. At the completion of the study, it became apparent that the initial infusion was bupivacaine but the second infusion was saline. This is another affirmation of the improvement of postoperative pain in a “blinded” patient. This prospective, double-blinded, and randomized ˜ Q pump has shown that its use evaluation of the ON results in a statistically significant decrease in the postoperative pain and subsequent narcotic usage after open inguinal hernia repair with the Prolene Hernia System. This occurred without an increase in the risk of infection or other complication. Continuous infusion of 0.5% ˜ Q pump is a safe bupivacaine at 2 mL/h through the ON and effective adjunct in postoperative pain management for open inguinal hernia repair. This represents a viable and possibly superior option for prolonged pain management, minimizing the use of narcotics in patients undergoing this and other surgical procedures. Author Contributions
Conception and design: LeBlanc Acquisition of data: LeBlanc, Bellanger, Rhynes, Hausmann Drafting of manuscript: LeBlanc
J Am Coll Surg
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