Anesth Analg 2008; 107:1393-1396
© 2008 International Anesthesia Research Society
doi: 10.1213/ane.0b013e318181b818
ANALGESIA
Perioperative Management of Patients with an Intrathecal Drug Delivery System for Chronic Pain
Jay S. Grider, DO/PhD*,
Raeford E. Brown, MD , and
George W. Colclough, MD*
From the Department of Anesthesiology, Divisions of *Pain Medicine, and Pediatric Anesthesiology; University of Kentucky, Lexington, Kentucky.
Address correspondence and reprint requests to Jay S. Grider, DO/PhD, Assistant Professor, University of Kentucky College of Medicine, 800 Rose St. Suite N 201, Lexington, KY 40536. Address e-mail to jsgrid2{at}email.uky.edu. or www.mc.uky.edu/anesthesiology.
Abstract
The use of intrathecal medications in the treatment of chronic pain is becoming more commonplace. As such, the incidence of encountering patients receiving therapy via an intrathecal drug delivery system in the perioperative period will also increase. In this case series, we discuss anesthetic management and postoperative analgesic issues in three patients with indwelling intrathecal drug delivery systems placed for treatment of chronic pain.
Just as with other implanted medical devices, such as cardiac pacemakers, internal defibrillators, and insulin pumps, unfamiliarity with intrathecal drug delivery system (IDDS) technology can create uncertainty concerning perioperative patient management. Although patients with IDDSs are undergoing surgery more often, the literature is silent concerning perioperative management of patients with these devices.1 The following case series reports anesthetic management and postoperative analgesic requirements of three patients with an IDDS.
CASE DESCRIPTION
Case 1
A 73-yr-old ASA class 2 woman presented for rectocele/ enterocele repair. An IDDS, delivering 1.4 mg/d of morphine was found to be functioning normally. The IDDS had been placed for chronic low back pain secondary to spinal stenosis. After discussion with the Chronic Pain Service, a decision was made to avoid epidural analgesia for postoperative pain control. No changes were made to the programming of the IDDS. The patient was taken to the operating room and underwent an uneventful general anesthetic. Intraoperatively, she received 200 µg of fentanyl and 10 mg of morphine IV. In the postanesthesia care unit (PACU), her IDDS was reinterrogated, found to be functioning normally, and no changes were made. The patient’s first report of postoperative pain was 25 min after arrival in the PACU. She received a total of 16 mg of IV morphine during a 1 h PACU admission. The Acute Pain Service was consulted and initiated IV patient-controlled analgesia (IVPCA) using hydromorphone 0.1 mg/mL with a 6-min dosing interval, 1 mL injection per patient request (PCA dose), and no basal rate. Using this method, the patient’s pain was maintained between 3 and 5/10 on a numeric pain rating scale, as assessed by the acute pain nursing staff without additional monitoring on the hospital ward. The patient averaged 31 attempted injections per 12-h period via the IVPCA receiving 2.3 mg of IV hydromorphone during the first 12 h and 1.9 mg in the next. On postoperative day 2, the patient was converted to Percocet 5/325 three times daily for acute on chronic pain control by the surgical service. Despite the lack of correlation with the previous IV hydromorphone requirement, she did well after conversion to the oral regimen and was discharged on postoperative day 3 without complication. On follow-up 2 wk later, she was recovering without incident.
Case 2
A 43-yr-old woman presented for elective revision of a lumbar spinal fusion from L2 to the sacrum with L3–4 decompression and removal of segmental hardware. She was referred for evaluation of her IDDS and recommendations for intraoperative and postoperative management. Her medical history was positive for tobacco abuse, depression, lumbar spinal stenosis, and mild chronic obstructive pulmonary disease. She reported multiple general anesthetics without complication. She had an IDDS placed in 2003 and was receiving 2415 µg/d of intrathecal fentanyl. Additionally, she used a 75 µg transdermal fentanyl patch. Adjunctive pain medications included ketoprofen and topiramate. She reported her pain to be 8/10 on a numeric pain rating scale. No changes were made to her IDDS infusion or to the transdermal fentanyl patch before progressing to the operating room. She underwent an uncomplicated general anesthetic and surgical procedure. Intraoperatively, it was discovered that the intrathecal catheter was in the superior portion of the operative field. Initial attempts to avoid catheter manipulation were abandoned, and the catheter was temporarily removed until the operation was completed. The same intrathecal catheter was then reintroduced into the intrathecal space via a new puncture site prior to closing the incision An IDDS myelogram after the procedure, but before tracheal extubation, demonstrated that the catheter and connections were intact. The patient received 450 µg of IV fentanyl during the operation. During a 5-h PACU stay, the patient received 2 mg of IV hydromorphone, 16 mg IV morphine, 250 µg of IV fentanyl, and 5 mg of IV methadone. She consistently reported pain scores of 8–9/10 on a numeric pain rating scale despite aggressive analgesic therapy. During this time, her IDDS was interrogated and found to be functioning normally. An IVPCA with hydromorphone 0.2 mg/mL with a basal of 1.5 mL and a 1 mL PCA dose with a 6-min lockout was initiated. The patient received a 0.4 mg bolus of IV hydromorphone every 4–6 h by the acute pain nursing staff on the orthopedic hospital ward. On postoperative day 3, the patient was converted to oxycodone SR 80 mg twice daily, and the transdermal fentanyl patch was discontinued in an attempt to gain better pain control via opioid rotation. Her reported pain score improved to 6/10. She was discharged on postoperative day 4 on this oral regimen with instruction to promptly follow-up with her pain management physician in an outlying community.
Case 3
A 60-yr-old man who experienced 25% total body surface area burns while disposing of trash near his home presented to the emergency department. He had an IDDS implanted 3 yr ago because of lack of improvement in pain control after lumbar laminectomy and cervical discectomy. The pain service was consulted for management of acute on chronic pain. In the intensive care unit, interrogation of his IDDS revealed an infusion of 13.9 mg/d of morphine and 1.25 mg/d of bupivacaine intrathecally. He was started on hydromorphone 0.2 mg/mL via an IVPCA with no basal, a 1 mL PCA dose and a 6-min lockout with standard critical care nurse monitoring in the burn intensive care unit. On hospital day 3, a basal of 1.5 mL/h was added secondary to poor pain control. Ketamine 0.5 mg/mL was added to the PCA prescription on hospital day 4 with marked improvement in pain control. The patient was taken to the operating room twice for debridement of the burns. Before the first surgical procedure, the anesthesiologist was concerned about intraoperative hypotension secondary to the intrathecal bupivacaine infusion; however, both the initial and subsequent general anesthetics were uneventful. The patient required 8 and 14 mg of morphine IV in the PACU after each surgery, respectively. On hospital day 10, the IVPCA infusion was decreased by half and oral methadone titrated to a pain score of 5/10 on a numeric pain rating scale over 48 h. The final dose of methadone required was 40 mg three times daily for the acute pain component whereas the IDDS dosage was unchanged. On hospital day 13, his IDDS reservoir was uneventfully refilled with morphine 40 mg/mL and bupivacaine 7 mg/mL using standard techniques. The patient was discharged on hospital day 18 with adequate pain control on 40 mg of methadone by mouth three times daily and continuing the preadmission infusion via the IDDS. He was instructed to follow up with his chronic pain physician for modification of the drug regimen upon discharge.
DISCUSSION
There are currently no recommendations or consensus statements from the major pain societies concerning perioperative management of patients with an IDDS.2 This deficit in the literature was recently highlighted in a correspondence which anecdotally describes one physician’s approach to the management of approximately 20 patients undergoing surgery with an IDDS placed for chronic pain.2 The author reports that acute postoperative pain after a variety of surgical procedures was managed with IV opioid PCA without complication.2
A common perioperative management concern is that patients with an IDDS may be more susceptible to respiratory depression and sedation with administration of parenteral opioids.3 Additional perioperative management misconceptions are that; (i) the IDDS may provide adequate pain control for the postoperative period, (ii) the infusion of the IDDS may be modified to provide acute pain control,4 and (iii) the presence of the reservoir or the placement of the intrathecal catheter may interfere with surgical access or performing regional anesthesia. Although not directly addressing patients with an IDDS, several issues regarding postoperative pain management in patients on chronic intrathecal opioid therapy may be applicable.
Two reviews of acute pain management in the opioid-dependent patient summarized the literature.5,6 In these reviews, it was suggested that the current daily dose of opioid, oral or transdermal, be administered throughout the perioperative period. This recommendation is based upon the concept that the daily dose of prescribed opioid provides a baseline narcotic requirement, which must be maintained.5 Use of regional or neuraxial analgesia is encouraged whenever possible.7 IVPCA with opioid has also been successfully used in this patient population.5,6 Sedation and respiratory depression are typical concerns of caregivers delivering parenteral opioids for acute pain management to patients receiving opioids chronically.3 It has been suggested that these outcomes are less likely than poorly controlled pain because of opioid tolerance.5 Opioid tolerance is suspected whenever a previously analgesic dose of an opioid becomes less effective.8 Tolerance also manifests itself as diminished sensitivity to the respiratory depressant and sedative effects of opioids.8 Based on these observations, it seems reasonable to extrapolate that IVPCA use concurrent with an IDDS is probably acceptable. Indeed, in the current series, patients had adequate pain control without complications, such as sedation or respiratory depression, using this regimen.
Addressing other concerns/misconceptions, a case report of labor management of a parturient with an IDDS suggested that epidural analgesia may be performed safely.4 In this report, the initial management plan was to use the IDDS for provision of labor analgesia; however, rapid progression of labor necessitated epidural placement.4 Because the epidural catheter was placed at a remote spinal interspace based on physical examination, the possibility of disrupting the indwelling intrathecal catheter seemed remote.4 This method of selecting an appropriate interspace may prove unreliable however.9 Many IDDS implanters use a paramedian approach to intrathecal catheter placement, resulting in a discrepancy between the assumed spinal interspace based on physical examination and the actual spinal interspace accessed. Fluoroscopic examination with contrast injection through the intrathecal pump side access port is the only reliable way to determine the spinal interspace and subcutaneous course of the intrathecal catheter once it exits the subcutaneous implant site. Although this was not feasible for labor management, in other settings, it may be prudent to consider use of fluoroscopy to guide placement of neuraxial and regional anesthetics to limit the possibility of intrathecal catheter disruption. Clinicians should have a clear understanding of the location and course of the catheter from the connection to the drug delivery system, through the insertion site at the dura to the spinal level of the catheter tip prior to attempting neuraxial analgesia for acute pain management.
Additionally, in this report, the IDDS programming and infusate were to be altered for use as an analgesic device for active labor.4 This plan was apparently abandoned because the IDDS programming and drug content could not be manipulated with speed and ease, resulting in the need for placement of an epidural catheter for delivery. Programming and exchange of pump reservoir contents is a complex task requiring experienced personnel. This complexity increases the possibility of error when attempting to use an IDDS for acute pain management. Further, administering drug boluses can be cumbersome and preparation of intrathecal grade pharmaceuticals can incur increased expense. Additionally, not all IDDS have complex programming capabilities, thus eliminating the possibility of use as a titratable postoperative pain modality. Because of these considerations, we recommend that clinicians should not attempt to use an IDDS for management of acute pain in the perioperative period.
In the preoperative setting, clinicians may either (i) decrease or suspend the intrathecal infusion while recognizing the need for supplemental baseline analgesia or (ii) continue the current intrathecal infusion rate. In an analogous situation, it has been advised that transdermal fentanyl administration should be continued in the perioperative period.5,6 Likewise, in the current series, we elected to continue the intrathecal dug delivery without interruption or alteration while using patient-controlled parenteral opioids to provide postoperative analgesia. Perioperatively, clinicians must also realize that abrupt cessation of intrathecal medications may have serious complications. For instance, abrupt discontinuation of intrathecal baclofen and clonidine has been associated with life-threatening withdrawal symptoms and rebound hypertension, respectively10,11 Additionally, without careful consideration of the relative opioid requirement when converting between intrathecal and IV routes of administration, it is possible to dramatically under or overdose patients. We therefore recommend maintenance of the baseline intrathecal infusion with supplemental IV or oral opioids in the perioperative period.
Intraoperative and postoperative anesthetic management concurrent with an IDDS often centers around two issues: intraoperative analgesia and potential impact of intrathecal medications on anesthetic administration. One strategy to ensure adequate analgesia during transition from the intraoperative to postoperative period involves titration of the intraoperative parenteral opioids to respiratory rate during general anesthesia.1 This technique, although central to basic anesthesia practice, would not be contraindicated in patients receiving opioids via an IDDS. A potential intrathecal drug interaction with anesthetic drugs is a more complex issue and beyond the scope of the current report. Of note, according to the prescribers guide from Medtronic Inc. (Minneapolis, MN), use of electrocautery is compatible with a programmable IDDS. In the postoperative period, a potential concern surrounds monitoring of the patient receiving oral or parenteral opioids in combination with an IDDS. Although respiratory depression and sedation are uncommon in the opioid-tolerant patient, monitoring with continuous pulse oximetry is reasonable.5,6
Medications approved by the Food and Drug Administration for intrathecal use are morphine, the N-type calcium channel antagonist ziconotide and baclofen (Information for prescibers, Medtronics Inc.). As previously mentioned, abrupt cessation of an intrathecal baclofen infusion may result in life-threatening withdrawal symptoms.10 The clinician must be alert to this scenario perioperatively because symptoms of baclofen withdrawal may not appear until several hours after the infusion has stopped. Other medications commonly used in IDDSs include the opioids hydromorphone and fentanyl and adjunctive drugs such as clonidine, and bupivacaine. The anesthetic implications of intrathecal hydromorphone and fentanyl should not differ appreciably from that of morphine. The impact of other intrathecal adjunctive drugs in the perioperative period, however, is unclear.
Ketamine was used via the IVPCA in the third case reported in an attempt to better control pain secondary to the burns and continuing debridement thereof. It has been suggested that this N-methyl-d-aspartate (NMDA) receptor antagonist decreases opioid requirements by altering opioid tolerance.8 The effect of NMDA antagonism on acute pain management in humans is an emerging area of study; however, both animal data and studies done in the chronic pain setting suggest a link between NMDA receptor antagonism and decreased opioid tolerance.8 Although it is debatable that short-term infusion of ketamine would significantly impact long-term opioid tolerance, in this patient, the potential benefit of NMDA receptor antagonism and the excellent analgesia provided by ketamine proved beneficial during the acute recovery phase. The patient was subsequently converted to oral methadone, which displays weak NMDA receptor antagonism, also with excellent pain control.12
There are some obvious limitations to the use of a small case series in a global sense when dealing with an emerging patient population. For instance in the current report, the wide variety of intrathecal dosing of opioids resulted in vastly differing postoperative analgesic needs. Thus, it was necessary to tailor therapy to specific patient analgesic requirements preventing a uniform approach to any one patient. Additionally, the variety of surgical procedures and underlying pathophysiology of each case undoubtedly impacted analgesic needs. Taken together, these considerations underscore the need for consensus guidelines regarding this issue as more data emerges.
In conclusion, we report the perioperative management of three patients with an indwelling IDDS delivering opioids for chronic pain therapy. In all cases, the IDDS was interrogated and the infusion continued perioperatively. None of the three patients experienced opioid-induced sedation or respiratory depression, despite the use of parenteral opioids using traditional PCA methods. We recommend the following: (1) interrogate the IDDS pre- and postoperatively understanding that electrocautery does not interfere with the device, (2) continue intrathecal therapy (recognizing that abrupt cessation of baclofen can be life-threatening) as a baseline analgesic requirement and supplement with appropriate oral of patient-controlled bolus IV opioids as needed, taking into consideration the likelihood of opioid tolerance, (3) use a multimodal analgesic approach when possible to limit the impact of opioid tolerance, and (4) determine the course of the intrathecal catheter preoperatively to prevent surgical or regional anesthetic disruption of the intrathecal infusion.
Footnotes
Accepted for publication Mar 25, 2008.
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