Implantation of Intrathecal Drug Delivery Systems

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Chapter 16 Implantation of Intrathecal Drug Delivery Systems

Pyung-Bok Lee, MD, PhD, Sang-Chul Lee, MD, PhD, Yong-Chul Kim, MD, PhD

Opioids produce a profound inhibition of the evoked discharge of spinal nociceptive neurons, thereby inhibiting the transmission of pain. Intrathecally administered opioids have no effect on the motor function and autonomic responses. The analgesic effect of opioids is dose dependent and antagonized by naloxone.

Indications

Implantation of an intrathecal drug delivery system is indicated for:

Chronic, intractable pain of malignant and/or benign origin that responds to opioids (Box 16.1)

Long-term infusion of baclofen for severe spasticity of spinal or cerebral origin that responds to baclofen

Long-term intravascular infusion of antibiotics or drugs for chemotherapy

BOX 16.1 Patient Selection Criteria for Use of an Intrathecal Drug Delivery System

Patient with Cancer Pain

Opioid response demonstrated during the screening trial

No difficulty with catheter advance in the subarachnoid space

Inability to control pain with systemic opioids

Life expectancy > 3 months

Patient with Chronic Nonmalignant Pain

Opioid response demonstrated during the screening trial

More conservative treatments have failed

Further surgical intervention is not indicated

Patient has no untreated drug addiction

Psychological evaluation finds no evidence of compensatory need

Contraindications

Contraindications to implantation of an intrathecal drug delivery system are as follows:

Systemic infection

Pump cannot be implanted less than 2.5 cm from the surface of the skin

Known allergies to the materials or medications

Drug abuse

Instrumentation

Equipment required for implantation of an intrathecal drug delivery system consists of the following:

Implantable intrathecal infusion pump (Figs. 16-1 and 16-2)

10-mL syringe for flushing the catheter access port and for skin infiltration

20-mL syringe for emptying the reservoir and filling the pump

22-gauge noncoring needle for emptying the reservoir and filling the pump (Fig. 16-3)

24-gauge noncoring needles for flushing the catheter access port (Fig. 16-3)

0.22-μ filter (Fig. 16-4)

15-gauge spinal needle (Fig. 16-5)

Intrathecal catheter with a stylet (Fig. 16-5)

Anchor (Fig. 16-6)

Catheter passer (Fig. 16-7)

Minor surgical kit (Fig. 16-8)

Surgical glue

Programming device (Fig. 16-9)

Figure 16–1 Various sizes of Tricumed intrathecal pumps (Tricumed Medizintechnik GmbH, Kiel, Germany).

Figure 16–2 Parts of an implantable intrathecal infusion pump.

Figure 16–3 The 24-gauge (left) and 22-gauge (right) noncoring needles used in implantation of an intrathecal infusion pump.

Figure 16–4 A filter and a 22-gauge noncoring needle.

Figure 16–5 A catheter with a stylet (top) and a 15-gauge spinal needle (bottom) for spinal catheterization.

Figure 16–6 Various types of anchors.

Figure 16–7 Parts of a catheter passer.

Figure 16–8 Instruments for a trial of ITDDS. (Intrathecal drug delivery system).

Figure 16–9 Programming device.

Drugs needed for implantation of an intrathecal drug delivery system are as follows:

Lidocaine for local infiltration

10 mg/mL of morphine sulfate (Fig. 16-10) or baclofen

5 mL of preservative-free 0.9% normal saline (for flushing catheter access port when using the SynchroMed II Infusion System pump [Medtronic, Inc., Minneapolis, MN])

Figure 16–10 Package of Highmol (20 mg/2 mL/ampoule)

(BC World Pharmacy Co., Ltd., Seoul, Korea).

Preoperative preparation

Physical examination should include the following actions:

Noting of any entry site infection or skeleton deformity

Recording of relevant laboratory findings

Nonsteroidal anti-inflammatory drug (NSAID), aspirin, and/or anticoagulant therapy should be stopped for 3 to 7 days before and after the procedure.

Patient and caregiver education should be performed as follows:

Instruct the patient on his or her treatment and personal responsibilities.

Explain that if the pump is not explanted at the patient’s death, the pump and alarm should be inactivated.

Explain that if the body is to be cremated, the pump should be explanted to avoid explosion.

The initial dose given by the drug delivery system must be determined according to current pain therapy, as follows:

For a single injection, the initial intrathecal injection should be 0.3 to 0.5 mg of morphine or half the intrathecal equivalent of daily opioid intake.

For multiple bolus injections, a series of intrathecal or epidural injections should be used.

For continuous epidural infusion with a patient-controlled analgesia system, the initial dose should be 0.2 mg/hr of morphine or the epidural equivalent of daily opioid intake; the dose should then be increased every 12 to 24 hours until pain relief is reported.

Procedure

This procedure describes the implantation of a SynchroMed II Infusion System pump (procedure might be slightly different for other products).

Step 1: Pump Preparation

1. Informed consent

2. Check initial pump status (Fig. 16-9):

a. Use a programmer to check current pump status. Ensure that the calibration constant is the same as that shown on the package labeling.

b. Check the pump reservoir volume.

c. Confirm that there are no active alarm events.

3. Empty the pump:

a. Remove the protective cap from the catheter port (Fig. 16-2) by pulling it away. A drop of water will appear from the catheter connector of the pump within 1 to 2 minutes. Leave the protective catheter connector cover off.

b. Insert the 22-gauge noncoring needle (Fig. 16-3) into the reservoir fill port septum until the needle touches the metal needle stop. Maintain negative pressure to withdraw the sterile water from the pump into the empty syringe. Empty the reservoir completely, until air bubbles stop flowing into the syringe (Fig. 16-11).

c. Maintain negative pressure on the syringe during removal of the syringe. Completely empty the pump before refilling it, and ensure that no air remains in the reservoir.

4. Fill the pump with prescribed drug:

a. Attach a filter (Fig. 16-4) and a 22-gauge noncoring needle (Fig. 16-3) to the syringe containing the prescribed fluid.

b. Insert the needle into the reservoir fill port septum until it touches the metal needle stop.

c. When opioid withdrawal symptoms are anticipated, rinsing the pump with 3 to 10 mL of the drug and discarding the drug used to flush the pump before filling the pump will result in a drug concentration of about 98%-99%.

d. After rinsing the pump, slowly inject the prescribed fluid into the pump reservoir at a rate less than 1 mL/3 sec (Fig. 16-12).

5. Flush the catheter access port:

a. Flush the catheter access port using the 22-gauge noncoring needle (Fig. 16-3) and 1 to 2 mL of prepared saline.

b. Insert the needle into the catheter access port septum until it touches the metal needle stop.

c. Inject the saline into the catheter access port septum until fluid is observed at the tip of the catheter access port (Fig. 16-13).

Figure 16–11 Emptying the pump of sterile water. See text for further explanation.

Figure 16–12 Filling the pump with the prescribed drug.

Figure 16–13 Flushing the catheter access port with prepared saline. Observe the fluid flowing from the port.

Step 2: Implant Procedure

The catheter is often implanted while an assistant prepares the pump.

1. Administer prophylactic antibiotics at least 1 hour before the implant procedure.

2. Identify the pump pocket site. This is usually in the abdomen, like the battery pocket site for an implanted spinal cord stimulator (Figs. 16-19 and 15-25).

3. Place the patient in the lateral position with the lumbar region slightly flexed.

4. Administer a local infiltration of lidocaine.

5. Make an incision of at least 5 cm at the needle entry site, 1 to 2 cm from the midline and 1 to 1.5 vertebral levels below the targeted interlaminar space, parallel to the spinous process (Fig. 16-14).

6. Undermine the edges of the incision to expose an area of the fascia to place the anchor (Fig. 16-15).

7. Insert the 15-gauge spinal needle (Fig. 16-5) via a paramedian approach and under C-arm guidance:

a. Orient the bevel of the spinal needle parallel to the dural fibers.

b. A shallow (about 30 degrees from the skin), oblique paramedian insertion technique is recommended. The skin entry point will be 1 to 2 cm from the midline and 1 to 1.5 vertebral levels below the targeted interlaminar space (Fig. 16-16).

8. Remove the stylet to confirm correct placement in the intrathecal space by the presence of cerebrospinal fluid (CSF) leakage.

9. Orient the needle bevel cephalad, remove the stylet, and thread the distal tip of the catheter through the needle to the desired location.

Figure 16–19 Preparation of the subcutaneous pump pocket in the abdominal area.

Figure 16–14 Making a skin incision around the needle entry.

Figure 16–15 Undermining the edges of the incision.

Figure 16–16 Technique for paramedian oblique shallow insertion.

Do not pull the catheter back within the needle to adjust its position. To retract the catheter during its placement, either (a) simultaneously withdraw the needle and catheter and then re-advance it or (b) if significant retraction of the catheter is required, withdraw the needle and catheter completely and then try again.

10. To minimize CSF leakage at the puncture site and later secure the catheter, place purse-string sutures through the ligament around the needle (Fig. 16-17).

11. Carefully remove the needle and guidewire from catheter simultaneously, and clamp the end of the catheter to prevent CSF loss during anchoring and tunneling (Fig. 16-18).

12. Secure the anchor (Fig. 16-6) to the lumbodorsal fascia, not to the subcutaneous fat, with the use of heavy, nonabsorbable sutures. Place the anchor as close as possible to the spinal entry point, using a nonabsorbable suture to prevent dislodgement or kinking of the catheter from spinal and ligament motion. Both ends of the anchor are tied with non-absorbable suture to secure the catheter to the anchor and should not be fixed with surround tissues which may cause catheter fracture because of the tension applied by repeated flexion and extension of body. Apply surgical glue around the anchoring area and spinal entry point of the needle.

13. Prepare the subcutaneous pump pocket in the abdominal area (Fig. 16-19; also see Fig. 15-25).

14. Using a catheter passer (Fig. 16-7), tunnel subcutaneously from the pump pocket incision to the spinal incision (Fig. 16-20):

a. Bend the catheter passer to conform to the patient’s contour.

b. Tunnel from the pump pocket to the spinal incision site at the subcutaneous level.

c. Unlock the obturator tab from the catheter passer.

d. Pull out the obturator.

e. Thread the catheter from the spinal incision site through the catheter passer until it emerges from the obturator handle. Suction and saline may be required during this procedure.

f. Slowly remove the catheter passer.

g. Confirm catheter patency by watching for CSF flow at the pump pocket site.

15. Trim the catheter if necessary, and firmly attach the connector (Fig. 16-2) to the catheter.

16. Confirm catheter patency again by watching for CSF backflow at the connector, and connect the pump to the catheter (Fig. 16-21).

17. Secure the connector with a nonabsorbable suture placed in the suture groove at the base of the connector, and insert the pump into the pocket, coiling the excess catheter behind the pump. Secure the pump with nonabsorbable sutures in the pump pocket (Fig. 16-22).

18. Suture the skin, and apply a dressing.

Figure 16–17 A pursestring suture is placed around the Tuohy needle and will be tied after the needle has been removed.

Figure 16–18 Simultaneous removal of the needle and guidewire from the catheter can prevent CSF loss during anchoring and tunneling (A, B). Flow of cerebrospinal fluid should be observed through the end of the catheter (C), Clamping the end of the catheter with surgical drape can prevent CSF loss and contamination (D).

Figure 16–20 Subcutaneous tunneling from the pump pocket incision to the spinal incision.

Tunnel from the pump pocket to the spinal incision site at the subcutaneous level using cather passer (A, B). Unlock the obturator tab from the catheter passer (C), Thread the catheter from the spinal incision site through the catheter passer until it emerges from the obturator handle (D).

Figure 16–21 Confirming catheter patency by watching for CSF backflow at the connector (A). Connecting the pump to the catheter (B).

Figure 16–22 Pump placement. Securing the connector with a nonabsorbable suture placed in the suture groove at the base of the connector (A), Inserting the pump into the pocket, coiling the excess catheter behind the pump (B). Irrigating the pocket site with sterile saline (C) and, securing the pump with nonabsorbable sutures in the pump pocket (D).

Postprocedural management

After implantation of an intrathecal drug delivery system, the following actions should be taken

Conduct a postoperative neurologic examination.

Instruct the patient not to bathe for 5 days.

Program the pump

(Refer to the manual for the pump, provided by the manufacturer). The bolus setting serves to clear the intrathecal tubing and infuses the drug to the tip of the catheter.

Complete the four primary steps in determining the postoperative priming bolus, as follows:

1. Identify the pump model numbers.

2. Determine the length of the implanted catheter.

3. Determine the total drug volume.

4. Determine the priming bolus, which is calculated as follows: total drug volume × drug concentration

Complications

Procedural problems that may occur after implantation of an intrathecal drug delivery system include the following:

Pump implanted upside down

Pocket seroma, hematoma, or infection

Post–dural puncture headache

Radiculitis, arachnoiditis, or meningitis

Epidural and intrathecal hemorrhage with neurologic injury (Fig. 16-23)

Damage of pump and accessories

Figure 16–23 A, Sagittal T2-weighted magnetic resonance image of the thoracic spine. An oval shaped deposit of hemosiderin can be seen within the spinal cord parenchyma from T8 to T9 with cystic expansion of the cord above the lesion. B, Axial T1-weighted image shows intramedullary location of the catheter within the posterior aspect of the spinal cord on the left.

(Adapted from Huntoon MA, Hurdle MFB, Marsh RW, et al. Intrinsic spinal cord catheter placement: Implications of new intractable pain in a patient with a spinal cord injury. Anesth Analg 2004;99:1763-1766.)

The catheter problems that may occur are as follows:

Catheter obstruction or kinking

Catheter disconnection, leakage, or breakage (Figs. 16-24 and 16-25)

Catheter migration or dislodgement

Catheter fibrosis or hygroma

Figure 16–24 Standard radiograph with injection of contrast agent via the side port shows a leak in the subdural space (arrow).

(From Pasquier Y, Schnider A, Cahana A. Subdural catheter migration may lead to baclofen pump dysfunction. Spinal Cord 2003;41:700-702.)

Figure 16–25 Computed tomography scan showing leak in the subdural space (single arrow) and catheter tip (double arrow).

(From Pasquier Y, Schnider A, Cahana A. Subdural catheter migration may lead to baclofen pump dysfunction. Spinal Cord 2003;41:700-702.)

The following pump problems may be seen after implantation of an intrathecal drug delivery system:

Inability to change the programmed delivery rate

Reservoir contamination

Overfilling of the pump

Failure of the self-sealing septum at the refill port

Movement of the pump in the pocket

Another problem that may occur is drug underdose or overdose, for the following reasons:

Reservoir depletion, mechanical failure, errors in pump preparation or programming, or errors in refilling of prescribed medications through the side-catheter access port or into pump pocket or subcutaneous tissue; such an underdose or overdose may be fatal.

Rapid pressure change, such as with sky diving, scuba diving, diathermy, or hyperbaric chamber therapy; such an underdose or overdose is temporary. Air travel, bathing, and living at high altitude will not affect pump function.

CASE STUDY 16.1 Cancer Pain

A 64-year-old man was admitted to the Seoul National University Hospital Pain Management Center with intractable abdominal pain. He had been diagnosed with advanced gastric cancer 3 years ago and had undergone total gastrectomy, pancreatectomy, splenectomy, and chemotherapy, but the cancer had recurred.

Three months before admission to our pain management center, the patient experienced severe upper abdominal pain and back pain because of infiltration of cancer to the peripancreatic lymph nodes and nerve. Morphine was infused intravenously up to 3 mg/hr using a patient-controlled analgesia device without effectively alleviating the pain. Celiac plexus block and splanchnic nerve radiofrequency thermocoagulation were performed, which achieved temporary reduction of pain. After these treatments, the patient complained only of periumbilical pain for 2 weeks, and thereafter his severe pain was aggravated. OxyContin 320 mg/day, nortriptyline 10 mg/day, alprazolam 0.375 mg/day, gabapentin 900 mg/day, and laxative were also prescribed. However, the patient still complained of severe constipation, urinary retention, and poor pain control.

Intrathecal drug delivery system (ITDDS) was scheduled and a single epidural injection of morphine was performed with 3 mg of morphine in 10 mL of 0.9% normal saline. After the trial administration of epidural morphine, no side effects were noted, and considerable pain relief was observed.

Implantation of the ITDDS was performed 1 day after the test trial of morphine. The skin entry point was the middle of the L4 body, and the intrathecal entry level was L2-L3 (Fig. 16-26). The catheter tip was located at T11 (Fig. 16-27).

Figure 16–26 Intrathecal entry point at L2/3 disc level (single arrow) and catheter shadow in intrathecal area (split arrow).

Figure 16–27 Placement of the intrathecal catheter. A, The tip of the catheter can be seen at the lower margin of the T11 body (upper arrow) and epidural entry point of catherter (lower arrow) at AP fluoroscopic view. B, The catheter shadow (arrow) at intrathecal area on lateral view.

OxyContin 320 mg/day given orally is equivalent to 320 mg/day of oral morphine. A 320 mg/day dosage of oral morphine is equivalent to 107 mg/day of IV morphine, 11 mg/day of epidural morphine, and 1.1 mg/day of intrathecal morphine. The initial drug delivery was 0.5 mg/day (half of the usual daily intake of opioids) of Highmol (20 mg/2 mL/ampoule, BC World Pharmacy Co., Ltd., Seoul, Korea). However, the patient still complained of pain, so an IV injection of 10 mg of morphine was given during the 6-hour observation period. The infusion rate was increased incrementally up to 1.0 mg/day under close observation.

Two days after the implantation, the patient was discharged from the hospital without any complications. The chronic constipation and urinary retention in association with high oral opioid intake had subsided. The patient was totally satisfied with the ITDDS implantation. Three months after the implantation, the infusion rate has not required elevation.

CASTE STUDY 16.2 Complex Regional Pain Syndrome

A 45-year-old man was admitted to the Seoul National University Hospital Pain Management Center with complaints of intractable right leg pain spreading to the whole body after a traffic accident. The patient had been diagnosed with complex regional pain syndrome type I in 2005 and was treated with medications, physiotherapy, psychotherapy, lumbar epidural injections, right lumbar sympathetic plexus blocks with or without alcohol neurolysis, as well as spinal cord stimulator implantation. In spite of these treatments, he complained of intractable pain. He had been treated with gabapentin 3600 mg/day, alprazolam 0.75 mg/day, a laxative, IR codone (an immediate-release form of OxyContin, Mundipharma International Limited, Cambridge, UK) 30 mg/day, hydromorphone 6 mg/day, and a fentanyl patch 50 μg/hr. However, he frequently complained of pain with intensity of 10 on a 10-cm visual analog scale (VAS).

Prior to intrathecal drug delivery system (ITDDS) implantation, a test dose of 3 mg morphine was administered epidurally without stopping the transdermal fentanyl and oral opioid therapy. After the epidural morphine trial, the patient complained of temporary urinary retention but the VAS score for the patient’s whole body pain was reduced from 10 to 0, indicating that an inadequate dose of opioids had been prescribed. Such a favorable response to the epidural morphine trial allowed him to proceed with the implantation of the ITDDS (SynchroMed II, Medtronic, Inc., Minneapolis, MN).

Implantation of the ITDDS was performed one day after the test trial of morphine. The skin entry point is middle of the L4 body and intrathecal entry level was L2-L3. The catheter tip was located at T11 (Fig. 16-28). The total opioid oral intake was calculated to be 154 mg/day of PO morphine: IR codone 30 mg/day PO, hydromorphone 6 mg/day PO, and fentanyl patch (50 μg/hr = 1.2 mg/day of patch). Morphine at 154 mg/day given orally is equivalent to 51 mg/day of IV morphine, 5 mg/day of epidural morphine, and 0.5 mg/day of intrathecal morphine. Highmol (20 mg/2 mL/ampoule) was diluted to 5 mg/mL with a preservative-free 0.9% normal saline, and the initial morphine delivery rate was 0.25 mg/day (half of the usual daily intake of opioids). It was increased gradually up to 1.0 mg/day with an interval of 12 hours, with the patient under close observation for opioid side effects.