At Duke University Ambulatory Surgery Center, we feel we are blazing new trails toward better postop pain control. Our single-injection and continuous-infusion nerve block techniques are allowing us to routinely do procedures such as total shoulders, mastectomy, open inguinal hernias and unicondylar arthroplasty on an outpatient basis. We also use blocks for laparoscopic cholecystectomies, Nissen fundoplication, tubal ligations and ENT procedures. Soon, we will test the techniques for patients undergoing first-time total knee replacements.

Benefits of blocking
As someone who has experienced the traditional narcotics-centered approach to postop pain control, I perceive that this technique produces profoundly superior analgesia. Our blocks provide pain relief during surgery and for up to 15 to 72 hours postoperatively, depending on whether we use a single-injection or a continuous-infusion peripheral nerve block technique. In addition to the block(s), our typical pain control regimen includes NSAIDs. When the patient is able to drink, we administer acetaminophen and another NSAID such as ibuprofen around the clock for three full days. For patients with stomach or bleeding conditions that contraindicate a traditional NSAID, we may alternately use a COX-2 inhibitor.

Dr. Steele ('[email protected]')) is an Associate Clinical Professor with the Duke University Department Of Anesthesiology.

Our experience
Our surgeons perform two-thirds of all cases and more than 99 percent of orthopedic cases under regional blocks. Our philosophy is that if there is an accessible nerve plexus that serves the surgical area, the patient is willing and there are no contraindications, we will administer a block. We routinely administer sciatic, paravertebral, interscalene, lumbar plexus, spinal, femoral, supraclavicular and axillary nerve blocks. Less commonly, we perform infraclavicular, ankle, epidural and even cranial nerve blocks, among others. Although the physical status of our patients is typically ASA 1 or 2, 19 percent of the more than 23,000 patients who underwent surgery at our center between July 1998 and September 2002 were ASA 3 and an additional 1.2 percent were ASA 4.

During this time, 92 percent of our 14,000 regional blocks were effective in that they produced the sensory, motor, and sympathetic blockade needed for surgery. The remainder required re-block or adjunctive local anesthesia, or they failed altogether and required general anesthesia. As far as postop pain control, our long-acting single-injection blocks provide complete analgesia for 15 hours and some continued pain relief for 24 hours, and the continuous infusion blocks provide excellent analgesia for up to 72 hours, depending on infusion duration. Of the over 23,000 patients treated at our center, 94 percent of regional anesthesia patients had zero VAS scores in the PACU, compared to just 76 percent of general anesthesia patients who had zero VAS scores. Among our continuous infusion patients, 95 percent reported zero VAS scores and none reported a VAS score greater than 3 at 24 hours. Patients who remain at rest with infusion pumps may experience no or very mild pain, and while movement may cause moderate pain, it typically doesn't necessitate narcotics.

Overall, our acute complication rate is less than 0.5 percent, and all complications so far are the direct result of missed blocks. Local anesthetics that inadvertently enter a vein - which in our experience occurs approximately one or two times out of 1,000 blocks - may cause anything from pre-seizure CNS excitation to frank tonic-clonic seizures to cardiac arrest. Missed interscalene blocks may rarely result in accidental total spinal or epidural spread (less than one in 10,000) if they are at the level of the neck and, if the anesthetic makes its way into the cerebral spinal fluid, the patient can go into cardiac arrest. Missed paravertebral blocks may result in pneumothorax.

Important considerations
Here are some important considerations for an aggressive regional anesthesia program:

• Education and training. An absolute mastery of neural anatomy is essential. One must understand the areas served by the various nerves and be able to interpret the signs of neural stimulation to deliver the anesthetic accurately. When we place continuous infusion catheters, for example, we may place a shorter-term catheter to one plexus and a longer-term catheter to another plexus. For knee surgery, we might place a pump in the sciatic nerve plexus for 24 hours but place a pump in the lumbar plexus for three days. For ankle replacements, we might use the opposite configuration, using a sciatic catheter for three days and a femoral catheter for one day.

  It is also necessary to invest in training, as there is a significant learning curve. When we were first learning to do regional blocks, our incidence of pneumothorax due to missed paravertebral blocks was one in 256; now it's one in 4,000. A one-year fellowship at a center doing continuous-catheter infusion is ideal.

• Pharmacokinetic and pharmacodynamic properties. To optimize outcomes, the anesthesiologist should be able to apply a working knowledge of the drug's duration of effect to the clinical situation. The majority of our blocks are long-acting; however, we sometimes use short-acting blocks or we combine short- and long-acting blocks. For a knee scope with debridement of the meniscus, for instance, we may administer a femoral nerve block using long-acting ropivicaine and a sciatic block using short-acting mepivacaine. This provides excellent anesthesia without over-sedation during surgery, yet allows the patient to regain sensation in the foot three to four hours postop while keeping the quadriceps anesthetized longer. Thus the patient is able to walk on crutches earlier and more comfortably.
• Toxicity profiles. We stock only ropivicaine for our long-acting and continuous infusion peripheral nerve blocks. Although it is more expensive than bupivicaine, ropivicaine is less toxic. An accidental venous injection of bupivicaine is more likely to cause seizures or cardiac arrest; also, patients who suffer venous injection with bupivicaine are difficult to resuscitate and may have to go on cardiac bypass until their livers can metabolize the drug. Ropivicaine also more selectively blocks sensory as opposed to motor nerves at low concentrations, so patients can retain more motor function while remaining pain-free.

In the infusion pumps, we use ropivicaine 0.2%. We like to keep the infusion dosage low to avoid anesthetic toxicity, although the dose depends on the site and the type of surgery and the patient's comorbidities. We cut down the base rate in sicker patients to as low as 4 to 6 mLs/hr, depending on the pump, with controlled boli of 2 to 3 mL every 20 to 30 minutes.

Finally, we will not add narcotics or clonidine to any block in an attempt to prolong block duration or increase block intensity. We believe this is ineffective, and clonidine places patients, especially elderly patients, at risk for hypotension and bradycardia.

Continuous-infusion peripheral nerve blocks
Patients who undergo procedures associated with more prolonged, intense pain - such as ACL repairs - are potential candidates for a continuous-infusion peripheral nerve block. When we think a patient might benefit from an infusion pump, we first evaluate his ability to understand the situation and the patient's responsibilities, motivation level and circumstances. We will only consider this option for capable patients with capable caretakers at home. The patient and caretaker must be visually aware and alert, and understand that an insensate limb is vulnerable to injury.

In addition, we teach the patient and caregiver the signs of local anesthetic toxicity and teach the caretaker how to turn the pump on and off, ensure that he knows to turn the pump off should any concerns or questions arise and show him how to remove the catheter. Finally, we put the phone number of the pain nurse, anesthesiologist and surgeon on the pump, and tell the caretaker we are available 24 hours. We call patients at least once daily.

More work ahead
To be sure, there is still more work to be done before this aggressive approach to pain control can become mainstream. So far, however, we have found our aggressive regional approach to be effective, safe and very well received.

Our outcomes studies involving more than 23,800 cases of all kinds reveal that more than 19 out of 20 patients are "very satisfied" with our care after 24 hours and more than nine out of 10 are very satisfied after seven days. And although we have not studied it yet, I believe future research may show that continuous catheter infusion patients have fewer myocardial and thrombotic events, improved sleep and even better performance during rehab.