Alternatives to Epidural

Posted 12 years ago by David Belavy

By David Belavy

Last week this blog was deliberately provocative by arguing that an epidural causes surgical complications. However, it is almost certainly true that anything that keeps a patient hypotensive or immobile from weakness will slow recovery and increase the risk of surgical complications. Just as patients in uncontrolled pain will recover very slowly. So what is the right postoperative analgesic regimen to optimise recovery?

The mainstays of postoperative analgesia, morphine and its related drugs, are excellent analgesics but they cause numerous problems like sedation, vomiting, and respiratory depression. So we add other drugs and call it "multimodal analgesia" in the hope of reducing those side effects. Paracetamol is well tolerated but offers only a little analgesia. Non-steroidal anti-inflammatory drugs offer a bit more analgesia but we need to consider gastric ulceration, renal impairment and sometimes their antiplatelet effect. Tramadol is supposed to cause less respiratory depression than opioids but definitely causes nausea and delirium and the oral opioids still contribute to constipation. “Multimodal analgesia” combines many of these drugs and, in fact, it will help most patients recover well.

I am very keen on the use of local anesthetics. Epidurals act on the nerve roots as they leave the dura. They can provide excellent analgesia but can cause urinary retention, leg weakness and vasodilation causing hypotension. There are some papers suggesting that blood flow in epidural-affected organs is directly dependent on the blood pressure. In those patients, fluid loading may not fix the hypotension and vasoconstrictors may be needed to improve perfusion.

Alternatively, we can use local anesthetics more peripherally to provide analgesia for abdominal incisions.

The anterior rami from the thoracic spine become intercostal and subcostal nerves to innervate the anterior abdominal wall. Branches of L1 supply the ilioinguinal and iliohypogastric nerves which innervate the lower abdomen and groin. Injecting local anesthetic around these nerves can reduce the somatic pain that arises from midline, Pfannensteil and Maylard incisions.

These nerves travel in the abdominal wall between the two inner muscle layers, the transversus abdominis and the internal oblique muscles. This plane has been termed the Transversus Abdominis Plane (TAP). It can be difficult or unreliable finding these nerves using anatomical landmarks but ultrasound helps us see the correct location.

The "posterior" TAP block involves injecting local anesthetic into the transversus abdominis plane in the midaxillary line between the costal margin and the iliac crest. The T10-T12 nerves pass through this plane and the block works for incisions below the umbilicus. You can expect benefit from the midline out to the lateral border of the rectus muscle. The “lateral” branches of the intercostal nerves described in the textbooks don’t seem to be as reliably blocked so incisions that extend beyond the border of the rectus muscle don’t show as much benefit. I think that this block requires a "moderate" level of skill with ultrasound guided regional anesthesia and can quickly become very difficult in obese patients. That said, some surgeons can overcome this problem by inserting a needle from inside the peritoneum, through one muscle layer and injecting local themselves

If your incision extends above the umbilicus, the T6-10 intercostal nerve roots can be anesthetised by inject local in the TAP just below the costal margin. This block certainly increases the difficulty and requires a high level of skill from the anesthetist. As surgeons know, the muscle layers become aponeuroses and divide around the rectus abdominis muscle meaning that getting the needle into the right plane can be tricky. Again obesity makes this hard but it can be worth the effort.

If your incision is a particularly low transverse incision (Pfannenstiel, Maylard), L1 anesthesia may be required. The trick with the ilioinguinal nerve is that it can enter the TAP in front of the midaxillary line. If you want to block it, local anesthetic should be injected superior and medial to the anterior superior iliac spine but still between the internal oblique and transversus abdominis.

All of these blocks are essentially "field" blocks meaning that large volumes of local anesthetic (20ml a side) are injected to spread through the plane and anesthetise the nerves. You can expect 12-18 hours of analgesia but inserting a catheter allows repeated top-ups so you can extend the benefit for a few days.

There are two other surgical options that can be considered. Rectus sheath or pre-peritoneal catheters can be tunneled on each side parallel to a midline incision. Dilute local anesthetic (eg 0.2% ropivacaine) can be run at 5ml/hr on each side through a pump or elastomeric device. I’m not sure if these catheters work on nerves passing posterior or through the rectus muscle, or if the local spreads directly to the wound. Regardless, they can be helpful. Systems like the Painbuster free patients up from infusion pumps and allow them to mobilize. But, I’m not aware of any randomized data that demonstrates the efficacy of pre-peritoneal catheters.

Finally, a wound infusion catheter where a multi-orifice catheter is placed in the rectus muscle or immediately in front of it during wound closure also offers benefit. Low dose infusions of more concentrated local anaesthetic (eg 2ml/hr) can provide analgesia without making the dressings too wet. However, until data comes out saying that wound dehiscence or infection is not increased, some people will remain concerned about this complication.

An important limitation to these techniques is that visceral pain sensation is not blocked and still requires narcotic analgesia. The practice of "multimodal analgesia" relies on using multiple drugs at sensible doses so that side effects can be minimised and local anesthetics certainly have a lot to contribute here.

With all of this talk of analgesic techniques, we need to remember that the goal should always be returning our patients to normal daily activity. We want our patients to eat, drink, toilet and mobilise independently and rapidly return to their work and normal life. We have many techniques available to achieve this and there will be no single right technique. We need to consider each patient, their operation, their surgeon and anaesthetist, and the hospital and home situation in which they will find themselves. If morphine injections or epidural analgesia are the right techniques to achieve recovery, then that’s what we should do. However, if local anesthetic techniques can safely reduce the pain and side effects of analgesia, then they deserve careful consideration. The only way we will know what works and doesn’t work is if we look at how our patients recover and ensure that our techniques are helping them back to their normal lives.