Spinal anaesthesia

Q Just under two years ago, I underwent arthroscopy in one of my knees. As the pain and immobility was a great problem for me, we decided to employ a private consultant to do the operation as soon as possible. He offered me a choice of full anaesthesia or one from the waist down. I decided on the latter.

As soon as I recovered from the operation, I began to experience severe back pain, exactly where the anaesthesia injection needle had entered my body. After some weeks, X-rays showed signs of arthritis which, my doctor maintained, was the cause of the pain.

He prescribed medication. When the operated knee started giving me trouble again, I was seen by the surgeon who had done the arthroscopy. I asked him about my back pain and its possible cause. He utterly denied that the pain could result from the spinal injection.

I am now being treated by an osteopath, who has not succeeded in easing the pain. She agrees that these spinal injections can have severe after-effects and, indeed, has observed them in several women who had this type of local anaesthesia during childbirth. Nevertheless, she says, no doctor will admit to them because of the possibility of litigation.

How right she is. I’ve asked four doctors, one a consultant anaesthetist, whether spinal anaesthetics can cause back pain, and the answer has always been ‘no way’.

This is another hard-to-prove area in the medical world, but I think it would be helpful if research could be carried out and published so that the public is warned.- BF, Brecon

A Doctors usually remind us of the proverbial three monkeys - see no evil, hear no evil, speak no evil. Oftentimes, they play dumb about one of the most common and well-known side-effects of drugs and medical procedures. Copious research has been both performed and published about persistent backache after the use of spinal anaesthesia, yet doctors continue to ignore it because they want to believe this clever means of operating on awake patients is safe and effective.

Arthroscopy and arthroscopic surgery is one of the most popular of the so-called ‘minimally invasive’ procedures. More than a million and a half of these are performed every year in the US, usually on the knee and shoulder. So successful is the procedure that surgeons now use it to repair all sorts of other joints, including the ankle, wrist, hip and even the temporomandibular joint (TMJ) in front of the ear.

On the face of it, arthroscopy is a miracle development in keyhole procedures and a big advance over ordinary ‘open’ surgery.

Developed by the Japanese, arthroscopy is a means of peering into a joint through a series of ingenious lenses. The technique employs fibreoptic cables, which project light into the joint. The resulting image is then projected onto a television screen.

The surgeon makes an incision about the joint, injects sterile fluid into the joint space to make all the various bones and tissues easier to see, then makes another incision for insertion of the tiny arthroscope. He can view the joint either through a lens or on the TV screen.

In the case of knees, while he’s in there, the surgeon can take a biopsy or perform minor surgery, such as mending damaged tissues or removing any floating pieces of cartilage or bone. The entire procedure can be wrapped up in an hour.

As with any surgery, however, this is not an exact science, as your own experience shows. Even ‘simple’ surgery isn’t always successful.

Two types of ‘awake’ anaesthesia are used for any surgery below the diaphragm. The spine is covered by three membranes (meninges) - the dura mater, the arachnoidea mater and the pia mater.

Spinal anaesthesia is injected into the subarachnoid (intrathecal) space of the spine - the space between the innermost pia mater and the arachnoid membrane. Epidural anaesthesia, the kind most commonly used in childbirth, is administered in the epidural space - that is, the space between the outermost dura mater and the vertebral (spinal) bones.

Spinal anaesthesia involves just a single injection of local anaesthetic whereas epidurals require continuous or periodical infusions to keep blocking nerve sensation.

Lidocaine, bupivacaine and tetracaine are all commonly used for spinal anaesthesia, sometimes with a vasoconstrictor such as adrenaline (epinephrine), which can prolong the duration of the block by up to 50 per cent. Three-hour surgery, such as a radical prostatectomy, requires a drug like tetracaine, often with adrenaline but, for knee arthroscopy, which is considered minor routine surgery, it’s likely that your anaesthetist opted for the relatively short-acting lidocaine. Occasionally, fentanyl is given to prolong the duration of the analgesia, but it also increases the incidence of minor adverse effects, such as itching and wheals (AANA J, 1999; 67: 337-43).

No doubt you were lured into having spinal anaesthesia because of the suggestion that it is less invasive than general anaesthesia, with fewer side-effects. At first glance, it would seem that spinal anaesthesia is the safer option. It’s also attractive because you supposedly have a shorter recovery time and a minimal exposure to the drugs. The compounds used for spinal anaesthesia also block off your sensation for less time than do the drugs used for general anaesthesia.

A review of studies comparing general and spinal or epidural types of anaesthesia concluded that surgery using epidurals is less likely to produce adverse effects, no matter what the type of surgery. Nevertheless, the study only considered those consequences immediately after the operation that are typical of general anaesthesia, such as deep vein thrombosis and respiratory depression. The study did not examine any effects over time and certainly never looked at the issue of spinal problems after epidurals. The long-term effects of spinal blocks on the back were not discovered because the question was apparently never asked (BMJ, 2000; 321: 1493-7).

Of the few studies that have been done, none shows an advantage of spinal anaesthesia over other types of anaesthesia for minor surgery, other than the fact that the patient stays put and can’t move about as he can with epidurals (Saudi Med J, 2000; 21: 10071-3). Indeed, one study comparing all three types of anaesthesia for outpatient knee arthroscopy found that epidural anaesthesia provided recovery and discharge times comparable to those with general anaesthesia, but that spinal anaesthesia was associated with a longer discharge time and increased level of side-effects (Anesth Analg, 2000; 91: 860-4).

These side-effects include hypovolaemia (abnormally low circulating blood volume) and coagulopathy (a disorder of the blood-clotting mechanism). Patients who develop this blood-clothing disorder are at risk of developing haematomas (an accumulation of blood), which can compress the nerve roots or spinal cord to cause spinal pain, neurological deficit or even permanent paralysis. A low circulating blood volume could lead to severely low blood pressure.

Spinal anaesthesia can also cause hypotension (J Med Assoc Thailand, 2001; 84: 5256-62), a reduction in the viscosity of the blood (Anesth Analg, 1992; 74: 635-40) and unexpected cardiac arrest (Almindelilge Danske Laegefor, 1995; 157: 2860-1).

Spinal anaesthesia requires a steady, experienced hand to position the patient and insert the needle. If it isn’t placed just right, the patient won’t get the right amount of drug or can suffer pain afterward.

There is no question that spinal anaesthesia can have devastating effects on the nervous system, a situation that has been known for nearly 50 years. Even in the 1950s, long-term back problems with spinal anaesthetic were being reported (JAMA, 1956; 161: 586-91).

Numerous studies have shown that it can cause transient neurologic symptoms (TNS), particularly in patients given lidocaine. In one study, 22 per cent of patients given lidocaine had TNS (Anesthesiology, 1996; 88: 619-23). In one instance, one 50-year-old woman given spinal anaesthesia for arthroscopy of the right knee suffered severe cramp-like pain in both buttocks that radiated to her thighs, a situation which carried on for 36 hours.

The most devastating side-effect can be adhesive arachnoiditis or inflammation of the arachnoid space in the spine, causing long-term debilitating pain.

In one instance, a 75-year-old woman was placed under spinal anaesthesia during her total knee replacement. Although the operation was successful, afterwards she began complaining of severe low back pain and the fact that she couldn’t move her lower legs. Eight hours after she’d had the anaesthetic, she was still paralysed. Eventually, a myelogram showed inflammation of the arachnoid space in the spine and MRI showed scarring of the spine. Two years later, her condition was unchanged (Jpn J Anesthesiol, 1999; 48: 176-80).

Rarely, this type of anaesthesia can cause nerve palsy. One study of more than 10,000 total knee replacements uncovered 32 cases of postoperative nerve palsies of the outer legs. Epidural anaesthesia was also found to be significantly associated with nerve palsy, as was spinal anaesthesia to a lesser extent (J Bone Joint Surg, 1996; 78: 177-84).

Spinal problems are also common with epidural anaesthesia. According to a study carried out at the University of Birmingham Medical School (BMJ, 7 July 1990), nearly a fifth of women (18 per cent) with epidural anaesthsia during labour reported long-term backache. The report concluded that, out of every 100 women who have an epidural during labour, eight will develop long-term backache as a direct consequence.

It also seems that spinal anaesthesia of every variety causes short- or long-term trauma of some degree. In a postmortem study of 10 patients who’d had postoperative epidurals (Anaesthesia, 1990; 45: 357-61), all 10 had evidence of “non-specific epidural inflammatory reactions” and seven showed signs of epidural infection. This may result from the needle itself or some type of contamination, as there is evidence that one-fifth of those receiving epidurals have contamination (Anesth Analg, 1977; 56: 222-5).

Although it is impossible to diagnose the extent of the damage you have suffered, it may well be that you have some sort of inflammation causing the pain. As manipulative therapy hasn’t worked, you may wish to try acupuncture and homoeopathy, proved to alleviate pain. As for your knee, since the surgery was not entirely successful, you could
try taking glucosamine/chondroitin supplements, which have solid evidence of sorting out joint problems.