MEDICAL MATTERS Dr Muiris HoustonLike other branches of medicine, anaesthesia has made major advances over the last decade. I experienced one of its advances at first hand last week.
"Twilight sleep" or monitored anaesthesia to give it its proper term is a technique used for minor surgical procedures such as breast biopsy and oral surgery. It is also widely used to sedate patients undergoing invasive investigations such as colonoscopy, when a flexible fibre-optic telescope is passed into the large bowel for diagnostic purposes.
You are asked to fast from the night before as you would do prior to a general anaesthetic, but there the similarity ends. The anaesthetist sets up an intravenous line and injects the drug midazolam through it. Very quickly, you become woozy and drift off to sleep. But you do not lose consciousness and are able to obey the surgeons requests.
Apart from not feeling pain, one of the major advantages of "conscious sedation" is that you cannot remember anything about the procedure afterwards. You are also fit to leave the hospital or clinic within an hour of the operation finishing, provided you are accompanied by someone and you do not drive.
Later in the day, you begin to experience the usual post-operative pain and it takes until the following morning before a slight headache and muzziness completely disappears. However, compared with a general anaesthetic, there is no nausea or vomiting and of course you are up on your feet much more quickly. You can also eat normally, as the digestive system has not been paralysed.
Regional anaesthesia involves the injection of an anaesthetic near a nerve bundle to numb a specific region of the body. This is achieved by means of a spinal block or using an epidural technique.
One Dublin anaesthetist estimates that 98 per cent of all caesarean sections are now done using either a spinal or epidural anaesthetic, so that the mother is completely conscious and able to bond with her new-born.
An even more surprising statistic is that less than 2 per cent of hip and knee replacements now take place using a general anaesthetic. It is possible to completely anaesthetise the operative field using a spinal or epidural technique.
As the statistic suggests, regional anaesthesia for joint replacement is no longer confined to those considered not medically fit for a general anaesthetic because of a bad heart or poor lung function. It has now become the anaesthetic method of choice.
Anaesthetists emphasise that where a person is simply terrified of being awake during surgery, they will be offered a general anaesthetic to completely knock them out. But for any surgery below the umbilical cord there is now a definite choice for patients.
Local anaesthesia numbs only part of the body, like the hand or foot. It is also extensively used for eye surgery; almost 90 per cent of cataracts are now removed using eye blocks, allowing the anaesthetist and the surgeon to tackle seven cases in a typical three hour operating session.
Deaths from general anaesthesia have dropped dramatically in the last 20 years. According to the American Society of Anaesthesiologists, the risk of death in a generally healthy patient is now one in 250,000 cases, a considerable drop from a mortality rate of one in 10,000 two decades ago.
New drugs and new techniques are the main reason for this decrease.
Modern anaesthesia has come a long way from its 19th century roots. Ether was first used for dental extractions in the US in the 1840s. On December 21st, 1846, the British surgeon Robert Liston amputated a diseased leg at the thigh from a patient who had been anaesthetised with ether. "This Yankee dodge, gentleman, beats mesmerism hollow" Liston pronounced after the successful operation.
Ether was soon displaced by chloroform, which was easier to administer. A key event in chloroform's acceptance as an anaesthetic occurred on April 7th, 1853: Queen Victoria took chloroform for the birth of Prince Leopold. "The effect was soothing, quietening and delightful beyond measure," Her Majesty recorded in her journal. However, the Lancet did not approve, warning in an editorial that "in no case could it be justifiable to administer chloroform in perfectly ordinary labour".
Other gaseous anaesthetics, such as halothane, were subsequently discovered. They are now used in combination with intravenous agents to induce and maintain general anaesthesia. But the real progress has been in the development of twilight, regional and local anaesthesia which has allowed day case surgery blossom and permitted the patient to head home within hours of the procedure.
Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he cannot answer individual queries.