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Modern machines and drugs now take the guesswork out of anaesthetising a patient, contributing to very low death rates during surgery
 Surgery is no longer the terrifying prospect it was in the mid-19th century, since the discovery and use of drugs which induce a state of unawareness. To a patient, being anaesthetised is as simple as lying on the operating table, counting down and then waking up in a bed hours later with the surgery completed. From the days when ether was first used, anaesthesia has made possible surgical procedures which would be unimaginable otherwise. Anaesthesia, however, involves more than putting a person to sleep. The drugs used can have a powerful effect on the vital functions of the body.
General anaesthesia is a loss of consciousness that also affects the body's ability to independently maintain its airway and keep the heart beating normally. The cocktail of drugs given puts a patient into a deep sleep, provides pain relief and at times, relaxes the muscles to prevent movements. However, if a procedure calls for only a local or regional anaesthetic to be used – that is, numbing only a particular part of the body – the patient may choose to be or not to be sedated at the same time.
Sedation is a continuum, with a state of comfortable sleep on one end and a deep unconsciousness on the other. The drug-induced state of sedation allows a patient to sleep comfortably while being able to respond to verbal and tactile stimuli. For instance, a patient is able to say his name and bite when he feels something being placed in his mouth. But if the sedation is deep enough, the patient can enter a state akin to being placed under general anaesthesia, during which the doctor may need to support his airway to maintain his breathing.
The safety of anaesthesia has been in the spotlight, with recent court cases here and in the United States involving the use of a powerful sedative called propofol. They include inquiries into the deaths of pop star Michael Jackson in the US and property management firm boss Franklin Heng here. But, in fact, the anaesthesiologist’s arsenal has expanded over the decades, and now include more sophisticated monitoring equipment and newer drugs to deaden the pain. These have led to major improvements in patient safety, say anaesthesiologists here. Dr Chong Jin Long, president of the College of Anaesthesiologists who runs his own practice at Mount Alvernia Medical Centre, said worldwide, anaesthesia-related deaths among those below 60 years of age used to be one in 20,000 before the 1970s. It has dropped to one in 185,000 now – so low that it is not expected for death to occur in the operating theatre. These patients typically die from respiratory complications which result from inadequate monitoring during surgery, Dr Chong added.
PATIENT’S WORST NIGHTMARE
Aside from dying on the operating table, it is every patient’s worst nightmare to awake halfway to feel every bit of the surgery in progress. Thankfully, such intra-operative awareness is now very rare with the use of a piece of monitoring equipment known as the bispectral index, said Dr Ho Kok Yuen, clinical director of Raffles Hospital’s pain management service. A patch strip with electrodes is placed on the patient’s forehead and connected to a monitor to record brainwave activity, a measure of the level of consciousness. A low value will indicate the patient is in a state of hypnosis, while a high value will signal to the anaesthesiologist that the drug dose is insufficient to keep the patient unconscious. In the past, this was “guesswork” with doctors intervening based on patients’ reactions, said Dr Ho.
Autonomic signs of inadequate anaesthesia include sweating and tearing. As a result, doctors had a tendency then to give more anaesthetic drugs to prevent intra-operative awareness, said Dr Ho. The downside is that a higher dose may lead to low blood pressure and increase the risk of a stroke and heart attack, he added. Associate Professor Ti Lian Kah, senior consultant at the department of anaesthesia at National University Hospital, advises patients to alert medical staff to any episodes of awareness during the surgery after the operation, as they might need help to cope with the trauma. Prof Ti said awareness during surgery can lead to anxiety, acute emotional stress or post-traumatic stress disorder, which require professional help and counselling.
MONITORING OXYGEN LEVELS
Doctors now also have machines that measure the exchange of gases within the body. The pulse oximetry is a simple, non-invasive method of measuring the oxygen levels in the blood through a sensor placed on the fingertip. This tells the medical staff if the patient is breathing well enough. Associate Professor Ong Biauw Chi, head and senior consultant at the department of anaesthesiology at Singapore General Hospital, said if more than 95 per cent oxygen saturation is registered, no intervention is required. But if the value drops to below 90 per cent, it means the patient is not receiving enough oxygen and may need to be intubated, given more oxygen or have the airway tube changed, she added. Before the invention of the pulse oximeter in 1972, doctors would check for blueness in the face. A lack of oxygen can turn fatal in less than three minutes. While doctors still look for this physical sign, the machine removes any “element of subjectivity”, Prof Ong said. Another advancement is the capnograph, which monitors the amount of carbon dioxide produced by the body. A normal amount of carbon dioxide from expired air is between 30 and 40 millimetres of mercury (mmHg). If the amount of carbon dioxide exhaled by the patient is lower than that value, it may indicate that an endotracheal tube – inserted through the mouth and down the airway to deliver oxygen to the lungs – may have been inserted into the stomach instead. This can lead to hypoxia, or deficient oxygenation of the blood, which is potentially fatal, said Dr Chong.
CRUCIAL ROLE OF ANAESTHESIOLOGIST
A common misconception is the anaesthesiologist puts people to sleep and then knocks off, said Dr Ho. The reality is he or she performs vital work that ensures the patient’s safety during surgery. The anaesthesiologist helps the patient to breathe, controls his blood pressure and ensures his comfort throughout the duration of the surgery and in the recovery room before the patient is wheeled to the ward. While the anaesthesiologist’s expertise was required only in the operating theatre in the past, his job scope has since expanded, noted Prof Ti. He said anaesthesiologists now take care of patients before their surgery by making sure their pre-existing medical conditions are managed well. They also take care of patients during and after surgery in the intensive care unit and help patients deal with post-operative pain. “This allows a continuum of care for the entire surgical period,” he added. Dr Chong said the ever-vigilant presence of the anaesthesiologist trumps technological advances when it comes to patient safety. He noted: “His job doesn’t end with the last stitch.”
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