Ancillary drugs are drugs that are used in conjunction with general anaesthetics. Although termed as ancillary drugs, these drugs play an integral role in every surgical operation. Ancillary drugs serve multiple functions in surgery and can enhance the surgical procedure and patient safety. To most patients, the prospect of an impending surgical operation leads to preoperative anxiety, especially given that the outcome of the surgery is unpredictable (Valenzuela Millan et al. 2010). Therefore, in order to reduce anxiety, benzodiazepines such as diazepam and lorazepam are commonly used (Fragen et al. 1976).
Benzodiazepines can be given orally or intramuscularly to the patients a few hours before the operation in order to relieve anxiety, promote sedation and amnesia. Benzodiazepines act on a positive regulatory site on the GABAA receptor, a ligand-gated ion channel, enhancing the activity of GABA neurotransmitter when it binds to the GABAA receptor. Subsequently, this leads to greater influx of chloride ions into the nerve cell, lowering the electrical potential of the cell and therefore having an overall inhibitory effect on the central nervous system, leading to anxiolysis, amnesia and sedation (Rang et al.2011).
In addition to benzodiazepines, opioids can be administered to enhance sedation and relief pain. With respect to the case study, benzodiazepines might have minor side effects on pregnant mothers. Some research studies found an increase in risk of malformation and cleft palate in newborns due to benzodiazepines (Dolovich et al. 1998). If used shortly before delivery, newborns might suffer from floppy infant syndrome, where the infant experiences lethargy (ACOG 2008).
Ancillary drugs are also used to reduce the risk of aspiration during surgery. Because of the inhibitory actions of general anaesthetics and drugs used to induce short-term paralysis for intubation, many of our protective reflexes such as the swallowing reflex and coughing reflex are compromised, therefore resulting in a greater risk of aspiration (Sundman et al. 2001). Aspiration of stomach content due to reflux is especially dangerous because stomach contents are highly acidic. Therefore, before surgery, fasting is often recommended.
On top of that, metoclopramide and non-particulate antacids are administered to accelerate stomach emptying and neutralize stomach acid respectively (Adelhoj et al. 1984). Histamine H2 receptor antagonists can also be prescribed to decrease secretion of gastric acid by parietal cells. To prevent aspiration of excess pharyngeal secretions, muscarinic receptor antagonists such as atropine and hyoscine are used to inhibit parasympathetic pathways. As a result, there is a reduction of the production of saliva and mucous in the gastrointestinal tract, thus reducing the risk of aspiration.
From a surgical point of view, blood pressure is an important factor to be taken into account while administering ancillary drugs. Excessive hypotension is commonly a result of the inhibitory actions of the anaesthetics on the sympathetic nervous system. Excessive hypotension is a potentially fatal complication because it is indicative of lowered cardiac output, subsequently cerebral anaemia and possibly death (Morris et al. 2005). To counter this, atropine is sometimes used as a muscarinic receptor antagonist, therefore increasing heart rate and conduction velocity.
On the other hand, in recent years, the technique of controlled hypotension is often employed because it allows the surgeons to see the surgical area more clearly and therefore perform the operation more accurately and efficiently (Eckenhoff 1978). Hypotensive agents such as hydralazine and sodium nitroprusside are used for controlled reduction of blood pressure (WHO 1989). Although there is a rough guideline to the administration of ancillary drugs, in reality, the complex interplay of multiple factors demands flexibility and expertise in the administration of ancillary drugs.
Because the reaction of each patient to the anaesthetic and surgical operation is different, it is therefore crucial for the anaesthetist to constantly monitor the vital signs of the patient throughout the procedure and modify the use of ancillary drugs in order to prevent any further complications. From pre-operation to post-operation, the patient must be assessed holistically by taking into account any conditions and circumstances to ensure that the benefit arising from the use of ancillary drugs outweighs the possible side effects.