Use of sedatives and analgesics
When carrying out plastic surgery under local anesthesia or no anesthesia, sedatives, hypnotics, antianxiety agent, and analgesics, etc. are used to alleviate patients’ anxiety and pain. Drugs are selected based on the patient’s age, degree of anxiety, history, obesity, type of duration of surgery/procedure and degree of pain, etc.
Sedatives, hypnotics and antianxiety drugs
Sedative-hypnotics reduce the patient’s anxiety during procedure and induces temporary amnesia which the patient can quickly recover from once the drug is discontinued. When patients are appropriately sedated, they can consciously express they are comfortable and their respiratory tract reflexes and stable voluntary respiration are maintained. Also, a level of consciousness is maintained to allow cooperation with the medical staff during the procedure.
Benzodiazepines, barbiturates, propofol, and ketamine are among some of the drugs used for this purpose and midazolam and propofol are the most widely used. Midazolam has potent amnesic, anxiolytic and sedative effects. It is water-soluble and does not cause pain during injection. It has an elimination half-life of 1.7-2.6 hours in healthy adults which is shorter than that of diazepam. However, continuous IV infusion or use in renal impaired patients can lengthen the elimination half-life. Its rapid onset of action (within 2-2.5 minutes of administration) allows accumulative effect when given in short repetitions but can cause complications such as impaired respiration, etc. In rare cases, (<1%), midazolam can cause paradoxical reaction of causing excitement and anxiety. Administering a low dose (0.1~0.2mg) of flumazenil, benzodiazepines antagonist, can bring recovery.
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Propofol causes pain during IV injection. It takes effect in 45-60 seconds and has a short duration of action (1-8 minutes) due to redistribution. This allows faster recovery of cognitive abilities. It is particularly useful as an anesthetic in the outpatient settings due to its antiemetic effect and minimal residual sedation and drowsiness. On the other hand, it has little analgesic action and can cause hypotension dose-dependently by reducing systemic vascular resistance, myocardial contractility and cardiac preload. Caution should be given as it can also cause apnea by inhibiting hypoxic ventilation and hypercapnic reaction at a subhypnotic dose.
Ketamine maintains hemodynamic stability through its sympatheticomimetic action and has the advantage of simultaneous sedation and analgesia. However, it causes phychomimetic effects in adults and should be used in combination with midazolam or propofol, rather than alone. Combination of propofol and ketamine reduces phychomimetic effects and the need of opioids as well as counteracts propofol’s cardiovascular inhibition and respiratory impairment.
-To be continued-
