Premedication
- Is the administration of drugs prior to an anaesthetic
- Has three potentially useful effects:
- Anxiolysis
- Reduced bronchial secretions
- Analgesia
- Anxiolysis if needed can be achieved with either benzodiazepines or
phenothiazines
- Opiate analgesics also have useful sedative properties
- Reduction of sections is not as important today with modern
inhalational agents
- Ether was notorious for stimulating bronchial secretions
- If required secretions can be reduced with hyoscine
- Also reduce salivation and prevents bradycardia
- Analgesia best achieved with strong opiates
Principles of premedication
- Anxiolysis
- Analgesia
- Amnesia
- Antiemetic
- Antacid
- Anti-autonomic
- Adjuncts
Drugs used
- Anxiolysis - benzodiazepines, phenothiazines
- Analgesia - opiates, non-steroids anti-inflammatories
- Amnesia - benzodiazepines, anticholinergics
- Antiemetic - anticholinergics, antihistamines, 5HT antagonist
- Antacid - Alginates, proton pump inhibitors
- Anti-autonomic - anticholinergics, beta-blockers
- Adjuncts - Bronchodilators, steroids
Induction
- Induction agents are usually administered intravenously
- Distributed to organs with a high blood flow (e.g. brain)
- Highly lipid soluble and rapidly cross blood brain barrier
- With falling blood levels they are rapidly redistributed from brain
- Have rapid onset and without maintenance would have rapid recovery
Thiopentone
- Short-acting barbiturate
- First used at Pearl Harbour in 1942
- Depresses myocardium
- In hypovolaemic patient can induce profound hypotension
Propofol
- Has very short half-life
- Can cause hypotension
- Can also be used for maintenance of anaesthesia as an infusion
Rapid-sequence induction
- Rapid induction of anaesthesia
- Cricoid pressures used to reduce risk of aspiration
- Pressure released once tracheal intubation with a cuffed tube has
been achieved
- Achieved by the use of thiopentone and suxamethonium
- Used for patients with:
- None fasted
- History of gastro-oesophageal reflux
- Emergency trauma patients
- Intestinal obstruction
- Pregnancy
- Intra-abdominal pathology that will delay gastric emptying
Bibliography
Cook D R. Can succinylcholine be abandoned? Anesth Analg
2000; 90 (Suppl 5): S24-28
Smith A F, Pittaway A J. Premedication for anxiety in adult
day surgery. Cochrane Database Syst Rev 2003; CD002192 |