Anesthetic Techniques: General, Regional and Monitored Anesthesia Care
Technique questions test selection and dose accuracy across general anaesthesia, central neuraxial and peripheral blocks, and monitored anaesthesia care (MAC), including each one's failure modes.
General anaesthesia
- Balanced technique: hypnosis (volatile or propofol TCI), analgesia (opioid or regional), muscle relaxation, plus depth and neuromuscular monitoring.
- Target train-of-four count 1–2 intraoperatively and a ratio above 0.9 before extubation.
- Awareness risk rises with TIVA, obstetric and cardiac cases; use processed EEG when a relaxant is used throughout.
Regional
- Spinal: hyperbaric bupivacaine 0.5%, 2.5–3 mL at L3–L4; block height depends on baricity, volume and patient position.
- Caesarean section: 10–12 mg hyperbaric bupivacaine with fentanyl 15–25 µg; prevent hypotension with a phenylephrine infusion rather than large crystalloid co-loading.
- Epidural test dose: 3 mL lidocaine 1.5% with 1:200,000 adrenaline; never give an adrenaline-containing solution intrathecally.
Monitored anaesthesia care
- MAC is deliberate light sedation with the anaesthetist present and the ASA qualifying criteria met. It is not the same as care during a general anaesthetic, and conversion to GA must be documented.
Worked example
A 30-year-old for elective caesarean delivery: spinal with 11 mg hyperbaric bupivacaine plus 20 µg fentanyl, block to T4, phenylephrine infusion 25–50 µg/min titrated to keep systolic pressure above 90% of baseline, left uterine displacement, vasopressor drawn up before incision.
Traps
Confusing MAC (monitored anaesthesia care) with MAC (minimum alveolar concentration); starting surgery before checking block height; attributing post-spinal hypotension to haemorrhage without considering sympathectomy.