General Anaesthesia in Obstetrics
Highlights
- Airway-related maternal mortality during obstetric GA is approximately 2.3 per 100,000 GAs for CS compared with one in 180,000 GAs for the general population; mortality after failed intubation is 1% in parturients (View Highlight)
- Because of the upward displacement of the diaphragm by the uterus and increase in transverse diameter of the thorax, functional residual capacity (FRC) is reduced 20% by term. Minute ventilation (MV) is increased by 50%. The combination of decreased FRC and increased MV accounts for rapid uptake of inhalational anaesthetic agents (View Highlight)
- Increased maternal resting metabolic rate and the increased metabolic demands of the fetoplacental unit cause an increase of 60% in oxygen consumption (View Highlight)
- Cardiac output increases by up to 50% at term, resulting from an increase in HR (10–20 beats min−1) and stroke volume (30–40%). Thus, induction of anaesthesia with i.v. anaesthetic agents is faster. (View Highlight)
- Progesterone also decreases the tone of the LOS (View Highlight)
- None of the currently used anaesthetic agents, including propofol, opioids, neuromuscular blocking agents (NMBAs), and local anaesthetics, at standard concentrations, have been shown to have teratogenic effects on the fetus at any gestational age (View Highlight)
- Even in cases of strongly suspected PAS, no association has been found between the degree of placental invasion and massive blood loss or large-volume transfusion (View Highlight)
- Changes in the patient's mental status (especially progression to unarousable) are likely to correlate with a reduced ability to protect her airway and should be triggers to consider induction of GA (View Highlight)
- Unlike during operative delivery, where uterine relaxation is undesirable, it is a requirement during many fetal surgeries. Uterine relaxation during these cases allows better surgical exposure, maximises maternal blood flow through the uterus, and reduces the chances of uteroplacental separation (View Highlight)
- Uterine relaxation may be achieved with a combination of agents (nitroglycerine, indomethacin and magnesium) with volatile agents acting as the bedrock of the effort (View Highlight)