Pregnancy brings about significant respiratory changes that affect how anesthesia is managed, particularly regarding lung capacity and oxygenation. As the uterus expands, it pushes the diaphragm upwards, reducing functional residual capacity (FRC) by around 20%. However, tidal volume increases by 30-50%, leading to a rise in minute ventilation. This change creates a state of chronic respiratory alkalosis with lowered arterial carbon dioxide (PaCO2) levels, improving oxygen delivery to the fetus. However, these alterations pose challenges during anesthesia, particularly under general anesthesia or when apneic episodes occur, as oxygen reserves are reduced.
Pregnant patients are more prone to rapid oxygen desaturation during anesthesia due to their lower FRC and higher oxygen consumption. Even with pre-oxygenation, the reduced lung capacity can lead to quicker desaturation during intubation or apnea. This requires careful monitoring to maintain adequate oxygenation throughout procedures. Additionally, increased metabolic demands, especially during labor, can heighten oxygen needs. Epidural analgesia can help reduce these demands, stabilizing oxygen levels during labor. Airway management is also complicated by hormonal changes that cause mucosal edema and anatomical shifts such as breast enlargement, making intubation more difficult. Using specialized equipment, optimizing patient positioning, and avoiding nasotracheal intubation can reduce risks of difficult airway management and hypoxia.
