Anestesia para emergencias en obstetricia

Abstract

Pregnancy induces changes in almost every body system, pushing their reserves to the limit. There is a decrease in systemic vascular resistance, a progressive increase in blood volume, heart rate and myocardial size, resulting in an increased cardiac output. It reduces the functional residual capacity and increases the tidal volume. Oxygen consumption increases, leading to a decrease in oxygen reserves and increased risk of hypoxemia under hypoventilation or apnea (more frequent due to difficult airway management as a result of edema). Important changes are also observed at the hematological, renal and intestinal levels. Uterine-placental blood flow increases progressively during pregnancy, elevating the risk of massive hemorrhage. When intrauterine resuscitation does not resolve acute fetal distress, urgent cesarean section should be performed. Neuraxial over general anesthesia is recommended. In emergency situations, general anesthesia or “Rapid Sequence Spinal Anesthesia” is suggested as an alternative. The requirements of both, hypnotics and inhalation agents, decrease during pregnancy. Obstetric hemorrhage may be the result of bleeding from placenta or a consequence of trauma to the genital tract during delivery. The most severe cases present hypovolemic shock. Along with controlling the source of bleeding, the treatment goals are: treat hypovolemia and acute trauma coagulopathy, preserve oxygen transport capacity, repair the endothelium and prevent dilutional coagulopathy. Management of placenta accreta must be multidisciplinary. Preoperative diagnosis is essential for adequate preparation. Combined spinal-epidural technique is recommended. When hysterectomy becomes necessary, conversion to general anesthesia should be considered. Amniotic fluid embolism in its early stage produces right ventricular dysfunction due to acute pulmonary hypertension and, in its late stage, left ventricular dysfunction. In 40% of cases, multifactorial coagulopathy is observed. The diagnostic criteria are: 1) hypotension or cardiac arrest, hypoxia and coagulopathy; 2) during labor, caesarean section, uterine curettage or in the first 30 minutes postpartum; 3) in the absence of another diagnosis that explains the symptoms. Treatment is supportive, besides termination of pregnancy. Resuscitation during pregnancy must be led by a professional who understands the complexities of the situation. Maternal well-being is the best predictor of fetal well-being. A perimortem cesarean may become necessary.