Ketamine is a medication used in various medical settings, primarily recognized as a dissociative anesthetic. Approved by the United States Food and Drug Administration (FDA) for general anesthesia, it induces a state of unconsciousness and pain relief during medical procedures. Ketamine has specific applications in anesthesia beyond its common associations. This includes its use in obstetrics, where it is a valuable, though not routine, tool in particular circumstances.
Clinical Use in Obstetric Anesthesia
Ketamine is not the first choice for routine or scheduled cesarean sections. Its use in obstetric anesthesia is reserved for specific, urgent situations. It is a valuable option in emergency cesarean sections, especially when the mother experiences hemodynamic instability, such as severe bleeding or very low blood pressure. The medication supports the mother’s cardiovascular system in these moments.
The drug is also considered for patients with severe asthma due to its bronchodilator properties, relaxing the airways. Ketamine may also be selected when regional anesthesia, like a spinal or epidural block, is medically contraindicated or unsuccessful. It can also serve as a rescue analgesic if neuraxial anesthesia is insufficient during a cesarean delivery.
Effects on the Mother
Ketamine offers anesthetic benefits for pregnant patients. It provides analgesia and anesthesia while maintaining or increasing blood pressure and heart rate. This characteristic is advantageous in hemorrhage or hypovolemia, where other anesthetics might cause a drop in blood pressure.
Despite these benefits, ketamine can cause side effects. Patients may experience emergence reactions upon waking, such as vivid dreams, hallucinations, or delirium. These psychological effects are often managed with other medications. The increase in heart rate and blood pressure, while helpful in some cases, can be problematic for mothers with pre-existing conditions like preeclampsia or hypertension. Nausea, vomiting, and jerky muscle movements are also noted.
Impact on the Fetus and Newborn
Ketamine readily crosses the placental barrier. In utero, the fetus may experience changes in heart rate variability. Ketamine can also influence uterine tone and the frequency and strength of contractions. However, its ability to maintain maternal blood pressure can support uterine blood flow, benefiting the fetus, particularly in maternal hypotension.
Immediately after delivery, newborns may exhibit transient effects such as increased muscle tone (hypertonus) or lower Apgar scores. These effects are typically dose-dependent; doses below 2 mg/kg usually do not cause significant neonatal depression, while higher doses (≥ 2 mg/kg) can lead to more pronounced effects. While Apgar scores might be lower at one minute, they generally improve by five minutes post-delivery.
Respiratory depression is another temporary effect, especially with higher doses or opioid co-administration. Limited human data exists on long-term neurodevelopmental outcomes from a single anesthetic dose, but it is generally considered safe when used appropriately. Animal studies, however, have suggested potential neurotoxicity to the developing brain with prolonged or high-dose exposure.
Ketamine Compared to Other Anesthetics
When considering anesthesia for a cesarean section, regional techniques, such as spinal or epidural blocks, are generally preferred over general anesthesia. Regional methods carry a lower risk of maternal aspiration and avoid the direct depressive effects of general anesthetics on the newborn. Ketamine, however, offers a rapid onset of action (within minutes intravenously), often faster than establishing a regional block.
A key difference lies in their effects on maternal blood pressure; ketamine supports or even increases it, while regional anesthesia can cause a drop. While regional blocks have their own potential complications, such as headaches or nerve irritation, ketamine’s side effects include emergence reactions. Ketamine can also supplement an inadequate regional block or aid in postoperative pain management.
Comparing ketamine to other general anesthetic agents, such as propofol, reveals distinctions. Ketamine helps maintain cardiovascular stability by increasing blood pressure and heart rate, contrasting with propofol, a common induction agent that can cause hypotension. While propofol is associated with a smoother emergence, ketamine recovery can involve the aforementioned psychological effects. Ketamine’s properties allow it to be safely used for inducing general anesthesia, potentially enabling 100% oxygen administration until newborn delivery, a consideration in emergency obstetric scenarios.