Intravenous Ketamine for Pain Control During First Trimester Surgical Abortion

Rationale:

At present, the gold standard for pain control during first trimester abortion is the combination of a paracervical block with moderate intravenous (IV) sedation. Paracervical blocks are routinely done with lidocaine, with or without epinephrine or vasopressin. Moderate sedation is commonly achieved using fentanyl 50-100ug IV and midazolam 1-2mg IV. The issue with the use of IV opioids for sedation is the need for continuous cardio-respiratory monitoring, due to the risk of cardio-respiratory depression or collapse. This therefore limits the ability of some centers to provide the best form of pain control for their participants undergoing first trimester surgical abortion. For instance, our center currently uses a paracervical block plus a combination of oral medications (morphine and lorazepam), which has been found to be inferior to a paracervical block plus IV sedation. All participants without contraindications to NSAIDs are pre-medicated with naproxen as recommended.2 The investigators also have access to nitrous oxide/oxygen 50:50 (Entonox) to use as an adjunct, however this has not been found to significantly improve procedural or post-operative pain.

In the past, ketamine was used for pain control during first trimester abortion. Ketamine is a dissociative agent and does not carry the same risk of cardio-respiratory depression as intravenous opioids. Ketamine was felt to be ideal for first trimester surgical abortion -as the medication has uterotonic properties, which could result in less blood loss. Doses of 0.5mg/kg IV were typically used. However, the use of ketamine for first trimester surgical abortion decreased dramatically after the 1970-1980's due to reports of adverse events including emergence phenomena (nightmares), nausea, and vomiting. In fact, only one study published during this time did not find negative emergence phenomena in participants exposed to ketamine. More recently, a systematic review concluded that ketamine was an inferior agent when compared to propofol for pain control during first trimester surgical abortion. However, propofol, a general anesthetic requiring continuous cardio-respiratory monitoring, should not be placed in the same anesthetic category as ketamine. Furthermore, propofol is only available in a limited number of settings offering first trimester surgical abortion.

Over the last 10 to 15 years, ketamine has become an increasingly commonly used dissociative agent for procedural sedation in the emergency department. The benefits of its use include the simultaneous provision of both sedation and analgesia, while maintaining airway reflexes and respiratory drive. Intravenous ketamine use in the emergency department has been shown to yield high success rates (94% to 100%). In addition, of all the drugs commonly used in this setting, ketamine has one of the highest safety profiles and lowest rates of complications.

The investigators are interested in re-visiting whether ketamine would be an appropriate choice of anesthetic for first trimester surgical abortion. If ketamine is found to be superior to IV fentanyl, it would potentially increase access to optimal pain control in settings where continuous cardio-respiratory monitoring is not available. Furthermore, in the current era of opioid misuse, it is important that providers look for alternative forms of pain management when appropriate. In fact, the Society for Family Planning recently put out a call to action for more research on alternative options to control pain short of moderate or deep sedation.