Labor Analgeisa
When a patient is in labor, the anesthesiologist has the role of pain relief, which can prevent potential negative maternal and fetal consequences of increased sympathetic activation. Neuraxial analgesia has proven to be most effective and is the most common form of pain relief for laboring women. Of neuraxial techniques, generally speaking epidurals are most commonly used for vaginal deliveries and spinals are used for cesarean sections. During labor, pain originates from different spinal levels depending on the stage of labor.
The first stage of labor begins at the onset of regular painful contracts and ends when the cervix is dilated to 10cm. Pain during this stage of labor originates from the uterine contraction which has innervation from T10-L1. The pain is vague, diffuse, and poorly localized as it is transmitted through visceral afferent nerves. Besides an epidural, other choices of analgesia during this stage include paracervical, paravertebral, and lumbar sympathetic blocks.
The second stage of labor begins when the cervix is completely dilated and ends with the baby being delivered. This pain is somatic in nature, due to the stretching and tearing of pelvic ligaments and muscles. In addition to the visceral afferent nerves being stimulated from the first stage of labor, there is pain transmitted from the pudendal nerves at S2, S3, and S4.
Before performing an intervention for pain relief, a provider should perform a history and physical that focuses on medical conditions, labs (ie. platelets, coagulation studies), airway/cardiac/pulmonary/spine exam. Vital signs for the mother and fetal heart rate monitoring should occur during the intervention. Hydration with intravenous fluids can help mitigate associated hypotension with neuraxial interventions, using caution regarding patients with preeclampsia and cardiac disease.
Although you may hear “epidurals” and “spinals” used interchangeably, they are vastly different ways to administer neuraxial analgesia. The biggest differences between the two is the onset, density, and duration of the nerve blocks. An epidural involves places a thin catheter in the epidural space which is connected to a pump that continuously infuses local anesthetic (ie. Bupivacaine/Ropivacaine). After the initial bolus, it has a gradual onset over the course of 10 to 15 minutes. The motor blockade tends to be mild with epidurals with most women still able to walk or move their legs with assistance. Spinals are a one time injection that provide analgesia for a few hours. The onset occurs over 5 minutes with the sudden loss of sensation to sharp pain and temperature and inability to move their legs. Both techniques can be used for labor pains and cesarean deliveries. Opioids can be added to both to increase the density of the block. And for labor analgesia, both are inserted around the L2 to L4 spinal level.
