Does Maternal Fever During Labor Analgesia Has Any Relationship With Maternal Ventilation?

Epidural techniques offer the advantage of being able to titrate the level, density, and duration of the blockade through the use of a catheter and are associated with relative maternal hemodynamic stability. One of the disadvantages, however, include a raise in maternal temperature that is attributed to labor epidural technique. This study will assess if decreased maternal ventilation following induction of labor analgesia causes a raise in temperature.

Fever in labor complicates up to one-third of deliveries. The etiologies of intrapartum fever are diverse and include maternal chorioamnionitis, and other infections. In addition, epidural analgesia used for pain relief in labor is associated with mild maternal temperature increase and overt fever. Originally dismissed by obstetric anesthesiologists as a clinical curiosity of little consequence, epidural-associated hyperthermia may lead to significant maternal as well as fetal or neonatal adverse effects. Observational investigations performed 2 decades ago demonstrated a gradual increase in temperature in laboring parturients with epidural analgesia not see in those electing systemic opioid analgesia or no analgesia. The epidural group showed an average increase in temperature of approximately 1 degree centigrade over 7 hours whereas temperatures in non-epidural group remained constant. No evidence of clinical infection was reported in any of the women. Many studies confirmed these raises in temperature in epidural group compared to no epidural group during labor and delivery.

Several mechanisms have been postulated with no study reaching a conclusion. The mechanisms suggested include imbalance between heat production and heat dissipation, effect of opioid on interleukin-2, markers of inflammation induced by epidural analgesia, etc. Our study aims at the first mechanism. It may be a physiological process that leads to an imbalance between heat production and heat dissipation. Labor is a hyper metabolic state and increased heat production is dissipated via increased ventilation that is associated with labor pains with no epidural pain relief. It is conceivable that laboring women with pain relief subsequent to epidural analgesia, a decrease in ventilations may occur leading to decreased heat dissipation.

Eligibility Criteria:
Inclusion Criteria:

1. Parturient with no major co-morbidities
2. Singleton, vertex gestation at term (38-42 weeks)
3. Less than 5 cm dilation
4. Intact fetal membranes or rupture for \< 6 hrs.
5. Desire to have an epidural technique for labor analgesia

Exclusion Criteria:

1. Current or historical evidence of clinically significant disease or condition, including diseases of pregnancy (i.e preeclampsia, gestational diabetes)
2. Any contraindication to the administration of an epidural technique
3. History of hypersensitivity or idiosyncratic reaction to local anesthetic or opioid medications
4. Current or historical evidence of a disease which may result in the risk of a cesarean delivery (i.e. vaginal birth after cesarean section, history of uterine rupture)
5. Evidence of anticipated fetal anomalies
6. Signs or symptoms consistent with an infection or sepsis; baseline temperature \< 37 degrees Celsius, or 99 degrees Fahrenheit.