Somnolence and Hypothermia after Epidurally Administered Morphine for Cesarean section
John Lesko, MD and Michealanne Fritcher MD
Department of Anesthesiology, University of Florida, Gainesville, Florida
We report a case of somnolence and hypothermia after epidural morphine
administration. A 21 year old healthy female at 41 weeks gestational age
presented for a routine trial of vaginal birth after caesarian section (VBAC).
The previous section was performed via a low transverse approach for failure
to progress. The mother presented at 8 cm cervical dilation, -1 cm station,
and 100% effacement. Fetal heart tones initially were non-reassuring with
variable decelerations to 80-90 beats per minute, but decelerations were not
sustained and rebounded spontaneously after no more than 2 minutes. The
obstetrician’s plan was to induce labor with artificial rupture of membranes
and augmentation of labor after institution of an appropriate analgesic
plan. A combined spinal-epidural (CSE) technique was chosen for analgesia.
It was performed without complication using an 18 G tuohy epidural needle,
with a loss-of-resistance to air and water technique, and a 27 G Sprotte
spinal needle placed intrathecally through the epidural needle. Clear
cerebrospinal fluid (CSF) flow was noted, but was lost upon patient
movement. The needle was advanced again and clear CSF flow resumed. 20 mcg
of fentanyl was injected into the subarachnoid space, the spinal needle was
withdrawn, and the epidural catheter easily threaded 5cm into the epidural
space. The catheter was tested with 3 ml 1.5% lidocaine with 1/200,000
epinephrine, without signs of subarachnoid or intravascular injection. It
was connected to an infusion of 0.16% Ropivicaine with 2 mcg/ml fentanyl,
set to deliver 6 ml per hour, with a patient controlled analgesia bolus of 4
ml every ten minutes, for a maximal dose of 30 ml per hour
Excellent analgesia was obtained, however, the fetal condition deteriorated
upon induction of labor with an oxytocin infusion. Artificial rupture of
membranes revealed meconium stained amniotic fluid and the variable
decelerations of the fetal heart rate became more profound. Labor
augmentation was halted and an amnioinfusion was begun, resulting in prompt
fetal recovery. It was then decided to proceed with cesarean section.
The patient was placed on the operating room table with left lateral uterine
displacement and hydrated appropriately. The epidural catheter was again
tested and 25 ml of 3% Chlorprocaine was incrementally administered. A T4
level of anesthesia was achieved. A 3% Chlorprocaine infusion of 12 ml/hr
was begun through the epidural catheter. After delivery of a healthy male
neonate with Apgar scores of 9 and 9 at 1 and 5 minutes, respectively; the
Chlorprocaine infusion was discontinued and 3 mg preservative-free morphine
was administered epidurally for postoperative analgesia. After abdominal
closure, the patient became unresponsive, with slow respirations and a SpO2
90% on room air. Treatment with 400 mcg of naloxone in divided doses
increased responsiveness, respirations, and oxygen saturation. The patient
was taken to the postoperative care unit in stable condition. There, the
oral temperature was 33.8 degrees Celsius. It was also noted she was not
shivering. A convective forced air warming blanket was placed and the
patient made a full recovery after several hours without any further
intervention.
CSE is a popular technique, but concerns remain about the role of the dural
rent that is necessarily present. This rent can theoretically allow the
passage of epidurally administered drugs to the subarachnoid space; the
magnitude of epidural to subarachnoid traverse is not fully understood. In
this presentation, we will explore the potential causes for the above case,
and discuss the role of epidural morphine in causing narcosis and
hypothermia. Pertinent literature will be reviewed, with a specific emphasis
on the increasingly popular CSE technique, and how this technique may have
contributed to our patient’s condition.
