The Time Required to Remain Sitting After Spinal Anesthesia With Fentanyl for 50% of Patients to Not Experience Hypotension.
Description:
Up down sequential analysis is a method developed by Dixon to determine the point where 50%
of people will have a positive response and 50% will have a negative response to an
intervention. It is a very powerful technique that has been used to determine the median
effective dose (referred to as ED50) of many medications. Using this method, patient number 1
is given a certain amount of the intervention being studied. If patient 1 has the desired
response, patient 2 in the series is given less of the intervention, and if patient 1 does
not have the desired response, patient 2 is given more of the intervention. This is repeated
through a series of patients until the dose where there is a 50% response rate is determined.
In this study, the investigators wish to use up down sequential analysis to determine the
time period a patient should remain seated after intrathecal injection of hyperbaric
medication that result in a 50% rate of hypotension, what we will call the ET50 (Estimated
Time for 50% of patients to have hypotension). The investigators would like to explore this
relationship with 2 clinically used doses of hyperbaric bupivicaine.
Patients scheduled for cesarean delivery arrive in the birthing centre 1-2 The patients will
be given the same anesthetic care routinely used in the birthing centre, except that the
investigators will control the time that the patient remains seated after injection of
intrathecal hyperbaric bupivacaine. The baseline blood pressure and heart rate will be
recorded. After intravenous access is obtained, an infusion of normal saline will be
commenced at a rate of 100 cc per hour. The patient will be brought to the operating room,
and the standard monitors will be placed. The intravenous fluid will be administered at a
rate of 500 ml per hour for one hour. The patient will be placed in a sitting position. The
landmarks of the spinal canal will be identified with an ultrasound, then using sterile
technique, an epidural catheter will be placed in the L2-L3 spinal interspace, and then a 27
gauge whitacre needle will be used to access the intrathecal space at the L4-L5 spinal
interspace. After identification of the intrathecal space, hyperbaric bupivacaine will be
injected over 30 seconds. The patient will then be left in the sitting position for the
predetermined time. The patient will then be placed supine, with a 15 degree wedge under the
right hip. The noninvasive blood pressure will be set to measure the blood pressure every
minute. Hypotension will be defined as a drop in blood pressure to more than 20% of the
patient’s preoperative blood pressure. The medications used for treatment of hypotension will
be left to the discretion of the treating anesthesiologist. The height of the anesthetic
blockade will be measured bilaterally with ice at 1, 5, 10, 15, and 20 minutes after the
patient has been placed supine. If the block has not reached T6 by 20 minutes after the
patient has assumed the supine position, or if the patient experiences any pain during the
cesarean delivery, 5 ml of 2% lidocaine will be administered through the epidural catheter.
If this does not suitably manage the pain, the treating anesthesiologist will be allowed to
manage the pain as they see fit.
Determination of the time in the sitting position :
The study patient will be considered a success if the duration of time in the sitting
position results in no pre-delivery hypotension. The study patient will be considered a
failure if the time spent in the sitting position results in pre-delivery hypotension. A
patient will be considered an indeterminate result if the ice test fails to show a block
reaching T6 by 15 minutes. A patient following a success will be left in the sitting position
for 15 seconds less than the preceding patient, and the patient following a failure will be
left in the sitting position for 15 seconds more than the preceding patient. A patient
following an indeterminate result will remain in the sitting position for the same time as
the preceding patient. The first patient in the series will be left in the sitting position
for two minutes and half for the 1.5 ml bupivacaine and 6 minutes and half for the 2 ml
bupivacaine after the injection of the intrathecal medication.
Dosage determination and blinding:
To see if ET50 is dependent on the dosage of medication given, we will determine the ET50 for
2 doses of hyperbaric bupivicaine with 15 micrograms of fentanyl. Both of the doses we will
study are used routinely in clinical practice. Using a computerized randomization schedule,
we will randomly assign patients to receive either 2 ml or 1.5 ml of 0.75% hyperbaric
bupivacaine, for a total of 15 mg or 12.5 mg of bupivacaine respectively.
Recorded data:
The investigators will record the demographic data of the patient, including height, weight,
age, gravidity, parity, weeks gestation, and reason for the cesarean delivery. The
investigators will record the medical history of the patient, and medications that the
patient takes. The investigators will record the admission heart rate, blood pressure and
saturation. The investigators will record the time that the intrathecal medication is
injected, and the time that that the patient remains seated after the spinal anesthesia has
been commenced. The investigators will record the level of anesthetic blockade at
1,5,10,15,and 20 minutes after the patient has been placed supine. The investigators will
record the blood pressure, and heart rate every minute after the patient has been placed
supine until the baby has been delivered. The investigators will record any medications used
to treat blood pressure before the baby has been born, and any medications used to treat
breakthrough pain. The investigators will record the birth time, the baby gender, weight,
apgar, and umbilical cord pH.
Condition:
Hypotension
Treatment:
Bupivacaine with 15 micrograms of fentanyl
Start Date:
July 2013
Sponsor:
McGill University Health Centre/Research Institute of the McGill University Health Centre
For More Information:
https://clinicaltrials.gov/show/NCT01896960