A Prospective Study to Establish a Correlation Between Infusion Rate of Propofol and Bispectral Index (BIS) in Patients Receiving Total Intravenous Anesthesia (TIVA)
Pre-anesthetic Management: This research will be initiated after receiving an approval from
the Institution Review Board, and an informed written consent will be obtained from each
patient. Forty patients in the age range 18-65 years and presenting for elective orthopedic
or gynecological procedures will be recruited. Both male and female patients will be
considered. Only patients with American Society of Anesthesiologists (ASA) physical status
I, II and III will be included. Patients who are pregnant and those with uncontrolled
hypertension with BP above 180/100, unstable angina, chronic obstructive lung disease
requiring oxygen therapy at home, and end-stage liver and kidney diseases will be excluded.
In addition, orthopedic surgery that needs the patient in prone position will not be
eligible for this investigation. Patients who have a medication allergy to propofol and
food allergy to egg and soy, since egg lecithin and soy milk are constituents of propofol
preparation, will be excluded. In order to have a complete data collection, only surgical
procedures scheduled to last more than three hours will be considered for this study.
Anesthetic Management: Routine anesthetic care, such as intravenous line placement and
American Society of Anesthesiologists' standard monitoring, will be applied to all patients.
In addition, a non-invasive Bispectral Index (BIS) sensor will be placed on patient's
forehead and connected to its monitor. Midazolam (25mcg/kg) and fentanyl (1mcg/kg) will be
administered to establish preanesthetic sedation and analgesia, respectively. Lidocaine 40mg
will be given to attenuate propofol-induced injection pain. Thereafter, Total Intravenous
Anesthesia (TIVA) will be induced with propofol (2mg/kg), and tracheal intubation
facilitated with a neuromuscular blocking agent chosen by the attending anesthesiologist.
The skeletal muscle relaxation will be maintained as needed for the surgical procedure. The
TIVA will be maintained with propofol infusion, for approximately half-hour, at
160mcg/kg/min with minor adjustment, as needed, to maintain patient's vital signs within ±
20% of the baseline. Once a steady state is established, propofol infusion rate will be
reduced to 140mcg/kg/min and maintained for approximately 15-30 min, following which the
infusion rate will be increased to 180mcg/kg/min and maintained for the same period of time.
Thereafter, the propofol infusion rate will be returned to 160mcg/kg/min. This exercise
will be repeated at 120mcg/kg/min and 200mcg/kg/min if patient's vital signs permit. In
addition, remifentanil at an infusion rate of 0.02 - 0.2mcg/kg/min will be administered to
provide surgical analgesia during the general anesthetic period. The infusion rate of
remifentanil will be tailored to the demands of the surgical stimulation. During the study
period, the attending anesthesiologist will have the option to deviate from the study
protocol and adjust the propofol infusion rate, as needed, to maintain patient's vital signs
within ± 20% of the baseline if such a need arises. An independent observer will
continuously monitor the BIS values at all time frames. Following the study period needed
to collect the required data, the attending anesthesiologist will have the option to
continue general anesthesia with either TIVA or with the traditional inhalational
anesthetic. The reversal of the neuromuscular blockade and subsequent tracheal extubation,
at the conclusion of surgery, will be performed using the customary criteria employed in
anesthetic practice. In addition, the routine protocols used for surgical infection
prevention and attenuation of postoperative pain and vomiting will be followed.
Observational Model: Cohort, Time Perspective: Prospective
BIS response to varying TIVA dosages
Correlation between various infusion rates of propofol administered during TIVA and BIS values during the first 3 hours of the operative procedure
Rex Ponnudurai, MD
United States: Food and Drug Administration
|University Hospital||Newark, New Jersey 07103|