The Minimal Effective Dose of Hyperbaric Spinal Bupivacaine for Successful Reliable Saddle Block for Minor Perianal Surgeries
Description:
Following approval of Research and Ethics Committee of University of Dammam and written
informed consent, 24 American Society of Anesthesiologists physical Status I and II patients,
aged 20-55 years, scheduled for outpatient elective perianal surgery in the lithotomy
position ( hemorrhoidectomy, fistulectomy), were prospectively enrolled in this study.
Patients unwilling to participate, those with contraindications to regional anesthesia,
morbid obesity, bleeding disorders, mental health problems or language barrier, taking
psychotropic or analgesic medication or a known history of allergic reactions to amide local
anesthetics, were excluded from the study.
All patients were fasted for over 6 hours and were premedicated with 0.2 mg/kg oral diazepam
60 min before spinal anesthesia.
In the operating room (OR), an intravenous (IV) 18-20G catheter was placed, and standard
monitoring [electrocardiogram (ECG), heart rate (HR), oxygen saturation (SpO2), and
noninvasive blood pressure (NIBP)] were started.
Under aseptic conditions, dural puncture was performed by staff-grade anesthesiologists,
using a standard midline approach in the sitting position at the L3-L4 or L4-L5
intervertebral space, using a 25-gauge Whitacre needle with its orifice directed caudal. A
predetermined small dose of hyperbaric bupivacaine (Marcaine Spinal Heavy; Astra Zeneca,
Lund, Sweden) which was prepared in1 mL tuberculin syringe was injected. All patients
remained in the sitting position for 10 min. the patient was asked if he/she perceived any
change in motor power.
If not, the patient was allowed to position him/herself without aid for surgery in lithotomy
position. Immediately before surgery, the level of sensory block was tested using a long
surgical toothless clamp gently applied radially, starting from the anal orifice, in
different diagonal directions.
Motor block was tested by modified Bromage scale (0 = no motor block, 1 = able to flex ankle
and bend knees, 2 = able to flex ankle, and 3 = full motor block) .
A successful block was defined as one that was sufficient to proceed with the surgery without
any supplementation (intravenous analgesic, local anesthetic infiltration or general
anesthesia).
The dose of bupivacaine given to each patient was determined by the response of the
previously tested patient using a modified Dixon’s up-and-down method (using 0.5 mg as a step
size) (16).
The first patient was tested at a dose 1.5 mg bupivacaine, if patient responded with failed
block then the next patient received an increment of 0.5 mg bupivacaine, if patient responded
with successful block, then the next patient received a decrement of 0.5 mg bupivacaine.
The research continued until the investigators obtained seven crossover midpoints. The
initial starting dose of 1.5 mg hyperbaric bupivacaine of the first patient was selected from
the findings of Wassef R et al. (13) who demonstrated adequate anesthesia for short perianal
surgery with the use of 1.5 mg spinal hyperbaric bupivacaine. Bupivacaine was prepared
immediately before injection by an anesthesiologist blinded to the study methodology and
admin¬istered by a second blinded anesthesiologist.
Block assessment and clini-cal follow-up of the patients was also per¬formed by a third
blinded anesthesiologist.
The following data were recorded; Patient demographics, duration of anesthesia and surgery,
level of sensory and motor block immediately before surgery, at the end of surgery, and every
30 minutes until resolution of the block. NIBP and HR were documented every 5 minutes in the
OR and PACU. Also Time to ambulation, first voiding time and time to home discharge were
recorded. Patient’s and surgeon’s satisfactions were evaluated with a 4-point score (0=poor,
1=good, 2=very good, 3= excellent). Patients were followed by phone call to note down any
possible postoperative complication (postdural puncture headache, TNS or backache) at day 1
postoperatively and 10 days later. The time of dural puncture was used as the primary
starting point of assessment.
Condition:
Perianal Surgery
Treatment:
Dixon’s up-and-down method
Start Date:
January 2014
Sponsor:
Dammam University
For More Information:
https://clinicaltrials.gov/show/NCT02299167