Minimal Effective Dose of Hyperbaric Spinal Bupivacaine for Saddle Block
Condition: Perianal Surgery
Study type: Interventional
Phase: Phase 3

Summary: 
      The optimal anesthetic technique would provide excellent operating conditions, rapid
      recovery, early discharge, no postoperative side effects, and high patient's satisfaction. In
      addition to increasing the quality and decreasing the costs of the anesthetic services (1).
      Selective spinal anesthesia (SSA) -spinal block with minimal effective doses for a specific
      type of surgery - has become very popular technique) 2(for some orthopedic and gynecological
      surgeries [3-9].

      Saddle anesthesia is a SSA directs a small bolus of hyperbaric local anesthetic, towards
      S4-S5 and coccygeal nerve roots (11), and is commonly utilized for perianal surgeries
      (11-14). Hyperbaric bupivacaine has been safely, replaced hyperbaric Lidocaine for saddle
      block (11, 12).

      Although Saddle blocks at different low doses of hyperbaric bupivacaine (1.5- 4 mg) have been
      used previously for mi¬nor perianal surgeries (11, 13, 14), the optimal effective dose has
      yet to be determined.

      The objective of this study is to determine the minimal effective dose of hyperbaric spinal
      bupivacaine required to induce a reliable and satisfactory saddle block for perianal
      surgeries (using a modified Dixon's up-and-down method.
    

Detailed description: 
      Following approval of the Research and Ethics Committee of the University of Dammam and
      written informed consent, patients with American Society of Anesthesiologists physical Status
      I and II, 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 barriers,
      taking psychotropic or analgesic medication, or a known history of allergic reactions to
      amide local anesthetics, were excluded from the study.

      Actually, 35 patients were enrolled. However; after they have signed the informed consent; 7
      patients were excluded because they have received analgesics in the morning of surgery, and 4
      patients refused to receive the saddle block on the operating room. So actually 24 patients
      out of 35 participants underwent intervention

      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, the 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 caudally. 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 the
      lithotomy position. Immediately before surgery, the sacral level of sensory block was tested
      using a long surgical toothless clamp gently applied radially, starting from the anal
      orifice, in different diagonal directions.

      The motor block was tested by a modified Bromage scale (0 = no motor block, 1 = able to flex
      the 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 the patient responded with a
      failed block then the next patient received an increment of 0.5 mg bupivacaine, if the
      patient responded with a 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. 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 independent anesthesiologist and
      was administered by a second anesthesiologist. Block assessment and clinical follow-up of the
      patients was also performed by a third 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 the surgery, and
      every 30 minutes until resolution of the block. NIBP and HR were documented every 5 minutes
      in the OR and PACU. Also Times to ambulation, first voiding time, and time to home discharge
      were recorded. Patient's and surgeon's satisfaction 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 the dural puncture was used as the
      primary starting point of assessment.
    

Intervention name(s): Dixon's up-and-down method
Intervention type(s): Drug
Intervention description(s): 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 0.5mg bupivacaine, if patient responded with successful block, then the next patient received a decrement of 0.5mg bupivacaine. The research continued until we obtained seven crossover midpoints.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Perianal surgery; hyperbaric bupivacaine; saddle block