Minor Anorectal Procedures & Perianal Abscess
Most commonly haemorrhoids, perianal fistulas & anal fissures.
Summary
Dose: 1 ml (5 mg) of 0.5% hyperbaric or isobaric bupivacaine + 15 mcg fentanyl.
Position: Sit, remain sitting for 10 minutes (hyperbaric only), then lithotomy.
Expectation: Surgical anaesthesia for up to 60 minutes.
Evidence
4-5mg of 0.5% hyperbaric bupivacaine (patient sitting, sit for 10 min, then supine) is sufficient for anorectal surgery of short duration (20-30 min) [1]. Average block (cold) was L4 in both groups. Supplementary fentanyl and/or thiopentone was required in 6-8% of patients. Difficult urination was experienced by up to 17% of patients. Catheterisation was required in 4.6% of 5 mg patients, and 0% of 4 mg patients. Time to urination was 270-300 minutes on average.
In a group of young (~25 yr) patients undergoing pilonidal cyst/sinus surgery, 5 mg isobaric bupivacaine (sitting, then immediately prone) was 100% successful [2]. A median level of T12 was achieved and surgery lasted an average of 60 minutes.
5 mg or 10 mg hyperbaric bupivacaine (lateral, immediately supine or lithotomy) was successful in all patients undergoing short (< 60 min) procedures (urology, orthopaedic, anal – majority anal) [3]. An average level of T11 was achieved. Ambulation, on average, within 3 hours. Void, on average, within 4 hours. Home readiness was achieved in 80% at 6 hours, and 90% at 7 hours.
1.5 mg (0.2 ml) and 6 mg (0.8 ml) 0.5% hyperbaric bupivacaine (sitting until S4 blocked ~ 5 min) were successful in perianal procedures lasting ~ 50 minutes [4]. 90% patients were placed in jack-knife and 10% lithotomy. In both groups block (pain) was restricted in sacral dermatomes. 1.5 mg patients discharged at ~ 2 hours and 6 mg patients at ~ 4 hours.
One investigator, in a letter to the editor questioned the 1.5 mg dose used above [5]. In his own (incomplete) dose finding studying (0.5% hyperbaric bupivacaine), he found block efficacy at 2 mg, 3 mg and 4-5 mg of 20%, 90% and 100% respectively.
4 mg 0.5% hyperbaric bupivacaine with 10 mcg fentanyl (sitting, inject over 2 minutes, sit 10 min, lithotomy) achieved a median level of L4 (temperature), and appears (no fail data presented) to have been successful for perianal surgery duration ~26 minutes [6].
5 mg 0.75% bupivacaine with 10 mcg fentanyl (diluted to 3 ml with NaCl 0.9%) was successful for perineal surgery (hydrocelectomy, fissurectomy, varicocelectomy, haemorrhoidectomy, circumcision, orchidopexy) of surgical duration ~ 23 minutes [7]. Voiding and discharge occurred ~ 3-3.5 hours after spinal injection.
References
Gudaityte J et al. Low-dose spinal hyperbaric bupivacaine for adult anorectal surgery: a double-blinded , randomised controlled study. J Clinical Anes 2009;21:474-481.
Cuvas et al. The use of low dose plain solutions of local anaesthetic agents for spinal anaesthesia in the prone position: bupivacaine compared with levobupivacaine. Anaesthesia 2009;64:14-18.
Tarkkila et al. Home-readiness after spinal anaesthesia with small doses of hyperbaric 0.5% bupivacaine. Anaesthesia 1997;52:1157-1160.
Wassef et al. Spinal perianal block: a prospective, randomised, double-blind, comparison with saddle block. Anesth Analg 2007;104:1594-6.
Carron et al. Spinal block with 1.5 mg hyperbaric bupivacaine: not successful for everyone. Anesth Analg 2007;105:1515-6.
Borodiciene et al. Lithotomy versus jacknife position on haemodynamic parameters assessed by impedence cardiography during anorectal surgery under low dose spinal anaesthesia: a randomised controlled trial. BMC Anesthesiology 2015;15:74.
Imarengiaye et al. Spinal Anaesthesia: Functional balance is impaired after clinical recovery. Anesthesiology 2003;98:511-5.