Plain chloroprocaine 1% for low dose spinal anaesthesia in minor, outpatient perianal surgery

Background
Low-dose spinal anaesthesia (SPA) is a safe and reliable anaesthesia technique in outpatient perianal surgery. Plain chloroprocaine 1% (CP) is the only short-acting local anaesthetic admitted for intrathecal injection in Germany. Regarding the slightly hyperbaric effect and its duration of action, plain CP seems to be ideal to perform low-dose SPA for perianal procedures. The aim of this trial was to determine the optimal dosage of plain CP 1% in patients undergoing perianal outpatient surgery.
Methods
All patients (male / female, ASA-status I-III, age: 18-80 years) undergoing perianal surgery were eligible for this prospective, randomised, clinical trial. Exclusion criteria were contraindications to SPA and allergies against drugs used. After ethics committee approval 120 patients were enrolled to the study. They were randomised 1:1:1 to receive either 10, 20 or 30mg of CP intrathecally. Patients had to remain seated in an upright position for at least 10 min after injection. We measured the expansion of sensory and motor block and the times until discharge. Statistical analysis was performed using the Kruskal-Wallis-, Chi2-, Tukey- or Fisher´s Exact-Test as indicated.
Results and discussion
No significant differences regarding demographic data could be detected between the groups. We found a positive correlation of the applied dose and the expansion of the sensory (p<0,0005) as well as the motor block (p<0,0086), while a significant motor block occurred only at a dosage of 30mg (Tab. 1). Doses of 10mg and 20mg led to a significant earlier discharge compared to 30mg (p=0,0003 vs. p=0,0406, Tab. 1). Two SPA failed after assumed successful injection (10mg and 30mg, n=1 each). Eight patients in the 10mg group suffered from pain (n=2) due to an incomplete block or discomfort (intestinal pressure, contact with surgeons hand) during the procedure, eased with additional local anaesthesia or sedation.
Conclusion
Plain CP 1% can safely be used for low dose SPA in perianal outpatient surgery. Regarding the avoidable motor block and later discharge-times in the 30mg group as well as the block-failures in the 10 mg group, 20mg can be recommended as the nearly “optimal” dose.