Short term stability of pH-adjusted lidocaine-adrenaline epidural solution used for emergency caesarean section.
BACKGROUND
Lidocaine-bicarbonate-adrenaline mixtures are commonly used for epidural bolus doses for emergency caesarean section. Previous research has shown that adrenaline degrades completely 24 h after mixing. Anecdotal enquiries suggest that anaesthetists who use such mixtures commonly prepare the solution ahead of use, despite a lack of data about its stability between 0 and 24 h. The aim of this study was to monitor the degradation of adrenaline in the above mixture over 20 h.


METHODS
2 mL of sodium bicarbonate 8.4% was added to 20 mL of 2% lidocaine; 2 mL of this mixture was discarded and 0.1 mL of adrenaline 1:1000 added. The mixtures were stored in plastic syringes at 24 degrees C unprotected from light (n=3) or in the dark (n=3). Non-alkalinised controls were also prepared. Adrenaline and lidocaine were assayed by high performance liquid chromatography at 0, 2, 4, 6 and 20 h.


RESULTS
In the bicarbonated mixture exposed to light, chemical degradation of adrenaline was fast at room temperature, only 73.0+/-3.6% of adrenaline remaining after 6h. In the dark, the stability of adrenaline improved and 95.8+/-3.6% remained after 6h. Negligible degradation occurred in the absence of bicarbonate in either condition. Lidocaine concentrations remained unchanged regardless of the storage conditions.


CONCLUSIONS
This study suggests that preparation of pH-adjusted lidocaine-adrenaline mixtures in advance and prolonged storage in the light is inadvisable.
Tuleu
C
C
Department of Pharmaceutics, The School of Pharmacy, University of London, Magill Department of Anaesthesia, Intensive Care & Pain Management, Chelsea & Westminster Hospital, London, UK. catherine.tuleu@pharmacy.ac.uk
Allam
J
J
Gill
H
H
Yentis
S M
SM
D000704:Analysis of Variance; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000737:chemistry*; D002585:Cesarean Section; D004338:Drug Combinations; D004355:Drug Stability; D004356:Drug Storage; D004630:Emergencies; D004837:Epinephrine / Q000737:chemistry*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008012:Lidocaine / Q000737:chemistry*; D019999:Pharmaceutical Solutions / Q000737:chemistry; D011247:Pregnancy; D017693:Sodium Bicarbonate / Q000737:chemistry; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000737:chemistry*
D000779:Anesthetics, Local; D004338:Drug Combinations; D019999:Pharmaceutical Solutions; D014662:Vasoconstrictor Agents; D017693:Sodium Bicarbonate; D008012:Lidocaine; D004837:Epinephrine