J Med Assoc Thai 2003; 86 (7):617

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Concentrations and Costs of a Thirty Second Priming Technique with Sevoflurane Using the Circle Circuit
Thienthong S Mail, Krisanaprakornkit W , Sinkuakool M , Taesiri W , P

Background : Priming the circuit for an application of inhalation agent depends on the time
taken. the fresh gas flow (FGF) rate, the concentration setting of the agent on the vaporizer, and the
priming technique. Based on previous studies, the priming time for a desirable concentration of
sevollurane varied between 30 seconds and 5 minutes. Remarkably, although the cost of priming with
sevollurane was lowest at 30 seconds, concentrations in the circuit were not clearly stated. The aim of
this study was to test the success (and cost) of a 30-second priming technique to achieve a 4.5 per cent
sevotlurane concentration in the circle circuit.
Method : Analyses were done on 20 samplings. Each time the adjustable pressure-limiting
(APL) valve on the assembly was closed, the 2-liter reservoir bag emptied and the patient end occluded.
For 30 seconds. the circuit was filled with oxygen (8 Lเธ—minเธ—1
)
and 8 per cent sevotlurane. The pressure
in the circuit was kept constant at I 0 mbar by partially releasing the excess gas at the patient end.
After 30 seconds, the sevotlurane concentration at the patient end of the circuit was analyzed and the
highest concentration recorded. The cost of the sevollurane used was then calculated.
Results : The sevollurane concentration in all of the samples was more than 4.5 per cent
(mean 6.40%; SD 0.30%). The average amount of liquid sevotlurane used was 1.8 ml at a cost of 42.30
baht (0.9 US$).
Conclusion : A 30-second priming technique was sufficient to achieve the required concen-
tration of sevollurane in the circle circuit thus reducing costs for gaseous induction.
Key word : Sevollurane, Anesthetic Circuit, Cost, Priming Technique

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