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Minerva Anestesiologica 2002 June;68(6):523-7


language: English

Wash-in and wash-out curves of sevoflurane and isoflurane in morbidly obese patients

Torri G., Casati A., Comotti L., Bignami E., Santorsola R., Scarioni M.

From the Department of Anesthesiology IRCCS H. San Raffaele Vita-Salute University of Milan - Milan


Background. The aim of ­this pros­pec­tive, ran­dom­ized ­study is to com­pare sevof­lu­rane and iso­flu­rane phar­ma­cok­i­net­ics in mor­bid­ly ­obese ­patients.
Methods. With Ethical Committee approv­al and writ­ten ­informed con­sent, 14 ­obese ­patients (BMI >35 kg/m2), ASA phys­i­cal stat­us II, under­go­ing lapar­os­cop­ic, sil­i­cone-adjust­able gas­tric band­ing ­were ran­dom­ly allo­cat­ed to ­receive ­either sevof­lu­rane (n=7) or iso­flu­rane (n=7) as ­main anes­thet­ic ­agents. General anes­the­sia was ­induced ­with 1 µg·kg-1 fen­ta­nyl, 6 mg·kg-1 sodi­um thi­o­pen­tal, and 1 mg·kg-1 suc­ci­nyl­cho­line fol­lowed by 0.4 mg kg-1·h-1 atra­cu­ri­um bro­mide (dos­es ­were ­referred to ­ideal ­body ­weight). Intermittent pos­i­tive pres­sure ven­ti­la­tion (IPPV) was ­applied ­using a Servo-900C ven­ti­la­tor ­with a non­re­breath­ing cir­cuit and a 15 l·min-1 ­fresh gas ­flow (­tidal vol­ume: of 10 ml·kg-1; res­pir­a­to­ry ­rate: 12 ­breaths/min; inspir­a­to­ry to expir­a­to­ry ­time ­ratio of 1:2) ­using an oxy­gen/air mix­ture (FiO2=50%), ­while sup­ple­men­tal bolus­es of thi­o­pen­tal or fen­ta­nyl ­were giv­en as indi­cat­ed in ­order to main­tain ­blood pres­sure and ­heart ­rate val­ues with­in ±20% ­from base­line. After ade­quate place­ment of tra­cheal ­tube and sta­bil­iza­tion of the ven­ti­la­tion param­e­ters, 2% sevof­lu­rane or 1.2% iso­flu­rane was giv­en for 30 min via a non­re­breath­ing cir­cuit. End-­tidal sam­ples ­were col­lect­ed at 1, 5, 10, 15, 20, 25 and 30 min, and meas­ured ­using a cal­i­brat­ed ­infrared gas ana­lyz­er. General anes­the­sia was ­then main­tained ­with the ­same inha­la­tion­al ­agents, ­while sup­ple­men­tal fen­ta­nyl was giv­en as indi­cat­ed. After the ­last ­skin ­suture the inha­la­tion­al ­agents ­were sus­pend­ed, and the end ­tidal sam­ples ­were col­lect­ed at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 min. Then the ­lungs ­were man­u­al­ly ven­ti­lat­ed ­until extu­ba­tion.
Results. No dif­fer­enc­es in age, gen­der and ­body ­mass ­index ­were report­ed ­between the two ­groups. Surgical pro­ce­dure ­required 91±13 in the sevoflurane ­group and 83±32 min in the isoflurane ­group. The FA/FI ­ratio was high­er in the sevoflurane ­group ­from the 5th to the 30th min. Also the wash­out ­curve was fast­er in the sevof­lu­rane ­group dur­ing the obser­va­tion peri­od; how­ev­er, the ­observed dif­fer­enc­es ­were sta­tis­ti­cal­ly sig­nif­i­cant ­only 30 and 60 sec ­after dis­con­tin­u­a­tion of the inha­la­tion­al ­agents.
Conclusions. The ­results of ­this pros­pec­tive, ran­dom­ized ­study con­firmed ­that sevof­lu­rane pro­vides ­more rap­id ­wash-in and ­wash-out ­curves ­than iso­flu­rane ­also in the mor­bid ­obese ­patient.

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