LETTERSTOTHEEDITOR 447
Continuous
bilateral
transversus
abdominis
plane
block
after
abdominal
surgery
Bloqueio
do
plano
transverso
abdominal
contínuo
bilateral
após
cirurgia
abdominal
DearEditor,
I read with great interest the article of Lima et al.1
concerning the use of continuous local anesthetic infu-sion via catheters placed bilaterally in the transversus abdominis plane (TAP) for postoperative analgesia after exploratory laparotomy. I congratulate them on the pre-sentation of thecase. However,I wouldlike toaddsome comments.
TAP block has become an important method of post-operativepainmanagementfor patientsundergoinglower abdominalsurgeryasaresultof itseffectiveness,relative easeof establishment andlow rateofcomplications.2We
agree withthe authors that it is important toassess the idealconcentrationandvolumeforbolus andinfusion and proper placement of the catheterwithin TAP. But in this sense,besidesthe efficacy,thesafetyissue shouldnotbe forgotten.Thus, theinstillationof large volumesinto the TAPbilaterallycanleadtosignificantintravascular concen-trationsoflocal anesthetic,evenexceedingthethreshold of toxicity.3 Thus,Hessian etal. in a recentinvestigation
determinedrelativelyhighcumulativedosesofropivacaine, assessingropivacaineplasmaconcentrationsduringasimilar continuousinfusionintotheTAPasproposedbytheauthors.4
Thereby,despite markedindividualvariability,carefulrisk benefitassessmentshouldbeperformedbeforecontinuous TAPblocks,especiallyinelderlypatients,renalor hepatic dysfunctionand gestation.5 The main objectiveof a
con-tinuoustechniqueshouldbeadministeringthelowesttotal dose of a local anesthetic effective to prevent undesir-able effects due to toxicitybecause otherwise I consider thatitdoes notprovide additionalbenefitwithrespectto a technique based onbolus administration into the TAP.6
Thus, in our institution, we use bilateral TAP catheters inserted by ultrasound imagingin the Triangle of Petitor inapostero-subcostallevelaccordingtothetypeof surgi-calincision, basedonbilateralcontinuousinfusion of0.2% ropivacaine 2mL/h for up to 50h with previous admin-istration of bolus of 5mL of 0.2% ropivacaine and 10mL throughbothcathetersbeforeremoving them,with excel-lentresults.
Likewise,theauthorsasertthat‘‘althoughtoxicplasma concentrations of local anesthetic have been detected, there areno reports of clinical signs of systemic toxicity associated with local anesthetic’’; however, the previous
studiesreportedseveral casesof symptomatic local anes-thetictoxicity.4,7
Moreover, the authors claim that ‘‘although TAP pro-videssuperioranalgesiacomparedtoplacebo,thevisceral pain, etc., remains, which requires the addition of IV opioidsin the blockade’’. It should be remembered that posteriorapproachtotheTAPpermitsspreadoflocal anes-theticsolutiontotheparavertebralspaceandpartofthis also results in some degree of epidural spread of local anesthetic. This extension to the central nervous system might explain patients requiring minimal extra analgesia postoperatively.8
TheoptimalsiteofinsertionofTAPcatheters,theideal localanestheticsolution,volumeandoptimalinfusionrate areyettobedetermined.Thisrequiresmorerigorous sci-entificinvestigation.
References
1.LimaIF,LindaF,DosSantosA, etal.ContinuousbilateralTAP blockinpatientwithpriorabdominalsurgery.RevBras Aneste-siol.2013;63:422---5.
2.McDonnell JG, O’Donnell B, Curley G, et al. The analgesic efficacyoftransversus abdominisplaneblockafterabdominal surgery:aprospectiverandomizedcontrolledtrial.AnesthAnalg. 2007;104:193---7.
3.SharkeyA,FinnertyO,McDonnellJG.Roleoftransversus abdomi-nisplaneblockaftercaesareandelivery.CurrOpinAnaesthesiol. 2013;26:268---72.
4.Hessian EC, Evans BE, Woods JA, et al. Plasma ropivacaine concentrations during bilateral transversus abdominis plane infusions.BrJAnaesth.2013;111:488---95.
5.Gómez-Ríos MÁ. Continuous transversus abdominis plane cathetertechniqueforpostoperativeanalgesiaafterabdominal surgery.AnaesthIntensiveCare.2013[inpress].
6.NirajG, KelkarA,JeyapalanI,etal. Comparisonofanalgesic efficacy ofsubcostal transversus abdominis planeblocks with epiduralanalgesiafollowingupperabdominalsurgery. Anaesthe-sia.2011;66:465---71.
7.GriffithsJD,LeNV,GrantS,etal.Symptomaticlocalanaesthetic toxicityandplasmaropivacaineconcentrationsafter transver-susabdominisplaneblockforCaesareansection.BrJAnaesth. 2013;110:996---1000.
8.FinnertyO,McDonnellJG. Transversusabdominisplaneblock. CurrOpinAnaesthesiol.2012;25:610---4.
ManuelÁngelGómez-Ríos
DepartmentofAnesthesiaandCriticalCare,Complejo HospitalarioUniversitariodeACoru˜na,ACoru˜na,Spain E-mail:magoris@hotmail.com(M.A.Gómez-Ríos). Availableonline12March2014
