Rev. Bras. Anestesiol. vol.66 número5

RevBrasAnestesiol.2016;66(5):554---555

REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

LETTERS

TO

THE

EDITOR

Answer

to

the

question

of

Dr.

Da-Qiang

Zhao

about

hypobaric

ropivacaine

Resposta

à

pergunta

do

Dr.

Da-Qiang

Zhao

sobre

ropivacaína

hiperbárica

DearEditor:

FirstofallIwanttothankyouforyourkindinterestonour

manuscriptentitled‘‘Ropivacaineforunilateralspinal

anes-thesia;hyperbaricorhypobaric?’’1_{onbehalfoftheauthors.}

You got a query on how the baricity of the solution was

0.997.2 _{First of all Ihave tostate that the dansitometer}

we haveused inthe study wasupto threedecimals

sen-sitiveandthemeasurementsof thesamplesweredone at

26◦_{Cwhich wasthepreset temperatureof thelaboratory}

andwe assumedit astheroomtemperature. The density

ofdistilledwaterdecreasesfrom1mgmL−1_after4◦_C

grad-ually as reported by Patterson and Morris,3 _{which means}

thatdistilledwaterishypobaricatbothroomtemperature

andbody temperature. Secondly, McLeod has definedthe

densitiesoflocal anestheticsolutionsofbupivacaine,

lev-obupivacaine,andropivacaine23◦_Cand37◦_Cstatingthat

onlyexceptforlevobupivacaine5and7.5mgmL−1_alllocal

anestheticsbehavehypobaricatbodytemperature.4 _Since

both distilledwater and the localanesthetic solution are

hypobaric,the resultant mixture is hypobaric. Theremay

beinadvertentmistakesatthirddecimalofthebaricityof

thesolutionwehavemeasuredduetothatthedansitometer

weusedwasonlythreedecimalssensitiveanda2◦_Chotter

environment than room temperature at the laboratory,

where density measurements were performed, may have

changedthelastdecimalofthedensity.Inconclusion,the

resultantsolutionwashypobaric.Ihopethiscouldhelpyour

query.

Conflicts

of

interest

Theauthordeclaresnoconflictsofinterest.

References

1.CantürkM,Kılcı O,Ornek D,etal. Ropivacainefor unilateral spinalanesthesia;hyperbaricorhypobaric?RevBrasAnestesiol. 2012;62:298---311.

2.Da-QiangZ.Aquestionaboutropivacaineforunilateral spinal anesthesia:hypobaricsolution.RevBrasAnestesiol.2012;65:311.

3.PattersonJB,MorrisEC.Measurementofabsolutewaterdensity, 1◦_Cto40◦_{C.Metrologia.1994;31:277---88.}

4.McLeodGA.Densityofspinalanestheticsolutionsofbupivacaine, levobupivacaine, and ropivacaine with and without dextrose. BJA.2004;92:547---51.

MehmetCantürk

DepartmentofAnesthesiologyandReanimation,AhiEvran

UniversityEducationandResearchHospital,Kirsehir,

Turkey

E-mail:drmcanturk@gmail.com

Availableonline18June2016

http://dx.doi.org/10.1016/j.bjane.2016.04.004