5. Evora PRB, Levin RL. Methylene blue asdrug of choice for catecholamine-refractoryvasoplegia after cardiopulmonary bypass.J Thorac Cardiovasc Surg. 2004;127:895-6

6. Levin RL, Degrange MA, Bruno GF, DelMazo CD, Taborda DJ, Griotti JJ, et al. Meth-ylene blue reduces mortality and morbidity invasoplegic patients after cardiac surgery. AnnThorac Surg. 2004;77:496-9.

7. Ozal E, Kuralay E, Yildirim V, Kilic S,Bolcal C, Kucukarslan N, et al. Preoperativemethylene blue administration in patients athigh risk for vasoplegic syndrome during car-diac surgery. Ann Thorac Surg. 2005;79:1615-9.

8. Kirov MY, Evgenov OV, Evgenov NV, Ego-rina EM, Sovershaev MA, Sveinbjornsson B,et al. Infusion of methylene blue in humanseptic shock: a pilot, randomized, controlledstudy. Crit Care Med. 2001;29:1860-7.

9. Donati A, Conti G, Loggi S, Munch C, Col-trinari R, Pelaia P, Pietropaoli P, et al. Doesmethylene blue administration to septic shockpatients affect vascular permeability andblood volume? Crit Care Med. 2002; 30:2271-7.

Reply to the Editor:We thank Drs Evora and Rodrigues for theirinterest in our case report and their com-ments. The clinical improvement as de-scribed in the series by Leyh and associates1

and the case reports by Grayling,2 Sparicio,3

and their colleagues, was not evident in ourcase. Those authors described dramatic im-provements in mean arterial pressure withcommencement of methylene blue (MB); ourpatient experienced no such benefit. Norepi-nephrine, epinephrine, and vasopressin re-quirements persisted for at least the first 24hours after the operation in our case. Hertreating intensivists believe that her postop-erative course was not significantly shortenedby the use of MB. The dose used (2 mg/kg atinduction of anaesthesia, 2 mg/kg on initia-tion of CPB, and an infusion of 1 mg/kg perhour for a total of 4 hours) was based on thedescription by Grayling and Deakin,2 whichis longer than that used by others.1,3

Nitric oxide vasodilation is implicatedin both sepsis and the refractory vasoplegiaassociated with cardiopulmonary bypass(CPB). The different outcomes in the stud-ies of MB in the septic group and ourpatient may be due to the different pathol-ogy and underlying heterogeneity of septicpatients.4 A case report of dramatic im-provement after MB in a patient with in-fective endocarditis refutes this.2Evora andRodrigues describe the “random” efficacy

of MB when used as a “last minute vaso-pressor.” The evidence for use of MB asanything other than the “last minute vaso-pressor” in such situations does not existfor children. We, therefore, reiterate theneed for clinical trials to answer this ques-tion.

Katherine Taylor, BMed( Hons ), BA, FANZCAformer Fellow in Paediatric Anaesthesia

The Hospital for Sick ChildrenDepartment of Anaesthesia

555 University AvenueToronto, Ontario M5G1X8, Canada

References

1. Leyh RG, Kofidis T, Struber M, Fischer S,Knobloch K, Wachsmann B, et al. Methyleneblue: the drug of choice for catecholamine-refractory vasoplegia after cardiopulmonarybypass? [see comment]. J Thorac CardiovascSurg. 2003;125:1426-31.

2. Grayling M, Deakin C. Methylene blue dur-ing cardiopulmonary bypass to treat refrac-tory hypotension in septic endocarditis.J Thorac Cardiovasc Surg. 2003;125:426-7.

3. Sparicio D, Landoni G, Pappalardo F, Criv-ellari M, Cerchierini E, Marino G, et al.Methylene blue for lithium induced refrac-tory hypotension in off-pump coronary arterybypass graft: report of two cases. J ThoracCardiovasc Surg. 2004;127:592-3.

4. Faber P, Ronald A, Millar BW. Methylthi-oninium chloride: pharmacology and clinicalapplications with special emphasis on nitricoxide mediated vasodilatory shock duringcardiopulmonary bypass. Anaesthesia. 2005;60:575-87.

Assumed oxygen consumption in thedetermination of cardiac output inchildren after cardiac surgeryTo the Editor:We read with interest the article by Faklerand associates1 titled “Assumed oxygenconsumption frequently results in large er-rors in the determination of cardiac out-put.” However, we were surprised that ourprevious article was not cited. We usedrespiratory mass spectrometry to continu-ously measure oxygen consumption (VO2)and compared these direct measurementswith estimated VO2 values using 4 equa-tions, including that of Lafarge and Miet-tinen. We studied ventilated children withcongenital heart disease both during car-diac catheterization and in the intensivecare unit early after cardiopulmonary by-pass surgery.2 We showed an overestima-tion of VO2 in children during cardiac cath-eterization and an underestimation in the

postoperative children, with all 4 equationsbeing particularly unreliable in the postop-erative group.

As rightly pointed out by Fakler andcolleagues,1 use of assumed VO2 will resultin large errors in the calculation of hemo-dynamic variables, such as cardiac outputand systemic and pulmonary vascular re-sistance. This issue becomes particularlyimportant in patients during the early post-operative period, when VO2 is not onlyincreased as a result of systemic inflamma-tory response syndrome but is also highlydependent on temperature,3 the use of ino-tropes and vasoactive drugs,4 and ventila-tory manipulation.5 Thus although the con-clusions of Fakler and colleagues1 supportour previous observations regarding the useof estimated VO2 during cardiac catheter-ization, we believe our data suggest theneed for even greater caution in the morehighly dynamic hemodynamic milieu ofthe postoperative cardiac intensive careunit.

Jia Li, MD, PhD

Igor E. Konstantinov, MD, PhD

Glen S. Van Arsdell, MD

Andrew N. Redington, MD, FRCP

Cardiac Program

Hospital for Sick Children

Toronto, Ontario, Canada

References

1. Fakler U, Pauli C, Hennig M, Sebening W,Hess J. Assumed oxygen consumption fre-quently results in large errors in the determi-nation of cardiac output. J Thorac Cardio-vasc Surg. 2005;130:272-6.

2. Li J, Bush A, Schulze-Neick I, Penny DJ,Redington AN, Shekerdemian LS. Measuredversus estimated oxygen consumption in ven-tilated patients with congenital heart disease:the validity of predictive equations. Crit CareMed. 2003;31:1235-40.

3. Li J, Schulze-Neick I, Lincoln C, Shore D,Scallan M, Bush A, et al. Oxygen consump-tion after cardiopulmonary bypass surgeryin children: determinants and implications.J Thorac Cardiovasc Surg. 2000;119:525-33.

4. Penny DJ, Sano T, Smolich JJ. Increasedsystemic oxygen consumption offsets im-proved oxygen delivery during dobutamineinfusion in newborn lambs. Intensive CareMed. 2001;27:1518-25.

5. Li J, Hoskote A, Hickey C, Van Arsdell G,Redington A, Adatia I. Hypercapnia im-proves systemic oxygenation and decreasesoxygen consumption and blood lactate levelsin children after bidirectional cavopulmonaryshunt operation. Crit Care Med. 2005;33:984-9.

doi:10.1016/j.jtcvs.2005.08.014

Letters to the Editor

The Journal of Thoracic and Cardiovascular Surgery ● Volume 131, Number 1 251

doi:10.1016/j.jtcvs.2005.09.007

doi:10.1016/j.jtcvs.2005.10.013