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Canadian Journal of Anesthesia 52:112-113 (2005)
© Canadian Anesthesiologists' Society, 2005

Correspondence

Continuous extrapleural infusion of ropivacaine in children: is it safe?

Konrad Maurer, MD, Katharina M. Rentsch, PhD, Alexander Dullenkopf, MD, René Prêtre, MD and Edith R. Schmid, MD

Zurich, Switzerland

To the Editor:

In contrast to bupivacaine, ropivacaine has not yet been shown to be suitable in the clinical context of continuous intercostal nerve blockade using an extrapleural catheter in children and young infants.1,2 After approval of the hospital’s Ethical Committee and obtaining parental consent, the pharmacokinetics of an extrapleural bolus of 0.5 mL•kg–1 ropivacaine 0.2% followed by a continuous extrapleural infusion at two different rates (0.2 mL•kg–1•hr–1 and 0.3 mL•kg–1•hr–1, resp.) for 48 hr were evaluated in two children undergoing cardiac surgery via a lateral thoracotomy (patient 1: male, four years old; patient 2: female, six years old). Anesthesia was performed according to our standard protocol and at the end of the operation an extrapleural catheter (20-gauge, multi-orifice, SIMS Portex Ltd., Hythe, UK) was placed as described earlier.3 The bolus of ropivacaine 0.2% was administered when the patients recovered from anesthesia (adequate reactions to verbal command) and the infusion was maintained for 48 hr. Total plasma concentrations of ropivacaine and plasma concentration of {alpha}1-acid glycoprotein were assessed at the hours t = 1/6, 1/3, 0.5, 1, 3, 6, 18, 30, 48, 50, 52 and 54. Total ropivacaine plasma concentration showed a first peak 30 min after the initial bolus. Its highest value was measured at the end of the continuous infusion (FigureGo) and exceeded the limit of 2.2 mg•L–1 that is accepted to be safe in terms of toxicity as described by Knudsen et al.4 The measured concentrations of {alpha}1-acid glycoprotein remained within the normal range. The capacity of {alpha}1-acid glycoprotein to buffer the free fraction of ropivacaine which, mainly, is responsible for toxic reactions in the context of a continuous infusion of local anesthetics was, therefore, not increasing. Thus, we may not assume a subsequent decrease in the unbound fraction of ropivacaine. Clinically, no pathological findings in terms of toxicity were found.



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  		FIGURE Evolution of venous total ropivacaine concentrations. Hours = time in hours after administration of the bolus of ropivacaine. The continuous extrapleural infusion of ropivacaine 0.2% was stopped at 48 hr.

 
Our preliminary results suggest that intercostal nerve block with an initial bolus of 0.5 mL•kg–1, followed by a continuous infusion through an extrapleural catheter of 2 mg•mL–1 ropivacaine at 0.2 mL•hr–1 and 0.3 mL•hr–1 over 48 hr is at the edge of being considered a safe technique for analgesia after lateral thoracotomy. More investigations - also in terms of pharmacodynamics - are needed to determine the optimal rate and concentration of ropivacaine administered through an extrapleural catheter in children.

Footnotes

Support was provided solely from departmental sources.

References

1 Downs CS, Cooper MG. Continuous extrapleural intercostal nerve block for post thoracotomy analgesia in children. Anaesth Intensive Care 1997; 25: 390–7.[Medline]

2 Karmakar MK, Booker PD, Franks R, Pozzi M. Continuous extrapleural paravertebral infusion of bupivacaine for post-thoracotomy analgesia in young infants. Br J Anaesth 1996; 76: 811–5.[Abstract/Free Full Text]

3 Sabanathan S, Eng J, Mearns AJ. Alterations in respiratory mechanics following thoracotomy. J R Coll Surg Edinb 1990; 35: 144–50.[Medline]

4 Knudsen K, Beckman Suurkula M, Blomberg S, Sjovall J, Edvardsson N. Central nervous and cardiovascular effects of i.v. infusions of ropivacaine, bupivacaine and placebo in volunteers. Br J Anaesth 1997; 78: 507–14.[Abstract/Free Full Text]





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