Adjuncts to caudal blockade in children.

Correspondence Adjuncts to caudal blockade in children Editor—We read with great interest the editorial by Lön-nqvist 1 regarding caudal additives. The author gives an excellent description of the chronological development of caudal adjuncts. Nevertheless, we were somewhat surprised by his affirmations regarding caudal neostigmine. The author claims that two studies are proof enough to show that caudal neostigmine has no role in the caudal space and its use should be limited to the reversal of neuromuscular block—'no further studies are needed'! Of the seven studies on caudal neostigmine in children, 2–8 only two 3 8 have been mentioned. Sample sizes of these two studies are quite small (n=30 and 20), therefore it seems premature to draw any sound conclusions. Four studies 2 4 7 8 showed a significant prolongation of postoperative analgesia when neostigmine was added to local anaesthetic (5–8 h vs 16–22 h). A dose finding study clearly showed dose-dependent analgesia of caudal neostigmine. 5 A study performed by our group showed a ketamine sparing effect of neostigmine with a postoperative analgesia of 21.8 h. 3 Only one study 6 so far did not observe a significant advantage in terms of analgesia when adding neostigmine to bupivacaine. Secondly, a 30% incidence of PONV as observed in two 3 8 studies is defined by the author as unacceptable. Of the seven studies on cau-dal neostigmine in children, four studies 2 4 6 7 did not show a significant increase in PONV. A dose-dependent increase of PONV has been described in the dose finding study, 5 but only with doses of 30 mg kg À1 or higher. The 30% incidence of PONV encountered in our study 3 might be because of the higher dose of neostigmine (10 mg kg À1) used, but nevertheless only mild PONV was observed as no child presented more than one single episode of vomiting. The same or even higher incidence of PONV can be observed with caudal opioids. 9 10 The effectiveness of antiemetics on preventing neostigmine induced PONV still needs to be tested. With regard to safety, all studies so far show that caudal neostig-mine has a reasonably benign profile with dose-dependent nausea and vomiting the only reported side-effect. In our study the preservative-free formulation has been used and this is strongly recommended. We agree with the author that prospective randomized trials of adequate size are warranted to answer important questions regarding new caudal adjuncts …