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Ultrasound guided epidural catheter placement in children without test dose may be unsafe.
- Baljit Singh, Manoj Bhardwaj, Deepak K Tempe (15 November 2006)
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Baljit Singh , Manoj Bhardwaj, Deepak K Tempe
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Letter to the Editor: Ultrasound guided epidural catheter placement in children without test dose may be unsafe. ____________________________________________________________________ Manoj Bhardwaj, Baljit Singh, Deepak K Tempe Dr. Manoj Bhardwaj, MD, Assistant Professor, Dr. Baljit Singh, MD, Professor, Dr. Deepak K Tempe, Director Professor & Head. From: Department of Anaesthesiology & Intensive Care G B Pant Hospital, New Delhi 110 002 India. Correspondence: Dr. Baljit Singh E-mail: dr_baljit@yahoo.com Editor - The study on ultrasound guided epidural catheter placement in children is very interesting.1 We endorse the authors’ view that the safety of epidural anaesthesia can be greatly enhanced if spread of local anaesthetic is visualized by ultrasound, however, certain issues need to be discussed. The first one relates to the test dose. The confirmation of placement of the epidural needle in the epidural space by ultrasound would not rule out the possibility of intravascular placement. Further, even though the authors have not mentioned aspiration to confirm intravascular placement, negative aspiration does not rule this out as the vessel wall may collapse over the tip of the needle with the negative pressure created during aspiration. It can be done with a good degree of certainty only by the administration of epinephrine containing test dose. The incidence of accidental intravascular entry by epidural needle/catheter in children has been reported to be as high as 5.6%.2 In order to reduce these risks, a test dose containing epinephrine with the local anaesthetic is recommended before administering the bolus dose. Also, ECG should be monitored continuously for changes in heart rate, rhythm, and T-wave amplitude.3 Further, as the ultrasound image is not of a very high quality, a minor dural breach either at the time of needle insertion or when the needle is turned to face the bevel cephald before insertion of the catheter may be missed leading to large volume of the local anaesthetic being injected into the subarachnoid or even subdural space. We believe that observing the spread of the drug in the epidural space can only be reassuring that the drug has been deposited in the epidural space but it can not be a substitute for an epinephrine containing test dose. Continuous testing for loss of resistance (LOR) has the potential of injecting saline or local anaesthetic solution or air as soon as the LOR is felt. If there is an accidental puncture of a vessel or the dura mater, the solution or air would be injected immediately due to the persistent pressure on the plunger. How the authors in one case in the control group aspirated blood with continuous testing for LOR, is difficult to understand. We differ with the authors’ opinion that inadequate analgesia in two patients in the control group was because the placement of epidural catheter was not optimal. The only way to conclusively prove catheter misplacement is imaging study, which was not performed. Inadequate analgesia in these two patients could be because of the dilution of local anaesthetic by saline or a patchy block that may occur with the injection of air that the authors have used in the LOR technique in the control group. Thus, inadequate analgesia can be attributed to the technique rather than the inappropriate placement of catheter. In the results section, the authors mention that epidural catheters were placed more swiftly in the ultrasound group, even though the time mentioned in the ultrasound group is longer than the control group, [234 (SD 138) s and 162 (SD 75) s]. However, in the abstract section, the times are different. This needs clarification. Further, in the control group, although epidural space was identified using air or saline for LOR, the authors still mention, “once the epidural space had been identified using levobupivacaine 0.25%, 0.2 mg kg-1 of the same local anaesthetic was injected prior to inserting the catheter…..” Also, the authors state that in the ultrasound group, 0.25%, 0.2 ml kg-1 of the drug was used. These may be typographical errors but can confuse the reader. Innovation to improve upon the safety of a technique and our normal anaesthetic practice is a great idea, but focusing on just direct visualization of a not so good quality ultrasound image while ignoring administration of the standard test dose and using continuous LOR technique, in our opinion, may invite more problems than solving them. References: 1. Willescke H, Marhofer P, Bosenberg A, et al. Epidural catheter placement in children: comparing a novel approach using ultrasound guidance and a standard loss-of-resistance technique. Br J Anaesth 2006; 97: 200-7. 2. Guay J. The epidural test dose: a review. Anesth Analg 2006; 102: 921- 9. 3. Fisher QA, Shaffer DH, Yaster M. Detection of intravascular injection of regional anaesthetics in children. Can J Anaesth 1997; 44: 592-8. Conflict of Interest:None declared |
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