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University of Florida, Gainesville, Florida
To the Editor:
We read with interest the recent technical communication by Capdevila et al. titled, "Patient-Controlled Perineural Analgesia After Ambulatory Orthopedic Surgery: A Comparison of Electronic Versus Elastomeric Pumps" (1). The phrase "patient-controlled" has historically been applied to medication delivery modes in which a patient may give a bolus of medication without the intervention of a health care provider. For example, a nurse drawing up additional local anesthetic in a syringe and injecting a labor epidural for breakthrough pain has not been described as "patient-controlled," as the patient is dependent on the provider. The same is true for intravenous opioid patient-controlled analgesia (PCA): a patient having to request a nurse to draw-up and then administer the medication has not be described as utilizing a PCA, or else there would be no difference between standard administration and "patient-controlled."
With this in mind, we are confused by the description of the technique used in this study for the elastomeric pump as being patient-controlled. The methods section explains, "In Group 1 [using an elastomeric pump], the patient or the nurse injected the bolus by means of a syringe connected to the catheter by a three-way tap." However, the discussion section concludes, "Our results show that continuous infusion of ropivacaine by means of LV5® disposable elastomeric pumps associated with bolus injections of the same drug by a nurse is a simple technique for patients in their home [emphasis added]." Since the LV5® has a flow-rate restrictor of 5 mL/h which cannot be bypassed, to give a local anesthetic bolus requires drawing up medication and injecting it viaa syringe and stopcock. Our questions to the authors are: 1) Did the authors send patients home with syringes, needles, and ropivacaine vials, and ask them to draw up the medication and inject it themselves in a sterile fashion as suggested in their methods section? 2) If so, do they suggest this should become a standard practice? And 3) if not, do the authors believe the term "patient-controlled" should be expanded to include a visiting nurse administering a patient-requested catheter bolus to an ambulatory patient?
We do not believe that is a trivial matter of semantics. We have studied in the laboratory (2,3) and clinically used various elastomeric (4) and electronic (5,6) infusion pumps. We would agree that elastomeric pumps are often easier to use and less intimidating to patients than electronic pumps. However, to our knowledge, only one nonelectronic pump is capable of true patient-controlled boluses (4), and then only with a maximum bolus dose of 2 mL every 15 min. There is evidence that patient-controlled local anesthetic infusion is superior to the continuous infusions which nearly all elastomeric pumps provide (7,8), and this is the main reason we continue to utilize electronic pumps for ambulatory perineural infusions in our clinical practice. At least in the health care environment of the United States at this time, it is simply not feasible to have a visiting health care nurse visit patients at their homes when a bolus injection is required, and therefore electronic pumps are often preferable to their less complex counterparts. It is for these reasons that we believe the recent title, "Patient-ControlledPerineural Analgesia After Ambulatory...... [emphasis added]" may be confusing and is important to clarify to readers.
References
Department of Anesthesia and Critical Care Medicine, Lapeyronie University Hospital, Montpellier, France Department of Anesthesia, Clinique du Parc, Lyon, France
In Response:
We would like to thank Ilfeld et al. for their interest in our work (1) and for the pertinent and important comments in their letter to the editor.
We are entirely in agreement with Ilfeld et al. when they state that, strictly speaking, the technique used by the patients of the "disposable pump" group cannot be considered patient-controlled administration. To uphold the established protocol, we discharged patients with the possibility of performing self injections of 0.2% ropivacaine after training in our unit, or with the help of the home care nurses who saw the patients three times daily.
Obviously, this is not standard practice and this amount of individual care cannot generally be provided for all ambulatory patients. Our study was intended to evaluate home use of elastomeric pumps with possibility of self-administration, and to compare them with electronic infusion pumps.
Ilfeld et al. found that "a patient-controlled local anesthetic infusion is superior to the continuous infusion that nearly all elastomeric pumps provide (2,3)."
This conclusion should, however, be tempered by the fact that, in the studies cited, only continuous infusion with concomitant PCA capacity was superior to continuous infusion. Furthermore, in the studies reported by Ilfeld et al. (4,5) only 2 or 3 patients out of 30 actually used the PCA function of their electronic infusion pump, with no evidence that the postoperative analgesia of these 2 or 3 patients was superior to that of the patients who did not use the PCA function.
We are currently using multiple rate disposable pumps with a bypass PCA chamber of 5 mL (Fig. 1) for our patients after ambulatory orthopedic surgery. This new protocol corresponds to a veritable "patient-controlled" regional analgesia.
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This article has been cited by other articles:
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  B. M. Ilfeld and F. K. Enneking Continuous Peripheral Nerve Blocks at Home: A Review Anesth. Analg., June 1, 2005; 100(6): 1822 - 1833. [Abstract] [Full Text] [PDF]
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