We thank our colleagues for their comments and criticisms of our study, 1and we wish to offer the following responses.

First, it is not hard to measure respiratory rate, oxygen saturation, and arterial blood pressure during morphine titration because monitors perform those functions well. Moreover, determination of Ramsay score is also very rapid, because an awake patient who is able to rate his or her visual analog scale (VAS) can be easily quoted 1 on the Ramsay score. Concerning the verbal and subjective behavioral scale used by our nurses, the reader could refer to our recent published study. 2The definition of inadequate analgesia requiring rescue was subjective: the anesthesiologist decided to stop morphine titration and use another analgesic technique, usually when more than 10–15 bolus of morphine were administered.

We do not accept the term “retrospective” used by Larijani and Goldberg. Indeed, the design of our study was clearly defined after a pilot study, 3a special data sheet was implemented (although this data sheet is now that used in routine practice in our unit), and all consecutive patients who fulfilled the criteria for inclusion and did not fulfill the criteria of exclusion were included. Thus, we think that this study was prospective.

We agree with Larijani and Goldberg that we need more information on the relationship between morphine requirement and the type of surgery. The influence of gender is real, but its magnitude seems not to be very important. Last, we previously demonstrated that age does not modify morphine requirement during intravenous morphine titration, 4,5whereas subcutaneous morphine requirement during the initial 24 h is significantly decreased in elderly patients. 5Larijani and Goldberg suggest that higher-bolus doses could be more rapidly efficient. We agree with this hypothesis, but the incidence of adverse outcomes may also increase. Only a randomized study could provide the response, and we have begun such a study.

Larijani and Goldberg report that their patients who had abdominal hysterectomy required a higher dose of morphine. In our study, 33 women underwent abdominal hysterectomy and they actually required 14 ± 8 mg (0.23 ± 0.14 mg/kg) morphine during intravenous titration, indicating that this surgery induced severe postoperative pain requiring a greater dose of morphine. However, comparison of the morphine doses during postoperative intravenous titration must be done cautiously, because the anesthetic regimen during the preoperative period, including the type and dose of opioids administered, may markedly interfere with that dose. The interest of our study is only to provide data from a large population to help to recognize some important relationships between the measurement of pain using VAS and morphine requirements. Further studies are required to precise the preoperative and postoperative variables associated with morphine dose in the postoperative period, as recently studied by Dahmani et al.  6 

In our opinion, the definition of severe pain (i.e. , VAS > 70) may not be very useful for a given patient. In contrast, we have explained that this definition may help to identify a population of patients that could benefit from morphine titration in less supervised clinical conditions, such as emergency medicine, or may help to stratify the severity of pain during clinical trials. 1 

We do not agree with the comment from Dr. Myles concerning the linear versus  sigmoid nature of the relationship between visual analog scale and morphine dose. In our study, we provided several statistical points of evidence that this curve is better described using a sigmoid curve than a straight line. These data include both the initial (30–40) and final (80–100) parts of the VAS range. The important question is whether or not this relationship reflects the VAS-pain relationship. In our study, we suggest that measuring the morphine dose required to obtain pain relief may be another way to assess the severity of pain. However, we agree that we did not take into account the complex nature of pain, which cannot be summarized only by its intensity, and that opioid-dose response has substantial interindividual variability.

In conclusion, we hope that our recent studies on intravenous morphine titration 1–5will favor the development on more clinical research on this important topic.

Aubrun F, Langeron O, Quesnel C, Coriat P, Riou B: Relationships between measurement of pain using visual analog score and morphine requirements during postoperative intravenous morphine titration. A nesthesiology 2003; 98: 1415–21
Aubrun F, Paqueron X, Langeron O, Coriat P, Riou B: What pain scales do nurses use in the postanaesthesia care unit? Eur J Anaesthesiol 2003; 20: 745–9
Aubrun F, Monsel S, Langeron O, Coriat P, Riou B: Postoperative titration of intravenous morphine. Eur J Anaesthesiol 2001; 18: 159–65
Aubrun F, Monsel S, Langeron O, Coriat P, Riou B: Intravenous morphine titration in the elderly. A nesthesiology 2002; 96: 17–23
Aubrun F, Bunge D, Langeron O, Saillant G, Coriat P, Riou B: Postoperative morphine consumption in the elderly patient. A nesthesiology 2003; 99: 160–5
Dahmani S, Dupont H, Mantz J, Desmonts JM, Keita H: Predictive factors of early morphine requirements in the post-anaesthesia care unit (PACU). Br J Anaesth 2001; 87: 385–9