- Email: [email protected]
Precision averaging
502
Letters to the Editor / Pain 110 (2004) 499–503
unrelated to whiplash and when the general consensus of the available scientific literature demonstrates the contrary, then these assertions are incorrect. In order to improve our understanding of this condition and thereby facilitate patient recovery, old myths need to be abandoned. The evidence to date emphatically demonstrates that whiplash is a complex condition involving both physical and psychological impairments. As we have stated previously, our next challenge is to adequately address all these aspects and reduce the incidence of chronicity associated with this condition.
References Cote P, Cassidy D, Carroll L, Frank J, Bombardier C. A systematic review of the prognosis of acute whiplash and a new conceptual framework to synthesize the literature. Spine 2001;26(19):E445–58. Linton S. A review of psychological risk factors in back and neck pain. Spine 2000;25(9):1148– 56. Linton S. Occupational and psychological factors increase the risk for back pain: a systematic review. J Occup Rehabil 2001;11:53–6. Schmand B, Lindeboom J, Schagen S, Heijt R, Koene T, Hamburger H. Cognitive complaints in patients after whiplash injury: the impact of malingering. J Neurol Neurosurg Psychiatry 1998;64:339–43. Scholten-Peeters G, Verhagen A, Bekkering G, van der Windt D, Barnsley L, Osstendorp R, Hendriks E. Prognostic factors of whiplash associated disorders: a systematic review of prospective cohort studies. Pain 2003; 104(1–2):303–22. Sterling M, Kenardy J, Jull G, Vicenzino B. The development of psychological changes following whiplash injury. Pain 2003;106(3): 481– 9. Sterling M, Jull G, Vicenzino B, Kenardy J. Physical and psychological predictors of outcome following whiplash injury. Proceedings: Australian Pain Society Conference, Canberra; 2004.
On the other hand, they seem to have misused some of their statistical software. For example, the age of the morphine þ naloxone patients, 41.4 ^ 11.01 years. Did they really record patient’s ages to the one-hundredth of a year? They have introduced one or two extra degrees of precision through averaging. A difference in pain intensity of 0.06 units? I suspect the patients’ verbal pain ratings were in whole numbers (1 –10) only. Although the pain scale is an ordinal measure, it is probably reasonable for statistical purposed to treat the values as though they were continuous. However, it is not reasonable to introduce two extra degrees of precision. Likewise with the rescue doses, how does one administer 5.4 rescue doses? The median number of rescue doses would probably be better. With regard to the opioid requirements, they report that the morphine þ naloxone group required 0.07 mg more over the 24 h period. My reading of their protocol (rescue doses, demand doses, and demand dose adjustments) indicates that the smallest possible dose of opioid was 0.5 mg. Reporting hundredths of a milligram is an increase in precision of 50 times. The fact is, there was simply no difference in opioid requirements. An ingenious idea, a good study, and a lot of hard work are made to look amateurish by lack of attention to detail.
Reference Cepeda MS, Alvarez H, Morales O, Carr DB. Addition of ultralow dose naloxone to postoperative morphine PCA: unchanged analgesia and opioid requirement but decreased incidence of opioid side effects. Pain 2004;107:41–6.
Michele Sterling*, Gwendolen Jull, Bill Vicenzino, Justin Kenardy Department of Physiotherapy, The University of Queensland, St Lucia, 4072 Brisbane, Australia E-mail address: [email protected]
Denis L. Bourke* Baltimore Veterans Affairs Medical Center, Anesthesiology Service, University of Maryland School of Medicine, Baltimore VAMC (115), 10 North Greene Street, Baltimore, MD 21201, USA E-mail address: [email protected]
* Corresponding author. Tel.: þ61-7-3365-4568; fax: þ 61-7-3365-2775. doi:10.1016/j.pain.2004.04.005
* Tel.: þ 1-410-605-7235; fax: þ1-410-605-7793. doi:10.1016/j.pain.2004.03.042
Precision averaging To the Editor: I found the article by Cepeda et al. (2004) very interesting. I think their mixture of morphine and naloxone is ingenious. It would have been interesting if they had tried some other naloxone doses and developed a dose response curve. They might possibly have reduced some of the other undesirable side effects. Hopefully, based on their current success, they plan to do that in the future.
‘Simply no difference’ in pain intensity and opioid requirement when ultralow doses of naloxone are added to morphine PCA To the Editor: We thank Dr Bourke for his interest in our study (Cepeda et al., 2004) and agree with his suggestion that further
Letters to the Editor / Pain 110 (2004) 499–503
unrelated to whiplash and when the general consensus of the available scientific literature demonstrates the contrary, then these assertions are incorrect. In order to improve our understanding of this condition and thereby facilitate patient recovery, old myths need to be abandoned. The evidence to date emphatically demonstrates that whiplash is a complex condition involving both physical and psychological impairments. As we have stated previously, our next challenge is to adequately address all these aspects and reduce the incidence of chronicity associated with this condition.
References Cote P, Cassidy D, Carroll L, Frank J, Bombardier C. A systematic review of the prognosis of acute whiplash and a new conceptual framework to synthesize the literature. Spine 2001;26(19):E445–58. Linton S. A review of psychological risk factors in back and neck pain. Spine 2000;25(9):1148– 56. Linton S. Occupational and psychological factors increase the risk for back pain: a systematic review. J Occup Rehabil 2001;11:53–6. Schmand B, Lindeboom J, Schagen S, Heijt R, Koene T, Hamburger H. Cognitive complaints in patients after whiplash injury: the impact of malingering. J Neurol Neurosurg Psychiatry 1998;64:339–43. Scholten-Peeters G, Verhagen A, Bekkering G, van der Windt D, Barnsley L, Osstendorp R, Hendriks E. Prognostic factors of whiplash associated disorders: a systematic review of prospective cohort studies. Pain 2003; 104(1–2):303–22. Sterling M, Kenardy J, Jull G, Vicenzino B. The development of psychological changes following whiplash injury. Pain 2003;106(3): 481– 9. Sterling M, Jull G, Vicenzino B, Kenardy J. Physical and psychological predictors of outcome following whiplash injury. Proceedings: Australian Pain Society Conference, Canberra; 2004.
On the other hand, they seem to have misused some of their statistical software. For example, the age of the morphine þ naloxone patients, 41.4 ^ 11.01 years. Did they really record patient’s ages to the one-hundredth of a year? They have introduced one or two extra degrees of precision through averaging. A difference in pain intensity of 0.06 units? I suspect the patients’ verbal pain ratings were in whole numbers (1 –10) only. Although the pain scale is an ordinal measure, it is probably reasonable for statistical purposed to treat the values as though they were continuous. However, it is not reasonable to introduce two extra degrees of precision. Likewise with the rescue doses, how does one administer 5.4 rescue doses? The median number of rescue doses would probably be better. With regard to the opioid requirements, they report that the morphine þ naloxone group required 0.07 mg more over the 24 h period. My reading of their protocol (rescue doses, demand doses, and demand dose adjustments) indicates that the smallest possible dose of opioid was 0.5 mg. Reporting hundredths of a milligram is an increase in precision of 50 times. The fact is, there was simply no difference in opioid requirements. An ingenious idea, a good study, and a lot of hard work are made to look amateurish by lack of attention to detail.
Reference Cepeda MS, Alvarez H, Morales O, Carr DB. Addition of ultralow dose naloxone to postoperative morphine PCA: unchanged analgesia and opioid requirement but decreased incidence of opioid side effects. Pain 2004;107:41–6.
Michele Sterling*, Gwendolen Jull, Bill Vicenzino, Justin Kenardy Department of Physiotherapy, The University of Queensland, St Lucia, 4072 Brisbane, Australia E-mail address: [email protected]
Denis L. Bourke* Baltimore Veterans Affairs Medical Center, Anesthesiology Service, University of Maryland School of Medicine, Baltimore VAMC (115), 10 North Greene Street, Baltimore, MD 21201, USA E-mail address: [email protected]
* Corresponding author. Tel.: þ61-7-3365-4568; fax: þ 61-7-3365-2775. doi:10.1016/j.pain.2004.04.005
* Tel.: þ 1-410-605-7235; fax: þ1-410-605-7793. doi:10.1016/j.pain.2004.03.042
Precision averaging To the Editor: I found the article by Cepeda et al. (2004) very interesting. I think their mixture of morphine and naloxone is ingenious. It would have been interesting if they had tried some other naloxone doses and developed a dose response curve. They might possibly have reduced some of the other undesirable side effects. Hopefully, based on their current success, they plan to do that in the future.
‘Simply no difference’ in pain intensity and opioid requirement when ultralow doses of naloxone are added to morphine PCA To the Editor: We thank Dr Bourke for his interest in our study (Cepeda et al., 2004) and agree with his suggestion that further