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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094On-line version ISSN 1806-907X

Rev. Bras. Anestesiol. vol.54 no.4 Campinas July/Aug. 2004 




Reply - Post-cesarean section analgesia with low spinal morphine doses and systemic nonsteroid anti-inflammatory drug: diclofenac versus ketoprofen


I have read with interest your comments on optimal spinal morphine doses for post-Cesarean section analgesia.

To discuss such issue, we should initially define whether spinal morphine will be used as single postoperative analgesic drug or if it will be part of a multimodal approach in which drugs of different pharmacological groups will be routinely and systematically administered. Major objective of the latter approach is to obtain maximum analgesic effect of each one of them with the lowest possible incidence of side effects. So, I agree that when morphine is used as single analgesic drug, and other drugs such as dipirone and paracetamol will only be administered in case of breakthrough pain, small spinal morphine doses are ineffective. Paracetamol has weak analgesic potency. In this situation, it is recommended to administer higher morphine doses, which in the literature vary 0.1 to 0.3 mg, or even 0.4 mg, as mentioned1.

However, in case of multimodal analgesic approach in which spinal morphine is used in combination with nonsteroid anti-inflammatory drugs, which are routinely and systematically administered and not only when there is pain leakage, lower doses may be safely used2. As mentioned in your letter, nonsteroid anti-inflammatory drugs associated to opioids are today a major component of multimodal pain management3.

Also, it is important to consider that although anti-inflammatory drugs belong to the same pharmacological group, they have different analgesic, anti-inflammatory and antipyretic potency. So, any comparison between different spinal morphine doses should consider that fact. A spinal morphine dose that is effective with a certain anti-inflammatory drug may be ineffective when associated with a different one.Also, it is known that the route of administration of the anti-inflammatory drugs may interfere with its analgesic efficacy. Intramuscular diclofenac provides better quality of analgesia than the rectal rout4.

We decided to evaluate the analgesic efficacy of low doses of spinal morphine and diclofenac because by the time the study was designed, diclofenac was the most common anti-flammatory prescribed by the obstetrians. Also it is known to be safe for the mothers who plan to breastfeed. The amount of drug found in the breastmilk is safe for the neonate.

In conclusion we think that the best option to treat post-cesarean pain is to use the multimodal approach with the combination of small doses of spinal morphine and systemic diclofenac. It is a simple, practical and efficient way to provide postoperative pain relief.

Regarding the anti-inflammatory choice, there are a number o new drugs available in the market, some of them with advantages in terms route and frequency of administration. However they have to be individually studied because the analgesic efficacy of one drug does not guarantee the other, specially when lower doses of spinal morphine are used. Another consideration would be to check the possibility to use in those mothers who plan to breastfeed.

I do not agree with the use of spinal morphine as the sole analgesic drug. Higher spinal morphine doses certainly provide better quality of analgesia. However this comes together with a higher incidence of side effects. For the patients who are too nauseated, have more than two episodes of vomiting or experience a severe pruritus, certainly question the validity of postoperative pain relief. Our goal in terms of providing a good quality of care for patients in the postoperative period should be to offer good pain relief with no side effects.


Yours sincerely

Mônica Maria Siaulys Capel Cardoso, TSA, M.D.
Address: Av. Dr Eneas de Carvalho Aguiar 255
8° Andar, PAMB Division of Anesthesia
ZIP: 05403-900 City: São Paulo, Brazil



01. Gwirtz KH, Young JV, Byers RS et al - The safety and efficacy of intrathecal opioid analgesia for acute postoperative pain: seven years experience with 5969 surgical patients at Indiana University Hospital. Anesth Analg, 1999;88:599-604.

02. Cardoso MMSC, Carvalho JCA, Amaro AR et al - Small doses of intrathecal morphine combined with systemic diclofenac for postoperative pain control after cesarean delivery. Anesth Analg, 1998;86:538-41.

03. Smith G, Power I, Cousins MJ - Acute pain - is there scientific evidence on which to base treatment? Br J Anaesth, 1999;82: 817-819.

04. Cardoso MMSC, Carvalho JCA, Tahamtani SMM - Diclofenaco por via muscular ou retal associado com baixas doses de morfina subaracnóidea para analgesia pós-operatória em cesarianas. Rev. Bras Anestesiol, 2002;52:666-672.

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