[Spinal opiates in obstetrics. Theoretical aspects and criteria for practical use]

Spinal opiates were introduced for use in obstetrics during the 1980's. The possibility of achieving analgesic effects with small doses, without motor and/or vegetative involvement, initially aroused a great deal of enthusiasm. After extensive experience using these drugs, however, it seems they only partially live up to these great expectations. Savings on dose seem to be attained only with morphine and the efficacy of spinal opiates used as the only agents against pain during childbirth is limited. Intradural administration is often accompanied by vegetative involvement, and the reduction in motor blockade generally does not have substantial effect on the progression of labor. On the other hand, it is important to underline the advantages of combining opiates with local anesthesia: both doses are reduced, quality of analgesia is greater, as is maternal satisfaction, and fetal/neonatal repercussions are scarce. Finally, in certain cases, opiates may constitute a valid alternative for local anesthesia, especially if delivery is intradural. The use of spinal opiates is certainly an important qualitative advance, though not a definitive one, in obstetrics.