Norepinephrine Infusion for Preventing Postspinal Anesthesia Hypotension During Cesarean Delivery

temic effect would have arisen. Thus the vasodilatory effect is more likely the consequence of the sympathetic blocking effect. Unfortunately, the authors injected initially a test dose of lidocaine 60mg which can obtund the effects of the drugs being tested. In a separate but closely related analysis, it should be remembered that a test dose of lidocaine (with epinephrine) produces such a motor-blocking effect that ambulation becomes difficult after an epidural block for labor analgesia. Apart from several other methodological concerns in this study (systematic prehydration, power analysis with different SDs, and superiority study design after announcement that a similar effect was expected), one additional factor should be taken into account. Parturients in pain during labor have an increased work of breathing, higher respiratory rate, and increased ventilation. As the photoplethysmogram is modulated by respiration,3 one mechanism by which the signal was modified could have been related to the reduced ventilation after pain relief was obtained. In conclusion, this study showed, not unexpectedly, that both ropivacaine and levobupivacaine produce similar effects (ie, vasodilatation) as measured by photoplethysmography, and this result does not alter significantly our clinical practice.