Intravenous morphine used alone or with topical tetracaine effectively reduced levels of pain in preterm newborn infants undergoing central line insertion procedures, according to a study in the February 15 issue of JAMA.

About 10 percent to 15 percent of newborns require prolonged hospitalization for conditions such as preterm birth, birth defects, and sepsis (a blood stream infection). As part of their medical care, they are often exposed to multiple invasive procedures that may be painful. There is accumulating evidence that untreated procedural pain in newborns leads to long-term changes in pain sensitivity, according to background information in the article. The effectiveness of local or systemic analgesics (pain relievers) to minimize pain in newborns during certain procedures is not clear.

Anna Taddio, Ph.D., of the Hospital for Sick Children and University of Toronto, and colleagues studied the relative efficacy and safety of topical local anesthesia (tetracaine) and intravenous opioid analgesia (morphine), used alone or in combination, for management of pain in newborns undergoing the insertion of a central venous catheter.

The randomized, double-blind, controlled trial, conducted between October 2000 and July 2005, included 132 ventilated newborns (average gestational age, 30.6 weeks at study entry). Prior to catheter insertion, the newborns were randomly assigned to receive tetracaine (n = 42), morphine (n = 38), or both (n = 31); a separate nonrandomized group of 21 neonates receiving neither tetracaine nor morphine was used as a control group.

The researchers determined pain scores by measuring the proportion of time newborns displayed facial grimacing (brow bulge) during different phases of the procedure (skin preparation, needle puncture, and recovery).

The authors found that the combination of morphine (opioid analgesia) and tetracaine (local anesthesia) was more effective than either local anesthesia alone or no analgesia in reducing the pain of catheter placement, but similar in effectiveness to opioid analgesia alone. Local anesthesia alone, however, was not consistently different from no analgesia, suggesting that it was a weak analgesic.

“We hypothesize that morphine was more effective than tetracaine because morphine reduced the sensory input derived from multiple phases of the procedure that differed in both the location and degree of invasiveness, whereas tetracaine decreased sensation from the needle puncture site,” they write.

Concerning adverse events, morphine caused respiratory depression and tetracaine caused erythema (abnormal redness of skin).

“These findings are consistent with the underlying mechanisms of action for both drugs,” the researchers write. “These data can be used to support evidence-based protocols for the pharmacologic management of pain during percutaneous central venous catheter placement in ventilated neonates,” the researchers conclude.

http://www.jamamedia.org