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11. Patient‐controlled epidural analgesia provides effective analgesia but optimal settings are
not clear (N) (Level I).
12. Single‐injection intrathecal opioids provide comparable early labour analgesia to epidural
local anaesthetics with increased pruritus (U) (Level I).
13. Systemic opioids in labour increase the need for neonatal resuscitation and worsen acid‐
base status compared with regional analgesia (U) (Level I).
14. Nitrous oxide has some analgesic efficacy and is safe during labour (U) (Level I).
11.1.3 Pain management during lactation
A number of general principles apply when administering analgesic and antiemetic drugs for
pain management during lactation:
• the choice of drugs should be based on knowledge of their potential impact on
breastfeeding and on the breastfed infant secondary to transfer in human milk; and
• the lowest possible effective maternal dose of analgesic is recommended, breastfeeding is
best avoided at times of peak drug concentration in milk, and the infant should be
observed for effects of medication transferred in breast milk.
The effects of many analgesic and antiemetic drugs during lactation have not been adequately
investigated, leaving clinical decisions to be made on evidence derived from pharmacokinetic
or observational studies, case reports and anecdote. For most drugs, information on infant
outcome is inadequate (based on single‐dose or short‐term administration or on case reports)
or absent, so maternal consent is advisable and caution is warranted.
The principles of passage of drugs in human milk (Ito, 2000; Berlin & Briggs, 2005; Ilett &
Kristensen, 2005) including drugs relevant to pain management (Rathmell et al, 1997; Spigset &
Hagg, 2000; Bar‐Oz et al, 2003) have been reviewed. The maternal plasma concentration, which is
influenced by the dose and the ability of the mother to metabolise the drug, is an important
determinant of drug levels in milk. High lipid solubility, low molecular weight, low protein
binding and the unionised state favour secretion into breast milk. Most drugs have a milk‐to‐
plasma ratio of 1 or less (Ito, 2000). The neonatal exposure is often 0.5% to 4% of the maternal
dose, but infant drug metabolism may be impaired, and much of the data is from single
maternal dose studies rather than chronic therapy (Berlin & Briggs, 2005). A safe level of infant
exposure to a drug has been arbitrarily defined as no more than 10% of the therapeutic dose
for infants (or the adult dose standardised by weight if the infant dose is not known) (Ito,
CHAPTER 11 are secreted, so early breastfeeding is unlikely to pose a hazard, even from drugs administered
2000). Until about the third to fourth postpartum day only very small amounts of colostrum
in the peripartum period.
Lactating women having surgical procedures with general anaesthetic have been advised to
discard their milk for 24 hours following the operation. Following single intraoperative doses
of midazolam (2 mg), propofol (2.5 mg/kg), and fentanyl (100 mcg), less than 0.1% of the drugs
were excreted into milk within 24 hours, suggesting that interruption of breastfeeding may not
be required (Nitsun et al, 2006 Level III‐3).
Drugs that might be prescribed during lactation have been categorised according to their risk
for the baby. Some of the drugs that might be used in pain management are listed with
comments in Table 11.3.
390 Acute Pain Management: Scientific Evidence
