Caesarean section is a common surgical procedure performed to deliver babies through an incision of the abdomen and uterus when vaginal delivery is contraindicated for maternal or fetal reasons or, in some cases upon request of the pregnant mother. It can either be done as an emergency or electively. The rate of caesarean section has been increasing around the world (Delbaere 2012). The rate of caesarean section differs around the world between 2% in least developed countries and 21% in developed countries and reaching 45.9% in Brazil (Betran 2007; Getahun 2009; Gibbons 2010). In the USA, caesarean section rates increased, from 20.7% in 1996 to 31.1% in 2006 for women of all ages, race, gestational ages, and in all states MacDorman 2008.
Caesarean section is associated with more postpartum pain than vaginal birth (Kainu 2010) and leads to more acute and chronic postpartum pain (Ingrid 2006). Postpartum pain has various negative consequences including:
it causes significant discomfort to women, which can lead to difficulties in mobility and subsequent problems, such as, an increased risk of venous thrombosis, and by interfering with optimal interaction with the newborn in the immediate postpartum period;
shallow breathing and splinting may result in atelectasis and predispose to pneumonia;
it may reduce the ability of the mother to initiate or continue with breastfeeding effectively Gadsden 2005.
Effective post-caesarean pain relief is important to avoid the above-mentioned problems. Different interventions have been proposed for post-caesarean pain relief, e.g. oral, intravenous and rectal analgesia with various drugs and various doses, regional analgesia, transversus abdominis plane block and combinations of the above-mentioned interventions.
The review will compare the effectiveness and safety of different classes of oral analgesia for post-caesarean pain relief.
Description of the condition
Post-caesarean pain is a result of incisional pain as well as pain from the uterus (e.g. uterine contraction after birth). Incisional pain is experienced by women following caesarean section due to tissue trauma from surgical incision, dissection and burns or direct nerve damage from nerve transection, stretching or compression Kelly 2001. Tissue trauma causes release of local inflammatory mediators that can produce augmented sensitivity to stimuli in the area surrounding an injury, i.e. hyperalgesia or misperception pain to non-noxious stimuli. The patient senses pain through the afferent pathway. Pharmacologic agents target these pathways Woolf 1993.
Pain varies in intensity and the onset of the post-operative pain depends on form of anaesthesia used during the procedure. This pain almost always requires some form of analgesia Kodali 2012.
Description of the intervention
Oral analgesia is a simple, easy to administer, well-tolerated and cost-effective type of pain relief that is offered to women after caesarean section.
1. Opioid analgesics
Natural opioids (codeine, dyhydrocodeine, morphine)
Diphenylpropylamine derivatives (dextropropoxyphene, dipipanone)
Other opioids (tramadol, tilidine)
2. Non-opioid analgesics
A. Para-aminophenol derivatives (paracetamol or acetaminophen)
B. Non-selective non-steroidal anti-inflammatory drugs (NSAIDs)
Acetylated salicylates (aspirin or acetylsalicylic acid)
Propionic acid (ibuprofen)
Acetic acids (diclofenac)
Fenamates (mefenamic acid)
C. Alpha-2 agonists
3. Combination drugs (e.g., paracetamol/codeine, paracetamol/tramadol, paracetamol/codeine/ibuprofen etc.).
Oral analgesics have various side-effects. The adverse effects of these drugs include nausea, vomiting, constipation, diarrhoea, drowsiness, respiratory depression, pruritis (itch), rash, fluid retention.
How the intervention might work
Different types of oral analgesics have different ways of achieving an analgesic (painkiller) effect.
Analgesic effects of opioids are due to decreased perception of pain, decreased reaction to pain as well as increased pain tolerance. Opioids act through binding to specific opioid receptors in the nervous system and other tissues. Opioids reduce the perception of pain by activating pain-inhibitory neurons and inhibiting pain transmission neurons (Chahl 1996).
Non-opioid analgesics act by reducing the nocioreceptive response to the endogenous inflammatory mediators released at the sites of tissue damage (Kuo 2006). NSAIDs block cyclo-oxygenase (COX), an enzyme responsible for the synthesis of prostaglandins (Chandrasekharan 2002). Pharmacological inhibition of COX can provide relief from symptoms of inflammation and pain by inhibition of prostaglandin synthesis.
Combination drugs (e.g. paracetamol/codeine, paracetamol/codeine) exhibit enhanced effects due to the different mechanism of action of their components SAMF 2012.
The exact mechanism of analgesic effect of alpha-2 agonists is unknown, though the release of acetylcholine may play a role Gordh 1989; Kodali 2012. There are reports suggesting that alpha-2 agonists such as clonidine and dexmedetomidine have a potent analgesic response, and that their potency is increased by concomitant opioid therapy Kodali 2012. Alpha-2 agonists have been reported to decrease post-operative pain Hidalgo 2005; Sung 2000.
Anticonvulsant agents such as gabapentin are gamma-aminobutyric acid analogues and have also been reported to have analgesic effects as well as opioid-sparing effects Kodali 2012. Although the main use of anticonvulsants is for chronic pain, there are reports supporting their adjunctive role in post-operative pain Mathiesen 2007; Moore 2009.
Why it is important to do this review
Many drugs with various mechanisms of action are used for post-caesarean pain relief. Although the response to pain relief is sometimes believed to be individual, it is very important to establish the most effective with the least adverse effects type of oral analgesia for women after caesarean section .
Optimal pain control post-caesarean section will benefit not only the mother and her baby, but also a healthcare system. Optimal pain control may shorten the time spent in hospital after caesarean section and, therefore, reducing healthcare costs Shang 2003.