Description of the condition

Acute pain has long been underestimated and untreated in the paediatric population, as it was thought that infants could not feel pain and that older children did not remember it. In addition, fear of overdosing or adverse effects prevented administration of adequate pain relief in children. However, acute pain should be considered as the fifth vital sign along with heart rate, respiratory rate, blood pressure and temperature. It is most often 'nociceptive' and results from injury, surgery, internal disease, or a combination of these. Specialized nerve endings called 'nociceptors' that are attached to nerve fibres collect the pain message at the site of tissue injury and forward it to spinal targets and eventually to cortical structures resulting in conscious pain perception, and conscious and subconscious responses to the pain. Different receptors and neurochemicals are involved in the transmission of pain messages; therefore, treatment of acute pain should be multimodal and involve medications which target different receptors. Chosen combinations of analgesics would then enhance the analgesic potency of each other; thereby finding the optimal combination and mode of delivery has the potential to reduce both the required dose of each drug and the incidence of adverse effects (Astuto 2009). It is likely that pain will be under treated if it is not assessed appropriately and regularly. Assessment of pain must be age‐appropriate and easily implemented at the bedside, and result in a reasoned and prompt adjustment of the analgesic dose. As children do not express the same pain behaviours as adults, several pain score scales have been developed and validated for paediatric populations. There are around 16 defined pain scales used for neonates (Committee on Fetus and Newborn 2016). The most frequently used pain scales are the Neonatal Infant Pain Scale (NIPS) and the Neonatal Pain, Agitation and Sedation Scale (N‐PASS) (Hillman 2015); the Premature Infant Pain Profile (PIPP) (Jonsdottir 2005); the COVERS Neonatal Pain Scale (Hand 2010); the Pain Assessment Tool (PAT) (Krechel 1995; Spence 2005); and the Crying Requires Increased oxygen administration, Increased vital signs, Expression, Sleeplessness (CRIES) (Krechel 1995).

Description of the intervention

Systemic opioids are commonly used to provide postsurgery analgesia in both adults and children. However, opioid therapy is associated with serious adverse effects including respiratory depression, hypotension and withdrawal often needing slow opioid weaning. Very preterm infants given morphine took significantly longer to reach full enteral feeding than infants in control groups (Bellu 2008). Therefore, to avoid or diminish potential risks caused by sole use of opioid analgesia, other pain control measures (i.e. additional analgesic preparations (non‐steroidal anti‐inflammatory drugs (NSAIDs), paracetamol), ultrasound‐guided transversus abdominis plane (TAP) block or epidural analgesia were trialled in infants undergoing surgical procedures. Intravenous paracetamol showed opioid‐sparing effects even after major abdominal surgery, but usage is limited by gestational age and birth weight, in addition to hepatic and renal impairment and its potential effects on neurodevelopment (Avella‐Garcia 2016; Ceelie 2013; Ohlsson 2015). Epidural analgesia achieves very good results in pain relief and reduces incidence of postoperative respiratory failure, specifically in high‐risk infants undergoing major surgery (Park 2001; Rigg 2002). However, it is widely recognised that the epidural technique is not universally successful and that inadequate analgesia is experienced by 20% to 30% of adults (Burstal 1998; McLeod 2001). Epidural‐associated hypotension is a frequent problem. Infrequent but potentially devastating complications such as epidural haematoma or abscess formation must always be considered (Cook 2009).

As a result, researchers are in search of alternative analgesic regimens. Local anaesthetic wound infiltration after chest and abdominal procedures and TAP blocks for abdominal wounds are some of the strategies (Hermansson 2013). There is an overlap in terminology used for local anaesthetic wound infiltration for postsurgical abdominal wounds and TAP blocks. Though both provide local anaesthetic infusion through a catheter entering the surgical wound, it is the location of the catheter tip that is the key difference. For local wound infiltration, the tip is placed in the subcutaneous space, muscle fascia or preperitoneal space. However, for the TAP block, the catheter tip is between the transverse abdominis and internal oblique laterally, and in the posterior rectus sheath medially. For this review, local wound analgesia will include local anaesthetic wound infiltration (catheter tip in the subcutaneous space, muscle fascia or preperitoneal) and TAP block (catheter tip between the transverse abdominis and internal oblique laterally, and in the posterior rectus sheath medially) for postsurgical abdominal wounds. For wound analgesia after procedures in the thoracic region, the catheter tip is usually inserted in the thoracotomy or sternotomy incision, or parasternally and into mediastinum (Kocabas 2008).

How the intervention might work

Continuous infiltration of local anaesthetic via a flexible catheter (tip for local wound infiltration in the subcutaneous space, muscle fascia or preperitoneal; however, for TAP block, the catheter tip is between the transverse abdominis and internal oblique laterally, and in the posterior rectus sheath medially) inside or alongside surgical wounds enables continuous, evenly spread infiltration of local anaesthetic over an indefinite period. It relieves pain by direct inhibition of noxious afferent generator potentials from peripheral nerve fibres and attenuation of the local inflammatory response to injury. Considered advantages include: ease of placement and fewer complications during insertion in comparison to epidural analgesia, in addition to the potential for reduced postoperative opioid requirements and increased postoperative mobility (Thornton 2011).

The effectiveness of the technique seems to be determined by: positioning of the catheter, and choice and concentration of local anaesthetic agent. Catheter placement within the preperitoneal space after laparotomy has been shown to reduce postoperative pain and accelerate recovery along with some potential benefits on postoperative pulmonary function (Beaussier 2007). In contrast, catheter placement superficial to muscular fascia has been so far shown to be largely ineffective (Chan 2010). One randomised controlled trial in children between three months and 12 years of age concluded that continuous subfascial bupivacaine infusion is reliable, safe and effective in paediatric postoperative pain control with considerably reduced opiate requirements (Machoki 2015). Studies have demonstrated that the placement of catheters in the appropriate muscle layers (TAP) after open nephrectomy and colorectal resection can achieve a significant reduction in requirements for additional opiates (Beaussier 2007; Forastiere 2008). One randomised controlled trial of ultrasound‐guided TAP versus local wound infiltration in children undergoing appendectomy reported that TAP block provided prolonged postoperative analgesia and reduced analgesia use without any clinical adverse effects (Shaaban 2014). One systematic review comparing TAP versus local anaesthetic wound infiltration in lower abdominal surgery in adults reported comparable short‐term postoperative analgesia, but TAP block had better long‐lasting effects (Yu 2014). Similarly, placement of the catheter either in the thoracotomy or sternotomy wound, or parasternally and into the mediastinum after cardiac surgery, was effective in reducing postoperative morphine consumption (Kocabas 2008). The effectiveness of local anaesthetic wound infiltration and opioid analgesia combinations in the provision of superior pain relief and reduction in opioid consumption after cardiothoracic surgery has been demonstrated in both adults and children (Kocabas 2008; Tirotta 2009).

Various local anaesthetic infusion regimens contribute vastly to the effectiveness of the analgesia. It appears that in the setting of laparotomy, a relatively high concentration of long‐acting agent (e.g. bupivacaine 0.5%) provides superior analgesia to placebo while lower concentrations of bupivacaine (e.g. 0.25%) have not ensured adequate analgesia in majority of adults. In contrast, lower concentrations of ropivacaine (0.2%) achieved sufficient analgesia and lower rescue opioid requirements (Beaussier 2007; Chan 2010).

Why it is important to do this review

A brief scoping search of the Cochrane database revealed no studies on use of local wound analgesia postsurgery in neonates. In the literature, there is limited information on the physiological benefits of local wound analgesia in neonates in terms of return of bowel function, need for indwelling catheterisation, hospital stay, rates of surgical site infection and short‐term wound complications (White 2010). Therefore, it seems appropriate to explore the benefits and disadvantages of local wound analgesia and currently used systemic pain control in neonatal postsurgical procedures. A more comprehensive review is required to summarise the evidence base and provide recommendations for future trials comparing this new technique to others.