Surgery for the correction of chest wall deformities, the commonest of which is pectus excavatum, is becoming more frequently performed, as minimally invasive surgical techniques are developed. This poses a challenge for the thoracic anaesthetist to provide appropriate perioperative pain relief for thoracic surgery for benign disease and what in many cases is an ostensibly cosmetic procedure.

Pectus correction was originally carried out by the Ravitch procedure. This was major thoracic surgery, involving removal of costal-cartilages and elevation of the sternum using small steel bars. This has now been super-ceded by the Nuss procedure. The Nuss procedure involves the thoracoscopic placement of a concave pectus bar, from the right side of the chest which is placed beneath the intercostal muscles and then flipped into a convex position to elevate the sternum, within the chest. The procedure involves two small (approximately 2 cm) lateral incisions in the chest wall for each pectus bar. One or two bars are used during each corrective procedure [1]. Severity of pain is related to the severity of the pectus (greater Haller Index) and the amount of elevation that is required. Two bars are paradoxically often less painful than one.

The bars are removed after approximately 2 years. This involves a second anaesthetic and further perioperative pain management.

Other procedures for chest wall surgery include local plastic reconstructive surgery, plastic flaps and silicone implants.

The patient population is predominantly young males with body image issues or perceived shortness of breath on exertion due to restrictive lung function. They are generally a highly-motivated group, who actively seek out the surgery and surgeons and are therefore motivated and prepared for a degree of post-operative pain.

However, the surgery is extremely painful and inadequate pain management can exacerbate post-operative complications, cause bar displacement, limit early mobilisation, limit enhanced-recovery and prolong hospital stay.

There is also an incidence of chronic post-operative pain and the patient should be aware of this before undergoing the procedure.

The pain management options include thoracic epidural anaesthesia or an opiate based technique. Regional blocks also play a role.

A survey and review of pain management following Nuss procedure was carried out over 108 Paediatric Hospitals in North America, Europe, Asia and Australasia, and was published in 2014. Fifty-five institutions carrying out the NUSS procedure responded and were performing the operations on patients aged between 14 and 17 years of age. Ninety-one percent of institutions used thoracic epidural anaesthesia and otherwise intravenous patient-controlled analgesia was used. Sixteen percent of the paediatric hospitals said they were stopping epidurals, preferring opiate PCAs [2]. A meta-analysis comparing epidural analgesia and Intravenous patient-controlled analgesia was also published in 2014. Only three randomised-controlled trials and three retrospective studies met inclusion criteria. Epidural analgesia produced slightly lower pain scores immediately post-operatively and in the first 12–48 h post-surgery, compared with PCA, but this did not translate into significantly different secondary outcomes such as reduced length of hospital stay and reduced hospital costs [3].

A standard anaesthetic technique involves a small dose of a short-acting opiate on induction of anaesthesia, such as fentanyl, followed by a longer-acting opiate such as morphine during the procedure. Immediate post-operative pain can be managed in the recovery room using protocolised incremental doses of intravenous fentanyl or morphine administered by recovery nurses, with assiduous respiratory monitoring, and sedation scoring, until the patient is comfortable.

Patient controlled opiate anaesthesia (PCA) with fentanyl or morphine is used in the post-operative period. Many studies report using PCA in addition to epidural analgesia. This requires careful monitoring of cardiovascular and neurological observations. Opiates should not be given via two different routes, i.e. by intravenous PCA and epidural infusion, to avoid opiate side effects. In younger children nurse controlled analgesia (NCA) can be used. This involves regular pain assessments by the nursing-staff, with a nurse-administered opiate bolus based on the patient’s weight. A standard adult PCA protocol includes a bolus dose (e.g. 1 mg of morphine or 20 ug of fentanyl) and a 5 minute lockout period, with or without a low dose background infusion. This enables the patient to titrate opiate consumption according to his or her individual requirements and expectations of post-operative pain. More severe pectus is associated with higher PCA morphine consumption. There was an increase in 6 % morphine usage with every 1 cm increase in pectus depth [4].

Intra-operative opiate analgesia can be supplemented by drugs with different mechanisms of action, which act synergistically and have an opiate-sparing effect. Conventional non-steroidal anti-inflammatory drugs (Cox-1 inhibitors) that can be administered intravenously include diclofenac and ketorolac. They inhibit the cyclo-oxygenase system and prostaglandin synthesis and therefore usual contraindications apply such as asthma, renal dysfunction, peptic ulceration and bleeding. In 2005 The European Medicines Agency (EMA) review on cox-2 specific inhibitors such as rofecoxib and paracoxib identified an increased risk of thrombotic events such as myocardial infarction and stroke. This has led to an increased reluctance to use cox-2 inhibitors intra-operatively. However the pectus population are young and fit and so advantages outweigh the risks in these patients. Indeed cox-2 inhibitors may have advantages in patients at risk of increased bleeding and gastric ulceration (PROSPECT Website).

Paracetamol is also a useful adjunct to an opiate- based technique. The mechanism of action of paracetamol has not been entirely elucidated but there is evidence that it also works on cox-2 receptors, predominantly in the central nervous system. Intravenous paracetamol is highly effective as it has 100 % bio-availability avoiding first pass metabolism in the liver in comparison with oral or rectal preparations. It can be given in conjunction with NSAIDs. One gram of intravenous paracetamol is said to have similar analgesic efficacy to 10 mg of Intra-muscular morphine [5].

Other more novel analgesics can be used intra-operatively or in the recovery room in patients with refractory pain.

Ketamine is an N methyl D aspartate (NMDA) receptor antagonist which has profound anaesthetic and analgesic properties, in small doses administered either intra-venously or intra-muscularly. It is opiate-sparing, reducing opiate side-effects such as respiratory depression. It may also prevent spinal-sensitisation or ‘wind-up’ which is attributed to the development of chronic post-operative pain syndromes. Intra-muscular administration has some advantages in that the effects of the ketamine are more prolonged. It can also be given as an infusion in the post-operative period.

Clonidine is an alpha-2 adrenergic agonist and imidazoline receptor antagonist. It was originally used to treat hypertension, but has several off-licence uses which include sedation and the treatment of pain. It can be used in conjunction with opiates intra-operatively and in the recovery room and can also be given as an infusion. It works by an entirely different mechanism from opiates and therefore has a synergistic effect.

Gabapentin or Pre-gabalin were originally developed as anti-epileptic medications, but are now used in the treatment of neuropathic pain. They have similar structures to the neurotransmitter GABA and bind to voltage-dependent calcium channels, but their mechanism of action is unclear. There is limited evidence from other areas of surgery that pre-operative gabapentin may confer advantages in the management of post-operative pain. They reduce opiate usages and decrease opiate side effects. They may also have a theoretical role in the prevention of the development of chronic post-operative pain [6]. There is currently no published evidence for their use in Nuss surgery.