Research examining analgesia efficacy following surgery is essential, in order to ensure optimum post-operative care is given to patients. Due to the difficulty of insertion and placement of the thoracic epidural in patients with significant thoracic scoliotic deformities requiring instrumented fusion, the intrapleural analgesia technique was adapted at our centre to deliver local anaesthetic directly to the spine after anterior thoracic fusion surgery. This retrospective study was performed to present the authors’ technique of using intermittent analgesia via an intrapleural catheter, present patient reported pains scores after thoracoscopic scoliosis correction and identify any adverse events related to the technique.
The use of an intrapleural catheter placed under direct vision in the operating theatre has several advantages; it allows the delivery of local anaesthetic directly to the site of the spinal levels involved in the instrumented fusion surgery and allows pre-emptive analgesia to be administered in these predominantly adolescent patients. Pre-emptive analgesia has been shown to have more beneficial effects and results in reduced analgesia dosages being used, as opposed to waiting for pain levels to increase prior to giving analgesia [26–30]. Effective analgesia after open thoracic surgery is conducive to good respiratory effort, better ventilatory mechanisms and gas exchange and decreased incidence of atelectasis . The respiratory benefits of effective analgesia are also highly desirable after minimally invasive surgery involving single lung ventilation, as well as for early mobilisation of these patients. A previous study on the first 100 cases of the larger patient series at our centre  found patients were mobilised a mean 1.6 days after surgery and was significantly less again when the initial 40 cases were excluded to account for the learning curve of the thoracoscopic technique and postoperative management regimes.
The technique of giving an intermittent bolus as opposed to a continuous infusion of local anaesthetic, allows the delivery of a higher dose of anaesthetic and therefore a more concentrated effect to achieve a dense neural block and is in keeping with postoperative epidural practice. The chest drain is clamped for around 30 minutes during delivery of the bolus and at all other times functions normally to assist with the clearance of the pleural effusion. A chest drain under continuous suction would hinder the effectiveness of a continuous delivery of local anaesthetic so was considered inappropriate for patients after TASF. Postoperatively, patients don’t tend to complain of pain from the incisions/portals over their general spine pain. However the intrapleural anaesthetic bolus is able to freely flow in the pleural space so may have some effect on minimising pain originating from the portals. With the patients receiving a multi-modal analgesia approach it is difficult to attribute how much the intrapleural analgesia may ease any portal incision pain over the effects of the PCA and additional non-opiate oral analgesia.
It is worth noting that for 42 of the 230 boluses (18%) assessed in the current study, the patients already had a pain score of zero before receiving a further local anaesthetic bolus, demonstrating good on-going analgesia between boluses. It is also important to note that, at our hospital, the use of intrapleural catheters and their analgesic effectiveness is carefully monitored on the ward by nursing, pharmacy and medical staff with the support of a specialised pain team. A protocol document to describe how to use the catheter, any potential complications, and the action to take in the event of any complication was developed (Table 1). Registered nurses caring for a patient with intermittent intrapleural analgesia must have attended a Paediatric Pain Management Workshop with successful completion of the two relevant modules (Management of a Paediatric Patient under the Pain Management Service, and Intermittent Bolus Intrapleural Analgesia).
The visual analogue pain score is a well-recognised tool for monitoring post-operative pain [31–33] and has been validated in the paediatric population . It has previously been suggested that, on the 100 mm scale, a score of 0-4 mm can be considered pain-free, 5-44 mm mild pain, 45-74 moderate pain, and more than 75 mm is severe pain  Bird et al. suggested that 13 mm was a significant decrease in scores less than 34 mm, whilst Bodian et al. proposed that for pain scores between 3 and 7 on a ten-point scale, a change of one or more was significant. This supports the current study findings that the mean decrease in pain score (a decrease of 1.75 on the ten-point scale) after administration of an intrapleural bolus was indeed significant. However, this does not negate the fact that pain is a subjective sensation that has multiple influencing factors, along with the potential placebo effect from receiving a bolus of local anaesthetic. Figure 5 presents the mean pain scores for all patients during the first four postoperative days, with the generally low mean scores suggesting the analgesia regime was effectively controlling the pain of the patient group. With the chest drain removed at mean 61 hours after surgery, and the intrapleural catheter removed at mean 58 hours after surgery, these may both have contributed to the drop of mean pain scores in the 60-72 time period of Figure 5. The histogram in Figure 4 clearly shows the change in distribution of pain scores reported before and after intrapleural analgesia is given. Before a bolus, the pain scores given most often were at the higher end (4-6) of the VAS scale, with a shift of the distribution toward lower pain scores (0-3) after a bolus was given, with a substantial proportion of the group reporting zero pain scores after a bolus.
We note that the most common reason for pain scores not being recorded in the medical notes in this study was the patient sleeping. The protocol policy document instructs staff not to seek a pain score from a sleeping patient (Table 1). Missing scores are a potential problem for any prospective study, however waking a sleeping child for assessment of their pain level would predictably result in an inaccurate and anomalous score recorded. The fact that a patient was sleeping would suggest that the pain management was satisfactory and, therefore, conducive to the on-going sleep state.
Patients in the study received opiates via a patient-controlled intravenous method. The quantity of opiates used via PCA in this study increased significantly in the second 24 hour period after surgery. This period (24 – 48 hours postop) coincides with the patient being mobilised and sat out of bed for the first time since surgery and physiotherapy and nursing interventions commenced to achieve restoration of full lung re-expansion and volumes. Opiate usage decreased significantly between the second and third and third and fourth 24 hour periods and was lower again once the intrapleural catheter and chest drain were removed (Figure 6). This may suggest that the catheter and chest drains were a source of some pain but it is most likely a combination of the removal of these irritants and the normal course of rapid recovery after minimally invasive surgery. Patients often report some shoulder tip pain from the chest drain which does not respond to IV narcotics and is eased by the intrapleural bolus. The shoulder tip pain ceases when the chest drain is removed on Day 2 or Day 3. Patients are discharged home usually Day 5 after surgery and are routinely prescribed non-steroidal anti-inflammatories and paracetemol based medications. The steady reduction of opiate usage, shown in Table 2, was expected since the immediate post-operative pain would likely be improving with each day, and it confirms the rapid recovery from this type of minimally invasive surgery.
It is our opinion that excellent pain management in the early couple of postoperative days with the multi-modal analgesia approach encourages rapid recovery and reduction of morphine use during the hospital stay. It also reduces the need to be prescribed prolonged usage of opiates after discharge home from hospital. In order to see if there was any association between the use of intrapleural analgesia and the required supplemental opiate analgesia, it would be necessary to perform a prospective cohort or randomised trial comparing patient-controlled analgesia with and without intrapleural catheter usage. Surgeons may wish to expand and validate the use of the intrapleural analgesia technique for use with open or minimally invasive anterior scoliosis correction or anterior release procedures prior to posterior instrumented fusion surgery.