**2.15. The mechanism and effects of IVLT in chronic pain**

The specific effects of IVLT rely on the pharmacological action of lidocaine. However, other elements of care are also critically important especially the psychosocial dynamics of the diagnosis and treatment process. Three mechanisms contribute to improvement in a patient's pain or functioning; the specific or intended effects of treatment, natural history of the disease and non-specific effects of treatment [292].

One non-specific treatment effect likely to improve treatment outcomes is high pre-treatment expectations of recovery [293–299]. Factors shown to modulate pre-treatment expectations include dispositional optimism [300–302], sex [297, 303], age [303], education level [297, 303], clinician-patient interactions [304] and degree of psychological distress [297]. Expectations can be enhanced by verbal suggestions, conditioning and imagery [299]. Influences likely to improve treatment outcomes include high expectations, no pre-existing mood disorder, low levels of anxiety, acceptance of the chronic pain diagnosis, a desire to get better, a need to return to a previous level of functioning, motivation and good clinician-to-child relationship and trust in the healthcare team.

Children and youth with chronic pain will require a lot of effort on the part of the clinicians to establish trust as they have met with many previous different healthcare workers; they may have been given mixed messages regarding the aetiology of pain, and potentially exposed to a negative encounter (not feeling believed that they have pain, lack of empathy, poor communication, lack of appropriate help).

To gain a child or youth's trust and that of their parents requires good communication [304–306]. This demands devotion of enough time to listen and extract a precise pain history, use of appropriate language and terminology, developmentally appropriate explanation of concepts [307] as well as understanding family culture, beliefs, hopes and fears. Trust necessitates that; potentially embarrassing questions are asked separately and in confidence and that the healthcare team convey empathy and expertise/credibility in chronic pain management. Introducing appropriate humour into the dialogue also helps to establish good rapport. It is also important to explain to a child/youth with ongoing pain that the healthcare team will attempt to minimise any pain on examination. During the initial assessment good education, establishing an agreed workable goal-directed and achievable management plan positively alters patient outlook as well as responses to treatment [298, 308]. Communicating positive expectations of treatment also contributes to decreased pain and improved functioning [309–311].

Psycho-social effects such as sadness, frustration, anxiety, anger, catastrophization or depression are the detrimental factors that are associated with continuation or worsening of pain. If these psychological factors remain unrecognized and untreated, they become barriers to the onward progress of any chronic pain management plan.

Without the evidence of a randomised double-blind placebo controlled trial, it is not easy to discern the over-riding beneficial therapeutic modality in the chronic pain case series presented. It could be argued that IVLT responsiveness, in tandem with good rapport and trust in the healthcare team, represents a placebo response. Such a response is defined as 'the psychobiological response seen after administration of a non-therapeutic modality'. Placebo treatments have known effects on endogenous pharmacology, as well as the cognitive and conditioning systems in humans [312–319]. The placebo response rate is higher in children compared with adults [320, 321]. Patient expectations and the doctor-patient relationship contribute to placebo analgesia responses and are unique to the individual [322]. The respiratory centres, serotonin secretion, hormone secretion, immune responses and heart function are also involved in the biological response to placebo analgesic treatments [319]. There is evidence that endogenous endorphins play a role as some placebo analgesic responses are reversed with naloxone [318, 323]. When considering non-analgesia placebo responses, dopamine also plays a major role [324]. Placebo response, or not, IVLT is a short intervention with minimal side effect profile, it is a worthwhile component of therapy that helps effect a turnaround to recovery in a child or youth who may have had pain and disability for many months prior to the intervention.

In an effort to increase the effectiveness of multi-disciplinary pain programs, more research is needed to further investigate pharmacological advances, psychological therapies and physiotherapy techniques that work for different ages, different types of pain and at different times in the chronic pain journey. It is clear that we also need to research and adopt clinical strategies aimed at optimising placebo and non-specific treatment effects in the paediatric population.
