The role of the autonomic nervous system in acute surgical pain processing - what do we know?

The case for invasive placebo – is the devil in the detail?

“…Pre-operative hypertension (Table 1) [1] is associated with an increased risk of peri-operative cardiac events and/or mortality (for example [2][3][4][5]); however, its omission from various risk stratification algorithms, such as the Revised Cardiac Risk Index [6] amongst others, has precipitated a fall in profile of this condition. This fall in profile is at odds with its frequency.…”

“…In several studies, pre-operative hypertension predicts mortality, or mortality and major morbidity, in a wide spectrum of surgery, from cardiac [3,8], to orthopaedic [2], to day-case surgery [4]. This should be unsurprising to anaesthetists for …”

“…This research study was prompted by the 2011 case series from McDonnell et al that showed a marked benefit of stellate ganglion block performed for similar indications with respect to postoperative pain scores and analgesic requirements [2]. Two editorials accompanied McDonnell et al's paper; one discussed the potential for modulation of acute somatic pain by the autonomic nervous system [3], and the other called for robust substantiation of the findings before such an approach was incorporated into routine clinical practice [4]. Kumar et al.…”

Psychosocial Stress-Induced Analgesia: An Examination of Effects on Heat Pain Threshold and Tolerance and of Neuroendocrine Mediation

“…The autonomic nervous system (ANS) interacts with nociceptive processing in a complex manner at all levels of the neuraxis [31] since afferent sympathetic fibres process sensory information from nociceptors [32]. In animals, a sympathetic-adrenal-medullary-induced increase of catecholamines has been associated with elevated cardiac and vascular activity, which is linked with diminished pain sensitivity in animals [33] and in male humans [11,34,35].…”

Heart rate and systolic blood pressure in patients with minor to moderate, non-haemorrhagic injury versus normal controls

“…This is largely due to a prevailing sympathetic outflow as the result of decreased baroreflex receptor sensitivity induced through the tissue injury. Pain appears to affect baroreceptor sensitivity, but through mitigation of the vagal component of the receptor (the exact mechanism still eludes scientists) 6. However, only severe pain induces any clinically distinguishable effect and even then the result can be variable 6–8.…”