Consequences of Procedural Sedation on Pain: Are there any?
Reviewed by Mary Hegenbarth, MD
Dr. Zempsky’s talk was a provocative discussion of several controversial areas, in particular issues of pain perception related to sedative/analgesic medications. This is a hot topic in pain medicine circles but perhaps less appreciated by those delivering PSA.
Concerns surrounding unintended consequences of pain treatment such as opioid abuse are getting a huge amount of press. So how did we get from historical undertreatment of children’s pain to where we are now? Anand (Lancet 1987) showed that infants undergoing PDA ligation had more complications if not given fentanyl. Taddio (Lancet 1997) found boys who underwent newborn circumcision had higher pain scores with subsequent immunizations. Similarly, Weisman (Arch Pediatr Adol Med 1998) found that children undergoing repeated BMA and LPs who received placebo instead of fentanyl for their first procedure had more pain and needed higher doses of opioids for subsequent procedures.
More recently, there has been concern that our treatment could put patients at risk for central sensitization and chronic pain. The concept of opioid induced hyperalgesia (OIH), while controversial, may play a role in both acute and chronic pain management. OIH has been experimentally shown to occur within hours of acute opioid administration. In the acute pain setting, remifentanil is the most frequently implicated agent, while the evidence on fentanyl is contradictory. Strategies that have been proposed to prevent OIH include use of NMDA antagonists (ketamine), gabapentenoids, propranolol, and cyclooxygenase inhibitors.
What about sedatives—do they have the same concerns? Sedative-hypnotic drugs including propofol and GABA agonists can increase pain perception. Experimental models of pain include cold and ischemia (similar to deep tissue/myofascial pain), as well as electrical/heat (similar to superficial pain). Frolich (Anesthesiology 2013) studied the effects of various agents in these models; midazolam increased pain perception for all modalities while propofol and dexmedetomidine increased heat perception but decreased cold/ischemia pain. However, these experimental models are not the same as clinical pain. Many questions remain, including whether exposure to procedural sedation increases pain sensitivity. If so, who would be at greatest risk—children? Repeat customers? Particular agents or procedures? Risk factors such as chronic pain, opioid exposure, anxiety?
Dr. Zempsky presented four examples of children who developed problems such as chronic pain, anxiety, depression and needle phobia following medical PTSD. He discussed the concept of pediatric medical trauma stress (PMTS) involving three phases: Phase I (peritrauma), Phase II (early, ongoing and evolving responses), and Phase III (longer-term). Risk factors for medical PTSD include PICU stay, unexpected/life-threatening illness, high number of invasive procedures, longer hospital stay, female gender, younger age, and psychological factors such as vulnerability and parental coping styles. Thirty-two percent of adolescents with chronic pain have a history of PTSD—how many of these could be from medical experience? We need to consider how to screen for PTSD and how this could affect sedation care—including whether the sedation experience itself could cause PTSD.
Finally, needle fear and phobia were reviewed. Needle fear typically develops in early to middle childhood (5-10 yrs); needle phobia once established lasts decades. Patients with needle phobia often avoid preventive health care and may have poor outcomes from suboptimal management of chronic disease. Consistent, effective needle pain protocols can help prevent this. If pre-sedation screening identifies that a child has needle fear/phobia, consider referral for exposure-based therapy (not simply distraction, which interferes with extinction of the fear response).