A patient recovering in the ICU can suffer pain for different causes including vascular access for therapies, devices for haemodynamic control, endotracheal tube for lung ventilation and, even if these patients are not able to communicate, it is imperative assess and treat pain. Critically ill patients are a heterogenic group with diverse comorbidities and pain can occur on admission for: trauma, post surgical pain, burns, spastic issues, cancer, neuropathic, and central pain. Many different organ system are simultaneously affected by inadequate pain control.
Pain can also occur during procedures like arterial and central line insertion, peripheral blood draw femoral sheet removal, nasogastric tube insertion extubation; as well for nursing care: bathing, sheet-change, mobilisation, repositioning and` breathing exercises.
Despite the awareness of the need for analgesia in ICU patients a significant number of patients are undertreated. Critical care medicine reported that 82% of ICU patients remembered pain or discomfort associated with the endotracheal tube, 38% still recalled pain as their traumatic ICU memory, and 18% were at high risk of developing post traumatic disorder.
A review article (Acute Medicine & Surgery2018;5:207-212) compare three guidelines: The American College of Critical Care Medicine published a revised version of the PAD guidelines in 2018 where the authors reported the ICU PAD Care Bundle to assess, treat and prevent pain, agitation and delirium. The Japanese Society of Intensive Care Medicine established a committee to develop the J-PAD guidelines in 2013 and Federacia Panamericana e Iberica de Sociedades de Medicina Critica y Terapia Intensure (FEPIMCTI) guidelines include an algorithm for administering sedation and analgesia in patients recovered in ICU.
In PAIN (2010) the authors compared 5 self-report intensity scales and suggest that the NRS-V should be the tool of choice for the ICU patient self-report of pain because it is the most reliably and feasible and discriminative self-report scale for measuring a critically ill patient’s pain intensity.
For the patient not able to communicate, the critical care pain observational tool is scale validated between ICU physicians. Five domains go into the final score and include facial expression, body moments compliance with the ventilator or vocalisation for non ventilated patients an muscle tension.
Each of these items can be scored from zero to 2 with a total maximum score of 8. This score in simple and easy to calculate quickly every four hours by nurses as the guideline recommend.
However, in many original articles, the authors recommend that vital signs changes should not be used for pain assessment in critically ill adults.
In the guidelines of FEPIMCTI the authors suggest the algorithms for administering drugs for sedation and analgesia in ICU patients. Opioids should always be considered preferentially as the first-line intervention, but in lower dose asthe authors recommend in many articles. Fentanyl, sufentanyl and remifentanyl are not superior to morphine for the treatment of pain in emergency setting (Pain Management, 2010).
In this era of sparing opioids, we must diminish their use because they can produce sedation, delirium, respiratory depression, ileus, immunosuppression, lengthen ICU LOS, and worsen post- ICU patient outcome. Also in the ICU setting multimodal analgesia must be promoted. Non-opioid analgesics: acetaminophen, nefopam, ketamine, lidocaine, neuropathic agents have each been evaluated in critically ill adults with the aim of sparing opioid use and improving analgesic effectiveness.
The Royal College of Physicians, in their National Clinical Guideline, recommend that paracetamol may have a morphine sparing effect when used in combination with morphine.(Journal of Critical Care-2010 25, 458-462) After paracetamol, Nefopam is the second most frequently used non opioid medication in mechanically ventilated ICU patients. Nefopam is a non-opioid analgesic that exerts its effect by inhibiting dopamine, noradrenaline and serotonine capture in both the spinal and super spinal spaces. A 20mg dose has an analgesic effect comparable 6mg of iv morphine.
(Anaesth.Analg. 2004;98:395-400; Journal of International Medical Research2014, 42-3, 684.692).
The Royal College of Physicians suggest also the use of nitrous oxide/oxygen mixture for patients able to actively inhale the medication and manage the equipment. This tool is useful for medication of extremity trauma, it is also contraindicated under certain circumstances that are not uncommon major trauma, for example, pneumothorax, in the presence of intra-cranial air of intra-abdominal perforation. (Emergency Medicine Australasia-2011 23,761-768).
The Royal College of Physicians include in the guidelines the benefits of ketamine for mild sedation (allowing for manipulation limbs and calming of the patient), and the opiate sparing and the reduction post- traumatic stress disorder was noted.(American Journal of Emergency Medicine, 2007 25,385-390; Asad E. Patanwala, Journal of Intensive Care Medicine1-9 2015).
In ICU patients who have developed opioid tolerance and addiction from opioid analgesics, N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine and magnesium can provide analgesia and prevent withdrawal. Both magnesium and ketamine, acting on NMDA, can be useful to tapering opioids and other sedatives in intensive care and to avoid Iatrogenic withdrawal syndrome (IWS). Very interesting is the role of gabapentinoids in the ICU. The area of interest should be some neuropathic pain condition like Guillan-Barre Syndrome (GBS) and multiple sclerosis. A review published on Cochrane Library showed that the management of pain in GBS is based on a pharmacotherapy, a reduction in pain severity was found when comparing gabapentin and carbamazepine to placebo. A recent randomised controlled trial by Turcotte et all, demonstrated that nabilone as an adjunctive to GBP is an effective, well-tolerated combination for MS-induced NPP. Dexmedetomidine as an analgesic has an opioid-sparing effect, which especially benefits patients with morbid obesity and obstructive sleep apnoea. Ruiquin et all, in a recent paper published on Transl Neuroscion 2015, examined the effects of chronic intrathecal infusion of DEX on paw withdrawal threshold (PWT) to mechanical stimulation as well as the concentrations of substance P and CGRP within the dorsal horn of the spinal cord of rats.
In conclusion, modern pain management in the ICU should not only address acute pain, but also aim to prevent the development of CPIP and on-going opioid use. So far, no single medication or technique has been proven as most elective in either acute management within ICU or as a preventative measure for the development of CPIP. Pharmacological strategies should involve the lowest possible dose of opioids that is still elective. Analysis of genetic polymorphisms can identify responders to particular medications and a patient’s response to treatment, providing personalised pain management in the intensive care.