Cryoanalgesia for Arterial Puncture Pain

Pain is a disturbing experience for patients in intensive care units (ICUs). It has deleterious effects on patients' health as it can lead to adverse physiological and psychological consequences. Patients undergo a wide variety of painful, invasive procedures to maintain their lives, such as arterial puncture, tracheal intubation, suctioning, insertion or removal of a chest tube, and wound care. A recent study recorded that the prevalence of pain in the ICU is approximately 31%. Another study reported that pain occurred in 5.0% -31.1% of the patients during the first 6 days of their stay in the ICU. Moreover, other studies have illustrated that the severity of pain increases significantly from the baseline during clinical procedures.

Arterial blood gases analysis is frequently requested for critically ill patients to diagnose and manage their acid-base imbalances and respiratory problems. Insertion of arterial lines for the purpose of repeated sampling is not practiced in many places for lack of monitoring devices or lack of expertise. Thus, arterial blood sampling is inevitable for these patients. Arterial samples can be obtained from different arteries such as the radial, brachial, femoral, axillary, dorsalis pedis, and posterior tibial. Regardless which site is used, all of these arteries have a high nerve supply and require deep needle insertion to access them. Hence, this procedure is usually associated with significant pain.

Managing procedural pain is a challenging task in ICUs as most patients have a reduced level of consciousness (LOC). Thus, they cannot express their pain and suffering, which can be disturbing situations for them that have adverse effects on their health. Therefore, when caring for unconscious patients, procedural pain must be evaluated and alleviated to avoid its physiological complications and prevent more intense pain.

In ICUs, pain management is mainly dependent on pharmacological and nonpharmacological interventions. Several pharmacological interventions are available, such as opioids, non-opioids, and adjunct analgesics. Although these medications are effective and fast, they have many adverse effects, including tolerance, suppression of cough reflexes, respiratory depression, immunosuppression, increased ICU stay, and worse post-ICU patient outcomes, especially for mechanically ventilated patients. Therefore, pharmacological interventions should not be the only option for pain management.

Nonpharmacological interventions are also advocated to minimize patients' pain because they are simple, safe, noninvasive, and inexpensive. They include relaxation techniques, cognitive-behavioral strategies, and biophysical interventions such as massage, pressure, and cutaneous electrical nerve stimulation by heat or cold application.

Cryoanalgesia is one of the most common nonpharmacological interventions. It is based on using low temperatures to produce analgesia or anesthesia. It slows the transmission of pain signals, increases the pain threshold, and provides anesthesia or numbness of the selected skin area. Fortunately, the nerve cells remain intact, allowing the nerves to regenerate and regain their normal function over time. Various cooling modalities can be used, such as ice packs, ice massage, cold water immersion, frozen gel packs, and vapocoolants.

Despite its benefits, prolonged repetitive ice application can lead to damage of the myelinated motor and sensory nerves. The myelin sheath is rich in lipids, and the ice results in the solidification and hardening of these lipids that may lead to the arrest of motor and sensory nerve conduction. It can also cause discomfort, frostbite, shivering, and changes in skin colour such as redness. So, it should be removed if the patient developed new pain, numbness, redness, or paleness of the application site. Cryoanalgesia should not be used for patients with severe hypoxia, traumatic brain injury, peripheral vessel disease, Raynaud's disease, diabetic neuropathy, and patients who are taking aspirin, anticoagulant, NSAID, and vasoactive agent. Additionally, it should be used in caution with people extreme age (infant, children, and elderly) as youngster have a thin layer of skin leading to skin breakdown and the elderly may become less sensitive to pain leading to burning. Moreover, open wound and stomas are among the situations that increase the risk of harm associated with using cold application as subcutaneous and deep tissues are more sensitive to temperature changes.

Cryoanalgesia is fast becoming a popular tool for controlling procedural pain as previous investigations have shown its benefits in decreasing pain during ICU procedures such as chest tube removal. Other researchers recorded its effectiveness in controlling pain associated with procedures involving the use of needles such as intramuscular injection, puncture of hemodialysis fistula, and immunization injection.

Additionally, several studies have investigated the effects of cryoanalgesia on pain during arterial puncture and reported its efficiency. However, empirical research on the effect of cryoanalgesia in reducing unconscious patients' pain remains scarce.