Laser therapy or photobiomodulation (PBM) continues to provide solutions/options for many intractable conditions. With September’s focus on pain, we wanted to highlight PBM’s analgesic effects.
The emphasis on managing pain in our veterinary patients has increased substantially especially in the last 8-10 years. Pain causes clinically relevant behavioral and physiologic changes which are detrimental to patient recovery. There are numerous pharmacologic and non-pharmacologic mechanisms for controlling pain with growing emphasis on minimizing pharmacologic intervention thru multimodal protocols. This has reached a critical level of focus particularly on the human side due to the explosive opioid crisis. On October 11, 2018, Congress held its first-ever briefing on ending opioid use through innovative medical technologies for pain management, with PBMT being the featured technology. As our knowledge base increases and the stigma comes down, PBM is becoming a more readily presented option.
Healing begins at the cellular level. Cellular chromophores within the blood stream and the mitochondria absorb the laser energy. Specifically, it is water (peak at 970-980 nm), hemoglobin (peak at 904-915 nm), and cytochrome-c-oxidase (peak at 790-830 nm) that are being targeted. This causes an improved efficiency of the respiratory chain leading to an increased synthesis of ATP. In addition, reactive oxygen species and NO and SOD are produced and there is a shift in the redox state. A cascade of secondary effects can then take place including DNA and RNA synthesis; activation of fibroblasts, macrophages, and lymphocytes; growth factor release; neurotransmitter release; vasodilation; collagen synthesis; improvement of cell membrane permeability and function of the Na+/K+ pump. Increased metabolic activity will increase oxygen and nutrient availability which leads to enhanced protein and enzyme production. These factors will accelerate/stimulate cell reproduction and growth which leads to faster repair of damaged tissues, moderate the inflammatory response, and provide analgesia.
These cellular reactions result in three major clinical benefits for the patient: pain reduction; inflammation reduction including swelling, edema, and bruising; and accelerated and improved tissue healing. These events happen simultaneously and naturally complement each other.
Inflammation is a result of both vascular and cellular consequences. Photobiomodulation ‘moderates’ inflammation by the following mechanisms. There is production of NO along with other mediators which stimulate vasodilation. This facilitates removal of cellular debris along with activation of the lymphatic drainage channels. But more importantly it reduces ischemia and all the negative events associated with a negative oxygen balance in tissue. Angiogenesis is stimulated as well which increases oxygen and nutrient transport to improve tissue repair and therefore reduce inflammation. Production of ROS and SOD helps stabilize cellular membranes and balance the detrimental effects of free radical activity, respectively. Enhanced WBC activity aids the removal of cellular debris. Lymphocyte activity is mediated to give a beneficial response between the T-helper and T-suppressor cells. There is increased production of PGI2 which has anti-inflammatory activity similar to other COX inhibitors. At the same time, there is a reduction in Interleukin-1 and other pro-inflammatory cytokines.
Reducing inflammation will have a measurable effect on the level of analgesia. There is also direct pain relief especially with the higher dosed regimens. Release of endogenous endorphins and opioids both locally and centrally is stimulated. Laser irradiation suppresses the depolarization of the afferent C-fibers. It helps restore the action potential of the damaged nerve back to the normal healthy level of ~70mV thereby increasing the stimulus needed to produce a painful response. (This relates to our attention to pre-emptive analgesia and preventing the “wind-up” effect.) There is a reduction in bradykinin levels. Axonal sprouting and nerve regeneration will occur and will alleviate the pain associated with the damaged tissue. In addition, the accelerated repair process in general will reduce pain sensitivity related to structural stress and imbalance.
All the afore mentioned mechanisms that help reduce inflammation, stimulate angiogenesis and vasodilation, and aid in clean-up of cellular debris, will also increase oxygen and nutrient transport to the area to accelerate and improve tissue repair. Increased ATP production will accelerate cellular function including growth and reproduction. Fibroblast proliferation and collagen synthesis is enhanced and more organized which leads to a reduction of scar tissue and improved tensile strength. There is more rapid epithelialization. Cellular differentiation and maturation increase the number of osteoblasts, myofibroblasts, and other muscle regenerating precursors. Laser therapy can reduce healing times by 30%-50%. It is not just faster healing; it’s better healing! It is this direct stimulation of tissue repair, regeneration, and remodeling that is unique to laser therapy. And this is why we are improving or resolving conditions that were traditionally less responsive before laser therapy was added to our current treatment regimens. And this is why we can manage or resolve many painful conditions.
Our goal for “pain management” is not to just make the more patient comfortable. We want to get the patient back to their normal activity and/or performance level; restore ROM and improve muscle strength and function; reduce the potential for re-injury; and become an active member of the family again. With the proper therapeutic laser in your armamentarium, you have the best chance of achieving these goals.