Red Light Therapy for Postoperative Pain: Scientific Evidence

Researchers evaluated whether photobiomodulation therapy (PBMT) could reduce pain in the early hours after nasal septum surgery in an observational study published in 2021. The study enrolled 62 patients (40 men, 22 women, aged 18 to 44 years) divided into 2 groups, with the PBMT group receiving 890 nm infrared pulsed laser at 3, 6, and 24 hours after surgery over the wings of the nose, followed by 630 nm intranasal light at 8 mW for 2 minutes after nasal packing removal at 48 hours, while the no-PBMT group received no light treatment. Pain was measurably lower in the PBMT group than the no-PBMT group from 6 to 24 hours after surgery (P<0.001), and stress responses measured by heart rate patterns were also lower in the PBMT group. These findings suggest PBMT may help reduce both pain and the body's stress response in the early recovery period after nasal septum surgery.

When low-level laser therapy (LLLT) was tested against control and placebo groups in a randomized controlled trial published in 2020, both laser doses were associated with lower pain scores and better overall recovery perception after cesarean section. 88 women were randomly assigned to 4 groups of 22 (control, placebo, LLLT at 4 J/cm2, and LLLT at 2 J/cm2), with the laser groups receiving 660 nm light at an irradiance of 470 mW/cm2 applied to the cesarean incision in a single session immediately after birth. By 44 to 48 hours after birth, both laser groups showed measurably better pain scores and pain sensitivity than the control and placebo groups. No significant difference in outcomes was found between the 2 J/cm2 and 4 J/cm2 doses, suggesting either may be similarly effective.

Pain was significantly lower in the laser group than the control group across all 6 measurement points over 24 hours in a randomized, double-blind observational study published in 2018 on postoperative pain after elective cesarean section. 80 patients were randomly assigned to 2 groups of 40, with the laser group receiving low power laser therapy using 2 wavelengths of light (804 nm and 650 nm) applied to the surgical incision at the end of surgery at a fluence of 1 to 2 J/cm2 and irradiance of 100 to 200 mW/cm2. The laser group also used significantly less total pain medication and waited longer before needing their first dose compared to the control group. The therapy was described as safe and non-invasive by the authors.

In 2018, a randomized, triple-blind, placebo-controlled trial examined whether a single session of photobiomodulation therapy (PBMt) applied shortly after hip replacement surgery could reduce pain and inflammation. 18 patients were divided into 2 groups of 9 and received either active or placebo PBMt using a 9-diode device combining 905 nm, 875 nm, and 640 nm light at 40.3 J per point across 5 sites along the hip incision, 8 to 12 hours after surgery. Pain scores and 2 markers of inflammation were significantly lower in the active group compared to placebo, though a third marker showed no significant change. Researchers concluded PBMt may be effective at reducing both pain and inflammation in the early hours after hip replacement surgery.

90 volunteers recovering from heart bypass surgery took part in a randomized controlled trial published in 2017, randomly assigned to 3 equal groups (control, placebo, and low-level laser therapy (LLLT)). The laser group received 660 nm light at a fluence of 1.06 J/cm2 and irradiance of 100 mW/cm2 applied to the chest surgery incision for 60 seconds, 5 times per week over 8 days, with all patients followed for 1 month. Lower pain scores during coughing on days 6 and 8 were reported in the laser group compared to both the placebo and control groups, suggesting LLLT may be effective at reducing pain after heart bypass surgery.

Researchers in 2016 compared 4 groups of 30 patients each, control, placebo, low-level laser therapy (LLLT) at 640 nm, and light-emitting diode therapy (LED) at 660 nm for reducing pain during coughing after heart bypass surgery. LLLT was applied to the chest surgery incision at a fluence of 1.06 J/cm2 and LED at 0.24 J/cm2, with pain measured using standardized pain scales at multiple points over 1 month. Both the LLLT and LED groups showed greater reductions in coughing pain on days 6 and 8 compared to the placebo and control groups, with similar results seen in patients with high and normal blood sugar levels. By 1 month, almost no participant in any group reported pain during coughing, and the pain reductions produced by LLLT and LED were comparable to each other throughout the follow-up period.

100 adult patients (84 male, 16 female) who underwent heart bypass surgery through a chest incision took part in a prospective observational study published in 2015 on postoperative pain relief. Each patient received a 980 nm Class IV laser applied at 10 J/cm2 over the 150 cm2 chest wound for 150 seconds once daily for up to 3 days starting 30 minutes after removal of the breathing tube, added to a standard pain medication protocol. Pain scores dropped from 7.31 before treatment to 3.40 by 24 hours, reached 0 by 54 hours in the 40 patients who needed a second dose, and no patient required additional pain medication at any point, leading researchers to suggest Class IV laser may be a useful addition to combined pain management after heart bypass surgery.

A double-blind, placebo-controlled randomized controlled trial published in 2015 evaluated the effect of pulsed high-intensity laser therapy (HILT) on post-mastectomy pain syndrome. The trial enrolled 61 women with a mean age of 53.56 years, randomly assigned to a laser group (30 patients) or a placebo group (31 patients), with the laser group receiving pulsed Nd:YAG HILT at 1064 nm three times per week for 4 weeks over the breast, underarm, and affected arm at a total energy dose of 3000 J, alongside a routine physical therapy program. At 12 weeks after treatment ended, the laser group still showed greater pain reductions, larger shoulder range of motion gains, and improved quality of life than the placebo group, and no side effects were observed during or after treatment.

Patients in the laser group consumed significantly less opioid than the control group (51.62 mg vs 89.28 mg) in a double-blind, placebo-controlled randomized controlled trial published in 2014 on postoperative pain after tibial fracture surgery. The 54 participants were randomly assigned to a laser group or a sham group, with the laser group receiving a combination of low level laser therapy (LLLT) at 808 nm and 650 nm applied to the tibial fracture region, back of the knee, and trigger points on muscles and surgical wounds at the end of surgery, at reported fluence values of 1, 3, 4, 6, and 9 J/cm2 and power outputs of 100 mW and 300 mW. The study reported that the laser group had lower pain scores at 2, 4, 8, 12, and 24 hours after surgery compared to the sham group. It was concluded that LLLT is painless, safe, and noninvasive.

Compared to patients who received intravenous regional anesthesia (IVRA) alone, those who also received gallium-aluminum-arsenide laser therapy (GaAlAs) showed lower pain scores in a double-blinded, placebo-controlled randomized controlled trial published in 2014. The trial enrolled 48 patients undergoing surgical fixation of distal radius fractures and randomly assigned them to 2 groups of 24, with the laser group receiving 808 nm irradiation at 4 J per point for 20 seconds over nerve roots in the neck (C5 to C8) and 0.1 J/cm2 for 5 minutes over the affected arm at an irradiance of 800 mW/cm2, while both groups received the same IVRA protocol using lidocaine. Researchers found that the laser group had significantly lower pain scores during and after surgery, a longer time to first fentanyl request, and used significantly less total fentanyl and pethidine compared to the lidocaine-only group. The authors reported that adding GaAlAs laser to IVRA was safe, with no differences between groups in blood pressure or heart rate.

A narrative review published in 2019 examined the effects of low level laser therapy (LLLT) on pain across a range of surgery types including mastectomy, fracture repair, tonsil removal, birth incision repair, and hernia surgery. The review pooled 559 participants across 10 studies, with wavelengths ranging from 620 to 1400 nm and fluence values including 1.5, 3.8, 4, 6, 8.8, 9, 10, and 10.4 J/cm2 across the included trials. 8 of the 10 trials reported positive effects on postoperative pain while 2 reported no benefit, with effect sizes ranging from 0.13 to 2.77 across the 4 studies that provided enough data to calculate them. The authors suggested LLLT may be an appropriate option for reducing pain after surgery, but noted that the size of the effect varied considerably and called for further research with consistent protocols.