LPT contraindications – some facts and some myths
By Jan Tunér
In early (and, sadly even in recent) publications, several incorrect contraindications of LLLT have been proposed. Most of them have been more or less disposed of, such as pacemakers. It is just stunning to believe that an electrical gadget can be influenced by a ray of light, such as the TV remote control.
Another alleged contraindication is patients with diabetes. So far it has not been claimed that LLLT can cure diabetes, but most certainly LLLT is a very useful tool to treat the side effects of diabetes, such as poor circulation, pain and consequent chronic wounds. Animal studies suggest that diabetic wounds treated with LLLT heal at a level of a non-treated wound in a healthy object [1].
The thyroid gland is another frequently seen contraindication. But never substantiated. Of course, hyperthyroidism could possibly be influenced in a negative way, but then again, LLLT is more of a normalizer than a stimulator. So where is the evidence? And hypothyroidism, then? Well, read this:
Höfling DB, Chavantes MC, Juliano AG, Cerri GG, Knobel M, Yoshimura EM, Chammas MC. Low-level laser in the treatment of patients with hypothyroidism induced by chronic autoimmune thyroiditis: a randomized, placebo-controlled clinical trial. Lasers Med Sci. 2012 Jun 21. [Epub ahead of print]
Chronic autoimmune thyroiditis (CAT) is the most common cause of acquired hypothyroidism, which requires lifelong levothyroxine replacement therapy. Currently, no effective therapy is available for CAT. Thus, the objective of this study was to evaluate the efficacy of low-level laser therapy (LLLT) in patients with CAT-induced hypothyroidism by testing thyroid function, thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb), and ultrasonographic echogenicity. A randomized, placebo-controlled trial with a 9-month follow-up was conducted from 2006 to 2009. Forty-three patients with a history of levothyroxine therapy for CAT-induced hypothyroidism were randomly assigned to receive either 10 sessions of LLLT (830 nm, output power of 50 mW, and fluence of 707 J/cm2; L group, n = 23) or 10 sessions of a placebo treatment (P group, n = 20). The levothyroxine was suspended 30 days after the LLLT or placebo procedures. Thyroid function was estimated by the levothyroxine dose required to achieve normal concentrations of T(3), T(4), free-T(4) (fT(4)), and thyrotropin after 9 months of postlevothyroxine withdrawal. Autoimmunity was assessed by measuring the TPOAb and TgAb levels. A quantitative computerized echogenicity analysis was performed pre- and 30 days postintervention. The results showed a significant difference in the mean levothyroxine dose required to treat the hypothyroidism between the L group (38.59 ± 20.22 μg/day) and the P group (106.88 ± 22.90 μg/day, P < 0.001). Lower TPOAb (P = 0.043) and greater echogenicity (P < 0.001) were also noted in the L group. No TgAb difference was observed. These findings suggest that LLLT was effective at improving thyroid function, promoting reduced TPOAb-mediated autoimmunity and increasing thyroid echogenicity in patients with CAT hypothyroidism.
So how about LPT contraindications? Basically, LPT has no serious side effects but it is of course a matter of dosage. One indication that remains to be investigated further is the irradiation over healthy growth plates. The first report came from Cheetham [2] who irradiated the healthy growth plates in young rats. One knee joint of each animal in the experimental group was irradiated three times a week at an energy density of 5 J/cm2. The animals were examined histologically after 6 and 12 applications. There was no difference between the irradiated knee joints, the untreated contralateral knee joint or those in the sham-irradiated control group.
The above seems to be confirmed by de Andreade [3], who writes: The longitudinal growth of long bones is attributed to epiphyseal growth. However, the effect of LPT in such structures has still not been studied extensively in the literature. Therefore, the aim of this study was to evaluate the use of LLLT, 30 mW, 670 nm, at three different doses on the epiphyseal growth of the right tibia of rats. Twenty-one Wistar rats, aged four weeks, were subjected to the application of LLLT, with dosage according to the group (G4: were submitted to the application of 4 J/cm2; G8: were submitted to the application of 8 J/cm2; G16: were submitted to the application of 16 J/cm2). After completion of protocol (ten consecutive days) they were kept until they were 14 weeks of age and then submitted to a radiological examination (evaluation of limb length) and euthanised. The histological analysis of the growth plates (total thickness and hypertrophic and proliferative zones) was then performed. Comparisons were made with the untreated left tibia. No differences were observed in any of the reviews (radiological and histological), when comparing the right sides (treated) to the left (untreated). It was concluded that the treatment with LLLT within the parameters used caused changes neither in areas of the epiphyseal cartilage nor in the final length of limbs.
But energy and number of sessions play a role, of course. In the following experiment, the rats were irradiated daily for 21 days, and it is no surprise that things do happen, for good and for worse, depending on parameters: To determine the influence of LPT on femoral growth plate in rats, Oliveira [4] used 30 rats, aged 40 days, and divided them into two groups, G1 and G2. In G1 the area of the distal growth plate of the right femur was irradiated at one point using 830 nm, 40 mW, energy density 10 J/cm2. The irradiation was performed daily for a maximum of 21 days. The same procedure was done in G2, but the probe was turned off. Five animals in each group were euthanized on days 7, 14 and 21 and submitted to histomorphometric analysis. In both groups the growth plate was radio graphically visible at all moments from both craniocaudal and mediolateral views. On the 21st day percentage of femoral longitudinal length was higher in G2 than G1 compared to basal value while hypertrophic zone chondrocyte numbers were higher in G1 than G2. Calcified cartilage zone was greater in G1 than in G2 at all evaluation moments. Angiogenesis was higher in G1 than in G2 at 14th and 21st days.
The effects of LPT on rheological factors need to be considered with caution. Laser irradiation increases microcirculation [5] but in fact of this, observations indicate that LPT reduce bleeding after tooth extractions. This appears to be contradictory. The safety of irradiating the blood itself seems to be high, since the method of intravascular blood irradiations has been used in Russia and other countries for decades. One advantage, beside the global stimulation, seems to be increased uptake of pharmaceuticals in the targeted area, leading to lower dosage of pharmaceuticals and reduced risks for side effects from these. So what about LPT for patients on warfarin? Experience indicates that this is a minimal risk and may even be useful for reduction of bleeding. But certainly not a clear recommendation at this stage of knowledge. And patients with haemophilia? Still needing a warning sign due to lack of knowledge.
Summing up: Most of the classical “contraindications” for LPT can be discarded, but those remaining are often depending on the diagnoses and laser parameters used. These are rather caveats than contraindications. One “contraindication” after the other has been dismantled, but this does not automatically mean that there are none. In a forthcoming edition of the Annals we will discuss another suggested contraindication – light sensitivity.
References:
[1] Al-Watban F A. Laser Therapy Converts Diabetic Wound Healing to Normal Healing. Photomed Laser Surg. 2009; 27 (1): 127-135.
[2] Cheetham M J, Young R S, Dyson M. Histological effects of 820 nm laser irradiation on the healthy growth plate of the rat. Laser Therapy 1992; 4 (2): 59-64.
[3] de Andrade A R, Meireles A, Artifon E L, Costa Brancalhão R M, Ferreira J R L, Flor Bertolini G R. The Effects of Low-Level Laser Therapy, 670 nm, on Epiphyseal Growth in Rats. ScientificWorldJournal. 2012 : 231723. PMCID: PMC3361141
[4] Oliveira S P, Rahal S C, Pereira E J, Bersano P R, Vieira Fde A, Padovani C R. Low-level laser on femoral growth plate in rats. Acta Cir Bras. 2012; 27 (2): 117-122.
[5] Schaffer M, Bonel H, Sroka R et al. Effects of 780 nm diode laser irradiation on blood microcirculation: Preliminary findings on time-dependent T1-weighted contrast-enhanced magnetic resonance imaging (MRI). J Photochemistry and Photobiology B: Biology. 2000; 54 (1): 55-60.