Fluorescein transit test time as a tool to assess lacrimal pump function after diode laser transcanalicular dacryocystorhinostomy and external dacryocysto-rhinostomy.

BACKGROUND: Dacryocystorhinostomy (DCR) is the gold standard surgical treatment for nasolacrimal duct obstruction. External DCR is the traditional approach (EXT-DCR); however, the advent of minimally invasive surgeries and the development of optic fiber and laser technologies have made it possible to perform laser transcanalicular DCR (T-DCR), a minimally invasive procedure. This study measured the fluorescein transit time (FTT) after EXT-DCR or T-DCR to evaluate the lacrimal drainage and lacrimal pump function after these two types of DCR. SUBJECTS AND METHODS: A cross-sectional study of 50 patients who underwent EXT-DCR (EXT-DCR Group) or T-DCR (T-DCR Group), who were anatomically patent upon irrigation, with a minimum 6 months of follow up. The patients' FTT was measured; it was defined as the time from the instillation of the dye into conjunctival sac to its free flow from the rhinostomy site. This evaluation was performed through nasal endoscopy performed intranasally with a blue filter that enabled the faster detection of fluorescein from the ostium site. The mean FTTs of the two groups were compared using the two-sided Student's unpaired t-test. Other variables such as sex, age, previous lacrimal sac size, and the site and shape of the rhinostomy were evaluated to determine their possible relationships with FTT. RESULTS: The EXT-DCR group had 80% female patients at a mean age of 58 years. The T-DCR group had the same percentage of female patients (80%) and a mean age of 56 years. The mean FTT group was 47.48 sec in the EXT-DCR and 33.04 sec in the T-DCR group. Functional success was 88% in both groups. CONCLUSION: FTT in the DCR-T Group was significantly lower than in the EXT-DCR Group. No other variables exhibited a statistically significant correlation with FTT. Lacrimal drainage was found to be better after T-DCR than after EXT-DCR, results which show that this procedure could prevent lacrimal pump damage.

Metamizol, a non-opioid analgesic, acts via endocannabinoids in the PAG-RVM axis during inflammation in rats.

The most commonly used drugs against pain act by inhibiting the cyclooxygenases (COXs). Metamizol (dipyrone) inhibits the COXs and is widely used in Europe and Latin America as a non-opioid analgesic. One target of metamizol and other non-opioid analgesics is the periaqueductal grey matter (PAG), where they trigger descending inhibition of spinal nociceptive transmission. Also, cannabinoids exert an analgesic action at several structures in the peripheral and central nervous system, including the PAG. The present study investigates whether the antinociceptive action of metamizol in the lateral-ventrolateral (LVL) PAG during inflammation is related to endocannabinoids. In anaesthetized rats, unitary action potentials were recorded from spinal nociceptive neurons with receptive fields in the ipsilateral hind paw. Inflammation of the paw induced neuronal hyperexcitability, which was attenuated by intra-LVL-PAG microinjection of metamizol either at the beginning of inflammation or when hyperexcitability was fully established. In both cases, the antinociceptive effect of metamizol was reduced by a microinjection of AM251, an antagonist at the CB1 cannabinoid receptor, either into the LVL-PAG or into the rostral ventromedial medulla (RVM). The RVM is a downstream structure that funnels PAG-derived descending inhibition into the spinal cord. These results show that endocannabinoids and their CB1 receptor (1) contribute at the LVL-PAG to the antinociceptive effects of metamizol, and possibly other non-opioid analgesics; and (2) participate in the PAG-derived activation of RVM descending antinociceptive influences.