Effects of a medetomidine-ketamine combination on Schirmer tear test I results of clinically normal cats

Effects of intramuscular alfaxalone and dexmedetomidine alone and combined on ocular, electroretinographic, and cardiorespiratory parameters in normal cats

Background

This study aimed to determine the effects of intramuscular (IM) administration of alfaxalone with or without dexmedetomidine on short electroretinography (ERG), ocular parameters and cardiorespiratory in healthy cats.

Methods

Eight healthy female spayed cats were treated with three sedation protocols: IM administration of 5 μg/kg dexmedetomidine (DEX), 5 mg/kg alfaxalone (ALF), and 5 μg/kg dexmedetomidine plus 5 mg/kg alfaxalone (DEX + ALF). The washout period after each treatment was 2 weeks. Physiological parameters, time metrics, intraocular pressure (IOP), Schirmer tear test 1 (STT-1) and a short ERG protocol were recorded. For age data, weight data, time metrics and ERG data, one-way ANOVA with Bonferroni posterior comparisons were performed. For physiological parameters, IOP and STT-1 data, two-way repeated measures ANOVA with Bonferroni posterior comparisons were performed. Statistical significance was set at a p-value <0.05.

Results

IOPs were increased in all three groups compared to baseline and showed no significant differences among three groups at any time point. STT-1 values were decreased significantly during the process. Significant differences were noticed between a-wave amplitude in the dark-adapted response between DEX and ALF, and a-wave amplitude in light-adapted response between ALF and DEX + ALF.

Conclusion

This study demonstrates the feasibility of three sedation protocols for short ERG recording in cats. All these treatments resulted in increased IOP values and reduced STT-1 values. But baseline data of ERG was not obtained as a blank control in cats.

A Comparison of the Intrarectal and Intramuscular Effects of a Dexmedetomidine, Ketamine and Midazolam Mixture on Tear Production in Cats: A Randomized Controlled Trial

Cats are often easily stressed and uncooperative. The use of sedative agents in the feline species is widely used to perform even minor clinical and diagnostic procedures. The aim of this study is to assess the impact on tear film production of the intrarectal route (IR) administration of a mixture of dexmedetomidine, ketamine and midazolam in comparison with the intramuscular (IM) one. A group of twenty cats were involved in a randomized and blinded clinical trial. A clinical and ophthalmological examination was conducted on the cats. The IR group received dexmedetomidine 0.003 mg kg-1, ketamine 4 mg kg-1 and midazolam 0.4 mg kg-1; the IM group received dexmedetomidine 0.003 mg kg-1, ketamine 2 mg kg-1 and midazolam 0.2 mg kg-1. A Shirmer tear test I (STT- I) was conducted 1 h before sedation and 2', 10', 20', 30', 40', and 80' post drug administration. The reaction to STT-I administration was also evaluated. The IM group has a lower mean tear production than the IR group for all time points evaluated. Cats in the IM group showed less reaction to STT-I administration. This study may suggest that the effect of sedative agents administered by the IR route has a lower incidence on tear production than the IM one. The use of eye lubricant is recommended in any case.

TFOS lifestyle: Impact of societal challenges on the ocular surface

Societal factors associated with ocular surface diseases were mapped using a framework to characterize the relationship between the individual, their health and environment. The impact of the COVID-19 pandemic and mitigating factors on ocular surface diseases were considered in a systematic review. Age and sex effects were generally well-characterized for inflammatory, infectious, autoimmune and trauma-related conditions. Sex and gender, through biological, socio-economic, and cultural factors impact the prevalence and severity of disease, access to, and use of, care. Genetic factors, race, smoking and co-morbidities are generally well characterized, with interdependencies with geographical, employment and socioeconomic factors. Living and working conditions include employment, education, water and sanitation, poverty and socioeconomic class. Employment type and hobbies are associated with eye trauma and burns. Regional, global socio-economic, cultural and environmental conditions, include remoteness, geography, seasonality, availability of and access to services. Violence associated with war, acid attacks and domestic violence are associated with traumatic injuries. The impacts of conflict, pandemic and climate are exacerbated by decreased food security, access to health services and workers. Digital technology can impact diseases through physical and mental health effects and access to health information and services. The COVID-19 pandemic and related mitigating strategies are mostly associated with an increased risk of developing new or worsening existing ocular surface diseases. Societal factors impact the type and severity of ocular surface diseases, although there is considerable interdependence between factors. The overlay of the digital environment, natural disasters, conflict and the pandemic have modified access to services in some regions.

Effect of 0.15% sodium hyaluronate on tear film breakup time in healthy anesthetized cats

OBJECTIVES

This study aimed to evaluate the effect of 0.15% sodium hyaluronate (SH) on tear film breakup time (TFBT) in healthy anesthetized cats.

PROCEDURES

Forty cats undergoing elective surgery were enrolled. TFBT was assessed before anesthesia to obtain baseline values. As a preanesthetic medication, cats received midazolam, tramadol, and cetamine combined in the same syringe. For anesthetic induction and maintenance, propofol and isoflurane were used. After a 15 min stabilization period to achieve the surgical anesthetic plane, one eye was treated with one drop of SH, while the other eye received saline and served as a control. TFBT was measured at the end of the general anesthesia (T40) and 35 (T75) and 80 min (T120) after the termination of the anesthesia. TFBT values were compared between the control and SH-treated eyes; both values were also compared with the baseline values (p < .05).

RESULTS

In the control eyes, TFBT significantly decreased from baseline at all time points (p < .001), while in SH-treated eyes, TFBT significantly increased from baseline only at T40 (p < .0001). In SH-treated eyes, TFBT was significantly higher than that in the control eyes at all time points (p < .001).

CONCLUSIONS

In healthy cats, TFBT decreases significantly after 40 min of general anesthesia, and one drop of 0.15% sodium hyaluronate was able to maintain the stability of the tear film for up to 75 min in treated eyes. However, the isolated effect of each drug used in our anesthetic protocol on TFBT should be executed in further studies.

Levobupivacaine Combined with Cisatracurium in Peribulbar Anaesthesia in Cats Undergoing Corneal and Lens Surgery

The aims of the study included evaluating the effects of levobupivacaine combined with cisatracurium on akinesia and mydriasis when administered by peribulbar injection, and evaluating if the chosen dose of cisatracurium is enough to avoid the use of systemic neuromuscular blockade in cats. The animals were divided into four groups as follows: group L received 1.25 mg kg^-1 levobupivacaine administered by peribulbar injection; group LC received the same dose of levobupivacaine combined with 0.01 mg kg^-1 of cisatracurium administered by peribulbar injection; group C received 0.01 mg kg^-1 of cisatracurium administered by peribulbar injection; group GC received 0.01 mg kg^-1 of cisatracurium intravenously. Physiological variables, intraocular pressure, akinesia, and mydriasis were measured before and up to 30 min after peribulbar injection. The onset of akinesia, duration of akinesia, and train of four (TOF) were evaluated. Physiological variables remained in the physiological range in all groups. Effective akinesia and mydriasis were observed in all groups. The (TOF) was 0.9 in all groups. Throughout the study was observed in group LC a shortened onset of akinesia and a prolonging its duration. The peribulbar injection of cisatracurium and levobupivacaine provided effective akinesia and mydriasis, and shortened the onset of akinesia while prolonging its duration.

Ophthalmic effects of dexmedetomidine, methadone and dexmedetomidine-methadone in healthy cats and their reversal with atipamezole

OBJECTIVES

The aims of this study were to evaluate and compare the effects that dexmedetomidine and methadone, either alone or in combination, have on the ocular variables of healthy adult cats when administered intramuscularly, as well as their reversal with atipamezole.

METHODS

A randomized crossover blinded study of 10 healthy cats was used to assess the effect of 0.2 mg/kg methadone (MET), 7.5 μg/kg dexmedetomidine (D7), 10 μg/kg dexmedetomidine (D10), 7.5 μg/kg dexmedetomidine and 0.2 mg/kg methadone (DM7) and 10 μg/kg dexmedetomidine and 0.2 mg/kg methadone (DM10) on intraocular pressure (IOP), tear production and pupil diameter (PD). The animals were evaluated for 30 mins. Afterwards, atipamezole was administered and ocular variables were evaluated for 30 mins.

RESULTS

D10, DM7 and DM10 significantly decreased mean IOP but MET or D7 did not. Tear production decreased significantly in all treatments, corresponding to 18%, 59%, 63%, 86% and 98% in MET, D7, D10, DM7 and DM10, respectively. PD increased in all treatments, but MET showed the highest PD. Thirty minutes after atipamezole (RT30), IOP returned to baseline with no difference between groups, and there was a significant increase in tear production, but the means were still different from baseline.

CONCLUSIONS AND RELEVANCE

Dexmedetomidine decreases IOP and tear production but increases PD in healthy cats. Atipamezole can partly reverse those alterations. Low-dose dexmedetomidine (7.5 µg/kg) promotes sedation without changing the IOP. All protocols significantly decrease tear production, and Schirmer tear test after sedation is not representative of non-sedated values. Methadone induces quick onset mydriasis without changing the IOP.

Hospitalization disrupts the daily rhythm of tear production in cats

OBJECTIVE

The exposure to constant light during the hospitalization was investigated to verify its influence on the daily rhythmicity of Schirmer tear test I (STT I) in the Felis catus.

ANIMAL STUDIED

One group (HG-hospitalized group) was consisted of 10 owned-cats hospitalized to perform a sterilization procedure and was exposed to a 24/0 light/dark (L/D) cycle; the cat control group (CG) was consisted of 10 staff-owned cats living in an indoor environment (12/12 L/D cycle).

PROCEDURE

The STT I values was performed at 4 h intervals over a 48 h period (starting at 8:00 a.m. on Day 1 and finishing at 8:00 a.m. on Day 3) on the left (LE) and right (RE) eyes into two cat groups. A 35 x 5 mm commercial tear test strip was used to record tear production in millimeters wetting per minute (mm/min).

RESULTS

Multivariate for repeated measure analysis of variance (ANOVA) showed a statistically significant effect of time. No difference was found between LE and RE tear production, and between the two experimental conditions. Robust daily rhythmicity was exhibited by the STT I in both eyes during the entire monitoring period in control cats and only during the Day 1 in hospitalized cats.

CONCLUSIONS

These data are a starting point for evaluating the imbalance of ocular physiology observed in hospitalized cats. Further studies on larger sample size and exposing the animals to various hospitalization procedures are needed to establish whether these alterations are caused by hospitalization procedures or by the light/dark schedules.

Influence of Fentanyl, Ketamine, and Lidocaine on Tear Production in Healthy Conscious Dogs

Tear production is an important factor in maintaining proper function of the cornea and conjunctiva. The purpose of this study was to determine the effects of bolus followed by infusion of fentanyl, lidocaine, and ketamine on tear production as measured by the Schirmer I Tear Test (STT-I) in dogs. A prospective, randomized, "double-blind" study was performed. A total of 55 healthy conscious client-owned dogs were included in the study. Dogs were randomly allocated to one of four groups and given intravenous fentanyl 0.005 mg kg^-1 followed by 0.005 mg kg^-1 hour^-1 (FEN-group), ketamine 0.6 mg kg^-1 followed by 0.6 mg kg^-1 hour^-1 (KET-group), lidocaine 1 mg kg^-1 followed by 1 mg kg^-1 hour^-1 (LID-group), or saline 0.3 mL kg^-1 followed by 2 mL kg^-1 hour^-1 (SAL-group). The STT-I was performed prior to (baseline) and again 30 minutes (T30) after initiation of drug administration. Data were expressed as the median (minimum - maximum) and analyzed by Wilcoxon and Steel-Dwass tests (P < .05). The STT-I values increased little but were statistically significant in the KET-group from 18 (14-23) to 19 (14-25) (P = .039) and in the LID-group from 21 (14-25) to 20 (17-29) (P = .027). At 30 minutes, STT-I values were significantly higher in LID-group 20 (17-29) than in FEN-group 18 (12-22) (P = .006). Fentanyl, ketamine, and lidocaine administered at the studied doses as a bolus and then followed by an infusion within 30 minutes in healthy conscious dogs demonstrated a clinically insignificant effect on tear production as measured by STT-I.

Evaluation of Tear Production as Measured by Schirmer Test I in Dogs after Acepromazine and Acepromazine-Methadone Premedication

Simple Summary

Different sedatives and anesthetic drugs have been reported to cause adverse ocular side effects, such as an exposure keratopathy due to loss of eyelid reflex, lagophthalmos, reduced stability of the tear film and decreased basal tear production. In the present study, the effects of two sedation protocols, acepromazine (ACP) and acepromazine–methadone (ACP–MET) combination, on tear production measured by the Schirmer Tear Test (STT) 1 on canine eyes were investigated, hypothesizing that both sedation protocols cause a reduction in canine tear production for a variable time. A significant decrease in tear production until 2 h after drug administration compared to basal tear values was observed in the ACP experimental protocol, while in the ACP + MET protocol, this reduction persisted until 8 h. In the ACP + MET group, after 40 min, 100% of dogs showed STT 1 readings lower than 15 mm/min, which could predispose them to corneal injuries. The major reduction in tear production due to the ACP + MET protocol proves the need for adequate corneal hydration, particularly to discourage its use in animals with altered tear production.

Abstract

The purpose of the current study was to investigate the effects of two commonly used sedation protocols in dogs, acepromazine (ACP) and acepromazine–methadone (ACP–MET) combination, on tear production measured by the Schirmer Tear Test (STT) 1. We hypothesized that both sedation protocols cause a reduction in canine tear production for a variable time. Fifteen client-owned dogs were recruited for the study. Each dog was subjected to sedation twice, 2–3 weeks apart, and they were randomly allocated to one of two groups receiving ACP (0.015 mg kg⁻¹) or ACP–MET (0.010 mg kg⁻¹ and 0.2 mg kg⁻¹) intramuscularly. In both eyes, tear production was measured 15 min before sedation (T0) and 20 min (T20 m), 40 min (T40 m), 1 h (T1), 2 h (T2), 4 h (T4) and 8 h (T8), after drug administration. Two-way repeated measures ANOVA, followed by the Bonferroni post hoc test (p < 0.05), showed a significant effect of time (p < 0.0001) and treatment (p < 0.0001). A significant decrease in tear production at T20 m, T40 m, T1 and T2 compared to T0 was observed in the ACP experimental protocol, while in the ACP + MET protocol, this reduction persisted until T8. Comparing the two experimental protocols, no statistically significant differences were observed at T0 or T20 m, and STT 1 values were statistically lower in the ACP + MET than the ACP protocol at the other data points. In the ACP + MET group, at T40 m, 100% of dogs showed STT 1 readings lower than 15 mm/min. This finding is clinically relevant as it can predispose dogs to corneal injuries. The major reduction in tear production due to the ACP + MET protocol proves the need for adequate corneal hydration, particularly to discourage its use in animals with altered tear production. The data obtained provide important information helping clinicians to better manage the drug’s effects on tear production.

FACTORS AFFECTING TEAR PRODUCTION AND INTRAOCULAR PRESSURE IN ANESTHETIZED CHIMPANZEES (PAN TROGLODYTES)

Measurements of intraocular pressure (IOP) and tear production are key components of ophthalmic examination. Chimpanzees (Pan troglodytes) were anesthetized using either tiletamine-zolazepam (TZ; 2 mg/kg) combined with medetomidine (TZM; 0.02 mg/kg), or, TZ alone (6mg/kg). Tear production was lower (P = 0.03) with TZM (5.63 ± 6.22 mm/min; n = 16) than with TZ (11.13 ± 4.63 mm/min; n = 8). Mean IOP, measured using rebound tonometry in an upright body position (n = 8) was 18.74 ± 3.01 mm Hg, with no differences between right and left eyes. However, positioning chimpanzees in left lateral recumbency (n = 27) resulted in higher IOP in the dependent (left) eye (24.77 ± 4.49 mm Hg) compared to the nondependent (right) eye (22.27 ± 4.65 mm Hg) of the same animal (P < 0.0001). These data indicate medetomidine anesthesia markedly lowers tear production in chimpanzees, and that body position should be taken into consideration when performing rebound tonometry.

Effects of Medetomidine, Dexmedetomidine and their combination with Acepromazine on the intraocular pressure (IOP), tear secretion and pupil diameter in dogs

Background

A great number of sedatives and anaesthetics have been used to perform surgeries or routine ophthalmologic examinations in animals and sometimes the combination of these medicines has more suitable effects than each one alone.

Objectives

This paper aims to explore the main effects of Medetomidine + Acepromazine, Dexmedetomidine + Acepromazine on intraocular pressure, tear secretion and pupil diameter.

Methods

To accomplish the aforementioned aim, 32 adult dogs (aged one‐to‐three‐years‐old) were clinically examined. Dogs were divided into four groups consisting of group DA, Dexmedetomidine (5 µg/kg) + Acepromazine (0.05 mg/kg); Group D, Dexmedetomidine (5 µg/kg); Group M, Medetomidine (10 µg/kg); Group MA, Medetomidine (10 µg/kg) + Acepromazine (0.05 mg/kg). The ocular factors including tear production, pupil diameter and intraocular pressure of both right and left eyes were first measured and then recorded in each dog at time T₀ (−15 min). Afterwards, the drugs were administered intramuscularly, based on which the ocular factors were re‐measured at T₁ (+5 min), T₂ (+15 min) and T₃ (+20 min). All four groups showed a reduction in intraocular pressure, which was significant in DA, D and M groups.

Results

Furthermore, there was a fluctuation in the amount of tear secretion in DA and D groups (increase and then decrease), as well as a significant reduction in M and MA groups. Decreasing in pupil diameter also occurred in all four groups, but the reduction was significant only in DA and MA groups.

Conclusion

According to the results obtained, as the changes caused by the systemic administration of the above drug compounds did not exceed the physiological range, it can be concluded that these combinations could be utilized as suitable sedatives or pre‐anaesthetic compounds in the eye surgeries.

Dexmedetomidine and Tear Production: Evaluation in Dogs as Spontaneous Model for Ocular Surface Disorders

Simple Summary

The general anesthesia or sedation reduces both the tear production and the stability of tear film that protect corneal surface, predisposing itself to the exposure keratopathy. The aim of the present study was to evaluate the effects of intramuscular dexmedetomidine (DEX) on canine tear production, measured by standardized Schirmer Tear Test 1 (STT-1) strips, for the 8 h following sedation, in dogs. A significant effect of time on canine tear production was found, highlighting that dexmedetomidine sedative protocol significantly affects tear production in dogs. It is recommended to treat the canine eyes with tear substitutes to protect ocular surface health and the welfare of the dogs. The ocular lubrication should be performed during and up to 12 h after sedation. The present report could provide preliminary information to better understand the effect of DEX on the tear film dynamics.

Abstract

Tear film provides lubrication and protection to the ocular surface. The sedation reduces tear production, often leading to perioperative exposure keratopathy. The aim of the present study was to report the effects of intramuscular dexmedetomidine on canine tear production, measured by STT-1, for an experimental period of 8 h after sedation. Ten dogs who underwent sedation for routine radiologic assessment were recruited for the study. In all animals, tear production in right and left eyes was measured 15 min before sedation (T0: basal values) and 20 min (T20), 1 h (T1), 2 h (T2), 4 h (T4) and 8 h (T8) after drug administration. Analysis of variance and post hoc Bonferroni test (p < 0.05) were performed. A significant effect of time on canine tear production was found. The tear production returned to basal values at T8. So, it is recommended to treat the canine eyes with tear substitutes during and up to 12 h after sedation.

Schirmer Tear Test Value and Corneal Lesions' Incidence during General Anesthesia for Non-Ophthalmic Surgery in Non-Brachycephalic Dogs: A Pilot Study Comparing Three Different Lubricant Eye Drop Formulations

Aim of this blinded, prospective, randomized clinical study was to compare three different lubricant eye drops (LED) in healthy adult dogs undergoing general anaesthesia (GA) for non-ophthalmic surgery. Tear production rate was monitored by means of Schirmer tear test-1 (STT-1), and incidence of post-operative corneal abrasions/ulcerations was detected by corneal staining. A complete ophthalmic examination was performed before premedication, at extubation time and 24 h after GA in twenty-five non-brachycephalic dogs (fifty eyes) undergoing elective orthopaedic or spinal surgery procedures. Dogs were randomly allocated to one of three groups receiving as prophylactic LED either carmellose sodium (GC), or 1% hyaluronic acid (GH), or 0.25% hyaluronic acid (GL). In each eye STT-1 was repeated every hour during GA, before instilling one drop of the assigned LED. In all groups STT-1 values drastically decreased during GA, while 24 h later nine eyes (18%) had STT-1 values lower than 15 mm/minute. All of the three formulations tested were fully effective in preventing corneal ulceration (0% in all groups), while 10% of eyes reported superficial de-epithelialization. Fluorescein staining demonstrated that hourly prophylactic LED application prevented exposure keratopathy during general anesthesia in 90% of the eyes in non-brachycephalic dogs.

Effect of intramuscular administration of medetomidine and xylazine on tear flow measured by the Schirmer tear test I in healthy cats

OBJECTIVES

This study aimed to investigate the effects of intramuscular medetomidine and xylazine on tear flow in healthy cats.

METHODS

Five cats each received medetomidine 10, 20, 40 and 80 µg/kg IM; xylazine 1.0, 2.0, 4.0 and 8.0 mg/kg IM; and physiological saline (2.0 ml IM) in a randomised order separated by intervals of at least 1 week. The Schirmer tear test (STT) I was performed in both eyes before and 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6, 7, 8 and 24 h after each dose.

RESULTS

The STT I value decreased significantly at 0.5 and 1.0 h and at 0.75 and 1.0 h in both eyes after administration of medetomidine at 10 or 40 µg/kg. After administration of medetomidine 80 µg/kg, there was a significant decrease in the STT I reading at 0.75, 2 and 3 h in the left eye and 0.75, 1, 2 and 3 h in the right eye. The STT I value decreased significantly at: 0.5, 0.75, 1 and 2 h in the left eye and 0.75 h in the right eye after administration of xylazine 1.0 mg/kg; 0.5, 0.75, 1 and 2 h in the left eye and 0.5, 0.75, 1 and 3 h in the right eye after administration of xylazine 2.0 mg/kg; 0.5, 0.75, 1 and 2 h in both eyes after administration of xylazine 4.0 mg/kg; and 0.5, 0.75, 1, 2 and 3 h in the left eye and 0.75, 1, 2, 3 and 4 h in the right eye after administration of xylazine 8.0 mg/kg.

CONCLUSIONS AND RELEVANCE

Both medetomidine and xylazine significantly decreased feline tear flow measured by STT I. Therefore, the ocular surface should be monitored carefully and protected appropriately in cats treated with these sedatives.

Measurement of tear production and intraocular pressure in conscious captive European fallow deer (DAMA dama)

Normal values for intraocular pressure (IOP) and tear production in conscious cervids have not been reported to date. Based on trends in zoological institutions to perform non-anaesthetized health exams, it is applicable to establish normal values in conscious animals, as anaesthesia and sedation can alter these parameters. The goal of this study was to estimate intraocular pressures using rebound tonometry and measure tear production values in a group of healthy, conscious, European fallow deer utilizing chute restraint. Evaluation of these values with regards to instrumentation and restraint variables will be assessed. Complete ophthalmic examinations, including estimation of IOP with rebound tonometry and measurement of tear production with Schirmer tear tests (STT) were performed on nine conscious European fallow deer (Dama dama) restrained in a chute. Correlations between IOP on the unspecified (P) and the equine (H) settings, as well as IOP and STT differences between left (OS) and right (OD) eyes were evaluated, in addition to assessment of correlations between right and left lateral recumbency on IOP and STT. Tear production measurements were 18.7 ± 5.1 mm min-1 with a 95% confidence interval (CI) range of 16.4-21.1 mm min-1 . Intraocular pressure measurements for the P setting were 16.1 ± 4.5 mmHg with a 95% CI range of 14.1-18.2 mmHg, and for the H setting were 21.5 ± 5.1 mmHg with a 95% CI range of 19.1-23.9 mmHg. No statistically significant difference (P > 0.05) was found between OS and OD in any test. Neither left nor right lateral recumbency was found to have a statistically significant effect on IOP or STT. This study represents the first assessment of ophthalmic parameters in conscious fallow deer with rebound tonometry and STT.