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1040 AJVR, Vol 75, No. 12, December 2014 Comparison of anesthetic efficacy and adverse effects associated with peribulbar injection of ropivacaine performed with and without ultrasound guidance in dogs Juliana T. Wagatsuma, DVM, MSC; Maurício Deschk, DVM, MSC; Beatriz P. Floriano, DVM, MSC; Joana Z. Ferreira, DVM, MSC; Heitor Fioravanti, DVM; Isabela F. Gasparello, DVM; Valéria N. L. S. Oliva, DVM, PhD Objective—To compare the anesthetic efficacy and adverse effects associated with per- ibulbar injection of ropivacaine (1% solution) performed with and without ultrasound guid- ance (UG) in dogs. Animals—15 dogs without ophthalmologic abnormalities. Procedures—Each dog was sedated and anesthetized. A peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) was performed with UG in 1 eye and without UG in the contralat- eral eye (control). For each eye, the intraocular pressure (IOP) immediately after eye central- ization and number of punctures were recorded; ophthalmic complications, postinjection corneal sensitivity (determined by Cochet–Bonnet esthesiometry), durations of the sensory and motor blockades (the latter determined as the interval to restoration of the vestibulo- ocular reflex, pupillary light reflex, and conjugate eye movement), and blockade quality were assessed in both eyes following anesthetic recovery. Results—Needle placement was fully visualized in 8 of the 15 eyes injected with UG. For eyes injected with or without UG, there was no difference with regard to the number of punctures, postinjection corneal sensitivity, and sensory or motor blockade duration and quality; however, restoration of conjugate eye movement occurred later in control eyes. For eyes injected with UG, mean IOP was 18.6 mm Hg, compared with 23.3 mm Hg for control eyes. Incidence of subconjunctival hemorrhage was higher for control eyes; severity of chemosis and hyperemia varied over time within both groups of eyes. Conclusion and Clinical Relevance—In dogs, peribulbar injection of ropivacaine with UG is feasible in dogs and provides effective sensory and motor blockades similar to those achieved with conventional techniques. (Am J Vet Res 2014;75:1040–1048) Received February 6, 2014. Accepted June 9, 2014. From the Department of Animal Clinic, Surgery and Reproduction, College of Veterinary Medicine of Araçatuba (FMVA), São Paulo State University (UNESP), Araçatuba, SP 16050-680, Brazil. Funded by the Foundation for Research Support of the State of Sao Paulo (FAPESP). Address correspondence to Dr. Wagatsuma (jutessalia@yahoo.com. br). To preserve ocular integrity, ophthalmic procedures require specialized anesthetic and surgical condi- tions such as application of sophisticated equipment and techniques, patient immobilization, maintenance of cardiovascular and respiratory variables, and pro- vision of an adequate surgical field.1 To achieve these conditions, intraocular analgesia should result in sen- sory fiber blockade, ocular extrinsic muscle akinesia, oculocardiac reflex blockade, and reduced IOP,2 allow- ing an appropriate postoperative outcome with mini- mal opioid use.3 Retrobulbar and peribulbar blocks are highlighted among the various ophthalmic anesthetic techniques4 such as intracameral5 and subtenonian6 injections, topi- cal anesthesia, infiltrative anesthesia, and anesthesia of the lacrimal, zygomatic, ophthalmic, and auriculopal- pebral nerves,4 because the isolated use of one of these techniques (except the subtenoniana injection) will provide only the sensorial or motor blockade, and the value of the cannula of Greenbaum used in subtenoni- ana anesthesia technique can increase the cost of the procedure, which is high, compared with the cost of with peribulbar or retrobulbar blockade.7 For a retrobulbar block, the anesthetic agent is ad- ministered within the retrobulbar musculature and re- sults in adequate analgesia3 and globe akinesia; a small drug volume is required and yet the time to onset of effects is short.8 However, close contact of the needle ABBREVIATIONS CEM Conjugate eye movement IOP Intraocular pressure PLR Pupillary light reflex UG Ultrasound guidance VOR Vestibulo-ocular reflex 14-02-0030r.indd 1040 11/18/2014 1:32:08 PM AJVR, Vol 75, No. 12, December 2014 1041 with the muscular cone is associated with several risks including intraneural anesthesia of the subarachnoid space, which may induce CNS depression, apnea, and cardiac arrest; IV administration; ocular puncture; and retrobulbar hemorrhage.9 As an alternative to the retrobulbar technique, peribulbar injection of anesthetic agents has been sug- gested. In a peribulbar block, the needle is introduced parallel to the orbital wall or floor and, unlike the retrobulbar block, the anesthetic agent is delivered ex- ternal to the muscular cone. Thus, a peribulbar block is considered a safer method10 because it reduces the risk of injury to the orbital structures such as the op- tic nerve and blood vessels.a The peribulbar technique can be performed by double puncture at the orbit up- per and lower corners11,a,b or by a single puncture at the inferotemporal or superonasal corner.12,a The needle puncture in the inferotemporal aspect is performed at a point situated on the border of the zygomatic arch at the junction between the lateral third and the medial two-thirds; a puncture in the superonasal corner is per- formed between the medial third and the lateral two- thirds.9,11 Results of several human14–17 and 2 animal12,a studies suggest that a single-puncture technique yields adequate drug distribution with a low incidence of oph- thalmic complications.12 However, this technique usu- ally requires a large volume of anesthetic agent as well as additional punctures when analgesia and akinesia were not adequate, which may increase the incidence of complications such as retrobulbar hematoma as well as scleral or ocular perforation.8,17,18 Ultrasound guidance during administration of an anesthetic agent enables real-time visualization of the needle and drug dispersion, thereby improving the quality and safety of the procedure.19 Widely used in human medicine20–23 and promisingly useful in vet- erinary medicine for patients requiring local anesthe- sia,24–31 anesthetic drug delivery with UG has advan- tages over anesthetic drug delivery without UG. The benefits include reduced volume of anesthetic agent, improved therapeutic efficacy,25 and visual confirma- tion of drug deposition.31–33 To our knowledge, the use of ultrasonography during application of ophthalmic anesthetic blocks has been rarely explored, with only a few reports31,33,34 of human studies and 1 report19 of a study evaluating retrobulbar administration in equine cadavers. We are not aware of any studies of the efficacy and safety of an- esthetic agents injected with UG for ocular anesthesia in live animals. On the basis of published data, use of UG during anesthetic agent administration to establish a peribulbar block could be a viable technique in dogs. Therefore, the purpose of the study reported here was to compare the anesthetic efficacy and adverse effects associated with peribulbar injection of ropivacaine (1% solution) performed with and without UG in dogs. Materials and Methods Animals—Fifteen adult dogs (30 eyes evaluated) owned by the university experimental kennel and of multiple breeds, both sexes, and various weights each underwent an ophthalmic examination. The evalua- tions were performed in a specific sequence, as follows: tear production assessment (Schirmer tear testc); basal corneal sensitivity testing (basal esthesiometryd); eye- lid, conjunctival, and corneal inspection (fluorescein stain teste) assisted by artificial light in a dark room; IOP measurement (applanationtonometryf); fundus evaluation (indirect ophthalmoscopyg); and ocular movement (VOR, PLR, and CEM). A CBC, serum bio- chemical analysis, and general physical examination were also conducted. The 15 animals included in the study had not un- dergone ophthalmic surgical procedures and had no ophthalmic disorder; given that evaluation of only their healthy eyes was part of the study, none of those dogs was excluded or replaced. Dogs were excluded from the study if any abnormalities were evident on the initial examination. This study was conducted at the Faculty of Veterinary Medicine of UNESP, Campus of Araça- tuba and was approved by the ethics committee of this institution, concerning the use of animals in animal experimentation. Experimental procedures—Prior to each experi- ment, food and water were withheld from each dog for 12 and 2 hours, respectively. For sedation, aceproma- zine maleateh was administered IM (0.05 mg/kg). After an interval of 20 minutes, a catheter was placed in a cephalic vein to enable IV administration of lactated Ringer’s solution (administration rate, 8 mL/kg/h). Anesthesia was induced with propofoli (5 mg/kg, IV) and maintained via inhalation of isofluranej in oxygen. Throughout the period that the dogs were anesthetized with isoflurane, heart and respiratory rates; esophageal temperature; systolic, diastolic, and mean arterial blood pressures; oxygen saturation as measured by pulse ox- imetry; and fractions of inspired isoflurane and expired carbon dioxide were measured every 5 minutes with a multiparameter monitor.k For each dog, the 2 eyelids (upper and lower) were shaved, and the puncture site was aseptically pre- pared by delicately applying topical iodine solution with a sterile gauze. Each dog was first positioned in right recumbency for the peribulbar blockade with UG Figure 1—Photograph to illustrate transducer positioning relative to the upper eyelid and needle during peribulbar injection of a local anesthetic agent administered by a single puncture ventral to the orbit with UG in an isoflurane-anesthetized dog. The trans- ducer orientation marker points toward the puncture site, and the transducer is angled 45° to 60° relative to the upper eyelid. 14-02-0030r.indd 1041 11/18/2014 1:32:09 PM 1042 AJVR, Vol 75, No. 12, December 2014 and thereafter in left lateral recumbency for peribulbar blockade without UG. Once the dog was stable under general anesthesia, the peribulbar block was performed with UGl via a single lower puncture site. Instead of a transcorneal technique, a trans-eyelid ultrasound tech- nique was used to decrease the risk of corneal injury.35 The transducer was positioned sagittally on the upper eyelid near the optical axis and angled 80° to 90° rela- tive to the globe to allow identification of the eye, bul- bar musculature, and optic nerve. The transducer was then angled at 45° to 60° rela- tive to the upper eyelid, remaining contralateral to the puncture point at the infraorbital floor and with the transducer orientation marker facing the puncture site (Figure 1); with this transducer orientation, the globe, ocular muscles, and optic nerve were simultaneously observed. Once the acoustic window was established, the needlem was introduced through the skin within the lateral third of the lower orbital margin and aligned lengthwise to the ultrasound beam, which allowed vi- sual confirmation of the needle’s real-time peribulbar location. In this moment, a syringe with ropivacainen (1% solution; 0.3 mL/kg) was connected to the needle and the drug was administered and visualized during its deposition; the orbit was then gently compressed for 2 minutes. The dog was then positioned in lateral recumben- cy on the other side of the body, and the axial length of that contralateral eye was measured; its extension was marked directly on the needle shank with a pen to avoid excessive insertion into the socket. The globe was anesthetized via injection of the same volume of ropivacaine used previously but drug administration occurred without UG (control eyes). The injection was performed solely on the basis of the peribulbar block anatomic landmarks, with the needlem introduced into the skin at the lower orbital margin between the lateral third and medial two-thirds. Once the drug was admin- istered, the site was gently compressed for 2 minutes, the dog was kept in sternal recumbency for 20 minutes, and after this time, the anesthetic vaporization was completed. Data collection—For both eyes in each dog, the number of punctures and the IOP immediately after eye centralization were recorded; for eyes injected with UG, the quality of needle visualization was assessed. Once the dog was completely awake (approx 30 minutes after the cessation of isoflurane administration), corneal and motor block durations and the incidence of ophthal- mic complications were also determined. Each dog was evaluated every 30 minutes until the basal esthesiomet- ric value return to baseline and ocular movement re- turned and normalized. All dogs were evaluated by the same evaluators (FBP, JZF) who were unaware which eye was blocked with UG or not. To assess the sensory blockade, corneal sensitiv- ity was assessed with a Cochet–Bonnet esthesiometer; the filament length that induced a positive response indicated by a positive corneal reflex, globe retrac- tion, or third eyelid protrusion in 2 of 3 consecutive assessments was recorded. A 4-cm-long filament was used initially, and the length was reduced in 0.5-cm increments for subsequent assessments until a positive response was elicited. To quantify the duration of the sensory blockade, the interval from the first evaluation after drug administration to when the esthesiometric value returned to the basal value was determined. The intensity of the motor blockade was considered absent, partial, or full on the basis of assessment of each of the cephalic movements: VOR (motor blockade indicated by absence of or decrease in lateral nystagmus during cranial rotation), PLR (motor blockade indicated by mydriasis unresponsive or poorly responsive to light), and CEM (motor blockade indicated by absence of or decreased visual accommodation during cranial move- ment). The interval during which each cephalic move- ment was not normal was recorded individually. Over- all motor blockade duration was the time needed for the motor blockades to become absent as determined on the basis of the VOR, PLR, and CRM. Each dog’s eyes were assessed for ophthalmic com- plications. Hyperemia, chemosis, subconjunctival hem- orrhage, ophthalmic pruritus, tearing, and discharge were classified as absent, light, moderate, or intense; the behavior of these complications over the time was assessed. For statistical analysis, the severities of the ocular complications detected at 30, 60, 180, and 300 minutes after injection of the anesthetic agent and the last moment evaluated were also used. However, be- cause the timing of that last evaluation differed among individuals, the final evaluation time point was not the same for all dogs. Statistical analysis—Data that were not normally distributed or had a high variation coefficient were compared with the Wilcoxon test; normally distributed data were compared with a paired t test. Comparisons over time within each group of eyes were analyzed with the Friedman test, followed by the Dunn test for mul- tiple comparisons. Comparisons over time between the groups of eyes were performed with the Wilcoxon signed rank test. The data were analyzed with computer softwareo; a value of P < 0.05 was considered significant. Results Fifteen dogs were selected and included in the study. There were 8 females and 7 males of various breeds, includingBeagle (n = 8), Labrador Retriever (1), Golden Retriever (1) and mixed-breed dogs (5). The mean ± SD weight was 13.5 ± 10.9 kg (median, 8.3 kg). During anesthesia, all dogs maintained mean arterial blood pressure (63.2 ± 5.4 mm Hg) within ref- erence range, and fraction of expired carbon dioxide was 40.5 ± 5.6 mm Hg. The peribulbar block was successfully performed in both eyes of all dogs. To correctly execute the injec- tion with UG, an adequate acoustic window allowing real-time visualization of the needle, globe, and mus- culature was required. The needle was appropriately positioned in the peribulbar region of the 15 eyes. In 8 of the 15 eyes, complete ultrasonographic visualization of the needle was achieved; the needle shank and tip were partially visible in images obtained from 4 eyes. The needle tip only was ultrasonographically visible for 3 eyes. Tissue distortion or the needle shank alone was not observed in the images for any of the 15 eyes. 14-02-0030r.indd 1042 11/18/2014 1:32:09 PM AJVR, Vol 75, No. 12, December 2014 1043 The ropivacaine deposition was completely visualized in real time in all 15 eyes, and both the hypoechoic and anechoic aspects were visible as circular or oval shapes (Figure 2). After peribulbar injection of ropivacaine with UG, centering of the pupil was visible (Figure 3). Of the variables assessed, only data for the IOP mea- surements were normally distributed, and are reported as mean ± SD. All other data were not normally distributed, and were compared by means of the Wilcoxon test; these data are reported as median and range as well as mean ± SD. For eyes that received a ropivacaine injection with UG, sensory block duration, the value of corneal esthe- siometry obtained in the first assessment after admin- istration of the anesthetic agent, and the mean number of punctures did not differ from findings for eyes that received a ropivacaine injection without UG (Table 1). For eyes injected with and without UG, the intervals during which the VOR, PLR, and CEM were absent and the intervals during which the VOR, PLR, and CEM were decreased did not differ significantly (Table 2). There was no difference in the intervals to restoration of the VOR and PLR; however, the interval to restoration of the CEM differed significantly between the groups of eyes. There was no difference in the overall duration of motor block between the groups of eyes. The mean basal IOP was 18.8 ± 3.5 mm Hg in the eyes that were subsequently injected without UG and 19.6 ± 4.2 mm Hg in the eyes that were subsequently injected with UG. After ropivacaine injection, mean IOP immediately after eye centralization) differed sig- nificantly (P < 0.05) between the 2 groups of eyes (23.3 ± 5.2 mm Hg in the control eyes vs 18.6 ± 5.4 mm Hg in the eyes injected with UG). The mean IOP immediately after eye centralization differed significantly (P < 0.05) from the basal value for the control eyes. The dogs’ eyes were assessed for development of hyperemia, chemosis, subconjunctival hemorrhage, ophthalmic pruritus, tearing, and discharge (all of which were classified as absent, light, moderate, or in- tense) at 30, 60, 180, and 300 minutes after injection of the anesthetic agent and at the final evaluation (Table 3). In the eyes that received a ropivacaine injection with UG, chemosis was evident in all dogs 30 minutes after administration of the anesthetic agent. However, the classification assigned to this complication decreased over time and differed significantly at 60 and 300 min- utes and at the final assessment after administration of the anesthetic agent; the severity at 60 minutes after injection of ropivacaine also differed from that at 300 minutes and at the final evaluation. Among eyes that received ropivacaine injection, that of only 1 dog did not develop chemosis at 30 minutes after administra- tion of the anesthetic agent; this finding differed with changes identified at 60, 180, and 300 minutes and at Figure 2—Representative real-time ultrasonographic image of the dispersion (area outlined by yellow dots) of 1% ropivacaine solution after peribulbar administration with UG in an isoflurane- anesthetized dog. In this image, the needle (arrow), globe (G), and optic nerve (ON) are visible. Figure 3—Photographs illustrating ocular rotation (right eye) be- fore peribulbar injection of 1% ropivacaine solution (A) and the visible centering of the pupil (left eye) after peribulbar injection of ropivacaine with UG (B) in an isoflurane-anesthetized dog. Peribulbar injection technique With UG Without UG Variable Median (range) Mean ± SD Median (range) Mean ± SD No. of punctures 1 (1–3) 1.5 ± 0.7 1 (1–6) 1.7 ± 1.3 Duration of sensory blockade (min) 383 (212–732) 416 ± 138.9 383 (157–485) 352.8 ± 97.7 Basal esthesiometric value (cm) 1.5 (2.0–2.5) 1.6 ± 0.47 1 (1–3) 1.4 ± 0.57 Postinjection esthesiometric value (cm) 0 (0–1) 0.066 ± 0.25 0 (0–0.05) 0.033 ± 0.12 Basal (pretreatment) corneal sensitivity testing of each dog was performed by use of a Cochet-Bonnet esthesiometer (pretreatment esthesiometric value [baseline]). Each dog underwent inhalation anesthesia with isoflurane and was administered a peribulbar injection of ropivacaine bilaterally (injection performed with UG for 1 eye and without UG for the other eye). A trans-eyelid ultrasonographic technique was used to decrease the risk of corneal injury, compared with the risk associated with a transcorneal technique. Number of punctures required to perform each injection was recorded. On completion of study evaluations, each dog was allowed to recover from anesthesia. Once the dog was completely awake (approx 30 minutes after gen- eral anesthetic recovery), corneal sensitivity was reassessed by esthesiometry (postinjection esthesiometric value). Duration of sensory blockade was calculated as the interval from the first assessment to the last as- sessment at which the esthesiometric value returned to baseline. Table 1—Data obtained for 15 dogs that received a peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) with UG in 1 eye and without UG in the contralateral eye (control). 14-02-0030r.indd 1043 11/18/2014 1:32:12 PM 1044 AJVR, Vol 75, No. 12, December 2014 the final evaluation, and the classification at 60 min- utes of administration differed with that assessed at 180 or 300 minutes and at the final evaluation. Severity of hyperemia also varied between the groups, but owing Peribulbar injection technique With UG Without UG Variable Median (range) Mean ± SD Median (range) Mean ± SD VOR Full blockade (min) 33 (0–70) 26.3 ± 21.8 28 (0–60) 24.9 ± 17.9 Partial blockade (min) 15 (0–60) 26.7 ± 23.5 15 (0–90) 30.3 ± 27.4 Overall blockade (min) 45 (0–168) 53.8 ± 40.2 41 (0–108) 48.8 ± 29.2 PLR Full blockade (min) 348 (98–630) 375.3 ± 124.6 313 (0–650) 323.8 ± 167.4 Partial blockade (min) 30 (0–90) 42 ± 31.7 30 (0–150) 44 ± 39.1 Overall blockade (min) 360 (158–690) 381 ± 146.1 400 (0–840) 390.5 ± 194.5 CEM Full blockade (min) 35 (0–70) 31.6 ± 20 25 (0–60) 24 ± 18.3 Partial blockade (min) 15 (0–60) 25.3 ± 21.3 15 (0–105) 26.5 ± 29.8 Overall blockade (min) 43* (0–98) 52.3 ± 27.7 50* (0–103) 55.7 ± 28.6 To assess motor blockade after peribulbar injection of ropivacaine in each eye, the intervals during which the VOR, PLR, and CEM were absent (full blockade) or decreased (partial blockade) were recorded. For the VOR, this was indicated by absence of or decrease in lateral nystagmus during cranial rotation. For the PLR, this was indicat- ed by mydriasis that was unresponsive or poorly responsive to light. For CEM, this was indicated by absence of ordecrease in visual accommodation during cranial movement. Overall duration of motor blockade was calculated as the interval from the first assessment with the dog completely awake (approx 30 minutes after general anesthetic recovery) to the last assessment when eye movement returned and was normalized. *For this variable, values differ significantly (Wilcoxon test, P < 0.02) between groups) Table 2—Duration of ocular motor blockade (determined on the basis of full or partial blockade of the VOR, PLR, and CEM) in the 15 dogs in Table 1 that received a peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) with UG in 1 eye and without UG in the contralateral eye (control). Peribulbar injection technique With UG Without UG 30 60 180 300 30 60 180 300 Complication and severity minutes minutes minutes minutes Final Total minutes minutes minutes minutes Final Total Hyperemia 12 13 Absent 4 4 3 4 4 5 5 3 4 4 Light 4 5 3 5 6 5 6 3 4 6 Moderate 7 6 8 6 5 5 4 7 7 5 Intense 0 0 1 0 0 0 0 2 0 0 Chemosis 15 14 Absent 0 0 0 4 6 2 1 1 3 6 Light 2 2 8 9 8 2 2 8 10 8 Moderate 8 7 7 2 1 7 6 6 2 1 Intense 5 6 0 0 0 4 6 0 0 0 Subconjunctival hemorrhage 3 8 Absent 13 13 14 13 13 9 8 8 8 9 Light 2 2 1 2 2 3 4 3 5 4 Moderate 0 0 0 0 0 1 0 3 2 2 Intense 0 0 0 0 0 2 3 1 0 0 Ophthalmic pruritus 1 1 Absent 15 15 14 15 15 15 15 14 15 15 Light 0 0 1 0 0 0 0 1 0 0 Moderate 0 0 0 0 0 0 0 0 0 0 Intense 0 0 0 0 0 0 0 0 0 0 Tearing 1 1 Absent 14 14 14 15 15 15 15 13 15 15 Light 1 1 1 0 0 0 0 2 0 0 Moderate 0 0 0 0 0 0 0 0 0 0 Intense 0 0 0 0 0 0 0 0 0 0 Discharge 3 3 Absent 15 14 14 15 15 14 14 14 15 15 Light 0 1 1 0 0 1 1 1 0 0 Moderate 0 0 0 0 0 0 0 0 0 0 Intense 0 0 0 0 0 0 0 0 0 0 Each dog’s eyes were assessed for ophthalmic complications; hyperemia, chemosis, subconjunctival hemorrhage, ophthalmic pruritus, tearing, and discharge were classified as absent, light, moderate, or intense. The severity of the ocular complications was recorded at 30, 60, 180, and 300 minutes after injection of the anesthetic agent and at the last moment evaluated. However, because the timing of that last evaluation differed among individuals, the final evaluation time point was not the same for all dogs. The number of complications does not add up to the total number because statistical analyses were only performed with the values obtained at 30, 60, 180, and 300 minutes after injection; these time points were chosen because they were associated with a greater number of variations. Only the incidence of subconjunctival hemorrhage differed significantly (P = 0.031) between the 2 groups of eyes, with a higher incidence in the control group. Table 3—Number of eyes with ophthalmic complications at various time points in the 15 dogs in Table 1 that received a peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) with UG in 1 eye and without UG in the contralateral eye (control). 14-02-0030r.indd 1044 11/18/2014 1:32:12 PM AJVR, Vol 75, No. 12, December 2014 1045 to the low magnitude of severity difference on the basis of the Dunn multiple comparison test, the intragroup variation over time could not be determined. Only the incidence of subconjunctival hemorrhage (Figure 4) differed significantly (P = 0.031) between the 2 groups of eyes, with a higher incidence in the control group. In 3 large dogs, (1 Labrador Retriever, 1 Golden Retriever, and 1 mixed-breed dog), the ultrasonograph- ic images were poor quality in both eyes, and eyeballs were somewhat retracted after the beginning of inha- lation anesthesia; however, these facts did not prevent the completion of the blocks and did not necessitate removal of the images from the study. The tear pro- duction was not measured after ropivacaine injection performed with UG and without UG but was visibly decreased during the measurement of the IOP, sensory evaluations, and assessment of ophthalmic complica- tions in both eyes in all dogs. Punctate superficial ulcers were found in 2 of these dogs in both eyes, in the central part of the cornea at the final assessments, though no signs of discomfort were observed. The dogs were administered topical anti- inflammatory eye dropsp and an antimicrobial ophthal- mic solutionq every 6 hours as long as was necessary; however, the corneas were healed after 3 days. Discussion Ultrasound-guided administration of local anes- thetic agents has received great notoriety in human and veterinary medicine.19 However, few studies29 have compared the clinical outcomes of these techniques with those of anesthetic blocks applied on the basis of anatomic landmarks in live animals.19,30 Thus, the pres- ent study has provided pioneering results through com- parison of data obtained following peribulbar injection of ropivacaine (1% solution) performed with and with- out UG in dogs. Successful peribulbar injection of an anesthetic agent with UG depends on upper trans-eyelid position- ing of the transducer, visualization of the needle and orbital structures, and real-time observation of the drug dispersion. The few published reports19,31,32 of ophthal- mic blocks applied with UG describe the importance of these criteria to ensure a positive clinical outcome. Although we decided to use a high fixed volume of ropivacaine to ensure that the techniques were not affected by low drug volumes (given that the local structures [extraocular muscles, fat, and blood vessels] could alter its dispersion into the intraconal36 region), benefits provided by local blocks administered with UG, such as reducing the volume and latency of the an- esthetic agent24,25,28 were not evaluated. However, other advantageous features related to the blocks adminis- tered with UG were observed including increased safety for the patient, visual confirmation of drug deposition, objective technical accuracy, and increased efficiency for difficult blocks.19,25,26,30 The lack of significant differences in sensory and motor blockade duration in the eyes anesthetized with or without UG was due to the use of ropivacaine in the same concentration (1%) and volume (0.3 mL/kg). In the dogs’ eyes evaluated in the present study, the senso- ry blockade duration was longer than the motor block- ade duration (attributed to due to the higher affinity of Aδ and C sensory fibers for ropivacaine, compared with that of motor fibers37). This finding was similar to a previously reported sensory blockade duration of 360 minutes in dogs that received local anesthesia of 1% ropivacaine solution.38 However, these data differ from that reported by Oliva et al,11 who recorded a 272-min- ute sensory blockade duration in dogs administered a less concentrated ropivacaine formulation (0.75%) via peribulbar injection. Vasquez et al40 observed a greater efficacy of 1% ropivacaine solution, compared with that of 0.75% ropivacaine solution, after periconal injection in humans. Lidocaine administration by sub-Tenonian peribulbar injection in dogs undergoing phacoemulsifi- cation provided analgesia of approximately 88 minutes’ duration in another report.6 Results of these studies confirm that ropivacaine has a long duration of action, compared with other local anesthetic agents and may reduce the pre- and postoperative opioid analgesic re- quirement and consequently, reduce the opioid-asso- ciated adverse effects (eg, sedation, urinary retention, vomiting, and body temperature changes40). Esthesiometric values between 0 and 0.5 cm indi- cate corneal insensitivity in dogs11; the values for the dogs’ eyes evaluated in the present study were within this range, thereby confirming the effectiveness of the injection techniques. The esthesiometricvalues were unlikely to have been influenced by anesthesia. The assessment was performed approximately 30 minutes after recovery from anesthesia (when the dogs were conscious) and the esthesiometric response remained absent for hours, gradually returning to basal status in nearly all dogs. These findings all confirm the establish- ment of an effective sensory blockade. The motor blockade of the PLR was the most in- tense and lasting motor effect in both eyes in all dogs in the present study, which differs from the findings of a study by Klaumanna in which a partial total mo- tor blockade of the PLR was detected in approximately 60% of 15 dogs at 55 minutes after peribulbar injection of 1% ropivacaine solution and partial motor block- ade was decreased in 40% of the dogs at 100 minutes; the difference between the values in intensity and du- ration of motor blockade in this study and in that by Klaumanna can be explained by the low volume (0.1 mL/kg) of anesthetic agent used in the latter, and also by the administration of the total volume of ropiva- caine between 2 points of puncture (lateral corner and nasomedial aspect), which exposed the parasympathet- ic nerve fibers to a lower amount of anesthetic agent. Figure 4—Photographs illustrating development of chemosis (left eye) after peribulbar injection of 1% ropivacaine solution with UG (A) and subconjunctival hemorrhage (right eye) after peribulbar injection of ropivacaine without UG (B) in an isoflurane-anesthe- tized dog. 14-02-0030r.indd 1045 11/18/2014 1:32:13 PM 1046 AJVR, Vol 75, No. 12, December 2014 The high-quality mydriasis induced by techniques in the present study eliminated the need for intraoperative administration of mydriatic eye drops, which requires comparatively more time to achieve the desired effect. Pupillary dilation induced by mydriatics eye drops of- ten dissipates during surgery41,42 and is limited when uveitis is present.43 In the present study, the duration of the motor blockade achieved by peribulbar injection of ropivacaine was short, and the blockade was predominantly partial of the VOR and CEM reflexes. Oliva et al11 detected a motor blockade of 133 minutes’ duration after peribulbar injec- tion of ropivacaine 0.75% in dogs undergoing facectomy, but the method of assessment was period intraoperative measurement of the ocular rotation by a goniometer, which differed from the evaluation method used in the present study. Klaumanna reported partial motor block- ade of the VOR in 9 of 15 dogs only at 100 minutes af- ter peribulbar injection of 1% ropivacaine solution. In the present study, the difference in CEM between eyes that were injected with or without UG was 3.4 minutes, which was not considered clinically relevant. Eye cen- tralization can also be achieved through neuromuscular blockade, but those neuromuscular agents are associated with respiratory muscle paralysis and require controlled ventilation as well as adequate patient monitoring.8,43 In humans, IOP increases in response to extra- ocular muscle pressure, intraocular content changes,45 systemic hypertension, medications, and hypercapnia. All dogs of the present study maintained mean arterial blood pressure (63.2 ± 5.4 mm Hg) within reference range, and fraction of expired carbon dioxide was 40.5 ± 5.6 mm Hg; the drugs administered are known to re- duce or maintain IOP,46,47 and a change in intraocular fluid volume was unlikely because no intraocular drug administration was evident. In humans, IOP may transiently increase immedi- ately following the peribulbar injection because of the pressure exerted on the globe by the physical volume of drug injected, which increases intraorbital pressure.48 Differences in IOP found between the groups may be due to the large volume of injected anesthetic agent and of the inadequate extrinsic muscle relaxation in some animals. Ideally, IOP should be evaluated serially during the period of blockade to determine whether any increase is transitory and related to the high drug volume or related to high latency of the block because the peribulbar technique is subject to inaccurate nee- dle positioning when performed without UG. Luyet et al33 observed the real-time dispersion of lidocaine af- ter performing a peribulbar block without UG in hu- mans and found erroneous intraconal dispersion in 61 of 100 subjects. In the dogs’ eyes that received ropi- vacaine injection with UG, IOP was unchanged after the procedure, because of the ability of ropivacaine to reduce IOP11,48,49,b; this ability may assist in balancing the IOP when large volumes of anesthetic agents are administered, increasing suspicions that the technique of peribulbar injection without UG directly influences IOP value as a result of inappropriate placement of the needle. Ophthalmic complications may be associated with peribulbar injections of local anesthetic agents and include pruritus, blepharospasm, chemosis, and subconjunctival hemorrhage6; administration of retro- bulbar blocks may cause hyperemia and corneal ulcer- ation.8 In the present study, subconjunctival hemor- rhage was less common and less intense in the dogs’ eyes that received the ropivacaine injection with UG, compared with findings for eyes that received the rop- ivacaine injection without UG, likely because of more accurate orientation of the needle path. Chemosis is caused by drug dispersion in the anterior orbit,44,50 and decreases over time as the anesthetic agent is absorbed. Accola et al18 reported that hyperemia was associated with excessive conjunctival manipulation during motor blockade assessment after performing a retrobulbar block in dogs. In the present study, senso- ry evaluation was frequently only possible by forcing the eyelids open manually, causing excessive conjunc- tival manipulation. Abnormal lacrimal production51 and eyelid akinesia5 may cause hyperemia, ocular dis- charge, and corneal ulceration in dogs; although these complications were not assessed during the postinjec- tion period in the present study, they were observed in some dogs, confirming the potential risk of ophthal- mic complications. The lower-quality definition of images obtained for 3 large dogs in the present study may be attributable to bulbar retraction caused by propofol- and isoflurane- induced muscle relaxation.52 According to Spaulding,51 ocular ultrasonography is more difficult in large dogs because of globe retraction; however, this does not con- traindicate the use of UG during administration of ocu- lar anesthetic blocks. A limitation of the present study was that the tear film in each eye was not evaluated after the injection had been administered. However, tear production was visibly decreased during the measurement of the IOP, sensory evaluations, and assessment of ophthalmic complications in both eyes in all dogs. Yasui et al53 demonstrated a relationship between lacrimal gland va- sodilation (induced by electrical corneal stimulation) and tear production in cats, which was mediated by the ophthalmic nerve via the parasympathetic pathway. The vasoconstrictive effect of ropivacaine54 may reduce lacrimal gland perfusion, which, when combined with an efficient sensory block (ophthalmic nerve block), may explain the decreased tear film in the study dogs. The anesthetic blockade of lacrimal gland innervation cannot be ruled out because of the dorsolateral location of the gland within the orbit.55 Results of the present study indicated that peri- bulbar injection of anesthetic agents can be performed effectively with UG in dogs. Use of upper trans-eyelid transducer positioning allowed real-time needle visu- alization and anesthetic agent dispersion. The quality and duration of the sensory and motor blockades werevery similar to those obtained by the conventional per- ibulbar injection technique (without UG). However, the eyes of the dogs that received peribulbar injec- tion performance with UG, the IOP remained stable and the incidence of subconjunctival hemorrhage was lower, highlighting the need for further studies to as- sess the potential clinical usefulness of this anesthetic technique. 14-02-0030r.indd 1046 11/18/2014 1:32:13 PM AJVR, Vol 75, No. 12, December 2014 1047 a. Klauman PR. Bloquio peribulbar com ropivacaina 1% em cães. MS dissertation. Universidade Federal do Paraná, Cuitiba, PR, Brazil, 2007. b. Ferreira JZ. Bloqueio peribulbar com ropivacaína a 0.75% para facectomia em cães: padronização e comparação de técnicas. MS dissertation, Faculdade de Odontologia, Universidade Estadual Paulista, Araçatuba, Brazil, 2011. c. Schirmer reflex test, Ophthalmos Indústria e Comércio de Produtos Farmacêuticos LTDA, São Paulo, Brazil. d. Cochet & Bonnet esthesiometer, Luneau Ophtalmologie, Char- tres, France. e. Fluorescein strips, Ophthalmos Indústria e Comércio de Produ- tos Farmacêuticos LTDA, São Paulo, Brazil. f. Tono-Pen XL, Medtronic, Jacksonville, Fla. g. Bio Welch Allyn, Welch Allyn, Skaneateles Falls, NY. h. Acepran 0.2%, Vetnil Ind e Comer de Produtos Veterinários LTDA, São Paulo, Brazil. i. Propovan, Cristália Produtos Químicos e Farmacêuticos, São Paulo, Brazil. j. Isoforine, Cristália Produtos Químicos e Farmacêuticos, São Paulo, Brazil. k. Monitor, Cardiocap 5, Datex-Ohmeda, GE Healthcare Indus- tries, São Paulo, Brazil. l. Accutome B-Scan Plus Advanced, Probe B: 15 MHz, resolution: 0.015 mm, gain: 47 e 55 dB, Accutome, Malvern, Pa. m. Agulha hipodérmica 22-gauge 1” BD PrecisionGlide, Becton Dickinson Ind. Cirúrg. LTDA, Curitiba, Brazil. n. Ropivacaine 1%, Cristália Produtos Químicos e Farmacêuticos, São Paulo, Brazil. o. SAS, version 9.3, SAS Institute Inc, Cary, NC. p. Cetorolaco de Trometamol 0.5%, Allergan, São Paulo, Brazil. q. Tobramicina, Alcon, São Paulo, Brazil. References 1. Carareto R, Nunes N, Sousa MG, et al. Anesthesia for oph- thalmic surgeries in canines. Rev Port Cienc Veterinarias 2007;102:35–42. 2. Vanetti LFA. Anestesia para oftalmologia. In: Ortenzi AV, Tardelli MA, eds. Anestesiologia – Sociedade de Anestesiologia do Estado de São Paulo. São Paulo, Brazil: Atheneu, 1996;591–606. 3. Myrna KE, Bentley E, Smith LJ. Effectiveness of injection of lo- cal anesthetic into the retrobulbar space for postoperative an- algesia following eye enucleation in dogs. J Am Vet Med Assoc 2010;237:174–177. 4. Kahvegian MP. Cirurgia ocular. Técnicas de Anestesia local. In: Fantoni DT, Cortopassi SRG, eds. Anestesia em cães e gatos. 2nd ed. São Paulo, Brazil: Editora Rocca, 2010;319–332. 5. Park SA, Park YW, Son WG, et al. Evaluation of the analgesic effect of intracameral lidocaine hydrochloride injection on in- traoperative and postoperative pain in healthy dogs undergoing phacoemulsification. Am J Vet Res 2010;71:216–222. 6. Ahn J, Jeong M, Lee E, et al. Effects of peribulbar anesthesia (sub-Tenon injection of a local anesthetic) on akinesia of extra- ocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification. Am J Vet Res 2013;74:1126–1132. 7. Barreiro J, Barreiro TP, Rehder JRCL. Costs of local anesthesia technique used in ophthalmology to perform cataract surgery by phacoemulsification. Arq Bras Oftalmol 2004;67:51–67. 8. Cyriac IC, Pineda RII. Postoperative complications of periocu- lar anesthesia. Int Ophthalmol Clin 2000;40:85–91. 9. Gross EM, Giuliano EA. Anesthesia for special patients: ocular patients. In: Thurmon JC, Tranquilli WJ, Benson GJ, eds. Lumb & Jones’ veterinary anaesthesia and analgesia. 4th ed. Baltimore: Williams & Wilkins, 2007;943. 10. Shilo-Benjamini Y, Pascoe PJ, Maggs DJ, et al. Retrobulbar and peribulbar regional techniques in cats: a preliminary study in cadavers. Vet Anaesth Analg 2013;40:623–631. 11. Oliva VNLS, Andrade AL, Bevilacqua L, et al. Anestesia peribul- bar com ropivacaína como alternativa ao bloqueio neuromuscu- lar para facectomia em cães. Arq Bras Med Vet Zoo 2010;62:586– 595. 12. Demirok A, Simsek S, Cinal A, et al. Peribulbar anesthesia: one versus two injections. Ophthalmic Surg Lasers 1997;28:998– 1001. 13. El Said TM, Kabeel MM. Comparison of classic peribulbar anes- thesia and new entry point (single percutaneous injection tech- nique) in vitroretinal surgery. Saudi J Anaesth 2010;4:80–85. 14. Ghali AM, Hafez A. Single-injection percutaneous peribulbar anesthesia with a short needle as an alternative to the dou- ble-injection technique for cataract extraction. Anesth Analg 2010;110:245–247. 15. Nouvellon E, Cuvillon P, Ripart J, et al. Anaesthesia for cataract surgery. Drugs Aging 2010;27:21–38. 16. Edge R, Navon S. Scleral perforation during retrobulbar and peribulbar anesthesia: risk factors and outcome in 50,000 con- secutive injections. J Cataract Refract Surg 1999;25:1237–1244. 17. Ripart J, Lefrant JY, De La Coussaye JE, et al. Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections. Anesthesiol- ogy 2001;94:156–62. 18. Accola PJ, Bentley E, Smith LJ, et al. Development of a retrobul- bar injection technique for ocular surgery and analgesia in dogs. J Am Vet Med Assoc 2006;229:220–225. 19. Morath U, Luyet C, Spadavecchia C, et al. Ultrasound-guided retrobulbar nerve block in horses: a cadaveric study. Vet Anaesth Analg 2013;40:205–211. 20. Perlas A, Chan VW, Simons M. Brachial plexus examination and localization using ultrasound and electrical stimulation: a vol- unteer study. Anesthesiology 2003;99:429–435. 21. Spence BC, Sites BD, Beach ML. Ultrasound-guided musculo- cutaneous nerve block: a description of a novel technique. Reg Anesth Pain Med 2005;30:198–201. 22. Casati A, Baciarello M, Di Cianni S, et al. Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve. Br J Anaesth 2007;98:823–827. 23. Tran TMN, Ivanusic JJ, Hebbard P, et al. Determination of spread of injectate after ultrasound-guided transversus abdominis plane block: a cadaveric study. Br J Anaesth 2009;102:123–127. 24. Costa-Farré C, Blanch XS, Cruz JI, et al. Ultrasound guidance for the performance of sciatic and saphenous nerve blocks in dogs. Vet J 2011;187:221–224. 25. Campoy L, Bezuidenhout AJ, Gleed RD, et al. Ultrasound-guid- ed approach for axillary brachial plexus, femoral nerve, and sci- atic nerve blocks in dogs. Vet Anaesth Analg 2010;37:144–153. 26. Schroeder CA, Snyder LBC, Tearney CC, et al. Ultrasound-guid- ed transversus abdominis plane block in the dog: an anatomical evaluation. Vet Anaesth Analg 2011;38:267–271. 27. Mahler SP. Ultrasound guidance to approach the femoral nerve in the iliopsoas muscle: a preliminary study in the dog. Vet An- aesth Analg 2012;39:550–554. 28. Echeverry DF, Laredo FG, Gil F, et al. Ultrasound-guided ‘two- in-one’ femoral and obturator nerve block in the dog: an ana- tomical study. Vet Anaesth Analg 2012;39:611–617. 29. da Cunha AF, Strain G, Rademacher N, et al. Palpation and ul- trasound-guided brachial plexus blockade in Hispaniolan Ama- zon parrots (Amazona ventralis). Vet Anaesth Analg 2013;40:96– 102. 30. De Vlamynck CA, Pille F, Hauspie S, et al. Evaluation of three approaches for performing ultrasonography-guided anes- thetic blockade of the femoral nerve in calves. Am J Vet Res 2013;74:750–756. 31. Luyet C, Eichenberger U, Moriggl B, et al. Real-time visualiza- tion of ultrasound-guided retrobulbar blockade: an imaging study. Br J Anaesth 2008;101:855–859. 32. Lundblad M, Eksborg S, Lonnqvist PA. Secondary spread ofcaudal block as assessed by ultrasonography. Br J Anaesth 2012;108:675–681. 33. Luyet C, Eng KT, Kertes PJ, et al. Real-time evaluation of dif- fusion of the local anesthetic solution during peribulbar block using ultrasound imaging and clinical correlates of diffusion. Reg Anesth Pain Med 2012;37:455–459. 34. Palte HD, Gayer S, Arrieta E, et al. Are ultrasound-guided oph- thalmic injurious to the eye? A comparative rabbit model study of two ultrasound devices evaluating intraorbital thermal and structural changes. Anesth Analg 2012;115:194–201. 35. Mattoon J, Nyland TG. Olho. In: Ultra-som diagnóstico em 14-02-0030r.indd 1047 11/18/2014 1:32:13 PM 1048 AJVR, Vol 75, No. 12, December 2014 pequenos animais. 2nd ed. São Paulo: Editora Roca, 2005;317– 321. 36. Nouvellon E, Cuvillon P, Ripart J. Regional anesthesia and eye surgery. Anesthesiology 2010;113:1236–1242. 37. Feldman HS, Covino BG. Comparative motor-blocking effects of bupivacaine and ropivacaine, a new amino amide local anesthetic, in the rat and dog. Anesth Analg 1988;67:1047– 1052. 38. Cortopassi SRG, Fantoni DT. Anestésicos locais. In: Andrade SF. Manual de terapêutica veterinária. 2nd ed. São Paulo, Brazil: Edi- tora Roca LTDA, 2010;375. 39. Vásquez CE, Macuco MV, Bedin A, et al. Comparação da Quali- dade do Bloqueio Oftálmico Periconal com Ropivacaína a 1% e 0,75% com Punção nos Pontos Infraorbitário Lateral e Medial da Órbita. Rev Bras Anestesiol 2002;52:681–688. 40. Plumb DC. Morphine sulfate. In: Plumb’s veterinary drug hand- book. 6th ed. Stockholm,Wis: PharmaVet, 2008;632–634. 41. Nikeghbali A, Falavarjani KG, Kheirkhah A, et al. Pupil dilation with intracameral lidocaine during phacoemulsification. J Cata- ract Refract Surg 2007;33:101–103. 42. Nikeghbali A, Falavarjani KG, Kheirkhah A. Pupil dilation with intracameral lidocaine during phacoemulsification: benefits for the patient and surgeon. Indian J Ophthalmol 2008;56:63–64. 43. Wilkie DA, Colitz CMH. Surgery of the canine lens. In: Gelatt KN, ed. Veterinary ophthalmology. 4th ed. Ames, Iowa: Blackwell Publishing, 2007;888–931. 44. Ahn JS, Jeong MB, Park YW, et al. A sub-Tenon’s capsule injec- tion of lidocaine induces extraocular muscle akinesia and my- driasis in dogs. Vet J 2013;196:103–108. 45. Mcgoldrick KE. Anesthesia and the eye. In: Barash PG, Cullen BF, Stoelting RK, eds. Clinical anesthesia. 2nd ed. Philadelphia: JB Lippincott, 1992;1095–1112. 46. Batista CM, Laus JL, Nunes N, et al. Evaluation of intraocular and partial CO 2 pressure in dogs anesthetized with propofol. Vet Ophthalmol 2000;3:17–19. 47. Stephan DD, Vestre WA, Stiles J, et al. Changes in intraocular pressure and pupil size following intramuscular administration of hydromorphone hydrochloride and acepromazine in clini- cally normal dogs. Vet Ophthalmol 2003;6:73–76. 48. Govêia CS, Magalhães E. Anestesia peribulbar com ropi- vacaína – estudo da ação vasoconstritora. Rev Bras Anestesiol 2010;60:495–512. 49. Serzedo PSM, Nociti JR, Zuccolotto EB, et al. Pressão intraocu- lar durante bloqueio peribulbar com ropivacaína ou bupivacaí- na: estudo comparativo. Rev Bras Anestesiol 2000;50:341–344. 50. Cangiani LM. Retrobulbar ou peribulbar: uma questão de no- menclatura? Vet Bras Anestesiol 2005;5:261–262. 51. Slatter D. Sistema lacrimal. In: Fundamentos de oftalmologia veter- inária. 3rd ed. São Paulo, Brazil: Editora Rocca, 2005;263–264. 52. Hodgson DS, Dunlop CI. General anesthesia for horses with spe- cific problems. Vet Clin North Am Equine Pract 1990;6:625–650. 53. Yasui T, Karita K, Izumi H, et al. Correlation between vasodila- tation and secretion in the lacrimal gland elicited by stimulation of the cornea and facial nerve root of the cat. Invest Ophthalmol Vis Sci 1997;38:2476–2482. 54. McLure HA, Rubin AP. Review of local anaesthetics agents. Mi- nerva Anestesiol 2005;71:59–74. 55. Feitl ME. Anestesia Ocular. In: Krupin, T, Kolker, AE, eds. Atlas de complicações em cirurgias oculares. São Paulo: Editora Manole LTDA, 1997;1–15.57. 14-02-0030r.indd 1048 11/18/2014 1:32:13 PM
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