Retrobulbar Nerve Block Research Articles

Ultrasound-guided Auriculopalpebral and Retrobulbar Nerve Blocks in Donkeys

Ultrasound-guided Auriculopalpebral and Retrobulbar Nerve Blocks in Donkeys

A novel enucleation- exenteration approach of the equine eye via the supraorbital fossa: an experimental and clinical study in donkeys (Equus asinus).

This study investigated the description and feasibility of a surgical procedure for enucleation-exenteration of the equine eye via the supraorbital fossa. A preliminary study was performed on both eyes of four cadaveric heads of native breed donkeys (Equus asinus) to describe the surgical anatomy and demonstrate a new supraorbital enucleation surgical approach. For the clinical study, eight donkeys were admitted for unilateral enucleation. All procedures were performed in a lateral recumbent position under the influence of inhalation anesthesia in combination with a retrobulbar nerve block. A semi-circular incision was made in the skin and fascia of the supraorbital fossa to gain access into the orbital cavity, after which the periorbital fat was dissected and removed. Bleeding was controlled by electrocautery and large blood vessels were ligated, then the eyeball was dissected sharply and freed from its bony attachment. The procedure was successfully accomplished in all clinical cases, and no significant complications occurred during or throughout the postoperative follow-up period. The initial results suggest the feasibility and safety of the supraorbital enucleation technique described in this study for equine eye enucleation. This new technique seems promising due to its feasibility, safety, and positive outcomes observed in both cadaveric and clinical studies.

A modified supraorbital surgical approach for enucleation- exenteration in dromedary camels (camelus dromedarius): Clinical study.

Enucleation and exenteration are widely utilized ophthalmic procedures in veterinary field. Enucleation in camels is like other large animals, typically performed under the influence of heavy sedation and loco-regional analgesia. The aim of the current study was to introduce a new surgical approach to enucleate the eye of camels through supraorbital fossa approach. for that purpose, the technique was applied to seven camels referred to the King-fisal teaching veterinary hospital for unilateral enucleation. Assessment of applicability, safety and feasibility of this technique was done. All procedures were performed in the kush (sitting) position under the influence of heavy sedation with Xylazine HCl in combination with retrobulbar nerve block. A "C" shaped skin incision was made in the skin and fascia of the supraorbital fossa to enter the orbital cavity, after which the periorbital fat was gripped, dissected and removed. Bleeding controlled by electrocautery and visible large blood vessels were ligated. After ligation the optic nerve and ophthalmic blood vessels, the eyeball was dissected sharply and freed from the orbital bony attachment. Finally, the orbital fascia and skin were sutured with simple interrupted pattern separately. The approach proved successful in all camels, with the enucleation procedure being both feasible and easily performed. The mean surgical time was approximately 46.6±12.4 minutes. The minimal occurrence of short and long-term complications was encouraging, and the cosmetic outcomes were notably improved. The supraorbital approach is a safe and effective technique for camel ophthalmic surgery, showing advantages in exposure and minimal complications. Further research is needed for validation and broader clinical applications.

Effect of Volumes of Solutions on Intraocular Pressure During Intravitreal Injection of Low Dose Gentamicin in Horses With Recurrent Uveitis: A Randomized Controlled Study.

Horses with recurrent uveitis can be treated by intravitreal injection of low dose gentamicin under sedation and after local anesthetic techniques including the retrobulbar nerve block. Since it is reported that retinal degeneration can be secondary to an acute increase of intraocular pressure (IOP), the current randomized controlled study was carried out in order to investigate the changes in IOP following retrobulbar anesthesia, with two different volumes of local anesthetic (lidocaine) solution (10 and 5 mL), and intravitreal injection of 6 mg gentamicin in two different volumes of solution (0.3 and 0.15 mL). Multivariate regression showed that IOP was significantly lower in the pathologic eye at baseline (estimated effect size -6.1 mmHg; P=.0001) and after sedation (estimated effect size -9.4 mmHg; P < .0001). The IOP was significantly higher after a 10 mL block (P .0002) but this effect was very small (+0.5 mmHg). There was no significant difference in IOP after the injection of 0.15 or 0.3 mL solution of gentamicin. There was no significant combined effect of the volume of local anesthetic used for the block and the volume of the gentamicin solution. Since the expected anesthetic effects (desensitization and akinesia) were met in all cases, the smaller volume of 5 mL of lidocaine solution would be preferable for retrobulbar block for intravitreal injections, while intravitreal injections volumes of 0.15 and 0.30 mL can be used indifferently.

Safety and accuracy of blind vs. ultrasound-guided dorsal retrobulbar nerve blocks in horses-A cadaveric study.

There is limited knowledge regarding the safety and accuracy of ultrasound-guided retrobulbar nerve blocks in horses. The aim of this study was to compare these parameters between blind and ultrasound-guided injection techniques for the dorsal retrobulbar nerve block in horses. Equine cadaver heads were used to inject the retrobulbar space with contrast medium (CM). Injections were performed either blindly based on anatomic landmarks (blind group, n=44) or under ultrasonographic guidance (US-group, n=44), equally divided between an experienced and unexperienced operator. Needle position and distribution of CM were assessed with computed tomography imaging and evaluated by a board-certified veterinary diagnostic imager blinded to the technique. Safety and accuracy of both techniques were compared. Ocular penetration was observed in two cases (n=2/44) in the blind group but not in the US group (n=0/44). No intrathecal, intraneural, or intravascular injections were seen in either group. Safety was significantly improved in the US group (p=.026). There was no statistically significant difference between the groups regarding the accuracy of the injection. Excellent accuracy was achieved more often with the ultrasound-guided technique (n=11/22) than with the blind technique (n=7/22) when performed by the unexperienced operator, but this difference was not statistically significant. To prevent globe-threatening complications and improve the safety of the injection, we recommend using the ultrasound-guided injection technique for the dorsal retrobulbar nerve block.

Estimation of the intraoperative blood loss in dogs undergoing enucleation.

To quantify the surgical blood loss during canine enucleation and to investigate the relationship between this and any patient, surgical, and anesthetic factors. A prospective observational analysis was conducted on 121 client-owned dogs (130 eyes) undergoing enucleation at a referral ophthalmology clinic. Blood loss was estimated by the gravimetric method (weight difference between dry and blood-containing surgical materials) to provide absolute blood loss (ABL) in milliliters, expressed as a percentage of circulating blood volume, to establish relative blood loss (RBL). Median ABL was 12 ml (1.6-116 ml), and median RBL was 1.3% (0.1%-6.7%). A higher RBL was associated with the following: use of a bupivacaine splash block versus retrobulbar nerve block (1.9 vs. 1%; p < .001), transpalpebral versus subconjunctival approach (2.2 vs. 1.3%; p=.003), and small versus large breed dogs (1.7% vs. 1.1%; p=.001). Both ABL and RBL differed significantly between surgeons. There was no significant difference in hemorrhage associated with the presence of ocular hypertension, systemic illness, surgical time, administration of meloxicam or choice of pre-medicant (acepromazine vs medetomidine). No dog required supportive intervention in response to surgical hemorrhage. This study has established a surgical blood loss estimate for dogs undergoing enucleation at an ophthalmology referral centre. Subconjunctival enucleation may be preferred for patients at greater risk of haemodynamic complications.

Preoperative oral diazepam for intraoperative blood pressure stabilisation in hypertensive patients undergoing vitrectomy under retrobulbar nerve block anaesthesia: study protocol for a randomised controlled trial

BackgroundAs a type of local anaesthesia, retrobulbar nerve block is often used in vitrectomy, with patients remaining conscious during the operation. The increase in systolic blood pressure (SBP) caused by tension and fear during the operation—especially in patients with a history of hypertension—can negatively impact the safety of the procedure, resulting in suprachoroidal haemorrhage or retinal haemorrhage. Diazepam has a sedative effect and can relieve tension during surgery. This study aims to evaluate the efficacy and safety of diazepam for intraoperative BP stabilisation in hypertensive patients under retrobulbar anaesthesia during surgery.MethodsThis single-centre, double-blind, randomised controlled and parallel clinical trial will include 180 hypertensive patients who will undergo vitrectomy with nerve block anaesthesia. Study participants will be randomly allocated in a 1:1 ratio to intervention (patients receiving oral diazepam before the operation) and control (patients receiving oral placebo before the operation) groups. The primary outcome is the effective rate of intraoperative BP control (systolic BP during operation maintained at <160mmHg at all timepoints). The secondary outcomes are the proportion of patients with SBP ≥180 mmHg at any timepoint from operation to 1 h post-operation, the change of mean systolic blood pressure and mean heart rate during operation from baseline, as well as the number of patients with intraoperative and post-operative adverse reactions within 12 weeks of surgery. The logistic regression model will be performed to compare the outcomes.DiscussionThis study will evaluate the efficacy and safety of diazepam for intraoperative BP stabilisation in hypertensive patients under nerve block anaesthesia during surgery. The results of this trial will reveal whether diazepam has a significant effect on intraoperative BP stability in patients with a history of hypertension who require vitrectomy. If the results of this trial are significant, a large-scale multi-centre clinical trial can be designed.Trial registrationChinese Clinical Trial Registry (ChiCTR) ChiCTR2100041772. Registered on 5 January 2021.

Ultrasound-guided retrobulbar nerve block in donkey cadavers

ObjectiveTo develop and describe an acoustic window to access and inject the retrobulbar region in donkey cadavers. Study designProspective cadaveric experimental study. AnimalsA total of 14 donkey cadaver heads. MethodsUltrasound landmarks for retrobulbar injection were identified by dissection of two cadavers. Ultrasound-guided retrobulbar injection of 3, 6 and 9 mL of contrast–lidocaine mixture (1:1) were evaluated using computed tomography (CT) in 12 cadavers for needle position and spread of injectate into the extraocular muscle cone. ResultsReal-time visualization of needle, extraocular muscle cone and optic nerve enabled successful intraconal instillation of injectate, as documented on CT images. Conclusions and clinical relevanceUltrasound-guided retrobulbar injections in cadaver donkeys provided adequate infiltration of the intraconal space.

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect.

Simple SummaryStanding ophthalmic surgeries have become more and more common in horses. For these standing surgeries, the blind retrobulbar block is often used for anesthesia and akinesia of the eye. However, placing a retrobulbar block using this blind technique can lead to complications, for example, penetration of the globe, nerve injury or chemosis due to spreading of the local anesthetic in the region of the globe. For this reason, it might be better to perform the retrobulbar block using guidance by ultrasound. Ultrasound-guided retrobulbar block has only been described twice in the literature using equine cadavers. Comparison of the ultrasound-guided peribulbar technique to the blind technique has only been carried out once. Furthermore, the learning curve of ultrasound-guided retrobulbar nerve block placement has not been evaluated. Our study aimed to compare the blind and ultrasound-guided approaches to retrobulbar block placement in horses and to evaluate the success and complication rates, analyzing the effect of training on ultrasound guidance. A trend towards a significant improvement in accuracy was seen for ultrasound guidance, and larger scale follow-up studies might show a significant training effect on the use of ultrasound in retrobulbar nerve block placement and that the use of ultrasound guidance could be promising.In standing ophthalmic surgery in horses, a retrobulbar nerve block (RNB) is often placed blindly for anesthesia and akinesia. The ultrasound (US)-guided RNB may have fewer complications, but the two techniques have only been compared once in equine cadavers. This study compares the techniques for success and complication rates and analyzes the effect of training on US guidance. Twenty-two equine cadavers were divided into three groups: blind RNBs were performed bilaterally in eight cadavers, US-guided RNBs were performed bilaterally in seven cadavers, and after US-guided training, blind RNBs were performed bilaterally in seven cadavers. All RNBs were performed by the same two inexperienced operators, and a combination of contrast medium (CM; 1.25 mL) and methylene blue dye (1.25 mL) were injected (2.5 mL total volume). Needle positioning in the periorbita and the distance of the CM to the optic foramen were assessed using computerized tomography (CT). Dye spreading was evaluated by dissection. In group 1, 37.5% of the injections were in the optimal central position in the periorbita; in group 2, 75% and in group 3, 71.4%. There was no significant difference between the groups regarding needle position (groups 1 and 2 p = 0.056; groups 1 and 3 p = 0.069, groups 2 and 3 p = 0.8). The mean CM distribution distance was not significantly different between all groups. Group 1 had 18.75% intraocular injections versus 0% in group 2 and 7.1% in group 3 (not significant). US guidance showed no significant increases in accuracy nor decreases in complications. However, the effects on accuracy showed a trend towards significant improvement, and larger scale follow-up studies might show significant training effects on US guidance.

Description of a novel ultrasound guided peribulbar block in horses: a cadaveric study.

BackgroundStanding surgery in horses combining intravenous sedatives, analgesics and local anaesthesia is becoming more popular. Ultrasound guided (USG) peribulbar nerve block (PB) has been described in dogs and humans for facial and ocular surgery, reducing the risk of complications versus retrobulbar nerve block (RB).ObjectiveTo describe a technique for USG PB in horse cadavers.MethodsLandmarks and PB technique were described in two equine cadaver heads (Phase 1), with computed tomography (CT) imaging confirming contrast location and spread. In Phase 2, ten equine cadaver heads were randomised to two operators naïve to the USG PB, with moderate experience with ultrasonography and conventional “blind” RB. Both techniques were demonstrated once. Subsequently, operators performed five USG PB and five RB each, unassisted. Contrast location and spread were evaluated by CT. Injection site success was defined for USG PB as extraconal contrast, and for RB intraconal contrast.ResultsSuccess was 10/10 for USG PB and 0/10 for RB (p < 0.001). Of the RB injections, eight resulted in extraconal contrast and two in the masseter muscle (p = 0.47).ConclusionsThe USG PB had a high injection site success rate compared with the RB technique; however, we cannot comment on clinical effect. The USG technique was easily learnt, and no potential complications were seen. The USG PB nerve block could have a wide application for use in horses for ocular surgeries (enucleations, eyelid, corneal, cataract surgeries, and ocular analgesia) due to reduced risk of iatrogenic damage. Further clinical studies are needed.

Prevalence of and covariates associated with the oculocardiac reflex occurring in dogs during enucleation.

To determine the prevalence of and covariates associated with the oculocardiac reflex (OCR) occurring in dogs during enucleations. 145 dogs that underwent enucleation at 2 veterinary teaching hospitals between January 2010 and June 2015. Information was collected from the medical records of included dogs regarding age and body weight at hospital admission, breed (for classification of brachycephalic status), and whether they had received anticholinergic drugs or a retrobulbar nerve block (RNB) prior to enucleation. An OCR was considered to have occurred if there was a sudden decrease of ≥ 30% in heart rate from the baseline value (mean heart rate prior to the sudden decrease) during surgery in the absence of intraoperative administration of opioids or α2-adrenoceptor agonists. Associations were explored between the collected data and the prevalence of OCR by means of binomial logistic regression. 4.8% (7/145) of dogs had an OCR noted during enucleation. Dogs that received a preoperative RNB (n = 82) had significantly lower odds of an OCR being observed than dogs that received no preoperative RNB (OR, 0.12). No association with OCR was identified for age or brachycephalic conformation or for preoperative administration of anticholinergic drugs. These findings suggested that preoperative administration of an RNB, but not preoperative administration of anticholinergic drugs, was associated with a lower prevalence of OCR in dogs during enucleations.

Factors associated with postoperative complications in healthy horses after general anesthesia for ophthalmic versus non-ophthalmic procedures: 556 cases (2012-2014).

OBJECTIVE To compare complications between healthy horses undergoing general anesthesia for ophthalmic versus non-ophthalmic procedures and identify potential risk factors for the development of complications. DESIGN Retrospective case series. ANIMALS 502 horses (556 anesthetic procedures). PROCEDURES Medical records from January 2012 through December 2014 were reviewed to identify horses undergoing general anesthesia. Signalment, body weight, drugs administered, patient positioning, procedure type (ophthalmic, orthopedic, soft tissue, or diagnostic imaging), specific procedure, procedure time, anesthesia time, recovery time, recovery quality, and postoperative complications were recorded. RESULTS Patients underwent general anesthesia for ophthalmic (n = 106), orthopedic (246), soft tissue (84), diagnostic imaging (110), or combined (10) procedures. Mean procedure, anesthesia, and recovery times were significantly longer for patients undergoing ophthalmic versus non-ophthalmic procedures. Excluding diagnostic imaging procedures, there was a significant positive correlation between surgery time and recovery time. Within ophthalmic procedures, surgery time, anesthesia time, and recovery time were significantly greater for penetrating keratoplasty versus other ophthalmic procedures. There was a significantly higher rate of postoperative colic following penetrating keratoplasty, compared with all other ophthalmic procedures. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that in healthy horses, duration of general anesthesia should be minimized to decrease the risk of postanesthetic complications. Judicious use of orally administered fluconazole is recommended for horses undergoing general anesthesia. For horses undergoing a retrobulbar nerve block during general anesthesia, use of the lowest effective volume is suggested.

Combination of dexmedetomidine with retrobulbar block in pediatric patients undergoing enucleation of eyeballs

Objective To evaluate effects of retrobulbar block combined with dexmedetomidine(Dex) on intraoperative management, postoperative pain, and recovery quality in pediatric patients undergoing enucleation of eyeballs. Methods Forty five pediatric patients(1-6 years) scheduled for enucleation of eyeballs were enrolled and randomly assigned into 3 groups(n=15), respectively received retrobulbar block combined with Dex(group ND), retrobulbar block(group N), and Dex(group D). In group ND, 0.5 μg/kg Dex was infused within 10 min after induction of anesthesia, and retrobulbar nerve block was achieved by surgeon before enucleation of eyeballs. In group N, retrobulbar nerve block was achieved before enucleation of eyeballs. In group D, 0.5 μg/kg Dex was administrated after induction of anesthesia. The MAP and HR were recorded before (T1), during (T2), and after (T3) the placement of orbital implant, and immediately after the removal of laryngeal mask airway(T4) and leave from PACU(T5). The pain scales, postoperative analgesics usage, nausea, and vomiting were assessed 2, 6 h and 24 h after operation. The perioperative adverse events were also recorded. Satisfaction regarding sleeping and pain condition was rated by parents 24 h after operation. Results The incidence of bradycardia during orbital implant placement was lower in group ND(8.3%) and group N(0) than in group D(41.7%, P<0.05). Pain scales in group ND[0(1), 0(1)] were lower than those in group N [2(2), 2(1)] and group D [3(1), 2(1)] 2 h and 6 h after operation(P<0.05), but not 24h after operation. In group ND, patients used less anal acetaminophen compared with other two groups. The severity of nausea and vomiting(no less than 2) in group ND and group N was significantly lower than that in group D. Satisfactory scores were the highest in group ND. Conclusions Retrobulbar block combined with Dex decreased oculocardiac reflex during enucleation of eyeballs in pediatric patients, and provided more satisfactory analgesic effects with fewer incidences of nausea and vomiting. Key words: Pediatric; Eye enucleation; Dexmedetomidine; Retrobulbar block

Development of an ultrasound-guided technique for retrobulbar nerve block in dromedary camels: a cadaveric study

ObjectiveDescription of an ultrasound (US)-guided technique for retrobulbar nerve blockade in dromedary (Camelus dromedarius) cadavers. Study designProspective experimental cadaveric study that was carried out in three phases: phase I: anatomical dissection and development of US-guided technique; phase II: methylene blue (MB) injection; phase III: contrast medium (CM), US-guided injections with computed tomography (CT) control. AnimalsA total of 36 orbits from 18 heads were obtained from 18 dromedary cadavers. MethodsPhase I: anatomical dissections were carried out bilaterally, using two heads to determine needle site placement. Phase II: a US-guided, lateral, in-plane approach using one of three volumes of MB (3, 6, or 9 mL) was evaluated in six heads (four orbits per volume tested) to establish the ideal injection volume. Injections of MB that strongly stained all retrobulbar nerves were considered successful, whereas insufficient MB volumes resulted in weak or no nerve staining. Phase III: US-guided retrobulbar injection with CM was carried out using 20 orbits. Computed tomography was performed after each injection trial to determine the accuracy of needle placement and CM dispersal. An injection was judged to be successful when the CT images revealed that the needle was located within the retractor bulbi muscle cone and the CM reached the target nerves at the orbitorotundum and the optic foramina. ResultsOnly injection of 9 mL of MB stained the target nerves sufficiently, whereas there was no or only weak staining with 3 and 6 mL, respectively. Therefore, 9 mL of CM was used for the US-guided injections in phase III. Subsequent CT scans revealed satisfying CM distribution within the ocular muscle cone in 18 of 20 cases (90% success rate). Conclusions and clinical relevanceUS-guided retrobulbar injection in dromedary cadavers is feasible. Further research is required to assess its practicality and usefulness in vivo.

Visual evoked potentials in the horse.

BackgroundElectrical potentials generated in the central nervous system in response to brief visual stimuli, flash visual evoked potentials (FVEPs), can be recorded non-invasively over the occipital cortex. FVEPs are used clinically in human medicine and also experimentally in a number of animal species, but the method has not yet been evaluated in the horse. The method would potentially allow the ophthalmologist and equine clinician to evaluate visual impairment caused by disorders affecting post-retinal visual pathways. The aim was to establish a method for recording of FVEPs in horses in a clinical setting and to evaluate the waveform morphology in the normal horse.MethodsTen horses were sedated with a continuous detomidine infusion. Responses were recorded from electrodes placed on the scalp. Several positions were evaluated to determine suitable electrode placement. Flash electroretinograms (FERGs) were recorded simultaneously. To evaluate potential contamination of the FVEP from retinal potentials, a retrobulbar nerve block was performed in two horses and transection of the optic nerve was performed in one horse as a terminal procedure.ResultsA series of positive (P) and negative (N) peaks in response to light stimuli was recorded in all horses. Reproducible wavelets with mean times-to-peaks of 26 (N1), 55 (P2), 141 (N2) and 216 ms (P4) were seen in all horses in all recordings. Reproducible results were obtained when the active electrode was placed in the midline rostral to the nuchal crest. Recording at lateral positions gave more variable results, possibly due to ear muscle artifacts. Averaging ≥100 responses reduced the impact of noise and artifacts. FVEPs were reproducible in the same horse during the same recording session and between sessions, but were more variable between horses. Retrobulbar nerve block caused a transient loss of the VEP whereas transection of the optic nerve caused an irreversible loss.ConclusionsWe describe the waveform of the equine FVEP and our results show that it is possible to record FVEPs in sedated horses in a clinical setting. The potentials recorded were shown to be of post-retinal origin. Further studies are needed to provide normative data and assess potential clinical use.

Analgesic and Sedative Effects of Dezocine and Midazolam During Vitrectomy

ABSTRACTPurpose: To evaluate the analgesic and sedative effectiveness of dezocine and midazolam in vitrectomy.Methods: One hundred and sixty patients undergoing vitrectomy were randomized into four groups. The control group was given local anesthetic in retrobulbar nerve block only, while the other three groups received a single dose of 0.1 mg/kg dezocine or/and 0.05 mg/kg midazolam (groups D, M, DM), respectively, at 10 min before retrobulbar block. Mean arterial pressure (MAP), heart rate (HR), and oxygen saturation (SpO2) were recorded prior to local anesthesia (Tp), at the start of surgery (T0), 5, 15, 30 min during (T1–T3), and at the end of surgery (T4). Pain at T2 and T4 was assessed by Numeric Rating Scale (NRS). Level of sedation at T2 was assessed using the Ramsay scale. Postoperative nausea and vomiting (PONV) events were recorded for 24 h.Results: Group DM showed a decrease in HR during T0–T4 compared to Tp (p < 0.001). The MAP of all groups decreased significantly at T0 compared to Tp (p < 0.05), but remained unchanged at T1–T4. At T2, all groups have lower pain level than control (p < 0.001), while group DM showed the lowest pain level. At T4, groups D and DM showed a lower pain level than control (p < 0.01). Groups M and DM showed a higher Ramsay score than group C (p < 0.01). Compared with control, group D had a higher PONV rate (p < 0.1). Groups M and DM showed a lower PONV rate than group D (p < 0.0001), and group M had a lower PONV rate than group C (p < 0.01).Conclusion: Combinatory use of dezocine and midazolam in addition to local anesthetic in retrobulbar nerve block can help relief pain and anxiety during vitrectomy and reduce PONV.

Effect of retrobulbar nerve block on heart rate variability during enucleation in horses under general anesthesia

Analysis of any effect of retrobulbar block during ocular surgery on heart rate variability and oculocardiac reflex. Prospective study. Horses (n = 16) undergoing eye enucleation due to chronic ophthalmologic diseases. Eye enucleation was performed under general anesthesia. The horses were randomly assigned to the first (inhalation anesthesia only, n = 10) or second group (inhalation and local retrobulbar anesthesia, n = 6). The retrobulbar block was performed using 12 mL of mepivacaine hydrochloride 2%. ECG data were taken by a Telemetric ECG before, during, and after surgery. Heart rate variability was analyzed in the time domain as mean heart rate, mean beat-to-beat interval duration, and standard deviation of continuous beat-to-beat intervals. The frequency domain analysis included the low- and high-frequency components of heart rate variability and the sympathovagal balance (low/high frequency). The low frequency represents mainly sympathetic influences on the heart, whereas high frequency is mediated by the parasympathetic tone. All horses without a retrobulbar block showed a significant decrease in the heart rate during traction on the globe and pressure on the orbital fat pad for homoestasis (P = 0.04). Simultaneously, high-frequency power, as an indicator of vagal stimulation, increased significantly. High-frequency and low-frequency power in the retrobulbar block group increased in five horses, and heart rate decreased in only one horse. Both were not significant within the group, but there was a significant difference between both groups relating to the incidence of heart rate decrease occurring at globe traction. Heart rate variability is a sensitive, non-invasive parameter to obtain sympathovagal stimulations during general anesthesia. The retrobulbar block can prevent heart rate decrease associated with initiation of the oculocardiac reflex.

Ultrasound-guided retrobulbar nerve block in horses: a cadaveric study

ObjectiveTo develop an ultrasound-guided technique for retrobulbar nerve block in horses, and to compare the distribution of three different volumes of injected contrast medium (CM) (4, 8 and 12 mL), with the hypothesis that successful placement of the needle within the retractor bulbi muscle cone would lead to the most effective dispersal of CM towards the nerves leaving the orbital fissure. Study designProspective experimental cadaver study. AnimalsTwenty equine cadavers. MethodsUltrasound-guided retrobulbar injections were performed in 40 cadaver orbits. Ultrasound visualization of needle placement within the retractor bulbi muscle cone and spread of injected CM towards the orbital fissure were scored. Needle position and destination of CM were then assessed using computerized tomography (CT), and comparisons performed between ultrasonographic visualization of orbital structures and success rate of injections (intraconal needle placement, CM reaching the orbital fissure). ResultsHigher scores for ultrasound visualization resulted in a higher success rate for intraconal CM injection, as documented on the CT images. Successful intraconal placement of the needle (22/34 orbits) resulted in CM always reaching the orbital fissure. CM also reached the orbital fissure in six orbits where needle placement was extraconal. With 4, 8 and 12 mL CM, the orbital fissure was reached in 16/34, 23/34 and 28/34 injections, respectively. Conclusion and clinical relevanceThe present study demonstrates the use of ultrasound for visualization of anatomical structures and needle placement during retrobulbar injections in equine orbits. However, this approach needs to be repeated in controlled clinical trials to assess practicability and effectiveness in clinical practice.

Application of target controlled infusion in eve ground surgery sedation and nursing

Objective To explore the nursing experiences of target controlled infusion applying in eye ground surgery sedation,and to form standard nursing care of peri-operation.Methods Seventy patients were randomly divided into experimental group and control group,35cases per group.Experimental group received propofol target control infusion and its plasma concentration was 1.2 microgram/ml; while control group received normal saline target control infusion instead.Results After retrobulbar nerve block 2 minutes during operation,blood pressure(MAP) of experimental group was(83.4 ± 12.1 )mm Hg,control group was(96.8 ± 15.7)mm Hg,and the difference was statistically significant ( t =5.35,P ＜ 0.05 ).Meanwhile,bispectral index (BIS) of experimental group was (83 ± 4) and control group was (95 ± 2),the difference was statistically significant ( t =6.23,P ＜ 0.05 ).Patients' satisfaction degree of post-operation follow-up was 98％ in experimental group.Conclusions Application of propofol target controlled infusing in eyeground operation with a target plasma concentration of 1.2 microgram/ml can reduce stress reaction,keep vital signs of patients stable during operation,and raise the patients' satisfaction degree. Key words: Peri-operation nursing; Eyeground operation; Target controlled infusion

Use of ketamine, xylazine, and diazepam anesthesia with retrobulbar block for phacoemulsification in dogs

The study was undertaken to evaluate the use of ketamine, xylazine, and diazepam along with a local retrobulbar nerve block for routine phacoemulsification in the dog. Animals Ten clinically healthy mixed-breed dogs of either sex, weighing between 10 and 15 kg. Ten mixed-breed dogs were selected for unilateral cataract removal by phacoemulsification. Standard preoperative preparations for cataract surgery were followed. Pre-anesthetic medication consisted of atropine sulfate (0.02 mg/kg, SC). Anesthesia was induced by xylazine HCl (1.0 mg/kg, IM) followed by ketamine (5.0 mg/kg, IM). Anesthesia was maintained subsequently with IV ketamine and diazepam to effect and depth of anesthesia was assessed clinically by pedal reflex and jaw reflex. After induction of anesthesia, a retrobulbar nerve block was performed using 2 mL of 2% lignocaine. Eye position was graded after retrobulbar block and IOP was examined preoperative, post-anesthetic, 6 h postoperative and 24 h after surgery. Phacoemulsification was performed using the phaco-chop technique and an intraocular lens was placed. Anesthetic recovery and postoperative recovery following surgery was recorded. The exposure of the globe in all the dogs was adequate; the desired central fixation of the eye was obtained and surgery could be performed uneventfully. The mean IOP recorded after induction of anesthesia was 15.75 +/- 0.82, which was not significantly (P > 0.01) different from pre-anesthetic values (14.85 +/- 0.85). Phacoemulsification was successfully performed with this anesthetic regimen without encountering major intraoperative or anesthetic complications.