Nursing the canine bilateral cataract patient: a case study

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1 Vet Times The website for the veterinary profession Nursing the canine bilateral cataract patient: a case study Author : Amy Bowcott Categories : RVNs Date : September 1, 2011 Amy Bowcott RVN, writes about nursing considerations for the preoperative and surgical stages of canine cataract surgery CATARACTS are a relatively common condition in dogs. Diabetes and/or old age can be contributing factors that may add further nursing considerations, particularly if the animal is to undergo surgery. This is a case study of a bilateral phacoemulsification and intraocular lens implantation in a dog referred to Willows Veterinary Centre and Referral Service in Solihull. Case details Patient: A nine-year-old female neutered Jack Russell terrier weighing 8.4kg. History: The patient was initially presented with a history of deteriorating vision and cloudy eyes of two months duration. A diagnosis of bilateral cataract formation had been made by the referring veterinary surgeon. The patient had been previously diagnosed with atopic dermatitis, which was controlled by cyclosporine (CsA). It was then referred to one of the Willows ophthalmic specialists for evaluation of the cataracts. Clinical examination 1 / 6

2 Clinical examination revealed no abnormalities. The owners had informed the veterinary surgeon that the dermatitis was controlled on treatment with CsA. Ophthalmic examination revealed the presence of bilateral advanced immature cataracts. There were good pupillary light and dazzle reflexes bilaterally. Menace responses were reduced due to the lens opacities. Following application of a mydriatic agent (tropicamide), fundic examination was possible, despite the lens opacities, and both retinas were normal. Intraocular pressures in both eyes were within normal limits (10-25mmHg). Investigations Local anaesthetic drops (proxymetacaine) were applied to both eyes. A generous amount of ultrasound gel was applied to the linear ultrasound probe to assist the passage of the ultrasound beam from the probe to the patient. Preoperative ultrasonography was performed (using a Logiq 7 ultrasound machine at 13 MHz) on both eyes, which was unremarkable. Diagnosis: Bilateral advanced immature cataracts. Treatment: Bilateral phacoemulsification and implantation of intraocular lenses. Preoperative preparation: Topical medication had been started one week prior to surgery to reduce the onset of postoperative lens-induced uveitis. This consisted of applying ketorolac trometamol 0.5 per cent drops four times a day to both eyes. The patient was admitted on the morning of surgery and fitted with an identification collar these are checked before any patient intervention is carried out. Safety check lists are also used throughout the practice at points of patient contact to ensure avoidable surgical errors are prevented. These points are as follows: prior to induction of general anaesthetic; prior to surgical intervention; and prior to any member of the surgical team leaving theatre. The list is adapted from the World Health Organization s check list. Preparation for surgery 2 / 6

3 The patient s rectal temperature (100.3 F), peripheral pulse (112 beats per minute) and respiration rate (14 breaths per minute) were all recorded before the premedication was administered. This consisted of 0.42mg acepromazine maleate. This was combined with 0.42mg buprenorphine. They were combined in a single syringe and administered intramuscularly. Preoperative topical medications were started one hour preoperatively, with the application of the mydriatic agent tropicamide. This was used to dilate the pupil, enabling the surgeon to look at the lens. This was applied twice within one hour. Ketorlac trometamol was also administered four times within one hour to reduce the inflammatory response to surgery. Within 20 minutes the patient was sedated. A 20-gauge intravenous (IV) cannula was aseptically placed into the right cephalic vein. The cannula was flushed with heparinised saline solution to ensure patency, and a T-port connector with an injection port was also used (flushed with heparinised saline solution to remove any air in the line). The T-port connector was connected to a giving set. General anaesthesia was induced using propofol (33.2mg), which was administered through the IV cannula. The trachea was intubated (aided with a small-bladed laryngoscope), using a size-seven reinforced endotracheal tube. The endotracheal tube cuff was inflated carefully, using 3ml of room air, to make sure there were no leaks. General anaesthesia was maintained using one to two per cent isoflurane in a carrier gas of oxygen at 2L/minute delivered using a Jackson Rees Modified Ayres T-piece breathing system (while in the preparation room). A giving set was used to administer warm Hartmann s solution. The giving set had previously been filled with the Hartmann s solution from the 500ml bag (which was labelled with patient s name, date and starting time). The giving set was connected to an Alaris infusion pump and an infusion rate was set at 5ml/kg/hour. This rate was adjusted when in theatre according to non-invasive blood pressure measurements and blood loss. Prophylactic preoperative antibiotics were administered intramuscularly (73.5mg amoxicillin clavulanate). A preoperative NSAID (33.6mg carprofen) was also administered IV. The anaesthetic was monitored closely and recorded on a chart. Bubble wrap was used around the torso, abdomen and distal paws to prevent hypothermia. This is extremely important when using the muscle relaxant atracurium besylate. White soft paraffin was applied to both eyes to prevent corneal abrasions during the eyelash trim. The upper eyelashes were trimmed carefully using curved Mayo scissors. Ultrasound gel was applied to the scissor tips to prevent any hairs from coming into contact with the cornea. Both eyes were then flushed using distilled water from a dispenser bottle. 3 / 6

4 The bladder was expressed manually (total amount of urine 20ml). The urine appeared normal. Theatre The patient was transported into theatre on a mobile anaesthetic trolley. Inhalation gaseous anaesthesia was delivered by intermittent positive pressure ventilation using a Pneupak Ventipak ventilator at a rate of 12 breaths per minute ( Figure 1 ). This was altered depending on the patient s vital parameters, including Sp0 2, end-tidal and inspired C0 2 levels. The patient was positioned in dorsal recumbency on a bean bag ( Figure 2 ). These support bags are only used for ophthalmology procedures to prevent micro-holes occurring that could cause the bag to deflate slowly, which could be detrimental to accurate positioning. Overlying the bean bag was an Inditherm heated bed. The bubble wrap around the patient was repositioned to lie like a blanket to ensure optimum insulation and prevent hypothermia. The patient s muzzle was tied to an overhead frame with a small rope tie and positioned for optimal access to the globe. A train-of-four nerve stimulator was applied to the patient s right hindlimb using crocodile clips overlying the stifle, to monitor the neuromuscular block. The surgical site was prepared with a dilution of two per cent povidone-iodine. A lacrimal cannula was used to carefully flush under the upper and lower eyelids and the conjunctival fornix ( Figure 3 ). Extreme care was taken to avoid scratching the cornea with the lacrimal cannula. The eye was then flushed with sterile sodium chloride. The area was draped in a sterile manner ( Figure 4 ). After surgery was completed on the right eye, the positioning, preparation and draping were repeated for surgery on the left eye. Surgical procedure The non-depolarising muscle relaxant, atracurium besylate (2.1mg), was administered IV. This was to ensure the eye was in a central position (anterior gaze position, so the surgeon could visualise the lens tissues, which are outlined against the retinal reflection). The eyelids were stabilised using a Barraquer speculum. The third eyelid was retracted and sutured on to the distal eyelid margin using 6/0 Polyglactin 910 and four stay sutures. A side port incision was made using a 1.2mm blade. Eighty degrees away from the first port incision a 3.2mm paralimbal corneal incision was then made at a 12 o clock position. One millilitre of hydroxyproplmethylcellulose two per cent gel was then instilled into the anterior chamber to maintain its shape, displace the iris from the incision line and protect the intraocular structures from trauma caused by the instruments and the ultrasound effects of the phacoemulsification handpiece. The gel was used ad-lib throughout the procedure to maintain the shape of the anterior chamber. A small tear was created in the lens capsule with a 25-gauge needle. Utrata forceps were used to 4 / 6

5 grasp the lens capsule and a continuous circular capsulorrhexis was made using a shearing technique. A button-tipped manipulator was introduced via the port incision and was used to stabilise and manipulate the globe. Phacoemulsification was used to break up the lens into small pieces and it was aspirated using a bimanual technique. Once all the solid lens material had been removed the remaining soft lens material was aspirated using straight and u-shaped irrigation/aspiration handpieces. The lens capsule was polished (remaining lens material removed from the capsule). Polishing was carried out using a straight irrigation/aspiration tip. Constant irrigation was maintained with Hartmann s solution, with 6.2mg heparin sodium and 500ìg epinephrine added into the bag. The bag was identified with a drugs added sticker. Sodium hyaluronate (1.5ml) at 1.4 per cent was introduced into the capsular bag, using a Rycroft cannula. The bag was filled and the gel overflowed to fill the anterior chamber. An intraocular lens (model C-Dog SE P41D; Dioptrix) was grasped with lens-holding forceps and implanted with a lens introducer cartridge and an implanter, through the capsulorrhexis and into the empty capsule. Once in the capsule, the lens was centred in the visual axis. The paralimbal corneal incision was partially closed using 9/0 Polyglactin in a simple continuous pattern. All the viscoelastic gel was removed thoroughly using irrigation and aspiration. The side port incision was closed with 9/0 Polyglactin in a simple interrupted pattern. The remaining 3.2mm paralimbal incision was closed using 9/0 Polyglactin in a simple continuous pattern. Chloramphenicol eye ointment was applied to the right eye immediately and the eye was taped closed. The left eye was positioned for surgery. A second dose of atracurium besylate 1.0mg was administered intravenously as the train-of-four nerve stimulator application produced two twitches of the right hindlimb, and the eye also began to rotate ventrally. The same procedure was repeated for the left eye. Surgery time: 75 minutes; recovery time (for the patient to assume sternal recumbency): 35 minutes. The postoperative period and general case discussion will follow in a future edition of VN Times. Reviewed by Christine Heinrich, DVOphthal, DipECVO, MRCVS and Heidi Featherstone, BVetMed, DVOphthal, DipECVO, MRCVS 5 / 6

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