Ophthalmic Anaesthesia News The Official Newsletter of the British Ophthalmic Anaesthesia Society Issue 5, October 2001 An update : Anaesthesia for Strabismus surgery Page - Contents Dr. P.A. Guise, FRCA, FANZCA 1 An update : Anaesthesia for Specialist Anaesthetist, Auckland hospital, New Zealand Strabismus surgery 6.BOAS 2001 meeting Report 8 OAS 2001 Meeting Report 13 An update : sub-Tenon’s Block Introduction 19 A Device for Inhalational Anaesthesia in Children Strabismus surgery involves altering the direction of gaze by detaching 20.Sub-Tenon’s Anaesthesia for one or more extraocular muscles from its insertion on the globe and Cataract Surgery Using a Plastic Cannula repositioning it to effectively shorten the muscle (resection) or to 22 News and Information lengthen it (recession). 27 BOAS membership application The key anaesthetic implications of this procedure are: form 1. Nausea and vomiting 31 Recent publications of interest 2. The oculo-cardiac reflex (OCR) 43 Members list 3. Adequate postoperative analgesia BOAS Registered Office 4. It is most commonly performed on the paediatric population. Department of Anaesthesia 5. Associated conditions South Cleveland Hospital 6. It is usually a Day-stay or almost an out-patient procedure. Middlesbrough TS4 3BW UK 7. The Forced Duction test (FDT) Tel 01642854601 Fax 01642854246 8. Choice of anaesthetic technique. Email: [email protected] Website: www.boas.org Nausea and Vomiting. Ophthalmic Anaesthesia News Editor: Dr Chandra Kumar The incidence of nausea and vomiting (PONV) in the first 24 hrs after Associate Editors strabismus surgery has been found to be as high as 72% in some Mr David Smerdon studies1. There are several possible reasons for this2. Firstly, during Dr Sean Tighe surgery, impulses from the extra-ocular muscles are relayed to the Dr Stephen Mather vestibular nuclei III, IV and V of the medial longitudinal fasciculi, The Society can’t be held which lie in the brainstem reticular formation. These nuclei lie in close responsible for the statements or anatomical proximity to the vomiting centre and impulses in the views of the contributors. No part of former may stimulate the vomiting centre. Support for this theory this Newsletter may be reproduced comes from the fact that there is an association between the without prior permission. oculocardiac reflex (OCR) and subsequent PONV3 such that children Articles of interest for future issue or correspondence should be sent by who had demonstrated an oculocardiac response intra-operatively were post, disk or email: 2.6 times more likely to vomit postoperatively than those who had not. Dr Chandra Kumar Secondly, alteration of the direction of gaze is thought to produce a Secretary, BOAS conflict in the CNS processing of positional information from vision South Cleveland Hospital and that from the vestibular apparatus in the inner ear leading to a Middlesbrough TS4 3BW “travel sickness” effect commonly termed the “oculokinetic reflex”. [email protected] [email protected] Ophthalmic Anaesthesia News, Issue 5, October 2001 Email: [email protected] Website http://www.boas.org 2 This effect lasts for several hours rises in a temporal relation to the offset of the postoperatively until the brain readjusts to the block. altered proprioceptive information it is receiving. Furthermore, children are also more Oculocardiac reflex (OCR) prone to nausea and vomiting4. Anaesthetic The OCR is a Trigemino-Vagal reflex 13 and is technique plays a significant part (see later): produced by traction on the extraocular the use of opiates significantly increases the muscles during surgery. (Fig 1.) Reproduced incidence 1 and the use of prophylactic anti- with permission). emetics lowers it. The afferent pathway is via the long and short The choice of which anti-emetic is most ciliary nerves to the ciliary ganglion and thence suitable is unclear. However, ondansetron 0.15 to the main sensory nucleus of the trigeminal mg/kg appears to be more effective than nerve via the Gasserian ganglion and the metoclopramide 5 droperidol appears to be as ophthalmic branch of V. Short internuncial effective as ondansetron 6,7 but is not the most fibres in the reticular formation link with the suitable anti-emetic for day stay procedures motor nucleus of the vagus, which lies slightly because of the dysphoria that affects up to 29% further down the brainstem. Efferent fibres of patients over the first 24 hrs. postoperatively then pass via X to the heart. even at doses as low as 10mcg/kg 8. Since the receptors involved in the vomiting pathway include D2, 5HT-3, H1, and ACh, theoretically administration of a combination of anti-emetics such as metoclopramide (D2), ondansetron (5HT-3) and prochlorperazine (H1 and ACh) to block all the above receptors may be more effective than a single agent. In high risk or refractory cases, dexamethasone 0.15 mg/kg 9 may enhance the effect of other anti-emetics. Oral clonidine 4mcg/kg 90min. pre-operatively 10 or lignocaine 2 mg/kg intravenously at induction of anaesthesia 2 could also be considered. Insertion of a sub-Tenon’s block prior to closure of the conjunctiva appears to significantly reduce the incidence of PONV11,12. The exact mechanism of this is unclear but may be due to the blockage of proprioceptive impulses from the operated eye The reflex has several features: preventing the “oculokinetic reflex”. Bearing in a) It is fatigueable: repeated traction mind the association of PONV and the produces progressively less effect. occurrence of the OCR, the insertion of a sub- b) It is produced to an equal extent Tenon’s block before muscle traction to block from all extaocular muscles. the OCR may be of additional benefit. This However, because of its technique also makes it unnecessary to fatigueability, the first muscle to be administer any opiates to these patients. pulled produces the biggest Modification of anaesthetic technique (see response. below) can reduce the incidence of PONV to c) It may be more common in the less than 6% in the immediate postoperative presence of a high PaCO2 (>40 period although the incidence of late PONV mmHg) Ophthalmic Anaesthesia News, Issue 5, Octoberl 2001 2 Email: [email protected] Website http://www.boas.org 3 d) It is more common if there is acute A history of any bleeding disorders should (square-wave) and aggressive also be sought as well as current medications traction on the EOM. and allergies. It is now uncommon, but e) It is not reliably prevented by occasionally phospholine iodide (ecothiopate anticholinergic premedication 14. iodide) may be used in the management of strabismus. This drug blocks There is little value in pre-treating with IV pseudocholinesterase and therefore prolongs anticholinergics at induction. If the reflex the effects of succinylcholine and ester-type becomes clinically significant despite careful local anaesthetics. surgical traction, complete cessation of traction Other medical conditions that may be and the administration of anticholinergic associated with strabismus in children are (Eg.atropine 10 mcg/kg) is all that is required. summarised in table 1. Medical Anaesthetic implications Adequate postoperative analgesia condition Traditionally, many of these children would be Down syndrome Atlanto-axial instability, given narcotic analgesics during or cardiac defects, immediately after surgery, which greatly macroglossia, increases the incidence of PONV in this group. sub-glottic stenosis, Modification of the anaesthetic technique (see tonsillar hypertrophy, below) makes the use of narcotic analgesics hypothyroidism unnecessary. Cerebral palsy Seizures, gastroesophageal reflux, joint contractures. Paediatric and Associated conditions Detailed accounts of the specific aspects of Congenital heart May require SBE anaesthetising children are out of the scope of disease prophylaxis this review, but several points are worth emphasising. These children are usually Table 1. Other medical conditions associated otherwise fit and well. However, there appears with strabismus to be an association between strabismus and neuromuscular disease such as muscular Day-stay considerations dystrophy 15 and malignant hyperthermia (MH) Unless indicated by an associated medical particularly if there is associated ptosis16,17. It condition, apart from a FBC in females 16-60 is therefore important to ascertain if there is yrs., no preoperative laboratory tests are any family history of anaesthetic problems. required. However, it is important to note that a history The optimal duration of preoperative fasting is of a previous uneventful anaesthetic does not not unanimously agreed. However, in this exclude susceptibility to MH even if known institution there is restriction of solids for 6hrs. trigger agents had been administered. and clear fluids for 2hrs. in children and adults, and 4hrs for breast and bottle-fed infants. Because nausea and vomiting are a significant Patients having strabismus surgery are usually concern with strabismus surgery, a history of ready for discharge within 2 - 4hrs. PONV or motion sickness should be noted. postoperatively, and therefore sedative Strabismus surgery is an elective procedure premedication is usually omitted. However, and this must be taken into account if the child paediatric patients routinely receive 30mg/kg presents with an upper respiratory tract oral paracetamol on arrival (about 60 min. infection (URTI). The presence of an URTI preoperatively). A 250mg/5ml strength syrup is increases the risk of a perioperative respiratory used to decrease the volume of fluid given. complication four- to sevenfold19. The Anticholinergic premedication is not routinely complication risk is particularly high in employed since it is unreliable at preventing children under 1yr. And these should definitely the oculo-cardiac reflex [14], and drying of be deferred. In older children the risk/benefit secretions is not required. ratio needs to be considered on an individual basis. Ophthalmic Anaesthesia News, Issue 5, October 2001 3 Email: [email protected] Website http://www.boas.org 4 Forced Duction Test (FDT) from a surgical and anaesthetic management This is a manoeuvre performed by the surgeon aspects. Traditionally these children would after induction of anaesthesia to check for free spend at least most of the day if not a night in passive movement of the eye in order to hospital after surgery. Strabismus surgery has differentiate between a paretic muscle and a been associated with one of the highest physical restriction impeding ocular incidences of PONV of any surgical procedure. movement. Some authors19 recommend non- Also, these patients were routinely intubated, depolarising neuromuscular block as well as with all the associated problems that that may avoiding succinylcholine so that muscle tone is cause in day-stay patients. absent permitting a more “accurate” FDT. The paediatric ophthalmologists in this institution Understanding the mechanisms behind many of are of the firm opinion that although avoiding the postoperative problems has led to succinylcholine is desirable, it is unnecessary significant improvements in the way these to produce neuromuscular block in order to children are managed for their anaesthetic with accurately perform the FDT. a corresponding reduction in postoperative morbidity. This has contributed to a reduction Choice of Anaesthetic Technique in time spent in hospital such that most At Auckland hospital, the following technique children are now ready for discharge within 2 is used: oral preoperative Paracetamol hours after surgery 30mg/kg, spontaneous respiration on a References laryngeal mask with Oxygen/Nitrous 1. Mendel HG et al. ketorolac vs fentanyl on oxide/Sevoflurane, avoiding narcotics and postoperative vomiting and analgesic performing a sub-Tenon’s block using a requirements. Anes. Analg. 1995:80:1129- lignocaine/bupivacaine mix at the end of 33. surgery. A randomised, prospective double- 2. Warner LO, Rogeres MD et al. Intravenous blind trial11 of 70 children employing this lignocaine reduces the incidence of technique with and without ondansetron 0.1 vomiting in children after strabismus mg/kg, was associated with minimal surgery. Anesthesiology 1988:68:618-21. postoperative discomfort and a PONV 3. Allen L, Sudesh S, et al. Th association incidence of less than 6% in the first two hours between the oculocardiac reflex and post- postoperatively. PONV in the subsequent 24 operative vomiting in children undergoing hrs. (when the sub-Tenon’s block would have strabismus surgery. Eye 1998:12:193-6. worn off) was higher, but still less than 20%. 4. Kenny GN. Risk factors in postoperative Interestingly, the incidence of PONV was not nausea and vomiting. Anaesthesia 1994 reduced by addition of ondansetron. No (Jan):49 Suppl.6-10. patients required admission overnight and no 5. Rose JB, Martin JM, Corddry DH et al. narcotic analgesia was required Ondansetron reduces the incidence and postoperatively. severity of poststrabismus repair vomiting A previous study by Fry and Walker12 on 45 in children. Anes.Analg. 1994:79(3):486-9. patients using a similar technique but with 6. Tang J, Watcha M, White P. A comparison routine use of ondansetron and of costs and efficacy of ondansetron and prochlorperazine was associated with a zero droperidol as prophylactic antiemetics. incidence of PONV in the first 24hrs. Anesth.Analg. 1996:83:304-313. postoperatively. 7. Klockgether-Radtke A, et al. Ondansetron, The inclusion of a non-steroidal anti- droperidol and their combination for the inflammatory agent such as Voltaren 1.5 mg/kg prevention of post-operative vomiting in could also be considered, although it is children. Eur.J.Anaesthesiol. 1997:14:362-7. uncertain as to whether this improves overall pain scores. 8. Lim BS, Pavy TJ, Lumsden G. The antiemetic and dysphoric effects of Summary droperidol in the day surgery patient. The management of children having strabismus Anaesth.Int.Care 1999:27:4:371-4. surgery has changed over recent years both Ophthalmic Anaesthesia News, Issue 5, October 2001 4 Email: [email protected] Website http://www.boas.org 5 9. Splinter W, Rhine E. Low-dose ondansetron undergoing squint surgery. with dexamethasone more effectively Br.J.Anaes.1982:54:1059-63. decreases vomiting after strabismus surgery 15 Lewandowsi KB. Strabismus as a possible in children than does high-dose sign of muscular dystrophy and malignant ondansetron. Anesthesiology 1998:88:72-5. hyperthermia. Can.An.Soc.J. 1982:29:372- 10 Mikawa K, Nishina K, et al. Oral clonidine 6. premedication reduces vomiting in children 16 King JO, Denborough MA. Anaesthetic after strabismus surgery. Can. J. An. 1995 induced malignant hyperthermia in children. Nov 42 (11): 977-81. J.Peadiatr. 1973:81:37-40. 11 Fry R, Guise P. A comparison of 17 Smith R.J. Preoperative assessment of risk Ondansetron vs. placebo on postoperative factors for malignant hyperthermia. nausea and vomiting following squint Br.J.Anaes. 1988:60:317-9. surgery in children. (Work in progress). 18 Cohen MM Cameron CB. Should you 12 Fry R, Walker M. Can vomiting after cancel the operation when a child has an squint surgery be prevented? (Letter) upper respiratory tract infection? Anaesth.Int.Care 1997:25:94-5. Anesth.Analg. 1991:72 (3):282-8. 13 Blanc V. et al. The oculo-cardiac reflex: an 19 Dell R, Williams B. Anaesthesia for analysis in infants and children. Can.J.An. strabismus surgery: a regional survey. 1983:30:360-9. Br.J.Anaes. 1999:82:5:761-3. 14 Mirakhur RK, Jones CJ, et al. IM or IV atropine or glycopyrrolate for the prevention of the oculo-cardiac reflex in children Ophthalmic Anaesthesia News, Issue 5, October 2001 5 Email: [email protected] Website http://www.boas.org 6 BOAS Meeting Report Middlesbrough 30TH-31ST AUGUST, 2001 After the unfortunate cancellation of the 3rd previous sharp needle techniques. They Annual meeting of the Society in London, the concluded that Sub-Tenons should be the fate of BOAS 2001 was uncertain. However method of choice for eye surgery. due to the hard work and enthusiasm of Dr Sean Tighe ended the first session with a Chandra Kumar, we need not have worried. comparison of Sub-Tenons and Topical Local BOAS 2001 WOULD happen and WOULD be Anaesthesia in respect of their complications a success. and efficacy, concluding that Sub-Tenons was Tall Trees Conference Centre again proved probably superior. He also tackled the cost itself to be an excellent venue for the meeting issue of including an Anaesthetist, and with its unique blend of high quality concluded that since they contributed greatly to accommodation and sports facilities in a rather efficiency and provided the necessary ALS “Out of Town” environment. back up, that their expense was justified! Despite the organisers’ short time scale, the After Coffee the Free paper session contained meeting attracted speakers from as far as Egypt six excellent presentations where again the and New Zealand, as well as 92 delegates from most frequent subject was that of Sub-Tenons. all corners of the UK and Portugal. Mr H Ruschen presented four case reports of The meeting commenced on the afternoon of complications following Sub-Tenons; two Thursday 30th with a series of workshops on patients developed hyphaemas, one a central such topics as Peribulbar/Retrobulbar blocks, retinal artery occlusion and the fourth vitreous Sub-Tenons block, Orbital Anatomy and Fast haemorrhages from a presumed globe Track Cataract Surgery. Due to popular perforation. This served as a warning to all that demand each workshop was run twice, giving Sub-Tenons may not be as free from both presenters and delegates a very busy complications as we imagine. afternoon. Chandra Kumar presented the results of a study Professor Chris Dodds, the President of BOAS in Middlesbrough using a short (6 mm) metal welcomed delegates to the meeting at the start cannula. This proved to be equally as effective of proceedings on Friday morning, which was as standard Cannulae and may reduce the risk well attended despite the excellent dinner and of complications. wine the previous evening. The next paper, also from Middlesbrough The first Scientific Session began with Monica described the results of an audit comparing 3 Hardwick presenting a summary of the recently commonly used Sub-Tenons Cannulae. All published, Joint Colleges Guidelines on Local three Cannulae gave good results but the deep Anaesthesia for Intraocular Surgery. This plastic cannula was more effective than the provoked a few comments from delegates on anterior one, and was equal or better than the the more controversial issues, but generally it metal cannula. appears that these guidelines have been well The third paper from Middlesbrough given by received, unlike their predecessors! Mr N Prasad described the fascinating The remainder of the first session was devoted subjective visual experiences described by mainly to the technique of Sub-Tenons block, patients undergoing phacoemulsification which seems to be rapidly gaining in cataract surgery under Sub-Tenons anaesthesia. popularity. Chandra Kumar gave a fact-filled On a different subject, Dr Andy Mitchell presentation on the history of the technique presented a study, which he carried out in along with illustrations of the various Cannulae Worcester, looking at postoperative morbidity used, possible drug mixtures and after cataract surgery under three different local complications. block techniques. Although there was no Phil Guise presented the results of a large serious morbidity reported after any of the prospective study carried out in his unit in techniques, it was surprising to note the high Auckland, which compared efficacy and incidence of minor morbidity such as a “blood- complications of Sub-Tenons with their Ophthalmic Anaesthesia News, Issue 5, October 2001 6 Email: [email protected] Website http://www.boas.org 7 shot“ eye, double vision, periorbital numbness surgical techniques used, and how they affect and post op pain. the anaesthetist – this was “all you ever wanted The second paper on a subject other than Sub- to know about vitreoretinal surgery but were Tenons, was given by Prof S Aziz from Cairo, afraid to ask (…a surgeon)!” and looked at the use of deep topical fornix The third presentation was by Ken Barber from nerve block as an aid to the one step adjustable Worcester who gave a colourfully illustrated suture technique for horizontal strabismus practical guide to dealing with problem surgery. They concluded that this was an patients presenting for cataract surgery under effective method of performing this technique local anaesthesia. These included the very without the need for general anaesthesia. anxious, those with a marked tremor, COPD, The last scientific session of the morning or an inability to lie flat. Various methods were included two National Survey reports. suggested to alleviate what are very common The first was an excellent presentation by Ed problems for surgeons and anaesthetists. Morris from Bristol on the National Survey of A Case discussion was the next item on the Fasting in Ophthalmic Regional Anaesthesia, programme, and this was presented by Robert which was published recently in Anaesthesia. Boyce from Middlesbrough, who described The second Survey report was that of current two patients that developed acute orbital cataract practise in the UK by UKISCRS inflammation after cataract surgery. The local members, presented by David Smerdon from anaesthetic techniques were different, but Middlesborough. The questionnaires of which hyalase was used in both cases. The discussion 79% were returned, asked numerous questions revolved around the causes of orbital on surgical technique, biometry formulae and inflammation and whether these were cases of recording outcomes. There were also questions pseudotumour induced by hyalase. Delegates on Anaesthesia, including techniques, who were asked to report any similar cases in their gave the anaesthetic and methods of practice to BOAS. monitoring. The final presentation of the day was the guest At the Annual General Meeting of the Society lecture sponsored by Abbot Laboratories and Prof Chris Dodds officially took over as the speaker was Dr Graem McLeod from President of BOAS and thanked his Dundee. Dr McLeod’s presentation was predecessor Rob Johnson for getting the entitled Levobupivacaine- improved safety for society off to such a good start. Two new Regional Anaesthesia? In which he eloquently council members were approved – Dr Steve reviewed the preclinical, human toxicity, Mather and Dr Gurvinder Thind, and details potency and clinical data for Levobupivacaine. were announced of forthcoming meetings, He provided evidence from large studies that particularly that in Birmingham in June 2002. Levobupivacaine is consistently less toxic than After lunch the first scientific session of the Bupivacaine, and has been used effectively in afternoon included three papers on more central and peripheral blocks including practical issues of patient management for ophthalmic blocks. various types of ophthalmic surgery. The meeting closed with a vote of thanks from The first was by Jonathan Lord from Prof Chris Dodds to the organisers of an Moorfields on General Anaesthesia for excellent meeting, namely Chandra Kumar and Paediatric Glaucoma. Although Paediatric his team from Middlesbrough, including the Glaucoma is very much a specialist area many stalwart conference secretary Pat McSorley. of the principles outlined in Dr Lord’s All those present; Council members, faculty presentation would be equally applicable to and delegates had enjoyed an entertaining and children undergoing other types of ophthalmic informative meeting which would ensure the surgery. continuing success of the British Ophthalmic Dr Rob Johnson gave an illuminating Anaesthesia Society. presentation on General and Local Anaesthesia for Vitreoretinal Surgery. He also included Dr Monica Hardwick, Worcester, UK some fascinating and useful background to the Ophthalmic Anaesthesia News, Issue 5, October 2001 7 Email: [email protected] Website http://www.boas.org 8 OAS Meeting, Chicago 2001 challenges from both surgical and an anaesthetic view. The annual scientific meeting of the American We were treated to two excellent workshops. Ophthalmic Anesthesia Society took place in Dr Gary Fanning presented a master class on Chicago from the 5th to the 7th of October. It orbital anatomy and the virtues of using a was a very successful meeting and well SHORT needle in the correct place. Dr Scott attended by North American members as well Greenbaum ran a master class on sub-tenon's as by 5 members of BOAS despite everyone's anaesthesia with a very balanced view of the concern with air travel after September the alternative techniques and their respective 11th. merits - or otherwise. The quality of the scientific programme was of a uniformly high standard and it covered areas of interest to all delegates. Indeed there appeared to have been a move to reduce the UK questions (usually - why not give a GA?) by providing expert discussion of points raised in the lectures. I will hint at the flavour of the meeting by mentioning just a few of the presentations, not because of lack of merit in those missed out, but because a comprehensive listing can be found on the OAS website ([email protected]). Three wise monkeys (from left to right Prof There were anaesthetically orientated topics Chris Dodds, Gary Fanning and Chandra such as a fascinating review of the history of Kumar) ophthalmic anaesthesia by Warren Hill, another on the impact of coagulopathy on ophthalmic anaesthesia from Marc Feldman, and the cluster of diplopia following regional orbital anaesthesia without bovine hyaluronidase from Sandra Brown. There was an update on the American Resuscitation guidelines from Len Romanowski that reinforced some of the differences in practice across the Atlantic. How many of us are aware of the changes recommended in February this year by the European Resuscitation Council, or have actually been re-certified as an ACLS provider? The ophthalmic surgical perspective was clear Ladies had wonderful time too (from left to and incisive - just as we would expect! The right Mrs Arline Fanning, Dr Ann Dodds, lecture by Steve Charles on the anaesthetic and Mrs Suchi Kumar and Mrs Ursula Johnson) surgical interface for V-R surgery was grounded in both clear expertise and great Socially, (I have no doubt the BOAS website common sense. Those who care for these will testify to this!) we had a great time but it patients all learnt from the lecture and those played havoc with our diets. It was so good who didn't were even more determined not to that several airlines reduced the number of get involved. Steven Gayer gave a masterly passengers to maintain a safe weight of cargo review of intraocular melanoma and the for the return trip. Even staunch trenchermen Ophthalmic Anaesthesia News, Issue 5, October 2001 8 Email: [email protected] Website http://www.boas.org 9 like Chandra Kumar failed to complete at the Eire Café, although Bob Johnson and another did manage to order and eat pudding. Dr Gary Fanning entertaining BOAS representatives and their wives (from left Ursula Johnson, Bob Johnson, Arline Fanning, Gary Fanning, Chandra Kumar and Chris Dodds) All in all it was a great meeting and one that we would encourage more members of BOAS to include in their CEPD list of places to go. Certainly they were very interested in the next BOAS meeting in Birmingham next June. Chris Dodds, President, BOAS Ophthalmic Anaesthesia News, Issue 5, October 2001 9 Email: [email protected] Website http://www.boas.org 10 BOAS is grateful to Abbott Laboratories for sponsoring the printing of this Newsletter We hope to receive future support Ophthalmic Anaesthesia News, Issue 5, October 2001 10 Email: [email protected] Website http://www.boas.org
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