OPHTHALMIC ANAESTHESIA NEWS The Journal of the British Ophthalmic Anaesthesia Society 2008 BOAS COUNCIL PRESIDENT Prof. Chandra Kumar SECRETARY Dr. K-L Kong TREASURER Mr. Tom Eke EDITOR Dr. Stephen Mather OTHER COUNCIL MEMBERS Dr. Jeremy Butcher Professor Chris Dodds Dr. Hamish Mclure Mr. David Smerdon Dr . Guri Thind Dr. Shashi Vohra Dr. Jonathon Lord Dr. Roger Slater Dr. Sean Tighe web: www.boas.org © BOAS 2008 EDITORIAL We have had problems in our hospital recently with topically applied vaso-active substances. This is not new. I have been involved in ophthalmic anaesthesia for over 20 years now and it has been a recurring problem. In fact I have had one near-death experience with a patient who developed acute pulmonary oedema after 10% phenylephrine drops. Everyone knows it is established practice to give sympathomimetics and anticholinergics to dilate the pupil, but how much consideration is given to the dose? We usually use 2.5% phenylephrine drops but occasionally I catch someone applying large quantities – sometimes a whole minim – of 10% phenylephrine in an attempt to force the dilatation of a reluctant pupil, or indeed to speed up the dilatation of a normal one. One drop is enough. Common sense tells us that excess solution, far from being absorbed into the eye, will run down the naso-lacrimal duct into the nose, there to be absorbed through the richly vascularised mucosa into the circulation, although use of a viscous solution may reduce this.. When I challenge the person they say “it’s only a drop”, but in reality it was more than one drop – it was several drops, indeed it is sometimes flooding of the eye. This excess of potent vasoconstrictor will not speed the dilatation of the pupil any more than one drop would have done, but it surely will have an effect on the blood pressure. What kind of dose is it? Well, it depends on the size of the drop, but one could expect 30 to 50 micrograms of phenylephrine per drop. 100 or more micrograms absorbed rapidly into the circulation is more than enough to bump up the blood pressure to worryingly high levels. Several studies have shown statistically significant rises in blood pressure, more so after 10% than 2.5% phenylephrine. This is maximal 10 – 20 minutes after administration1. We don’t often take the blood pressure more than once in the ward or the reception area but we may take it when the patient comes to theatre, just before we perform a block . We certainly will before a general anaesthetic. Sometimes the adverse effects are only noticed when the patient complains of headache, angina or is short of breath. We can see the time course of the effect on the blood pressure during general anaesthesia because the blood pressure is frequently recorded. Table 1 shows such a series of readings from a patient in which the blood pressure almost doubled (phenylephrine drops were applied about 1345h) Quite apart from the rise in mean arterial pressure having consequences for choroidal haemorrhage during intra-ocular surgery, I would be seriously worried about this patient’s coronary and cerebral circulation with such high systolic blood pressures. In cataract cases perhaps we could just accept the need for iris hooks? 2 Table 1 data courtesy of A. Rubin Time HR SpO NIBP NIBP mean ( mmHg) 2 12:35 58 100 127/68 91 12:40 59 100 131/67 91 12:45 50 99 101/54 74 12:50 54 99 103/54 76 12:55 50 99 101/51 73 13:00 46 99 85/44 64 13:05 45 99 80/43 60 13:10 45 99 81/41 59 13:15 56 99 98/59 79 13:20 47 99 93/48 68 13:25 47 99 84/45 62 13:30 47 99 85/43 62 13:35 49 99 94/48 69 13:40 48 99 92/47 67 13:45 65 99 119/66 89 drops applied 13:51 69 99 204/120 151 13:53 59 99 209/102 143 13:55 52 99 182/80 116 13:58 44 99 137/62 91 14:00 47 99 132/60 88 14:01 49 99 118/59 83 Sometimes we have problems in the other direction. The long term use of topical beta blockers such as timolol can lead to systemic beta blockade which we have to take account of during anaesthesia, particularly general anaesthesia. So we all have to be aware of the pharmacology, pharmacokinetics and pharmacodynamics of these agents, and how our personal interventions impact on others. In this edition of Ophthalmic Anaesthesia News, Berrin Gunaydin presents a timely review of the hazards of topically applied medication. There has been some discussion recently around the Joint Royal Colleges’ guidelines “Local Anaesthesia for Cataract Surgery”. BOAS Council have debated whether the guidelines need to be updated because the recommendations published by the Royal Colleges are now several years old. Of more concern, however, is that these guidelines are now widely applied to all forms of regional orbital anaesthesia for many different ophthalmic procedures, in many differing institutions. It is worth remembering that the guidelines were originally conceived for use within the UK National Health Service, in a comprehensive hospital setting. 3 Council member Shashi Vohra writes: “ I am particularly concerned about the following statements that put sub-Tenon's blocks in the same category as sub-conjunctival and topical blocks: ‘6.4.2 Staff and monitoring requirements for each LA technique If an anaesthetist is not present, topical, subconjunctival or sub-Tenon's block techniques are recommended. When peribulbar or retrobulbar techniques are used an anaesthetist should be available. If an anaesthetist is not available, peribulbar or retrobulbar LA techniques should not be used.’ I recently conducted a survey of the BOAS membership on the use of ophthalmic local anaesthesia and in particular sub-Tenon's blocks. The results have shown some interesting facets of practice. My survey revealed several cases of potentially life and sight threatening complications such as dysrhythmias and faints in addition to other local complications. This is probably just the tip of the iceberg as not all complications get reported. Since there is no national database it is difficult to judge the scale of the problem. The survey too was just a snapshot of practice, nevertheless quite revealing. Recently there has been one reported death following a sub-Tenon’s block2. Another problem that has surfaced from the survey is the attitude to monitoring of the cases. ‘6.4.1 Methods of monitoring All theatre personnel should have regular training in Basic Life Support (BLS), and there should be at least one person present with Advanced Life Support (ALS) or equivalent qualification.’ A number of respondents in the survey stated that in their institutions the patients were monitored by non-ALS trained staff, although the guidelines clearly advise the presence of an ALS trained person. This could be due to the misplaced belief that these blocks are so safe that they do not warrant the same input as the sharp needle orbital blocks. The current financial constraints do not help and may only worsen the situation in the future. I sincerely believe that sub-Tenon's blocks should have the same status as the routine sharp needle blocks especially as they are no longer being used just for ambulatory cataract surgery. There is clearly a need for discussion, guidance and new recommendations for monitoring as well as for precise technical aspects particularly in the light of emerging evidence”. If the situation outlined above is widespread in ophthalmic anaesthetic practice, then perhaps now is the time to conduct a national survey. Many hospitals use the 4 Medisoft electronic record system , indeed we do in my own institution, but the detail recorded for anaesthesia is minimal, and quite often wrong, being a “default” record entered by the surgeon, or a minimal record made by the anaesthetist. Transient bradycardia or unwell feelings are almost never recorded. This means we get a false picture. We seem to only record major adverse events. It also means, unfortunately, that at present we cannot use historical data on Medisoft to get an accurate representation of what is happening. If BOAS members are willing to participate in a truly national survey of complications, recording all complications, this would be a major contribution to our understanding of how safe our interventions really are. Complications are, fortunately, rare, so we will need a very large dataset. BOAS could be the vehicle through which we might enable a co-operative attempt to succeed. As a “short needle” man myself, using only 13 to 16mm needles for orbital blocks, I was particularly interested in Dr Riad’s paper on minimally invasive peribulbar block, using a percutaneous technique, published in this issue. My experience of using such short needles is that one inevitably has to use large volumes, often 9 or 10 mls. This does not, however, seem to create any problems with raised intraocular pressure or “bulging forward” of the vitreous. Such a technique does not seem to make cataract surgery more difficult. As always, we would appreciate the views of our members on different techniques. For example, do you use one or more injection points if you use short needles? Transcutaneous or transconjunctival? You don’t have to wait a year for the next edition of Ophthalmic Anaesthesia News. Let us know what you think and we’ll put it on the web site. I feel some blogging coming on…. Steve Mather References: 1. Kenawy NB and Jabir M, Br J Ophth 2003 87(4) 505 – 506. 2. Quantock CL, Goswami T, Anaesthesia 2007 62 175-177. 5 THE 2ND WORLD CONGRESS OF OPHTHALMIC ANAESTHESIA, CAIRO FEBRUARY 2008 Some people enjoy travelling as much as arriving. I am not one of those people. I put air travel in the same box as trips to the dentist and being strangled. However, I couldn’t walk, cycle or swim to Cairo, so flying was the only sensible option. My ticket informed me that my hand luggage shouldn’t include a machete, fireworks, flares, ammunition or explosives. It was going to be a pretty dull flight. Fortunately, I was able to pass the time watching the cabin crew trying to unblock the toilet, and I can report that if you ever need to salvage an impacted loo at 37,000 feet then you need to get your hands on a bottle of coca-cola. You’ll only need a couple of hundred mls, so if you’re completely bonkers you can have the rest yourself afterwards (bonkers because if it unblocks toilets, goodness knows what it could unblock in you). Anyway, after a brief 14 hour delay in Frankfurt I was on a plane again and soon arrived in Cairo. Professor Azziz’s perfect organisation was obvious from the moment we touched down. Despite the delays and unpredictable arrival time, a driver was waiting for us and whisked us through rush hour Cairo to the hotel. The Marriott is an old palace sitting on the banks of the Nile. From the outside you can hear the kamikaze traffic all around, but once you step into the lobby you know you’ve arrived in an oasis of calm - the perfect setting for the 2nd World Congress of Ophthalmic Anaesthesia. The meeting started with a brief talk by Professor Ezzat Samy Aziz, the Congress General Secretary. Using languages from each country, he welcomed delegates and faculty from all over the world. He pointed out that although the start time had drifted on to ‘Egyptian time’ the sessions would be following the published schedule, and he would be asking the Chairperson for each session to be ruthless about time keeping. For emphasis he showed us the digital stop watch that would be quietly counting down the seconds as the speaker was talking. This was going to be good. Step over the time line and the electronic counter would sound an alarm as Egyptian heavies stormed the room and carted the speaker off – brilliant. Keeping carefully to time, Professor Chris Dodds, in his role as Congress President, took to the podium to officially open the meeting. He thanked Ezzat for all his hard work and pointed out where the fire exits and toilets were. The first session entitled ‘Past, present and future’ was chaired by the one of the internationally renowned patriarchs of ophthalmic anaesthesia, Professor Chandra Kumar, and Professors Ezzat Aziz and Medhat Shalaby from Egypt. The first talk was an entertaining romp through the history of ophthalmic anaesthesia from Karl- ‘coca cola’-Koller to modern day techniques, by Steve Gayer. His talk was educational and amusing as always, and littered with superb photographs harvested from the Bascomm Palmer Institute Ophthalmic Library, which contains every text from human history which includes the words ‘eye’ and ‘dollar’ (actually the last bit of that sentence is a lie – sorry Steve). Next up was Professor Hannes Loots from South Africa. He spoke on the subject of Governance and Ophthalmic Anaesthesia, teaching us about the 5 focal virtues which will help us become better doctors, the essence, like that for becoming a prize winning taxi driver, is that we need to simply ‘care for our patients’. It seems straightforward and over-simplified, but the 4 underlying message has the ring of truth. If we care about what happens to our patients, we will deliver better care for them. The session was closed by Chris Dodds who indulged in some crystal ball gazing to give us a sneak preview of the scientific advances which are within reach and could impact on anaesthesia. These included nanotechnology, to create minute probes and new stem cell technology which promises eternal life. Having solved the problem of death, he outlined that it could also be used to grow new organs like eyes for transplantation – yes, more transplant surgeons in the ophthalmic theatres ! Quick, collect your children and run for the hills ! An additional bonus during this talk was a hugely informative image of Dr K-L Kong dressed casually as a housemaid. A salutary lesson in instructing your children not to release private family photographs to complete strangers or strange familiars! The image of K-L recognising the photo, clasping both hands over his mouth and then bringing his knees up to the sides of his ears will stay with me for a long time. The second session, entitled “Science” opened with an overview of the use of vasoconstrictors in ophthalmic anaesthesia by Dr Hamish McLure from Leeds, UK, principally with regard to their use in local anaesthetic mixtures. He was followed by an examination of the use of hyaluronidase – actually both use and abuse - by Professor Jaques Ripart from Nimes, France. Hyaluronidase is still widely used throughout the world, seemingly safely, but the optimal dose is unknown and various problems have been ascribed to it, from local reactions to pseudotumours. Next Dr Uday Goraksha from India gave a comprehensive talk on the management of intraocular pressure, always a subject guaranteed to interest anaesthesiologists and surgeons alike. The final talk of the session, by professor Berrin Gunaydin from Turkey was on the subject of topical drug administration to the eye. She outlined the potential hazards to be aware of when using drugs from many groups, but particularly topical vasoconstrictors. An expanded version of this talk appears in this edition of Ophthalmic Anaesthesia News. Session 3, entitled ‘Clinical Practice’, was chaired by Dr K-L Kong from Birmingham with Professors Adel Awara and Amr Matar from Egypt. The first talk on sedation was delivered by Dr Manuel Galindo from Columbia. He described practice in his own institution where 99% of the work was performed in an ambulatory setting – the UK Department of Health would be proud ! He detailed a vast number of sedative recipes for us to take home and try out, but cautioned that all had significant side effects if performed without care. The next speaker was Dr Oya Yalcin Cok from Ankarra in Turkey. She spoke eloquently on the problems of anaesthesia for ophthalmic examinations which may be brief, but required adequately deep levels of anaesthesia and which may unpredictably progress on to much longer more complex procedures. Dr Stephen Mather from Bristol, UK followed with a detailed and informative lecture on the causes and preventative strategies for PONV following strabismus surgery. He emphasised the multi-factorial aetiology and the requirement for a multi-stranded technique to minimise PONV. At last I’ve got a reason to tell the surgeon that these operations must not be more than 30 minutes in length otherwise they’ll get PONV ! 5 The final talk in this section was delivered by Mr Tom Eke, a surgeon from Norwich. He discussed the local anaesthetic techniques which can be used for glaucoma surgery, pointing out that the lidocaine may interfere with the remodelling and formation of the scleral flap. His personal favourite involves a combination of topical and intracameral local anaesthetic. He showed his own results which were fantastic. Looks like we anaesthetists may have to find alternative things to amuse us when the glaucoma theatre follows his lead. The evening entertainment was a Gala meal on a Nile Cruise boat. What an experience. Delicious food, a whirling dervish and a Cleopatra who turned into a belly dancer then posed next to Chris Dodds - who also posed - for photos. I have a feeling that we will all be enjoying those photos for many years to come. On Day 2 the 6th session was kicked off by Dr Marc Rozner who gave a spirited lecture on the problems of anaesthetising patients with pacemakers. If you don’t know what type it is there are a wealth of clues on the chest X-ray. He also pointed out that we need to watch out for respiratory rate monitors which can fool some pacemakers and inappropriately increase their heart rate. Also, if you have a patient with an implantable cardioverter then you must switch it off to shock therapy during the procedure. Chris Dodds was obviously feeling that he hadn’t spoken for far too long so he rose to give the next lecture on Ophthalmic Anaesthesia in the elderly. He pointed out that we need 2.2 births for every death so we can keep paying for care for the elderly. The 0.2 of a birth sounds good to me – shouldn’t need an epidural for that. Phil Guise followed Chris, speaking about the relative risks of stopping or maintaining anticoagulant therapy in the perioperative period. Current advice for most ophthalmic surgery seems to be to keep it going. Finally, Dr Daniel Espada Lahoz from Brazil gave a superbly detailed lecture on the different techniques of facial blocks. Each technique was accompanied by cartoons and video footage . The Free Paper presentations were chaired by Dr Ashish Sinha and Dr Marc Feldman. Tom Eke presented two excellent papers, one on a ‘no-scissors, no speculum’ technique for sub-Tenon’s anaesthesia (which requires a 21G triport cannula and follows on from his ‘no anaesthetist, no problem’ technique), and the other on his ‘face to face’ positioning for cataract surgery (which requires perfect balance and nerves of steel). This was followed by Dr Carniro who described a CT study looking at orbital dispersal of local anaesthetic following retrobulbar block. The CT images showed that the local anaesthetic doesn’t always move from the extraconal into the intraconal space. Dr Nagi then told us about his study comparing sevoflurane and ketamine for IOP measurements. The sevoflurane caused a 30% drop in IOP ! The final presentation of the session was by Dr Kahn who had compared single with multiple injections for sub-Tenon block. The single shot gave a better block which should save us all plenty of time ! The next session of the day in the main auditorium was chaired by an international committee consisting of Professor Mounir Afifi from Egypt, Dr Hannes Loots from South Africa and Mr Tom Eke from the UK. Dr Sinha started with a lecture about eye trauma showing some gruesome photos. Professor Aziz pointed out that in future this lecture wouldn’t be scheduled immediately after lunch. Next, Steve Gayer 6 expounded on the further use of ultrasound for ophthalmic anaesthesia. Then Dr Taylor Guillaume told us about the problems with postoperative diplopia, which they cured by changing from bupivacaine and lidocaine to mepivacaine . The final talk of this section was by Dr Roger Slater who described the anaesthetic technique for enucleation and evisceration, emphasising the importance of having a plan for postoperative pain management. Again more gruesome photos ! The final session of the meeting covered opinions in ophthalmic anaesthesia and was chaired by Professor Amr Montaser from Egypt and Dr Roger Slater and Dr Shashi Vohra from the UK. Dr Marc Feldman discussed references and patient choice in anaesthesia. He noted that for a trainee every patient presents an opportunity to perform a new and exciting procedure (every patient looks like an epidural space !). He discussed the requirement for having an anaesthetist present as inevitably some patients would have life threatening events, but that currently it was impossible to predict who they were. Dr Waleed Riad from Riyadh then described a minimally invasive blockade technique using a half inch (13mm) needle to inject 10mls of local anaesthetic in the inferotemporal space accompanied by constant digital pressure to disperse the solution. Dr George Ghaly gave the next lecture on the advantages, disadvantages and limitation of Day Care surgery which are a problem to all in the UK as the Department of Health strives to increase the proportion of procedures done as day cases. The final presentation was by Professor Stephen Gatt from Australia. He described some of the data from the Australian Adverse Event Study in which 4.6% of adverse events were related to eyes. He emphasised the need for anaesthetic presence in risky situations and went on to outline the changes in the legal system which now emphasise that although a practitioner need not have the highest expert skill they must be acting in the best interest of the patient. He detailed the identifying characteristics of “low risk anaesthetists” and gave us a list of activities which will ensure we stay contented and safe. I seem to remember him mentioning that we must get plenty of sex. Well, if it’s in the patient’s best interests …. On the plane back to the UK (only a 6 hour delay in Frankfurt, toilets fine) I reflected on what had been a superb meeting. The setting was wonderful, the atmosphere enthusiastic and supportive, and the presentations were relevant and interesting. Professor Aziz had organised one of the best meetings I’ve ever attended. The next World Congress will be in Turkey and I can’t wait. However, I will be walking to that one! Hamish McLure 7 ARTICLES HAZARDS OF TOPICAL OPHTHALMIC DRUG ADMINISTRATION: WHY DO WE CARE? Berrin Gunaydin Department of Anaesthesiology Gazi University Faculty of Medicine 06500 Ankara Turkey [email protected] Topical ophthalmic drug administration is not free from the risks of serious systemic adverse events. Such events are usually underestimated by anaesthesiologists and ophthalmologists. Many side or adverse effects occur because of systemic absorption and this is observed at an intermediate rate between intravenous (i.v.) and subcutaneous injection. One of the primary reasons for systemic toxicity is the use of high concentrations because of the low ocular bioavailability, resulting in high systemic absorption since only 1% is absorbed by the eye and the remaining 99% is considered to be systemically absorbed via the conjunctiva, through the nasolacrimal duct and nasal route. Secondly, use of non-selective drugs. However, hazards of topical ocular drugs are not necessarily a consequence of a particular group of drugs. There are other contributing factors such as comorbidity or pre-existing medical conditions (cardiovascular, pulmonary and endocrine diseases) that may interfere with these drugs. Additionally, the dose of a topically administered drug can rarely be measured and as far as the local anaesthetics are concerned, mucous membranes do not have adequate buffer capacity providing a route for diffusion of the base form of local anaesthetic 1 Most of the ophthalmic topical drugs show their effects via adrenergic (contraction of iris radial muscle via α1) or cholinergic (contraction of iris sphincter muscle via M3) receptors. There is a rich supply of adrenergic receptors in the iris, while beta receptors mostly spread in ciliary, retinal and choroidal vasculature. Muscarinic receptors (particularly M3) are present both in the iris and ciliary muscle and epithelium 2 Therefore, topical application of cholinergic, anticholinergic, adrenergic drugs and local anaesthetics are of interest. The potential hazards of topically used ophthalmic drugs are mainly related to their mechanism of action and their interaction with local or general anaesthetics . The reasons why these are important will be addressed. I. Cholinergic drugs Systemic effects of cholinergic topical ophthalmic drugs (e.g. pilocarpine) used for lowering intraocular pressure (IOP) are bradycardia, increased salivation, hypotension and bronchospasm which need reversal with i.v. atropine. Vagotonic anaesthetics like halothane can accentuate the effects of cholinergic drugs3 Most anaesthesiologists now prefer newer agents like sevoflurane or desflurane instead if a volatile agent is used for maintenance of general anaesthesia. The 8