If you wish to respond to a paper or other item already published in the BJA, please go to the abstract/full text version of that item and click on the link "E-Letters: Submit a response to the article".
Electronic Letters to:
|
|
E-letters: Electronic letters published:
-
![[Read E-letter]](/icons/misc/sectionDOWN.gif)
Anaesthesia in the prone position
- J. S. Wilmington (22 November 2008)
-
intubation in the prone position
- Anders S. Bergman (14 August 2008)
-
Re: Anaesthesia in the prone position - When the neck is excessive flexed
- Kim Carter, Hiliary Edgcombe, Simon Yarrow (16 June 2008)
-
'Nanavati position' allows avoidance of the prone position
- Mark Nel (23 April 2008)
-
Anaesthesia in the prone position - When the neck is excessive flexed
- Ming-Hui Hung, Tzong-Shiun Lee, and Shou-Zen Fan (23 April 2008)
-
Anaesthesia in the prone position
- Hilary Edgcombe, Kim Carter, S. Yarrow (13 April 2008)
-
Anaesthesia in the prone position
- Gary W Minto, Sarah Ford (26 March 2008)
|
|
|||
|
J. S. Wilmington
Send letter to journal:
|
Current literature indicates an increase of Posterior Ischemic Optic Neuropathy following lengthy prone position spine surgery in recent years. Contributory factors may include instrumentation and long surgeries >6 hours perhaps accompanied by significant facial edema. Would be interested in comments regarding staged surgeries. Also any comments regarding informed consent for this relatively uncommon yet devastating outcome. Conflict of Interest:None declared |
|||
|
|
|||
|
Anders S. Bergman, MD
Send letter to journal:
|
Dear Sir, as a commentary to the very interesting review by Edgecombe et.al. I thought it would be worth mentioning that we do approximately 100 elective prone intubations per year since many years at Ryggkirurgiska Kliniken, Strängnäs, Sweden. This is a privately run spinal surgery hospital performing approx. 700 elective operations per annum, mostly on the lumbar spine. As the very last part of the surgical evaluation of segmental pain, the patient is operatated on under local anaesthesia to determine the exact level for lumbar fusion. If a decision to perform surgery is reached, the patient is preoxygenated, induced with fentanyl-midazolam and after ascertaining that mask ventilation is adequate, relaxed with rocuronium and subsequently intubated, still in the prone position. An assistant will support the head which is turned to the patient's right and intubation is accomplished usually with a Macintosh #4 blade,a short handle on the laryngoscope, and a stylet inside the regular tube #7 or #8. In the rare case intubation should not be possible the patient will be turned onto another table and intubated supine, the surgical wound covered with sterile adhesive plastic. This technique was introduced around 1987 by Dr. Klaus Baer who for many years performed most of the prone intubations. He is now retired since some years and the technique is employed regularly by approximately 3-4 anaesthetists. To my knowledge, Dr. Baer has only published the technique once in the Swedish Medical Association´s journal "Läkartidningen" (Baer K. Läkartidningen 1992;89:3657-60.) Anders S. Bergman, M.D., Ph.D., D.E.A.A. Strängäs,Sweden anders.bergman@ryggkirurgiska.se Conflict of Interest:None declared |
|||
|
|
|||
|
Kim Carter , Hiliary Edgcombe, Simon Yarrow
Send letter to journal:
|
Editor – we would like to thank Ming-Hui Hung and colleagues for their interest in our article and for reporting their successful management of one of the complications of anaesthesia in the prone position. One of the issues which arises is the value of laryngeal mask airway (LMA) insertion as an immediately available rescue technique. Whilst controversial, it has been used successfully in this context (1,2) and is indeed increasingly being used in the elective setting, allowing patients to position themselves in the prone position to avoid other complications as we have discussed (3). Fibreoptic intubation (FOI) frequently takes longer to get organised and perform and the airway oedema which was described (and which we assume contributed to the decision not to use the LMA) can also make FOI challenging, with the risk of damage to and bleeding from the surrounding structures compromising potentially both the view and ventilation. There is indeed no simple solution to this problem. The excessive neck flexion further complicates the situation; we agree that although the tongue will generally fall forward when prone this is not always the case and the associated macroglossia contributes to the challenge. We note that the practice of avoiding oropharyngeal airways in an attempt to prevent macroglossia has been considered although one case of postoperative macroglossia (4) was believed to be secondary to pressure -related ischemic myonecrosis of the tongue muscles or intralingual branches of cranial nerves 7 and 12, where the author felt that absence of the oropharyngeal airway could have contributed to the swelling and describes his practice of using a bite block in cases where airways were omitted to try and prevent tongue protrusion and maintain the bite in a slightly open position. Both the excessive neck flexion and long duration of surgery are clearly important factors in the case you described. Altering the table position as detailed, into the reverse Trendelenburg, clearly made the best of a very difficult situation. 1. Dingeman RS, Goumnerova LC, Goobie SM. The use of a laryngeal mask airway for emergent airway management in a prone child. Anesthesia and analgesia 2005; 100: 670-1 2. Brimacombe J, Keller C. An unusual case of airway rescue in the prone position with the ProSeal laryngeal mask airway. Can J Anaesth 2005; 52: 884. 3. Edgcombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br J Anaesth 2008; 100: 165-83 4. Drummond JC. Macroglossia, Déjà vu. Anesthesia & Analgesia 1999; 89: 534. 5. Kuhnert SM, Faust RJ, Berge KH, Peipgras DG. Postoperative Macroglossia: Report of a Case with Rapid Resolution After Extubation of the Trachea. Anesthesia Analgesia 1999; 88: 220-3. Conflict of Interest:None declared |
|||
|
|
|||
|
Mark Nel
Send letter to journal:
|
Editor—The recent article on prone positioning1 emphasized the many adverse physiological effects and complications, which may be encountered. In our experience these hazards may be obviated in many operations that are routinely performed with the patient prone, by instead adopting a modified lateral position we refer to locally as the 'Nanavati position'. To achieve the Nanavati position the patient is first turned into a standard lateral decubitus position, with the limb to be operated on being dependent. The patient is then stabilized with lower back and pelvic supports in the usual way. The head is kept neutral on a pillow and the upper arm is supported in a thoracic arm rest. The key maneuver is to then place a large (eg 30cm x 30cm) sandbag under the dependent hip: this allows the pelvis to be rotated and thereby effectively brings the dependent limb into a fully prone position (see photograph). Positioning is completed by paying attention to pressure point padding and peripheral nerve protection of both lower limbs and the dependent arm. This position will facilitate good surgical access to the posterior aspect of the lower leg, and is therefore suitable for unilateral surgery on, inter alia, varicose veins involving the short saphenous system and/or sapheno-popliteal junction, Baker's cysts and ruptured Achilles tendons. Many surgeons will also accept the position we have described for pilonidal sinus and pilonidal abscess surgery. Widespread adoption of this alternative to the prone position would serve to enhance patient safety, reduce the requirement for significant numbers of trained staff to be present at positioning, and minimize the need for additional equipment such as the Montreal mattress and specialized face rests. With the Nanavati position, there is no longer a compelling case for intubation of the patient as with the prone position, and we typically manage these patients using a reinforced laryngeal mask airway. Although this position has proved safe and effective in many of our patients over a number of years, we recognize a few potential problems. Firstly, all types of lateral positioning can be expected to alter respiratory physiology. The dependent lung is efficiently perfused and ventilated on breathing spontaneously but with positive pressure ventilation the dependent lung is better perfused and the non-dependent lung better ventilated, resulting in increased V-Q mismatch. Secondly, there is always the risk of soft tissue damage or neurological compromise caused by excessive pressure on dependent areas. Finally, the act of placing a sand bag under the dependent hip can theoretically lead to exaggerated lateral tilt of the lower spine: we have seen no adverse effects from this to date but would suggest caution if normal spinal movement is compromised. S. Grover M. Nanavati M. R. Nel* Hillingdon, UK *E-mail: mark.nel@thh.nhs.uk 1. H. Edgcombe1, K. Carter1 and S. Yarrow2,* , British Journal of Anaesthesia 2008 ;100(2):165-183; Conflict of Interest:None declared |
|||
|
|
|||
|
Ming-Hui Hung Department of Anaesthesiology, National Taiwan University Hospital, Tzong-Shiun Lee, and Shou-Zen Fan
Send letter to journal:
|
Editor – We read with interest the excellent review article on Anaesthesia in the Prone Position.(1) We applaud the authors for their useful discussion and suggested solutions for practical procedures. We would like to highlight the headholder use and neck flexion in the prone position in face of emergency airway management. The headholder and flexion of the neck is commonly adopted by neurosurgeons to facilitate surgical exposure during cervical spine or posterior fossa surgery. We have recently had a patient who had accidental extubation during craniotomy in the prone position with neck hyper-flexed and rotated to her right side. The nasal tracheal tube was inserted without difficulty after induction of anaesthesia. The accident happened 6 hours after the beginning of the operation when the dura was still opened. While activating emergency airway cart, face mask ventilation was tried but difficult to achieve adequate ventilation. The chin to chest distance was short (less than 2 finger breadth) after neck flexion and the jaw was unable to be thrust. The face and tongue was too oedematous to have an oropharyngeal airway inserted. Not considering laryngeal mask airway as rescue alternative, we directly used fibreoptic bronchoscope to facilitate successfully endotracheal intubation. The swelling oropharynx and arytenoids were also seen on bronchoscopy. It is generally believed that the tongue will fall forward in the prone position and consequently the airway will tend to remain open.(1,2) Nevertheless, it is not always the case in the prone position with excessive neck flexion.(3-5) The acute angle between the oral and pharyngeal axes at the back of the tongue,(3) and tongue, face or oropharyngeal swelling as a result of obstruction of venous or lymphatic drainage4, 5 may prevent successful placement of laryngeal mask airway as a rescue alternative in case of accidental extubation.(3) Fibreoptic- assisted nasotracheal intubation is still the best solution in such kind of airway crisis. The operating table can be adjusted with reverse Trendelenburg position and elevated to its utmost level with tilt to prevent from physical restriction on the endoscopist. Potential neurological sequelae or infection can be avoided without interfering with the surgical field. Ming-Hui Hung* Shou-Zen Fan Tzong-Shiun Lee Taipei, Taiwan *E-mail: mhhung@ntu.edu.tw References 1. Edgcombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br J Anaesth 2008; 100: 165-83 2. Dingeman RS, Goumnerova LC, Goobie SM. The use of a laryngeal mask airway for emergent airway management in a prone child. Anesthesia and analgesia 2005; 100: 670-1 3. Ishimura H, Minami K, Sata T, Shigematsu A, Kadoya T. Impossible insertion of the laryngeal mask airway and oropharyngeal axes. Anesthesiology 1995; 83: 867-9 4. Augoustides JG, Groff BE, Mann DG, Johansson JS. Difficult airway management after carotid endarterectomy: utility and limitations of the Laryngeal Mask Airway. J Clin Anesth 2007; 19: 218-21 5. Tattersall MP. Massive swelling of the face and tongue. A complication of posterior cranial fossa surgery in the sitting position. Anaesthesia 1984; 39: 1015-7 Conflict of Interest:None declared |
|||
|
|
|||
|
Hilary Edgcombe Royal Berkshire Hospital, Reading, Kim Carter, S. Yarrow
Send letter to journal:
|
Editor - we would like to thank Drs Minto and Ford for their interest in our article and the interesting points which they raise. It certainly seems plausible that in the absence of muscle tone in the extra-ocular muscles, gravity may exert a force on the globe when the patient is prone, sufficient to cause traction on the optic nerve. Whether this traction is harmful (because of its effects on extra-neural blood vessels, intra-neural blood vessels or via intraneural connective tissue tearing causing haemorrhage, as has been discussed with reference to peripheral nerve injury elsewhere1), or not, is unknown. Drs Minto and Ford make the case for using remifentanil as a means of avoiding muscle relaxants and therefore presumably maintaining a degree of muscle tone which protects the optic nerve against undue traction in the prone position. This again seems reasonable, although as far as we are aware there are as yet no studies directly addressing the influence of remifentanil infusion on extra-ocular muscle tension or the incidence of post-operative visual loss. It could also be the case that general anaesthesia with or without muscle relaxants causes sufficient muscle relaxation to produce the theoretically harmful traction effect. Additionally, remifentanil infusion may influence optic nerve perfusion in other ways: in common with several analgesic and anaesthetic drugs, remifentanil at doses similar to those used by Drs Minto and Ford causes a reduction in intra-ocular pressure2 which would theoretically tend to favour optic nerve perfusion. It would be interesting to know whether this effect is maintained at all doses of remifentanil infusion, or whether at high-dose infusion, opioid-associated muscle rigidity affecting the extra-ocular muscles could in itself abnormally increase intra-ocular pressure and thus influence post-operative visual loss by this alternative mechanism. Thus there are two questions: firstly, whether traction on the optic nerve during anaesthesia in the prone position contributes to ischaemic optic neuropathy and secondly, what influence muscle relaxants (and / or remifentanil infusions) have on such traction. Both are difficult to address experimentally. At present, decisions must be made on the basis of theoretical mechanisms of injury, as well as the other features of the drugs concerned which may be of relevance to specific patients. We would agree with the practice of Drs Minto and Ford in counselling their high- risk patients regarding the potential for post-operative visual loss. We would also like to take this opportunity to thank Dr Alan Seymour, former Consultant Anaesthetist at Birmingham Heartlands Hospital, for pointing out that we omitted to mention the Parry-Brown position in our review of the historical development of the prone position. In this variation developed for thoracic surgery3, the patient lies prone with flexed hips and pillows under the chest and pelvis, allowing the abdomen to hang free. The ipsilateral arm hangs over the edge of the operating table (drawing the scapula away from the incision site) with the contralateral arm lying at the side. The head is extended on the atlanto- occipital joint and rotated to the ipsilateral side – this straightens the line of the trachea and contralateral bronchus. When the operating table is tilted, secretions will gravitate along the tracheal tube to the mouth and can be easily suctioned – this is in direct contrast to the Overholt position where secretions tended to remain in the lung until the bronchus was divided. This position had the advantages of continual drainage of the lungs, together with greater mediastinal stability, albeit at the expense of a more limited incision as compared to a lateral thoracotomy. It represented a significant advance in thoracic anaesthesia, and we are grateful to Dr Seymour for bringing this omission to our attention. H Edgcombe K Carter S Yarrow* Oxford, UK *E-mail: drsyarrow@tiscali.co.uk References: 1 Winfree CJ, Kline DG. Intraoperative positioning nerve injuries. Surg Neurol 2005; 63: 5-18 2 Sator-Katzenschlager SM, Oehmke MJ, Deusch E, Dolezal S, Heinze G, Wedrich A. Effects of remifentanil and fentanyl on intraocular pressure during the maintenance and recovery of anaesthesia in patients undergoing non-ophthalmic surgery. Eur J Anaesthesiol 2004; 21: 95-100 3 Parry Brown AI. Posture in thoracic surgery. Thorax 1948; 3: 161-5 Conflict of Interest:None declared |
|||
|
|
|||
|
Gary W Minto, consultant anaesthetist derriford, Sarah Ford
Send letter to journal:
|
In their comprehensive review of anaesthesia in the prone position, Edgcombe and colleagues (1) highlight the possibility of postoperative visual loss (POVL). Estimates of this complication for spinal surgery are as high as 0.2% (2). Analysis of 93 cases from the American Society of Anesthesiologists (ASA) Postoperative Visual Loss Registry revealed that most of the lesions were due to posterior Ischaemic Optic Neuropathy (ION) rather than direct pressure on the globe (3). We wish to postulate a possible contributory mechanism, namely the effects of prolonged muscle relaxation of the extra-ocular muscles. As explained by Kamming and Clarke in a recent case report in this journal (4) the final common pathway in ischaemia of the Optic Nerve is inadequate oxygenation of its component neurons. The perfusion of these depends on the difference between mean arterial pressure and intraocular pressure or venous pressure, whichever is the greater. It has been shown that intraocular pressure is increased when anaesthetised patients are turned prone. (5) Blood flow to the posterior optic nerve may be particularly susceptible to increased venous pressure because the supplying arteries, pial end vessels derived from the ophthalmic artery are narrow. ION may be a “compartment syndrome of the optic nerve” whereby increased venous pressure and interstitial fluid accumulation within the relatively nondistensible bony canal through which the optic nerve travels promote critical ischaemia. Elderly patients may be especially vulnerable due to the natural attrition rate of optic nerve fibres of approximately 5000 axons lost per year of life. (3) Non-depolarising neuromuscular blockers paralyse the orbicularis oculi and corrugator supercilii in a predictable fashion. (6) The effects of these agents on the rectus muscles are not well established, though it is likely that they are similarly susceptible to blockade. Our hypothesis is that muscle relaxation of the extra-ocular muscles in the prone position abolishes muscle tone and subjects the optic nerve to traction due to the unopposed gravitational pull on the eyeball. This may in turn narrow the calibre of the feeder vessels, particularly in vasculopathic individuals. The ASA has issued an advisory statement based on expert consensus (7) which suggests that patients who undergo prolonged procedures, have substantial blood loss, or both are at high risk of perioperative ION. Estimated blood loss of 1000 ml or greater occurred in 82% whilst anaesthetic duration of 6h or longer was present in 94 % of the cases from the Postoperative Visual Loss Registry. (3) It is our practice to preoperatively counsel such patients about the risk of POVL. During prolonged and potentially bloody spinal or intracranial neurosurgery in the prone position, particularly in elderly males we avoid the use of infusions or multiple doses of muscle relaxants. Remifentanil infused at 0.2 – 0.5 microgms/kg/min appears to provide suitable operating conditions whilst avoiding paralysis of the extra-ocular muscles. G. Minto S. Ford Plymouth, UK E-mail: gary.minto@phnt.swest.nhs.uk 1. Edgcombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br J Anaesth 2008; 100: 165-83 2. Stevens WR, Glazer PA, Kelley SD. et al. Ophthalmic Complications after spinal surgery. Spine 1997; 22: 1319-24 3. Lee L, Roth MD, Posner KL, et al. The American Society of Anesthesiologists Postoperative Visual Loss Registry: analysis of 93 spine surgery cases with postoperative visual loss. Anesthesiology 2006; 105: 652-9 4. Kamming D. & Clarke, S Postoperative visual loss following prone spinal surgery Br J Anaesth 2005; 95:257-60 5. Hunt K, Bajekal R, Calder I et al. Changes in intraocular pressure in anaesthetised prone patients. J Neurosurg Anesthesiol 2004; 16: 287-90 6. Hemmerling TM, Schmidt J, Hanusa C et al. Simultaneous determination of neuromuscular block at the larynx, adductor pollicis, orbicularis oculi and corrugator supercilii muscles. Br J Anaesth 2000; 85: 856-60 7. Practice Advisory for perioperative visual loss associated with spine surgery: a report by the American Society of Anesthesiologists Task Force on perioperative blindness. Anesthesiology 2006; 104: 1319-28 Conflict of Interest:None declared |
|||