Failed epidural in an obese patient - blame it on Pythagoras!

Anaesthesia, 2000, 56, pages 585-610 block in labour with inspection of the catheters to loop in the soft tissues of individual practice varies slightly, there puncture site revealing fluid leakage. the back, thus explaining the phenomis enon of continuous epidurals becomsuccess rate and minimises insertion With regard to Carrie and Russell's suggests that this is insufficient in some in visualising their epidural catheters radiologically, we had no such propresented generation of neuro-radiological conblems, term requesting epidural analgesia. She skin level. Collier and Gatts difficulties may be the catheters being perfectly obese patients. A 26-ycar-old in primigravid spontaneous patient labour at trast it is extremely difficult reliably to clear to junior anaesthetists and midwas 115 kg but otherwise fit and well visualise epidural catheters in the back, wives with and we wonder if their representations extraordinary suggestion that we had spinous processes were palpable and an of gently looping catheters are artefacimagined the catheter images and that epidural was sited on the first attempt at tual. It seems unlikely that a catheter our ‘representations of gently looping inserted through a straight needle could catheters are artefactual’ would negate L3,4- It was 7.5 cm from the skin to the epidural space. The epidural was fixed adopt such a loop in the rigid confines of the back ligaments and musculature, the whole point of our report and even away from the midline, as a brief our professional integrity. inspection during a lumbar laminecwhite lines’ which we drew on the Xskin at 11.5 cm. After a test dose (4 ml 2% lidocaine), a top up of 15 ml 0.1% tomy may confirm. Whilst the Lockit rays were to indicate the paths of the bupivacaine with 2 pgml! fentanyl Clamp may be the ideal skin fixation for the non-obese patient, an efficient ‘non-slip’ catheter with suitable eye catheters, were was given and an infusion of the same not so obvious when greatly reduced solution was started at 10 ml.h'. This in size and reproduced for publication. produced good analgesia, which lasted looking at the films. Their comes dangerously close to questioning which The unfortunately ‘clear an uneventful pregnancy. Her in place with a Lock-IT epidural catheter clamp (SIMS Portex) to the our conclusion for approximately 90 min. At that time that if fixed firmly to the skin, epidural We would repeat of she had a block to T; on the left and Ti: on the right (tested with ethyl chloride). Further top up of 10 ml of we wish to point out a typographical epidural space and loop in the soft the same solution was given but with ‘gaffe’ in one of Carrie and Russell’s references (4), with regard to the spelling of the name of one of the tissues of the back. Consequently, a no effect on block height or analgesia. catheter such as that designed by Collier The catheter site was examined and the and Gatt in which the three lateral eyes catheter still found to be tethered at current authors! lie within 4 mm of the tip is potentially 11.5 cm. Her epidural was removed and advantageous re-sited without difficulty at L;,2. Once instance of C. B. Collier S. P Gatt Royal Hospital for Women, Sydney, Australia References 1 Collier CB, Gatt SP A new epidural catheter: Closer eyes for safety? Anaesthesia 1993; 48: 803-6. 2065 complications [1]. I present a case that Whatever on their illustrations to represent the course of the dye-filled epidural catheters. However, even with the current Finally, and with some amusement, 162 Wa apparently unmoved dislodgement. =) maximises ing at while that 4-5 cm a very clear white line has béen drawn overcome the occasional ahs ineffective evidence epidurograms from ‘some years ago’, positions is still to be developed to WG. Correspondence 2 Collier CB. An Atlas Of Epidurograms: catheters may cease to function due to their ability to be when pulled out compared with one where the lateral eyes are more again proximal. following the initial bolus dose but wore off after 1 h despite an infusion The typographic error that converted the epidural block was good under our as before. It failed to improve following control. The spelling was correct in a further 10 ml bolus dose. Inspection “Gar” to ‘Gaff’ was not the manuscript submitted to Anaestheof the catheter site showed it to be still sia, but as readers are probably aware, in place. The patient did not wish to correspondents are not given the opportunity to see proofs of their letters have another epidural sited and received 150 mg intramuscular pethidine and before publication. had an uneventful vaginal delivery 90 min later. Epidural blocks investigated. Sydney: L. E. S. Carrie Harwood Academic, 1998. R. Russell but later behaved as if they had fallen John Radcliffe Hospital, out. When inspected, both remained Oxford, UK well fixed to the skin with no external evidence of catheter migration. It was A reply We are grateful fer the opportunity to reply to the letter by Drs Collier and Both epidurals initially worked well 7.5 cm from the skin to the epidural space, Gatt commenting on our study (Carrie Failed epidural in an obese patient - blame it on and Russell. Anaesthesia 2000; 55: 1231-3), although regret the need to Pythagoras! within the epidural space. The fact that epidurals failed would defend our findings. The whole point of reporting the study was to demonstrate the remarkable ability of epidural There is much debate regarding the there no catheter © 2001 Blackwell Science Ltd suggesting that there should have been 4 cm of catheter remaining both suggest that in the was optimal length of epidural catheter to remaining feed into the epidural space. Although implying significant catheter migration. epidural space,

Correspondence possible Anaesthesia, 2000, 56, pages 585-610 explanation is that the epidurals were sited with the patient's skin taught across her flexed lumbar Advantages and disadvantages became possible to remove the catheter of the Arrow Flex Tip Plus” epidural catheter with mild resistance and there was no breakage of the the patient sat back and the adipose Dr Goyal (Goyal. Anaesthesia 2001; 56: tissue 94-5) on her back was no longer catheter. This case indicates that it can spine. After the epidural was inserted, has drawn attention to the be difficult to withdraw the Arrow epidural catheter, even immediately following uncomplistretched out of the way. The distance usefulness of an Arrow FlexTip PlusTM cated insertion. from skin to epidural space is therefore epidural catheter, which contains a stainless-steel coil. As Dr Goyal points remove the catheter, it should be left in place and further attempts be made out, compared with conventional nonlater. likely to increase increase of 2cm significantly. would An leave only 2 cm of catheter within the epidural space. A shear force across her back produced by moving on her bed could easily have moved the skin site laterally relative to her spine. A 6-cm lateral movement of the skin site relative to her spine would have pulled the remaining 2 cm of epidural catheter out of the epidural space. (Pythagoras’ theory: In right-angled triangles the square upon the hypotenuse is equal to the sum of the squares of the two remaining sides.) On examination the following day, the patient was indeed found to have very lax tissues overlying her lumbar spine. With relatively gentle traction, the skin overlying her lumbar spine could be pulled more than 10 cm laterally. Epidural catheter migration has been positively correlated to body mass index [2]. In obese patients with significant adipose deposition across their back, | would advocate inserting a minimum of 6 cm of epidural catheter within the epidural space to reduce the chance of catheter migration leading to epidural failure. If it is difficult to reinforced catheters, it is easier to insert The advantages of the Arrow epidural the Arrow catheter with a lower incidence of paraesthesia or penetration catheter should be weighted against its of epidural veins [1]. However, there have been several reports of breakage of the Arrow catheter after difficulties in its removal [2-5]. Our previous ex vivo study has shown that the Arrow catheter snaps at a significantly lower weight than other conventional non-reinforced epidural catheters [2]. We report here another case of difficulty in removing an Arrow epidural catheter immediately after its insertion. A 29-year-old nurse was scheduled for urgent Caesarean section. With the patient in the right decubitus position and her back bend forward, the L:_3 disadvantages. T. Asai K. Shingu Kansai Medical University, 570-8501, Osaka, Japan References 1 Eanwell ER, Morley-Forster, P. Krause R. Decreased incidence of complications in parturients with the Arrow (FlexTip PlusTM) epidural catheter. Canadian Journal of Anaesthesia 1998; 45: 370-2. 2 Asai T, Yamamoto K, Hirose T, epidural space was easily located via a Taguchi H, Shingu K. Breakage of median approach using a 17-gauge Arrow Tuohy needle. A new 19-gauge Arrow reinforced catheter and other epidural catheters: a comparison of an Arrow catheter was passed through the non-reinforced catheters. Anesthesia and needle until the 13-cm mark on the Analgesia 2001; 92: 246-8. catheter just entered the Tuohy needle (that was 5 cm into the epidural space), 3 Woehlck HJ, Bolla B. Uncoiling of wire in Arrow Flextip epidural catheter and the needle was removed. Without on removal. Anesthesiology 2000; 92: changing the patient’s position, attempts were made to withdraw the catheter so that the distal 3-cm segment of the 907-9. 4 Hopf H-E, Leischik M. More on problems with removing the Arrow catheter was remaining in the epidural FlexTip epidural catheter: smooth in- C. Wasson space. However, it was impossible to hardly out? Anesthesiology 2000; 93: Bolton Royal Infirmary, withdraw and the catheter started to Bolton BL4 OJR, UK stretch. Changing the patients position 5 Fukukita K, Takemura M, Tanaka T. A did not relieve the problem. The patient severed spiral epidural catheter: a case was informed and the catheter was left report (Japanese text). Rhinsho-Masui in place. Nevertheless, injection of 2 ml (Japanese Journal of Clinical Anesthesia) of 2% mepivacaine (after negative aspir- 1998; 22: 966-8. References 1 Beilin Y, Bernstein HH, Zucker- Pinchoff B. The optimal distance that a multiorifice epidural catheter should be 1362. ation of blood or cerebrospinal fluid) produced regional analgesia. Another 15 ml of mepivacaine in divided doses A new interest in an old remedy threaded into the epidural space. Anesthesia and Analgesia 1995; 81: were injected and adequate analgesia was obtained. Epidural analgesia was for headache and backache for our obstetric patients: a 301-4. maintained after surgery. Two days later, sphenopalatine ganglion block 2 Bishton IM, Martin PH, Vernon JM, Liu WH. Factors influencing epidural attempts were made to remove the catheter migration. Anaesthesia 1992; catheter, but it was still difficult. Changing the patients position did not solve 47: 610-12. the problem. However, the next day it 606 Recently, we started using a sphenopalatine ganglion block [1] to treat our obstetric patients for moderate to severe © 2001 Blackwell Science Ltd