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Sonographically guided coeliac plexus block
Clinical Radiology (1993) 47, 143 145
Correspondence Letters are published at the discretion of the Editor. Opinions expressed by correspondents are not necessarily those of the Editor. Unduly long letters may be returned to the authorsfor shortening. Letters in response to a paper may be sent to the author o f the paper so that the reply can be published in the same issue. Letters should be typed double spaced and should be signed by all authors personally. References should be given in the style specified in the Instructions to Authors at the front o f the Journal.
PATIENT M O N I T O R I N G IN RADIOLOGY SIR Dr Wright's recent letter in this journal [1] raises an important point. The Association of Anaesthetists recommend that a minimum standard of monitoring including the use of pulse oximetry should be applied when sedation is given for procedures even of brief duration outside the operating theatre [2]. The General Dental Council states that 'where intravenous and inhalational sedation techniques are employed, a suitably experienced practitioner may assume the responsibility of sedating the patient, as well as operating, provided that as a minimum requirement a second appropriate person is present throughout the procedure' [3]. It is also recognized that significant reductions in oxygen saturation may occur for at least an hour after sedation for a radiographic examination [4]. The days of Radiologists struggling alone with a sedated patient are clearly numbered, however it is unrealistic to expect an anaesthetic department to provide the level of cover Dr Wright suggests. A more realistic alternative would be to employ suitably trained nursing staffor operating department assistants to act under supervision of the radiologist. Increased emphasis on sedation, analgesia, anaesthetic and monitoring techniques may be necessary in the F R C R (Part 1) syllabus. Radiologists should be pressing for nationally agreed standards for monitoring, recovery facilities and staffing levels as a matter of urgency. This involves great expense, but then so does litigation. -
F. L. C L A R K E P. A. GAINES*
Department of Anaesthesia University of Sheffield Beech Hill Road Sheffield SIO 1LA and *Academic Departments of Radiology and Magnetic Resonance Imaging Royal Hallamshire Hospital Glossop Road Sheffield SIO 2JF
References
I Wright NB. Patient monitoring in radiology (letter). Clinical Radiology 1992;45:361. 2 Recommendations for standards of monitoring during anaesthesia and recovery. Reprinted October 1989. Association of Anaesthetists. 3 General anaesthesia, sedation and resuscitation in dentistry. Report of an expert working party prepared for the Standing Dental Advisory Committee, March 1990. 4 Murray AW, Morran CG, Kenney GNC, Anderson JR. Arterial oxygen saturation during upper gastrointestinal endoscopy: the effects o f a midazolam/pethidine combination. Gut 1990;31:270-273.
SONOGRAPHICALLY GUIDED COELIAC PLEXUS BLOCK S m - We read with interest the paper on sonographically guided coeliac plexus block [1]. The authors rightly express concern that the dose of lignocaine used reached the recommended maximum and that local anaesthetic toxicity was a potential problem. However, it should be remembered that the recommendation of a single maximum dose without regard to the site of injection is meaningless [2]. It is well known that the plasma concentration of local anaesthetic drugs varies considerably as a function of the site of injection; for example, intercostal block produces more than three times the maximum plasma concentration of lignocaine than is seen after local infiltration [3]. Prilocaine (Citanest, Astra) is an underutilized local anaesthetic [4] that may deserve a place in radiological practice. It has a similar potency and speed of onset of action to lignocaine but with a wider therapeutic
range [5]. A study in human volunteers [6] showed that there were no adverse effects following a 200 mg i.v. bolus o f prilocaine, which should give encouragement to those using local anaesthetics in vascular sites such as around the coeliac plexus. The 'maximum recommended dose' of prilocaine is 10 mg/kg for a single injection [7]. The limit is imposed as a result of a dose-related production of methaemoglobin by a metabolite of prilocaine (otoluidine) rather than cardiovascular or central nervous system depression as is the case with lignocaine. However, in clinical practice dosages in excess of 16 mg/kg are necessary to produce methaemoglobin levels capable of producing symptoms of hypoxia [8]. Methylene blue given intravenously in a dose of I mg/kg will effectively revert methaemoglobin levels to normal. Also, at s for a 50 ml vial of 1% prilocaine, it compares favourably with the price of i % lignocaine with adrenaline (Xylocaine, Astra) at s for a 20 ml vial [9]. In summary, we feel that prilocaine is a useful local anaesthetic for procedures performed in vascular areas or when large volumes o f local anaesthetic are required. The maximum dose allowed would be increased, while the risks of cardiovascular and central nervous system toxicity would be reduced. S. MORRIS Departments o f Anaesthetics and *Clinical Radiology S. J. MORRIS* University Hospital of Wales Heath Park Cardiff CF4 4XN
References
1 Das KM, Chapman AH. Sonographically guided coeliac plexus block. Clinical Radiology 1992;45:401-403. 2 Scott DB. Maximum recommended doses of local anaesthetic drugs. British Journal of Anaesthesia 1989;63:373-374. 3 Scott DB, Jebson P JR, Braid DP, Ortengren B, Frisch P. Factors affecting plasma levels oflignocaine and prilocaine. British Journal o f Anaesthesia 1972;44:1040 1049. Wildsmith JAW. Prilocaine - an underutilized local anaesthetic. Regional Anaesthesia 1985; 1O:155-159. Covino BG. Clinical pharmacology of local anaesthetic agents. In: Cousins MJ & Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain, 2nd ed. Philadelphia: Lippincott, 1988; I 11-144. 6 Englesson S, Eriksson E, Wahlqvist S, Ortengen B. Differences in tolerance to intravenous xyloeaine and citanest (L.67), a new local anaesthetic. Proceedings of the First European Congress of Anaesthesiology 1962; Proc. 2:206. 7 0 n j i Y, Tyuma I. Methaemoglobin formation by a local anaesthetic and some related compounds. Acta Anaesthesiologica Scandinavica 1965;XVI(Suppl.): 151-159. Crawford OB. Methaemoglobin in man following the use of prilocaine. Acta Anaesthesiologiea Scandinavica 1965;XVl(Suppl.): 183 187. British National Formulary 1992;23:462-463.
TRANSJUGULAR INTRAHEPATIC PORTOSYSTEMIC STENT SHUNT: WHICH METAL STENT? SIR- There is considerable clinical interest in this technique to stop variceal bleeding by creating an intrahepatic portosystemie shunt. The earliest report used the Palmaz stent, but it is not surprising that alternative metal stents have been introduced. We have recently used the Wallstent to decompress the portal system in a 73-year-old male, and believe it to be the first reported use o f this stent for transjugular intrahepatic portosystemic stent shunt in the UK.
Correspondence Letters are published at the discretion of the Editor. Opinions expressed by correspondents are not necessarily those of the Editor. Unduly long letters may be returned to the authorsfor shortening. Letters in response to a paper may be sent to the author o f the paper so that the reply can be published in the same issue. Letters should be typed double spaced and should be signed by all authors personally. References should be given in the style specified in the Instructions to Authors at the front o f the Journal.
PATIENT M O N I T O R I N G IN RADIOLOGY SIR Dr Wright's recent letter in this journal [1] raises an important point. The Association of Anaesthetists recommend that a minimum standard of monitoring including the use of pulse oximetry should be applied when sedation is given for procedures even of brief duration outside the operating theatre [2]. The General Dental Council states that 'where intravenous and inhalational sedation techniques are employed, a suitably experienced practitioner may assume the responsibility of sedating the patient, as well as operating, provided that as a minimum requirement a second appropriate person is present throughout the procedure' [3]. It is also recognized that significant reductions in oxygen saturation may occur for at least an hour after sedation for a radiographic examination [4]. The days of Radiologists struggling alone with a sedated patient are clearly numbered, however it is unrealistic to expect an anaesthetic department to provide the level of cover Dr Wright suggests. A more realistic alternative would be to employ suitably trained nursing staffor operating department assistants to act under supervision of the radiologist. Increased emphasis on sedation, analgesia, anaesthetic and monitoring techniques may be necessary in the F R C R (Part 1) syllabus. Radiologists should be pressing for nationally agreed standards for monitoring, recovery facilities and staffing levels as a matter of urgency. This involves great expense, but then so does litigation. -
F. L. C L A R K E P. A. GAINES*
Department of Anaesthesia University of Sheffield Beech Hill Road Sheffield SIO 1LA and *Academic Departments of Radiology and Magnetic Resonance Imaging Royal Hallamshire Hospital Glossop Road Sheffield SIO 2JF
References
I Wright NB. Patient monitoring in radiology (letter). Clinical Radiology 1992;45:361. 2 Recommendations for standards of monitoring during anaesthesia and recovery. Reprinted October 1989. Association of Anaesthetists. 3 General anaesthesia, sedation and resuscitation in dentistry. Report of an expert working party prepared for the Standing Dental Advisory Committee, March 1990. 4 Murray AW, Morran CG, Kenney GNC, Anderson JR. Arterial oxygen saturation during upper gastrointestinal endoscopy: the effects o f a midazolam/pethidine combination. Gut 1990;31:270-273.
SONOGRAPHICALLY GUIDED COELIAC PLEXUS BLOCK S m - We read with interest the paper on sonographically guided coeliac plexus block [1]. The authors rightly express concern that the dose of lignocaine used reached the recommended maximum and that local anaesthetic toxicity was a potential problem. However, it should be remembered that the recommendation of a single maximum dose without regard to the site of injection is meaningless [2]. It is well known that the plasma concentration of local anaesthetic drugs varies considerably as a function of the site of injection; for example, intercostal block produces more than three times the maximum plasma concentration of lignocaine than is seen after local infiltration [3]. Prilocaine (Citanest, Astra) is an underutilized local anaesthetic [4] that may deserve a place in radiological practice. It has a similar potency and speed of onset of action to lignocaine but with a wider therapeutic
range [5]. A study in human volunteers [6] showed that there were no adverse effects following a 200 mg i.v. bolus o f prilocaine, which should give encouragement to those using local anaesthetics in vascular sites such as around the coeliac plexus. The 'maximum recommended dose' of prilocaine is 10 mg/kg for a single injection [7]. The limit is imposed as a result of a dose-related production of methaemoglobin by a metabolite of prilocaine (otoluidine) rather than cardiovascular or central nervous system depression as is the case with lignocaine. However, in clinical practice dosages in excess of 16 mg/kg are necessary to produce methaemoglobin levels capable of producing symptoms of hypoxia [8]. Methylene blue given intravenously in a dose of I mg/kg will effectively revert methaemoglobin levels to normal. Also, at s for a 50 ml vial of 1% prilocaine, it compares favourably with the price of i % lignocaine with adrenaline (Xylocaine, Astra) at s for a 20 ml vial [9]. In summary, we feel that prilocaine is a useful local anaesthetic for procedures performed in vascular areas or when large volumes o f local anaesthetic are required. The maximum dose allowed would be increased, while the risks of cardiovascular and central nervous system toxicity would be reduced. S. MORRIS Departments o f Anaesthetics and *Clinical Radiology S. J. MORRIS* University Hospital of Wales Heath Park Cardiff CF4 4XN
References
1 Das KM, Chapman AH. Sonographically guided coeliac plexus block. Clinical Radiology 1992;45:401-403. 2 Scott DB. Maximum recommended doses of local anaesthetic drugs. British Journal of Anaesthesia 1989;63:373-374. 3 Scott DB, Jebson P JR, Braid DP, Ortengren B, Frisch P. Factors affecting plasma levels oflignocaine and prilocaine. British Journal o f Anaesthesia 1972;44:1040 1049. Wildsmith JAW. Prilocaine - an underutilized local anaesthetic. Regional Anaesthesia 1985; 1O:155-159. Covino BG. Clinical pharmacology of local anaesthetic agents. In: Cousins MJ & Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain, 2nd ed. Philadelphia: Lippincott, 1988; I 11-144. 6 Englesson S, Eriksson E, Wahlqvist S, Ortengen B. Differences in tolerance to intravenous xyloeaine and citanest (L.67), a new local anaesthetic. Proceedings of the First European Congress of Anaesthesiology 1962; Proc. 2:206. 7 0 n j i Y, Tyuma I. Methaemoglobin formation by a local anaesthetic and some related compounds. Acta Anaesthesiologica Scandinavica 1965;XVI(Suppl.): 151-159. Crawford OB. Methaemoglobin in man following the use of prilocaine. Acta Anaesthesiologiea Scandinavica 1965;XVl(Suppl.): 183 187. British National Formulary 1992;23:462-463.
TRANSJUGULAR INTRAHEPATIC PORTOSYSTEMIC STENT SHUNT: WHICH METAL STENT? SIR- There is considerable clinical interest in this technique to stop variceal bleeding by creating an intrahepatic portosystemie shunt. The earliest report used the Palmaz stent, but it is not surprising that alternative metal stents have been introduced. We have recently used the Wallstent to decompress the portal system in a 73-year-old male, and believe it to be the first reported use o f this stent for transjugular intrahepatic portosystemic stent shunt in the UK.