British Journal of Anaesthesia 1992; 69. 542-545
CORRESPONDENCE
TABLE I. Number of successful retrograde intubations (total number and number at first attempt) and of cases of vocal cord damage, in 77 cadavers allocated to four groups with regard to site of puncture and mode of catheter insertion into the tracheal tube (either through the lumen (ET) or only through the Murphy eye) Successful intubations n
Group 1 Cricothyroid puncture + ET Group 2 Cricothyroid puncture + Murphy eye Group 3 Cricotracheal puncture + ET Group 4 Cricotracheal puncture + Murphy eye Total
Total
First attempt
17
5
4
20
15
11
20
14
13
20
20
17
77
54
45
Vocal cord damage
3
0
2. Lieu JC, Forrler M, Forrler C, Pottecher C. L'intubation oro-tracheaele par voie retrograde. Annales Francoises a"Ancsthe'sie et de Reanimation 1989; 8: 632-635. Sir,—We have been using retrograde methods for almost 25 yr. We have seen almost every complication as reported in the article [1]. Haematoma is not an uncommon complication. There are reports of intratracheal bleeding when this route is used for aspiration, resulting in serious, life-threatening complications [2-5]. Of course, I agree with Dr Lieu and his group that bleeding into the trachea is rare, but haematoma and formation of subcutaneous emphysema, although perhaps unnoticed, are not uncommon. We did have a case of massive goitre. All methods of intubation, including a fibreoptic bronchoscope, failed; the cricothyroid membrane was exposed by a small incision, enlarged blood vessels on the membrane were tied and a retrograde method was used successfully to inrubate, avoiding the necessity for tracheostomy. The subcricoid region is difficult to use if there is a mass goitre. We had cases of a prolonged change in voice and feeling of soreness after a somewhat traumatic retrograde intubation using the cricothyroid region. This was not the case when the subcricoid region was used. I am happy to note that cadaver studies do agree with our and other reports of ease of intubating using the subcricoid region [1, 6, 7]. We have used the subcricoid retrograde method for difficult intubations successfully since 1982, with minimal complications [1]. I am sure that the incidence of damage to vocal cords and subglottic oedema may be much greater than 8 % if intubation is performed on live patients using the cricothyroid region. I conclude that, when all other methods to inrubate the larynx fail, the subcricoid retrograde method is the best and least complex available. T. R. SHANTHA
Atlanta 1. Shantha TR. Retrograde intubation using the subcricoid region. British Journal of Anaesthesia 1992; 68: 109-112. 2. Akinyemi OO, John A. Complications of guided blind endotracheal intubation. Anaesthesia 1974; 29: 733-735. 3. Kalinske RW, Parker RH, Brandt D, Hoeprich TD. Diagnostic usefulness and safety of transtracheal aspiration. New England Journal of Medicine 1967; 276: 604-608. 4. Massey JY. Complications of transtracheal aspirate: A case report. Journal of the Arkansas Medical Society 1971; 67: 254-256. 5. Poon YK. Case History Number 89: A life-threatening complication of cricothyroid membrane puncture. Anesthesia and Analgesia 1976; 55: 298-301. 6. Abou-Madi MN, Trop D. Pulling versus guiding: A modification of retrograde guided intubation. Canadian Journal of Anaesthesia 1989; 36: 336-339. 7. Lieu JC, Forrler M, Forrler C, Pottecher C. L'intubation oro-trachcalc par voie retrograde. Annales Francoises a"Anaesthesie et de Reanimation 1989; 8: 632-635.
3
in group 4. This was significantly different from those in other groups. Damage to a vocal cord occurred only with the cricothyroid route (8 % of cases). J. C. LLEU M . FORRLER T . POTTECHER J. C. OTTENI
Strasbourg 1. Shantha TR. Retrograde intubation using the subcricoid region. British Journal of Anaesthesia 1992; 68: 109-112.
VENTILATORY EFFECTS OF LAPAROSCOPY UNDER GENERAL ANAESTHESIA Sir,—The study by Puri and Singh [1] is well designed and a valuable contribution to our knowledge of respiratory physiology. However, we wish to make the following comments on this subject, as we were involved in previous studies utilizing similar methodology in pregnant subjects [2-4]. The haemodynamic changes during laparoscopy also are important in the interpretation of arterial to end-tidal differences in carbon dioxide tension (Pa^-PE'^,,) values and the relevant data have not been presented. Studies have shown that laparoscopy may be associated with increases in cardiac output and
Downloaded from http://bja.oxfordjournals.org/ at University of Winnipeg on August 13, 2015
RETROGRADE INTUBATION USING THE SUBCRICOID REGION Sir,—Dr Shantha recommends puncture of the cricotracheal instead of the cricothyroid ligament for retrograde intubation, because he believes that bleeding complications may be avoided and the risks of subglottic oedema and stenosis decreased [1]. However, to our knowledge, these arguments have not yet been substantiated. In the presence of venous stasis, a frequent occurrence with difficult intubation, the incidence of bleeding at the puncture site is probably at least as frequent. Moreover, the subcricoid approach is more difficult or impossible in the obese, in the presence of goitre or cervical haematoma. In common with Dr Shantha, we recommend the subcricoid route but for the following reasons: it has the greatest success rate with the guide threaded through the Murphy eye; it carries the smallest risk of damage to a vocal cord by the needle or the catheter; and it allows a deeper tracheal penetration of the trachea! rube, thus decreasing the risk of accidental exrubation at catheter removal. These data were obtained during a study by our group published in a French journal of anaesthesia in 1989 [2]. Our study included 77 cadavers of adults who had died less than 4 h previously and were devoid of morphological causes of difficult intubation. They were allocated randomly to four groups depending on the site of puncture (cricothyroid ligament = groups 1 and 2; cricotracheal ligament = groups 3 and 4) and the mode of catheter insertion (complete tracheal tube lumen catheterization = groups 1 and 3; only Murphy eye catheterization = groups 2 and 4). We used a Tuohy needle (17-gauge) with the corresponding extradural catheter. After the intubating manoeuvre, the airways were dissected and checked for local damage. The results (table I) demonstrated a success rate of 100 %
CORRESPONDENCE
543
arterial pressure [5, 6], and changes in cardiovascular dynamics could result in changes in V/£> state in the lung and hence in Second, in the absence of capnographic recordings, the authors could have estimated the components of physiological deadspace using traditional formulae [4,7] instead of speculating that anatomical deadspace may have decreased during laparoscopy. Finally, negative values of (PaCOl-.PE'COi) n a v c D e e n observed during anaesthesia in pregnant subjects (50%), in infants (50%) and in patients after cardiac bypass surgery (8.1%) [8]. The increased cardiac output and increased carbon dioxide production, reduced FRC and low compliance are factors that have been implicated in the production of negative values. Therefore, one would be interested to know the incidence of negative values, particularly during stage II of Puri and Singh's study where, after insufflation of carbon dioxide into the peritoneum, the subjects may resemble the pregnant in some features, namely reduced FRC, low compliance and increased carbon dioxide production. K. B. SHANKAR A. Y. KUMAR H. MOSELEY
1. Puri GD, Singh H. Ventilatory effects of laparoscopy under general anaesthesia. British Journal of Anaesthesia 1992; 68: 211-213. 2. Shankar KB, Moseley H, Kumar Y, Vemula V. Arterial to end-tidal carbon dioxide tension difference during Caesarean section anaesthesia. Anaesthesia 1986; 41: 698-702. 3. Shanker KB, Moseley H, Kumar Y, Vemula V, Krishnan A. Arterial to end-tidal carbon dioxide tension difference during anaesthesia for tubal ligations. Anaesthesia 1987; 42: 482-486. 4. Shanker KB, Moseley H, Vemula V, Kumar Y. Physiological dead space during general anaesthesia for Caesarean section. Canadian Journal of Anaesthesia 1987; 33: 373-376. 5. Liu SY, Leighton T, Davis I. Prospective analysis of cardiopulmonary responses to laparoscopic cholecystectomy. Journal of Laparoendoscopic Surgery 1991; 39: 241-246. 6. Kelman GR, Swapp GH, Smith I, Benjie RJ, Gordon NLM. Cardiac output and arterial blood gas during laparoscopy. British Journal of Anaesthesia 1972; 44: 1155-1162. 7. Hedenstierna G, McCarthy G. The effects of anaesthesia and intermittent positive pressure ventilation with different frequencies on the anatomical and alveolar deadspace. British Journal of Anaesthesia 1975; 47: 847-852. 8. Shankar KB, Moseley H, Kumar AY, Delph Y. Anaesthesia and capnometry. A review article. Canadian Journal of Anaesthesia 1992; 39: (In press).
Sir,—Although (•PaCOl-fE/cot) m individual patients changed at different stages of laparoscopy, there were no overall mean changes in (Pa^-PE'COi) at various stages of laparoscopy studied (indicated in table I of our paper [1]). Some of these individual changes in this difference may have resulted from the changes in haemodynamic state produced by increased PaCOt anc^ increase in intrathoracic pressure, but we did not study cardiac output and pulmonary artery pressure measurements as it was not ethically justified to insert a pulmonary artery catheter in a patient for diagnostic laparoscopy. Regarding the incidence of negative values of (Pa^-PE' m ,) there were three of 14 patients (21%) with negative values of (PacvPE'co^ a t stage I (before insufflation of carbon dioxide) and the number increased to five of 14 (35%) after insufflation (stage II) during laparoscopy, but the trend was not similar in all patients: it decreased in some, while increasing in others. Finding various fractions of physiological deadspace by the conventional formulae would have been a futile statistical exercise, as the derived values would not represent the actual anatomical and alveolar deadspaces [2]. -
-
-
G. D. PURI H. SINGH
Chandigarh, India 1. Puri GD, Singh H. Ventilatory effects of laparoscopy under general anaesthesia. British Journal of Anaesthesia 1992; 68: 211-213.
EUROPEAN STANDARDIZATION COMMITTEE ON ANAESTHETIC EQUIPMENT Sir,—Our publication [1] on fresh gas utilization of eight circle systems was one of the first testing the new European CEN standard. Dr Greenbaum's statement [2] that our reference to the draft document of the CEN/TC215 proposal was not authorized, is incorrect. As stated in the introduction of the proposal, the standard may be quoted with the approval of the Convenor of the working group or the Chairman. Approval for our publication was obtained from both before submitting the manuscript (the Chairmanship of the Technical Committee has changed in the meantime). As already mentioned, our publication describes a testing procedure under well defined circumstances and nothing else. It does not set performance limits. I have no knowledge of any other type testing standard which reliably evaluates the efficiency of anaesthesia systems. It is left to the member states of CEN to accept, alter or omit it completely from the final document. We consider it as essential that standards are discussed and evaluated by an international readership of various journals before they become accepted standards. In the past, too many standards have been designed in theory only and therefore tend to lack data for their applicability in clinical practice. By testing the standards we would hope, therefore to make a contribution towards avoiding such problems in the future. A. M. ZBINDEN
Bern, Svnlzerland 1. Zbinden AM, Feigenwinter P, Hutmacher M. Fresh gas utilization of eight circle systems. British Journal of Anaesthesia 1991; 67: 492^99. 2. Grcenbaum R, Sugg BR, Hayes B. European Standardization Committee on Anaesthetic Equipment. British Journal of Anaesthesia 1992; 68: 326.
RADIOIMMUNOASSAY TESTS AND ANAPHYLAXIS Sir,—Dr Fisher's letter [1] has raised doubts about the ability of the commercial paper radioallergosorbent tests (RAST) to categorize correctly patients who have suffered anaphylactic reactions when the commercial test is compared with their own laboratory methods. The documentation of false negatives with the commercial RAST is an important finding and suggests that diagnostic skin testing [2] also should be performed for appropriate drugs, particular if sera from known RAST-posirive patients are not available to validate the commercial tests. Another area of concern is the use of these RAST for screening before anaesthesia [3]. Here, because larger numbers of patients would be tested, the false positive rate, in addition to the false negative rate, would be important [4]. After a fatality in Aberdeen from presumed suxamethonium-induced anaphylaxis, a prospective pilot study was undertaken to ascertain the rate of false positive reactions. Serum from 206 patients presenting for elective surgery were analysed using commercial RAST (Pharmacia) to detect antibodies to thiopentone, suxamethonium and alcuronium. Eight (3.9 %), seven (3.4 %) and 20 (9.7 %) patients tested positive for these agents, respectively, in this patient sample. None of these patients was reported to have had adverse reactions. Moreover, one patient documented as having increased antibody titres to suxamethonium has undergone several uneventful anaesthetics which included that agent. This finding is at variance with Assem's assertion that "high RAST was always associated with a severe reaction" [5]. If these results are representative, the concerns of Fisher regarding the use of RAST for screening [3] and the conclusions of the Associationof Anaesthetist's Working Party that " there is no support for routine screening of patients for specific drug antibodies at present" [6], are upheld. I. McG. IMRAY T. M. S. REID D. W. NOBLE Aberdeen
Downloaded from http://bja.oxfordjournals.org/ at University of Winnipeg on August 13, 2015
Barbados
2. Fletcher R. Airway deadspace, end-tidal CO,, and Christian Bohr. Ada Anaesthesiologica Scandinavica 1984; 28: 408—411.
CORRESPONDENCE
TABLE I. Number of successful retrograde intubations (total number and number at first attempt) and of cases of vocal cord damage, in 77 cadavers allocated to four groups with regard to site of puncture and mode of catheter insertion into the tracheal tube (either through the lumen (ET) or only through the Murphy eye) Successful intubations n
Group 1 Cricothyroid puncture + ET Group 2 Cricothyroid puncture + Murphy eye Group 3 Cricotracheal puncture + ET Group 4 Cricotracheal puncture + Murphy eye Total
Total
First attempt
17
5
4
20
15
11
20
14
13
20
20
17
77
54
45
Vocal cord damage
3
0
2. Lieu JC, Forrler M, Forrler C, Pottecher C. L'intubation oro-tracheaele par voie retrograde. Annales Francoises a"Ancsthe'sie et de Reanimation 1989; 8: 632-635. Sir,—We have been using retrograde methods for almost 25 yr. We have seen almost every complication as reported in the article [1]. Haematoma is not an uncommon complication. There are reports of intratracheal bleeding when this route is used for aspiration, resulting in serious, life-threatening complications [2-5]. Of course, I agree with Dr Lieu and his group that bleeding into the trachea is rare, but haematoma and formation of subcutaneous emphysema, although perhaps unnoticed, are not uncommon. We did have a case of massive goitre. All methods of intubation, including a fibreoptic bronchoscope, failed; the cricothyroid membrane was exposed by a small incision, enlarged blood vessels on the membrane were tied and a retrograde method was used successfully to inrubate, avoiding the necessity for tracheostomy. The subcricoid region is difficult to use if there is a mass goitre. We had cases of a prolonged change in voice and feeling of soreness after a somewhat traumatic retrograde intubation using the cricothyroid region. This was not the case when the subcricoid region was used. I am happy to note that cadaver studies do agree with our and other reports of ease of intubating using the subcricoid region [1, 6, 7]. We have used the subcricoid retrograde method for difficult intubations successfully since 1982, with minimal complications [1]. I am sure that the incidence of damage to vocal cords and subglottic oedema may be much greater than 8 % if intubation is performed on live patients using the cricothyroid region. I conclude that, when all other methods to inrubate the larynx fail, the subcricoid retrograde method is the best and least complex available. T. R. SHANTHA
Atlanta 1. Shantha TR. Retrograde intubation using the subcricoid region. British Journal of Anaesthesia 1992; 68: 109-112. 2. Akinyemi OO, John A. Complications of guided blind endotracheal intubation. Anaesthesia 1974; 29: 733-735. 3. Kalinske RW, Parker RH, Brandt D, Hoeprich TD. Diagnostic usefulness and safety of transtracheal aspiration. New England Journal of Medicine 1967; 276: 604-608. 4. Massey JY. Complications of transtracheal aspirate: A case report. Journal of the Arkansas Medical Society 1971; 67: 254-256. 5. Poon YK. Case History Number 89: A life-threatening complication of cricothyroid membrane puncture. Anesthesia and Analgesia 1976; 55: 298-301. 6. Abou-Madi MN, Trop D. Pulling versus guiding: A modification of retrograde guided intubation. Canadian Journal of Anaesthesia 1989; 36: 336-339. 7. Lieu JC, Forrler M, Forrler C, Pottecher C. L'intubation oro-trachcalc par voie retrograde. Annales Francoises a"Anaesthesie et de Reanimation 1989; 8: 632-635.
3
in group 4. This was significantly different from those in other groups. Damage to a vocal cord occurred only with the cricothyroid route (8 % of cases). J. C. LLEU M . FORRLER T . POTTECHER J. C. OTTENI
Strasbourg 1. Shantha TR. Retrograde intubation using the subcricoid region. British Journal of Anaesthesia 1992; 68: 109-112.
VENTILATORY EFFECTS OF LAPAROSCOPY UNDER GENERAL ANAESTHESIA Sir,—The study by Puri and Singh [1] is well designed and a valuable contribution to our knowledge of respiratory physiology. However, we wish to make the following comments on this subject, as we were involved in previous studies utilizing similar methodology in pregnant subjects [2-4]. The haemodynamic changes during laparoscopy also are important in the interpretation of arterial to end-tidal differences in carbon dioxide tension (Pa^-PE'^,,) values and the relevant data have not been presented. Studies have shown that laparoscopy may be associated with increases in cardiac output and
Downloaded from http://bja.oxfordjournals.org/ at University of Winnipeg on August 13, 2015
RETROGRADE INTUBATION USING THE SUBCRICOID REGION Sir,—Dr Shantha recommends puncture of the cricotracheal instead of the cricothyroid ligament for retrograde intubation, because he believes that bleeding complications may be avoided and the risks of subglottic oedema and stenosis decreased [1]. However, to our knowledge, these arguments have not yet been substantiated. In the presence of venous stasis, a frequent occurrence with difficult intubation, the incidence of bleeding at the puncture site is probably at least as frequent. Moreover, the subcricoid approach is more difficult or impossible in the obese, in the presence of goitre or cervical haematoma. In common with Dr Shantha, we recommend the subcricoid route but for the following reasons: it has the greatest success rate with the guide threaded through the Murphy eye; it carries the smallest risk of damage to a vocal cord by the needle or the catheter; and it allows a deeper tracheal penetration of the trachea! rube, thus decreasing the risk of accidental exrubation at catheter removal. These data were obtained during a study by our group published in a French journal of anaesthesia in 1989 [2]. Our study included 77 cadavers of adults who had died less than 4 h previously and were devoid of morphological causes of difficult intubation. They were allocated randomly to four groups depending on the site of puncture (cricothyroid ligament = groups 1 and 2; cricotracheal ligament = groups 3 and 4) and the mode of catheter insertion (complete tracheal tube lumen catheterization = groups 1 and 3; only Murphy eye catheterization = groups 2 and 4). We used a Tuohy needle (17-gauge) with the corresponding extradural catheter. After the intubating manoeuvre, the airways were dissected and checked for local damage. The results (table I) demonstrated a success rate of 100 %
CORRESPONDENCE
543
arterial pressure [5, 6], and changes in cardiovascular dynamics could result in changes in V/£> state in the lung and hence in Second, in the absence of capnographic recordings, the authors could have estimated the components of physiological deadspace using traditional formulae [4,7] instead of speculating that anatomical deadspace may have decreased during laparoscopy. Finally, negative values of (PaCOl-.PE'COi) n a v c D e e n observed during anaesthesia in pregnant subjects (50%), in infants (50%) and in patients after cardiac bypass surgery (8.1%) [8]. The increased cardiac output and increased carbon dioxide production, reduced FRC and low compliance are factors that have been implicated in the production of negative values. Therefore, one would be interested to know the incidence of negative values, particularly during stage II of Puri and Singh's study where, after insufflation of carbon dioxide into the peritoneum, the subjects may resemble the pregnant in some features, namely reduced FRC, low compliance and increased carbon dioxide production. K. B. SHANKAR A. Y. KUMAR H. MOSELEY
1. Puri GD, Singh H. Ventilatory effects of laparoscopy under general anaesthesia. British Journal of Anaesthesia 1992; 68: 211-213. 2. Shankar KB, Moseley H, Kumar Y, Vemula V. Arterial to end-tidal carbon dioxide tension difference during Caesarean section anaesthesia. Anaesthesia 1986; 41: 698-702. 3. Shanker KB, Moseley H, Kumar Y, Vemula V, Krishnan A. Arterial to end-tidal carbon dioxide tension difference during anaesthesia for tubal ligations. Anaesthesia 1987; 42: 482-486. 4. Shanker KB, Moseley H, Vemula V, Kumar Y. Physiological dead space during general anaesthesia for Caesarean section. Canadian Journal of Anaesthesia 1987; 33: 373-376. 5. Liu SY, Leighton T, Davis I. Prospective analysis of cardiopulmonary responses to laparoscopic cholecystectomy. Journal of Laparoendoscopic Surgery 1991; 39: 241-246. 6. Kelman GR, Swapp GH, Smith I, Benjie RJ, Gordon NLM. Cardiac output and arterial blood gas during laparoscopy. British Journal of Anaesthesia 1972; 44: 1155-1162. 7. Hedenstierna G, McCarthy G. The effects of anaesthesia and intermittent positive pressure ventilation with different frequencies on the anatomical and alveolar deadspace. British Journal of Anaesthesia 1975; 47: 847-852. 8. Shankar KB, Moseley H, Kumar AY, Delph Y. Anaesthesia and capnometry. A review article. Canadian Journal of Anaesthesia 1992; 39: (In press).
Sir,—Although (•PaCOl-fE/cot) m individual patients changed at different stages of laparoscopy, there were no overall mean changes in (Pa^-PE'COi) at various stages of laparoscopy studied (indicated in table I of our paper [1]). Some of these individual changes in this difference may have resulted from the changes in haemodynamic state produced by increased PaCOt anc^ increase in intrathoracic pressure, but we did not study cardiac output and pulmonary artery pressure measurements as it was not ethically justified to insert a pulmonary artery catheter in a patient for diagnostic laparoscopy. Regarding the incidence of negative values of (Pa^-PE' m ,) there were three of 14 patients (21%) with negative values of (PacvPE'co^ a t stage I (before insufflation of carbon dioxide) and the number increased to five of 14 (35%) after insufflation (stage II) during laparoscopy, but the trend was not similar in all patients: it decreased in some, while increasing in others. Finding various fractions of physiological deadspace by the conventional formulae would have been a futile statistical exercise, as the derived values would not represent the actual anatomical and alveolar deadspaces [2]. -
-
-
G. D. PURI H. SINGH
Chandigarh, India 1. Puri GD, Singh H. Ventilatory effects of laparoscopy under general anaesthesia. British Journal of Anaesthesia 1992; 68: 211-213.
EUROPEAN STANDARDIZATION COMMITTEE ON ANAESTHETIC EQUIPMENT Sir,—Our publication [1] on fresh gas utilization of eight circle systems was one of the first testing the new European CEN standard. Dr Greenbaum's statement [2] that our reference to the draft document of the CEN/TC215 proposal was not authorized, is incorrect. As stated in the introduction of the proposal, the standard may be quoted with the approval of the Convenor of the working group or the Chairman. Approval for our publication was obtained from both before submitting the manuscript (the Chairmanship of the Technical Committee has changed in the meantime). As already mentioned, our publication describes a testing procedure under well defined circumstances and nothing else. It does not set performance limits. I have no knowledge of any other type testing standard which reliably evaluates the efficiency of anaesthesia systems. It is left to the member states of CEN to accept, alter or omit it completely from the final document. We consider it as essential that standards are discussed and evaluated by an international readership of various journals before they become accepted standards. In the past, too many standards have been designed in theory only and therefore tend to lack data for their applicability in clinical practice. By testing the standards we would hope, therefore to make a contribution towards avoiding such problems in the future. A. M. ZBINDEN
Bern, Svnlzerland 1. Zbinden AM, Feigenwinter P, Hutmacher M. Fresh gas utilization of eight circle systems. British Journal of Anaesthesia 1991; 67: 492^99. 2. Grcenbaum R, Sugg BR, Hayes B. European Standardization Committee on Anaesthetic Equipment. British Journal of Anaesthesia 1992; 68: 326.
RADIOIMMUNOASSAY TESTS AND ANAPHYLAXIS Sir,—Dr Fisher's letter [1] has raised doubts about the ability of the commercial paper radioallergosorbent tests (RAST) to categorize correctly patients who have suffered anaphylactic reactions when the commercial test is compared with their own laboratory methods. The documentation of false negatives with the commercial RAST is an important finding and suggests that diagnostic skin testing [2] also should be performed for appropriate drugs, particular if sera from known RAST-posirive patients are not available to validate the commercial tests. Another area of concern is the use of these RAST for screening before anaesthesia [3]. Here, because larger numbers of patients would be tested, the false positive rate, in addition to the false negative rate, would be important [4]. After a fatality in Aberdeen from presumed suxamethonium-induced anaphylaxis, a prospective pilot study was undertaken to ascertain the rate of false positive reactions. Serum from 206 patients presenting for elective surgery were analysed using commercial RAST (Pharmacia) to detect antibodies to thiopentone, suxamethonium and alcuronium. Eight (3.9 %), seven (3.4 %) and 20 (9.7 %) patients tested positive for these agents, respectively, in this patient sample. None of these patients was reported to have had adverse reactions. Moreover, one patient documented as having increased antibody titres to suxamethonium has undergone several uneventful anaesthetics which included that agent. This finding is at variance with Assem's assertion that "high RAST was always associated with a severe reaction" [5]. If these results are representative, the concerns of Fisher regarding the use of RAST for screening [3] and the conclusions of the Associationof Anaesthetist's Working Party that " there is no support for routine screening of patients for specific drug antibodies at present" [6], are upheld. I. McG. IMRAY T. M. S. REID D. W. NOBLE Aberdeen
Downloaded from http://bja.oxfordjournals.org/ at University of Winnipeg on August 13, 2015
Barbados
2. Fletcher R. Airway deadspace, end-tidal CO,, and Christian Bohr. Ada Anaesthesiologica Scandinavica 1984; 28: 408—411.
