British Journal of Anaesthesia 1992; 68: 224-227
CORRESPONDENCE
M. McD. FISHER
St Leonards, N.S.W.
1.
2. 3.
4.
REFERENCES Baldo BA, Fisher MM. Detection of serum IgE antibodies that react with alcuronium and tubocurartine after lifethreatening reactions to muscle-relaxant drugs. Anaesthesia and Intensive Care 1983; 11: 194-197. Harle DG, Baldo BA, Fisher MM. Detection of IgE antibodies to suxamethonium after anaphylactoid reactions during anaesthesia. Lancet 1984; 1: 930-932. Harle DG, Baldo BA, Smal MA, Wajon P, Fisher MM. Detection of thiopentone-reactive IgE antibodies following anaphylactoid reactions during anaesthesia. Climes in Allergy 1986; 16: 493-^98. Assem ESK. In vivo and in vitro tests in anaphylactic reactions to anaesthetic agents. Agents Actions 1991; 33: 208-211.
REFERENCES 1. Wildsmith JAW. Regional anaesthesia requires attention to detail. British Journal of Anaesthesia 1991; 67: 224-225. 2. Taylor LJ. Are face-masks necessary in operating theatres and wards? Journal of Hospital Infection 1980; 1: 173-174. 3. Ruthman JC, Hendricksen D, Miller RF, Quigg DL. Effect of cap and mask on infection rates. Illinois Medical Journal 1984; 165: 397-399. 4. Laslett LJ, Sabin A. Wearing of caps and masks is not necessary during cardiac catheterization. Catheterization and Cardiovascular Diagnosis 1989; 17: 158-160. 5. Ritter MA, Eitzen H, French MLV, Hart JB. The operating room environment as affected by people and the surgical face mask. Clinical Orthopaedics 1975; 111: 147-150. 6. Ayliffe GAJ. Masks in surgery ? Journal of Hospital Infection 1991; 18: 165-166. 7. Schweizer RT. Mask wiggling as a potential cause of wound contamination. Lancet 1976; 2: 1129-1130. Sir,—Thank you for the opportunity of responding to Dr Yentis. Spinal anaesthesia is a technique that offers many advantages for many patients, but it does involve bypassing all the defence mechanisms provided for the central nervous system. The literature is full of examples of how catastrophic may be the results of inadvertent injection of anything but the intended local anaesthetic solution. Anyone who fails to learn the lessons provided by these examples is in serious danger of repeating them. My letter was written in response to a case report [1] of a patient who developed probable bacterial meningitis after a spinal anaesthetic. In the report it was admitted that a face mask had not been worn by the anaesthetist. In the absence of an alternative explanation, it must be assumed that a failure of aseptic technique resulted in the meningitis. I accept that there is much evidence that questions the use of face masks in many situations, but their use is almost universal in surgical practice. At the very least, they provide some form of physical barrier restricting the spread of paniculate matter from the anterior nares to the sterile field. I accept that an unfortunately large proportion of anaesthetists do not wear a face mask when performing spinal anaesthesia, but they do wear a face mask during the surgical procedure, even though they are a significant distance away from the wound. Where is the logic in that? As a final point, I would dispute absolutely that "published data support the widespread practice of not wearing masks" because there are no such data. J. A. W. WILDSMITH
Edinburgh WEARING OF FACE MASKS FOR SPINAL ANAESTHESIA Sir,—Dr Wildsmith states that, in his opinion, masks should always be worn when spinal or extradural anaesthesia is performed [1]. Such a statement has serious implications for those anaesthetists (in my experience, most) who do not routinely wear masks. There have been many studies of the efficacy of masks in preventing bacterial contamination and infection. These have shown that masks are of little use in ward work (including changing of dressings) [2], suturing of wounds [3], cardiac catheterization [4] and even surgery [5]. In particular, even transmission of Staphylococcus aureus from carriers is not thought to be prevented by the wearing of a mask [6]; masks might even increase the risk of infection by increasing the shedding of skin scales from the face [7]. The efficacy of masks has not been assessed specifically in spinal and extradural anaesthesia. However, despite Dr Wildsmith's dismissal of these studies as being irrelevant, the published data support the widespread practice of not wearing masks. S. M. YENTIS London
REFERENCE 1. Lee JJ, Parry H. Bacterial meningitis following spinal anaesthesia for Caesarean section. British Journal of Anaesthesia 1991; 66: 383-386.
POTASSIUM IN THE PERIOPERATIVE PERIOD Sir,—The article by Vaughan in the Postgraduate Education issue [1] prompts me to write on a topic which has exercised my mind for some time. Vaughan stated: "The recommended maximum rates of infusion of potassium are 10-20 mmol h~l, with a maximum of 500 mmol 24 h" 1 ." The statement is not referenced and the author can justifiably claim that this is a "standard" and well accepted piece of advice which follows similar recommendations by other reviewers. My problem is that it does not coincide with my understanding of basic physiology and biochemistry, and I have been searching for the evidence on which this standard opinion is based. In a review on the same topic by Lunn and Vaughan [2], the similar recommendation (15-20 mmol h"1 and a maximum of 400-500 mmol daily) was attributable to a 1969 paper [3] which was
Downloaded from http://bja.oxfordjournals.org/ at University of Michigan on June 25, 2015
RADIOIMMUNOASSAY TESTS IN ANAPHYLAXIS Sir,—Radioimmunoassay tests (RIA) for neuromuscular blocking drugs and thiopentone have been used by several laboratories to investigate anaphylactoid reactions during anaesthesia [1-3]. The development by Pharmacia of a simple version of these tests, in which the antigen is coupled to paper, is a welcome addition to these studies, allowing the investigation of patients in other than specialized laboratories, and a study published recently has clearly demonstrated the efficacy of these tests [4]. In studies in our laboratories comparing the commercial radioallergosorbent test with published methods, we were able to detect only one positive RIA in 31 patients who had undergone a life-threatening reaction during anaesthesia and had positive skin tests and RIA tests (using published methods) to a drug administered at the time of the reaction. These results were probably batch-related. My concern over these findings was increased by our recent involvement in two medico-legal cases in the United Kingdom in which the question of whether anaphylaxis had occurred or not was a critical issue. In both cases we found strong positive RIA to a drug used at the time of the adverse event which also was prick-test positive, while results from another laboratory using the commercial RIA were equivocal in one case and negative in the other. In the interests of safe subsequent anaesthesia in reacting patients, and particularly where RIA tests are used as evidence in medico-legal cases, results from a known RIA-positive patient should be used as a control to separate true negatives from false negatives when the paper RIA is used.
CORRESPONDENCE
M. McD. FISHER
St Leonards, N.S.W.
1.
2. 3.
4.
REFERENCES Baldo BA, Fisher MM. Detection of serum IgE antibodies that react with alcuronium and tubocurartine after lifethreatening reactions to muscle-relaxant drugs. Anaesthesia and Intensive Care 1983; 11: 194-197. Harle DG, Baldo BA, Fisher MM. Detection of IgE antibodies to suxamethonium after anaphylactoid reactions during anaesthesia. Lancet 1984; 1: 930-932. Harle DG, Baldo BA, Smal MA, Wajon P, Fisher MM. Detection of thiopentone-reactive IgE antibodies following anaphylactoid reactions during anaesthesia. Climes in Allergy 1986; 16: 493-^98. Assem ESK. In vivo and in vitro tests in anaphylactic reactions to anaesthetic agents. Agents Actions 1991; 33: 208-211.
REFERENCES 1. Wildsmith JAW. Regional anaesthesia requires attention to detail. British Journal of Anaesthesia 1991; 67: 224-225. 2. Taylor LJ. Are face-masks necessary in operating theatres and wards? Journal of Hospital Infection 1980; 1: 173-174. 3. Ruthman JC, Hendricksen D, Miller RF, Quigg DL. Effect of cap and mask on infection rates. Illinois Medical Journal 1984; 165: 397-399. 4. Laslett LJ, Sabin A. Wearing of caps and masks is not necessary during cardiac catheterization. Catheterization and Cardiovascular Diagnosis 1989; 17: 158-160. 5. Ritter MA, Eitzen H, French MLV, Hart JB. The operating room environment as affected by people and the surgical face mask. Clinical Orthopaedics 1975; 111: 147-150. 6. Ayliffe GAJ. Masks in surgery ? Journal of Hospital Infection 1991; 18: 165-166. 7. Schweizer RT. Mask wiggling as a potential cause of wound contamination. Lancet 1976; 2: 1129-1130. Sir,—Thank you for the opportunity of responding to Dr Yentis. Spinal anaesthesia is a technique that offers many advantages for many patients, but it does involve bypassing all the defence mechanisms provided for the central nervous system. The literature is full of examples of how catastrophic may be the results of inadvertent injection of anything but the intended local anaesthetic solution. Anyone who fails to learn the lessons provided by these examples is in serious danger of repeating them. My letter was written in response to a case report [1] of a patient who developed probable bacterial meningitis after a spinal anaesthetic. In the report it was admitted that a face mask had not been worn by the anaesthetist. In the absence of an alternative explanation, it must be assumed that a failure of aseptic technique resulted in the meningitis. I accept that there is much evidence that questions the use of face masks in many situations, but their use is almost universal in surgical practice. At the very least, they provide some form of physical barrier restricting the spread of paniculate matter from the anterior nares to the sterile field. I accept that an unfortunately large proportion of anaesthetists do not wear a face mask when performing spinal anaesthesia, but they do wear a face mask during the surgical procedure, even though they are a significant distance away from the wound. Where is the logic in that? As a final point, I would dispute absolutely that "published data support the widespread practice of not wearing masks" because there are no such data. J. A. W. WILDSMITH
Edinburgh WEARING OF FACE MASKS FOR SPINAL ANAESTHESIA Sir,—Dr Wildsmith states that, in his opinion, masks should always be worn when spinal or extradural anaesthesia is performed [1]. Such a statement has serious implications for those anaesthetists (in my experience, most) who do not routinely wear masks. There have been many studies of the efficacy of masks in preventing bacterial contamination and infection. These have shown that masks are of little use in ward work (including changing of dressings) [2], suturing of wounds [3], cardiac catheterization [4] and even surgery [5]. In particular, even transmission of Staphylococcus aureus from carriers is not thought to be prevented by the wearing of a mask [6]; masks might even increase the risk of infection by increasing the shedding of skin scales from the face [7]. The efficacy of masks has not been assessed specifically in spinal and extradural anaesthesia. However, despite Dr Wildsmith's dismissal of these studies as being irrelevant, the published data support the widespread practice of not wearing masks. S. M. YENTIS London
REFERENCE 1. Lee JJ, Parry H. Bacterial meningitis following spinal anaesthesia for Caesarean section. British Journal of Anaesthesia 1991; 66: 383-386.
POTASSIUM IN THE PERIOPERATIVE PERIOD Sir,—The article by Vaughan in the Postgraduate Education issue [1] prompts me to write on a topic which has exercised my mind for some time. Vaughan stated: "The recommended maximum rates of infusion of potassium are 10-20 mmol h~l, with a maximum of 500 mmol 24 h" 1 ." The statement is not referenced and the author can justifiably claim that this is a "standard" and well accepted piece of advice which follows similar recommendations by other reviewers. My problem is that it does not coincide with my understanding of basic physiology and biochemistry, and I have been searching for the evidence on which this standard opinion is based. In a review on the same topic by Lunn and Vaughan [2], the similar recommendation (15-20 mmol h"1 and a maximum of 400-500 mmol daily) was attributable to a 1969 paper [3] which was
Downloaded from http://bja.oxfordjournals.org/ at University of Michigan on June 25, 2015
RADIOIMMUNOASSAY TESTS IN ANAPHYLAXIS Sir,—Radioimmunoassay tests (RIA) for neuromuscular blocking drugs and thiopentone have been used by several laboratories to investigate anaphylactoid reactions during anaesthesia [1-3]. The development by Pharmacia of a simple version of these tests, in which the antigen is coupled to paper, is a welcome addition to these studies, allowing the investigation of patients in other than specialized laboratories, and a study published recently has clearly demonstrated the efficacy of these tests [4]. In studies in our laboratories comparing the commercial radioallergosorbent test with published methods, we were able to detect only one positive RIA in 31 patients who had undergone a life-threatening reaction during anaesthesia and had positive skin tests and RIA tests (using published methods) to a drug administered at the time of the reaction. These results were probably batch-related. My concern over these findings was increased by our recent involvement in two medico-legal cases in the United Kingdom in which the question of whether anaphylaxis had occurred or not was a critical issue. In both cases we found strong positive RIA to a drug used at the time of the adverse event which also was prick-test positive, while results from another laboratory using the commercial RIA were equivocal in one case and negative in the other. In the interests of safe subsequent anaesthesia in reacting patients, and particularly where RIA tests are used as evidence in medico-legal cases, results from a known RIA-positive patient should be used as a control to separate true negatives from false negatives when the paper RIA is used.
