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The use of lignocaine in dental practice: results of a survey of a group of general and hospital dental practitioners
PII:
Journal of Dentistry, Vol. 25, No. 5, pp. 431433, 1997
SO300-5712(96)00062-O
0 1997ElsevierScienceLtd. All rights reserved Printed in Great Britain 0300-5712/97 $17.00+0.00
ELSEVIER
The use of lignocaine in dental practice: results of a survey of a group of general and hospital dental practitioners J. E. Rowson and P. M. Preshaw Department
of Oral and Maxiiiofacial
Surgery, 30 The Ropewalk,
Nottingham,
NGl 5DW, UK
ABSTRACT Objectives: This survey investigated whether dentists using lignocaine with adrenaline used aspiration
syringes or warming and assessedtheir knowledge of appropriate doses of these drugs. Methods: Sixty-two general dental practitioners (GDPs) and 26 hospital dental practitioners (HDPs) responded to a series of questions asked via telephone or direct interview. Results: Only 3% of dentists interviewed correctly calculated the amount of lignocaine (mg) in 2 ml of 2% lignocaine solution and none knew the safe dose expressed as mglkg body wt. All dentists were using a cartridge system and had an easily remembered maximum number of cartridges that they would administer. This number varied, but in all caseswas within the safe maximum dose recommended by the British National Formulary. The survey also showed that 63% of the GDPs were using self aspirating syringe systemsand approximately 50% considered warming the anaesthetic solution prior to injection to be beneficial. Conclusion: The results indicate that dentists may be found to be poor at calculating doses but are nevertheless unlikely to give inappropriate amounts of lignocaine to healthy adults. This indicates the relative safety of the cartridge system. The use of the self aspirating syringe is not universal in spite of recommendations for its use. Warming of the anaesthetic solution is popular. 0 1997Elsevier ScienceLtd. KEY WORDS:
Lignocaine,
J. Dent 1997; 25: 431-433
Local anaesthesia, (Received
Safety, Dental practice
5 December
1995; accepted 25 July 1996)
INTRODUCTION based local anaesthetic solutions are the most frequently administered drugs in dental practice and have been safely used for many years. They are administered using cartridge syringes, each cartridge containing between 1.8 and 2.2 ml of 2% lignocaine solution. It has been estimated that an individual dentist may administer approximately 70-80000 cartridges during his or her practising lifetime’. A previous survey’ suggests that doctors are often unaware of the dose of local anaesthesiathey are adminLignocaine
istering which may therefore be inappropriately high. In hospital medical practice cartridges are not often used
and solution is drawn up from stock vials. Any system Correspondence should be addressed to: Dr J. E. Rowson, Department of Oral and Maxillofacial Surgery, 30 The Ropewalk, Nottingham NGl 5DW, UK. Tel.: (0115) 924 9924, Ext. 48916.
of delivery which promotes the safe use of local anaesthetics in hospital practice would therefore be of benefit.
This study investigated whether a group of dental surgeons was informed as to the dose of local anaesthetic they administer
and hence whether inadvertent
overdose was likely. It also enquired about the use of self aspirating syringes3 and whether, as has been suggested4,dentists warm the solution before use.
METHODS The general dental practitioners (GDPs) on the Family Health Services Association list for Nottingham were asked if they would agree to be contacted by telephone and asked six questions about the use of local analgesia. Those who agreed were contacted directly and asked the questions (Table I). A total of 62 responses were
432
J, Dent. 1997; 25: No. 5
Table 1. Summary of the results of the survey
Number (%) giving a correct response Question How much lignocaine (mg) is there in 2 ml of a 2% solution? What is the safe dose (mg/kg) of lignocaine with adrenaline? What is the maximum number of cartridges of 2% lignocaine with adrenaline you would use in a 60 kg adult? What is the maximum safe dose (cartridges) of 2% lignocaine with adrenaline?
GDP
HDP
A//
Correct response
GDP
HDP
O(O) O(O) 62(100)
3(12) OK9 26(100)
3(3) O(O) 88 (100)
40 mg 6.4-9.6 mg/kg 12
2-12
4-8
59(95)
25(96)
84(95)
12
3-17
5-20
No 31 23
Yes 11 12
GDP Do you warm your local anaesthetic? Do you use a self aspirating syringe? GDP, general dental practitioner;
Range
Yes 31 39
HDP No 15 14
HDP, hospital dental practitioner.
obtained. Twenty-six of the hospital dental practitioners (HDPs) working in a University Dental Hospital on a particular day were asked the same set of questions. The latter included clinical and academic staff and covered all dental specialties. Values for dosage were taken from the British National Formulary’ and for the second question, following previous practice, a range of plus or minus 20% of the exact value was allowed2. The maximum dose of lignocaine with adrenaline to be used in a healthy adult was determined to be 25 ml of 2% solution, which equates to approximately 12 cartridges depending on the exact volume per cartridge.
RESULTS The results of the survey are shown in Table I. Only three HDPs and none of the GDPs were able to correctly calculate the amount (mg) of lignocaine in 2 ml of 2% lignocaine solution. Similarly, 87 out of 88 answered ‘don’t know’ to the question regarding the safe dose of lignocaine with adrenaline in mglkg body wt, one dentist giving an incorrect response. All dentists were able to respond without hesitation, however, to the questions relating to the use of anaesthetic solution in cartridges. Although three GDPs and one HDP thought that the maximum safe dose in cartridges was above the maximum quoted in the BNF, no dentist would have personally administered more than this safe limit. Thirty-one (50%) of the GDPs and 11 (42%) of HDPs reported warming their local anaesthetic prior to use. A wide variety of methods were employed to warm the cartridges including placing them under warm running water, holding them in a hand or pocket and using a baby bottle warmer. Only 12 (46%) HDPs used a self aspirating syringe routinely. By contrast, 39 (63%) of GDPs used self aspirating syringes.
DISCUSSION The recent death of a patient following the administration of dental local anaesthetic created media interest in the use of local anaesthetics in dental practice. There has been confusion, however, over the maximum number of cartridges of local anaesthetic solution which may be safely given6, and this has understandably caused concern for patients attending for dental treatment. It is not easy to obtain clear information regarding the maximum dose of lignocaine which may be administered in a given situation. The British National Formulary (BNF) states that for a healthy patient, no more than 200 mg of plain lignocaine and no more than 500 mg of lignocaine with adrenaline should be given. A 2.2 ml cartridge of 2% lignocaine solution contains 44 mg of lignocaine. Thus, a maximum of approximately five cartridges of plain lignocaine or 12 cartridges of lignocaine with adrenaline should be administered. This theoretical maximum number was known to 95% of dentists in the study with 100% indicating that they would use less than 12 cartridges in practice. The BNF reports that the maximum dose of adrenaline which should be administered to a fit and healthy patient is 500 ug. One 2.2 ml cartridge of local anaesthetic solution containing 1:80000 adrenaline contains a total of 2.75 x 10K5 g of adrenaline. Therefore over 18 cartridges would be required to exceed the maximum recommended dose. The BNF gives no indication of the maximum doses which may be safely used in children, the elderly or in debilitated patients. An alternative approach was described by Allen who published tables of maximum doses related to patients’ weight7. Malamed reported that a maximum dose of lignocaine (with adrenaline) of 4.4 mglkg body wt should be given’. This suggeststhat for a healthy 70 kg adult up to seven cartridges of lignocaine with adrenaline could be safely given but in a 30 kg child, however, the maximum would be three cartridges. In the elderly, apart from assessing their
Rowson and Preshaw: Use of lignocaine
weight, which can be well below the average 70 kg adult, there are more likely to be medical conditions indicating a further reduction in dose. A study into the use of local anaesthetic by doctors2 has shown that they are poor at performing dose calculations and a more recently reported study has confirmed this’. The dental surgeons included in the present study performed less well than their medical colleagues. This is not surprising since dentists use a restricted number of drugs and do not have to perform such calculations with any frequency in their day to day practice. The most important finding, however, is that even though no dentist knew the correct maximum dose in mg/kg, they all quoted limits of 12 or less as the most cartridges that they would use. This is within the safe maximum dose for lignocaine with adrenaline. In contrast, Scrimshire’ found in a survey of doctors that 46% would have given two or more times the maximum safe dose. It seemsthat cartridges have the important advantage that a simple ‘maximum number’ is easier to remember than dosesin weight per weight or weight per volume. It has been recommended that aspirating syringes be used for administering local anaesthetics in dentistry3. Although the majority of GDPs (63%) were using these systems,most hospital dentists were not. The reason for this may be inertia in the absence of reports of side effects in any number from the estimated 70 million or more local anaesthetics given each year in the UK alone. Notwithstanding this, the dangers of intravascular injection are very real”. Intra-arterial injection would appear to be less likely than intravenous injection, as the arteries tend to slip out of the way of the needle, unless firmly bound down to bone”. Intraarterial injection may be particularly perilous, however, due to the risk of reverse carotid flo~‘~,‘~. A recent study reported that warming anaesthetic solution to body temperature prior to injection reduces the discomfort of the procedure4. In the present study the methods of warming varied widely. The most common was to hold the cartridge under warm running water from the tap. Often, a hand or pocket was used to warm the cartridge, and seven GDPs used a baby’s bottle warmer. Conversely, other studies have reported that warming local anaesthetic solutions prior to injection makes no difference to the pain experienced by the patient’“,i5. Furthermore, it is only at temperatures of 15°C or less and 40°C or more that patients can correctly identify a temperature difference15.
Although dentists may be found to be poor at calculating drug doses, they are unlikely to administer
433
inappropriately high levels of local anaesthetics to healthy adults. The cartridge system of administration of local anaesthetics, which allows an easy to remember maximum number, would seem to promote safe use. Despite recommendations, self aspirating syringes are still not used universally. Recent design improvements may increase their use in time. Finally, warming remains popular although there is little evidence that this has an effect on reducing discomfort.
References 1. 2. 3. 4.
5.
6. I. 8. 9.
10. 11.
12.
13.
14.
Watson, A. K., Problems with local anaesthetics in Dentistry. Dental Update, 1988 (Suppl. l), 2-5. Scrimshire, J. A., Safe use of lignocaine. British Medical Journal, 1989, 298, 1494. Meechan, J. G. and Rood, 5. P., Aspiration in dental local anaesthesia. British Dental Journal, 1992, 172, 40. Davidson, J. A. H. and Boom, S. J.: Warming lignocaine to reduce pain associated with injection. British Medical Journal, 1992, 305, 617-618. British Medical Association and the Royal Pharmaceutical Society of Great Britain, British National Formulary, Vol. 26. BMA and Pharmaceutical Press, 1993, pp. 486470. British Dental Association News, Vol. 8, March 1995, p. 2. Allen, G. D., Dental Anaesthesia and Analgesia, 3rd edn. Williams & Wilkins, Baltimore, 1984. Malamed, S. F., Handbook of Local Anaesthesia, 3rd edn. Mosby Year Book Inc., St. Louis, 1990, pp. 263-364. Rolfe, S. and Harper, N. J. N., Ability of hospital doctors to calculate drug doses. British Medical Journal, 1995, 310, 1173-l 174. Meechan, J. G., Aspiration during dental local anaesthesia. Dental Update, 1988, (Suppl. 2) 14. Covino, B. G. and Vassallo, H. G., Local Anaesthetics. Mechanisms of Action and Use. Grune & Stratton, New York, 1976, pp. 1233148. Aldrete, J. A., Narang, R., Sada, T., Liem, S. T. and Miller, G. P., Reverse carotid blood flow - a possible explanation for some reactions to local anaesthetics. Journal of the American Dental Association, 1971, 94, 1142-l 145. Aldrete, J. A., Nicholson, J., Sada, T., Davison, W. and Garrastasu, G., Cephalic kinetics of intra-arterially injected lignocaine. Oral Surgery, Oral Medicine and Oral Pathology, 1977, 44, 1677172. Oikarinen, V. J., Ylipaavalniemi, P. and Evers, H., Pain
and temperature sensationsrelated to local analgesia. 15.
CONCLUSION
in dental practice
International Journal of Oral Surgery, 1975, 4, 151-156. Rood J. P., The temperature of local anaesthetic solutions. Journal of Dentistry, 1977, 5, 213-214.
Journal of Dentistry, Vol. 25, No. 5, pp. 431433, 1997
SO300-5712(96)00062-O
0 1997ElsevierScienceLtd. All rights reserved Printed in Great Britain 0300-5712/97 $17.00+0.00
ELSEVIER
The use of lignocaine in dental practice: results of a survey of a group of general and hospital dental practitioners J. E. Rowson and P. M. Preshaw Department
of Oral and Maxiiiofacial
Surgery, 30 The Ropewalk,
Nottingham,
NGl 5DW, UK
ABSTRACT Objectives: This survey investigated whether dentists using lignocaine with adrenaline used aspiration
syringes or warming and assessedtheir knowledge of appropriate doses of these drugs. Methods: Sixty-two general dental practitioners (GDPs) and 26 hospital dental practitioners (HDPs) responded to a series of questions asked via telephone or direct interview. Results: Only 3% of dentists interviewed correctly calculated the amount of lignocaine (mg) in 2 ml of 2% lignocaine solution and none knew the safe dose expressed as mglkg body wt. All dentists were using a cartridge system and had an easily remembered maximum number of cartridges that they would administer. This number varied, but in all caseswas within the safe maximum dose recommended by the British National Formulary. The survey also showed that 63% of the GDPs were using self aspirating syringe systemsand approximately 50% considered warming the anaesthetic solution prior to injection to be beneficial. Conclusion: The results indicate that dentists may be found to be poor at calculating doses but are nevertheless unlikely to give inappropriate amounts of lignocaine to healthy adults. This indicates the relative safety of the cartridge system. The use of the self aspirating syringe is not universal in spite of recommendations for its use. Warming of the anaesthetic solution is popular. 0 1997Elsevier ScienceLtd. KEY WORDS:
Lignocaine,
J. Dent 1997; 25: 431-433
Local anaesthesia, (Received
Safety, Dental practice
5 December
1995; accepted 25 July 1996)
INTRODUCTION based local anaesthetic solutions are the most frequently administered drugs in dental practice and have been safely used for many years. They are administered using cartridge syringes, each cartridge containing between 1.8 and 2.2 ml of 2% lignocaine solution. It has been estimated that an individual dentist may administer approximately 70-80000 cartridges during his or her practising lifetime’. A previous survey’ suggests that doctors are often unaware of the dose of local anaesthesiathey are adminLignocaine
istering which may therefore be inappropriately high. In hospital medical practice cartridges are not often used
and solution is drawn up from stock vials. Any system Correspondence should be addressed to: Dr J. E. Rowson, Department of Oral and Maxillofacial Surgery, 30 The Ropewalk, Nottingham NGl 5DW, UK. Tel.: (0115) 924 9924, Ext. 48916.
of delivery which promotes the safe use of local anaesthetics in hospital practice would therefore be of benefit.
This study investigated whether a group of dental surgeons was informed as to the dose of local anaesthetic they administer
and hence whether inadvertent
overdose was likely. It also enquired about the use of self aspirating syringes3 and whether, as has been suggested4,dentists warm the solution before use.
METHODS The general dental practitioners (GDPs) on the Family Health Services Association list for Nottingham were asked if they would agree to be contacted by telephone and asked six questions about the use of local analgesia. Those who agreed were contacted directly and asked the questions (Table I). A total of 62 responses were
432
J, Dent. 1997; 25: No. 5
Table 1. Summary of the results of the survey
Number (%) giving a correct response Question How much lignocaine (mg) is there in 2 ml of a 2% solution? What is the safe dose (mg/kg) of lignocaine with adrenaline? What is the maximum number of cartridges of 2% lignocaine with adrenaline you would use in a 60 kg adult? What is the maximum safe dose (cartridges) of 2% lignocaine with adrenaline?
GDP
HDP
A//
Correct response
GDP
HDP
O(O) O(O) 62(100)
3(12) OK9 26(100)
3(3) O(O) 88 (100)
40 mg 6.4-9.6 mg/kg 12
2-12
4-8
59(95)
25(96)
84(95)
12
3-17
5-20
No 31 23
Yes 11 12
GDP Do you warm your local anaesthetic? Do you use a self aspirating syringe? GDP, general dental practitioner;
Range
Yes 31 39
HDP No 15 14
HDP, hospital dental practitioner.
obtained. Twenty-six of the hospital dental practitioners (HDPs) working in a University Dental Hospital on a particular day were asked the same set of questions. The latter included clinical and academic staff and covered all dental specialties. Values for dosage were taken from the British National Formulary’ and for the second question, following previous practice, a range of plus or minus 20% of the exact value was allowed2. The maximum dose of lignocaine with adrenaline to be used in a healthy adult was determined to be 25 ml of 2% solution, which equates to approximately 12 cartridges depending on the exact volume per cartridge.
RESULTS The results of the survey are shown in Table I. Only three HDPs and none of the GDPs were able to correctly calculate the amount (mg) of lignocaine in 2 ml of 2% lignocaine solution. Similarly, 87 out of 88 answered ‘don’t know’ to the question regarding the safe dose of lignocaine with adrenaline in mglkg body wt, one dentist giving an incorrect response. All dentists were able to respond without hesitation, however, to the questions relating to the use of anaesthetic solution in cartridges. Although three GDPs and one HDP thought that the maximum safe dose in cartridges was above the maximum quoted in the BNF, no dentist would have personally administered more than this safe limit. Thirty-one (50%) of the GDPs and 11 (42%) of HDPs reported warming their local anaesthetic prior to use. A wide variety of methods were employed to warm the cartridges including placing them under warm running water, holding them in a hand or pocket and using a baby bottle warmer. Only 12 (46%) HDPs used a self aspirating syringe routinely. By contrast, 39 (63%) of GDPs used self aspirating syringes.
DISCUSSION The recent death of a patient following the administration of dental local anaesthetic created media interest in the use of local anaesthetics in dental practice. There has been confusion, however, over the maximum number of cartridges of local anaesthetic solution which may be safely given6, and this has understandably caused concern for patients attending for dental treatment. It is not easy to obtain clear information regarding the maximum dose of lignocaine which may be administered in a given situation. The British National Formulary (BNF) states that for a healthy patient, no more than 200 mg of plain lignocaine and no more than 500 mg of lignocaine with adrenaline should be given. A 2.2 ml cartridge of 2% lignocaine solution contains 44 mg of lignocaine. Thus, a maximum of approximately five cartridges of plain lignocaine or 12 cartridges of lignocaine with adrenaline should be administered. This theoretical maximum number was known to 95% of dentists in the study with 100% indicating that they would use less than 12 cartridges in practice. The BNF reports that the maximum dose of adrenaline which should be administered to a fit and healthy patient is 500 ug. One 2.2 ml cartridge of local anaesthetic solution containing 1:80000 adrenaline contains a total of 2.75 x 10K5 g of adrenaline. Therefore over 18 cartridges would be required to exceed the maximum recommended dose. The BNF gives no indication of the maximum doses which may be safely used in children, the elderly or in debilitated patients. An alternative approach was described by Allen who published tables of maximum doses related to patients’ weight7. Malamed reported that a maximum dose of lignocaine (with adrenaline) of 4.4 mglkg body wt should be given’. This suggeststhat for a healthy 70 kg adult up to seven cartridges of lignocaine with adrenaline could be safely given but in a 30 kg child, however, the maximum would be three cartridges. In the elderly, apart from assessing their
Rowson and Preshaw: Use of lignocaine
weight, which can be well below the average 70 kg adult, there are more likely to be medical conditions indicating a further reduction in dose. A study into the use of local anaesthetic by doctors2 has shown that they are poor at performing dose calculations and a more recently reported study has confirmed this’. The dental surgeons included in the present study performed less well than their medical colleagues. This is not surprising since dentists use a restricted number of drugs and do not have to perform such calculations with any frequency in their day to day practice. The most important finding, however, is that even though no dentist knew the correct maximum dose in mg/kg, they all quoted limits of 12 or less as the most cartridges that they would use. This is within the safe maximum dose for lignocaine with adrenaline. In contrast, Scrimshire’ found in a survey of doctors that 46% would have given two or more times the maximum safe dose. It seemsthat cartridges have the important advantage that a simple ‘maximum number’ is easier to remember than dosesin weight per weight or weight per volume. It has been recommended that aspirating syringes be used for administering local anaesthetics in dentistry3. Although the majority of GDPs (63%) were using these systems,most hospital dentists were not. The reason for this may be inertia in the absence of reports of side effects in any number from the estimated 70 million or more local anaesthetics given each year in the UK alone. Notwithstanding this, the dangers of intravascular injection are very real”. Intra-arterial injection would appear to be less likely than intravenous injection, as the arteries tend to slip out of the way of the needle, unless firmly bound down to bone”. Intraarterial injection may be particularly perilous, however, due to the risk of reverse carotid flo~‘~,‘~. A recent study reported that warming anaesthetic solution to body temperature prior to injection reduces the discomfort of the procedure4. In the present study the methods of warming varied widely. The most common was to hold the cartridge under warm running water from the tap. Often, a hand or pocket was used to warm the cartridge, and seven GDPs used a baby’s bottle warmer. Conversely, other studies have reported that warming local anaesthetic solutions prior to injection makes no difference to the pain experienced by the patient’“,i5. Furthermore, it is only at temperatures of 15°C or less and 40°C or more that patients can correctly identify a temperature difference15.
Although dentists may be found to be poor at calculating drug doses, they are unlikely to administer
433
inappropriately high levels of local anaesthetics to healthy adults. The cartridge system of administration of local anaesthetics, which allows an easy to remember maximum number, would seem to promote safe use. Despite recommendations, self aspirating syringes are still not used universally. Recent design improvements may increase their use in time. Finally, warming remains popular although there is little evidence that this has an effect on reducing discomfort.
References 1. 2. 3. 4.
5.
6. I. 8. 9.
10. 11.
12.
13.
14.
Watson, A. K., Problems with local anaesthetics in Dentistry. Dental Update, 1988 (Suppl. l), 2-5. Scrimshire, J. A., Safe use of lignocaine. British Medical Journal, 1989, 298, 1494. Meechan, J. G. and Rood, 5. P., Aspiration in dental local anaesthesia. British Dental Journal, 1992, 172, 40. Davidson, J. A. H. and Boom, S. J.: Warming lignocaine to reduce pain associated with injection. British Medical Journal, 1992, 305, 617-618. British Medical Association and the Royal Pharmaceutical Society of Great Britain, British National Formulary, Vol. 26. BMA and Pharmaceutical Press, 1993, pp. 486470. British Dental Association News, Vol. 8, March 1995, p. 2. Allen, G. D., Dental Anaesthesia and Analgesia, 3rd edn. Williams & Wilkins, Baltimore, 1984. Malamed, S. F., Handbook of Local Anaesthesia, 3rd edn. Mosby Year Book Inc., St. Louis, 1990, pp. 263-364. Rolfe, S. and Harper, N. J. N., Ability of hospital doctors to calculate drug doses. British Medical Journal, 1995, 310, 1173-l 174. Meechan, J. G., Aspiration during dental local anaesthesia. Dental Update, 1988, (Suppl. 2) 14. Covino, B. G. and Vassallo, H. G., Local Anaesthetics. Mechanisms of Action and Use. Grune & Stratton, New York, 1976, pp. 1233148. Aldrete, J. A., Narang, R., Sada, T., Liem, S. T. and Miller, G. P., Reverse carotid blood flow - a possible explanation for some reactions to local anaesthetics. Journal of the American Dental Association, 1971, 94, 1142-l 145. Aldrete, J. A., Nicholson, J., Sada, T., Davison, W. and Garrastasu, G., Cephalic kinetics of intra-arterially injected lignocaine. Oral Surgery, Oral Medicine and Oral Pathology, 1977, 44, 1677172. Oikarinen, V. J., Ylipaavalniemi, P. and Evers, H., Pain
and temperature sensationsrelated to local analgesia. 15.
CONCLUSION
in dental practice
International Journal of Oral Surgery, 1975, 4, 151-156. Rood J. P., The temperature of local anaesthetic solutions. Journal of Dentistry, 1977, 5, 213-214.