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NEW METHODS FOR STONE EXTRACTION IN UROLOGY
1377
she had been unwell for 2-3 years. 21/2 years she had had an attack of shingles, followed the previously next year by several months of severe stomatitis. She and her husband had lived in Africa for more than 6 years and neither had ever visited the USA, the Caribbean, or Zaire. Detailed questioning revealed none of the accepted risk factors for AIDS. Serum from the husband was positive for HTLV-III at a titre of 450.
Apparently
During management of the index case,
one of the nursing "needlestick" injury to the finger while resheathing a hypodermic needle on a syringe containing fresh blood drawn from an arterial line. This was not an ordinary needlestick injury, in that a small amount of blood may well have been injected. Thirteen days later a severe ’flulike illness developed with mild sore throat, headache, myalgia, and facial neuralgia. Four days later a macular, nonitchy rash appeared on the chest and trunk and spread to the neck and face. The macules were up to 1 cm in diameter and were not raised. This rash lasted for seven days. No antibiotics were taken before or during this period. General malaise persisted and severe arthralgia became a notable feature, requiring regular analgesia for sleep. There was no arthritis. Pyrexia up to 39 ° C persisted until the twentieth day of the illness, after which it resolved; recovery thereafter was uneventful. noted Generalised lymphadenopathy, throughout the illness, likewise resolved. Serum drawn twenty-seven days after the injury (two weeks after the onset of illness) was negative for anti-HTLV-III, but on days fortynine and fifty-seven the titres were 12 and 24. The specificity of this reactivity was confirmed by indirect immunofluorescence (Virus Reference Laboratory, Public Health Laboratory Service, Colindale) and by enzyme-linked immunosorbent assay (Centers for Disease Control, Atlanta). Investigations for other likely causes ofaglandular-fever-type syndrome were negative, including culture and serological investigation for Epstein-Barr virus, cytomegalovirus, rubella virus, and parvovirus infection. A formal social history was taken by an epidemiologist who could find no other recognised risk factors for acquisition of HTLV-III infection (Communicable Disease Surveillance Centre,
staff had
a
Colindale). Epidemiological
evidence is beginning to suggest that in AIDS differs epidemiologically from that in the Africa central USA and is being spread heterosexually. The rate of admission of male and female patients to hospitals with a diagnosis of AIDS is increasing to epidemic proportions. In the index case described here the disease was very likely to have been acquired in Africa. If the lack of risk factors in both husband and wife is accepted, questions arise as to the mode of transmission of the initial infection, irrespective of which of them may have acquired it first. It seems highly probable that the infection was transmitted heterosexually between them. The index case was certainly infective for the nurse; and, since the patient had been ill for 2-3 years she could presumably have transmitted the disease, if the right circumstances arose, throughout that period. A similar period of infectivity without apparent disease has been described for HTLV-III-infected blood donors. The disturbing feature, however, is the contrast with American experience with needlestick injuries, none of which has resulted in either disease or transmission (though we do not know how many involved microinjection of blood, as in the British incident). In view of the different epidemiology of AIDS in Africa, this incident raises the possibility that there may be differences in infectivity and other characteristics
between the viruses of American and African origin. The outside possibility of an insect vector has still to be examined. These events will cause many observers to reconsider the adequacy of the precautions taken both in nursing of AIDS patients and in handling of laboratory specimens. In view of the known epidemiology of AIDS in drug addicts, we should not be surprised that small volumes of blood are capable of transmitting HTLV-Ill. Nevertheless, it is curious that such transmission should be observed for the first time in the UK, when health care staff in the USA are so much more likely to encounter HTLV-III-related disease. While HTLV-III may have many epidemiological features in common with hepatitis B infection, we should not draw too much comfort from the comparison at this stage, when the life-long sequelae to HTLV-III infection remain unknown. The utmost care should be taken to avoid self-inoculation when handling blood and blood-products from patients with HTLV-III-related disease. This may be particularly important where the infection is likely to have been acquired in Africa.
NEW METHODS FOR STONE EXTRACTION IN UROLOGY CUTTING for stone is as ancient an art as surgery itself and the concept of a major operation for the removal of even a small stone was not questioned until a decade ago. The considerable morbidity, the prolonged hospital stay with weeks off work, together with the financial implications for both patient and health service were accepted albeit often grudgingly. Endourology, as they prefer to call it in America, has now arrived. This is controlled manipulation within a closed urinary tract, usually via a percutaneous
nephrostomy.’ We have been able
to
gain direct access
to
the inside of the
kidney, percutaneously, since 19552 and many thousands of drainage procedures have been performed in well-equipped departments of urology and radiology. It was thus a short step to enlarging the tract sufficiently to pass an endoscope and attempt to grab a stone within the kidney.3 With standard urological equipment such as cystoscopes, resectoscopes, and wire baskets there were many disappointments, but in successful cases the patient could be out of hospital in a few days and back to work immediately thereafter. The patient with recurrent stone formation could be helped by this method when thoughts would otherwise have been turning to ablative surgery. The breakthrough was the development of suitable, purpose-designed instruments-with much credit to a few resourceful and enthusiastic surgeons and radiologists together with the cooperation of the urological instrument makers.4,5 Some centres now offer a clinical service for removal of pelvi-caliceal stones by rigid percutaneous
nephrolithotomy techniques.
For
easily
accessible stones
EC, Smith AD Percutaneous stone extraction for 200 patients. J Urol 1984; 132: 437-38 2. Goodwin WE, Casey WC, Woolf W. Percutaneous trocar (needle) nephrostomy in hydronephrosis. JAMA 1955; 157: 891. 3. Fernstrom I, Johansson B Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10: 257. 4. Wickham JEA, Miller RA Percutaneous renal surgery Edinburgh: Churchill Livingstone, 1983. 5 Wickham JEA, Kellet MJ Percutaneous nephrolithotomy Br Med J 1981; 283: 1571. 1. White
1378
(renal pelvis and lower posterior calices) the success rate is as high as 95%.’ A percutaneous tract is established under local anaesthesia in one or two sessions and then under general anaesthesia, often with X-ray control, the tract is enlarged for the final assault on the calculi. Commonly now the whole procedure is done as a single session in the X-ray department. The larger or less accessible stones remained troublesome and more ingenuity was needed. Flexible instruments to go in and out of calices and various grasping aids were developed.6 Ultrasound or electrohydraulic disintegration, already available for bladder stones, was miniaturised and adapted for the kidney. The tip of the lithotripter is applied to the stone, which breaks into tiny fragments that can then be aspirated through a sucker. Some say that virtually all renal stones can be removed percutaneously.6 Small stones in the lower ureter have been accessible to wire Dormia baskets for a long time, but it has always been a lottery as to whether the basket will go up the ureter, engage the stone, or get stuck on the way out. The development of rigid ureteroscopes has changed all that. The ureteric orifice can be dilated, seemingly without harm, and the whole ureter inspected with this new instrument. A suitable sized stone can be caught and manipulated down the ureter under direct vision with an 80% chance of success without major complications.8 Alternatively the stone can be destroyed in situ with electrohydraulic pressure waves from a 1’ 6 mm probed On occasion, a combination of ureteroscopy and percutaneous nephrolithotomy may be needed to remove all the stones.’ The advantages of endoscopic stone removal have been enumerated in respect to the mortality, success rate, cost effectiveness, and applicability to recurrent stoneforming patients. The disadvantages are the investment in. both time and money and the probable early obsolescence of any instruments purchased today. So, should the techniques be available only in specialist referral centres or in all district general hospitals? Some enthusiasts suggest that conventional stone therapy is already obsolete, but the oldfashioned cutting for stone seems likely to continue for some time yet in most countries. There is more than a possibility that all the techniques mentioned so far will be rapidly outdated by the use of the "big banger"-more correctly extracorporeal shockwave lithotripsy (ESWL). This mighty machine delivers carefully aimed shock waves at stones within the kidney whilst the patient lies anaesthetised in a water bath. The stones are shattered to dust and pass down the ureter with little morbidity. In Germany more than a thousand patients have’ been treated in two centres in 3 years, with 90% of patients being stone-free 3-6 months after treatment. 10 Only 0 - 7% of patients needed a further operation for ureteric obstruction. If the fragments are too large to pass they can be removed by percutaneous nephrolithotomy. The proponents suggest that 60% of operations for renal stones and 30% of those for ureteric stones could be substituted by ESWL.ll .
6
Percutaneous removal of cahceal and other "inaccessible" stones: Results J Urol 1984, 132: 443-47. 7 Ford TF, Parkinson MC, Wickham JEA Clinical and experimental evaluation of ureteric dilation Br J Urol 1984; 56: 460-63. 8 Ford TF, Watson GM, Wickham JEA Transurethral ureteroscopic retrieval of ureteric stones Br J Urol 1983; 55: 626-28 9. Matouschek E The lithotrity of stones in the ureter under visual control. Eur Urol 1984; 10: 60-61. 10 Miller K, Fuchs G, Rassweiler J, Eisenberger F. Financial analysis, personnel planning and organizational requirements for the installation of a kidney lithotripter in a urological department. Eur Urol 1984, 10: 217-21. 11. Chaussy C, Schmiedt E, Jocham D, Schuller J, Brandl H. Extracorporeal shock wave lithotripsy (ESWL)-a tool for the routine management for stone patients? International symposium, Vienna, 1983, cited by Miller et al (ref 10).
Reddy PK, Lange PH, Hulbert JC, et al
Every cloud with a silver lining has a darker aspect and here it is cost. Buildings may need adapting, the machine needs installing, and personnel are needed to run it. Maintenance, insurance, and cost of electrodes all need to be taken into account. The lithotripter costs over f1 million and with an estimated 450 treatments per annum the running cost of each treatment is about f500.JO In Germany the cost saving in respect to hospital stay is in the region of 400 and each patient is saved some f160 in disability time. Finally, the point is made that fewer patients proceed
to
chronic
dialysis. JO In Britain these machines should leave more hospital beds for patients on the seemingly endless urological waiting-lists. CALAMITY AT BHOPAL UNTIL disaster struck, few people had heard of Seveso. The same could be said of the industrial capital of the central Indian state of Madhyar Pradesh, until the leak of lethal vapour from a chemical plant left at least 2000 people dead. Even more than a week after the incident, environmental scientists and toxicologists are still thumbing through the standard texts for a definitive statement about the medical aspects of the substance that escaped-just as they had done for dioxin. The most likely culprit at Bhopal is the highly reactive chemical intermediate methyl isocyanate (MIC). Organic isocyanates were first synthesised in 1849, but they came into commercial use in the 1930s. The application at the Union Carbide plant was the synthesis of the pesticide carbaryl (’Sevin’), the reaction product of 1-naphthol and MIC. Another in the carbamate group of pesticides with MIC as an intermediate is aldicarb; the MIC stored in Britain is used to make a herbicide. Other uses have been in the manufacture of polymers and coatings. MIC itself can be made from carbonyl chloride (phosgene) and methylamine, either for immediate use or, as at Bhopal, after storage. One estimate of US production in 1980 was 20 000 tons. MIC is no longer made in Britain but at Grimsby and at Bayer plants in Belgium and Germany it is kept in much smaller containers than the tank at Bhopal, holding an estimated 17 500 litres of MIC. The earliest descriptions from India of a creeping, deadly, yellow, choking vapour have inevitably reminded people of phosgene, which was kept at but not made at the Union Carbide plant. However, the company has denied that phosgene was the noxious agent and until investigations are complete it must be assumed that the vapour that escaped was MIC. MIC is a liquid, but its boiling point is low (around 40°C). It has a powerful odour, is inflammable, and in gaseous form is heavier than air; and it is toxic by both inhalation and by absorption through the skin. Standard laboratory safety texts,I,2 where they mention MIC at all, agree that it is intensely irritating to the eyes, nose, and throat, but only one specifically refers to the pulmonary oedema which, with corneal ulceration, is the most common severe effect to have been recorded at Bhopal. For example, one authority,3 noting the intense- toxicity of phosgene, with pulmonary oedema, breathlessness, and coughing up of frothy fluid, simply records that MIC irritates the respiratory system and eyes. In another book there is no entry, apart from a fire hazard 1.Sittig
M. Handbook of
toxic
and hazardous chemicals
New
Jersey. Noyes
Publications, 1981: 459. 2 Proctor NH, Hughes JP. Methyl isocyanate. In Chemical hazards of the workplace. Philadelphia: JB Lippincott, 1978: 348-49. 3. Bretherick L, ed. Hazards in the chemical laboratory, 3rd ed. London: Royal Society of
Chemistry,
1981.
she had been unwell for 2-3 years. 21/2 years she had had an attack of shingles, followed the previously next year by several months of severe stomatitis. She and her husband had lived in Africa for more than 6 years and neither had ever visited the USA, the Caribbean, or Zaire. Detailed questioning revealed none of the accepted risk factors for AIDS. Serum from the husband was positive for HTLV-III at a titre of 450.
Apparently
During management of the index case,
one of the nursing "needlestick" injury to the finger while resheathing a hypodermic needle on a syringe containing fresh blood drawn from an arterial line. This was not an ordinary needlestick injury, in that a small amount of blood may well have been injected. Thirteen days later a severe ’flulike illness developed with mild sore throat, headache, myalgia, and facial neuralgia. Four days later a macular, nonitchy rash appeared on the chest and trunk and spread to the neck and face. The macules were up to 1 cm in diameter and were not raised. This rash lasted for seven days. No antibiotics were taken before or during this period. General malaise persisted and severe arthralgia became a notable feature, requiring regular analgesia for sleep. There was no arthritis. Pyrexia up to 39 ° C persisted until the twentieth day of the illness, after which it resolved; recovery thereafter was uneventful. noted Generalised lymphadenopathy, throughout the illness, likewise resolved. Serum drawn twenty-seven days after the injury (two weeks after the onset of illness) was negative for anti-HTLV-III, but on days fortynine and fifty-seven the titres were 12 and 24. The specificity of this reactivity was confirmed by indirect immunofluorescence (Virus Reference Laboratory, Public Health Laboratory Service, Colindale) and by enzyme-linked immunosorbent assay (Centers for Disease Control, Atlanta). Investigations for other likely causes ofaglandular-fever-type syndrome were negative, including culture and serological investigation for Epstein-Barr virus, cytomegalovirus, rubella virus, and parvovirus infection. A formal social history was taken by an epidemiologist who could find no other recognised risk factors for acquisition of HTLV-III infection (Communicable Disease Surveillance Centre,
staff had
a
Colindale). Epidemiological
evidence is beginning to suggest that in AIDS differs epidemiologically from that in the Africa central USA and is being spread heterosexually. The rate of admission of male and female patients to hospitals with a diagnosis of AIDS is increasing to epidemic proportions. In the index case described here the disease was very likely to have been acquired in Africa. If the lack of risk factors in both husband and wife is accepted, questions arise as to the mode of transmission of the initial infection, irrespective of which of them may have acquired it first. It seems highly probable that the infection was transmitted heterosexually between them. The index case was certainly infective for the nurse; and, since the patient had been ill for 2-3 years she could presumably have transmitted the disease, if the right circumstances arose, throughout that period. A similar period of infectivity without apparent disease has been described for HTLV-III-infected blood donors. The disturbing feature, however, is the contrast with American experience with needlestick injuries, none of which has resulted in either disease or transmission (though we do not know how many involved microinjection of blood, as in the British incident). In view of the different epidemiology of AIDS in Africa, this incident raises the possibility that there may be differences in infectivity and other characteristics
between the viruses of American and African origin. The outside possibility of an insect vector has still to be examined. These events will cause many observers to reconsider the adequacy of the precautions taken both in nursing of AIDS patients and in handling of laboratory specimens. In view of the known epidemiology of AIDS in drug addicts, we should not be surprised that small volumes of blood are capable of transmitting HTLV-Ill. Nevertheless, it is curious that such transmission should be observed for the first time in the UK, when health care staff in the USA are so much more likely to encounter HTLV-III-related disease. While HTLV-III may have many epidemiological features in common with hepatitis B infection, we should not draw too much comfort from the comparison at this stage, when the life-long sequelae to HTLV-III infection remain unknown. The utmost care should be taken to avoid self-inoculation when handling blood and blood-products from patients with HTLV-III-related disease. This may be particularly important where the infection is likely to have been acquired in Africa.
NEW METHODS FOR STONE EXTRACTION IN UROLOGY CUTTING for stone is as ancient an art as surgery itself and the concept of a major operation for the removal of even a small stone was not questioned until a decade ago. The considerable morbidity, the prolonged hospital stay with weeks off work, together with the financial implications for both patient and health service were accepted albeit often grudgingly. Endourology, as they prefer to call it in America, has now arrived. This is controlled manipulation within a closed urinary tract, usually via a percutaneous
nephrostomy.’ We have been able
to
gain direct access
to
the inside of the
kidney, percutaneously, since 19552 and many thousands of drainage procedures have been performed in well-equipped departments of urology and radiology. It was thus a short step to enlarging the tract sufficiently to pass an endoscope and attempt to grab a stone within the kidney.3 With standard urological equipment such as cystoscopes, resectoscopes, and wire baskets there were many disappointments, but in successful cases the patient could be out of hospital in a few days and back to work immediately thereafter. The patient with recurrent stone formation could be helped by this method when thoughts would otherwise have been turning to ablative surgery. The breakthrough was the development of suitable, purpose-designed instruments-with much credit to a few resourceful and enthusiastic surgeons and radiologists together with the cooperation of the urological instrument makers.4,5 Some centres now offer a clinical service for removal of pelvi-caliceal stones by rigid percutaneous
nephrolithotomy techniques.
For
easily
accessible stones
EC, Smith AD Percutaneous stone extraction for 200 patients. J Urol 1984; 132: 437-38 2. Goodwin WE, Casey WC, Woolf W. Percutaneous trocar (needle) nephrostomy in hydronephrosis. JAMA 1955; 157: 891. 3. Fernstrom I, Johansson B Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10: 257. 4. Wickham JEA, Miller RA Percutaneous renal surgery Edinburgh: Churchill Livingstone, 1983. 5 Wickham JEA, Kellet MJ Percutaneous nephrolithotomy Br Med J 1981; 283: 1571. 1. White
1378
(renal pelvis and lower posterior calices) the success rate is as high as 95%.’ A percutaneous tract is established under local anaesthesia in one or two sessions and then under general anaesthesia, often with X-ray control, the tract is enlarged for the final assault on the calculi. Commonly now the whole procedure is done as a single session in the X-ray department. The larger or less accessible stones remained troublesome and more ingenuity was needed. Flexible instruments to go in and out of calices and various grasping aids were developed.6 Ultrasound or electrohydraulic disintegration, already available for bladder stones, was miniaturised and adapted for the kidney. The tip of the lithotripter is applied to the stone, which breaks into tiny fragments that can then be aspirated through a sucker. Some say that virtually all renal stones can be removed percutaneously.6 Small stones in the lower ureter have been accessible to wire Dormia baskets for a long time, but it has always been a lottery as to whether the basket will go up the ureter, engage the stone, or get stuck on the way out. The development of rigid ureteroscopes has changed all that. The ureteric orifice can be dilated, seemingly without harm, and the whole ureter inspected with this new instrument. A suitable sized stone can be caught and manipulated down the ureter under direct vision with an 80% chance of success without major complications.8 Alternatively the stone can be destroyed in situ with electrohydraulic pressure waves from a 1’ 6 mm probed On occasion, a combination of ureteroscopy and percutaneous nephrolithotomy may be needed to remove all the stones.’ The advantages of endoscopic stone removal have been enumerated in respect to the mortality, success rate, cost effectiveness, and applicability to recurrent stoneforming patients. The disadvantages are the investment in. both time and money and the probable early obsolescence of any instruments purchased today. So, should the techniques be available only in specialist referral centres or in all district general hospitals? Some enthusiasts suggest that conventional stone therapy is already obsolete, but the oldfashioned cutting for stone seems likely to continue for some time yet in most countries. There is more than a possibility that all the techniques mentioned so far will be rapidly outdated by the use of the "big banger"-more correctly extracorporeal shockwave lithotripsy (ESWL). This mighty machine delivers carefully aimed shock waves at stones within the kidney whilst the patient lies anaesthetised in a water bath. The stones are shattered to dust and pass down the ureter with little morbidity. In Germany more than a thousand patients have’ been treated in two centres in 3 years, with 90% of patients being stone-free 3-6 months after treatment. 10 Only 0 - 7% of patients needed a further operation for ureteric obstruction. If the fragments are too large to pass they can be removed by percutaneous nephrolithotomy. The proponents suggest that 60% of operations for renal stones and 30% of those for ureteric stones could be substituted by ESWL.ll .
6
Percutaneous removal of cahceal and other "inaccessible" stones: Results J Urol 1984, 132: 443-47. 7 Ford TF, Parkinson MC, Wickham JEA Clinical and experimental evaluation of ureteric dilation Br J Urol 1984; 56: 460-63. 8 Ford TF, Watson GM, Wickham JEA Transurethral ureteroscopic retrieval of ureteric stones Br J Urol 1983; 55: 626-28 9. Matouschek E The lithotrity of stones in the ureter under visual control. Eur Urol 1984; 10: 60-61. 10 Miller K, Fuchs G, Rassweiler J, Eisenberger F. Financial analysis, personnel planning and organizational requirements for the installation of a kidney lithotripter in a urological department. Eur Urol 1984, 10: 217-21. 11. Chaussy C, Schmiedt E, Jocham D, Schuller J, Brandl H. Extracorporeal shock wave lithotripsy (ESWL)-a tool for the routine management for stone patients? International symposium, Vienna, 1983, cited by Miller et al (ref 10).
Reddy PK, Lange PH, Hulbert JC, et al
Every cloud with a silver lining has a darker aspect and here it is cost. Buildings may need adapting, the machine needs installing, and personnel are needed to run it. Maintenance, insurance, and cost of electrodes all need to be taken into account. The lithotripter costs over f1 million and with an estimated 450 treatments per annum the running cost of each treatment is about f500.JO In Germany the cost saving in respect to hospital stay is in the region of 400 and each patient is saved some f160 in disability time. Finally, the point is made that fewer patients proceed
to
chronic
dialysis. JO In Britain these machines should leave more hospital beds for patients on the seemingly endless urological waiting-lists. CALAMITY AT BHOPAL UNTIL disaster struck, few people had heard of Seveso. The same could be said of the industrial capital of the central Indian state of Madhyar Pradesh, until the leak of lethal vapour from a chemical plant left at least 2000 people dead. Even more than a week after the incident, environmental scientists and toxicologists are still thumbing through the standard texts for a definitive statement about the medical aspects of the substance that escaped-just as they had done for dioxin. The most likely culprit at Bhopal is the highly reactive chemical intermediate methyl isocyanate (MIC). Organic isocyanates were first synthesised in 1849, but they came into commercial use in the 1930s. The application at the Union Carbide plant was the synthesis of the pesticide carbaryl (’Sevin’), the reaction product of 1-naphthol and MIC. Another in the carbamate group of pesticides with MIC as an intermediate is aldicarb; the MIC stored in Britain is used to make a herbicide. Other uses have been in the manufacture of polymers and coatings. MIC itself can be made from carbonyl chloride (phosgene) and methylamine, either for immediate use or, as at Bhopal, after storage. One estimate of US production in 1980 was 20 000 tons. MIC is no longer made in Britain but at Grimsby and at Bayer plants in Belgium and Germany it is kept in much smaller containers than the tank at Bhopal, holding an estimated 17 500 litres of MIC. The earliest descriptions from India of a creeping, deadly, yellow, choking vapour have inevitably reminded people of phosgene, which was kept at but not made at the Union Carbide plant. However, the company has denied that phosgene was the noxious agent and until investigations are complete it must be assumed that the vapour that escaped was MIC. MIC is a liquid, but its boiling point is low (around 40°C). It has a powerful odour, is inflammable, and in gaseous form is heavier than air; and it is toxic by both inhalation and by absorption through the skin. Standard laboratory safety texts,I,2 where they mention MIC at all, agree that it is intensely irritating to the eyes, nose, and throat, but only one specifically refers to the pulmonary oedema which, with corneal ulceration, is the most common severe effect to have been recorded at Bhopal. For example, one authority,3 noting the intense- toxicity of phosgene, with pulmonary oedema, breathlessness, and coughing up of frothy fluid, simply records that MIC irritates the respiratory system and eyes. In another book there is no entry, apart from a fire hazard 1.Sittig
M. Handbook of
toxic
and hazardous chemicals
New
Jersey. Noyes
Publications, 1981: 459. 2 Proctor NH, Hughes JP. Methyl isocyanate. In Chemical hazards of the workplace. Philadelphia: JB Lippincott, 1978: 348-49. 3. Bretherick L, ed. Hazards in the chemical laboratory, 3rd ed. London: Royal Society of
Chemistry,
1981.