tract who develop acute papillary necrosis. Such patients will not present with renal failure if the contralateral kidney functions normally, and under these circumstances the diagnosis of an obstructed pyonephrosis can easily be delayed, with potentially serious consequences for renal function. If acute obstruction is suspected in the presence of infection a negative ultrasonogram is of no clinical value (and, as Dr Webb implies, a dilated collecting system will require further evaluation by other means). Such patients deserve urography, and if this shows a "non-functioning" kidney antegrade pyelography should be carried out, which can be followed by percutaneous drainage if obstruction is present. STEPHEN J AUSTIN Hospital for Sick Children, Great Ormond Street, London WCIN 3JH I Webb JAW. Ultrasonography in the diagnosis of renal obstruction. BMJ 1990;301:944-6. (27 October.)
AUTHOR'S REPLY,-I note Dr Austin's concern that no pelvicaliceal dilatation will be detected by ultrasonography in infected kidneys that are acutely obstructed, especially those in diabetic patients with acute papillary necrosis, and agree that this is theoretically possible. Nevertheless, I have not encountered this over the past 12 years, during which I have used ultrasonography to examine many obstructed infected kidneys, including some in diabetic patients with ureters obstructed by sloughed papillae.. Dr Austin suggests that urography is a better method than ultrasonography and that obstruction of an infected kidney should be suspected if there is no filling of the pelvicaliceal system with contrast medium. Unfortunately, this urographic sign is not specific for obstruction. Severe acute infection alone may also prevent the pelvicaliceal system from filling with contrast medium at urography. 2 JA W WEBB St Bartholomew's Hospital, London EClA 7BE I Davidson AJ, 'I'alner LB. Urographic anid angiographic abnormalities in adult-onset acute bacterial nephritis. Radiology
1973;106:249-56. 2 Teplick JG, Teplick SK, Berinson H, Hasken ME. Urographic and angiographic changes in acute unilateral pyelonephritis. Clin Radiol 1979;30:59-66.
clinical assessment of the severity of an attack. In elderly patients the absence of physical signs classically viewed as markers of acute severe asthma should not be seen as reassuring. MARTIN J CONNOLLY
Seacroft Hospital, Leeds LS14 6UH I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for the management of asthma in adults. 2. Acute severe asthma. BMJ 1990;301:797-800. (6 October.) 2 Petheram IS, Jones DA, Collins JV. Assessment and management of acute asthma in the elderly: a comparison with younger asthmatics. Postgrad MedJ 1982;58:149-51. 3 Connolly MJ, Crowley JJ, Vestal RE. Reduced awareness of methacholine-provoked bronchoconstriction in elderly asthmatics and normals. Age Ageing 1990;19(suppl 2):19. 4 Robin ED. Risk benefit analysis in chest medicine. Death from bronchial asthma. Chest 1988;93:614-8.
SIR,-The guidelines issued by the British Thoracic Society and others relegate oral theophyllines to a subsidiary role and strongly advise monitoring of blood or salivary concentrations because of the narrow therapeutic ratio.' Oral theophyllines are, however, still widely used in general practice in Britain, roughly three and a half million prescriptions being written annually. As serum theophylline concentrations are measured in hospital laboratories we surveyed the biochemistry laboratories in the North West Regional Health Authority to ascertain the level of monitoring in general practice. For the three months February to April 1990 the total number of estimations of theophylline concentrations (number requested by general practitioners) in each district was as follows: Salford 262 (24), Wigan 194 (6), North Manchester 170 (2), Blackburn 156 (4), Blackpool 123 (9), Central Manchester 102 (0), Burnley 90 (2), Oldham 80 (8), Preston 67 (6), Rochdale 47 (2), South Manchester 46 (1), Trafford 41 (4), Tameside 37 (4), Bolton 29 (3). Thus, general practitioners requested less than 5% of the total number of assays. Assuming the population of North West region to be four million, there are about 87 500 prescriptions of theophylline written each quarter.2 Thus, serum theophylline concentrations are estimated in general practice less than once per 1173 prescriptions. Slow release oral theophylline will continue to have a role in managing asthma in the 1990s, although this role is likely to diminish with the introduction of long acting inhaled bronchodilator drugs. Much more monitoring of serum theophylline concentrations in general practice is necessary if oral theophyllines are to be used safely.
Guidelines for management of asthma SIR,-The guidelines for the management of asthma in adults published by the British Thoracic Society and others fail to recognise the potential differences in the presentation of acute severe asthma that occur in elderly asthmatic patients. During an acute asthmatic attack older patients are likely to show less inspiratory fall in blood pressure and less tachycardia than younger patients with the same degree of bronchoconstriction and abnormalities in blood gas concentrations.2 They are also likely to present later for medical attention,2 perhaps partly because elderly people (whether they have asthma or not) have less subjective appreciation than the young of the same degree of bronchoconstriction.' These differences may result in underestimation of the severity of an attack by both patient and doctor and may in part account for the relative excess of deaths due to asthma in older people.4 They emphasise the need for objective measurement (peak expiratory flow, concentrations of blood gases) in elderly patients whatever the
1162
A PANDIT S KALRA A WOODCOCK Wythenshawe Hospital, Manchester M23 9LT I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 1. Chronic persistent asthma. BMJ 1990;301:651-3.
patients over a long time are aware that there is a group of patients who cannot be adequately controlled by inhalers and other drugs, including oral steroids. Some of these patients, if carefully chosen, will benefit from hyposensitisation. There are numerous reports of double blind, placebo controlled trials of the effects of hyposensitisation in asthmatic patients sensitive to house mite or animal allergens.`8 Depending on the protocol, all these papers showed appreciable improvement in forced expiratory volume in one second,38 delay of onset or reduction of symptoms on exposure to animals,47 or increase in the provocation dose required to produce a 20% drop in forced expiratory volume4-7; some authors reported that sensitivity to histamine was decreased,8 others noted that responses to histamine6 or methacholine4 were unchanged despite the other improvements. Many earlier trials have been discredited because they used non-standardised extracts and did not include placebo drugs. Now that the importance of placebo groups is fully recognised and purified biologically standardised extracts have become available, a more open minded attitude would perhaps be reasonableallowing for the fact that asthmatic patients must be carefully selected for immunotherapy and even more carefully monitored during treatment. As stated in Dr P John Rees's editorial international allergists would indeed be surprised to read the statement on hyposensitisation.9 But the care of patients whose symptoms could not otherwise be ameliorated would probably compensate for some of the loss of income. M A GANDERTON
Maidenhead, Berkshire SL6 7LY I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 1. Chronic persistent asthma. BMJ 1990;301:651-3. (29 September.) 2 British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 2. Acute severe asthma. BMJ 1990;301:797-800. (6 October.) 3 Bousquet J, Calvayrac P, Guerin B, et al. Immunotherapy with a standardised Dermatophagoides pteronyssinus extract. 1. In vivo and in vitro parameters after a short course of treatment. 7 Allergy Clin Immunol 1985;76:734-44. 4 Ohman JL, Steven MD, Findlay R, Leitermann KM. Immunotherapy in cat-induced asthma. Double-blind trial with evaluation of in vivo and in vitro responses. J7 Allergy Clin Immunol 1984;74:230-9. 5 Van Metre TE, Marsh DG, Adkinson NF, et al. Immunotherapy decreases skin sensitivity to cat extract. J Allergv Clin Immunol
1989;83:888-99. 6 Taylor WW, Ohman JL Jr, Lowell FC. Immunotherapy in cat-induced asthma: double-blind trial with evaluation of bronchial responses to cat allergen and histamine. J Allergy
Clin Immunol 1978;61:283-7. 7 Sundin B, Lilla G, Craff-Lonnevig V, et al. Immunotherapy with partially purified and standardized animal dander extracts. 1. Clinical results from a double-blind study on patients with animal dander asthma. J Allergy Clin Immunol 1986;77:478-87. 8 Lilja G, Sundin B, Graff-Lonnevig V, et al. Imniunotherapy with cat- and dog-dander extracts. 4. Effects of 2 years of treatment. J Allergy Clin Immunol 1989;83:37-44. 9 Rees PJ. Guidelines for the management of asthma in adults.
BMJf 1990;301:771-2.
(29 September.) 2 Hay IFC, Higenbotham [Va. Has the management of asthma improved? Lancet 1987;ii:609-1 1.
Trauma in pregnancy
SIR,-The British Thoracic Society and others have set out their advice for managing asthma clearly, concisely, and logically in simple language, and I hope that the articles will be widely read and the advice heeded.'2 Though asthma has become more common and more severe in recent years, it has unfortunately become less newsworthy. The statement that hyposensitisation (immunotherapy) is not indicated in the management of chronic persistent asthma' is, however, still open to question. Doctors dealing with many asthma
SIR,-Dr Pamela Nash's and Mr Peter Driscoll's informative paper on trauma in pregnancy' contains a potentially misleading statement regarding the effects of backward pressure of the uterus when a pregnant woman lies in the supine position. Indeed, pressure on the vena cava reduces venous return to the heart, the extent depending on the capacity of the azygos system to provide an alternative route, thus reducing cardiac output. Arterial blood pressure is not necessarily reduced, however, as compensatory changes may increase peripheral vascular resistance, thus influencing an important factor in the equation: mean arterial
BMJ
VOLUME
301
17
NOVEMBER
1990
AUTHOR'S REPLY,-I note Dr Austin's concern that no pelvicaliceal dilatation will be detected by ultrasonography in infected kidneys that are acutely obstructed, especially those in diabetic patients with acute papillary necrosis, and agree that this is theoretically possible. Nevertheless, I have not encountered this over the past 12 years, during which I have used ultrasonography to examine many obstructed infected kidneys, including some in diabetic patients with ureters obstructed by sloughed papillae.. Dr Austin suggests that urography is a better method than ultrasonography and that obstruction of an infected kidney should be suspected if there is no filling of the pelvicaliceal system with contrast medium. Unfortunately, this urographic sign is not specific for obstruction. Severe acute infection alone may also prevent the pelvicaliceal system from filling with contrast medium at urography. 2 JA W WEBB St Bartholomew's Hospital, London EClA 7BE I Davidson AJ, 'I'alner LB. Urographic anid angiographic abnormalities in adult-onset acute bacterial nephritis. Radiology
1973;106:249-56. 2 Teplick JG, Teplick SK, Berinson H, Hasken ME. Urographic and angiographic changes in acute unilateral pyelonephritis. Clin Radiol 1979;30:59-66.
clinical assessment of the severity of an attack. In elderly patients the absence of physical signs classically viewed as markers of acute severe asthma should not be seen as reassuring. MARTIN J CONNOLLY
Seacroft Hospital, Leeds LS14 6UH I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for the management of asthma in adults. 2. Acute severe asthma. BMJ 1990;301:797-800. (6 October.) 2 Petheram IS, Jones DA, Collins JV. Assessment and management of acute asthma in the elderly: a comparison with younger asthmatics. Postgrad MedJ 1982;58:149-51. 3 Connolly MJ, Crowley JJ, Vestal RE. Reduced awareness of methacholine-provoked bronchoconstriction in elderly asthmatics and normals. Age Ageing 1990;19(suppl 2):19. 4 Robin ED. Risk benefit analysis in chest medicine. Death from bronchial asthma. Chest 1988;93:614-8.
SIR,-The guidelines issued by the British Thoracic Society and others relegate oral theophyllines to a subsidiary role and strongly advise monitoring of blood or salivary concentrations because of the narrow therapeutic ratio.' Oral theophyllines are, however, still widely used in general practice in Britain, roughly three and a half million prescriptions being written annually. As serum theophylline concentrations are measured in hospital laboratories we surveyed the biochemistry laboratories in the North West Regional Health Authority to ascertain the level of monitoring in general practice. For the three months February to April 1990 the total number of estimations of theophylline concentrations (number requested by general practitioners) in each district was as follows: Salford 262 (24), Wigan 194 (6), North Manchester 170 (2), Blackburn 156 (4), Blackpool 123 (9), Central Manchester 102 (0), Burnley 90 (2), Oldham 80 (8), Preston 67 (6), Rochdale 47 (2), South Manchester 46 (1), Trafford 41 (4), Tameside 37 (4), Bolton 29 (3). Thus, general practitioners requested less than 5% of the total number of assays. Assuming the population of North West region to be four million, there are about 87 500 prescriptions of theophylline written each quarter.2 Thus, serum theophylline concentrations are estimated in general practice less than once per 1173 prescriptions. Slow release oral theophylline will continue to have a role in managing asthma in the 1990s, although this role is likely to diminish with the introduction of long acting inhaled bronchodilator drugs. Much more monitoring of serum theophylline concentrations in general practice is necessary if oral theophyllines are to be used safely.
Guidelines for management of asthma SIR,-The guidelines for the management of asthma in adults published by the British Thoracic Society and others fail to recognise the potential differences in the presentation of acute severe asthma that occur in elderly asthmatic patients. During an acute asthmatic attack older patients are likely to show less inspiratory fall in blood pressure and less tachycardia than younger patients with the same degree of bronchoconstriction and abnormalities in blood gas concentrations.2 They are also likely to present later for medical attention,2 perhaps partly because elderly people (whether they have asthma or not) have less subjective appreciation than the young of the same degree of bronchoconstriction.' These differences may result in underestimation of the severity of an attack by both patient and doctor and may in part account for the relative excess of deaths due to asthma in older people.4 They emphasise the need for objective measurement (peak expiratory flow, concentrations of blood gases) in elderly patients whatever the
1162
A PANDIT S KALRA A WOODCOCK Wythenshawe Hospital, Manchester M23 9LT I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 1. Chronic persistent asthma. BMJ 1990;301:651-3.
patients over a long time are aware that there is a group of patients who cannot be adequately controlled by inhalers and other drugs, including oral steroids. Some of these patients, if carefully chosen, will benefit from hyposensitisation. There are numerous reports of double blind, placebo controlled trials of the effects of hyposensitisation in asthmatic patients sensitive to house mite or animal allergens.`8 Depending on the protocol, all these papers showed appreciable improvement in forced expiratory volume in one second,38 delay of onset or reduction of symptoms on exposure to animals,47 or increase in the provocation dose required to produce a 20% drop in forced expiratory volume4-7; some authors reported that sensitivity to histamine was decreased,8 others noted that responses to histamine6 or methacholine4 were unchanged despite the other improvements. Many earlier trials have been discredited because they used non-standardised extracts and did not include placebo drugs. Now that the importance of placebo groups is fully recognised and purified biologically standardised extracts have become available, a more open minded attitude would perhaps be reasonableallowing for the fact that asthmatic patients must be carefully selected for immunotherapy and even more carefully monitored during treatment. As stated in Dr P John Rees's editorial international allergists would indeed be surprised to read the statement on hyposensitisation.9 But the care of patients whose symptoms could not otherwise be ameliorated would probably compensate for some of the loss of income. M A GANDERTON
Maidenhead, Berkshire SL6 7LY I British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 1. Chronic persistent asthma. BMJ 1990;301:651-3. (29 September.) 2 British Thoracic Society, Research Unit of the Royal College of Physicians of London, King's Fund Centre, National Asthma Campaign. Guidelines for management of asthma in adults. 2. Acute severe asthma. BMJ 1990;301:797-800. (6 October.) 3 Bousquet J, Calvayrac P, Guerin B, et al. Immunotherapy with a standardised Dermatophagoides pteronyssinus extract. 1. In vivo and in vitro parameters after a short course of treatment. 7 Allergy Clin Immunol 1985;76:734-44. 4 Ohman JL, Steven MD, Findlay R, Leitermann KM. Immunotherapy in cat-induced asthma. Double-blind trial with evaluation of in vivo and in vitro responses. J7 Allergy Clin Immunol 1984;74:230-9. 5 Van Metre TE, Marsh DG, Adkinson NF, et al. Immunotherapy decreases skin sensitivity to cat extract. J Allergv Clin Immunol
1989;83:888-99. 6 Taylor WW, Ohman JL Jr, Lowell FC. Immunotherapy in cat-induced asthma: double-blind trial with evaluation of bronchial responses to cat allergen and histamine. J Allergy
Clin Immunol 1978;61:283-7. 7 Sundin B, Lilla G, Craff-Lonnevig V, et al. Immunotherapy with partially purified and standardized animal dander extracts. 1. Clinical results from a double-blind study on patients with animal dander asthma. J Allergy Clin Immunol 1986;77:478-87. 8 Lilja G, Sundin B, Graff-Lonnevig V, et al. Imniunotherapy with cat- and dog-dander extracts. 4. Effects of 2 years of treatment. J Allergy Clin Immunol 1989;83:37-44. 9 Rees PJ. Guidelines for the management of asthma in adults.
BMJf 1990;301:771-2.
(29 September.) 2 Hay IFC, Higenbotham [Va. Has the management of asthma improved? Lancet 1987;ii:609-1 1.
Trauma in pregnancy
SIR,-The British Thoracic Society and others have set out their advice for managing asthma clearly, concisely, and logically in simple language, and I hope that the articles will be widely read and the advice heeded.'2 Though asthma has become more common and more severe in recent years, it has unfortunately become less newsworthy. The statement that hyposensitisation (immunotherapy) is not indicated in the management of chronic persistent asthma' is, however, still open to question. Doctors dealing with many asthma
SIR,-Dr Pamela Nash's and Mr Peter Driscoll's informative paper on trauma in pregnancy' contains a potentially misleading statement regarding the effects of backward pressure of the uterus when a pregnant woman lies in the supine position. Indeed, pressure on the vena cava reduces venous return to the heart, the extent depending on the capacity of the azygos system to provide an alternative route, thus reducing cardiac output. Arterial blood pressure is not necessarily reduced, however, as compensatory changes may increase peripheral vascular resistance, thus influencing an important factor in the equation: mean arterial
BMJ
VOLUME
301
17
NOVEMBER
1990
