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PREVENTION OF AIRBORNE INFECTION
778 "
off-hand," and I have issued three separate invitations
PREVENTION OF AIRBORNE INFECTION SIR,-In your issue of March 6, Mr. Baker claims that
to another doctor to call at any time that is convenient
to discuss a particularly difficult problem. Once again I have had no reply. In spite of all this, I believe that the general practitioner is the most important member of the health service, and I most earnestly wish to see more cooperation between practitioner and hospital ; but I can assure Dr. Hardcastle that the organisation of such cooperation is weary uphill work. REGISTRAR
IN
TEACHING HOSPITAL.
CONTROLLED HYPOTENSION WITH ARFONAD use of ’ Arfonad ’ have We believe that any hypotensive technique should be used only when it is considered essential for the success of a particular operation. Our present experience with arfonad is, therefore, necessarily small ; we have used it in 21 aural fenestrations and 5 craniotomies. We would, however, like to record that our findings are almost identical with those already published in larger series.
SIR,-The recent reports of the
been very
interesting.
The anaesthetic
described1 for neurosurgical operations has been used in every case, and it is essential, if oozing is to be avoided even when arterial pressure is low, to ensure a perfect airway, spontaneous respiration, and correct posture. The tachycardia that may follow the injection of gallamine triethiodide should preclude this drug in any hypotensive operation. The standard drip chamber has been used with a pendulum2 and fine-adjustment regulator.3 This has allowed satisfactory control of dosage of an 0-1% solution. The ages of the patients in this series have ranged from fifteen to sixty-five years, and the average dosage has been at the rate of 23 mg. per minute.
’
BLOOD-UREA LEVELS OF WEST AFRICANS IN LONDON
technique recently
We have been particularly impressed by the control during the induction of hypotension with this drug. The " pressure floor," mentioned by Dr. Scurr and Dr. Wyman (Feb. 13), and the individual variation in dosage required have been confirmed. Difficulty has been experienced in lowering the pressure in 4 cases, but even with a systolic pressure of between 80 and 100 mm. Hg, bleeding has not been troublesome. It seems that the lowering of the pulse-pressure to between 10 and 15 mm. Hg is more important in stopping bleeding than an absolute reduction of blood-pressure. In 4 long cases it was found that, after about 100 minutes, it was suddenly necessary to double the drip-rate to maintain the previously established blood-pressure. This change did not appear to be related to any change in the anaesthetic or any operative procedure. Like others, we have found procaine amide of value in reducing tachycardia. We would also stress the importance of replacing any blood that may be lost ; if this is not done, difficulty will be experienced in restoring the blood-pressure to normal. Cessation of administration has been followed by an immediate rise in blood-pressure, but it has often taken over 30 minutes to return to normal. In the neurosurgical cases, the systolic pressure has been allowed to rise to 90 or 100 mm. Hg before replacement of the bone flap, so that the surgeon could stop any bleeding. The postoperative condition of the patients has been excellent ; there have been no cases of prolonged hypotension and no complications attributable to the anaesthetic. The results published so far suggest that arfonad is a valuable drug, provided it is used with care and
SIR,-The observation of Phillips and Kenneythat
plasma-urea level
the
ROBERT I. W. BALLANTINE IAN JACKSON TOM B. BOULTON. Ballantine, R. I. W., Jackson, I. Anœsthesia, 1954, 9, Morton, H. J. V. Ibid, 1953, 8, 112. Morton, H. J. V. Brit. med. J. 1953, i, 990.
low
in
small
a
sample
of West Africans
139 mg. per 100 ml. prompted us to compare a group of West African students in London with a series of English males of similar age-distribution. Twelve of the Africans were from the Gold Coast and the rest from Southern Nigeria ; the Europeans were as
was
as
University staff, students, The drawn
estimated
and technicians.
oxalated whole blood, freshly by venepuncture, by Conway’s method,2 using urease Dunning tablets as the enzyme preparation. All estimations were performed in duplicate ;a samples from both Africans and Europeans were run in each batch of determinations together with a standard urea solution. Wo were subsequently able to examine a small series of serum specimens from blood obtained by venepuncture from African technicians at the fniversity College, Ibadan, Nigeria, and sent by air to London in vacuum ampoules packed with ice. We urea was
on
indebted to Mr. J. P. Garlick for this material and for The data are certain information about the subjects. summarised in the accompanying table. are
*
The
Based
on
18 subjects.
value for the London Africans
mean
compared
with
English gives a value of t 2-19 for d.f. 37, which is just significant at 5-0%, so that there is some evidence that, even on a European diet, the African blood-urea level is slightly low. The African subjects had been in England for a period ranging from 11 days to 7 years (mean 21/4 years). Plotting the urea level against length of residence in England suggested no obvious relation between the two, but the sample is small and includes very few recently arrived subjects. The mean blood-urea level of the London Africans compared with that of the Ibadan Africans gives a highly significant -differem the
(t
=
=
were
5-38 d.f.
32, P
urea
<
on
When blank determinations evidence of prior decomposifound.
00001).
these to ammonia
performed
tion of
discrimination.
1. 2. 3.
continuous-flow aerosol of hexylresorcinol might be used instead of ventilation to control the numbers of airborne bacteria in operating-theatres and dressingstations, although he admits that no reports of its use for this purpose are available to justify his claims.’ We have recently completed analyses of an investigation of the use in clerical offices of hexylresorcinol vaporised from the thermal generators described by Mr. Baker. In this situation, no reduction was detect. able in the bacterial counts in the air with the vaporisers working normally ; and even when the vapour concentration was increased sixfold, and produced some throat irritation among the occupants of the room, the rate of kill of bacteria sprayed from the mouth was equivalent to no more than 6 air changes per hour. The results of these investigations will be published in full elsewhere. Medical Research Council Air O. M. LIDWELL Hygiene Laboratory. R. E. O. WILLIAMS. London, N.W.9. a
sera no
was
Our results tend to confirm Phillips and Kenney’s observation that the blood-urea level is low in Africans of intermediate economic status living on a native diet 4.
1. Phillips, P. G., Kenney, R. A. Lancet, 1952, ii, 1230. 2. Conway, E. J. Microdiffusion Analysis and Volumetric Error.
London, 1947.
off-hand," and I have issued three separate invitations
PREVENTION OF AIRBORNE INFECTION SIR,-In your issue of March 6, Mr. Baker claims that
to another doctor to call at any time that is convenient
to discuss a particularly difficult problem. Once again I have had no reply. In spite of all this, I believe that the general practitioner is the most important member of the health service, and I most earnestly wish to see more cooperation between practitioner and hospital ; but I can assure Dr. Hardcastle that the organisation of such cooperation is weary uphill work. REGISTRAR
IN
TEACHING HOSPITAL.
CONTROLLED HYPOTENSION WITH ARFONAD use of ’ Arfonad ’ have We believe that any hypotensive technique should be used only when it is considered essential for the success of a particular operation. Our present experience with arfonad is, therefore, necessarily small ; we have used it in 21 aural fenestrations and 5 craniotomies. We would, however, like to record that our findings are almost identical with those already published in larger series.
SIR,-The recent reports of the
been very
interesting.
The anaesthetic
described1 for neurosurgical operations has been used in every case, and it is essential, if oozing is to be avoided even when arterial pressure is low, to ensure a perfect airway, spontaneous respiration, and correct posture. The tachycardia that may follow the injection of gallamine triethiodide should preclude this drug in any hypotensive operation. The standard drip chamber has been used with a pendulum2 and fine-adjustment regulator.3 This has allowed satisfactory control of dosage of an 0-1% solution. The ages of the patients in this series have ranged from fifteen to sixty-five years, and the average dosage has been at the rate of 23 mg. per minute.
’
BLOOD-UREA LEVELS OF WEST AFRICANS IN LONDON
technique recently
We have been particularly impressed by the control during the induction of hypotension with this drug. The " pressure floor," mentioned by Dr. Scurr and Dr. Wyman (Feb. 13), and the individual variation in dosage required have been confirmed. Difficulty has been experienced in lowering the pressure in 4 cases, but even with a systolic pressure of between 80 and 100 mm. Hg, bleeding has not been troublesome. It seems that the lowering of the pulse-pressure to between 10 and 15 mm. Hg is more important in stopping bleeding than an absolute reduction of blood-pressure. In 4 long cases it was found that, after about 100 minutes, it was suddenly necessary to double the drip-rate to maintain the previously established blood-pressure. This change did not appear to be related to any change in the anaesthetic or any operative procedure. Like others, we have found procaine amide of value in reducing tachycardia. We would also stress the importance of replacing any blood that may be lost ; if this is not done, difficulty will be experienced in restoring the blood-pressure to normal. Cessation of administration has been followed by an immediate rise in blood-pressure, but it has often taken over 30 minutes to return to normal. In the neurosurgical cases, the systolic pressure has been allowed to rise to 90 or 100 mm. Hg before replacement of the bone flap, so that the surgeon could stop any bleeding. The postoperative condition of the patients has been excellent ; there have been no cases of prolonged hypotension and no complications attributable to the anaesthetic. The results published so far suggest that arfonad is a valuable drug, provided it is used with care and
SIR,-The observation of Phillips and Kenneythat
plasma-urea level
the
ROBERT I. W. BALLANTINE IAN JACKSON TOM B. BOULTON. Ballantine, R. I. W., Jackson, I. Anœsthesia, 1954, 9, Morton, H. J. V. Ibid, 1953, 8, 112. Morton, H. J. V. Brit. med. J. 1953, i, 990.
low
in
small
a
sample
of West Africans
139 mg. per 100 ml. prompted us to compare a group of West African students in London with a series of English males of similar age-distribution. Twelve of the Africans were from the Gold Coast and the rest from Southern Nigeria ; the Europeans were as
was
as
University staff, students, The drawn
estimated
and technicians.
oxalated whole blood, freshly by venepuncture, by Conway’s method,2 using urease Dunning tablets as the enzyme preparation. All estimations were performed in duplicate ;a samples from both Africans and Europeans were run in each batch of determinations together with a standard urea solution. Wo were subsequently able to examine a small series of serum specimens from blood obtained by venepuncture from African technicians at the fniversity College, Ibadan, Nigeria, and sent by air to London in vacuum ampoules packed with ice. We urea was
on
indebted to Mr. J. P. Garlick for this material and for The data are certain information about the subjects. summarised in the accompanying table. are
*
The
Based
on
18 subjects.
value for the London Africans
mean
compared
with
English gives a value of t 2-19 for d.f. 37, which is just significant at 5-0%, so that there is some evidence that, even on a European diet, the African blood-urea level is slightly low. The African subjects had been in England for a period ranging from 11 days to 7 years (mean 21/4 years). Plotting the urea level against length of residence in England suggested no obvious relation between the two, but the sample is small and includes very few recently arrived subjects. The mean blood-urea level of the London Africans compared with that of the Ibadan Africans gives a highly significant -differem the
(t
=
=
were
5-38 d.f.
32, P
urea
<
on
When blank determinations evidence of prior decomposifound.
00001).
these to ammonia
performed
tion of
discrimination.
1. 2. 3.
continuous-flow aerosol of hexylresorcinol might be used instead of ventilation to control the numbers of airborne bacteria in operating-theatres and dressingstations, although he admits that no reports of its use for this purpose are available to justify his claims.’ We have recently completed analyses of an investigation of the use in clerical offices of hexylresorcinol vaporised from the thermal generators described by Mr. Baker. In this situation, no reduction was detect. able in the bacterial counts in the air with the vaporisers working normally ; and even when the vapour concentration was increased sixfold, and produced some throat irritation among the occupants of the room, the rate of kill of bacteria sprayed from the mouth was equivalent to no more than 6 air changes per hour. The results of these investigations will be published in full elsewhere. Medical Research Council Air O. M. LIDWELL Hygiene Laboratory. R. E. O. WILLIAMS. London, N.W.9. a
sera no
was
Our results tend to confirm Phillips and Kenney’s observation that the blood-urea level is low in Africans of intermediate economic status living on a native diet 4.
1. Phillips, P. G., Kenney, R. A. Lancet, 1952, ii, 1230. 2. Conway, E. J. Microdiffusion Analysis and Volumetric Error.
London, 1947.