Correspondence References 1. BECKJ. Virginia Apgar, in memoriam in Clinical Perinarology,
2nd edn. ALADJEMS, BROWNA, SUREAU C, eds. St. Louis: C.V. Mosby, 1980: 19-29. A, MARTINRJ, MILLERMJ. IdentiJication and 2. FANAKOFF munugemen1 vf high risk problems in neonate in murernal-fetal
989
medicine. 2nd edn. CREASY RK, RESNIKR, eds. London: W.B. Saunders, 1989: I 150-3. 3. PRITCHARD JA, MCDONALD PC, GANTNF, eds. The newborn infant. In: Williams obstetrics, 17th edn. Appleton-Century-Crafts. Norwalk, Ct., 1985: 379-88.
Low cardiac output and enoximone Dr White’s account of the management of low cardiac output syndrome after cardiac surgery with enoximone (Anaesthesia 1990; 45: 386-89) intrigued me. The residual aortic regurgitation after mitral valve replacement and coronary artery bypass grafting was presumably sufficiently serious to contraindicate the use of intra-aortic balloon counterpulsation and yet so trivial as not to justify replacement. Secondly, I was astounded to see the use of adrenaline at an infusion rate of 2.5 (pg/kg)/minute. This seems to be approaching the dose range for a single injection in the treatment of anaphylaxis, and well beyond the maximum useful inotropic dose quoted as 0.2 (pg/kg)/minute.’ The systemic vascular resistance (SVR) was calculated and I presume not indexed, but no mention was made of its inaccuracy due to the presence of (important) aortic regurgitation. Quite clearly the run-off after the left ventricle had ejected its stroke volume would be forwards into the sytemic arterial tree and backwards through the aortic orifice into the left ventricle. Thus the mean arterial pressure would be spuriously low for the purpose of calculating SVR. The merit of having a low SVR in the presence of aortic regurgitation is obvious but disadvantageous in some ways for effective coronary perfusion. How much enoximone contributed to the increase in cardiac index and decrease in calculated SVR when measured after 22 hours seems a matter of conjecture. The happy outcome for the patient in this anecdotal report might even be entitled ‘successful management of the circulation using metaraminol’! Southampton General Hospital, Southampton, SO9 E X Y
A reply
We welcome the opportunity to reply to Dr Manners‘ letter. Intra-aortic balloon counterpulsation was contraindicated in this patient because of the tachyarrhythmia rather than the aortic regurgitation, which was considered to be of minor significance. Triggering of the intra-aortic balloon pump from the ECG signal produces inconsistent pump responses in tachyarrythmias and makes it ineffective.’ The systemic vascular resistance figures we quoted were not indexed. We considered that the reduction in SVR with enoximone was much greater than could be explained by the degree of aortic regurgitation alone. Flow improved considerably after enoximone but sufficient driving pressure must be maintained to perfuse vital organs, and a balance between pressure and flow must be struck. Metaraminol has been used regularly as the primary vasopressor at Papworth for over 20 years. Like many drugs, it is the way in which they are used that is important. We would also be astounded by the use of adrenaline at 2.5 (pg/kg)/minute and must thank him for pointing out the obvious typographical error! The adrenaline infusion should read 0.25 (pg/kg)/minute. Case reports are by their very nature anecdotal; however, we considered the case worth a report. This was our first experience with a new class of inotrope in 1987 and we learned several lessons. Papworth Hospital, Cambridgeshire CB3 8 R E
J.W. MANNERS
D.A. WHI-re R.D. LATIMER A. ODURO
Rejerence Reference I. HENSLEY FA, MARTINDE. The practice of’cardiuc anesrhesia. Boston: Little, Brown, 1990.
1. MACCIOLIG A , LIJCAS WJ, NORFLEET EA. The intra-aortic balloon pump: A review. Journal ~ fCardiothoracic ’ An~s/hericr 1988; 2: 365-73.
Occupational exposure to HIV and zidovudine chemoprophylaxis Comprehension of risk of HIV infection through normal working exposure to the virus in theatre and intensive care comes largely from material intended for the lay public. Anaesthetists, however, work in an environment where they are regularly exposed to blood and body fluids and where needlestick injury is not uncommon. The risk depends on the prevalence of HIV in the population, probability of transmission per accident and the number of accidents in a given time. There are 3021 recorded cases of HIV in the United Kingdom; estimates for the number of unidentified carriers ranges from 25-62 for every known AIDS case. Large scale studies of prevalence are difficult, but a recent study of over I15000 pregnant women, tested anonymously by use of Guthrie cards for neonatal screening, has shown a figure as high as 0.49 per thousand in inner London, in a group which is not essentially high risk.’
The incidence of needlestick injury and risk of subsequent transmission is unknown. Combined data from 10 prospective studies shows that the risk of HIV-I transmission associated with a single p a r e n t e d exposure is 0.37% (slightly less than 1 infection for every 250 exposures).‘ This is probably an underestimate because inoculation with small numbers of viruses, as in needlestick injury, can result in delayed seroconversion and a delay of 42 months is recorded.3 Any one exposure would seem not to pose an unacceptable threat, but the cumulative risk of many incidents may be unacceptably high.,Jones3 has suggested that the chance of infection for an anaesthetist over a 40year working life is as high as 1 in 25. The risk of progression to AIDS is high once infection has occurred. The Association of Anaesthetists of Great Britain and Ireland has published guidelines for the prevention of
2nd edn. ALADJEMS, BROWNA, SUREAU C, eds. St. Louis: C.V. Mosby, 1980: 19-29. A, MARTINRJ, MILLERMJ. IdentiJication and 2. FANAKOFF munugemen1 vf high risk problems in neonate in murernal-fetal
989
medicine. 2nd edn. CREASY RK, RESNIKR, eds. London: W.B. Saunders, 1989: I 150-3. 3. PRITCHARD JA, MCDONALD PC, GANTNF, eds. The newborn infant. In: Williams obstetrics, 17th edn. Appleton-Century-Crafts. Norwalk, Ct., 1985: 379-88.
Low cardiac output and enoximone Dr White’s account of the management of low cardiac output syndrome after cardiac surgery with enoximone (Anaesthesia 1990; 45: 386-89) intrigued me. The residual aortic regurgitation after mitral valve replacement and coronary artery bypass grafting was presumably sufficiently serious to contraindicate the use of intra-aortic balloon counterpulsation and yet so trivial as not to justify replacement. Secondly, I was astounded to see the use of adrenaline at an infusion rate of 2.5 (pg/kg)/minute. This seems to be approaching the dose range for a single injection in the treatment of anaphylaxis, and well beyond the maximum useful inotropic dose quoted as 0.2 (pg/kg)/minute.’ The systemic vascular resistance (SVR) was calculated and I presume not indexed, but no mention was made of its inaccuracy due to the presence of (important) aortic regurgitation. Quite clearly the run-off after the left ventricle had ejected its stroke volume would be forwards into the sytemic arterial tree and backwards through the aortic orifice into the left ventricle. Thus the mean arterial pressure would be spuriously low for the purpose of calculating SVR. The merit of having a low SVR in the presence of aortic regurgitation is obvious but disadvantageous in some ways for effective coronary perfusion. How much enoximone contributed to the increase in cardiac index and decrease in calculated SVR when measured after 22 hours seems a matter of conjecture. The happy outcome for the patient in this anecdotal report might even be entitled ‘successful management of the circulation using metaraminol’! Southampton General Hospital, Southampton, SO9 E X Y
A reply
We welcome the opportunity to reply to Dr Manners‘ letter. Intra-aortic balloon counterpulsation was contraindicated in this patient because of the tachyarrhythmia rather than the aortic regurgitation, which was considered to be of minor significance. Triggering of the intra-aortic balloon pump from the ECG signal produces inconsistent pump responses in tachyarrythmias and makes it ineffective.’ The systemic vascular resistance figures we quoted were not indexed. We considered that the reduction in SVR with enoximone was much greater than could be explained by the degree of aortic regurgitation alone. Flow improved considerably after enoximone but sufficient driving pressure must be maintained to perfuse vital organs, and a balance between pressure and flow must be struck. Metaraminol has been used regularly as the primary vasopressor at Papworth for over 20 years. Like many drugs, it is the way in which they are used that is important. We would also be astounded by the use of adrenaline at 2.5 (pg/kg)/minute and must thank him for pointing out the obvious typographical error! The adrenaline infusion should read 0.25 (pg/kg)/minute. Case reports are by their very nature anecdotal; however, we considered the case worth a report. This was our first experience with a new class of inotrope in 1987 and we learned several lessons. Papworth Hospital, Cambridgeshire CB3 8 R E
J.W. MANNERS
D.A. WHI-re R.D. LATIMER A. ODURO
Rejerence Reference I. HENSLEY FA, MARTINDE. The practice of’cardiuc anesrhesia. Boston: Little, Brown, 1990.
1. MACCIOLIG A , LIJCAS WJ, NORFLEET EA. The intra-aortic balloon pump: A review. Journal ~ fCardiothoracic ’ An~s/hericr 1988; 2: 365-73.
Occupational exposure to HIV and zidovudine chemoprophylaxis Comprehension of risk of HIV infection through normal working exposure to the virus in theatre and intensive care comes largely from material intended for the lay public. Anaesthetists, however, work in an environment where they are regularly exposed to blood and body fluids and where needlestick injury is not uncommon. The risk depends on the prevalence of HIV in the population, probability of transmission per accident and the number of accidents in a given time. There are 3021 recorded cases of HIV in the United Kingdom; estimates for the number of unidentified carriers ranges from 25-62 for every known AIDS case. Large scale studies of prevalence are difficult, but a recent study of over I15000 pregnant women, tested anonymously by use of Guthrie cards for neonatal screening, has shown a figure as high as 0.49 per thousand in inner London, in a group which is not essentially high risk.’
The incidence of needlestick injury and risk of subsequent transmission is unknown. Combined data from 10 prospective studies shows that the risk of HIV-I transmission associated with a single p a r e n t e d exposure is 0.37% (slightly less than 1 infection for every 250 exposures).‘ This is probably an underestimate because inoculation with small numbers of viruses, as in needlestick injury, can result in delayed seroconversion and a delay of 42 months is recorded.3 Any one exposure would seem not to pose an unacceptable threat, but the cumulative risk of many incidents may be unacceptably high.,Jones3 has suggested that the chance of infection for an anaesthetist over a 40year working life is as high as 1 in 25. The risk of progression to AIDS is high once infection has occurred. The Association of Anaesthetists of Great Britain and Ireland has published guidelines for the prevention of
![[Comparison of enoximone versus tobutamine in the treatment of low cardiac output after cardiac surgery].](/assets/img/hold.png)
