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PROTECTIVE ACTION OF HYPERBARIC OXYGEN IN MICE WITH PNEUMOCOCCAL SEPTICÆMIA
579
PROTECTIVE ACTION OF HYPERBARIC OXYGEN IN MICE WITH PNEUMOCOCCAL SEPTICÆMIA
TABLE II-PNEUMOCOCCAL VIRULENCE AFTER INTRAPERITONEAL
INJECTION
AT THREE DIFFERENT TIMES DURING EXPERIMENT
R. M. Ross M.B. Glasg. REGISTRAR, UNIVERSITY DEPARTMENT
OF SURGERY
T. A. MCALLISTER M.B. Glasg. REGISTRAR, UNIVERSITY DEPARTMENT OF BACTERIOLOGY WESTERN
EXPOSURE
to
INFIRMARY, GLASGOW
oxygen at 2
or
3
atmospheres markedly
inhibits the growth of some aerobic and obligatory anaerobic bacteria and changes their colonial morphology and Towers 1963, McAllister et al. 1963, al. 1964). In many animals long-continued hyperbaric oxygen also produces toxic effects (Bean 1945), though it has been used with success in the treatment of anaerobic infections (de Almeida and Pacheco 1941, Brummelkamp et al. 1961, 1963, Klopper et al. 1962, Wallyn and Gumbiner 1963). Since an oxygen tension of 2. atmospheres is readily attainable in the arterial blood (Ledingham 1963) we tried to produce significant bacterial inhibition in mice with pneumococcal septicxmia without incurring the risk of serious toxic side-effects. The survival of oxygen-treated and control groups was compared in a variety of experimental situations.
(Hopkinson Gottlieb
et
.
Materials and Methods Porton albino mice of both sexes, weighing from 25 to 40 g., were used, but in any one experiment both the oxygen-treated and control groups were within the same 5 g. range (table r). Each mouse was challenged intraperitoneally with 0-5 ml. of a suspension of pneumococci in a sterile 1 : 2 peptone water saline mixture. The peptone water comprised peptone (British Drug Houses Ltd.) 2% in water+0-5% sodium chloride. A single strain of Streptococcus pneumonice type III (type III pneumococcus) was used throughout the experiments. Its in-vitro sensitivity to hyperbaric oxygen was tested as previously described (McAllister et al. 1963, 1964). Two separate freeze-dried preparations of this strain (labelled A and B in table i) were subcultured on horse-blood-agar at 37°C and were used to prepare the inocula. After several plate-to-mouse-toplate passages (labelled numerically in table r) to increase their virulence, the pneumococci were grown for 8 hours at 37°C in meat-extract broth (500 g. ox heart per litre -1 % peptone+ 0-5% sodium chloride+0-05% para-aminobenzoic acid) enriched with 10% human serum. After centrifugation at 3000 r.p.m. for 20 minutes the bacteria were resuspended in
peptone/saline, and cell-counts were estimated by comparison with Brown’s opacity standards (Burroughs Wellcome). The required dosage was then obtained by further dilution in peptone/saline, and viable counts were carried out by the method of Miles and Misra (1938) using horse-blood-agar plates and pipettes calibrated to deliver 0-02 ml. per drop. The L.D’50S for pneumococci A4, A6, and B2 (table n) were calculated by the method of Reed and Muench (1938), using in each case tenfold dilutions of the pneumococci and six groups of five mice. The groups of mice were placed in a pressure tank (capacity 9-5 c.ft.), and, after preliminary flushing with oxygen for 10 minutes, the pressure was increased over a 12-minute period to 2 atmospheres (1520 mm. Hg). Throughout the exposure to hyperbaric oxygen a continuous flow through the tank was maintained to keep the environment at as near 100% oxygen as possible. The tank was decompressed over a 12-minute period. In experiments 1, 2, 3, and 5 two exposures were employed, separated by an interval of normal atmospheric conditions. In each experiment the initial exposure was made about 45 minutes after intraperitoneal challenge. The control groups of mice were kept under normal atmospheric conditions in the same room (temperature 20°C) as the pressure tank.
Results The results are summarised in tables i-iv. Table I shows the overall results for eight experiments, and table iv illustrates in detail the type of data recorded during each. The effects of hyperbaric oxygen can be gauged in three ways:
(1) By comparing the time-to-90% mortality in each group (table i). (2) By the number of deaths in the oxygen-treated group when 90% (18/20) of controls are dead (table i). 90% mortality was chosen as a convenient endpoint, because’ it embraces the majority of the mouse population and avoids distortion of the results by a single highly resistant mouse. (3) By comparing the mean survival-times of the oxygentreated and control groups (table ill). The third method is a less sensitive index of the protective effect of hyperbaric oxygen than the other two; nevertheless there is a highly significant difference between the means in experiments 1 and 8.
TABLE I-SURVIVAL OF OXYGEN-TREATED AND CONTROL MICE WITH PNEUMOCOCCAL SEPTICAEMIA
*
A and B
are
separate subcultures of the
same
type-III
pneumococcus.
Numbers refer
to
number of mouse-passages before experiment.
580 TABLE III-MEAN SURVIVAL-TIMES
In experiments 4, 6, and 7 the course of the septicaemia was altered (table i). The beneficial effects, however, are transient and are not reflected by a significant difference in the mean survival-times. In experiments 2, 3, and 5 there is no evidence of any prolongation of survival in the
oxygen-treated
oxygen at 2
group.
Four further results
were
obtained:
striking inhibition of growth of pneumococci horse-blood-agar and exposed at 37°C to 2 atmospheres of oxygen either continuously for 18 hours or intermittently for three periods of 2 hours with 2-hour intervals (1) There subcultured
infected host. In experiments 1 and 8 this is seen as an increase in the time-to-90% mortality of the oxygentreated group as against the mortality in controls (table i) and also as an increase in the mean survival-time of the oxygen-treated group to an extent which is statistically highly significant (table ill). Thus, in these two experiments a protective effect was obtained without apparent signs of oxygen toxicity. In experiments 4, 6, and 7 the beneficial effects of hyperbaric oxygen were reflected in the prolongation of timeto-90% mortality in the oxygen-treated group (table i) but the corresponding mean survival-times do not differ significantly (table ill). No protective effect was noted in experiments 2, 3, and 5. Throughout the series no adverse effects of oxygen were apparent. The pneumococcus was chosen as the test organism, because, although classified as an aerobe and facultative anaerobe, it shares many properties with the strict anaerobes. Most of its energy is derived from anaerobic glycolysis, and its lack of catalase and consequent susceptibility to hydrogen peroxide renders it very sensitive to small changes in oxidation-reduction potential (Topley and Wilson 1964, Dubos 1958). In our preliminary experiments its growth was strongly inhibited in vitro by
was on
between. (2) In a pilot study on twelve mice (30-35 g.) large numbers of viable pneumococci were recovered from the heart-blood 15 minutes after intraperitoneal challenge with 500 x 106 ’
organisms. (3) Pneumococci isolated from the heart-blood of mice exposed to hyperbaric oxygen after challenge grew normally when subcultured on horse-blood-agar and were encapsulated. (4) Three groups of 20 mice (30-35 g.) were observed for 6 weeks after (a) intraperitoneal injection of 0-5 ml. peptone/ saline; (b) intraperitoneal injection of 0-5 ml. peptone/saline+ 5 hours continuous hyperbaric oxygen at 2 atmospheres; (c) 5 hours continuous oxygen at 2 atmospheres. No ill-effects were noted.
Discussion
The results show that hyperbaric oxygen can alter the of an aerobic septicxmia, and can, by its antibacterial activity, significantly prolong the survival of the
course
TABLE IV-MORTALITY OF OXYGEN-TREATED AND CONTROL MICE THROUGHOUT A PNEUMOCOCCAL SEPTICaeMIA
(EXPERIMENT 8)
atmospheres.
Pneumococcal virulence is associated with the degree of capsulation, and there is no evidence that the production of soluble toxins plays any part in its pathogenicity (Topley and Wilson 1964). When injected intraperitoneally in mice, pneumococci rapidly enter the bloodstream, and death results from invasion and multiplication in the tissues. Hence the adoption of a mouse-pneumococcal system permitted exposure of live, multiplying, virulent aerobic bacteria to 2 atmospheres of oxygen in the arterial blood. Mice are convenient hosts, because, like humans,
they
are
highly susceptible
to
oxygen
poisoning. Hyper-
baric oxygen can therefore only be beneficial when it can exert its toxicity selectively to produce bacteriostasis (McAllister et al. 1963) rather than tissue damage. In the chosen system the severity of the infection progressively increases the mortality-rate with eventual death of all controls. In any one experiment their percentage mortality is a function of time as well as of the size of the inoculum; for example, in experiment 8 the same dose, namely 125 x 106 pneumococci, is the L.D.5o at 91/2 hours, the L.D.76 at 11 hours, the L.D.90 at 20 hours, and the L.D.loo at 29 hours (table iv). In our experiments all the oxygentreated mice also died eventually and protective action was apparent not as an overall difference inmortality between the control and oxygen-treated groups but as a prolongation of " time-to-death " of the oxygen-treated group. This is illustrated in experiment 8 (table iv) where 50% mortality is reached at 15 hours (51/2 hours’ prolongation), 75%mortality at about 28 hours (17 hours’ prolongation), 90% mortality at 29 hours (9 hours’ prolongation) and 100% mortality at 32 hours (3 hours’ prolongation). The failure of hyperbaric oxygen to influence the overall mortality is possibly due to its bacteriostatic rather than bactericidal action. Several broad conclusions can be drawn from the results: When the time-to-death of the majority of the controls very short (e.g., in experiment 3) the overwhelming nature of the infection precluded effective protection either by the hyperbaric oxygen or the natural defences of the mice. On the other hand, (2) when the course of the control infection was prolonged
(1)
was
581
The local application of hyperbaric oxygen (see figure) could prove beneficial in infected superficial wounds and burns, infected ischaemic skin-flaps, and in acute infective gangrene.
Summary
Locally applied hyperbaric oxygen. Patient is in air at 2 atmospheres. The foot is encased in filled polyethylene bag.
an
oxygen-
example, in experiment 2, any bacteriostasis producec by hyperbaric oxygen would have been nullified by furthel as, for
bacterial multiplication, and would therefore not have been reflected by the relatively insensitive indicator-namely, death of the mouse. In both these circumstances-the failure oi hyperbaric oxygen to control either the overwhelming or the more chronic infection-an analogy with antibiotic therapy can be made. (3) The best protective effects are seen between these two extremes (e.g., in experiments 1 and 8) when death of the majority of the controls occurred 10 to 20 hours after challenge.
The survival of mice with pneumococcal septicaemia can be prolonged by exposure to oxygen at 2 atmospheres (1520 mm. Hg) shortly after intraperitoneal challenge. In 2 out of 8 experiments the difference between treated and control groups was highly significant; in 3 experiments the beneficial effects were transient; and in the remainder there was no evidence of protection. The variation in results may be analogous with antibiotic therapy.
Infections by other sensitive aerobic bacteria-e.g., Staph. aureus, Esch. coli, Ps. pyocyanea, and Strep. viridans -might be amenable to treatment with hyperbaric oxygen, either alone or combined with conventional antibiotics, provided that they are in situations where antibacterial oxygen tensions are readily attainable, such as in the arterial blood and on the surface of the body. We wish to thank Sir Charles Illingworth and Prof. R. G. White for their support and encouragement; Dr. Iwo Lominski for his guidance throughout the experiments; Dr. R. A. Robb, of the department of mathematics, Glasgow University, for the statistical analysis; Mr. George A. Thomson for the supply and care of the mice; and Mr. G. R. Kerr for the photography.
REFERENCES with the bacteriostatic antibiotics, the J. W. (1945) Physiol. Rev. 25, 24-40. Bean, the is to longer infecting organism exposed hyperbaric Brummelkamp, W. H., Hoogendijk, J., Boerema, I. (1961) Surgery, 49, 299. Boerema, I., Hogendyk, L. (1963) Lancet, i, 235. oxygen the greater the chances of therapeutic success de Almeida, A. O., Pacheco, G. (1941) Rev. bras. Biol. 1, 1. seem likely to be. Exposure is limited, however, by the Dubos, R. J. (1958) Bacterial and Mycotic Infections of Man. London. S. F., Rose, N. R., Maurizi, J., Lanphier, E. H. (1964) Lancet, i, danger of oxygen toxicity, and in our experiments times Gottlieb, 382. were chosen which produce no overt toxic effects in mice Hopkinson, W. I., Towers, A. G. (1963) ibid. ii, 1361. Klopper, P. J., Brummelkamp, W. H., Hoogendijk, J. L. (1962) Pr. méd. or man. Pneumococci very rapidly invade the blood41, 1874. Lambertsen, C. J., Ewing, J. H., Kough, R. H., Gould, R., Stroud, M. W. stream and accordingly oxygen therapy was begun as soon (1955) J. appl. Physiol. 8, 255. as possible after injection, since once the tissues have been Ledingham, I. McA. (1963) Personal communication. T. A., Stark, J. M., Norman, J. N., Ross, R. M. (1963) Lancet, invaded to any degree the chances of achieving significant McAllister, ii, 1040. (1964) ibid. i, 499. protection are greatly reduced. Miles, A. A., Misra, S. S. (1938) J. Hyg., Camb. 38, 732. The therapeutic response depends on the interaction of Reed, L. J., Muench, H. (1938) Amer. J. Hyg. 27, 493. Topley and Wilson (1964) Principles of Bacteriology and Immunity (edited a number of variables, such as inoculum size, pneumoby G. S. Wilson and A. A. Miles); vol. I. London. Wallyn, R. J., Gumbiner, S. (1963) Proceedings of 1st International Congress coccal virulence, mouse-weight, and the timing and duraon Clinical Application of Hyperbaric Oxygen. Amsterdam. tion of oxygen treatment (table I). The size of the inoculum could only be roughly gauged before injection, and pneumococcal virulence varied with the age of the subculture and the number of successive mouse-passages HYPERBARIC OXYGEN IN THE before each experiment (table 11). Accordingly, on account. TREATMENT OF THE POSTOPERATIVE of the small number of observations and the lack of LOW-CARDIAC-OUTPUT SYNDROME precise control of some of the governing factors their individual roles in the differing degrees of protection M. H. YACOUB could not be accurately assessed. M.B. Cairo, F.R.C.S., F.R.C.S.E., F.R.C.S.G. The protective action of hyperbaric oxygen in infected SENIOR SURGICAL REGISTRAR* mice is further evidence that it may be of value in the G. L. ZEITLIN treatment of some aerobic infections in man, either as an M.B. Cantab., F.F.A. R.C.S. adjunct to conventional antibiotics or alone, where the SENIOR ANÆSTHETIC REGISTRAR causal organisms are antibiotic resistant or inaccessible. LONDON CHEST HOSPITAL, LONDON, E.2 The causal microorganisms must be sensitive to hyperbaric IT has been our experience that patients who develop oxygen-e.g., Staphylococcus aureus, Escherichia coli, Pseudomonas pyocyanea, and Streptococcus viridans-and the low-cardiac-output syndrome in association with pulmonary hypertension after cardiac surgery seldom must be sited where an oxygen tension of 2 atmospheres recover despite vigorous treatment. We report here the is readily attainable. The latter proviso includes arterial of a case patient who was successfully treated by means blood (Lambertsen 1955, Ledingham 1963), pulmonary of hyperbaric oxygen therapy. alveoli, and, in addition, any area of the body surface if oxygen is applied to it locally while the patient is in air at Case-report
In
common
—
—
2
atmospheres (see figure).
Hyperbaric
oxygen has been used with some success in anaerobic infections, but may also be of value in aerobic septicxmias or in combination with antibiotics in subacute bacterial endocarditis where it could shorten treatment.
—
—
—
A 50-year-old man was admitted to the London Chest Hospital on Oct. 23, 1964. He had a history of productive cough, recurrent hxmoptysis, and dyspncea on exertion for 21 years. He had been discharged from the Army 20 years *Present address:
Brompton Hospital, London, S.W.3.
PROTECTIVE ACTION OF HYPERBARIC OXYGEN IN MICE WITH PNEUMOCOCCAL SEPTICÆMIA
TABLE II-PNEUMOCOCCAL VIRULENCE AFTER INTRAPERITONEAL
INJECTION
AT THREE DIFFERENT TIMES DURING EXPERIMENT
R. M. Ross M.B. Glasg. REGISTRAR, UNIVERSITY DEPARTMENT
OF SURGERY
T. A. MCALLISTER M.B. Glasg. REGISTRAR, UNIVERSITY DEPARTMENT OF BACTERIOLOGY WESTERN
EXPOSURE
to
INFIRMARY, GLASGOW
oxygen at 2
or
3
atmospheres markedly
inhibits the growth of some aerobic and obligatory anaerobic bacteria and changes their colonial morphology and Towers 1963, McAllister et al. 1963, al. 1964). In many animals long-continued hyperbaric oxygen also produces toxic effects (Bean 1945), though it has been used with success in the treatment of anaerobic infections (de Almeida and Pacheco 1941, Brummelkamp et al. 1961, 1963, Klopper et al. 1962, Wallyn and Gumbiner 1963). Since an oxygen tension of 2. atmospheres is readily attainable in the arterial blood (Ledingham 1963) we tried to produce significant bacterial inhibition in mice with pneumococcal septicxmia without incurring the risk of serious toxic side-effects. The survival of oxygen-treated and control groups was compared in a variety of experimental situations.
(Hopkinson Gottlieb
et
.
Materials and Methods Porton albino mice of both sexes, weighing from 25 to 40 g., were used, but in any one experiment both the oxygen-treated and control groups were within the same 5 g. range (table r). Each mouse was challenged intraperitoneally with 0-5 ml. of a suspension of pneumococci in a sterile 1 : 2 peptone water saline mixture. The peptone water comprised peptone (British Drug Houses Ltd.) 2% in water+0-5% sodium chloride. A single strain of Streptococcus pneumonice type III (type III pneumococcus) was used throughout the experiments. Its in-vitro sensitivity to hyperbaric oxygen was tested as previously described (McAllister et al. 1963, 1964). Two separate freeze-dried preparations of this strain (labelled A and B in table i) were subcultured on horse-blood-agar at 37°C and were used to prepare the inocula. After several plate-to-mouse-toplate passages (labelled numerically in table r) to increase their virulence, the pneumococci were grown for 8 hours at 37°C in meat-extract broth (500 g. ox heart per litre -1 % peptone+ 0-5% sodium chloride+0-05% para-aminobenzoic acid) enriched with 10% human serum. After centrifugation at 3000 r.p.m. for 20 minutes the bacteria were resuspended in
peptone/saline, and cell-counts were estimated by comparison with Brown’s opacity standards (Burroughs Wellcome). The required dosage was then obtained by further dilution in peptone/saline, and viable counts were carried out by the method of Miles and Misra (1938) using horse-blood-agar plates and pipettes calibrated to deliver 0-02 ml. per drop. The L.D’50S for pneumococci A4, A6, and B2 (table n) were calculated by the method of Reed and Muench (1938), using in each case tenfold dilutions of the pneumococci and six groups of five mice. The groups of mice were placed in a pressure tank (capacity 9-5 c.ft.), and, after preliminary flushing with oxygen for 10 minutes, the pressure was increased over a 12-minute period to 2 atmospheres (1520 mm. Hg). Throughout the exposure to hyperbaric oxygen a continuous flow through the tank was maintained to keep the environment at as near 100% oxygen as possible. The tank was decompressed over a 12-minute period. In experiments 1, 2, 3, and 5 two exposures were employed, separated by an interval of normal atmospheric conditions. In each experiment the initial exposure was made about 45 minutes after intraperitoneal challenge. The control groups of mice were kept under normal atmospheric conditions in the same room (temperature 20°C) as the pressure tank.
Results The results are summarised in tables i-iv. Table I shows the overall results for eight experiments, and table iv illustrates in detail the type of data recorded during each. The effects of hyperbaric oxygen can be gauged in three ways:
(1) By comparing the time-to-90% mortality in each group (table i). (2) By the number of deaths in the oxygen-treated group when 90% (18/20) of controls are dead (table i). 90% mortality was chosen as a convenient endpoint, because’ it embraces the majority of the mouse population and avoids distortion of the results by a single highly resistant mouse. (3) By comparing the mean survival-times of the oxygentreated and control groups (table ill). The third method is a less sensitive index of the protective effect of hyperbaric oxygen than the other two; nevertheless there is a highly significant difference between the means in experiments 1 and 8.
TABLE I-SURVIVAL OF OXYGEN-TREATED AND CONTROL MICE WITH PNEUMOCOCCAL SEPTICAEMIA
*
A and B
are
separate subcultures of the
same
type-III
pneumococcus.
Numbers refer
to
number of mouse-passages before experiment.
580 TABLE III-MEAN SURVIVAL-TIMES
In experiments 4, 6, and 7 the course of the septicaemia was altered (table i). The beneficial effects, however, are transient and are not reflected by a significant difference in the mean survival-times. In experiments 2, 3, and 5 there is no evidence of any prolongation of survival in the
oxygen-treated
oxygen at 2
group.
Four further results
were
obtained:
striking inhibition of growth of pneumococci horse-blood-agar and exposed at 37°C to 2 atmospheres of oxygen either continuously for 18 hours or intermittently for three periods of 2 hours with 2-hour intervals (1) There subcultured
infected host. In experiments 1 and 8 this is seen as an increase in the time-to-90% mortality of the oxygentreated group as against the mortality in controls (table i) and also as an increase in the mean survival-time of the oxygen-treated group to an extent which is statistically highly significant (table ill). Thus, in these two experiments a protective effect was obtained without apparent signs of oxygen toxicity. In experiments 4, 6, and 7 the beneficial effects of hyperbaric oxygen were reflected in the prolongation of timeto-90% mortality in the oxygen-treated group (table i) but the corresponding mean survival-times do not differ significantly (table ill). No protective effect was noted in experiments 2, 3, and 5. Throughout the series no adverse effects of oxygen were apparent. The pneumococcus was chosen as the test organism, because, although classified as an aerobe and facultative anaerobe, it shares many properties with the strict anaerobes. Most of its energy is derived from anaerobic glycolysis, and its lack of catalase and consequent susceptibility to hydrogen peroxide renders it very sensitive to small changes in oxidation-reduction potential (Topley and Wilson 1964, Dubos 1958). In our preliminary experiments its growth was strongly inhibited in vitro by
was on
between. (2) In a pilot study on twelve mice (30-35 g.) large numbers of viable pneumococci were recovered from the heart-blood 15 minutes after intraperitoneal challenge with 500 x 106 ’
organisms. (3) Pneumococci isolated from the heart-blood of mice exposed to hyperbaric oxygen after challenge grew normally when subcultured on horse-blood-agar and were encapsulated. (4) Three groups of 20 mice (30-35 g.) were observed for 6 weeks after (a) intraperitoneal injection of 0-5 ml. peptone/ saline; (b) intraperitoneal injection of 0-5 ml. peptone/saline+ 5 hours continuous hyperbaric oxygen at 2 atmospheres; (c) 5 hours continuous oxygen at 2 atmospheres. No ill-effects were noted.
Discussion
The results show that hyperbaric oxygen can alter the of an aerobic septicxmia, and can, by its antibacterial activity, significantly prolong the survival of the
course
TABLE IV-MORTALITY OF OXYGEN-TREATED AND CONTROL MICE THROUGHOUT A PNEUMOCOCCAL SEPTICaeMIA
(EXPERIMENT 8)
atmospheres.
Pneumococcal virulence is associated with the degree of capsulation, and there is no evidence that the production of soluble toxins plays any part in its pathogenicity (Topley and Wilson 1964). When injected intraperitoneally in mice, pneumococci rapidly enter the bloodstream, and death results from invasion and multiplication in the tissues. Hence the adoption of a mouse-pneumococcal system permitted exposure of live, multiplying, virulent aerobic bacteria to 2 atmospheres of oxygen in the arterial blood. Mice are convenient hosts, because, like humans,
they
are
highly susceptible
to
oxygen
poisoning. Hyper-
baric oxygen can therefore only be beneficial when it can exert its toxicity selectively to produce bacteriostasis (McAllister et al. 1963) rather than tissue damage. In the chosen system the severity of the infection progressively increases the mortality-rate with eventual death of all controls. In any one experiment their percentage mortality is a function of time as well as of the size of the inoculum; for example, in experiment 8 the same dose, namely 125 x 106 pneumococci, is the L.D.5o at 91/2 hours, the L.D.76 at 11 hours, the L.D.90 at 20 hours, and the L.D.loo at 29 hours (table iv). In our experiments all the oxygentreated mice also died eventually and protective action was apparent not as an overall difference inmortality between the control and oxygen-treated groups but as a prolongation of " time-to-death " of the oxygen-treated group. This is illustrated in experiment 8 (table iv) where 50% mortality is reached at 15 hours (51/2 hours’ prolongation), 75%mortality at about 28 hours (17 hours’ prolongation), 90% mortality at 29 hours (9 hours’ prolongation) and 100% mortality at 32 hours (3 hours’ prolongation). The failure of hyperbaric oxygen to influence the overall mortality is possibly due to its bacteriostatic rather than bactericidal action. Several broad conclusions can be drawn from the results: When the time-to-death of the majority of the controls very short (e.g., in experiment 3) the overwhelming nature of the infection precluded effective protection either by the hyperbaric oxygen or the natural defences of the mice. On the other hand, (2) when the course of the control infection was prolonged
(1)
was
581
The local application of hyperbaric oxygen (see figure) could prove beneficial in infected superficial wounds and burns, infected ischaemic skin-flaps, and in acute infective gangrene.
Summary
Locally applied hyperbaric oxygen. Patient is in air at 2 atmospheres. The foot is encased in filled polyethylene bag.
an
oxygen-
example, in experiment 2, any bacteriostasis producec by hyperbaric oxygen would have been nullified by furthel as, for
bacterial multiplication, and would therefore not have been reflected by the relatively insensitive indicator-namely, death of the mouse. In both these circumstances-the failure oi hyperbaric oxygen to control either the overwhelming or the more chronic infection-an analogy with antibiotic therapy can be made. (3) The best protective effects are seen between these two extremes (e.g., in experiments 1 and 8) when death of the majority of the controls occurred 10 to 20 hours after challenge.
The survival of mice with pneumococcal septicaemia can be prolonged by exposure to oxygen at 2 atmospheres (1520 mm. Hg) shortly after intraperitoneal challenge. In 2 out of 8 experiments the difference between treated and control groups was highly significant; in 3 experiments the beneficial effects were transient; and in the remainder there was no evidence of protection. The variation in results may be analogous with antibiotic therapy.
Infections by other sensitive aerobic bacteria-e.g., Staph. aureus, Esch. coli, Ps. pyocyanea, and Strep. viridans -might be amenable to treatment with hyperbaric oxygen, either alone or combined with conventional antibiotics, provided that they are in situations where antibacterial oxygen tensions are readily attainable, such as in the arterial blood and on the surface of the body. We wish to thank Sir Charles Illingworth and Prof. R. G. White for their support and encouragement; Dr. Iwo Lominski for his guidance throughout the experiments; Dr. R. A. Robb, of the department of mathematics, Glasgow University, for the statistical analysis; Mr. George A. Thomson for the supply and care of the mice; and Mr. G. R. Kerr for the photography.
REFERENCES with the bacteriostatic antibiotics, the J. W. (1945) Physiol. Rev. 25, 24-40. Bean, the is to longer infecting organism exposed hyperbaric Brummelkamp, W. H., Hoogendijk, J., Boerema, I. (1961) Surgery, 49, 299. Boerema, I., Hogendyk, L. (1963) Lancet, i, 235. oxygen the greater the chances of therapeutic success de Almeida, A. O., Pacheco, G. (1941) Rev. bras. Biol. 1, 1. seem likely to be. Exposure is limited, however, by the Dubos, R. J. (1958) Bacterial and Mycotic Infections of Man. London. S. F., Rose, N. R., Maurizi, J., Lanphier, E. H. (1964) Lancet, i, danger of oxygen toxicity, and in our experiments times Gottlieb, 382. were chosen which produce no overt toxic effects in mice Hopkinson, W. I., Towers, A. G. (1963) ibid. ii, 1361. Klopper, P. J., Brummelkamp, W. H., Hoogendijk, J. L. (1962) Pr. méd. or man. Pneumococci very rapidly invade the blood41, 1874. Lambertsen, C. J., Ewing, J. H., Kough, R. H., Gould, R., Stroud, M. W. stream and accordingly oxygen therapy was begun as soon (1955) J. appl. Physiol. 8, 255. as possible after injection, since once the tissues have been Ledingham, I. McA. (1963) Personal communication. T. A., Stark, J. M., Norman, J. N., Ross, R. M. (1963) Lancet, invaded to any degree the chances of achieving significant McAllister, ii, 1040. (1964) ibid. i, 499. protection are greatly reduced. Miles, A. A., Misra, S. S. (1938) J. Hyg., Camb. 38, 732. The therapeutic response depends on the interaction of Reed, L. J., Muench, H. (1938) Amer. J. Hyg. 27, 493. Topley and Wilson (1964) Principles of Bacteriology and Immunity (edited a number of variables, such as inoculum size, pneumoby G. S. Wilson and A. A. Miles); vol. I. London. Wallyn, R. J., Gumbiner, S. (1963) Proceedings of 1st International Congress coccal virulence, mouse-weight, and the timing and duraon Clinical Application of Hyperbaric Oxygen. Amsterdam. tion of oxygen treatment (table I). The size of the inoculum could only be roughly gauged before injection, and pneumococcal virulence varied with the age of the subculture and the number of successive mouse-passages HYPERBARIC OXYGEN IN THE before each experiment (table 11). Accordingly, on account. TREATMENT OF THE POSTOPERATIVE of the small number of observations and the lack of LOW-CARDIAC-OUTPUT SYNDROME precise control of some of the governing factors their individual roles in the differing degrees of protection M. H. YACOUB could not be accurately assessed. M.B. Cairo, F.R.C.S., F.R.C.S.E., F.R.C.S.G. The protective action of hyperbaric oxygen in infected SENIOR SURGICAL REGISTRAR* mice is further evidence that it may be of value in the G. L. ZEITLIN treatment of some aerobic infections in man, either as an M.B. Cantab., F.F.A. R.C.S. adjunct to conventional antibiotics or alone, where the SENIOR ANÆSTHETIC REGISTRAR causal organisms are antibiotic resistant or inaccessible. LONDON CHEST HOSPITAL, LONDON, E.2 The causal microorganisms must be sensitive to hyperbaric IT has been our experience that patients who develop oxygen-e.g., Staphylococcus aureus, Escherichia coli, Pseudomonas pyocyanea, and Streptococcus viridans-and the low-cardiac-output syndrome in association with pulmonary hypertension after cardiac surgery seldom must be sited where an oxygen tension of 2 atmospheres recover despite vigorous treatment. We report here the is readily attainable. The latter proviso includes arterial of a case patient who was successfully treated by means blood (Lambertsen 1955, Ledingham 1963), pulmonary of hyperbaric oxygen therapy. alveoli, and, in addition, any area of the body surface if oxygen is applied to it locally while the patient is in air at Case-report
In
common
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2
atmospheres (see figure).
Hyperbaric
oxygen has been used with some success in anaerobic infections, but may also be of value in aerobic septicxmias or in combination with antibiotics in subacute bacterial endocarditis where it could shorten treatment.
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A 50-year-old man was admitted to the London Chest Hospital on Oct. 23, 1964. He had a history of productive cough, recurrent hxmoptysis, and dyspncea on exertion for 21 years. He had been discharged from the Army 20 years *Present address:
Brompton Hospital, London, S.W.3.