A handbook on antiseptics

Front matter

Book

GopyrigM°_

COPYRIGHT DEPOSffi

Preface

The main object of this handbook is to give a concise account of the chief chemical antiseptics which have been found useful for surgical purposes during the present war. Some of the publications on this subject are not readily accessible to many who wish to inform themselves as to current European practice, and the requisite information has not yet, so far as we know, been collected into a form handy for reference. It appeared, therefore, that the present work might prove of use to surgeons and others in this country who are now taking up military duties connected with the care of the wounded.

The unparalleled severity and frequency of wound infections in the present war has led to considerable advances in our knowledge of antiseptics and of methods for their successful employment. These advances have already proved to be of great value in the treatment of septic conditions in civil and industrial practice.

No endeavor has been made to make a complete compendium of the innumerable antiseptics and disinfectants that have been proposed from time to time, for text-books already exist in which most of these substances are adequately described, and no good purpose would be served by duplication. Our principal aim has been to collect in convenient form the methods of preparation and use of various new antiseptics and modifications of old ones which have received some measure of endorsement by military surgeons during the past three years.

viii PREFACE

The utility of antiseptics, properly used as adjuncts to efficient surgery, is becoming more firmly established as the war proceeds. Surgeon General Sir George Makins in the Hunterian Oration for 191 7 says: "The most useful practical test of the efficiency of any method of wound treatment is furnished by the observation of the dates at which microorganisms disappear from the surface of the exposed tissues and at which the wound may be safely and permanently closed by suture or other means. When subjected to this test the antiseptic method has proved itself more rapid and more trustworthy than the phylacagogic or saline method of treatment."

A large part of the investigations on antiseptics carried on during the last three years has been done at the instance of the British Medical Research Committee. We are indebted to Dr. W. Morley Fletcher of that Committee and to the editors of the British Medical Journal and the Journal of the Royal Army Medical Corps for permission to use parts of the reports published in the journals referred to.

Purely surgical details concerning the use of antiseptics do not lie within the scope of the present book although some of the principles essential to the successful use of antiseptics are briefly referred to. A short statement of the use of antiseptics in the treatment of carriers of infectious organisms is, however, included. Owing to similarity in the substances used we have deemed it advisable to include a brief statement of the use of certain disinfectants of the chlorine group for the sterilization of drinking water and the disinfection of hospital ships.

September 1, 191 7.

The Herter Laboratory

New York.

Contents

PAGE

Preface . . . . ' vii

Chapter I. General Introduction : Classification — laws of disinfection — influence of media — choice of antiseptics — modes of application . . i

Chapter I General Introduction

The terms " antiseptic," " disinfectant/' and " germicide" are frequently used irrespective of their precise significance. Strictly speaking, an antiseptic is a substance which inhibits the reproduction of microorganisms, but it need not of necessity manifest great killing or "germicidal" action on such organisms. Substances such as boric acid or sodium benzoate are examples of compounds which are fairly effective in restraining the multiplication of bacteria though possessing feeble germicidal properties. Most of the substances used in the prevention of wound sepsis possess both antiseptic and germicidal properties though perhaps they are most commonly termed antiseptics.

The term " disinfectant " should clearly connote a substance which destroys infecting agents and hence is identical with a germicide, but the word has come to be used in a popular sense, irrespective of complete sterilization, to indicate some of the phenomena commonly associated with efficient disinfection, such as a deodorant effect. 1 The use of the words " disinfectant " and " disinfection " in any other sense than that first indicated is to be deprecated.

1 An account of many important hygienic applications of disinfectants which are beyond the scope of the present work will be found in Colonel Lelean's book on "Sanitation in War." Churchill. London.

Classification of Antiseptics. — For various reasons it is quite impossible to formulate a perfectly logical classification of antiseptics. In the first place, almost every soluble substance, provided it can be obtained in sufficient concentration, is capable of exerting some antiseptic action, so that theoretically it would be necessary to classify most known organic and inorganic substances, and such an undertaking is obviously useless and unnecessary. For practical considerations it is sufficient to limit ourselves to those substances which have found fairly extended use as antiseptics. In classifying these we may endeavor to divide them according to the nature of the substances themselves or according to their mode of action. The latter method has much to commend it, but unfortunately we know but little of the intimate details of the act of disinfection as carried out with even the simplest substances, such as phenol or hydrogen peroxide.

Chemical antiseptics naturally fall into two main classes of compounds — inorganic substances as exemplified by bodies such as hydrogen peroxide, chlorine, and metallic salts, such as those of mercury and silver, on the one hand, and on the other organic, or carbon, compounds such as phenols, aromatic acids, dye-stuffs, such as malachite green, etc., etc. But in these two main groups of inorganic and organic antiseptics are found substances of widely different properties and above all showing enormous variations in stability. This instability of some of the most widely used antiseptics is a point of fundamental importance, for upon a clear recognition of this fact will depend, to a considerable extent, success or failure in their practical use. This chemical instability is of various kinds, as a few examples will serve to show.

Hydrogen peroxide is a good example of an unstable inorganic disinfectant. The exact way in which it destroys microorganisms is not clear but is undoubtedly connected with its oxidizing action. Now when hydrogen peroxide is placed on the surface of an infected wound, it is rapidly decomposed, part of the oxygen of the peroxide being used up in oxidizing organic compounds and much of it being liberated as oxygen gas owing to the decomposition of the peroxide by a widely distributed enzyme, "catalase." The net result is that after a period of time which may be almost incredibly short no undecomposed hydrogen peroxide remains and disinfection proceeds no further towards completion. For, as will be shown later, the rate at which disinfection proceeds is directly related to the concentration of the antiseptic. Obviously, this instability indicates that hydrogen peroxide should be either frequently renewed or restricted in its use to conditions where temporary action only is required.

The chlorine group of antiseptics includes a number of important substances such as chlorine itself, hypochlorous acid and its sodium and calcium salts, and organic "chloramines" — i.e. substances containing chlorine attached to nitrogen in the form of XC1 groups. They are all characterized by marked instability, since in disinfection they react not only with the cell constituents of microorganisms but also with most other substances which are apt to accompany bacteria. In so reacting, the active chlorine of the antiseptic is eventually converted either into inert chlorides or into inert organic substances in which the chlorine has become united to carbon. Thus in using the chlorine antiseptics, as with hydrogen peroxide, the process of disinfection will only go on so long as some of the active substance remains undecomposed, and in practical use means must be taken for the renewal of these antiseptics at suitable intervals, in cases where sterilization is not promptly completed.

In the examples of unstable antiseptics just cited, the active substances are decomposed during disinfection and cannot be regenerated. In another large class of antiseptics the active agent is not totally destroyed during disinfection but is rendered relatively inactive. Good examples of this are found among many metallic salts; mercuric chloride and silver nitrate, for example, are much less effective when acting on bacteria suspended in hard water than when acting on washed bacteria suspended in distilled water. Similarly, phosphates and other salts frequently found in wound exudates inhibit the action of metallic antiseptics. In these cases disinfection by the metallic salts is impeded not by the complete destruction of the compound, as with hydrogen peroxide or chlorine antiseptics, but through the conversion of the metallic salt into an inactive form. This conversion may be effected either by precipitation of the metallic component in an insoluble form, or by changing its state — e.g. changing its condition of ionization in aqueous solution. In such cases the antiseptic substance is rendered inert but not destroyed and, theoretically at least, could be regenerated by suitable chemical means.

Lastly, there are other substances used as antiseptics which apparently are stable during disinfection or at least comparatively so. Familiar examples of compounds of this type are found in the phenols and in aromatic substances of the dye class. These compounds apparently are not readily decomposed by the cell constituents of bacteria nor by most substances which are apt to accompany the latter. It has been suggested that some of these antiseptics act by virtue of changes they produce in the surface layer of the bacterium so that the latter is rendered permeable by the antiseptic. But even with these relatively stable substances there is a definite limit to the amount of disinfection which any given quantity of the compound can accomplish and this amount will vary according to the conditions under which the antiseptic acts. This fact will be noted again in the following section in which some reference is made to the laws governing disinfection.

The following table shows the relative stability or instability of some of the common groups of antiseptics :

Inorganic Antiseptics

Hydrogen Peroxide and some of its

derivatives Chlorine

Hypochlorous Acid and its Salts

Bromine and Iodine Boric Acid and its Salts Mercury Salts

Silver Salts

Bismuth Salts

Zinc Salts

Unstable, easily decomposed during

disinfection Unstable, easily decomposed during

disinfection Unstable, easily decomposed during

disinfection Less unstable than chlorine Stable Often inactivated by precipitation or

otherwise Often inactivated by precipitation or

otherwise Often inactivated by precipitation or

otherwise Often inactivated by precipitation or

otherwise

Alcohol, Ether, etc Iodoform Formaldehyde

Hexamethylenetetramine and its derivatives Phenols, Naphthols, and derivatives Aromatic Chloramines

Dyes such as malachite green, acriflavine, etc.

Organic Antiseptics Stable

Fairly stable Unstable Mostly stable

Mostly stable

Unstable, easily decomposed during disinfection

Mostly stable, though sometimes reduced to leuco-forms, and often adsorbed by tissues

It is a surprising fact that this varying stability of antiseptics is so little realized by many workers. Current literature is full of reports of experiments in which bacteriologists have added reactive unstable substances, such as hypochlorous acid, to media which cause their prompt disappearance in dilute solution ; the mixture containing little or no remaining antiseptic is subsequently sown with organisms and astonishment is expressed at the inefficiency of the substance employed as a disinfectant. This important point will be referred to repeatedly in later sections.

The Laws Governing Disinfection. — These have been chiefly worked at by Miss Chick. 1 Earlier experiments were carried out by Kronig and Paul 1 and by Madsen and Nyman. 2 It would be out of place to go into the details of the elaborate experiments and calculations necessary to elucidate the principles of disinfection but a brief summary of the essential results may be given. Miss Chick observed the number of bacteria that survived, at varying intervals of time, the action of a constant quantity of a stable antiseptic, such as phenol, at a constant temperature, on a known number of organisms. By utilizing these results mathematically she was able to calculate a velocity coefficient for the disinfecting action of the substance. The main result of these experiments was to show that in all essential particulars the act of disinfection could be regarded as obeying the laws governing a simple chemical reaction, the disinfectant representing one reagent and the bacteria the other. This conception is of the greatest importance since the cardinal points of efficient disinfection, namely adequate active mass or concentration of antiseptic, time of action, and perfect contact, are thereby experimentally established.

The influence of temperature upon the rate of disinfection is interesting since here again a close analogy exists between ordinary chemical reactions and disinfection. The velocity of disinfection increases with rise in temperature in a manner similar to that of an ordinary chemical reaction. Some idea of the magnitude of the effect of temperature may be gathered from the fact that with metallic salts the mean velocity of disinfection increased 2-4 fold for a rise in temperature of io° C, while with phenol it was as high as eightfold, using B. paratyphosus as test organism in each case.

It must be remembered, however, that the similarity in the mathematical relations governing the velocity of simple chemical reactions and disinfection does not of necessity prove that the act of disinfection is a chemical one, although with some antiseptics this is almost certainly the case.

Influence of Media. — The capacity of a disinfectant to kill microorganisms is dependent to an extraordinary degree upon the conditions under which it acts. Almost invariably the greatest germicidal activity is shown when the substance acts upon bacteria freed from contaminating culture media and suspended in distilled water or salt solution. The presence of proteins and similar substances, e.g. peptones, usually causes a huge reduction in the germicidal activity of most substances. In the presence of pus, in which many of the organisms are partly ingested in the bodies of the dead leucocytes and hence difficult to attack, the results are still less favorable. The following table gives some idea of the reduction in germicidal activity of some of the common antiseptics acting for two hours at room temperature on staphylococcus aureus (i drop of 24 hours broth culture) in a total volume of 5 cc. of either water or 50 per cent horse serum. The antiseptics were in all cases added last of all to the mixtures :

Antiseptic

Phenol ....

Salicylic Acid . .

Hydrogen Peroxide Iodine ....

Mercuric Chloride 1 Silver Nitrate x . .

Sodium Hypochlorite Chloramine-T . .

Staphylococci in Water

' 1 : 250 - , 1 : 500 +

1 : 1,000,000 +

negative subcultures.

The — sign indicates sterilization as evidenced by while the + sign indicates incomplete disinfection.

1 No antidote was used in these experiments to prevent the action of traces of the salt in the subcultures. (Cp. p. 52.)

In order to illustrate the difficulty of sterilizing pus, some selected experiments made by W. Parry Morgan x may be cited. In these experiments one part of pus was mixed with nine parts of antiseptic and after ten minutes 10 cmm. were planted in liquid agar which was then shaken and incubated. It was found that when the antiseptic was strong the number of colonies could be counted readily, but when it was weak the agar became opaque with innumerable colonies. The results are, of course, comparative and do not lend themselves to strict quantitative expression, for the specimens of pus vary much among themselves.

Table showing the Effects of Antiseptics upon the Growth of Bacteria in Pus

(Dakin's Solution)

Eusol

(Bleaching Powder and Boric Acid)

When the proportion of pus to antiseptic was higher than in the above experiments, the disinfecting action was still further diminished.

A few substances, such as some derivatives of hexamethylenetetramine, are known whose germicidal action is said not to be materially affected by the presence of serum, and one striking example exists of a substance which is apparently actually more active in serum than in water. This compound prepared by Benda and termed trypaflavine but now known

1 Brit. Med. Journ., May 13, 1916.

as acriflavine (sometimes simply flavine) has been shown by Browning l and his colleagues to kill staphylococci in serum at one tenth the concentration necessary when the same organisms are suspended in peptone solution. Experiments with pus, however, showed much higher concentrations were necessary to achieve sterilization than with peptone or serum media.

The causes of these huge variations in the germicidal action of antiseptics under various conditions are but slightly understood. The reduction in the case of members of the chlorine group can be accounted for to a considerable extent by the rapidity of the chemical interaction of the disinfectant with the protein medium, with the production of inert substances if the proteins be in sufficient excess. But other causes must be at work where the more stable antiseptics such as phenol and the dye-stuffs are concerned. It is frequently said that the antiseptic is " quenched " or " fixed " by the protein medium, but these terms do not carry much enlightenment, nor does the suggestion that the molecular condition of the antiseptic is influenced by the presence of colloids in the medium. The low germicidal action shown by most antiseptics against pus is due in part no doubt to the mechanical difficulties of penetrating the mucoid particles in the pus. Parry Morgan has shown, moreover, that when the organisms in pus, or added to it, have undergone phagocytosis they are less readily destroyed by antiseptics. The reduction in antiseptic activity of a substance in the presence of any particulate matter has been often observed 2 and is probably connected with the surface adsorption of the antiseptic by the particles with consequent reduction in its effective concentration.

The Choice oe Antiseptics. — The selection of antiseptics for various purposes requires the consideration of a

1 Brit. Med. Journ., Jan. 20, 1917.

2 Chick and Martin, Journ. of Hygiene, 8, p. 654, 1908, number of factors. The possession of high germicidal activity, as ordinarily tested in the presence of media comparable with those in which the disinfectant is to act, is of course desirable. But it is equally important to bear in mind the concentration at which the substance may be used, for a relatively innocuous substance used in fairly high concentration will often give much more satisfactory results than lower concentrations of more active substances. The speed of disinfection is also an important question for it varies enormously with different types of antiseptics. Antiseptics of the chlorine group and iodine are among the most rapid, while the dyes and some metallic salts are relatively slow. An inspection of the tables in Chapter VII, in which a heavily infected mixture of blood serum and muscle extract was treated with various antiseptics at about the concentration recommended for wound treatment will give a good idea of their relative speed of action and potency under the conditions selected.

The ideal surgical antiseptic should effect complete sterilization within its sphere of action without causing any damage to animal cells. At the moment such a substance does not appear likely to be found, but on the other hand it is surprising to see how little damage may be done to animal tissues by some active antiseptics. An important method of judging of the injurious action of antiseptics is to investigate the condition of the leucocytes in wounds recently treated with the substance under consideration. In general it appears from experiments in vitro that, with the strength of antiseptics commonly used in surgery, mercury salts and hypochlorites have relatively little effect on phagocytosis as compared with phenol (Parry Morgan). It is a regular phenomenon to observe activity of the leucocytes obtained from wounds which have been recently treated with hypochlorites.

Ingenious methods for determining the influence in vivo of antiseptics on the activities of leucocytes have been worked out by Col. C. J. Bond. 1 Indigo impregnated threads are laid in aseptic or septic wounds with or without antiseptics. After varying periods of time the threads will be found to have become decolorized owing to the ingestion of pigment particles by the leucocytes. It was found that the application of a strong antiseptic, e.g. i : iooo mercury biniodide or i : 20 phenol, to a wound such as that made for the radical cure of hernia or for the removal of varicose veins, does delay to some slight extent the decolorization of an indigo thread placed in it as a drain. But in general it appeared that antiseptic solutions in moderate concentration exercise less influence over emigration and phagocytosis than many surgeons had supposed. There are, however, reasons for concluding that many antiseptics do exert a considerable inhibitive effect on the return immigration of living phagocytes. But if the use of antiseptics does bring about a reduction of the numbers, or inhibit the activities, of pathogenic organisms, not merely in vitro but in the actual wound, then although these reagents undoubtedly do cause the death of a certain number of body cells and prevent others from again reaching the tissues, this is relatively of slight importance if the invading organisms are at the same time materially diminished in numbers or offensive capacity.

Other criteria which need consideration in judging of the suitability of any particular substance as an antiseptic concern the absence of marked irritation of the skin or other tissues to which the substance may be applied, and also its effect on the rate of dissolution of necrotic tissue and the rate of formation of healthy granulations. In general, too, it will be found that antiseptics which coagulate the proteins in wound exudates, e.g. salicylic acid, or strong phenol, are less desirable than those which do not act in this way, since anaerobes are apt to multiply in necrotic tissue more or less surrounded with impermeable coagulum. In contrast with this effect, the solvent action of hypochlorites and the related dichloramine-T on dead tissue is marked and constitutes a valuable property.

But the problem of selecting the most desirable antiseptic is by no means limited to the preceding considerations. It is of paramount importance that judgment should be exercised in choosing a substance which is likely to be effective under the conditions of its employment. Thus any of the hypochlorite solutions which give excellent results when used for the intermittent flushing of infected wounds, partly on account of the rapidity of their action and of their generally inoffensive character, are almost useless when applied in small amounts as a simple wet dressing which is infrequently renewed. In the latter case no active antiseptic persists for any significant length of time and not much more is accomplished than the prevention of secondary reinfection. When prolonged action is required and frequent application is impossible, recourse must be had to more stable mixtures which yield up their store of antiseptic slowly. Examples of such substances are the bismuth iodoform paraffin mixture (B.I. P.) and the oi]y solution of dichloramine- T. These substances will be referred to later.

Finally, it must be once more emphasized that antiseptics at best are only accessories to, and not substitutes for, efficient surgical treatment of infected wounds. The disinfecting action of antiseptics is practically restricted to the wound surfaces and the cavity inclosed by them and none of them appears to have any considerable power of penetration without simultaneous loss of activity. The prompt excision of damaged tissue has now become a routine method in war surgery on the Western Front, and this procedure, renders the effective employment of antiseptics much more certain than it was earlier in the war.

Modes of Application. — Antiseptics are applied in various ways, according to the character of the wound, the nature of the substance, and the kind of action desired. Aqueous solutions are used most extensively. When unstable antiseptics, such as hypochlorites and chloramine-T, are used and prolonged antiseptic action is required — as in the treatment of freshly infected or septic wounds — it is necessary to employ some means of frequently renewing the antiseptic. This end is- commonly accomplished either by irrigation or by intermittent instillation of fresh antiseptic solution into the wound by means of short rubber tubes so arranged that the solution may reach every recess of the wound. This method has been used extensively in the present war and has given excellent results. The technique of the method will be found fully described in a book by Carrel and Dehelly. 1 To obtain the best results with this mode of treatment, a careful observation of details is essential, and as only an outline can be given here reference should be made to the book just mentioned or to numerous original papers in recent publications.

The first step is the mechanical cleansing of the wound by excision, this being omitted as dangerous if the phenomena of inflammation have already set in. The wound is then subjected to active antiseptic treatment. For this purpose sodium hypochlorite — so-called Dakin's solution — is employed at a concentration of 0.5 per cent (see page 23). Great care is taken to insure uniform distribution of the antiseptic by means of the rubber tubes w T hich are usually of fine bore, closed at one end and provided near the closed end with a number of fine lateral perforations. A number of these tubes, depending on the size of the cavity, are disposed within the wound, care being taken that no gauze intervenes between the tubes and the

1 Le traitement des plaies infectes, Collection Horizon, Masson et Cie., Paris, 191 7, tissues and also that the tubes are not so closely applied as to block the perforations. The tubes are led through the outer dressing and kept in position with safety pins. When, as is always the case with large wounds, more antiseptic solution is needed than can be conveniently supplied by using a glass syringe, the ends of the tubes are connected by T pieces to a single tube which in turn connects with a glass reservoir holding a liter of solution which is suspended several feet above the level of the bed. The supply of solution to the wound is arranged by opening for a few seconds every two hours the clip attached to the main tube. An important point is the absence of a drainage opening at the most dependent part of the wound; in fact, the ideal arrangement is attained when the wound is cup-shaped; when it is on the inferior surface of a limb the aperture is partly plugged with gauze to hinder free escape of the fluid. It is important to note that vessels in the base of the wound should not be ligatured with silk since this material is attacked by hypochlorites. The routine bacteriological examination of the wound is important. It is found that when practical sterility has been maintained for two or three days it is safe to close the wound. In the case of wounds that have suppurated, it is advisable to wait a little longer.

In place of the hypochlorite, the more stable chloramine- T has been used to a considerable extent and with particular success in fresh industrial accidents. It is usually used in 0.5-2 per cent solution and its action is similar to that of hypochlorite save that necrotic tissue is less rapidly removed.

The methods of application of the ordinary solutions of less unstable antiseptics such as phenol, iodine, and the metallic salts, call for no special comment.

When the frequent renewal of the antiseptic is impracticable or not desired, recourse may be had to pastes or oils of various kinds, which embody a store of antiseptic that may be gradually utilized. The mild antiseptic action of a paste containing about one per cent of chloramine-T and five per cent of sodium stearate in water is often useful to maintain sterility and prevent reinfection of wounds which have previously received more vigorous treatment. A much more intensive action can be obtained from the use of dichloramine-T dissolved in eucalyptol and paraffin as described on page 39. The amount of active antiseptic which may thus be applied to the wound surface is extremely large and its action is correspondingly prolonged. The method of using this oil is particularly simple and the results appear to be exceptionally good, both as regards the prevention and treatment of sepsis.

A paste possessing moderate potency, introduced by Rutherford Morison, composed of bismuth subnitrate, iodoform, and paraffin, is being widely used with good results both for wounds of the soft tissues and for fractures. The fact that the wounds do not need dressing for several days gives it a great advantage when the number of cases requiring treatment is very large, and because of this it also secures a maximum of rest for the wound.

It must not be forgotten that the employment of pastes as a primary dressing is not free from serious risks and should only be practiced with caution. The use of salicylic acid pastes for the immediate treatment of wounds other than superficial ones is said to have given particularly poor results as anaerobes are apt to flourish in walled off recesses of the wound. The coagulating properties of salicylic acid would especially facilitate such a result.

The administration of antiseptics by intravenous injection is the only method other than that of local application that is at all practiced for military purposes. Eusol has been used to some extent for this purpose l though it is abundantly clear that any action it may have is unconnected with any

1 Lorrain Smith, Ritchie, and Rettie, Brit. Med. Journ., Nov. 13, 191 5. Frazer and Bates, Brit. Med. Journ., Aug. 5, 1916.