A. Insufficient Penetration Of The Liquid

Whenever examination of the curve of sterilisation shows that, before attaining surgical asepsis, the line has become horizontal, we may be sure that a fault in technique has been committed. We know, in fact, that the diminution in the number of microbes in a wound should progress steadily, whenever the antiseptic liquid is carried into all the regions infected. If sterilisation is not achieved, in the first place it is necessary to ascertain that the Dakin's solution contains the needful amount of hypochlorite, and afterwards to look into the possible causes which could hinder the penetration of the liquid throughout the wound. The causes are generally as follows:-

1st. The distribution of the liquid in the wound has not been completely accomplished, by reason of: {a) slipping or detachment of one of the conducting tubes; {b) obliteration of the lumen of a tube by blood-clot; (c) kinking in a tube, due to faulty placing; (d) the omission to put a conducting tube in some diverticulum of the wound. Should a tube be placed in a passage too narrow which it fits tightly, there can be no return flow of liquid between the wall of the tube and that of the wound, and, in consequence, no instillation. Careful examination of the wound will enable us to ascertain the presence of one or more of these causes of error.

2nd. There is some error in the installation of the irrigating apparatus. The fault most frequently committed is that of putting a drop-counting appliance in communication with several tubes. As the output is very small, the liquid, obeying the dictates of gravity, runs down one of the tubes while nothing goes to the rest. The same thing may happen in intermittent irrigation, if the calibre of the principal tube or the inferior orifice of the flask (reservoir) is too narrow. In this case the outflow is insignificant, and instead of the liquid being distributed to four or eight tubes, it passes along only a few of them, and, in consequence, a whole region of the wound is deprived of liquid. This mistake will be avoided if the instructions we have already given on the subject of the relative calibres of the different tubes and the installation of the irrigation apparatus be followed precisely.

3rd. The quantity of liquid is insufficient. Inadequate instillation is most frequently seen, when, instead of using irrigating apparatus, a syringe is employed. As the tubes are multiple, the nurse has to spend much time in injecting the needed amount with a syringe. Therefore, whenever this method is in use, the quantity of antiseptic is frequently found to be insufficient. The same thing happens in using irrigation apparatus, when, through negligence, the irrigations are omitted, or made at too long intervals during the night. Likewise when a tube passed into too narrow a track blocks up its lumen, so that no circulation is established (Fig. 65). By carefully examining a wound we find indications which lead us to suspect the insufficiency in quantity of liquid. Two symptoms present themselves in these cases. One is, the pus beginning to have an unpleasant odour, for a well-irrigated wound should be perfectly inodorous. The second is absence of the characteristic changes in the secretions. The discharge from a well-irrigated wound should be thicker and more transparent than the normal secretion. The presence of unmodified secretions in a wound permits one to assert, either that the liquid does not contain the sufficient amount of hypochlorite, or that the instillation is not being carried out in the prescribed manner.

B. Excessive Quantity Of Liquid

When the liquid is allowed to flow too long over the surface of a wound, or in quantity too abundant, the absorbent cottonwool of the dressing, and evaporation, are not equal to the task of getting rid of the excess of fluid. The bed becomes flooded, the limb bathed in Dakin's solution, and the skin becomes irritated. An excessive quantity of liquid has no deleterious action on the wound, but it worries the patient. He is in an uncomfortable plight, and ulceration of the skin, more or less painful, may be produced. Therefore the nurse must learn how to regulate the quantity of liquid so that the wounds are sufficiently moistened without the patient being made damp. With a little attention nurses soon avoid injecting too much liquid into the wound. Besides it is always better to use too much than too little, for the inconvenient results of too much liquid are not serious and can be remedied easily. By applying carefully squares of vaselined gauze (p. 158) to the skin about the wound, it can be protected completely against the lesions produced by an excess of liquid.

Fig. 65.   Relative dimensions of the orifice of the wound and of the conducting tube, a, Faulty arrangement.   The opening is much too small, the liquid is under pressure in the limb, and its circulation is impossible. b, Correct arrangement.   The opening is large enough to allow the free return of the liquid between the wall of the wound and the outside of the tube.

Fig. 65. - Relative dimensions of the orifice of the wound and of the conducting tube, a, Faulty arrangement. - The opening is much too small, the liquid is under pressure in the limb, and its circulation is impossible. b, Correct arrangement. - The opening is large enough to allow the free return of the liquid between the wall of the wound and the outside of the tube.

C. Excessive Pressure

We have noticed already that an excess of pressure may be due to two quite different causes - a too great elevation of the reservoir of fluid above the level of the bed, or to smallness of the incision which hinders a ready reflux of the liquid between the walls of the wound and the conducting tube (Fig. 65). Excessive pressure of liquid in the wound brings about distress. The moment instillation causes a patient pain it must be discontinued, and the error of technique which is the cause of the pain must be discovered.