80

Goligher et a1.1o examined 23 cases of local recurrencefollowing restorative operations for carcinoma of therectum or recto-sigmoid ; 15 of these recurrences wereunexpected and may, they consider, have been caused byimplantation, at the time of operation, of free tumour cellspresent in the faeces. In 6 of 55 patients operated on byWarren Cole 11 the growth recurred in a similar manner ;and this led him and his associates 12 to investigate further50 specimens containing carcinoma for the presence ofmalignant cells free in the bowel lumen. Smears were 82%positive within 5 cm. of the lesion ; the proportion fell inalmost linear fashion with increasing distance from thelesion, and only 10% were positive at 25 cm. or over.When ligatures had been placed around the bowel oneither side of the growth, smears taken beyond them werenegative ; from this it seemed reasonable to suppose thatoperative manipulation increased exfoliation and raisedthe number of potential seedlings of malignant cells.Cole therefore recommends occlusion of the bowel withtapes above and below the lesion before mobilisation.The St. Mark’s group 10 instil a solution of one in fivehundred perchloride of mercury to kill cells free in thelumen, and Abel 13 agrees that this measure is effective.

Nevertheless, we cannot be sure that malignant cellsdo in fact grow when implanted at the suture line. Theoccurrence of metastases in the abdominal scar indicatesthat malignant cells may be implanted by the surgeon’shand or by the growth being delivered through the wound.But some workers maintain that the colon with a growthis in a generalised precancerous state in which frankmalignancy can be precipitated by simple trauma. Thepoint would be nicely settled if exfoliated cells taken fromthe bowel lumen or surface of the growth were found togrow in tissue-culture. Coman 14 has succeeded ingrowing free carcinoma cells from the ascitic fluid of

patients with growths of the stomach. The same methodmight be applied to carcinoma of the colon, but cultureof direct smears from the bowel lumen would be impossiblebecause of bacterial contamination. z

10. Goligher, J. C., Dukes, C. E., Bussey, H. J. R. Brit. J. Sung.1951, 39, 199.

11. Cole, W. H. Arch. Surg. 1952, 65, 264.12. Grew. E. A., Laws, J. F., Cole, W. H. J. Amer. med. Ass.

1954, 154, 1251.13. Abel, L. See Brit. med. J. 1954, i, 1257.14. Coman, D. R. Cancer Res. 1943, 3, 526.15. Baumgarten, O., Betcher, A. M. Anesthesiology, 1954, 15, 188.16. Benson, J. H., Reeve, E. B., Taylor, G. W. Guy’s Hosp. Rep.

1951 100, 129.

REBREATHING IN ANÆSTHESIA

THE basic methods of delivering anaesthetic gases andvapours have changed very little in the past decade.Most British anaesthetists use a closed or semi-closed

system with partial rebreathing. These techniques havedisadvantages, which have been summarised by Baum-garten and Betcher,15 who themselves advocate non-

rebreathing methods.The two principal drawbacks of closed or semi-closed

techniques are increased respiratory resistance and

possible carbon-dioxide accumulation. Both are to someextent combined in anesthetic sequences that includemuscle relaxants or central respiratory depressants-particularly when used haphazardly-and the very lowventilation-rates that not uncommonly result enhancethe dangers. In the " to-and-fro " method of carbon-dioxide absorption the average pressure at the lipsduring quiet breathing was found to be -3 mm. H2Oduring inspiration and -;- 3 mm. H2O during expiration,while with a circular absorber the figures were -10 mm.and - 10 lllm.16 These pressures are not very high,though at the extremes of age they might cause thepatient considerably increased effort. Carbon-dioxideaccumulation is a more likely hazard even with a soda-lime canister in the circuit, since quiet breathing of ananesthetic mixture rich in oxygen, though fully oxygenat-ing the blood, may not remove carbon dioxide. Con-

trolled or assisted respiration does not necessarily avertthis risk-indeed it may lull the anaesthetist into a falsesense of security-but it will overcome the slight resis-tance of the apparatus. In a semi-closed circuit withoutabsorption, the amount of carbon-dioxide accumulationdepends on the flow of gases, while the resistance is

primarily governed by the setting of the expiratory valve.With this method elimination of rebreathing would

require a very uneconomical flow-about 15 1. per min.17Baumgarten and Betcher advocate the use of a non-

return valve on the semi-closed system, to preventrebreathing and eliminate all resistance other than thatof the expiratory valve. One advantage is that themixture which the patient breathes resembles as closelyas possible that delivered from the machine, since thereis no dilution from rebreathing. The main disadvantageis high cost. Even with non-rebreathing techniquesrelatively rapid gas flows are necessary ; and nitrousoxide, on account of the quantity needed, is one of themost expensive items in modern anaesthesia. On theother hand, methods depending on carbon-dioxideabsorption are essentially economical and have fewdisadvantages. Non-rebreathing methods may bedesirable on specific occasions-for patients at theextremes of age or when spontaneous quiet respirationwithout carbon-dioxide accumulation or breathing againstresistance is needed (as in neurosurgery) so that surgicalconditions in the wound are not adversely affected.Advances in apparatus or technique cannot take the

place of competent anesthetists, who should select themethod best suited to the operation, the patient, andtheir own capabilities. ,

17. Molyneux, L., Pask, E. A. Brit. J. Anœsth. 1951, 23, 81.18. Miller, W. S. Amer. J. Roentgenol. 1926, 15, 399.19. Allison, P. R. Thorax, 1947, 2, 169.20. Brock, R. C. Ibid, 1948, 3, 88.21. Massie, J. R. jun., Welchons, G. A. Ann. Surg. 1954, 139,

624.

PULMONARY BLEBS AND BULLÆ

A PULMONARY bleb, according to Mi-Her,1-8 is due to anescape of air into the alveolar layer of the pleura, whereasa bulla arises from the distension of alveoli with eventual

rupture of their walls. Both can give rise to spontaneouspneumothorax ; and a bulla, because of a bronchialor bronchiolar ball-valve mechanism,19 may enlargeenormously and compress sound lung tissue with correr,7ponding loss of pulmonary function. Sometimes, indeed,a, giant bulla may occupy a hemithorax and may bemistaken for a spontaneous pneumothorax on cursoryinspection of a radiograph, although closer examinationwill usually reveal trabeculse, the appearance of a rimof lung at the costophrenic angle or apex, and absence ofthe lung mass at the hilum. It is important to distinguishthe conditions, because needling a bulla may lead to atension pneumothorax.

Recurrent spontaneous pneumothorax is commonlytreated by pleurodesis, and Brock 20 emphasised the

importance of first excluding a localised bulla as thesource of the trouble, for this should be treated byexcision. He pointed out that such a bulla may escaperadiographic detection, and thus thoracoscopy shouldnever be omitted. Large bulle that are compressingsound lung tissue may also be excised, with consequentimprovement in pulmonary function. Massie andWelchons 21 report six further cases in which pulmonaryblebs and bullse were surgically removed, and remarkthat even when there are multiple bullae in a lobe localexcision may be possible, thus avoiding the sacrificeof sound lung tissue entailed in lobectomy. How far

surgical treatment is practicable when bullae are multipleand bilateral has yet to be decided.

We regret to record that Dr. H. A. DuNLOP, physicianwith charge of outpatients to Charing Cross Hospital, diedon July 2, at the age of 50.