BLIND NASAL INTUBATION USING DOXAPRAM HYDROCHLORIDE

Brit. J. Anaesth. (1968), 40, 361

BLEND NASAL INTUBATION USING DOXAPRAM HYDROCHLORIDE BY J. A. H. DAVIES

SUMMARY

Previous authors have referred to the value of hyperpnoea as an aid to blind nasal intubation (Magill, 1936; Human, 1941; Gillespie, 1963; Macintosh and Bannister, 1952; Lee, 1964). Blind nasal intubation can also be performed when respiration is depressed by deep general anaesthesia and during the apnoea produced by a muscle relaxant, but such conditions are often undesirable when blind nasal intubation is most strongly indicated, for example in patients with trismus or ankylosed temporomandibular joints. For patients presenting difficult intubation problems, the safest techniques are those which are effective when the patient is lightly anaesthetized or even awake (Gillespie, 1963; Gold and Buechel, 1960). It is under light general anaesthesia that hyperpnoea is most helpful. Advantage may be taken of the respiratory stimulation which accompanies light ether anaesthesia, but the agent most widely employed to produce hyperpnoea is carbon dioxide. Although under special circumstances hypercarbia may be harmless and even beneficial (Frumin, Epstein and Cohen, 1959; Schultz et al., 1960; Inkster, 1963; Broom and Sellick, 1965; Prys-Roberts, Smith and Nunn, 1967), most authors agTee that high concentrations of carbon dioxide are dangerous and lesser degrees of hypercarbia may exaggerate the ill effects of other drugs and anaesthetic manoeuvres (Price, 1960; Bin and Cole, 1965; Nunn, 1966). Anaesthetic circuits have been designed with great care and ingenuity in an effort to prevent accumulation of carbon dioxide. Because of these considerations the use of doxapram hydrochloride, a new analeptic and respiraF

tory stimulant, instead of carbon dioxide, to facilitate blind nasal intubation was thought worthy of a trial. Doxapram hydrochloride* (Doprarn; A. H. Robins Co.). When 100 mg of doxapram hydrochloride is injected intravenously in an anaesthetized patient respiratory stimulation begins in three-quarters of a minute and rises to a maximum some 2 minutes after injection. A minute volume of 5 l./min can be expected to increase to between 15 and 30 l./min. The respiratory rate rises little, the increased minute volume being due almost entirely to an increased tidal volume. The response is short-lived and within 5 minutes of injection the minute volume has returned almost to normal (Siker, Mustafa and Wolfson, 1964; Stephen and Talton, 1964; Noe, Bourillo and Greifenstein, 1965). The principal toxic effect of an analeptic drug is the production of convulsions. Animal experiments indicate that the dose of doxapram hydrochloride required to cause respiratory stimulation is much less than that which causes convulsions, and that it is safer in this respect than other analeptics (Funderburk and Alphin, 1962; Ward and Franko, 1962; Polak and Plum, 1963). Doxapram hydrochloride is very acid (pH 3.5— 5.0) and forms a precipitate with thiopentone and other alkaline solutions. Particular care must be taken to flush an indwelling needle between injections of thiopentone and doxapram hydrochloride. * Doxapram hydrochloride is not at present available in the United Kingdom.

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A technique is described of blind nasal intubation under light general anaesthesia employing a respiratory stimulant, doxapram hydrochloride. Intubation was successfully achieved with not more than 200 mg of doxapram hydrochloride in 88 of 100 patients. It is suggested that it may be a useful alternative to carbon dioxide for blind nasal intubation.

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362 METHOD

tube. Use was made of extension, flexion, lateral flexion and rotation of the head, rotation of the tube, and transferring the tube to the other nostril. One dose of doxapram hydrochloride 100 mg gave sufficient respiratory stimulation for four or five attempts. If the first dose of doxapram hydrochloride was unsuccessful the dose was repeated and further attempts made. Occasionally it was necessary to give the patient an inhalational agent for a few minutes before the second dose if he had reached too light a plane of anaesthesia. When no success attended the second dose of doxapram hydrochloride the attempt at blind nasal intubation was abandoned and deemed a failure. RESULTS (TABLE i)

Blind nasal intubation was accomplished using not more than two doses of doxapram hydrochloride 100 mg in 88 out of 100 cases. In 70 cases only one dose of doxapram hydrochloride 100 mg was required and in 32 of these cases the tube entered the trachea at the first attempt. In 12 cases blind nasal intubation was unsuccessful after two doses of doxapram hydrochloride (total dose 200 mg). TABLE I

Results of attempts at blind nasal intubation using doxapram hydrochloride. Total number of patients 100 Intubation successful with one dose of doxapram hydrochloride (100 mg) 70% Intubation successful with two doses of doxapram hydrochloride (200 mg) 18% Total successful intubations 88% Failures 12% Success with the first attempt of the tube 32 DISCUSSION

Many factors influence the outcome of attempts at blind nasal intubation, but the persistent anaesthetist can achieve a high success rate at the risk of traumatizing the upper airway. Trauma can be minimized by spraying the nasal cavity with cocaine 5 per cent which produces, in addition to its analgesic effect, intense vasoconstriction and shrinking of the mucous membrane which increases the capacity of the nasal cavity and facilitates passage of the tube. Reduction in vascularity is such that the risk of bleeding following intubation is reduced. In not one of the

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The technique adopted was that originally described by Magili (1928, 1930, 1936), and doxapram hydrochloride was used instead of carbon dioxide to stimulate respiration. One hundred patients, having a variety of minor operations for which intubation was considered to be warranted, were investigated, of whom 49 were male. Except for two children aged 5 :s~d 6 years, ages ranged from 11 to 79 years and body weight from 38 to 83 kg. Premedication consisted of papaveretum or pethidine with atropine or hyoscine. Because doxapram hydrochloride has some pressor activity, patients with arterial hypertension were excluded. Since no knowledge is available concerning its effect on the foetus no pregnant women have been included in the investigation. Ten minutes before induction the nasal cavity was sprayed with cocaine 5 per cent, using a Rogers crystal spray. The total dose was in all cases less than 4 mg. Anaesthesia, in all adult cases except two, was induced with thiopentone (200-500 mg). In one case of dystrophia myotonica and one of carcinoma of the tongue anaesthesia was induced with nitrous oxide and oxygen. Having flushed the indwelling needle, doxapram hydrochloride 100 mg (5 ml) was injected intravenously. Children were given a reduced dose according to their body weight. The patient's head was arranged in the position described as "sniffing the morning air", supported on a bunched-up pillow. When the right nostril was used the fingers of the left hand were used to support the jaw, to keep the lips closed, and to occlude the left nostril. A well-lubricated red mineralized rubber Magili nasal endotracheal tube of suitable dimensions, curvature and consistency was then introduced through the right nostril and advanced so that the tip lay just above the cords. In most cases a tube of 8.5 mm bore was used for men and one of 8.0 mm was used for women. If the tube did not pass easily through the right nasal cavity it was transferred to the left. When the respiratory stimulation of doxapram hydrochloride occurred the tube was advanced briskly during inspiration between the vocal cords and into the trachea. If the first attempts were not successful a variety of manoeuvres was employed according to the misdirection of the

BLIND NASAL INTUBATION USING DOXAPRAM HYDROCHLORIDE

ACKNOWLEDGEMENTS

The author wishes to thank those surgeons at the Radcliffe Infirmary, Oxford, and at Frenchay Hospital, Bristol, whose patients have b:en included in this study. He is most grateful to Professor John OuttonBrock and Dr. Bryce-Smith for their advice and encouragement, and to A. H. Robins Co., for liberal supplies of doxapram hydrochloride. REFERENCES

Bin, C , and Cole, P. (1965). Some physiological effects of closed circuit halothane anaesthciia. Anaesthesia, 20, 258. Broom, B., and Sellick, B. A. (1965). Controlled hypercapnia in open heart surgery under hypothermia. Lancet, 2, 452.

Frumin, M. J., Epstein, R. M., and Cohen, G. (1959). Apneic oxygenation in man. Anesthesiology, 20, 789. Funderburk, W. H., and Alphin, A. H. (1962). Electrical changes in the central nervous system produced by a new respiratory stimulant, AHR619. Fed. Proc, 21, 324. Gillespie, N. A. (1963). Endotracheal Anesthesia, 3rd ed., ch. 4 and p. 195. Wisconsin: University of Wisconsin Press. Gold, M. I., and Buechel, D. R. (1960). A method of blind nasal intubation for the conscious patient. Anesth. Analg. Curr. Res., 39, 257. Human, J. U. (1941). The Secrets of Blind Nasal Intubation and the Signs of Anaesthesia, 2nd ed., p. 67. London: John Bale. Inkster, J. S. (1963). The induction of anaesthesia in patients likely to vomit with special reference to intestinal obstruction. Brit. J. Anaesth., 35, 160. Lee, J. A. (1964). A Synopsis of Anaesthesia, 5th c d , p. 257. Bristol: John Wright. Macintosh, R. R., and Bannister, F. B. (1952). Essentials of General Anaesthesia, 5th ed., p. 265. Oxford: Blackwell. Magill, I. W. (1928). Endotracheal anaesthesia. Proc. roy. Soc. Med., 22, 1, 83. (1930). Technique in endotracheal anaesthesia. Brit. med. J., 2, 817. (1936). Endotracheal anesthesia. Amer. J. Surg., 34, 450. Noe, F. E. (1966). Respiratory stimulation with doxapram hydrochloride during the anesthesia recovery period. Anesth. Analg. Curr. Res., 45, 479. Borrillo, N., and Greifenstein, F. E. (1965). Use of a new analeptic, doxapram hydrochloride, during general anesthesia and recovery. Anesth. Analg. Curr. Res., 44, 2, 206. Nunn, J. F. (1966). Hypercapnia in clinical anaesthesia. Anaesthesia, 21, 601. Polak, A., and Plum, F. (1963). New respiratory stimulants in barbiturate poisoned animnli; and man, Clin. Res., 11, 90. Price, H. L. (1960). Effects of carbon dioxide on the cardiovascular system. Anesthesiology, 21, 652. Prys-Roberts, C , Smith, W. D . A., and Nunn, J. F. (1967). Accidental severe hypercapnia during anaesthesia. Brit. J. Anaesth., 39, 257. Schultz, E. A., Buckley, J. J., Oswald, A. J., and Van Bergen, F. H. (1960). Profound acidosis in an anesthetised human: report of a case. Anesthesiology, 21, 285. Siker, E. S. (1965). Postanaesthetic respiratory depression. Anesth. Analg. Curr. Res., 44, 253. Musrafa, K., and Wolfson, B. (1964). The analeptic effects of doxapram hydrochloride on thiopentone induced depression. Brit. J. Anaesth., 36, 216. Stephen, C R., and Talton, I. (1964). Investigation of doxapram as a postanesthetic respiratory stimulant. Anesth. Analg. Curr. Res., 43, 6, 628. Ward, J. W., and Franko, B. V. (1962). A new centrally acting agent (AHR619) with marked respiratory stimulating pressor and "awakening" effects. Fed. Proc., 21, 325. Wasserman, A. J., and Richardson, D . W. (1963). Human cardio-pulmonary effects of doxapram, a respiratory stimulant. Clin. Pharmacol. Ther., 4, 321.

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100 patients in the series did bleeding occur of sufficient extent to warrant aspiration. Nevertheless it seemed reasonable to abandon the method after some half-dozen attempts in the absence of strong indications. The number of attempts in each case was also limited by the duration of the respiratory stimulation brought about by doxapram hydrochloride and the desire not to administer a toxic dose. After consideration of the doses given by various authors (Siker, Mustafa and Wolfson, 1964; Stephen and Talton, 1964; Noe, Borrillo and Greifenstein, 1965; Wasserman and Richardson, 1963; Siker, 1965; Noe, 1966), it was thought wise not to exceed 200 mg for an adult. Doxapram hydrochloride usually increased muscle tone and this can be a nuisance if relaxation is required at the beginning of an operation. Such increased tone was quickly overcome by halothane with nitrous oxide and oxygen. Occasionally a pronounced analeptic response occurred which, if accompanied by movements of the head and neck, interfered with intubation. It is possible that this is more likely to occur when too little thiopentone has been given or too long an interval has elapsed between administration of thiopentone and doxapram hydrochloride. No attempt has been made to compare the efficacy of doxapram hydrochloride with that of carbon dioxide, although the degree of success achieved in this series is similar to that mentioned by others (Human, 1941; Gillespie, 1963), and it is suggested that doxapram hydrochloride might be considered a useful alternative to carbon dioxide as an aid to blind nasal intubation. If it can be shown to be less toxic than carbon dioxide it may prove to be a better choice.

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INTUBATION NASALE AVEUGLE SOUS CHLORHYDRATE DE DOXAPRAM

N A S E N B L I N D I N T U B A T I O N U N T E R VERW E N D U N G VON DOXAPRAMHYDROCHLORID ZUSAMMENFASSUNG

SOMMAIKE

BOOK REVIEW Eleciroencephalography for Anesthesiologists and Surgeons. By M. S. Sadove, D. Becka and F. A. Gibbs. Published by Pitman Medical Publishing Co. Ltd., London, and J. B. Lippincott Company, Philadelphia. Pp. 95; indexed; illus. Price 90s. For many years anaesthetists have been aware that the drugs they give to produce unconsciousness can produce profound modifications in the electroencephalogram. The significance of the resulting changes as far as clinical anaesthesia was concerned, however, was by no means clear and indeed the electroencephalographic effects of anaesthetics remained, until recently, something of an academic curiosity, perhaps something which students learned for examinations but with the •conviction, perhaps not fully justified, that what they learned was unlikely to be of any practical importance io them in their work. As far as the changes produced by anaesthetic drugs are concerned the position is substantially the same. The introduction of surgical procedures which tended to interfere with cerebral blood flow, however, stimulated a new interest in this subject and though the advantages of electroencephalographic monitoring of patients undergoing cardiac surgery has not entirely fulfilled its initial expectations, it has become realized that in this field the electroencephalograph has something to offer and can indeed provide information which is not readily obtained by any other form of monitoring. It is therefore appropriate that a book on the subject should be published. The present volume is in fact the product of the work of three people, an anaesthetist, a supervisor and instructor in a department of encephalography, and a professor of neurology whose work on the electroencephalogram in other fields is widely known. As would be expected, the book covers the electroencephalographic changes produced by most anaesthetic drugs. This material is presented in the form of a series of tracings. The shape of the leaves of the book, too, is devised so that these records lie open for inspection

just as do the records obtained directly from the machine itself. It is true that there has been a moderate degree of scaling down but this should not trouble even those who are in the habit of reading electroencephalograms for themselves. The place of the electroencephalogram in cardiac arrest and vascular insufficiency is also discussed at length with the aid of large numbers of tracings. The only omission of any note here is the absence of any records made in patients in whom hypotension was induced deliberately as part of general anaesthesia, but it may well be that the workers who produced this volume did not have access to such cases, though they comment on its usefulness under these circumstances. For comparison the electroencephalograms of normal sleep and those of the various forms of epilepsy are also presented. A most useful feature of the book is the first section, which will be invauable to anyone who wishes to start using this form of patient monitoring. For here they will find full details of how to set about obtaining the necessary apparatus, installing it and running it. Equally the last chapter, concerned with extraneous potentials and artefacts, must be of tremendous value to those whose knowledge of the subject is relatively elementary. The book concludes with a list of references and an index. The numerous electroencephalographic tracings are not numbered, but the pages which contain them occupy more than half of the text. As would be expected from an experienced worker like Dr. Gibbs, tracings from leads from all parts of the brain are included in these records. In general this is a most valuable introduction to the use of the electroencephalogram by anaesthetists in the operating theatre, in the recovery room and Intensive Care Unit. There certainly should be a copy of it everywhere, particularly everywhere where cardiac patients are being looked after in the postoperative phase, and every departmental library should obtain a copy of it.

A. R. Humer

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On decrit vine technique d'intubation nasale aveuglc sous legere anesthesie generate, avec un stimulant de la respiration, chlorhydrate de doxapram. L'intubation reussissait chez 88 des 100 patients avec pas plus que 200 mg de chlorhydrate de doxapram. On suggere que ce medicament pourrait constituer une alternative utile pour Panhydride carbonique dans l'intubation nasale aveugle.

Es wird ein Verfahren beschrieben, bei dem unter leichter Allgemeinnarkose und unter Verwendung von Doxapramhydrochlorid, eines die Atmung anregenden Mittels, ohne Sicht cine Intubation durch die Nase vorgenommen wurde. Die Intubation wurde bei achtundachtzig von hundert Patienten mit weniger als 200 mg Doxapramhydrochlorid erfolgreich durchgefuhrt. Es wird die Ansicht vertreten, dafi Doxapramhydrochlorid bei der Nasenblindintubation moglicherweise eine brauchbare Alternative fur Kohlendioxyd darstellt.