The oculorespiratory reflex revisited

Transcription

1 468 Vctor Fara Blanc FRCPC, Jean-Lous Jacob ~tcsc, Jean Mlot FRCSC, Louse Cyrenne FRCr'C The oculorespratory reflex revsted Contnuous measurement of the ntratraeheal pressure and capnography are very smple and accessble methods for the detecton and recordng of the oculorespratory reflex (ORR). Eght healthy chldren (fve to 14 years old) undergong strab~raus surgery under haothane-ntrous oxde anaesthesa wth spontaneous ventlaton were studed. The ORR was evoked by tracton on the extrnsc muscles of the eye (four medal rect and four lateral rect). Slowng of the respratory rate andlor shallow respratory movements were observed n each patent. One patem developed apnoea of 20 seconds duraton whch forced the use of manually controlled ventlaton. ntravenous atropne t to.ol r ) reduced the ncdence of postve OCR (to 37.5 per cent) but dd not dmnsh the ncdence of the ORR ro0 per cent). Snce the ORR may lead to hypercapna and hypoxaemfa, controlled ventlaton s recommended for patents undergong strabsmus surgery at least mmedately before and durng the muscular tracton. t s now clear that the ORR may be evoked by tracton on the extrnsc muscles of the eye, may produce hypercapna and hypoxaema and so, may aggravate the consequences of the OCR. Key words aeflexf..s: oculorespratory reflex, oculocardac reflex; SURGERY', suabsmus; ANAESTHESA: paedatrc; antcholnergc, antmuscarnc drugs; hypercapna, hypoxaema. PARASYMPAT-ETC NERVOUS SYSTEM: RESPRATON'. From the Departments of Anaesthesa and Ophthalmology (J-.J, JM), H6ptal Sante-Justne and Unve~t~ de Montrtal, Montr(~al, Quebec. Address correspondence to: Vctor Fara Blanc MD, Department of Anaesthesa, Hgptal Sante-Justne, 3175 Chemn C6te Ste-Catherne, Montrtal, Qutbec, H3T 1C5. The oculorespratory reflex (ORR) was frst descrbed by Aschner (1908) n the rabbt submtted to bulbar pressure. 1 n , Petzetaks descrbed the ORR evoked by pressure on the eyes of humans. 2'3 The clncal manfestatons of the ORR nclude bradypnoea, expratory gasp or nspratory pauses, shallow respratory movements and respratory arrest.)-~ The ORR and the oculgcardac reflex (OCR) are separate but ntmately assocated reflexes, The afferent arc of each s dentcal, 1'7-9 whle the efferent are s clearly dfferent. n fact, Petzetaks reported that atropne abolshes the OCR wthout changng the ncdence of the ORR; 2 and Detava, s lke Joffe and Gay, t~ reported that, n the dog, ntravenous atropne enhances the ORR. These phamlacologcal dfferences observed wth ntravenous atropne strongly suggest that the ORR s ndependent of the vagus nerve_ Delays demonstrated, n the dog, that blateral vagotomy and secton of the spnal cord at the level of the seventh cervcal vertebra (phrenc nerves ntact) does not abolsh the ORR. s Whle the efferent pathway for the ORR s not clearly elucdated, t seems reasonable to postulate that the afferent mpulses reachng the man sensory nucleus of the trgcmna] nerve stmulate fbers whch reach the pneumotaxc respratory centre n the ventrolateral tegmentum of the pons. Sgnals sent from ths area to the medullary respratory area (nspratory and expratory centres) would result n nspratory nhbton an&'or expratory facltaton, through the phrenc and other respratory nerves, whch lead to bradypnoea, rregular respratory movemenls and, fnally, to respratory arrest. No menton s made of the ORR n current textbooks of anaesthesa. The followng study ntroduces two smple methods for the detecton and recordng of the ORR. t s centred around two basc questons: (a?) s t possble to elct the ORR hy tracton on the extrnsc muscles of the eye? (b) How mportant may the ORR be n patents undergong squnt correcton? Methods Eght chldren (four males and four females) fve to 14 years of age and ASA physcal status, requrng correcton of strabsmus under general anaesthesa, were studed after nformed consent was obtaned from the CAN! ANAEST-[ 1988 r 35:5 / pp468-72

2 Blanc el al.: THE OCULORESPRATORY REFLEX 469 mmhg 0 = HEART RATE TRACTrON ~0 sec. FGURE 1 A postve ORR (slowng of:he respratory rule and shallow ret, platoly movements n the tracheal pressure tracng) and negatve OCR (no ssnfcant change n the heart rate), durng and after tracton o~ the left lateral rectus of a fve-yem--old boy. parents. The protocol for ths study was approved by the Commttee on Medcal Ethcs of the HOptal Sante- Justne. Every chld had the followng montorng: precordal stethoscope, contnuous ECG (CM-5), regular blood pressure measurements wth a Dnamap (Vtal Sgns Montor - Model 1846) and rectal thermometry. No premedtaton was gven. nducton was acheved wth halothane, ntrous oxde and oxygen (40 per cent) by mask. ntravenous atropne (0.01 mg'kg -~) was then gven. When the tachycarda was establshed, tracheal ntubaton was performed, wthout the use of muscle relaxants, under deep halothane-oxygen anaesthesa. After ntubaton, anaesthesa was mantaned wth halothane (1.5 per cent), ntrous oxde and oxygen (40 per cent), usng a Bath crcut wth a fresh gas flow not less than 260 ml. kg -t, wth spontaneous breathng, n sx of the chldren. n the two remanng patents an Oho crcle system wth carbon doxde absorpton replaced the Ban crcut, n order to obtan capnographc tracngs. ncson of the conjunctva was done nasally or temporally by a fornx approach accordng to the muscle to be operated upon, wth mnmal moblzaton of the globe n order not to elct the ORR and/or the OCR. Secondly, a muscle hook was gently engaged under the muscle tendon. The dssecton was kept mnmal, thus avodng tracton on the muscle to be studed. Usng a four channel Gould recorder, we obtaned a contnuous and smultaneous recordng of the heart rate (Gould ECG Rate Amplfer - Model t X), of the ntratraeheal pressure (P23 Gould Statharn Pressure Transducer), and of the muscular tracton duraton (Gould Tme Marker), n each patent. n two chldren, the expred carbon doxde (PECO2) was also recorded, usng an Oho crcle system wth CO2 absorpton and a Semens (Srecust 322) capnograph. Twenty to 25 mnutes after ntravenous atropne and tracheal ntubaton, when the heart and respratory rates were stable, a square wave stmulus of g, lastng seconds, was appled to the extraocular muscle to be studed, The ORR was defned as a fall n respratory rate of ten per cent or more (n the tracheal pressure and r c traces) and/or the development of shallow respratory movements (n the tracheal pressure tracng). The OCR was consdered to have occurred when the heart rate slowed at least 12 beats-ran -] (3 mm downward deflecton n the heart rate tracng). Results The extraoeular tracton nvarably produced slowng of the respratory rate, even when the heart rate remaned stable. As soon as an extraocular muscle was stmulated the respratory paltem changed, lnspratory pauses, slowng of the respratory rate and/or shallow respratory movements, were constantly observed (Fgures and 2). Moreover, n the two patents studed wth capnography the PECO2 rased from a mean value of 41 mmhg (5.453 kpa) to a mean value of 47 mmhg (6.251 kpa). Slowng of the respratory rate, shallow respratory movements and elevated PECO-, perssted for seconds after releasng the muscular tracton (Fgures 1 and 2). n one patent (14 year old female), respratory arrest occurred 12.5 seconds after the release of the extraocular muscle tracton (rght medal rectus) and forced the ntaton of manually controlled ventlaton, after 20 seconds of persstent apnnea (Fgure 3). No measurable varaton occurred n the capnographe

3 470 CANADAN JOURNAL OF ANAESTHESA PE CO2 mmhg 40 2 TRACHEAL PRESSURE mm Hg HEART RATE " O 1! TRACTON FGURE 2 Note slowng of the respratory rate wth nspratory pauses (PECOz and racheal pressure tracngs), hypercapnn (from 42 to 48 mmhg - l~co2 tracng) alld postve OCR (bradycarda, n the heart rate b-acng), as soon as the muscular tracton s started. Obtaned from the [el! medal rectus of an eght-year-old grl. and tracheal pressure traces n the control perod, whle clear varatons were noted durng and after the muscular stmulaton. Ths allows concluson that the varatons, ncludng the rse n end-tdal CO2, were real and not concdental. ntravenous atropne (0.01 mg-kg -J) prevented the OCR n 62.5 per cent of our patents but dd not abolsh the ORR whch was evdent n each ease_ Dscusson The present study clearly proves that the ORR can also be evoked by extraocular muscle tracton. Usng hghly reflexogene stmul (square wave tractons of g lastng seconds), we observed 100 per cent of postve ORR versus 37.5 per cent of postve OCR, despte the fact that each patent had receved ntravenous atropne (0.01 mg.kg -t) 20 to 25 mnutes before the muscular stmulaton. n fact, t has been reported that atropne does not prevent the ORR elcted by pressure on the eyeballs of human bengs 2 and rather enhances the ORR evoked by bulbar pressure n the dog. s't~ The present study was not desgned to determne the sgnfcance of the type of stmulus n the ncdence of the ORR. We used hghly refexogenc stmul (type A or square wave stmul) N because we wanted to know f the ORR may he evoked by tracton on the extrnsc muscles of the eye. As we know that the type of stmulus s a determnant factor n the ncdence of the OCR ~ t seemed reasonable to postulate that ths should he true for any other mechancally evoked reflex. Several years of systematc clncal observaton permt to conclude that surgeons not aware of the mportance of the stmulus do use hghly reflexogenc muscular tractons and get a hgh ncdence of postve OCR. On the contrary, surgeons who practse very gradual and gentle manpulaton of the extraocular muscles have a very low ncdence of postve OCR. Our results show that the ORR s a frequent and potentally dangerous occurrence durng strabsmus surgery when hghly reflexogenc stmul are used. Ths reflex, not abolshed by ntravenous atropne, may lead to bradypnoea wth hypercapna (Fgure 2) and may culmnate n apnoea wth consequent hypoxaema (Fgure 3). Although others, usng very dfferent methods, wth undefned stmul, have concluded that the use of controlled ventlaton does not reduce the ncdence of the

4 Blanc oral: THE OCULORESPRATORY REFLEX 471 TRACHEAL PRESSURE 0 - mmhg tracton, wat for normal heart rate, then contnue the operaton wth gentler manpulaton HEART ~20 RATE BO l 4 l f J f Acknowledgements We thank all the members of the Department of Bomedcal Engneerng of the Hfptal Sante-Justne for ther nvaluable assstance. Also, we extend a note of apprecaton to the nurses of the operatng room, to the anaesthetc and nhalotherapy staff, who devotedly asssted us, 0 see. FGURE 3 Bradypnoea and rregular respratory movements followed b~, apnoea (postve ORR - tracheal pressure tracng) and slow to recover bradycarda (postve OCR - heart rule tracng), alter tracton on the rght medal rectus ~f a 14-year-old grl. OCR, n'13 we conclude that controlled ventlatotl must be preferred to spontaneous breathng, at least mmedately before and durng the muscular tracton. One addtona/queston remans unanswered: how can we explan the scarceness of nformaton concernng the ORR n anaesthesology and n ophthalmology'.j s t due to the fact that, fnally, most of the patents undergong squnt correcton are anaesthetzed wth asssted or controlled ventlaton? s t due to the "reflex of automatcally baggng the patent" when somethng s wrong? We do not know, As we stressed prevously,~ ~ the type of stmulus beng the determnant factor of the OCR, mnmal, very gradual and gentle manpulaton of the extraocular muscles s requred to dmnsh the ncdence or the ntensty of the OCR and the occurrence of cardac arrhythmas. Well managed anaesthesa s equally mportant. Controlled ventlaton must be preferred to spontaneous ventlaton, at least mmedately before and durng the muscular tracton. Hypereapna does augment the ncdence of the OCR n spontaneously breathng nfants and chldren l and hypoxaema must be prevented when facng the possblty of cardac arrhythmas. These ventlatory abnomlaltes may be due to, or aggravated by an ORR. ntravenous antmusearnes effectvely reduce the ncdence of bradycarda and of bradyarrhythmas, durng strabsmus surgery and, consequently, are ndcated. But we have to remember that these drugs do not abolsh the ORR and so, do not elmnate the need for vcntlatory control. Perfect co-operaton between the surgeon and the anaesthetst s mandatory. Both must realze the mportance of the dfferent factors causng or favourng the OCR and the ORR. t" the OCR s elcted, the surgeon must release the References 1 Aschner B. 0bur enen bsher noch ncht beschrebenen Reflex yon Auge anf Kreslauf and Atmung: Verschnden des Radalspalses be Druk auf das Auge. Wen Kln Wschr 1908; PetzetaMstk r R~flexe oculo-respratore el r~flexe ocnovaso-moteur b_ l'&at normal. Bull Soc M~d Hfp Pars 1914, 37: Petzetaks M. Effets ~flexes de la compresson oculare l'~tat normal. R~flexes: ccalo-cardaque, oculo-respratore, oculo-vasomoteur. J s Pars 1915; 16: Salamagne JC, Lc rfflcxe oculo-cardaque - L'anesrh~sc en Ophtalmologe - XXV Congr~s Natonal d'anesthfse et de R~atfmaton, Bordeaux, France, pp (1979). 5 Detava P. ~tude des offers de la compresson ocu/are sur la crculaton et ]a respraton. Roy Belg Cln Sc 1914; Foster CS, Brennan L. The oculocardac reflex and the oculorespratory reflex. J Am Nurse Anesth 1974; 42: GayAJ, Joffe WS, Barnet R. The afferent course of the oculorespratory reflex of the thrd, fourth and sxth cranal nerves. nvest Ophlhal 1964; 3: Joffe WS, Gay A J, Antrm CC. Trgemnal pathway for afferent fbers from the oculomotor nerves. nvest Ophtha 1966; 5: P~ntnen P J. The mportance of the oeuloeardae reflex durng ocular surgery. Acta Ophthal Suppl 1966; 86: Joffe WS, Gay AJ. The uculorespratory reflex n the dog. nvest Ophthal 1966; 5: Blanc VF, Hardy JF, Mlot J, Jacob JL. The oculocardac reflex: a graphc and statstcal analyss n nfants and chldren. Can Anaesth Sue J 1983; 30: ForestnertE, mbreeht P. Controlled respraton does not nhbt oculocardac reflex durng strabsmus surgery n chldren. Anesthesology 1983; 59: A Mrakhur RK, Shepherd WF, Jones CJ. Ventlaton and the oeulocardae reflex. Preventon of nculocardac reflex durng surgery for squnts: role of controlled ventlaton and antcholnergc drugs. Anaesthesa 1986; 41:

5 472 CANADAN JOURNAL OF ANAESTHESA R6sum6 Cette dtude a ~t~ con~ue afn de savor sle rdflexe oculorespratore (ROR) pout ~tre d~clench~ par l' dtrement des muscutes extrns~ques de l'oel et ans pouvor prsumer de son mportance face au r~flexe oculocardaque (ROC) tars des correctons de strabsme. L'enregstrement graphque de la presson ntratrachdale et la capnographe se sont av#r~es des m~thodes slmples et fables pour la d~tecton et pour 1' ~tude du ROR. Hut enfants (de cnq d t4 ans; ~tat physque de la classfcaton ASA) operas pour des correctons de strabsme, anesth~sds l'halothane el au protoxyde d' azote, en respraton spontan,~e, farent dtud~s. Nous a vans employg des tractons musculares de grammes durant secondes. Malgrd l'empto d'atropne par voe ntraveneuse (O.Ol mg.kg ), te ROR (bradypnde, arythme respratare) a ~td postf dans 100 pour cent des cas, alors que le ROC n'a 6t~ postf que dons37,5 pour cent des cos. Un enfant (llle de 14 ans ) a pr~sent~ one apn~e de 20 seeondes, apr~s la stmulaton de son drot nterne. En concluson, le RORest une enftd assez fr~quente, lots des correctons de strabsme, pouvant amener de t'hypercapne et de l'hypoxe et, par consequent, pouvant aggraver le ROCet facfter l'apparton d'arythmes cardaques, x: ventlaton contrdlde est donc d recommander lots des correctons de strabsme, au mans mm~datement avam et pendant los tractons musculares.