511 Bradycardia during cold ocular irrigation under general anaesthesia: an example George A. Arndt MD,* M. Christine Stock MD~ of the diving reflex A case of bradycardia is reported which was precipitated by Case report cold normal saline applied to the eye during general anaesthesia. A 60-yr-old woman was scheduled for left scleral buckle. The history and physiology of the diving reflex is discussed Her past medical history was unremarkable, with no his- and we believe that these data suggest that this patient's brady- tory of cardiovascular, neurological, renal, haematopoetic, cardia was induced by the diving reflex, and not by the oculo- endocrinological, or pulmonary disease. She did not cardiac reflex. smoke or use alcohol or take medications. Previously she had undergone two gynaecological operations during un- Nous rapportons un cas bradycardie provoquOe par l'application complicated general anaesthesia. Physical examination oculaire de solut~ physiologique froid. La discussion porte sur was normal and there was no syncopal history. The I'histoire et la physiologie du r~flexe de plongke. Nous croyons preoperative laboratory results were normal, with hae- que ces donn~es supportent notre hypoth~se d'un bradycardie moglobin and haematocrit 13.7 gin. dl -I and 39.7%, re- provoqu~e par le r~flexe de plong~e et non par le rdflexe oculo- spectively. The preoperative 12-lead electrocardiograph cardiaque. (ECG) showed normal sinus rhythm with no suggestion of ischaemia. The vital signs the day before surgery were blood pressure 140/80 mmHg, pulse 88 beats, min -I and The oculocardiac reflex, well-described in the anaesthesia respirations 18 breaths, min -x. She weighed 55.7 kg and literature, results from a variety of stimuli including trac- was 155 cm tall. Sixty minutes before her operation, the tion on the extraocular muscles, ocular manipulation, patient received diazepam I0 mg po, and a peripheral pressure or traction on the globe, or pressure applied to /v infusion of lactated Ringer's solution with 5% dextrose. an empty orbit. I-5 However, even in the absence of these Intraoperative monitoring included a fivedead contin- stimuli, cold ocular irrigation may elicit bradycardia in- uous ECG which displayed limb lead II. After preoxy- duced by the diving reflex. The oculocardiac reflex is genation, anaesthesia was induced with thiopentone 275 active in awake and anaesthetized subjects and is man- mg and lidocaine 100 mg /v. Tracheal intubation was ifested by a variety of dysrhythmias, which include bra- facilitated with succinylcholine 80 mg/v, and was easily dycardia, bigeminy, ectopic beats, nodal rhythm, and as- accomplished. Anaesthesia was maintained with 1% iso- ystole. 6-8 The diving reflex may have similar physiological flurane and 50% nitrous oxide in oxygen. Ventilation was mechanisms and clinical significance. controlled so that end-tidal carbon dioxide concentration was 36 mmHg. Relaxation was maintained with 5 mg /v vecuronium bromide. Vital signs did not vary by more Key words than 5% during anaesthetic induction and maintenance HEART: alThythmia; up to this point. BRADYCARDIA:diving reflex. Fifteen minutes after induction, a watertight drape was From the Departments of Anesthesiology,University of placed around the left eye and the surgeon began to ir- Wisconsin Clinical Science Center,* Madison, Wisconsin and rigate the eye liberally with sterile, room-temperature, Emory UniversitySchool of Medicine,l"Atlanta, Georgia. normal saline. The temperature of the saline was 19.7~ Address correspondence to: Dr. George A. Arndt, The heart rate promptly decreased from 78 beats, min -1 Department of Anesthesiology,University of Wisconsin with normal sinus rhythm to a sinus bradycardia of 30 Clinical Science Center, B6/387 CSC, 600 Highland Avenue, beats, min-l. The surgeon stopped the irrigation and at- Madison, WI 53792. ropine 0.4 mg was given/v. The heart rate increased to Acceptedfor publication 22nd February, 1993. 90 beats- min -I with normal sinus rhythm. The episode CAN J ANAESTH 1993 / 40:6 / pp511-4 512 CANADIAN JOURNAL OF ANAESTHESIA of bradycardia was short-lived (lasting approximately 20 Richet. The diving reflex is present in man, seals, and sec), and quickly returned to an acceptable rate with at- dogs. It is a highly integrated reflex consisting of initiating ropine administration and cessation of irrigation. During events which temporally summate to protect against as- the episode, no ocular stimulus was present other than phyxiation under water. 10,16.tS Clinically, the reflex has application of cold saline; the surgeon had placed no re- been induced using ice water. However, in man, the reflex tractors, instruments, retracted the eye muscles or placed is also initiated by facial application of 0-20 ~ C cold sa- pressure on the eye. Pulse oximetry revealed that the line. t9 In our patient, the temperature was 19.7~ and patient was not hypoxic during the episode, neither did fell within the 15-20~ range, the most frequently studied she become hypotensive, the blood pressure remaining temperature range. 2~ Further general anaesthesia does at 110/80 as measured by auscultation before, during and not abolish the reflex in dogs and seals, 22 but im or/v after the episode. After the heart rate stabilized, the sur- anticholinergic agents may block or antagonize the re- geon proceeded cautiously with ocular irrigation which flex. 9 In seals, and perhaps in man, afferent information caused no further change in vital signs. We were unable from the carotid body and sinus, mediated by the glos- to record a rhythm strip during the episode. The drape sopharyngeal nerve, is important in sustaining the later was found to form a watertight seal, preventing the ir- portions of the reflex which includes vasoconstriction and rigation solution escaping from the field. apnea. 22,23 The remainder of anaesthesia was uneventful. The vital Both the parasympathetic and sympathetic nervous signs remained stable. At the end of the procedure muscle systems are integral parts of the diving reflex. In dogs, relaxation was reversed with glycopyrrolate and neostig- bradycardia results from increased vagal tone, 24,~ as the mine with no change in heart rate. Emergence was un- reflex is abolished with atropine. The sympathetic nerv- complicated and the tracheal tube was removed when ous system causes intense peripheral vasoconstriction the patient opened her eye. She was transferred to the which diverts blood flow from nonvital organs and main- recovery room and discharged when alert and awake. tains cardiac output, blood pressure and venous tone. 23,24 The postoperative visit the next day was unremarkable Blood flow to the kidneys, muscles, and gut is minimized. except for a mild sore throat. Cardiac blood flow and cardiac output may decrease by 90% but the reflex protects blood flow to the heart, lungs, Discussion and brain. 26 The diving reflex begins when temperature This case is an example of the diving reflex in an adult receptors in the ophthalmic division of cranial nerve five during general anaesthesia. Classically the diving reflex are excited by cold water. 26 The sensory information pro- is described as bradycardia without hypotension during ceeds to the sensory nucleus of the fifth cranial nerve the application of cold irrigants to the distribution of the and then to the vagal motor nucleus. 26 Fifth cranial nerve ophthalmic division of the fifth cranial nerve. Bradycardia sensory input also enters the brainstem cardioinhibitory is mediated by the vagus nerve. 9,1~ This reflex appears centre and mediates the sympathetic response. 26 The to be more prominent in children than in adults and has vagal motor nucleus and the cardioinhibitory centre also been used in both awake adults and children to treat communicate with the respiratory centre. 26 This produces refractory supraventricular tachycardia. "-~4 It is a primal a more intense reflex during exhalation. Jg,2s Only the reflex and appears to be present in most vertebrates. It brain maintains a normal or increased blood supply. 9,27 is more potent than a Valsalva manoeuvre, carotid mas- The diving reflex may have clinical importance. Death sage or ocular compression in inducing vagally mediated from arrhythmias due to the oculocardiac reflex are well bradycardia. J5 known. 6 The diving reflex is mediated by similar reflex The diving reflex was fast described by Bert in 1879 arcs. In awake humans, the diving reflex appears to be while investigating duck asphyxiation. He found that more intense than the oculocardiac reflex, t5,2~ Bradycar- water applied to the ducks' eyes and nostrils produced dia during the diving reflex is more profound than the bradycardia, and ducks tolerated underwater asphyxia- maximal bradycardia of the oculocardiac reflex, t5.21 The tion longer than chickens. 5,t7 In 1894, Richet concluded diving reflex also involves intense sympathetic nervous that the duck's ability to tolerate long periods underwater system activity altering myocardial repolarization as ev- was a reflex physiological adaptation, conserving avail- idenced by T-wave and ST segment changes. 29 The com- able oxygen stores and allowing the animal to tolerate bination of slowed myocardial conduction, altered ven- long periods without oxygen. He speculated that blood tricular repolarization, and the propensity of the was preferentially shunted to more oxygen-dependent or- oculocardiac reflex to produce life-threatening arrhyth- gans. 16 mias implies that the diving reflex also may precipitate The diving reflex was characterized in diving and non- a potentially dangerous situation. 29,3~ The risk may be diving animals years after the initial work of Bert and compounded in the elderly ophthalmology patient with Amdt and Stock: DIVING REFLEX 513 multiple medical problems. In experienced pearl divers, 2 Aplvor D, Ravi PK. Ketamine and the oculocardiac re- two cases of idioventricular rhythms and other dysrhyth- flex. Anaesthesia 1976; 31: 18-22. mias during routine dives were attributed to the diving 3 Blanc VE Hardy J, Milot J, Jacob J.