219 Reflex bradycardia D. John Doyle MD PhD FRCPC, Patrick W.S. Mark during surgery Reflex bradycardia and sinus arrest may occur in a variety of fentanyl, and succinylcholine may facilitate the reflex. surgical procedures, from neurosurgery to general abdominal, Since the reflex is vagally-mediated, premedication with laparoscopic, opthalmic and facial surgery and even proce- an anti-cholinergic (e.g., atropine or glycopyrrolate) may dures such as liver biopsies and electroconvulsive therapy, in be a suitable preventative measure. most cases a vagally-mediated reflex has been implicated, although experimental support for this is often lacking. Drugs Reflex bradycardia during abdominal surgery such as vecuronium, atracurium, halothane, fentanyl and A decrease in arterial blood pressure and a change in heart succinylcholine may predispose to this reflex. Premedication rate may occur with surgical manipulation of abdominal with an anticholinergic is usually effective in preventing its contents. Rocco and Vandam ~ found that some patients occurrence. exhibited a fall in blood pressure of about 20 mmHg systolic and 6 mmHg diastolic over a period of 8 to 15 Une bradycardie rdflexe et/ou un arr~t sinusal peuvent survenir pulse beats immediately after manipulation of the upper lors de tout un dventail d' interventions aUant de la neurochirur- abdominal anterior parietal peritoneum. The effect was gie d la chirurgie abdominale, laparoscopique, ophtalmique et transient even if the initial stimulus was continued. A faciale en passant par la biopsie du foie et les dlectrochocs. similar reflex of greater magnitude and longer duration Malgr~ I'absence de confirmation expdrimentale solide, on a was noted with displacement of the liver, insertion of the souvent insistd sur le rrle du nerf vague dans ce r~flexe. On salt hand into the peritoneal cavity, placement of packing, qu'entre autres, le vdcuronium, l'atracurium, l'halothane, le evisceration, or retraction of the wound edges. Rocco and fentanyl et la succinylcholine peuvent en favoriser l'apparition, Vandam explained these findings in terms of tissue alors qu'un anticholinergique en pr~m~dication pourra habi- deformation, resulting in an increase in vagal tone and a tuellement le prdvenir. consequent decrease in cardiac contractility and output. A simultaneous bradycardia was present in nearly half the patients. Any sudden change in the cardiovascular state of a patient Smith 2 attributed some sudden decreases in blood during anaesthesia is potentially dangerous, especially pressure during abdominal surgery to a coeliac plexus when its cause is obscure. Presented here is a summary of reflex. He stated that stimulation of the coeliac plexus some reported instances of changes in heart rate and blood (e.g., through handling of upper abdominal viscera) pressure which have been attributed to a vagal reflex. This caused a reflex decrease in cardiac output due to increased phenomenon has been observed during a wide range of vagal tone. The accompanying decrease in heart rate was procedures, from neurosurgery to general abdominal, only minor, apparently due to the compensatory effects of laparoscopic, ophthalmic, and facial surgery. In addition, the Bainbridge reflex (an increase in heart rate resulting it has also been observed during laryngoscopy, percutane- from an increase in the pressure within the large veins or ous liver biopsy, and electroconvulsive therapy (vide the right atrium). 3 infra). Drugs such as vecuronium, atracurium, halothane, More recently, Seltzer et al. 4 observed that traction on the abdominal mesentery resulted in a decrease (20 Key words mmHg on average) in mean arterial pressure, which was COMPLICATIONS: arrest, cardiac, arrhythmia; attributed to vasodilatation, manifested as a decrease in HEART: arrhythmia, bradycardia, sinus arrest; systemic vascular resistance, as measured using invasive PARASYMPATHETIC NERVOUS SYSTEM: vagus; haemodynamic monitoring. This was often accompanied REFLEXES: vagal. by an increased heart rate, although instances of bradycar- dia also occurred. From the Department of Anaesthesia, Toronto General Hospital. Bradycardia and hypotension after percutaneous Address for correspondence to: Dr. D.J. Doyle, Department liver biopsy of Anaesthesia, Toronto General Hospital, 200 Elizabeth Sullivan and Watson s described three patients who Street, Toronto, Ontario, M5G 2C4. developed transient hypotension and bradycardia imme- CAN J ANAESTH 1990! 37:2 /pp219-22 220 CANADIAN JOURNAL OF ANAESTHESIA diately after percutaneous liver biopsy. This was attribut- was administered. A similar case was described by Doyle ed to stimulation of the hepatic and coeliac plexuses and and Mark. is These events were attributed to parasympa- the splanchnic and vagal nerves. However, Barrett6 thetic stimulation from both peritoneal stretching and suggested that stimulation of the tissue between the liver cervical dilatation. and the diaphragm might also be responsible. Doyle and Mark ~8 noted that when drugs with vagolytic or sympathomimetic effects, such as pancuronium, are Bradycardia due to the oculocardiac reflex used, this reflex is often masked. However, if drugs free Bradycardia upon traction of the orbit has been docu- of cardiovascular effects, such as vecuronium, are used, mented since the early 1900's 7,s and involves a reflex arc; the reflex is not masked unless an anticholinergic is also the afferent arm is via parasympathetic fibres in the ciliary administered. In all four of the above cases, the neuro- nerves and the ophthalmic nerve from the Gasserian muscular blocking drug used was vecuronium. How- ganglion. 9 These fibres run to the spinal tract of the ever, the peculiarity in Clayton's case ~7 is that even trigeminal nerve. The adjacent nucleus ambiguus is the though hyoscine had been given preoperatively, brady- origin of the vagus, which forms the efferent arm of the cardia was still noted. This is in contradistinction with the reflex. Many related phenomena have been observed. studies of Caldwell et al. 19 in which 52 patients undergo- Robideaux I~ described a case in which an attempt at ing laparoscopic sterilization were given IV vecuronium disimpaction of a fractured maxilla resulted in abrupt and IM hyoscine and developed tachycardia during the bradycardia which promptly subsided upon cessation of operation. traction. This was attributed to stimulation of terminal branches of the trigeminal nerve through traction on the Bradycardia during laryngoscopy floor and medial aspect of the orbit. In a similar case, Podolakin and Wells 24 described three patients, each with Shearer and Wenstone t ~reported incidents of bradycardia a history of cardiac disease, who developed severe in two patients undergoing procedures to elevate fractured bradycardia at the beginning of surgery just after laryn- zygomas. The explanation offered for this observation goscopy and spraying of the cords with lidocaine. This was the inadvertent stimulation of parasympathetic fibres response was believed to have been caused by reflex vagal in the periosteum of the zygoma. In another case, Kerr activity from stimulation of the larynx with insufficient and Vance 12 observed a profound bradycardia resulting fentanyl anaesthesia. After increasing the induction dose from an oculocardiac reflex in two patients with previous of fentanyl, Podolakin and Wells did not encounter any orbital enucleations. It was speculated that regeneration further cases of this reflex. The exact pathway of this of the severed axons from the Gasserian ganglion allowed reflex is not known but the fibres of the superior laryngeal the reflex to occur in spite of an empty orbit. Finally, the nerve have been ruled out by the work of Jacobs et al. 25 observation of Hopkins 13 that severe bradycardia resulted using nerve stimulation experiments in a rat model. upon diathermy in the vicinity of the tentorium is ex- Bradycardia associated with electroconvulsive plained because the ophthalmic nerve sends branches to therapy the tentorium cerebelli. There have been many reports of bradycardia during Because of the severity of the cardiovascular effects electroconvulsive therapy (ECT). Marks 26 noticed that resulting from this relatively common reflex (Mirakhur et parasympathetic discharge occurred immediately after the al. ~4 found that 90 per cent of patients in their study current is applied and resulted in severe bradycardia and exhibited the reflex), the possibility of reflex bradycardia hypotension. This was supported by Anton et al. 27 who should always be noted when operating near the ophthal- studied the effects of ECT in dogs. Although atropine has mic nerve. been used routinely prior to the procedure, its use is now being questioned since some (Wyant28) have found it to Bradycardia associated with laparoscopy and D&C contribute nothing to patient safety and may be harmful Instances of bradycardia not unlike those reported during because of cardiac sphincter relaxation during convulsive abdominal surgery have been recorded during certain movements which increases the likelihood of regurgita- gynaecological procedures. Milligan and Beers~5 encoun- tion. tered a patient undergoing a gynaecological laparotomy who developed 5:1 heart block and eventually asystole Psychogenic cardiac arrest immediately after opening the peritoneum. Kirkwood and Frerichs et al. 29 reported an unsedated patient who Duckworth 16 reported a similar incident in which a patient underwent arthroscopic examination of a knee with