Sensitivity to vasovagal maneuvers in normal children and adults

The Oculocardiac Reflex: A Review

BACKGROUND

A typical oculocardiac reflex (OCR) is a moderate trigemino-vagal bradycardia elicited by tension on an extraocular muscle (EOM) during strabismus surgery; however, many other orbital stimuli can elicit cardiac slowing including retinopathy of prematurity examination.

METHODS

World literature related to trigeminovagal and oculocardiac reflex covering over 15,000 patients including 51 randomized clinical trials and case reports are analyzed and reviewed. Under an ongoing observational trial in Alaska, anesthetic, patient and surgical influences on routine strabismus surgery using prospective, uniform EOM tension are compared seeking sufficient sample size to characterize this individually widely variable cardiac response.

RESULTS

With adequate sample size, and emphasizing clinical studies controlling type of EOM, muscle tension amount and duration, anticholinergic and opioid medications, the following augment OCR; rapid-acting opioids and dexmedetomidine while OCR is reduced in older patients, the right eye, less EOM tension, deeper inhaled agents, hypocarbia, anticholinergic medications and orbital block. In re-operations, the former are relatively poor predictors of subsequent OCR.

CONCLUSION

Profound bradycardia can occur in almost 10% of strabismus surgery cases without anticholinergic preventive measures, but reliable prediction of OCR remains elusive. With foreknowledge and careful anesthetic monitoring of the patient before EOM manipulation, residual adverse sequelae from OCR are fortunately very rare. Despite well over a century of experience, the teleology for this occasionally dramatic cardiac response to eye surgery is still not known.

Sudden death during physical restraint by the Dutch police

BACKGROUND

and goal: The Police is sometimes confronted with the death of a subject during physical restraint. In most of these cases a clear Cause of Death (COD) cannot be determined by the Pathologist. The goal of this research is to find and clarify a pattern and pinpoint a clearer COD.

METHOD

The research group is compiled of 38 closed police case files from the NPIID (National Police Internal Investigation Department) between 2005 and 2016. The control group is compiled of cases involving excitation and restraint, without leading to death. 148 cases were included from the NPIID between 2005 and 2016 and the Violence Registration Database of the Dutch National Police between 2014 and 2015. Case files of both the research and the control group were systematically analyzed and compared.

RESULTS AND CONCLUSION

The observed patter shows that subjects dying during Physical Restraint are mostly males between 30 and 40 years old with a BMI above 30 kg/m². Both BMI and age are remarkably lower in the control group. Subjects were encountered in a state of excitation mostly attributed to (multiple) drugs (cocaine, MDMA or cannabis). The physical restraint portrayed a pattern of escalation with restraint being mostly face-down, hands cuffed to the back, receiving thoracic pressure, resulting in a high total amount of force used. In the research group 44.7% (17/38) of subjects were encountered (partially) unclothed versus 4.1% (6/148) in the control group. Cause of death in these cases seems to be multifactorial and is comprised of both personal factors and factors during and after the struggle. The different factors are comingled and augment each other. The end effect is that the subjects end up in a fatal spiral.

The clinical surrogate definition of the trigeminocardiac reflex: Development of an optimized model according to a PRISMA-compliant systematic review

BACKGROUND

The trigeminocardiac reflex (TCR) is defined as sudden onset of parasympathetic dysrhythmias including hemodynamic irregularities, apnea, and gastric hypermotility during stimulation of sensory branches of the trigeminal nerve. Since the first description of the TCR 1999, there is an ongoing discussion about a more flexible than the existing clinical definition. Aim of this work was to create a clinical surrogate definition through a systematic review of the literature.

METHODS

In this meta-analysis study, literature about TCR occurrences was, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement, systematically identified through various search engines including PubMed (Medline), Embase (Ovid SP), and ISI Web of Sciences databases from January 2005 to August 2015. TCR was defined as a drop of heart rate (HR) below 60 bpm or 20% to the baseline. We extracted detailed data about hemodynamic changes and searched for connections between arterial blood pressure (BP) and HR changes during such episodes.

RESULTS

Overall 45 studies harboring 57 patients were included in the study but only 32 patients showed sufficient data for final analyze. HR showed a nonlinear behavior with a "tipping point" phenomena that differs in variance from the central/peripheral (20-30% drop) to ganglion (40-49% drop). BP showed a linear behavior with a "central limit" phenomena not differing in variance in the whole subgroup (30-39% drop). An analyzation of the correlation between BP and HR showed a trend to a linear correlation.

CONCLUSIONS

We can show for the first time that HR is the dominant variable in the TCR and present a new surrogate definition model. This model and the role of BP must be better investigated in further studies.

An old drug for use in the prevention of sudden infant unexpected death due to vagal hypertonia

Reflex vagal hypertonia (RVH) has been identified as a possible cause of sudden unexpected death in infants during the first year of life. Homatropine methylbromide (HM) is an anticholinergic drug known to inhibit muscarinic acetylcholine receptors, thus affecting the parasympathetic nervous system. The aim of the present study was to investigate the effects of HM on 24-h Holter electrocardiographic signs of RVH (pre-HM treatment vs post-HM treatment; post-HM treatment vs a control group of healthy infants). A total of 50 patients (mean age, 6.1 ± 2.7 months; 28 males, 22 females; 12 born pre-term) affected by RVH were enrolled in the study. Pre-HM treatment vs post-HM treatment: statistically significant differences were detected for higher heart rate, lower heart rate, mean heart rate, longer sinusal pause, presence of advanced atrio-ventricular blocks, and systolic blood pressure (p < 0.001, p < 0.00001, p < 0.02, p < 0.00001, p < 0.05, and p < 0.04, respectively). A statistically significant correlation was revealed between HM-administered dose and both average heart rate and systolic blood pressure (r = 0.93, p < 0.0001; r = 0.94, p < 0.0001, respectively). No significant differences were detected between post-HM treatment electrocardiographic data and those of the control group. By antagonizing action of the vagus nerve of the parasympathetic system on the heart, thus increasing cardiac frequency, HM treatment appears to feature a good safety profile and be highly effective in preventing transient infantile hypervagotonia, the potential cause of several cases of sudden unexpected death during the first year of life.

Cardiovascular responses to apneic facial immersion during altered cardiac filling

The hypothesis that reduced cardiac filling, as a result of lower body negative pressure (LBNP) and postexercise hypotension (PEH), would attenuate the reflex changes to heart rate (HR), skin blood flow (SkBF), and mean arterial pressure (MAP) normally induced by facial immersion was tested. The purpose of this study was to investigate the cardiovascular control mechanisms associated with apneic facial immersion during different cardiovascular challenges. Six subjects randomly performed 30-s apneic facial immersions in 6.0 +/- 1.2 degrees C water under the following conditions: 1) -20 mmHg LBNP, 2) +40 mmHg lower body positive pressure (LBPP), 3) during a period of PEH, and 4) normal resting (control). Measurements included SkBF at one acral (distal phalanx of the thumb) and one nonacral region of skin (ventral forearm), HR, and MAP. Facial immersion reduced HR and SkBF at both sites and increased MAP under all conditions (P < 0.05). Reduced cardiac filling during LBNP and PEH significantly attenuated the absolute HR nadir observed during the control immersion (P < 0.05). The LBPP condition did not result in a lower HR nadir than control but did result in a nadir significantly lower than that of the LBNP and PEH conditions (P < 0.05). No differences were observed in either SkBF or MAP between conditions; however, the magnitude of SkBF reduction was greater at the acral site than at the nonacral site for all conditions (P < 0.05). These results suggest that the cardiac parasympathetic response during facial immersion can be attenuated when cardiac filling is compromised.

Facial immersion bradycardia in teenagers and adults accustomed to swimming

We compared heart rate and breath-hold duration during facial immersion in teenagers, 11-14 years (N = 6), 15-18 years (N = 6) and adults, 33-48 years (N = 11). The subjects were members of a competitive swimming club, and were familiar with facial immersion. In contrast to the results of a previous study (J. Appl. Physiol. 63 (1987) 665) in which naïve subjects were used, the 11-14 group were able to breath-hold as long as adults (mean +/- SE, 47+/-6 vs. 46+/-4 s). This allowed time for the full development of bradycardia. Pre-immersion heart rate was significantly higher in young teens than in adults (100+/-4 vs. 78+/-3 b.p.m.). Heart rate after 30 s of head immersion was statistically identical (young teens, 65+/-5 b.p.m.; adults, 64+/-3 b.p.m.). Therefore, both the percentage reduction from pre-immersion rate and rate of fall in heart rate were greater in 11-14-year-olds than in adults. Oxygen loading increased breath-hold time in all groups, and slowed the onset of bradycardia in adults and older teens, but not in the 11-14-year-old group, during the first 10 s after immersion. We conclude that breath-hold time in teenagers is influenced by familiarity with underwater breath-holding. The resulting cardiovascular adjustments in 11-14-year-olds are intrinsically at least as intense as those in adults and seem to have a faster onset.

Sudden death after a cold drink: case report

We report a case of sudden cardiac death in a 12-year-old boy after rapid ingestion of a frozen slurry drink. The cause of death was determined to be a cardiac arrhythmia secondary to a previously undiagnosed cardiac rhabdomyoma with associated myocardial scarring. Ingestion of cold liquids has been associated with syncope, but not sudden cardiac death. In this case, bradycardia induced by cold-induced vasovagal reflex may have precipitated the terminal arrhythmia. Ingestion of cold liquids should be considered a potential trigger for fatal cardiac arrhythmias in patients with underlying heart disease.

Influence of parasympathetic dysfunction and hyperinsulinemia on the hemodynamic response to an isometric exercise in non-insulin-dependent diabetic patients

The handgrip test has long been used as a test for investigating cardiac autonomic neuropathy in diabetic patients. However, the factors involved in the hemodynamic response to the handgrip test have not been thoroughly studied. The aim of this study was to investigate blood pressure (BP) and heart rate (HR) responses to an isometric test in non-insulin-dependent diabetics (NIDDs) and to correlate the results with vagal function evaluated by three standardized tests and with plasma insulin levels. Fifty-five NIDDs, 35 of whom had one to three abnormal parasympathetic tests (PS+), were compared with 10 healthy control subjects. Fasting and postprandial plasma insulin levels were significantly higher in the PS+ than in the PS- patients. Resting HR correlated significantly with log fasting and postprandial insulin. In PS+ NIDDs, resting HR was significantly higher than in PS- patients. Age-matched comparisons also showed that resting systolic BP was significantly higher in PS+ patients than in controls. In PS- patients, the mean acceleration of HR was significantly higher than in the control group from the second to the fifth minute, and the BP response was also higher than in controls. These data suggest that (1) sympathetic response to an isometric exercise is increased in PS- NIDDs; (2) cardiac parasympathetic dysfunction is associated with a more severe insulin resistance; and (3) the subsequent higher plasma insulin level may contribute to the increase in resting HR and BP through sympathetic activation while limiting the hemodynamic response to an isometric exercise through its vasodilative effect.

Evidence for differential sympathetic and parasympathetic reinnervation after heart transplantation in humans

During heart transplantation (HTX) all neural connections are severed. In humans, signs of autonomic reinnervation have been found. In this study non-invasive tests were used to compare signs of sympathetic and parasympathetic reinnervation. Non-invasive autonomic function tests and heart rate variability parameters (HRV; 24 h electrocardiographic registration) were used to investigate signs of reinnervation. 16 HTX patients (14 males) were compared with age-and sex-matched controls. Parasympathetic heart rate changes in HTX compared to controls were attenuated during the diving test, deep breathing, the Valsalva maneuver and standing up but not during carotid sinus massage. Sympathetic heart rate increases were lower during the cold pressor test and mental stress. The blood pressure responses were comparable to the control group, but not during active standing and tilting. This finding suggests an obligatory 'blood pressure' role for the innervated heart in these two tests. All HRV parameters were lower in HTX. One or more normal parasympathetic responses were found in 13 out of 16 patients versus 4 out of 16 with normal sympathetic responses (p < 0.05). Heart rate variations were less in case of a higher donor age, and higher in case of a longer time after HTX. Parasympathetic signs of reinnervation are more common than sympathetic signs of reinnervation. A higher donor age reduces signs of reinnervation. If the sympatho-vagal balance is a prognostic factor in HTX patients as it is in other cardiac diseases these findings are clinically relevant.

Low incidence of the oculocardiac reflex and postoperative nausea and vomiting in adults undergoing strabismus surgery

PURPOSE

To investigate the incidence of the oculocardiac reflex (OCR), and of postoperative nausea and vomiting (PONV) in adults undergoing strabismus surgery.

METHODS

Adults (18-86 yr) undergoing inpatient strabismus surgery received 10 micrograms.kg-1 atropine and 10 micrograms.kg-1 altentanil iv and were randomly allocated to: (A) 5 mg.kg-1 thiopentone iv, isoflurane/N2O maintenance; (B) 3 mg.kg-1 propofol iv, propofol/N2O maintenance (10-14 mg.kg-1.hr-1); 3 mg.kg-1 propofol iv, propofol/air/O2 maintenance (10-14 mg.kg-1.hr-1). Analyses were with the number-needed-to-treat/harm.

RESULTS

In 97 adults the absolute risk of OCR (13-20%) and PONV (21-31% after 24 hr) was low, with no differences between groups. Number-needed-to-treat to prevent PONV with propofol with or without N2O compared with thiopentone-isoflurane was 7 to 11. Number-needed-to-harm for one OCR with propofol compared with thiopentone-isoflurane was 17.

CONCLUSION

Adults undergoing strabismus surgery with prophylactic atropine had a low risk of OCR and PONV, independent of the anaesthetic technique used.

Peripheral vasoconstrictor responses to sympathetic activation in diabetic patients: relationship with rheological disorders

The sympathetic nervous system regulates peripheral blood flow. This study investigated sympathetic vascular control in diabetic patients by measuring cutaneous blood flow (CBF) with a laser Doppler device at rest and during three sympathetic activation tests: deep-breathing, changing positions from sitting to standing, and using the Valsalva maneuver. The influence of various factors, particularly rheological changes, was also assessed. Forty-two type II diabetes mellitus (non-insulin-dependent [NIDDM]) patients and 14 control subjects were studied. The mean value and standard deviation (SD) of basal CBF at rest were not significantly different in the two groups. In 12 NIDDM patients, the SD was less than the lowest limit found in the controls. During the three tests, the reduction in CBF and its downward slope were lower in NIDDM patients than in controls, with the greatest difference occurring during the deep-breathing test. During this test, the downward slope of CBF was less than the lowest control level in 14 NIDDM patients. The log SD of basal CBF correlated with the decrease in CBF during the sitting-to-standing and Valsalva tests in control subjects and during all three tests in NIDDM patients. In NIDDM patients, log mean basal CBF correlated negatively with the log erythrocyte filtration index ([FI] an index of rigidity) and positively with hemoglobin A1c (HbA1c). The log downward slope of CBF during the deep-breathing test correlated negatively with log erythrocyte Fl. The log downward slope of CBF during the sitting-to-standing and Valsalva tests correlated positively with total cholesterol and triglycerides, respectively. Basal CBF and the CBF response to these tests did not correlate with retinopathy, nephropathy, peripheral neuropathy, or heart rate variations during these tests. This study suggests that CBF assessment by laser Doppler flowmetry affords an attractive noninvasive way to investigate sympathetic nervous function in diabetic patients. The amplitude of changes in basal CBF and the decrease in CBF during the deep-breathing test show that this is a simple and sensitive procedure for detecting sympathetic nerve dysfunction. Moreover, theological blood properties and metabolic factors seem to strongly influence resting CBF and vasomotor reflexes.

Estimation of fast vagal response by time-dependent analysis of heart rate variability in normal subjects

In this study, the selective windowed discrete Fourier transform algorithm (SDA) for time-frequency analysis was applied on non-stationary heart rate signals, recorded during vagal perturbations. These perturbations were achieved in healthy subjects (aged 6-42 years) by inducing the oculocardiac reflex and the diving response. The results showed that the SDA can detect and quantify the expected, although brief, increase in vagal tone, by displaying a marked transient increase in the respiratory peak of the time-dependent spectrum. It allowed us to demonstrate an age-dependent reduction of the vagal response, obtained from the respiratory peak of the heart rate time-dependent spectrum. The SDA approach is thus an adequate tool for the evaluation of an instantaneous change in vagal activity, as well as steady-state vagal activity, including the detection of a malfunction or an exaggerated response of the parasympathetic tone. Since changes in heart rate control are expressed by a transient response, they would not have been detected by a standard, steady-state spectral analysis of heart rate variability, which requires the consideration of long and steady trace lengths and would therefore cause smearing of such fast changes. Time-dependent, or transient changes in autonomic control can thus be detected and quantified by SDA time-frequency analysis.

Human sympathetic nerve activity to glabrous skin does not increase during simulated diving

In humans, cardiovascular adjustment to simulated diving causes a marked increase in sympathetic outflow to intramuscular vessels and muscle vasoconstriction. Skin vasoconstriction in the hand also occurs during diving in humans. Skin nerve sympathetic activity (SSA), containing vasoconstrictor signals to glabrous skin, unexpectedly was reduced during diving in a previous study of SSA recorded in the peroneal nerve. SSA was recorded by microneurography in the median nerve in 13 healthy volunteers during simulated diving. Skin blood flow in the hand and one finger was monitored. The typical SSA response, irrespective of duration of diving and water temperature, was an increase during the control period immediately prior to immersion of the face and a sudden reduction of SSA when the face was immersed. The increase in SSA preceding the dive was accompanied by vasoconstriction, which continued during the dive, but re-dilation regularly occurred before the end of the dive. Inhibition of SSA was not total. Mental arithmetic during diving evoked strong bursts of SSA, similar to those seen normally during mental stress. It is concluded that the true response of SSA to simulated diving is an inhibition of the immediately preceding outflow, in agreement with observations of cutaneous blood flow in animals. The skin vasoconstriction recorded during simulated diving is a consequence of an SSA increase before the procedure, suggested to be a stress response before the forthcoming manoeuvre. The SSA response during simulated diving is the opposite to that of sympathetic outflow to muscle, which emphasizes the diversity of sympathetic regulation of different organ systems.

Lack of global vagal propensity in patients with oculocardiac reflex

BACKGROUND

Profound bradycardia during ophthalmic surgery is a rare but potentially serious event. Little is known about the predictability of the oculocardiac reflex.

METHODS

Four vagotonic maneuvers were performed on six patients who had profound oculocardiac reflex (3- to 10-second asystole) during eye surgery, the results of which were compared with 30 previously studied control subjects. Electrocardiographs were monitored during the following vagotonic maneuvers: diving response (apneic facial immersion), Valsalva maneuver, ocular compression, and carotid sinus massage.

RESULTS

The degree of heart rate slowing as a result of diving response, Valsalva maneuver, and, notably, ocular compression did not differ when these patients were compared with the 30 previously studied control subjects. Carotid sinus massage produced significantly (P = 0.01) more bradycardia in the six patients (mean +/- standard deviation, -24% +/- 6%) than in the 30 control subjects (-12% +/- 7%). The heart rate response to pressure on the eyes did not correlate with prior intraoperative oculocardiac reflex.

CONCLUSION

The discrepancy in heart rate sensitivity between surgical extraocular muscle tension and ocular compression may be due to different sensory receptors and brain stem processing for the trigeminally mediated oculocardiac reflex. Carotid sinus massage may help predict low heart rates during eye surgery.

The intraoperative oculocardiac reflex as a predictor of postoperative vaso-vagal responses during adjustable suture surgery

Adjustable suture surgery has become a popular method of strabismus correction in those cases in which results are less predictable, such as reoperations, thyroid ophthalmopathy, and blind eyes. Complications related to adjustable strabismus surgery are, in general, no different than those related to standard surgical techniques. We noticed a subgroup of patients who experienced significant vaso-vagal responses (V-VR) during postoperative adjustment and sought to discover a method of identifying these patients prior to adjustment. Sixty patients were studied prospectively from July 1991 to July 1992. All patients had surgery under general anesthesia and were adjusted 24 hours later. A positive oculocardiac reflex (OCR) occurred when a 10% or greater intraoperative change in heart rate was associated with traction on an extraocular muscle. A positive V-VR postoperatively consisted of one or more subjective findings (dizziness, light-headedness, nausea, or body temperature changes), and two or more objective findings (10% or greater change in heart rate, hypotension, pallor, diaphoresis, vomiting, disorientation, or loss of consciousness). Variables studied for predictive value included OCR, age, sex, strabismus type, previous surgery, muscle adjusted, and systemic disease. Twenty-five patients (41.6%) had a positive V-VR during adjustment. Twenty-seven patients (45%) had a positive OCR. Eighty-five percent of patients with a positive OCR and 9% of patients with a negative OCR had a positive V-VR. Younger patients were also more likely to have a positive V-VR. A positive intraoperative OCR under general anesthesia during strabismus surgery is highly predictive of a postoperative V-VR during planned adjustment.

Cluster headache: alterations in heart rate, blood pressure and orthostatic responses during spontaneous attacks

Changes in heart rate and blood pressure (BP) have been monitored beat-to-beat in a cluster headache patient with and without attacks using a non-invasive Doppler servo method. Two attacks were monitored and during one of them a tilt test was carried out. The variability of heart rate and BP was greater during the attack than during the interparoxysmal period. A marked bradycardia occurred during attacks. Systolic BP increased slightly. There was no heart rate increase after tilting during the attack, whereas this was present invariably during tests carried out interparoxysmally. BP changes during "attack tilt" were difficult to evaluate because of large variation. This may be the first observation of a baroreflex arc dysfunction during a cluster headache attack.