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At least 91 records · Page 5Linked to original sources
PubMed2006

Use of the oculocardiac reflex to assess vagal reactivity during quiet sleep in neonates.

Arousal from sleep can be a protective response to life-threatening stimuli. Hence, faults within state-switching processes may lead to fatal events. To investigate the role of the nervous system during cardiac failure triggered by phasic, vagally mediated stimulation, we analysed autonomic and behavioural reactions in 50 premature neonates during quiet sleep (QS) -- a sleep state characterized by a preponderance of tonic, parasympathetic activity. Bradycardia was induced with a standardized ocular compression test. Neither awakening nor behavioural escape reactions were observed during or after an episode of bradycardia. Eighty-six per cent of the provoked bradycardic episodes induced central apnoea. During QS, the neonates' respiratory response and arousability were found to be time-dependent: when the test was performed early in the QS episode, apnoea was more frequent (94%), and no sleep state change occurred. When ocular compression was performed in the later part of the QS episode, a transition towards active sleep was observed, together with significantly fewer episodes of apnoea (64%). These results indicate that a progressive decrease in the respiratory system's responsiveness to phasic, parasympathetic stimulation occurs during QS, whereas arousability increases. Our study suggests that newborns could be more vulnerable to potentially fatal events during the initial portion of a QS episode.

Apnea↗
PubMed1978

Two types of febrile seizure: anoxic (syncopal) and epileptic mechanisms differentiated by oculocardiac reflex.

The duration of cardiac asystole induced by ocular compression was measured in 100 consecutive children referred for electroencephalographic examination after one or more febrile convulsions (FC). The children were classified into three groups-namely, those with anoxic FCs, those with epileptic FCs, and "others"-according to the appearances of the FC and the electroencephalogram (EEG). In 14 children the description of the FC suggested non-epileptic anoxic cerebral seizures such as are seen after prolonged syncope or breath-holding. In 35 children the FCs were assumed to be epileptic in mechanism on the basis of unilateral (hemiclonic) twitching, known cerebral disease, a family history of epilepsy, or spikes on the EEG. In the 51 "others" the FCs could not be classified. Definitely abnormal asystole (four seconds or over) was induced by ocular compression in half the anoxic group, in 16% of the "others," but in none of the epileptic group. The differences between the degree of asystole induced in each of the three groups was highly significant (P=0.005).These results support the hypothesis that vagal-mediated cerebral ischaemic anoxia is implicated in the genesis of FCs that resemble anoxic seizures and in a substantial number of those without an obvious epileptic mechanism. The significance, genetics, management, and prognosis of FCs must now be re-examined in this light.

Brain Ischemia↗
PubMed2000

[Effects of sevoflurane versus propofol on oculocardiac reflex--a comparative study in 180 children].

Oculocardial reflex (OCR) occurs particularly through manipulation of the medial rectus muscle and results in a bradycardic arrhythmia. In children the incidence is between 60 and 80%. After using sevoflurane in clinical practice, the absence or non-occurrence of this reflex was observed. The data of 180 healthy children aged between four and 14 years who had to undergo strabismus surgery under general anaesthesia were analysed: group I (n = 92), group II (n = 88). All children received standard premedication with midazolam, no anticholinergic drugs were administered. During narcosis, analgesia was maintained routinely with alfentanil. In group I sevoflurane was inhaled for hypnosis and in group II propofol was injected as intravenous hypnotic drug. The depth of anaesthesia was adjusted according to clinical criteria. To compare both groups, heart rate (HR) was determined before, during and after surgical intervention. OCR was defined as a heart rate declining by more than 20% from the initial HR.OCR is described in all methods of general anaesthesia. Under sevoflurane the occurrence of the reflex was significantly (p < 0.05) reduced to 14% of all patients as compared to 75% in patients who received a propofol infusion. Sufficient reflex reduction according to the depth of narcosis under sevoflurane in combination with the sympathomimetic effects of this drug could therefore be discussed as a reason for its positive effects. In our opinion, the use of sevoflurane should be considered as an option for general anaesthesia in strabismus surgery.

Adolescent↗
PubMedDate not supplied

Prevention of oculocardiac reflex (O.C.R) during extraocular muscle surgery.

In the present study the effectiveness of intravenous atropine sulphate which blocks the peripheral muscarinic receptors at the heart and retrobulbar xylocaine hydrochloride which blocks the conduction at ciliary ganglion on the afferent limb of OCR was studied during strabismus surgery. The study was conducted on fifty three patients of either sex having squint of more than ten years duration. The patients were randomly allocated into four groups. No preanaesthetic medication with atropine or retrobulbar block with xylocaine was given in control group of patients. In the second group, only preanaesthetic medication with atropine was given; while in the third group only retrobulbar injection of xylocaine was given five minutes before operation. In the last group both atropine as preanaesthetic medication and xylocaine as retrobulbar block were given. The electrocardiographic recordings were taken before and throughout the operative procedure. It was interesting to note that in the group where atropine and xylocaine were used none of the patients exhibited activation of OCR. Results have been discussed.

Adolescent↗