Christian Dubreuil

Remifentanil and controlled hypotension; comparison with nitroprusside or esmolol during tympanoplasty.

Purpose: To determine whether remifentanil, combined with propofol, could induce controlled hypotension, reduce middle ear blood flow (MEBF) measured by laser-Doppler flowmetry, provide a “dry” operative field, and could be compared with nitroprusside or esmolol combined with alfentanil and propofol.Methods: Thirty patients undergoing tympanoplasty and anesthetized with 2.5 mg·kg−1 propofoliv followed by a constant infusion of 120µg·kg−1·min−1, were randomly assigned in three groups to receive either 1µg·kg−1 remifentaniliv followed by a continuous infusion of 0.25 to 0.50µg·kg−1, or nitroprussideiv, or esmololiv combined for the latter two groups with alfentaniliv.Results: Controlled hypotension was achieved at the target pressure of 80 mmHg within 107±16, 69±4.4, 53.3±4.4 sec for remifentanil, nitroprusside and esmolol respectively. MEBF decreased by 24±0.3, 22±3.3, 37±3% and preceded the decrease in SABP, within 30±6.1, 11.2±3.1, 15±2.8 sec for remifentanil, nitroprusside and esmolol respectively. Remifentanil, and nitroprusside decreased MEBF autoregulation less than esmolol (0.36±0.1, 0.19±0.2, −0.5±0.2). Controlled hypotension was sustained in all three groups throughout surgery, and the surgical field rating decreased in a range of 80% in all three groups. Nitroprusside decreased pH and increased PaCO2. There were no postoperative complications in any of the groups.Conclusions: Remifentanil combined with propofol enabled controlled hypotension, reduced middle ear blood flow and provided good surgical conditions for tympanoplasty with no need for additional use of a potent hypotensive agent.RésuméObjectif: Déterminer si le rémifentanil, associé au propofol, peut induire une hypotension contrôlée, réduire le débit sanguin de l’oreille moyenne (DSOM) mesuré par laser-Doppler, assurer un champ opératoire exsangue et être comparé au nitroprussiate et à l’esmolol associés à l’alfentanil et au propofol.Méthode: Trente patients subissant une tympanoplastie, et anesthésiés par 2,5 mg·kg−1 de propofoliv suivis d’une perfusion de 120µg·kg−1·min−1, ont été répartis après randomisation en 3 groupes recevant soit 1µg·kg−1 de rémifentaniliv suivis d’une perfusion de 0,25 à 0,50µg·kg−1·min−1, soit du nitroprussiate, soit de l’esmololiv, associé pour les 2 derniers à de l’alfentanil.Résultats: Tout d’abord, l’hypotension contrôlée a été obtenue au niveau souhaité de 80 mmHg en 107±16; 69±4,4; 53,3±4,4 sec pour le rémifentanil, le nitroprussiate et l’esmolol. Le DSOM a diminué de 24±0,3; 22±3,3; 37±3% et a précédé la chute de pression de 30±6,1; 11,2±3,1; 15±2,8 sec pour le rémifentanil, le nitroprussiate et l’esmolol. Le rémifentanil et le nitroprussiate ont moins réduit l’autorégulation que l’esmolol (0,36±0,1; 0,19±0,2; −0,5±0,2). Ensuite, l’hypotension contrôlée a été maintenue dans les 3 groupes tout au long de l’opération, et le saignement opératoire a été diminué de 80% dans les 3 groupes. Le nitroprussiate a diminué le pH et augmenté la PaCO2. Il n’y a eu aucune complication postopératoire dans chacun des groupes.Conclusion: Le rémifentanil associé au propofol a permis de réaliser une hypotension contrôlée, de réduire le débit sanguin de l’oreille moyenne et d’assurer de bonnes conditions opératoires pour la tympanoplastie sans recours à un agent hypotenseur puissant.

Remifentanil induces consistent and sustained controlled hypotension in children during middle ear surgery

PurposeTo determine in children whether remifentanil combined with sevoflurane, could induce controlled hypotension, reduce middle ear blood flow (MEBF) measured by laser-Doppler, and provide a satisfactory operative field.MethodsForty children undergoing middle ear surgery and anesthetized with sevoflurane were randomly assigned to receive either 1 μg·kg−1 remifentanil iv followed by a continuous infusion of 0.2 to 0.5 μg·kg−1min−1 or 0.25 μg · kg−1min−1 nitroprusside iv and alfentaniliv (n = 20 in each group).ResultsControlled hypotension was achieved at the target mean arterial pressure (MAP) of 50 mmHg (P < 0.01) within 121 ±21 and 62 ± 9 sec for remifentanil and nitroprusside respectively. MEBF decreased by 22 ± 4 and 20 ± 6% and preceded the decrease in MAP within 20 ± 7 and 10 ± 3 sec for remifentanil and nitroprusside respectively. Remifentanil, and nitroprusside decreased MEBF autoregulation (0.41 ± 0.2 and 0.37 ± 0.3 respectively). Controlled hypotension was sustained in both groups throughout surgery, and the surgical field rating was good. Nitroprusside increased PaCO2 slightly, and there were no postoperative circulatory, neurological or metabolic complications in any of the groups.ConclusionRemifentanil combined with sevoflurane in children enabled controlled hypotension, reduced MEBF and provided good surgical conditions for middle ear surgery with no need for additional use of a specific hypotensive agent.RésuméObjectifDéterminer si le rémifentanil, combiné au sévoflurane, peut permettre une hypotension contrôlée, une réduction du débit sanguin de l’oreille moyenne (DSOM) mesuré par Doppler à laser, et assurer un champ opératoire exsangue chez l’enfant.MéthodeQuarante enfants opérés à l’oreille moyenne et anesthésiés par du sévoflurane, ont été répartis par randomisation en deux groupes (n = 20) recevant soit l μg kg−1 de rémifentanil iv suivi d’une perfusion continue de 0,2 à 0,5 μg kg−1 min−1, soit 0,25 μg kg−1 min−1 de nitroprussiate iv, associé à de l’alfentanil iv.RésultatsTout d’abord, l’hypotension contrôlée a été obtenue au niveau souhaité de 50 mmHg (P < 0,001) en 121 ± 21 et 62 ± 9 sec pour le rémifentanil et le nitroprussiate respectivement. Le DSOM a diminué de 22 ± 4 et de 20 ± 6 % et a précédé la chute de pression de 20 ± 7 et de 10 ± 3 sec pour le rémifentanil et le nitroprussiate respectivement. Le rémifentanil et le nitroprussiate ont diminué l’autorégulation (0,41 ± 0,2 et 0,37 ± 0,3). Ensuite, l’hypotension contrôlée a été maintenue dans les deux groupes tout au long de l’opération, et l’état du champ opératoire a été excellent. Le nitroprussiate a augmenté modérément la PaCO2. Il n’y a eu aucune complication circulatoire, neurologique ou métabolique postopératoire dans chacun des groupes.ConclusionLe rémifentanil associé au sévoflurane chez l’enfant a permis de réaliser une hypotension contrôlée, de réduire le débit sanguin de l’oreille moyenne et d’assurer de bonnes conditions opératoires pour l’opération de l’oreille moyenne sans recourir à un hypotenseur spécifique.

Acuteness of Preoperative Factors to Predict Hearing Preservation in Acoustic Neuroma Surgery

Objectives: To determine in patients with acoustic neuromas the predictive factors of hearing preservation according to clinical, radiological, and electrophysiological parameters and to evaluate, for each of these predictive factors, the percentage of patients with preserved hearing.

Effects of posture, hypotension and locally applied vasoconstriction on the middle ear microcirculation in anaesthetized humans.

Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30°), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30°, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O2 and CO2 in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P<0.0001,P<0.0001,P<0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P>0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P<0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations. The behaviour of the middle ear blood flow submitted to hypotension, posture, or to vasoconstriction could be related to counteracting regulatory responses and/or to direct vascular effects.

Sympathetic nerve regulation of cochlear blood flow during increases in blood pressure in humans.

Abstract The purpose of this work was to show that regulation of the blood flow to the cochlea by the sympathetic nervous system occurs in humans at the level of the cochlear microcirculation during increases in blood pressure and that its involvement depends on the pressure level. Eight anaesthetized patients undergoing tympanoplasty for hearing disease took part in a pharmacological protocol of stimulation and inhibition of the autonomic nervous system (ANS) to provide variations in systolic blood pressure (BPS) and cochlear blood flow (CBF). The CBF was measured by laser-Doppler flowmetry. Changes in autonomic nerve activity were brought about by changes in baroreceptor activity (BR) initiated by the injection of an α adrenergic agent before and after sympathetic and parasympathetic blockade. The CBF variations (δCBF) were plotted against BPS increases at each stage of the ANS inhibition. The BR diminished significantly after α blockade, after α and β blockade, and after α and β blockade and atropine, by 50% (P < 0.01), 29% (P < 0.05), and 95% (P < 0.001) respectively. The BPS increased significantly (P < 0.01) by 36 (SD 9)%, 47 (SD 1)%, and 67 (SD 16)% respectively. The CBF response to an increase in BPS exhibited two opposing variations in the patients: CBF decreased significantly in one group, and increased significantly in the other group. In both groups, δCBF decrease and δCBF increase, respectively, were significant after ANS blockade; even so the decrease and increase, respectively, levelled off at BPS around 160 mmHg before ANS blockade. For BPS below 160 mmHg, correlations between δCBF and BPS were significant before inhibition and after inhibition of ANS. For BPS above 160 mmHg, BPS and δCBF were not correlated before inhibition of ANS, and were significantly correlated after inhibition of ANS. For BPS below 160 mmHg, CBF response to the BPS increase was the same before and after ANS blockade, i.e. ANS control did not predominate; even so, for BPS above 160 mmHg, the CBF response to BPS increase was different before and after ANS blockade: CBF varied significantly after ANS blockade as it varied for BPS below 160 mmHg, while it remained constant before ANS blockade that elicited ANS control of CBF. In conclusion, sympathetic nerve regulation via its vasomotor tone at the level of cochlear microcirculation occurred markedly when the blood pressure was above 160 mmHg; the autonomic nervous system would appear to control the cochlear blood flow against large variations in blood flow in response to hypertensive phenomena.

Otoacoustic emissions and brainstem auditory evoked potentials in children with neurological afflictions

Findings are reported for evoked otoacoustic emissions (EOAEs) recorded from 22 children with neurological afflictions, whose brainstem auditory evoked potentials (BAEPs) were pathological on at least one side (41 ears explored). Our results confirmed that EOAEs are always present in children and infants having normal BAEPs. Absence of EOAE (n = 22) was almost always related to middle ear or cochlear damage with BAEPs indicating diagnoses, respectively, of transmission damage (n = 7) or endocochlear damage (n = 16). Conversely, for BAEP diagnoses of retrocochlear damage (n = 12), EOAEs were always present. EOAEs associated with BAEPs, therefore, appear to offer a well-adapted technique for precise etiological diagnosis of childhood hearing loss. When no wave is identifiable by BAEP recording, EOAE presence indicates retrocochlear damage.

Brainstem auditory evoked potentials following meningitis in children

The report concerns findings for brainstem auditory evoked potentials (BAEPs) recorded in 116 children, aged between a few days and 7 years, having suffered from bacterial meningitis. 26% of cases occurred between birth and 6 months, 55% between 6 months and 2 years, and 19% after 2 years of age. Hemophilus was the most common bacteria (49%), followed by Pneumococcus (22%) and Meningococcus (15%). Neurological complications were found in 30% of the meningitis cases and accounted for 85% of all complications found. 29% of BAEPs were abnormal, of which 47% revealed transmission, 32% endocochlear and 21% retrocochlear impairment. Transmission impairment mainly occurred before the age of 2 years (88%), most frequently in meningococcus meningitis cases (44%), and independently of neurological complications. Retrocochlear impairment was found in association with neurological complications in 71% of cases. Endocochlear BAEP damage was found in 9.5% of cases, half of which were bilateral and total, representing cophosis: it was found at all ages, and without any particular associated neurological complication. Hemophilus was the commonest bacterial agent in endocochlear cases overall, with Pneumococcus underlying 50% of cophosis cases. The study shows BAEP recording in association with a clinical ear examination is useful following childhood bacterial meningitis, screening for definitive endocochlear and deafness, distinguishing total from partial hearing-loss and indicating suitable treatment.

Type of initial brainstem auditory evoked potentials (BAEP) impairment and risk factors in premature infants

Brainstem auditory evoked potentials (BAEPs) were recorded in 89 premature infants aged between 34 and 52 weeks. 47.2% had normal and 52.8% abnormal BAEPs in at least one ear. Seven risk factors were taken into account: birth weight lower than 1500 g, hypoxia, neurological damage, fetal pathology, associated malformation, the use of ototoxic drugs, and exchange transfusion. The type of BAEP impairment was defined as either endocochlear, transmission or retrocochlear damage. Percentage BAEP impairment was higher in case of hypoxia (63.3%) but remained similar whether the other risk factors were present or absent. Transmission impairment was more frequent in case of birth weight lower than 1500 g, hypoxia or ototoxic drug administration; Endocochlear damage occurred more frequently when ototoxic drugs had been used or exchange transfusion performed. When birth weight was lower than 1500 g, transmission damage was more frequent than when birth weight was higher than 1500 g. In contrast, endocochlear damage was more frequent when birth weight was higher than compared with lower than 1500 g. In male infants, BAEP impairment was more frequent and more often of retrocochlear type than in female infants. BAEP impairment was more frequently of endocochlear type in female compared to male infants. Among the 89 premature infants recorded, 11.2% has endocochlear damage corresponding to potentially handicapping hearing loss. These results are discussed with reference to the literature.

Clinical interest of brainstem auditory evoked potentials in 72 children with inadequate language development.

The present study is of brainstem auditory evoked potentials (BAEP) in 72 children, of 2 to 13 years of age, showing inadequate language development. The age of the children was mainly below the age of 4 (39 cases = 54%), peaking between 3 and 4 years of age (33 cases = 46%). Even so, 82% of our patients were 3 years old or over: 64% were boys, 36% girls, the proportion of boys falling off with age 26% (19 cases) of BAEPs recorded were normal, 74% (53 cases) pathological. High prevalence of undiagnosed hearing loss was found. Physiopathological BAEP classification showed endocochlear impairment in 68% (36 cases), conductive impairment in 21% (11 cases) and retrocochlear impairment in 11% (6 cases) of subjects. Unilateral impairment (20 cases = 28%) cannot account for inadequate language development; but, in the 8 cases (11%) of total bilateral hearing loss, and the 15 cases (21%) of partial bilateral impairment, hearing loss more or equal to 50 dB HL, impaired hearing would play a role in the retardation.

Transient Evoked Otoacoustic Emissions in Nonsurgical Ear

Several studies have reported contralateral hearing deficits following ear surgery. This study aimed to evaluate changes in micromechanical cochlear properties which could occur in the contralateral ear following ear surgery, using transient evoked otoacoustic emission (TEOAE) recording. Surgery involved tympanic membrane surgery in 13 cases and middle ear surgery in 16 cases. TEOAEs were recorded and compared for contralateral ears before (day 1: D1) and after (day 2: D2) ear surgery. Two patients failed to show a TEOAE reproductibility > 75%, and were excluded from the study, thus reducing the number of patients to 27. Results were compared to those of a control group of 12 normal hearing subjects, recorded in similar conditions also on day one (D1) and day two (D2). The difference between D1 and D2 was not significant in either group. Pre/postsurgery variations in TEOAE amplitude for the patient group were negatively and significantly correlated with the corresponding preoperative levels in that the greater the presurgical TEOAE level, the larger the decrease in postoperative level. Compared to the variation confidence intervals in the control group, TEOAE amplitude remained stable in 15 patients, increased in four and decreased in eight. These three groups of patients differed only regarding preoperative TEOAE amplitude values, which were significantly greater in the group which presented a decrease in TEOAE amplitude than in the others. Increase in TEOAE amplitude was more frequent after tympanic membrane surgery. On the other hand, TEOAE amplitude decrease was more frequent after middle ear surgery, and is significant compared to the tympanic membrane surgery results. The results show that cochlear micromechanical properties may be reduced in the ear contralateral to surgery and that this decrease depends on the severity of the surgical procedures in the operated ear, such as drilling or opening of the oval window.