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PubMedDate not supplied

[Postoperative pain as the fifth vital parameter].

INTRODUCTION: Acute postoperative pain and its therapy is a great challenge for all health-care providers in operative medicine today. Despite development of new analgesic drugs and different therapeutic modalities in pain treatment, acute postoperative pain represents a negative experience for many surgical patients. MATERIAL AND METHODS: By reviewing relevant medical articles on this topic, we tried to find answers on the reasons why many surgical patients have pain in the postoperative period despite implementation of modern and powerful analgesic therapy like patient-controlled analgesia (PCA), spinal/epidural opioids and regional analgesia. RESULTS: The reasons of inefficacy of many analgesic therapeutic methods are multiple. One of them is the attitude of patients and healthcare workers to pain. Many of them consider pain is a natural and physiological consequence of different diseases and pathological conditions and moderate to severe pain is considered as acceptable consequence of surgery. Another important factor contributing to undertreatment is that pain is invisible in most hospital wards: severity of pain is not assessed, and patients are reluctant to "complain." Unless severity of pain is assessed on a routine basis, pain cannot be effectively treated. Thus, one of the most important changes in the process of improving the efficacy of pain treatment is to introduce pain assessment as the fifth vital sign in addition to the traditional four vital signs (temperature, pulse, blood pressure and respiratory rate). DISCUSSION: Introduction of the "fifth vital parameter" would solve many problems in postoperative pain therapy, because healthcare workers take vital signs very seriously both for monitoring and treatment. By frequent measuement and registration of pain intensity and by organization of teams for treatment of postoperative pain, analgesic therapy would be more efficient, and whole therapy of surgical patients would be more qualitative. Undertreatment of pain can have very serious consequences; delayed improvement, change of immune system, changed answer to stress, appearance of vegetative symptoms and possibility of permanent changes in peripheral and central nervous system resulting in chronic pain syndrome. These effects are very harmful, changing quality of life of the whole family because the treatment of chronic pain syndrome is very difficult and expensive. CONCLUSION: Anesthesiologists have a central role in perioperative treatment of surgical patients (from the preoperative preparation through anesthesia and intraoperative monitoring to postoperative treatment and monitoring at the department of the intensive care and at the department of postanesthetic care). Due to abovementioned and familiarity with many therapeutic modalities, like spinal/epidural application of analgesics, regional anesthesia/analgesia many clinicians and pain specialists consider anesthesiologists are those who can organize and supervise teams for acute postoperative pain services.

Humans↗

PubMed2005

Microvascular decompression in patients with hemifacial spasm: report of 1200 cases.

BACKGROUND: Microvascular Decompression (MVD) operation is the most reliable treatment for hemifacial spasm (HFS), but it causes many complications. The aim of this retrospective study was to investigate the factors relavent to the effects and postoperative complications of microvascular decompression on hemifacial spasm. METHODS: A total of 1200 HFS patients treated with MVD were studied retrospectively. The root exit zone (REZ) of the facial nerve was exposed through the infraflocculus approach, the offending vessels were identified and separated from the REZ, and a Teflon graft was interposed between the offending vessels and the brain stem. Brain stem auditory evoked potential (AEP) was monitored intraoperatively. RESULTS: The offending vessels can be identified in all patients. The anteroinferior cerebellar artery was the main offending vessel (42.6%). Patients with vertebral artery compression had a multiple vascular compression fashion. Follow-up for 2 - 10 years (mean 4.2 years) showed that 88.7% patients were cured and 5.6% relieved, with an effective rate of 94.3%. Recurrence rate was 3.2%, and the ineffective rate was 2.6%. The most frequent complication was hearing dysfunction (2.8%). CONCLUSIONS: MVD is the most definitive treatment method of HFS. The key procedures of this operation include adequate exposure of the REZ, identification of the offending vessels, and proper positioning of Teflon grafts. Complications can be reduced effectively by utilizing a real-time AEP monitoring during the operation.

Adult↗

PubMed1983

Cortical oxidative metabolism under conditions of ischemia, hypoxia, and asphyxia in the rabbit.

The purpose of this investigation was to compare the effects of hypoxia, asphyxia, and ischemia on brain cortical oxidative metabolism. This study was carried out using 14 New Zealand White rabbits. The effects of episodic stress were measured simultaneously on brain functional metabolism by monitoring cortical oxygen tension (brain pO2), cortical cerebral blood flow (cCBF), cortical blood volume, and mitochondrial oxidative metabolism. During hypoxia (when the fraction of inspired O2 (FiO2) was reduced to 10%) and asphyxia (induced by turning the respirator off), there was a decrease of brain pO2 but an increase of cCBF and blood volume. Similarly, there was a reduction of cortical oxidative metabolism. In post-asphyxic conditions, an overshoot of brain pO2 and post-asphyxic oxidation of cytochrome (Cyt.) aa3 were usually shown. Under ischemic conditions (induced by sudden severe hypotension plus bilateral common carotid occlusion), cCBF and blood volume were decreased. There was also a decrease of brain pO2 and a reduction of Cyt. aa3 following ischemia. These techniques are applicable in intraoperative monitoring of patients.

Animals↗

PubMed1985

[Intra- and perioperative acoustic evoked brain stem potentials in cerebellopontile angle operations].

From a series of 35 cases with intraoperative monitoring of acoustic evoked brainstem responses 4 cases with cerebellopontine angle surgery are presented in detail. The aim of neuromonitoring is to provide the surgeon with an additional instrument to assess the functional state of the hearing pathway with objective neurophysiological criteria during dissection near the eighth nerve and brainstem. Thus, a near total loss of potential during a neurovascular decompression of the trigeminal nerve could be reversed by modifying the surgical procedure. In 2 cases of acoustic neurinoma with preserved wave I this peak was obtainable throughout the procedure with a good postoperative result. Transient amplitude attenuation and latency increase was seen with a meningioma, which normalized before the end of operation with good postoperative hearing and brain-stem function. The relationship between intraoperative BAEP changes and postoperative brain-stem and eighth nerve function, and the value of neuromonitoring are discussed with regard to surgery around the internal auditory meatus and the eighth nerve.

Adult↗

PubMed1997

Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve--preservation and restitution of function.

OBJECTIVE: Although the rate of reported facial nerve preservation after surgery for vestibular schwannomas continuously increases, facial nerve paresis or paralysis is a frequent postsurgical sequelae of major concern. The major goal of this study was to define criteria for the right indication, timing, and type of therapy for patients with palsies despite anatomic nerve continuity and those with loss of anatomic continuity. METHODS: One thousand vestibular schwannomas were surgically treated at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. Of 979 cases of complete removal and 21 cases of deliberately partial removal, the facial nerve was anatomically preserved in 929 cases (93%). The rate of preservation is increasing, as is evidenced in the most recent cases, and preservation is supported by special electrophysiological monitoring. The facial nerve was anatomically severed in 60 cases (6%). It was anatomically lost in previous operations that were performed elsewhere in 11 cases (1%). In case of nerve discontinuity (42 cases), immediate nerve reconstruction by one of three available intracranial procedures (within the cerebellopontine angle, intracranial-intratemporal, intracranial-extracranial) was performed in the same surgical setting. In case of loss of the proximal facial nerve stump at the brain stem, early reanimation by combination with the hypoglossal nerve was achieved in most patients within weeks after tumor surgery. In a few patients with anatomic nerve continuity but absence of reinnervation for 10 to 12 months, a hypoglossal-facial combination was applied. All the patients with partial or with complete palsies were treated in a special follow-up program of regular controls and of modulation of physiotherapeutic treatment every 3 to 6 months. RESULTS: In intracranial nerve reconstruction at the cerebellopontine angle, 61 to 70% of patients regained complete eye closure and an overall result equivalent to House-Brackmann Grade 3. Hypoglossal-facial reanimation led to Grade 3 in 79%. The duration between the onset of paralysis and the reconstructive procedure is decisive for the quality of the outcome. These data are discussed in view of other treatment options and certain parameters influencing outcome. CONCLUSIONS: This management contains three major principles as follows: 1) preservation of facial nerve continuity in function by the aid of intraoperative monitoring, 2) early nerve reconstruction in case of lost continuity, and 3) scheduled follow-up program for all patients with incomplete or complete palsies.

Adolescent↗

PubMed2001

Stimulation electromyography as a method of intraoperative identification of the recurrent laryngeal nerve in thyroid surgery.

INTRODUCTION: The iatrogenic injury of the recurrent laryngeal nerve during thyroid surgery still represents a major problem because of the great physiologic and psychologic trauma to the patients. The incidence of this complication ranges between 1% and 15% depending on the thyroid pathology and type of surgery. AIM: To evaluate the potential of stimulation electromyography as a method of intraoperative prophylaxis of iatrogenic injuries of the recurrent laryngeal nerve. MATERIAL AND METHODS: Intraoperative monitoring of the recurrent laryngeal nerve based on stimulation electromyography, which was introduced in the Clinics of Surgery and Otorhinolaryngology at the Higher Medical Institute in Plovdiv, was applied in thyroid surgery using Neurosign 100 (Magstim Company Ltd., Wales, UK) apparatus. The study involved 5 experimental dogs and 73 recurrent laryngeal nerves in 47 patients treated in the clinics from November 1, 1999 to February 15, 2000. RESULTS: In all experimental animals and patients the electrical stimulation was successful triggering an "M" response of the laryngeal muscles (the vocal muscle). A stable contact was achieved between the recording (needle) electrodes and the vocal folds. None of the patients had signs of laryngeal palsy or complaints other from the usual in endotracheal intubation. CONCLUSION: The results suggest that the intraoperative stimulation electromyography of the recurrent laryngeal nerve is a safe and effective method for evaluation of the nerve integrity during and at the end of the operation.

Adult↗

PubMed2004

Iatrogenic paraplegia in spinal surgery.

INTRODUCTION: Paraplegia as a result of a surgical spinal procedure is a rare complication. The risk cannot be precisely quantified due to the lack of current data. The aim of this study was to record a sufficiently large number of major spinal operations, especially extended methods in scoliosis surgery. Hereby, a reliable statement regarding the risk of severe neurological complications with these surgical techniques should be possible. First, a retrospective analysis of patients from a German spine centre (spinal fusion) and a survey of 17 German centres of spinal surgery were conducted for the retrospective acquisition of severe iatrogenic neurological complications. MATERIALS AND METHODS: The study included 1194 patients who underwent a spinal fusion during the period 1992-2002. The incidents of postoperative paraplegia are described in detail, and case studies done. Possible causes, methods of intraoperative monitoring and options of therapy are discussed according to research in relevant publications. Additionally, severe neurological complications of 3115 spinal operations were recorded in a standardised survey conducted throughout major German spinal centres. RESULTS: Of the 1194 patients surveyed, 7 (0.59%) experienced a postsurgical complete or incomplete paraplegia. In 3 of the recorded cases, the cause could be identified. The survey of 3115 scoliosis surgeries showed that iatrogenic paraplegia occurred with a frequency of 0.55%. The risks associated with short spinal fusions (0.14%), cervical discectomies (0.07%) and lumbar discectomies (0.03%) are considerably less. CONCLUSION: Operative treatment of scoliosis with a high degree of correction carries a risk of neurological complications of about 0.5%. Mechanical as well as ischaemic damage to the spinal cord can be detected early by means of consistent intraoperative neuromonitoring.

Adolescent↗

PubMed1996

Continuous retrograde monitoring of the facial nerve during cerebellopontine angle surgery: normative data.

An alternative technique for the continuous monitoring of the facial nerve, monopolar recording of facial nerve antidromic potentials (FNAPs), on 10 subjects undergoing retrosigmoid vestibular neurectomy for Meniere's disease is described. To elicit FNAPs bipolar electrical stimulation of the marginalis mandibulae was performed. Stimulus intensity ranged from 0 to 10 mA with a delivery rate of 7/second. Antidromic potentials were recorded with a silver wire monopolar electrode positioned intracranially on the proximal portion (root entry zone) of the acoustic-facial bundle. Bipolar recordings with two silver electrodes were also performed from different nerves in the cerebellopontine angle to define the specific origin of the action potentials. FNAP. amplitude increased as a function of stimulus intensity. The average latency was 3.35 milliseconds (range 3.0 to 3.7 ms). Action potentials recorded intracranially during electrical stimulation of the marginal nerve originated specifically from the facial nerve. FNAP recording is therefore a promising technique for the continuous intraoperative monitoring of the facial nerve during cerebellopontine angle surgery.

Journal Article↗

PubMed2003

Laser Doppler flowmetry in non-human primate stroke studies: model refinement for pre-clinical development of cerebroprotective strategies.

BACKGROUND: Safety, feasibility, and efficacy trials in non-human primate stroke models are essential to the evaluation of experimental therapies and their translation to humans. Although Laser Doppler Flowmetry has been successfully employed in rodent stroke to continuously monitor cerebral blood flow, it has not been applied in primate studies. This investigation examined the utility of Laser Doppler Flowmetry in refining an existing baboon model of cerebral ischemia/reperfusion. METHOD: Continuous Laser Doppler Flowmetry monitoring was used, in non-human primates, to document local cerebral blood flow before, during, and after middle cerebral artery territory occlusion. In each baboon (n = 7) a single Doppler probe was placed into the left frontal cortex through a precoronal burr hole. Correlations between Laser Doppler Flowmetry values and latencies to Motor Evoked Potential dropout were compared using a linear regression model. FINDINGS: Placement of the Laser Doppler probe was easily accomplished in all animals. Laser Doppler Flowmetry tracings accurately documented blood flow changes that occurred with each technical manipulation during the procedure. Laser Doppler confirmed decreased perfusion that coincided both regionally and temporally with vessel occlusion. Depth of ischemia as measured by Laser Doppler Flowmetry was associated with Motor Evoked Potential dropout latencies for individual animals. CONCLUSIONS: Continuous, single probe Laser Doppler Flowmetry is a reliable method of documenting perfusion changes following middle cerebral artery territory occlusion in a baboon model of reperfused stroke. This advanced intraoperative monitoring technique may lead to more accurate evaluation of acute stroke therapies in pre-clinical trials.

Animals↗

PubMed2000

Usefulness of quick intraoperative measurements of intact parathyroid hormone in the surgical management of hyperparathyroidism.

We investigated the use of quick measurement of intraoperative intact parathyroid hormone (I-PTH) to predict the outcome of parathyroidectomy. We examined intraoperative monitoring of I-PTH in 34 consecutive primary hyperparathyroidism (pHPT) patients operated on between April and December 1999. The average patient age was 56 +/- 13 years, and all but one were women. Four had a history of thyroidectomy. Blood samples were drawn before excision of enlarged parathyroid gland(s) and at 2, 5, 10, and 15 minutes afterward. Plasma I-PTH was measured by a two-site immunochemiluminometric assay. Twenty-three patients were shown to have single gland disease, and ten had multiglandular disease. All patients, except one, underwent successful parathyroidectomies. The plasma I-PTH value 15 minutes after removal of enlarged gland(s) had dropped to 26 +/- 10% of pre-excision I-PTH value. In one patient with a previous history of thyroidectomy for thyroid papillary cancer, no gland enlargement was found in the area where the lesion had been suggested by both ultrasonography and 99mTc sestamibi scanning. In this case, intraoperative measurements of I-PTH in the bilateral internal jugular veins identified an ectopic parathyroid tumor, which was successfully removed. We conclude that quick measurement of intraoperative I-PTH is a valuable tool for decision-making, especially for reoperative parathyroid surgery, for patients with previous history of thyroidectomy, and for patients in whom unilateral neck exploration or a single-gland approach is scheduled based upon preoperative localization.

Female↗

PubMed1987

Electrical activity in the heart during hyperkalemic hypothermic cardioplegic arrest: site of origin and relationship to specialized conduction tissue.

Previous studies from this laboratory have shown that low-amplitude electrical activity (LEA) may occur during standard hyperkalemic hypothermic cardioplegic arrest and be undetected by routine monitoring techniques. The present study was designed to elucidate the electrophysiological nature of LEA. Ten dogs were monitored continuously during standard cardioplegic arrest using a 32-channel data acquisition system. In 7 animals (Part I), electrophysiological mapping of the lower right atrial septum during arrest was performed. The initial site of activation of LEA was consistently recorded from the region of the lower atrial septum prior to atrial or ventricular electrical activation. The site of origin of LEA was thus localized to the anatomical region of the atrial septum containing the atrioventricular nodal conduction tissue. In Part II, the electrophysiological mechanism of LEA was investigated in the remaining 3 animals utilizing an intrinsic property of specialized conduction tissue. Inclusion of a calcium channel-blocking agent in standard cardioplegic solution completely prevented the development of LEA in all 3 animals, which is in contrast to findings in previous studies using standard cardioplegic solution alone. These data suggest that LEA may be related to calcium-mediated activation of specialized conduction tissue. This mechanism of activation may explain why LEA cannot be detected by the intraoperative monitoring techniques routinely employed.

Animals↗

PubMed1987

The use of VEPs for CNS monitoring during continuous cardiopulmonary bypass and circulatory arrest.

Cerebral function was monitored with the use of visual evoked potentials (VEPs) in 16 infants (mean age 9.9 +/- 4.3 months) during surgery for congenital cardiac anomalies. While hypothermia was employed in all patients, half (8) remained on continuous cardiopulmonary bypass (CCB) while the rest were cooled to lower temperatures before the induction of circulatory stasis and venous exsanguination (CA), i.e., profound hypothermic circulatory arrest (PHCA). VEPs were recorded before, during and after surgical intervention. Latency changes occurred in both the N100 and P145 components of the VEP as a function of systemic temperature during cooling in both groups. Differences in the VEPs were found between the two groups post-operatively, with the most interesting result being a greater increase in P145 latency in the CA group after rewarming. To the extent that VEPs reflect neurological status, our findings suggested that CCB was associated with less perturbation in acute neurological status than PHCA, and shorter arrest times and lower temperatures during CA were associated with the most favourable post-operative VEPs. Hence, intraoperative monitoring of VEPs appeared to be useful as an objective measure of the short-term effects of various cardiopulmonary procedures on neurophysiological function.

Brain↗

PubMed1980

Pulmonary shunting during leukoagglutinin-induced noncardiac pulmonary edema.

Noncardiogenic pulmonary edema occurred in an anesthetized patient during an otherwise uneventful laparotomy. Following transfusion of an individual unit of whole blood, routine intraoperative monitoring detected sudden major pulmonary shunting (increased alveolar-arterial oxygen gradient) and an increased physiological alveolar dead space (increased arterial-alveolar carbon dioxide gradient). The noncardiac pulmonary edema probably resulted from the presence of a leukoagglutinin against the patient's granulocytes in the donor's plasma. This antibody had no apparent specificity for known HLA, neutrophil, or blood group antigens. The acute respiratory failure was transient, resolving in 72 hours with respiratory support. The presence of otherwise unexplained noncardiogenic pulmonary edema during or soon after a blood transfusion should suggest the possible diagnosis of a leukoagglutinin reaction.

Agglutinins↗

PubMed1984

Monitoring of multimodality evoked potentials during open heart surgery under hypothermia.

Multimodality evoked responses (ERs) were monitored in 16 adults who had cardiac surgery under cardiopulmonary bypass and moderate hypothermia (19-25 degrees C). Cooling affected all sensory ERs by progressively increasing the latencies of the major components. The effect was more profound on the later than on the earlier ER components. Visual evoked responses (VERs) were most inconsistent and always disappeared at temperatures below 25 degrees C. The later components of the long latency somatosensory evoked responses (SERs) also attenuated or disappeared rather early during hypothermia. On the other hand, short latency SERs were more resistant to the effects of hypothermia. They were always recordable at temperatures of 25 degrees C or above; and usually persisted even at temperatures between 20 and 25 degrees C. Brain-stem auditory evoked responses (BAERs) were consistently present at temperatures above 25 degrees C, wave V was recordable in majority between 20 and 25 degrees C. All sensory ERs disappeared with severe hypothermia (20 degrees C or less) except the components generated more peripherally such as N10 of the short latency SERs. We feel that BAERs and short latency SERs may serve as useful intraoperative monitors of brain function during hypothermia.

Adult↗

PubMed2002

Effect of thoracic epidural anaesthesia on colonic blood flow.

BACKGROUND: The effect of thoracic epidural block on splanchnic blood flow is unclear. It remains to be resolved if sympathetic block, increases or decreases regional splanchnic blood flow and whether regional splanchnic flow becomes dependent on cardiac output or perfusion pressure. A clear understanding of the regional haemodynamic consequences of an epidural block may modify practice with respect to epidural anaesthesia. METHODS: Fifteen patients, who underwent anterior resection for rectal cancer, had invasive intraoperative monitoring of arterial pressure, central venous pressure, cardiac output, inferior mesenteric artery flow (Doppler flow probe), and colonic serosal red cell flux (laser Doppler probe), while an epidural block was established with local anaesthetic. In three consecutive time periods, arterial pressure was first allowed to fall (to a mean arterial pressure of 60 mm Hg), then treated with colloid fluid resuscitation and finally by vasopressors until the pre-epidural arterial pressure had been restored. RESULTS: On induction of epidural block, there was a reduction in mean colonic serosal red cell flux to 65% and inferior mesenteric artery flow to 80% (mean) of pre-epidural levels. There was a strong association between mean arterial pressure and both measured inferior mesenteric artery blood flow (P < 0.004) and colonic serosal red cell flux (P < 0.0001). Changes in cardiac output were poorly associated with either inferior mesenteric artery blood flow (P = 0.638) or colonic serosal red cell flux (P = 0.265). Inferior mesenteric artery blood flow and colonic serosal red cell flux were restored to pre-epidural levels after arterial pressure had been improved with a vasopressor. CONCLUSION: Once intraoperative epidural block has been established, colonic serosal red cell flux and inferior mesenteric artery flow are more closely associated with changes in mean arterial pressure than changes in cardiac output. The measured reduction in colonic flow does not respond to an increase in cardiac output with fluid resuscitation, but requires the use of a vasopressor to increase arterial pressure, before colonic blood flow is improved.

Aged↗

PubMedDate not supplied

[Changes in blood calcium during liver transplant in children].

We have evaluated the changes in plasma total and ionic calcium levels in twenty hepatic transplantations in pediatric patients. Direct intraoperative monitoring of ionic calcium is fundamental, because its variability is unrelated with total calcium levels; in addition, normal ionic calcium levels contribute to the hemodynamic stability of the patient. Although at the end of the operation total and ionic calcium levels were similar to the postinduction measurement, their values were dissociated in the perianhepatic period. In the anhepatic phase ionic calcium reached its lowest value (1.00 mmol/l) although total calcium increased above postinduction level from 2.13 to 2.46 mmol/l (p less than 0.05). In hepatic transplantation in pediatric patients calcium administration is indicated during the transfusion of citrated blood, being particularly necessary during the anhepatic phase to prevent ionic hypocalcemia.

Adolescent↗

PubMed1996

[Clinical experience of laryngeal mask airway combined with continuous intravenous propofol infusion during general anesthesia].

BACKGROUND: Propofol's greatest attributes are its pharmacokinetic properties which result in a rapid, clear emergency and lack of cumulative effects even after prolonged administration. It is a drug of popular choice for the maintenance of general anesthesia. The laryngeal mask airway (LMA), originally described by Dr. Brain is now a good alternative as the airway management technique. Because of its high success rate in securing a clinically acceptable airway in anesthetized patients, LMA has been proposed as a practical airway and conveyer for general anesthesia. This study was designed to observe and evaluate the feasibility of propofol infusion combined with N2O for maintenance of anesthesia, with a LMA as airway and conveyer during general anesthesia. METHODS: Sixty patients, ASA class I-II, aged 15-59 years, were selected for this study. They were scheduled for upper-limb orthopedic surgeries in supine position. No patient was premedicated. Intraoperative monitoring included electrocardiography, pulse oximetry, end-tidal carbon dioxide and automatic non-invasive blood pressure. The agents for induction of anesthesia included atropine 0.01 mg/kg, atracurium 5 mg, fentanyl 2-3 micrograms/kg, 2% lidocaine 1.5-2 mg/kg, propofol 2 mg/kg, and succinylcholine 1-1.5 mg/kg, all of which were given intravenously in sequence. After that laryngeal mask airway (LMA) was inserted. The position of LMA was confirmed by even undulation of chest wall and breathing sound. Anesthesia was then maintained with nitrous oxide in 40% oxygen and continuous propofol infusion. The pumping rate was set to start at 6 mg/kg/h. Muscle relaxation was achieved by intravenous tracrium given intermittently. All patients were mechanically ventilated with a ventilator incorporated to the anesthesia machine. The ventilator was set to give a tidal volume of 8 ml/kg at a rate of 12-14/min. At the end of the operation, the propofol infusion and nitrous oxide were simultaneously discontinued. The effect of muscle relaxant was antagonized by atropine 1.0 mg and neostigmine 2.5 mg intravenously. The LMA was removed while the patient was awake and able to open mouth at request. They were followed 24 h postoperatively for inquiring intraoperative awareness and other complaints. RESULTS: No patient was noted to experience awareness during the intraoperative period. Regarding LMA insertion, success in the first attempt was seen in 55 patients (90.2%). Success in the second attempt was seen in 5 patients (8.2%). Failure was encountered in one patient (1.6%). The average time of emergence was 92 +/- 3.4 min. The average rate of speed of propofol infusion was 6.29 +/- 0.97 mg/kg/h. CONCLUSIONS: The combination of propofol infusion and N2O with laryngeal mask as airway and recovery was a good alternative in administration of general anesthesia.

Adolescent↗

PubMed1999

Effect of compression on the cochlear nerve: a short- and long-term electrophysiological and histological study.

The short- and long-term effects of static compression of the cochlear nerve were studied in dogs. The nerve was exposed in the cerebellopontine angle and a modified aneurysm clip was applied to reduce the diameter of the nerve trunk to 50%, 40%, 30% or 20% of normal (designated respectively as 50%, 60%, 70%, and 80% compression). Brainstem auditory evoked potentials (BAEPs) were monitored intraoperatively and post-operatively. The animals were sacrificed between 5 and 119 days after nerve compression and temporal bones were examined histologically. In the 50% compression group, all peaks except peak I disappeared immediately after nerve compression. After release of the clip, however, peak II and subsequent components recovered and prolonged interpeak latency (IPL) between peaks I and IV normalized within 7 days. In the 60% compression group, recovery was incomplete for as long as 49 days after compression. Significant histological changes were not always reflected in the electrophysiological recordings, as shown by the finding of multiple cavitations at the compressed portion of the cochlear nerve in cases in which conduction block of cochlear nerve impulses was reversible. In the 70% compression group, peak IV did not reappear for more than 1 week, and histological examination revealed severe damage to all cochlear nerve fibers except those from the apical turn, which lie in the center of the cochlear nerve trunk. Severe injury occurred to the cochlear nerve fibers that are situated more superficially in the nerve, which are tonotopically responsible for the perception of high-frequency sound and the generation of BAEPs. This means that the BAEP changes due to cochlear nerve compression would be detectable by BAEP monitoring, although changes in the apical region of the cochlea are not fully detectable by BAEP monitoring. In the 80% compression group, all peaks except peak I were lost permanently and the amplitude of peak I, which had been preserved in the acute phase, gradually decreased. Reversibility of impaired cochlear nerve impulse conduction was related to the severity of compression, and at some level of compression between 70% and 80% the nerve fibers generating BAEPs permanently lost the ability to conduct electrical impulses proximal to the site of compression. In the 70% and 80% compression groups, the amplitude of peak I gradually decreased over the first 30 days after compression and did not change significantly thereafter. Histologically, the branches of the internal auditory artery were resilient to compression, although they are easily avulsed due to stretch force. Furthermore, retrograde degeneration of cochlear neurons triggered by compression at the cisternal portion of the cochlear nerve was apparent. Such slowly progressive degeneration of nerve fibers may play a part in development of the delayed postoperative hearing disturbance.

Animals↗