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Biomedical subjects

M Petermeyer

Publications and source records attributed to M Petermeyer.

6 recordsLinked to original sources
PubMed2000

Advanced image-guided skull base surgery.

BACKGROUND: Tumors of the skull base frequently encase or extend into normal neural and vascular structures. Preoperative planning and intraoperative identification of anatomic landmarks is especially important in complex tumors since it helps avoid or minimize surgical morbidity. METHODS: By creating a surgical plan the image guidance software offers help in the establishment of a surgical approach. During surgery, the neuronavigation system displays the location of anatomic landmarks of the skull base regardless of any erosion or displacement. RESULTS: A series of 10 patients with complex tumors in various skull base locations is reported. Osseous structures are easily identified using the CT-based image guidance since these landmarks do not shift due to CSF loss. Image fusion of CT and MRI data gives additional information on the displacement of soft tissue structures. Image fusion in a substraction mode is helpful when a tumor has invaded bony structures or when the encasement of major vessels has to be visualized. CONCLUSION: The preoperative data preparation (planning of the approach, image fusion) plays a vital role in modern neuronavigation and contributes useful information during surgery for complex skull base tumors. Such advanced neuronavigation increases the efficacy and safety of intraoperative maneuvers. Eroded and distorted anatomic landmarks are not subject to a significant amount of intraoperative shift throughout the surgical procedure.

Adult↗
PubMed1999

Aneurysm of the posterior inferior cerebellar artery caused by a traumatic perforating artery tear-out mechanism in a child.

Traumatic posterior circulation aneurysms in the absence of fractures and penetrating wounds are extremely uncommon, especially in children. To our knowledge this is the first traumatic posterior inferior cerebellar artery(PICA) aneurysm reported that cannot be related to a skull fracture or a trauma caused by the edge of a rigid meningeal structure. In the present case, the initial subarachnoid hemorrhage (SAH) was caused by a perforating artery, originating from the PICA, which was torn out as the result of a deceleration trauma. Such a mechanism explains both the initial SAH and the development of the false aneurysm responsible for the second SAH.

Aneurysm, False↗
PubMed1998

Management of aneurysms of the vertebral artery-posterior inferior cerebellar artery complex.

Aneurysms of the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) account for only about 3% of all diagnosed intracranial aneurysms. The surgical therapy of these aneurysms is complex and difficult due to the close topographical relationship between the neurovascular structures. Here, we report upon 27 patients with 29 such aneurysms. Of these, 22 patients (81%) were hospitalized because of a subarachnoid hemorrhage. Sixteen of these patients (72%) had an additional intraventricular hemorrhage. Twenty-one patients (78%) were surgically treated for their aneurysms, three of them also for an associated arteriovenous malformation. Aneurysms of the VA and the proximal PICA were exposed via a transcondylar (n = 11) or lateral suboccipital (n = 3) approach, those originating from the distal PICA via a paramedian suboccipital (n = 7) route. Endovascular therapy was used in three patients. A patient with a fusiform aneurysm of the vertebrobasilar junction was treated with a ventriculoperitoneal shunt only. Three aneurysms with a complex morphology were not treated. Of the patients operated upon, two died postoperatively due to vasospasm. Two other patients developed an incomplete dorsolateral medullary syndrome. One individual was lost for follow-up. The median follow-up period was 4.6 years (range 3-86 months). Both, the overall mortality (2/27) and morbidity (2/27) were 7.5%, respectively. Our results show that even complex vascular lesions of the posterior fossa can be treated with a satisfactory long-term outcome in the majority of our patients (85%). The multimodal management and an individually tailored microsurgical approach are key issues for the treatment of such aneurysms.

Adult↗
PubMed1997

[Low-flow anesthesia with desflurane].

OBJECTIVES: Due to its low solubility and negligible metabolism, desflurane is assumed to be especially suitable for application by low-flow anaesthetic techniques. The aim of this clinical investigation was the development of a standardised dosing scheme for low-flow and minimal-flow desflurane anaesthesia. METHODS: One hundred six ASA status I-II patient were assigned to six groups according to the duration of the initial high-flow phase, fresh gas flow, and fresh-gas desflurane concentration. The median age, height, body weight, and constitution of the groups was comparable. After an initial high-flow phase using 4.4 l/min, the fresh gas flow was reduced to 0.5 l/min (minimal-flow anaesthesia) or 1.0 1/min (low-flow anaesthesia). Inspired nitrous oxide concentrations were maintained at 60% to 70%. Using different standardised schemes of vaporizer settings, inspired desflurane concentrations were applied in the range from 3.4% to 8.7%, i.e., between 1 and 1.5 MAC. Inspired and expired desflurane concentrations were measured continuously by the side-stream technique and recorded on-line. Venous blood samples were taken immediately prior to induction and 45 min after flow reduction for measurement of carboxyhaemoglobin (COHb) concentration). RESULTS: In the 10- to 15-min initial phase during which a high fresh gas flow of 4.4 l/min was used, the inspired desflurane concentration reached values in the range of 90%-95% of the fresh gas concentration. In low-flow anaesthesia this concentration could be maintained without any alteration of the vaporizer setting, whereas in minimal-flow anaesthesia with flow reduction the fresh gas concentration had to be increased by 1% to 2%: The quotient calculated by division of the inspired desflurane concentration by its fresh gas concentration (Q = CI/CF) ranges between 0.65 and 0.75 in animal-flow and between 0.80 and 0.85 in low-flow anaesthesia. If use was made of the wide output range of the desflurane vaporizer, the inspired concentration could be increased rapidly by about 5% in 8 min, although the flow was kept constant at 0.5 l/min. Compared with its value prior to induction (2.13 +/- 1.05%), the COHb concentration decreased statistically significantly by about 0.7% during the 1st hour of minimal-flow anaesthesia (1.42 +/- 1.01%). In no case was a COHb concentration observed that exceeded threatening or even toxic values, although the soda lime was changed routinely only once a week. CONCLUSIONS: The pharmacokinetic properties of desflurane, resulting in especially low individual uptake, and the wide output range of the vaporizer facilitate the use of low-flow anesthetic techniques in routine clinical practice. Even in minimal-flow anesthesia, the duration of the initial high-flow phase can be shortened to min. If the flow is reduced to 1 l/min, the inspired desflurane concentration achieved in the initial high-flow phase can be maintained without any alteration of the vaporizer setting. In minimal-flow anesthesia, however, with flow reduction to 0.5 l/min, the fresh gas concentration has to be increased to a value 1%-2% higher than the inspired nominal value. Due to the wide dialing range of the desflurane vaporizer, the amount of vapour delivered into the breathing system can be increased to about 110 ml/min even at a flow of 0.5 l/min. The large amount of agent that can be delivered into the system even under low-flow conditions, together with the very low individual uptake, results in a time-constant that is sufficient short for the clinically required rapid increase in inspired desflurane concentrations. The short time-constant of low-flow desflurane anaesthesia improves the control of the anaesthetic concentration. If all measures are taken to safely avoid inadvertent drying out of the soda lime, there is no evidence that low-flow anaesthesia with desflurane is liable to increase the risk of accidental carbon monoxide poisoning. (ABSTRACT TRUNCATED)

Adult↗
PubMed1996

[Incidence and quality of dreaming during anesthesia with propofol in comparison with enflurane].

UNLABELLED: Since the introduction of propofol into clinical practice, dreaming during general anaesthesia has been frequently reported with this drug. We investigated the incidence and character of these dreams with regard to distinction from intraoperative awareness and in comparison with habitual dreams or dreams during general anaesthesia with enflurane. METHOD: A total of 230 patients (ASA I-II) undergoing minor elective surgery were randomly assigned to one of two groups. Both groups received the same premedication (1 mg flunitrazepam) the previous evening. After induction using etomidate 2 mg/kg, anaesthesia in group I was maintained using 0.8%-1.5% enflurane supplemented in the sense of "balanced anaesthesia" with fentanyl, vecuronium, and nitrous oxide. Anaesthesia in group II was induced with propofol 2 mg/kg. After a saturation phase of approximately 10 mg/kg.h, 5-6 mg/kg.h was administered for maintenance supplemented by fentanyl, Vecuronium, and N2O as in group I. Interviews were conducted preoperatively, just after recovery from anaesthesia, and 24 h later. We inquired about preoperative fears or concerns, sensory perceptions, and the incidence and character (pleasant, unpleasant, indifferent) of habitual dreams. After recovery the patients were asked if they had had any conscious perceptions, whether they believe them to be dreams or reality, and repeated the preoperative questions as to common feelings and the character of sensory perceptions. RESULTS: The two groups were not entirely comparable due to the distribution of sex and age, but we did not find any differences in preoperative grades of fear and incidence of dreams. Of the propofol patients, 60% dreamed intraoperatively versus 11% in the enflurane group. No evidence of any intraoperative awareness was found. Because of the low incidence of dreams in the enflurane group, a comparison of detailed information between the groups could not be provided. Except for 1, all patients in the propofol group had very pleasant dreams compared to their habitual dreams (4.5% in the enflurane group). One day after surgery 37% of all patients in the propofol group remembered having dreamed intraoperatively. We did not found any correlation to the incidence of habitual dreaming, preoperative fear, age, sex, duration of anaesthesia, or total dose of propofol. Furthermore, intraoperative dreams differed from habitual dreams in character and content. CONCLUSIONS: We conclude that sensory experiences during propofol anaesthesia are not stimulus-related perceptions or awareness, but dreams similar to normal ones. In view of the absence of clear signs of stimulus-related response, we presume that dreaming is a specific side effect of propofol. Because of the absence of difficulties, dreaming during propofol anaesthesia appears not to be a disadvantage with regard to the quality of anaesthesia.

Adult↗