Multi-frequency electrical impedance tomography (EIT) of the adult human head: initial findings in brain tumours, arteriovenous malformations and chronic stroke, development of an analysis method and calibration

MFEIT (multi-frequency electrical impedance tomography) could distinguish between ischaemic and haemorrhagic stroke and permit the urgent use of thrombolytic drugs in patients with ischaemic stroke. The purpose of this study was to characterize the UCLH Mk 2 MFEIT system, designed for this purpose, with 32 electrodes and a multiplexed 2 kHz to 1.6 MHz single impedance measuring circuit. Data were collected in seven subjects with brain tumours, arteriovenous malformations or chronic stroke, as these resembled the changes in haemorrhagic or ischaemic stroke. Calibration studies indicated that the reliable bandwidth was only 16-64 kHz because of front-end components placed to permit simultaneous EEG recording. In raw in-phase component data, the SD of 16-64 kHz data for one electrode combination across subjects was 2.45 +/- 0.9%, compared to a largest predicted change of 0.35% estimated using the FEM of the head. Using newly developed methods of examining the most sensitive channels from the FEM, and nonlinear imaging constrained to the known site of the lesion, no reproducible changes between pathologies were observed. This study has identified a specification for accuracy in EITS in acute stroke, identified the size of variability in relation to this in human recordings, and presents new methods for analysis of data. Although no reproducible changes were identified, we hope this will provide a foundation for future studies in this demanding but potentially powerful novel application.

The sitting position for neurosurgery in children: a review of 16 years' experience

BACKGROUND

Use of the sitting position for neurosurgery is controversial. The main concern is the risk of venous air embolus (VAE) and its sequelae.

METHODS

The paediatric neurosurgeons at our institution routinely use the sitting position for posterior fossa and pineal surgery, and a retrospective audit of the incidence of VAE from 1982 to 1998 has been performed.

RESULTS

Venous air embolism, defined as a fall in end-tidal carbon dioxide pressure >0.4 kPa, was detected in 38 of 407 operations (9.3%). A fall in systolic arterial pressure >10% accompanied the VAE in nine out of 43 episodes (20.9%); this represents 2% of all operations. All VAE episodes responded promptly to treatment and there was no perioperative morbidity or mortality directly attributed to it.

CONCLUSIONS

This is the largest study of the incidence of VAE in children undergoing neurosurgery. Our results suggest that the sitting position can be used safely for neurosurgery in children.

Carcinoid syndrome symposium on treatment modalities for gastrointestinal carcinoid tumours: symposium summary

OBJECTIVE

To develop a collaborative approach for the treatment of gastrointestinal carcinoid tumours and carcinoid syndrome.

PARTICIPANTS

Leaders in the medical, endocrine, radiologic and surgical treatment of carcinoid disease were selected to present papers at the Carcinoid Syndrome Symposium on Treatment Modalities for Gastrointestinal Carcinoid Tumours and participate in the workshop that followed.

EVIDENCE

A multidisciplinary symposium with experts in the field of carcinoid syndrome was organized at the University of Calgary. Data presented, participation of the attendees and a review of the literature were used in the workshop to develop a collaborative approach to the management of carcinoid tumours.

BENEFITS

Carcinoid tumours are rare and few centres have large experiences in their treatment. Before the development of this collaboration, patients with carcinoid tumours received a unidisciplinary approach depending on referral patterns. The development of a multidisciplinary neuroendocrine clinic helped to unify the approach to these patients, yet a consensus on the treatment of carcinoid tumours was lacking. The expertise at the symposium allowed for consensus and the development of treatment algorithms, including biochemical screening, radiographic localization and surgical intervention, for gastrointestinal carcinoid tumours. The role of medical and hormonal therapy after cytoreducion is presented.

RECOMMENDATION

Patients with carcinoid tumours require a multidisciplinary approach to their care.

A comparison of rectal and intramuscular codeine phosphate in children following neurosurgery

Codeine is frequently used for postoperative analgesia in children. Intramuscular injections are not ideal and the rectal route may be preferable. We compared rectal and intramuscular codeine administered following neurosurgery. 20 children (over 3 months) undergoing elective neurosurgical procedures, were randomized to receive either rectal or intramuscular codeine phospate (1 mg.kg-1) at the end of the procedure. Serum levels of codeine and morphine were assayed at intervals following administration (0, 30, 60, 120, 240 min). Fentanyl was the intraoperative analgesic and postoperative rescue analgesia was paracetamol, diclofenac and intramuscular codeine. The Children's Hospital of Eastern Ontario Pain Scale was used to assess analgesia. Peak codeine levels in both groups were observed at 30 min and morphine levels were consistently low. The plasma codeine levels were significantly greater at 30 and 60 min following intramuscular injection, and were associated with slightly better analgesia scores, but did not reach statistical significance. However, the peak plasma level occurred at similar times in both groups. Codeine is absorbed as rapidly via the rectal route compared with the intramuscular route but the peak levels are lower.

Analgesic doses of fentanyl impair oxidative metabolism of neonatal hepatocytes

BACKGROUND/PURPOSE

Studies in human surgical neonates have shown that intraoperative fentanyl analgesia results in greater fall in perioperative body core temperature compared with morphine analgesia. The aim of the study was to compare in a neonatal animal model the biochemical effect of fentanyl and morphine on hepatocyte oxidative metabolism.

METHODS

Hepatocytes were isolated from suckling rats and the oxygen consumption from palmitate was measured polarographically. In experiment A, fentanyl and morphine within the respective analgesic serum ranges were added to hepatocytes to assess the effect on oxygen consumption. In experiment B, fentanyl was added to hepatocytes in the presence of inhibitors of mitochondrial respiration to investigate its site of action. In experiment C, hepatocytes were incubated with either fentanyl or morphine, centrifuged, and then examined ultrastructurally by electron microscopy.

RESULTS

In experiment A, fentanyl inhibited oxygen consumption by up to 40% (P < .01). Morphine inhibited oxygen consumption to a maximum of 25% (P < .01). In experiment B, in the presence of oligomycin, fentanyl increased the inhibition of oxygen consumption; however, in the presence of myxothiazol, no further inhibition by fentanyl occurred. In experiment C, mild ultrastructural alterations to hepatocytes were observed after incubation with fentanyl but not with morphine.

CONCLUSIONS

This study demonstrates that therapeutic doses of two commonly used analgesic drugs impair neonatal hepatic oxidative metabolism. Fentanyl exerts a greater effect than morphine by diminishing liver oxygen consumption by up to 40%. The inhibitory effect of fentanyl occurs directly on the mitochondrial respiratory chain, either on substrate oxidation or on the thermogenic proton leak. The findings of this study are relevant to the perioperative management of surgical neonates.

The anaesthetic management of a case of Kawasaki's disease (mucocutaneous lymph node syndrome) and Beckwith-Weidemann syndrome presenting with a bleeding tongue

An unusual case of a 13-month-old child with Kawasaki's disease and the Beckwith-Weidemann syndrome is presented. The child, while anticoagulated with warfarin and aspirin to prevent extension of a coronary artery thrombus, fell and lacerated the tongue resulting in haemorrhage and significant swelling. The ongoing haemorrhage, combined with difficulty in securing venous access resulted in the child becoming shocked. Surgical intervention was required to stem the haemorrhage. The anaesthetic management of a shocked child with a coronary artery aneurysm and thrombosis, a potentially difficult airway and a full stomach is described.

Fentanyl analgesia increases the incidence of postoperative hypothermia in neonates

Postoperative hypothermia remains a clinical problem in neonates undergoing surgery. Intraoperative analgesia can blunt the metabolic and hormonal response to operative stress in neonates. However, its effects on heat production and thermoregulation are not known. The aim of this review was to characterise the effects of intraoperative analgesia on body temperature in neonates undergoing surgery. The case notes of 25 consecutive neonates who underwent major operations were retrospectively reviewed. Axillary temperature was measured before the operation, and postoperatively after returning to the neonatal intensive care unit (NICU). Patients were divided into groups based on the intraoperative analgesic used: (1) 9 neonates received fentanyl; (2) 5 received morphine; and (3) 11 received epidural bupivacaine. All groups were comparable in terms of conceptional age, postnatal age, body weight, duration of operation, and operative stress score. In all groups the body temperature was significantly lower at the time of returning to the NICU than preoperatively. Three patients (33%) who received fentanyl became hypothermic during the operation, whereas none of those who received either morphine or bupivacaine had hypothermia. The drop in temperature between preoperative and initial postoperative values was significantly greater in patients who received fentanyl intraoperatively (median drop 0.8 degreesC, range 0.6 - 2.4) when compared with patients who received morphine (P = 0.02) or epidural bupivacaine (P = 0.01). These data suggest that intraoperative fentanyl modulates the postoperative body temperature in neonates. We hypothesise that fentanyl blocks metabolic heat production, which results in a reduction in postoperative body temperature.

Functional caudate imaging in symptomatic Huntington's disease: positron emission tomography versus single-photon emission computed tomography

Functional neuroimaging with positron emission tomography previously demonstrated reduced caudate glucose metabolism in virtually all symptomatic patients with Huntington's disease (HD). Single-photon emission computed tomography studies of brain blood flow also have shown caudate abnormalities in patients with HD. The present study compared these two functional imaging modalities in 6 patients with HD who had been symptomatic for fewer than 5 years. All patients had significantly impaired caudate-thalamus and caudate-whole-slice glucose metabolism ratios as measured by positron emission tomography. However, only 3 had clearly abnormal caudate-thalamus activity ratios and 2 had clearly abnormal caudate-whole-slice ratios on single-photon emission computed tomography. These findings indicate that single-photon emission computed tomography imaging of caudate blood flow is a less sensitive indicator of caudate dysfunction in early HD than is positron emission tomography imaging of caudate glucose metabolism.

Does gallium uptake in the pulmonary hila predict involvement by non-Hodgkin's lymphoma?

67Ga imaging of non-Hodgkin's lymphoma is useful for evaluating the presence of viable tumour in a residual mass after treatment. However, we have frequently seen gallium uptake in the pulmonary hila without other evidence of lymphoma. To study the significance of this finding, 79 patients with intermediate grade non-Hodgkin's lymphoma were reviewed. Thirty-seven (47%) had abnormal hilar gallium uptake. Twenty-three of these could be fully evaluated, and only five (22%) had hilar lymphoma. A pattern of bilateral, symmetric hilar uptake was seen in 19 patients, but only one had evidence of lymphoma. In 15 cases, this pattern was seen only on single photon emission computed tomography (SPECT). The aetiology of this uptake remains unknown. It is not treatment related, as 12 patients had hilar gallium uptake prior to chemotherapy. Unless confirmed by other methods, hilar gallium uptake should not be attributed to lymphoma, and should not influence patient management.

Giant false aneurysm of the subclavian artery. An unusual complication of internal jugular venous cannulation

A false aneurysm with a diameter of 15 cm developed in the wall of the subclavian artery after attempted internal jugular cannulation. This potentially lethal complication, its diagnosis and treatment are described.