The assessment of fetal brain growth in diabetic pregnancy using in utero magnetic resonance imaging.

AIM: To assess fetal brain growth over the third trimester in pregnant women with diabetes using in utero magnetic resonance imaging (iuMRI) to determine if greater brain growth occurs in type 1 (T1DM) when compared to gestational (GDM) diabetes mellitus. MATERIALS AND METHODS: Each consented participant was scanned at three fixed times during the third trimester using iuMRI. One hundred and fifty-seven patients were approached, 48 participants were recruited, and 36 complete data sets were analysed. Three-dimensional (3D) iuMRI volume data sets were manually segmented using software to construct models of the fetal brain from which brain volumes could be calculated. Inter-rater analysis was performed, and volume differences and growth rates were compared between T1DM and GDM. RESULTS: Recruitment proved difficult with low uptake and high attrition rates (77.1%). Inter-rater analysis revealed excellent correlation (intraclass correlation coefficient=0.93, p<0.001) and agreement with no significant difference between operators (p=0.194). There was no evidence of increased brain volume in the T1DM group. Growth rates between visit 1 and 3 for T1DM and GDM were not significantly different (p=0.095). CONCLUSION: T1DM brain volumes were not significantly larger than GDM volumes and there was no significant divergence of brain growth over the third trimester. Constructing volume models from 3D iuMRI acquisitions is a novel technique that can be used to assess fetal brain growth. No specialist software or knowledge is required. Larger studies attempting to recruit pregnant women in the later stages of pregnancy should employ multicentre recruitment to overcome recruitment difficulties and high attrition rates.

Surface reconstructions of foetal brain abnormalities using ultrafast steady state 3D acquisitions.

MRI of the foetal brain in utero is performed in routine clinical practice using sequences that produce two-dimensional (2D) images. Recent developments in image post-processing have allowed the construction of three-dimensional (3D) volume data sets from 2D images acquired in different anatomical planes, but these have limitations due to the unpredictable nature of foetal movement. These limitations have been overcome by development of several different advanced computer techniques, which require specialist knowledge, software, and processing methods, which are rarely available in routine clinical settings. Our aim was to develop a technique that can be used in routine clinical situations without the need for custom-developed or expensive software by utilizing MRI sequences that can produce a 3D data set in "ultrafast" timescales. The 3D dataset, combined with versatile image post-processing and visualization techniques, has resulted in the production of high-resolution images of foetal brain surfaces in utero. The aim of this paper is to demonstrate our methods and early results by way of a pictorial review illustrating a range of developmental brain disease in utero.

Age is the best predictor of postoperative morphine requirements.

The dose of opioid prescribed for postoperative pain relief has traditionally been based on the weight of the patient. Although a reduction in dose is often suggested for elderly patients over 70 years of age, age-related alterations to dose are generally not considered for younger patients. The records of 1010 patients, under 70 years old, prescribed morphine via patient-controlled analgesia (PCA) after major operations were examined to see what factors might best predict the amount of morphine used in the first 24 h after surgery. Factors included were age, sex, weight, operative site, verbal numeric pain score (at rest and on movement) and a nausea/vomiting score. In a subgroup of 78 of these patients, the effects of intraoperative and recovery room doses of opioid ('clinical' loading dose) were analysed. Although the interpatient variability in PCA morphine doses was large (differences of up to 10-fold in each age group), the best predictor of PCA morphine requirement in the first 24 h after surgery (the amount required in the 24 h after the initial loading dose) was the age of the patient. An estimate of these requirements for patients over the age of 20 years can be obtained from the formula: average first 24 h morphine requirement (mg) = 100 - age. PCA allows patients the flexibility to titrate their own opioid dose; if conventional analgesic regimens are to become more effective, they too need to allow for the wide interpatient variation in dose requirements. Although previous studies have noted a correlation between patient age and the amount of opioid needed, this study quantifies this correlation and provides guidelines for opioid dosing. Prescriptions for conventional analgesic regimens should include a dose range centred on values obtained from the above formula to allow for the large interpatient variation in each age group. While initial morphine dose should be guided by patient age and not weight, subsequent doses must still be titrated according to effect.

A molecular model for the formation and properties of fluid gels.

The effects of biopolymer gelation in a shear field are discussed. Gel particles are produced if the gelation mechanism involves an aggregation step. Particular attention is paid to the molecular events of ordering and aggregation upon cooling, investigating the differences in such processes as a result of shearing during gelation. A model is proposed which follows the conception of the particles, their growth, physical properties and stability.

The determination of absorption coefficients for measurement of carboxy-hemoglobin, oxy-hemoglobin, reduced hemoglobin, and met-hemoglobin in sheep using the IL482 CO-Oximeter.

The IL482 CO-Oximeter uses four wavelengths of visible light to analyze blood samples for the relative percentages of oxy-, carboxy-, reduced, and met-hemoglobin. In the analysis, the absorption at each of the wavelengths is multiplied by a matrix of four coefficients to derive the quantities of the four hemoglobin types. The normal settings of the CO-Oximeter coefficients are those for adult human hemoglobin. However, animal blood can be measured provided that the appropriate matrix of coefficients is available. Instrumentation Laboratory has provided sets of coefficients for several animal species. The company has also published a protocol for determining coefficients for other animal species. This protocol was examined using sheep hemoglobin-A blood and found to be inaccurate. The IL482 protocol is unsatisfactory because, if the initial error is large, successive iterations to determine the coefficient matrix through revision of the estimates of residual hemoglobin types do not converge. With sheep type-A hemoglobin, the use of human coefficients for the initial estimate gave a value of 6%, whereas, by chromatography, the carboxyhemoglobin (COHb) was 0.12% (i.e., a better initial estimate would be zero). When this was done, the final COHb estimate on "as-drawn" blood was within 1% of the COHb measured independently by gas chromatography. Revision of the protocol gave a markedly better accuracy, within 2% for COHb over the whole range when tested against mixtures of CO and O2 tonometered blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Norpethidine toxicity and patient controlled analgesia.

Patient-controlled analgesia (PCA) with i.v. opioids is prescribed increasingly. We report three cases of norpethidine toxicity in patients receiving pethidine by PCA.

Use of an oxygen concentrator linked to a draw-over vaporizer (anesthesia delivery system for underdeveloped nations)

The use of an oxygen concentrator linked to a draw-over vaporizer was examined. The fractional oxygen concentration from this equipment was dependent on the minute ventilation, oxygen output of the concentrator (%), and the presence of an oxygen economizer tube (OET) (a 900-mL corrugated tube). Fractional oxygen concentrations were always higher with an OET than without an OET (other variables being constant). With the OET in place, the fractional oxygen concentration was only dependent on the minute volume and independent of the pattern of ventilation (i.e., varying inspiratory and expiratory ratios and inspiratory and expiratory pauses). Without an OET, the performance of the system was considerably impaired. In this setting, the final oxygen concentration depended not only on the added flow of oxygen and minute volume but also on the pattern of ventilation. In conclusion, when using a draw-over vaporizer linked to an oxygen concentrator, an OET is essential so as to provide consistent oxygen concentrations to the patient at any given minute volume.

Intra-operative patient-controlled sedation. Comparison of patient-controlled propofol with patient-controlled midazolam.

Propofol and midazolam were compared for intra-operative patient-controlled sedation in 40 ASA 1 day patients undergoing surgical extraction of third molar teeth under local anaesthesia. All patients initially received 0.7 micrograms.kg-1 fentanyl. Patients in the propofol group self-administered 20 mg (2 ml over 6 s) bolus doses of propofol; successful demands averaged 8.0 (SD 4.4) and unsuccessful demands (during the 1 min lockout period) 2.8 (SD 4.1). The midazolam group self-administered 0.5 mg (2 ml over 6 s) bolus doses and averaged 14.0 (SD 6.3) and 17.6 (SD 19.8) successful and unsuccessful demands respectively. Postoperative memory, measured with delayed free recall, and postoperative mental performance, measured with the frequency accrual speed test index, were both significantly less impaired in the propofol group. Although there was no significant difference in patient satisfaction, measured postoperatively, propofol was judged the more suitable agent for patient-controlled sedation, because of its more rapid response to fluctuating intra-operative requirements, superior recovery characteristics and beneficial effect on mood.

Ventilatory effects of clonidine alone and in the presence of alfentanil, in human volunteers.

Clonidine, an alpha 2-adrenergic agonist, can potentiate opioid-induced analgesia. In a double-blind placebo-controlled study in human volunteers, we sought to determine whether clonidine also potentiates opioid-induced respiratory depression. Hypercapnic ventilatory responses (minute ventilation, mean inspiratory flow rate, and mouth occlusion pressure) were measured in five healthy male volunteers on two separate occasions (with or without clonidine, approximately 3.5 micrograms.kg-1 orally) under the following conditions: baseline, 2 h after clonidine/placebo (alfentanil concentration of 0), and during computer-controlled alfentanil infusions to approximate plasma concentrations of 5, 10, 20, 40, and 80 ng.ml-1. Plasma alfentanil concentrations were measured before and after each rebreathing test, and clonidine concentrations were measured after each rebreathing test. The end-tidal CO2 (PET(CO2)) was measured continuously. Data were analyzed by repeated-measures analysis of variance. The PET(CO2) and measured concentrations of alfentanil were included as covariates, and a compound symmetry error analysis was assumed. Statistical significance was achieved when P less than 0.05. For minute ventilation, mean inspiratory flow rate, and mouth occlusion pressure there was a statistically significant relationship to the covariates of PET(CO2) and plasma alfentanil concentration. Clonidine, when compared to placebo, caused a small but significant depression of mean inspiratory flow rate. There was similarly a small, but statistically insignificant, depression of minute ventilation by clonidine. The mouth occlusion pressure was not affected by clonidine treatment. Clonidine treatment did not potentiate alfentanil-induced respiratory depression. Although the combination of an opioid and an alpha 2-adrenergic agonist may act synergistically for the analgesic response, there is no synergistic effect by this drug combination on respiratory depression.

Intra-operative patient-controlled sedation and patient attitude to control. A crossover comparison of patient preference for patient-controlled propofol and propofol by continuous infusion.

Intra-operative patient controlled sedation with propofol (bolus dose 18 mg over 5.4 s; lockout period 1 min) has been compared to continuous propofol infusion (3.6 mg.kg-1.h-1) in a randomised crossover study of 38 ASA 1 or 2 day surgery patients undergoing two-stage bilateral extraction of third molar teeth under local anaesthesia (76 procedures). Mean (SD) propofol used (mg.kg-1) was less with patient-controlled sedation (2.39 (1.28) than with the infusion (2.58 (0.84)) but the difference was not statistically significant. There were only minor differences between the methods in postoperative recovery of cognitive function and no differences for patient cooperation and surgeon's satisfaction with sedation. Patient-controlled sedation was preferred by 19 patients, continuous infusion by 10, with nine indifferent. Preferences, expressed as mild, moderate or strong, were significantly stronger for patient-controlled sedation (p < 0.05). Sedation was no deeper than eyelid closure with response to command in all 76 procedures. This level was reached in all 38 infusion cases but in only 26 cases with patient-controlled sedation, where 12 patients remained less sedated (p < 0.01). Patient-controlled sedation with propofol provided safe sedation and was strongly preferred over the infusion by a large proportion of patients.

Prevalence of hepatitis B surface antigen and antibody (hepatitis B virus markers) in personnel at a children's hospital.

After two cases of acute hepatitis B infection occurred in phlebotomists at The Hospital for Sick Children in 1985, a seroprevalence survey of hepatitis B virus markers was undertaken. Directors in high-risk areas were advised by phone and memorandum to screen employees. Participation was entirely voluntary, and employees who did not respond were contacted six weeks after initial notification. Information obtained from each participant through a self-administered questionnaire included age, duration of employment in current pediatric occupation, history of blood transfusions, immune globulin prophylaxis, needlestick injury, and country of birth (North America/United Kingdom or other). Sera identified by code were tested by radioimmunoassay. Interactions were analyzed by using a multiple logistic regression model. A total of 10% of the personnel in high-risk areas, in which there was frequent exposure to blood or blood products, had hepatitis B markers in their blood, compared with 2% who did not have this exposure. Birthplace and occupation have independently significant effects on the likelihood of having hepatitis B markers. There appears to be an increased risk to employees in pediatric units, depending on the patient (and parent) population being served, although the risk may be lower than in adult hospitals.