Positron emission tomography of the brain: new possibilities for the investigation of human cerebral pathophysiology.

In the foregoing an overview of positron emission tomography has been presented. Its theoretical, technical, and methodological implications, as well as its clinical applications have been outlined. The emphasis has been on the quantitative aspects of the method and its usefulness is investigating normal and pathological functions of brain tissue. Although the potential of this new research technique is obvious, many theoretical and practical difficulties still need to be solved. Nevertheless it provides an opportunity to bridge the gap between basic experimental research and clinical medicine.

Correction for the presence of intravascular oxygen-15 in the steady-state technique for measuring regional oxygen extraction ratio in the brain: 2. Results in normal subjects and brain tumour and stroke patients.

Values of regional cerebral oxygen extraction ratio and oxygen utilisation obtained with the oxygen-15 steady-state inhalation technique have been found to be overestimated due to the signal from intravascular oxygen-15. A previously described method to correct for this intravascular component has been applied to a series of studies on normal subjects, and on brain tumour and stroke patients. With this correction the regional cerebral oxygen extraction ratio in normals becomes comparable to the global values previously reported with arteriovenous sampling techniques. Within the lesions of brain tumour and stroke patients, the corrections have been found to be variable and often substantial. It is concluded that failure to apply this correction may result in major errors in the values for regional oxygen extraction ratio and oxygen utilisation. This is especially true when the regional blood flow and oxygen extraction ratio of a tissue is low and regional blood volume is high.

Measurement of cerebral blood flow using bolus inhalation of C15O2 and positron emission tomography: description of the method and its comparison with the C15O2 continuous inhalation method.

This article describes a rapid method for the regional measurement of cerebral blood flow using a single breath of C15O2 and positron emission tomography. The technique is based on the bolus distribution principle and utilises a reference table for the calculation of flow. Seven subjects were studied using both this method and the C15O2 continuous inhalation steady-state technique. The single-breath method gave flow values 20% higher than those obtained using the steady-state method. A simulation study was performed in an attempt to define the reasons for the difference between the two techniques. Estimations were made of identified sources of error in the measurement of regional cerebral blood flow using the single-breath technique and compared with results from a similar study previously described for the steady-state technique. However, further comparative studies will be necessary to satisfactorily explain the difference between both techniques.

Vigabatrin in intractable childhood epilepsy: a retrospective study.

The effects of vigabatrin were studied over a 6-month period in 43 patients with intractable epilepsy. Children with complex partial seizures, with or without secondary generalization, responded best with more than one-half achieving a greater than 50% reduction; generalized tonic-clonic seizures also improved but there was no significant change in absence or myoclonic seizures. Four patients are seizure-free on monotherapy with vigabatrin. The drug was well tolerated with few side effects.

Effects of restricted knee flexion and walking speed on the vertical ground reaction force during gait.

Although lower extremity immobilization, including restricted knee flexion, is commonly used in rehabilitation, the effect of angle of knee restriction and walking speed on the vertical ground reaction forces during gait is unclear. Force plate measurements were made on 36 healthy males walking at three different speeds when knee flexion was unrestricted and restricted to both 10 and 25 degrees. Analysis of variance and post hoc analyses showed significant increases in four characteristics of the vertical ground reaction force in the restricted leg and in two characteristics in the unrestricted leg during walking with restricted knee flexion. Loading rate and unloading rate for the restricted leg and peak force for both legs showed significant speed-knee flexion restriction interactions. At the fast walking speed, two significant differences were found between knee flexion restrictions of 10 and 25 degrees. The clinical implications of these findings are that restricted knee flexion during gait may significantly alter the forces applied to both lower limbs.

The Anaesthetic Mortality Assessment Committee 1979-1984.

A review of 324 cases reported to the Anaesthetic Mortality Assessment Committee over a five year period confirms a low incidence of cases associated primarily with anaesthesia. The committee has identified potential problem areas affecting anaesthesia which require continued vigilance on the part of the anaesthetist. These include the fluid balance of patients, the potential for hypothermia, altered patterns of drug action in the elderly and critically ill and the influence of other disease processes-notably those affecting the heart. As well there are the rare problems more directly associated with anaesthesia such as hypersensitivity reactions and malignant hyperpyrexia. Technical problems during anaesthesia such as misplacement of the endotracheal tube are not commonly associated with death, but because they are preventable, are of particular importance.

The need to train anaesthetists in New Zealand.

A survey of New Zealand public hospitals undertaken at the end of 1974 shows that the country is training half the number of anaesthetists to maintain the public hospital-based anaesthetic services. There is a need to develop and expand training programmes for anaesthetists. New graduates can be assured that there are career prospects in the specialty.

Is a microfilter necessary in a single unit blood transfusion.

Pulmonary dysfunction may be caused by microaggregates passing through a standard blood filter (170 mu) during transsfusion. In this study a sheep was repeatedly tranfused with a single unit (about 450 ml) of her own blood to compare the effects of 27 mu and 170 mu pore filters on lung function. Lung function was assessed by comparing cardiac output, pulmonary shunt and alveolar-arterial oxygen tension gradient before, during and after transfusion. There were no significant changes in these parameters. So far as these results can be extrapolated from sheep to man, it is considered that the more expensive 27 mu pore filter is not justified in small volume transfusions.

The control of postoperative pain by EMG biofeedback in patients undergoing hysterectomy.

Electromyographic (EMG) measurements from the forehead and rectus abdominis areas were undertaken in a group of patients presenting for elective hysterectomy. The efficacy of EMG auditory feedback as a means of inducing relaxation so as to modify the dose of postoperative analgesia was examined and compared with the dose in subjects having EMG measurements without audiofeedback. Comparison was also made with a group of subjects who did not have EMG measurements. Subjects in those groups who were given relaxation instruction received less postoperative analgesia than subjects not receiving this treatment. A reduction in EMG activity was demonstrated with auditory feedback, but this did not relate directly to reduced analgesic administration after surgery.

A hypersensitivity screening clinic following untoward reactions to anaesthesia.

Anaphylactoid or anaphylactic reactions to drugs used during general anaesthesia are potentially life threatening. It is important that they be differentiated from other types of cardio-respiratory collapse. At present a detailed history of the time sequence of events in relation to drug administration is of a greatest importance. Retrospective skin testing may then indicate which agent was involved, although false positives and false negatives may occur. Forty-nine patients who presented with a history of collapse during anaesthesia over a five year period were skin tested. Positive results were obtained in 22, ten gave inconclusive test results but a strongly suggestive history. The remainder were considered to have other causes for their clinical presentation. The incidence of severe reactions confirmed by history and by skin testing in this community is approximately 1:4000.