Biomedical subjects

M R Crawford

Publications and source records attributed to M R Crawford.

6 recordsLinked to original sources

PubMed1992

Some effects of isoflurane on I waves of the motor evoked potential.

We have investigated the effects of isoflurane anaesthesia on the motor evoked potential recorded in the extradural space during corrective spinal surgery in 15 patients. Isoflurane was added to a nitrous oxide in oxygen mixture supplemented with fentanyl and a neuromuscular blocking agent. Isoflurane was administered to achieve end-tidal concentrations of 2%, 1% and 0% in all patients, and also of 1.5% and 0.5% in nine patients. Transcranial electrical stimulation of the motor cortex was used to elicit descending volleys in corticospinal axons (the motor evoked potential). With stimuli of 450-750 V and no isoflurane, multiple I waves were always seen following the D wave. In all patients the number of I waves decreased and individual I waves became smaller in amplitude the greater the isoflurane concentration, but there were only minor changes in the D wave. The greatest depressant effect on I waves occurred at an end-tidal concentration of 0.5%. Given that I waves are an index of synaptic transmission, anaesthetic-induced changes in I waves may provide a useful model for the neuronal events underlying anaesthesia-induced unconsciousness.

Adolescent↗

PubMed1992

Quantification technique for the middle latency response.

Few objective analysis techniques have been developed for, or applied to, the auditory evoked middle latency response (MLR). This report demonstrates the applicability of the Fsp statistical technique (Elberling and Don, 1984) to the MLR time domain. Subjects for this study were 10 normal hearing young adults. The stimuli were 60, 40, 20 dB nHL clicks and a NS control. Evoked responses were obtained as a series of 10,000 individual traces for each stimulus presentation and analyzed off line to determine the applicability of the Fsp technique. In addition, the effects of filtering and time window size were examined to determine the optimum collection characteristics for the Fsp analysis method. The results indicate that the Fsp technique is a viable tool for estimating signal-to-noise characteristics of the MLR. When using the Fsp technique with the MLR the high-pass filter should be set to 20 Hz so that a 50-msec time window can be used.

Acoustic Stimulation↗

PubMed1991

Prevalence of hearing loss in adults with sickle cell disease.

Hearing status in 75 adult subjects with sickle cell disease was examined. Thirty-one (or 41%) of the subjects failed the hearing screening. When examined by hemoglobin type, it was found that persons with sickle cell C disease had the greatest incidence of hearing loss, although all subject groups exhibited greater prevalence rates than the general population. The results suggest that routine audiologic assessment be incorporated into the regular medical examination for adults with sickle cell disease.

Adolescent↗

PubMed1991

Hearing disorders in sickle cell disease: cochlear and retrocochlear findings.

The auditory system was assessed in 34 adult subjects with sickle cell disease using standard audiometric test techniques. The study results indicate that patients with sickle cell disease are at risk for retro-cochlear as well as cochlear dysfunction of the auditory system. However, there is no consistent audiometric pattern that is pathognomonic of sickle cell disease. The test results indicate that auditory status should be carefully monitored in all adult patients with sickle cell disease.

Acoustic Impedance Tests↗

PubMed1988

Epidermolysis bullosa--a review of 15 years' experience, including experience with combined general and regional anaesthetic techniques.

Eight patients with epidermolysis bullosa received a total of 60 anaesthetics for 67 procedures over the fifteen-year period 1972 to 1986. On twenty-three occasions patients were intubated. On thirteen occasions general anaesthesia was supplemented by regional blockade, involving a total of thirty-four local anaesthetic blocks. Complications from intubation were minimal and none were seen related to regional blockade.

Anesthesia, Conduction↗

PubMed1986

High-frequency ventilation.

Over the last six years high-frequency ventilation has been extensively evaluated both in the clinical and laboratory settings. It is now no longer the great mystery it once was, and it is now no longer believed (as many had hoped), that it will solve all the problems associated with mechanical pulmonary ventilation. Although the technique is safe and appears to cause no harm even in the long term, it has not yet been shown to offer any major advantages over conventional mechanical ventilation.

Biomechanical Phenomena↗