Changes in respiratory sensations induced by lobeline after human bilateral lung transplantation.

1. The sensations evoked by the injection of lobeline into the right antecubital vein were studied in 8 subjects after bilateral lung transplantation and 10 control subjects. In control subjects, two distinct sensations were experienced. There was an early noxious sensation (onset approximately 10 s) followed by a late sensation of breathlessness (onset approximately 26 s) associated with involuntary hyperventilation. The early sensation was accompanied by respiratory and cardiovascular changes. 2. In contrast to control subjects, the early respiratory events and the noxious sensations evoked by injections of lobeline (18-60 microg kg(-1)) did not occur in subjects with recent bilateral lung transplantation. This suggests that the early respiratory sensations are mediated by the discharge of receptors in the lungs. 3. The late hyperventilation and the accompanying sensation of breathlessness occurred in both transplant and control subjects and are therefore likely to be mediated by receptors elsewhere in the body, presumably systemic arterial chemoreceptors stimulated by lobeline. 4. In control subjects, but not transplant subjects, there was a consistent decrease in mean arterial pressure associated with the lobeline injection. This suggests that pulmonary afferents mediate the hypotension. 5. For transplant subjects studied more than a year after transplantation, there was some evidence that the noxious respiratory sensations evoked by lobeline had returned. This suggests that some functional reinnervation of pulmonary afferents may occur.

Depression of I waves in corticospinal volleys by sevoflurane, thiopental, and propofol.

UNLABELLED: Isoflurane depresses the number and amplitude of I waves of the motor-evoked potential produced by transcranial electrical stimulation of the motor cortex and thus affects components of the corticospinal volley that are believed to arise from Laminae III and V. This study extends these observations to sevoflurane (9 patients) and the two IV anesthetics, thiopental and propofol (10 sets of observations in 10 and 6 patients, respectively). The patients' ages ranged from 10 to 17 yr. Sevoflurane was administered to achieve end-tidal concentrations of 0.5%-3%. Thiopental and propofol were given as boluses of 5 mg/kg and 2 mg/kg, respectively, to patients anesthetized with nitrous oxide, fentanyl, midazolam, and a muscle relaxant. Sevoflurane had a depressant effect on I waves essentially similar to that of isoflurane; thiopental depressed I wave activity by an average of 33% (95% confidence interval: 20%-46%, P < 0.001) and propofol by 39% (95% confidence interval: 20%-40%, P < 0.001). With all three anesthetics, later I waves showed the most amplitude depression. The three anesthetics had qualitatively similar effects on I waves. IMPLICATIONS: Sevoflurane, thiopental, and propofol depress components of the corticospinal volley produced by transcranial electrical stimulation of motor cortex in a manner qualitatively similar to isoflurane. The findings indicate that anesthetics with primarily hypnotic actions suppress interneuronal activity in cerebral cortex.

Absence of viscerosomatic inhibition with injections of lobeline designed to activate human pulmonary C fibres.

1. Activation of pulmonary C fibres (J receptors) in animals produces inhibition of spinal motoneurones. Intravenous bolus injections of lobeline are believed to activate pulmonary C fibres (J receptors) in human subjects and to produce characteristic sensations and cardiorespiratory responses. This study quantified the respiratory sensations evoked by such injections and then used a range of suprathreshold doses of lobeline and tested for the presence of reflex or descending inhibition of motoneuronal output. 2. Injections of lobeline produced dose-dependent sensations of respiratory discomfort referred to the throat and upper chest beginning within about 10 s and often associated with coughing. As the dose increased the latency for the sensations decreased while their duration and intensity increased. Reflex changes in blood pressure, heart rate and ventilation also occurred. 3. Injections of lobeline at doses sufficient to evoke respiratory discomfort lasting 25-32 s (37-73 microgram kg-1) increased the size of the H reflex in soleus with an onset latency of about 10 s and lasting about 20 s. 4. The size of EMG responses evoked in upper limb muscles by transcranial magnetic stimulation of the motor cortex increased shortly after injections and remained elevated for about 30-35 s. 5. Injections of lobeline during sustained voluntary contractions of the elbow flexors at submaximal or maximal levels did not impair the ability to produce force. 6. Walking was not disrupted by repeated suprathreshold doses of lobeline. 7. It is concluded that injections of lobeline sufficient to evoke cardiorespiratory reflexes and sensations of severe respiratory discomfort are not associated with functionally important inhibition of motor performance. The results cast doubt on the ability of the J reflex to limit exercise in humans.

Longitudinal distortion product otoacoustic emission (DPE) latency changes in preterm neonates.

The purpose of this investigation was to determine what types of changes occur in the distortion product otoacoustic emission (DPE) latency with increasing postconceptual age. These DPE latency changes were then described in relation to developmental changes in conductive and cochlear mechanisms in the neonate. Longitudinal DPE latency measurements were obtained from a single ear of 18 preterm neonates. DPEs were evoked at f2s of 3, 4 and 5 kHz. The longitudinal data revealed that DPE latency decreased as a function of postconceptual age for f2 of 3 and 4 kHz, but did not change significantly at 5 kHz. These findings suggest that (1) the conductive and/or cochlear system have not reached maturity in the preterm neonate, (2) DPE latency can be used to measure developmental changes in the auditory periphery, and (3) maturational changes need to be considered if DPE latency is used to identify auditory dysfunction in neonates.

DNA sequence similarity between California isolates of Cryptosporidium parvum.

We evaluated whether nucleic acid amplification with primers specific for Cryptosporidium parvum followed by automated DNA sequence analysis of the PCR amplicons could differentiate between California isolates of C. parvum obtained from livestock, humans, and feral pigs. Almost complete sequence identity existed among the livestock isolates and between the livestock and human isolates. DNA sequences from feral pig isolates differed from those from livestock and humans by 1.0 to 1.2%. The reference sequence obtained by Laxer et al. (M. A. Laxer, B. K. Timblin, and R. J. Patel, Am. J. Trop. Med. Hyg. 45:688-694, 1991.) differed from California isolates of C. parvum by 1.8 to 3.2%. These data suggest that DNA sequence analysis of the amplicon of Laxer et al. does not allow for differentiation between various strains of C. parvum or that our collection of isolates obtained from various hosts from across California was limited to one strain of C. parvum.

Electrophysiologic changes in preterm neonates: auditory brain stem response and distortion product otoacoustic emissions.

The purposes of this investigation were to determine 1) if auditory peripheral maturity is present in the newborn; 2) if not, at what age maturational changes occur in the peripheral auditory system from preterm to full-term; and 3) how results of tests used to identify auditory dysfunction in neonates, such as distortion product otoacoustic emissions (DPEs) and auditory brain stem responses (ABRs), change during this period. Longitudinal DPE amplitude and ABR wave I latency measurements were obtained from a single ear of 18 preterm neonates. The DPEs were evoked at f2s of 2, 3, 4, and 5 kHz. The longitudinal data revealed that in general, DPE amplitude increased and ABR wave I latency decreased as a function of postconceptional age. These findings suggest that 1) the peripheral auditory system has not reached maturity in the preterm neonate; 2) maturational changes continue from preterm to full-term; and 3) these changes are reflected in ABR and DPE measurements.

Cotrel-dubousset instrumentation in children using simultaneous motor and somatosensory evoked potential monitoring.

STUDY DESIGN: To record prospectively combined motor- and somatosensory-evoked potentials in children during scoliosis surgery using Cotrel-Dubousset instrumentation, without using special anesthetic or muscle relaxant regimens. OBJECTIVE: To determine the outcome of scoliosis surgery guided by a new technique of monitoring motor- and somatosensory-evoked potentials simultaneously. SUMMARY OF BACKGROUND DATA: Other techniques used to assess cord function generally are limited by special anesthetic requirements or assess only a limited part of the cord or monitor motor function separately from somatosensory function. METHODS: Spinal cord function was monitored using epidural leads to record simultaneously the descending motor volley (by transcranial electrical stimulation) and the ascending somatosensory volley (by tibial nerve stimulation) at two spinal levels. RESULTS: Combined motor- and sensory-evoked potentials were recorded successfully in 138 of 160 children (81%). Changes in evoked potential waveforms were seen in eight patients (5%), but resolved or lessened in response to appropriate measures. Curve correction was satisfactory, and there were no new postoperative deficits or worsening of preexisting deficits in any patient. CONCLUSION: A spinal cord monitoring system is described that is safe, reliable, accurate, and makes it unnecessary to resort to the "wake-up" test.

Variability of motor-evoked potentials recorded during nitrous oxide anesthesia from the tibialis anterior muscle after transcranial electrical stimulation.

When recorded as a compound muscle action potential (CMAP), the motor-evoked potential (MEP) is affected by volatile anesthetics and nitrous oxide. However, MEPs recorded using epidural electrodes in the presence of nitrous oxide are highly reproducible from trial to trial. We wished to establish the reproducibility over time of the CMAP produced by supramaximal transcranial electrical stimulation of the human motor cortex. Cascades of 100 successive CMAPs were recorded from the tibialis anterior muscles of six anesthetized patients undergoing scoliosis surgery, in response to transcranial electrical stimuli of > 500 V. Satisfactory CMAPs could be recorded in the presence of nitrous oxide, but not isoflurane. Latencies and amplitudes were reproducible in repeated sequences of 100 responses. However, amplitude and, to a lesser extent, latency, were highly variable within a sequence. In addition, occasional individual stimuli, although rarely successive ones, failed to evoke a CMAP. CMAPs have a much higher trial-to-trial variability than corticospinal volleys recorded from the epidural space. Using the present methodology it would be difficult to rely on CMAP recordings as an indicator of corticospinal function in the clinical monitoring situation.

Role of airway receptors in the reflex responses of human inspiratory muscles to airway occlusion.

1. This study was designed to investigate the role of airway receptors in the responses of a range of inspiratory muscles to airway occlusion. The occlusion had a rapid onset (< 10 ms), lasted 250 ms and produced only a slight impediment to inspiration. 2. Based on analysis of single trials and averaged rectified electromyographic responses (EMG) in six subjects, there was a major inhibition (IR) with an onset at 34 +/- 2 ms and a trough at 65 +/- 2 ms, and an excitation (ER) with a peak at 105 +/- 2 ms. These two responses are reflex given that voluntary reaction times to a tap on the chest wall occurred at latencies longer than the peak of ER. 3. The responses to airway occlusion did not appear in limb muscles which contracted phasically with inspiration. 4. Anaesthesia of the surface receptors of the upper airway did not attenuate the responses to occlusion. Because this procedure does not eliminate the inputs from muscle and deep laryngeal pressure receptors, two subjects were tested when intubated with a cuffed endotracheal tube so that the occlusion was delivered only to structures below the level of the trachea. Responses to airway occlusion were preserved when all upper airway receptors were 'bypassed'. 5. Responses to airway occlusion also remained after prolonged inhalation of nebulized lidocaine (lignocaine) sufficient to block the cough reflex. 6. The receptors mediating the responses to airway occlusion are therefore likely to reside in inspiratory muscles acting on the chest wall. If so, the short-latency inhibition contrasts with the excitatory stretch reflex responses observed in limb muscles.

Estimated noise distributions across stages of consciousness utilizing the Fsp quantification technique.

We used the Fsp technique to quantify the influence of changing stages of consciousness on the signal-to-noise ratio of the middle latency response (MLR). The MLR and polysomnographic activity were obtained from 10 subjects during a continuous 6-hour period. The Fsp statistic was applied to the MLR data in order to determine the number of scores above a specified criterion in each stage of consciousness and time window of analysis. Results demonstrated that the number of Fsp scores exceeding the criterion of acceptance decreased with increasing depth of sleep. The awake stage yielded the greatest proportion of scores above the criterion. The background noise data were analyzed separately. The distributions of noise differed as a function of stage of consciousness.

Age-related response to lidocaine-prilocaine (EMLA) emulsion and effect of music distraction on the pain of intravenous cannulation.

OBJECTIVE: To compare the efficacy of a local anesthetic cream and music distraction in reducing or preventing pain from needle puncture (intravenous cannulation) in children. A secondary aim was to examine the influence of age on the pain report and behavior and on the therapeutic outcome. METHODOLOGY: Children aged 4 to 16 years (N = 180) who were to undergo surgery under general anesthesia via intravenous cannulation were randomly allocated to one of three interventions. The comparison of lidocaine-prilocaine emulsion (EMLA, Astra) and a placebo emulsion was double-blind. Stratification by age group (4 to 6, 7 to 11, 12 to 16) ensured an equal number of children (20) in each intervention/age group category. A global assessment of the behavioral reaction to the procedure was made by the principal investigator, taking into account vocal, verbal, facial, and motor responses. The child was asked to assess pain severity on the Faces Pain Scale (FPS) and a visual analogue toy (VAT). The scales were applied conservatively as ordinal scales: FPS 0 to 6; VAT 0 to 10. RESULTS: Children who received lidocaine-prilocaine emulsion reported less pain (mean FPS score = 1.42) compared with placebo emulsion (mean FPS score = 2.58) and with music distraction (mean FPS = 2.62). There was a highly significant therapeutic effect (P < .001) on the self-report and behavioral scores. Younger children, regardless of intervention, reported significantly more pain than the older children (mean FPS scores: 2.85, 2.33, 1.43 for age groups 4 to 6, 7 to 11, and 12 to 16 respectively; P < .001). The superiority of the local anesthetic emulsion was maximal in the youngest age group (4 to 6) almost eliminating pain-related behavior, and multiple regression analysis confirmed significant age and treatment effects and revealed interaction between therapeutic effect and age. Although a trend favoring the active emulsion was evident in the older children (7 to 11, 12 to 16) the differences were not significant. The pain scores were influenced by the type (gauge) of cannula, but this did not affect the conclusion regarding therapeutic and age effects. There was no influence of sex, experience with venipuncture, or whether the child was anxious on arrival in the operating room. CONCLUSIONS: The results show that lidocaine-prilocaine emulsion is highly effective in preventing pain from venipunctures in young children, the group in most need of prevention.

Speech spectra for six recorded monosyllabic word tests.

Speech spectra (long-term RMS levels and 1% speech peaks) in third-octave bands were determined for six monosyllabic word test materials: digital recordings of the Central Institute for the Deaf W-22 word test and the Northwestern University NU-6 word test obtained from Qualitone; audiotape recordings of the Central Institute for the Deaf W-22 word test, the Northwestern University NU-6 word test, and the Harvard Psycho-Acoustic Laboratory PB-50 word test obtained from Auditec of St. Louis; and an audio-tape recording of the Maryland CNC word test obtained from Olsen Distributors. The spectra were generally within 2 SD of previous results for continuous speech spoken by an average male talker (Cox, Matesich, & Moore, 1988; Cox & Moore, 1988), but differed sufficiently from those data and from one another to affect the accuracy of Articulation Index calculations. The relationship between the level of the calibration tone and the speech in the third-octave band centered at 1000 Hz was different for each recording.

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.

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.

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.

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.

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.

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.

Ganglionic slow postsynaptic potentials and muscarinic asynchronous discharge in postganglionic nerve elicited by orthodromic stimulation.

Simultaneous recordings of the slow postsynaptic potentials of in vitro rabbit superior cervical ganglion and the muscarinic asynchronous discharge in the postganglionic nerve were obtained in order to examine their relationship. Analyses for linear correlation indicated that the peak amplitude of the S-EPSP cannot fully determine the maximum rate of muscarinic asynchronous discharge. The rate of asynchronous discharge in the postganglionic nerve systematically increased with increases in either the frequency or duration of preganglionic stimulation even after the S-EPSP was at asymptotic levels. We suggest that this deviation from linearity is the result of repetitive spike discharge elicited by the S-EPSP. The S-IPSP had no apparent influence on generation of asynchronous afterdischarge, but may have had an influence on asynchronous discharge occurring during a train of stimuli. Incubation of ganglia with gallamine, an antagonist of the ganglionic muscarinic receptors mediating hyperpolarization, resulted in the selective blockade of the S-IPSP. Neither the S-EPSP nor the muscarinic afterdischarge were suppressed by muscarinic receptor blockade by gallamine, nor did gallamine produce any effect on the nicotinic F-EPSP or the noncholinergic SS-EPSP. Temporary exposure of ganglia to dopamine, in the presence of an inhibitor of catechol-O-methyltransferase, was followed by a potentiation of the muscarinic afterdischarge in accordance with the long-term enhancement reported for the S-EPSP.