The psycho-galvanic reflex: a pharmacological study of the peripheral mechanism

The validity of skin conductance for assessing acute pain in mechanically ventilated infants: A cross-sectional observational study

BACKGROUND

Assessing pain in mechanically ventilated infants is challenging. The assessment of skin conductance (SC) is based on the sympathetic nervous system response to stress. This study purpose was to evaluate the validity of SC for assessing pain in mechanically ventilated infants.

METHODS

A prospective cross-sectional observational design was used to study SC and its relation to: the category of procedure (i.e., painful or non-painful); the phase of procedure (i.e., before, during and after), and referent pain measurements (i.e., Premature Infant Pain Profile-Revised (PIPP-R) and Neonatal Facial Coding System (NFCS)). Eligible infants were those up to 12 months of age, in intensive care units, who were mechanically ventilated, and required painful and non-painful procedures.

RESULTS

From October 2017 to November 2018, 130 eligible infants were identified, and 55 infants were studied. SC (number of waves per second) during painful procedures (median 0.27, interquartile range 0.2-0.4) was statistically significantly higher than those during non-painful procedures (0, 0-0.09). SC during painful procedures was statistically significantly higher than those before (0, 0-0.07) and after painful procedures (0, 0-0.07). SC showed moderate statistically significant positive correlations with PIPP-R (Spearman's rho = 0.4-0.62) and the four-item NFCS (Spearman's rho = 0.31-0.67) before, during and after painful or non-painful procedures respectively. SC had excellent performance (area under the receiver operator curve = 0.979) with excellent sensitivity (92.31%), specificity (95.42%) and negative predictive value (99.21%) but only sufficient positive predictive value (66.67%) when used to discriminate moderate-to-severe pain.

CONCLUSIONS

SC showed good validity for assessing pain in critically ill infants requiring mechanical ventilation.

SIGNIFICANCE OF THE STUDY

Pain assessment in mechanically ventilated infants is challenging. In this study, the validity of skin conductance (SC) for pain assessment is evaluated in the same population of infants during painful and nonpainful procedures. SC showed good validity for assessing acute pain in relation to category of procedure, phase of procedure, and referent pain measurements. SC is a promising method, especially with other pain assessment methods and other determinants of pain, in a multimodal pain assessment approach to understand the complexity of pain in mechanically ventilated infants.

Point process models for sweat gland activation observed with noise

The aim of this article is to construct spatial models for the activation of sweat glands for healthy subjects and subjects suffering from peripheral neuropathy by using videos of sweating recorded from the subjects. The sweat patterns are regarded as realizations of spatial point processes and two point process models for the sweat gland activation and two methods for inference are proposed. Several image analysis steps are needed to extract the point patterns from the videos and some incorrectly identified sweat gland locations may be present in the data. To take into account the errors, we either include an error term in the point process model or use an estimation procedure that is robust with respect to the errors.

Regional brain responses associated with thermogenic and psychogenic sweating events in humans

Sweating events occur in response to mental stress (psychogenic) or with increased body temperature (thermogenic). We previously found that both were linked to activation of common brain stem regions, suggesting that they share the same output pathways: a putative common premotor nucleus was identified in the rostral-lateral medulla (Farrell MJ, Trevaks D, Taylor NA, McAllen RM. Am J Physiol Regul Integr Comp Physiol 304: R810-R817, 2013). We therefore looked in higher brain regions for the neural basis that differentiates the two types of sweating event. Previous work has identified hemispheric activations linked to psychogenic sweating, but no corresponding data have been reported for thermogenic sweating. Galvanic skin responses were used to measure sweating events in two groups of subjects during either psychogenic sweating (n = 11, 35.3 ± 11.8 yr) or thermogenic sweating (n = 11, 34.4 ± 10.2 yr) while regional brain activation was measured by BOLD signals in a 3-Tesla MRI scanner. Common regions activated with sweating events in both groups included the anterior and posterior cingulate cortex, insula, premotor cortex, thalamus, lentiform nuclei, and cerebellum (P(corrected) < 0.05). Psychogenic sweating events were associated with significantly greater activation in the dorsal midcingulate cortex, parietal cortex, premotor cortex, occipital cortex, and cerebellum. No hemispheric region was found to show statistically significantly greater activation with thermogenic than with psychogenic sweating events. However, a discrete cluster of activation in the anterior hypothalamus/preoptic area was seen only with thermogenic sweating events. These findings suggest that the expected association between sweating events and brain regions implicated in "arousal" may apply selectively to psychogenic sweating; the neural basis for thermogenic sweating events may be subcortical.

Predictive value of sympathetic skin response in diagnosing complex regional pain syndrome: a case-control study

Objective

To investigate the predictive value of the sympathetic skin response (SSR) in diagnosing complex regional pain syndrome (CRPS) by comparing three diagnostic modalities-SSR, three-phasic bone scans (TPBS), and thermography.

Methods

Thirteen patients with severe limb pain were recruited. Among them, 6 were diagnosed with CRPS according to the proposed revised CRPS clinical diagnostic criteria described by the International Association for the Study of Pain. SSR was measured in either the hands or feet bilaterally and was considered abnormal when the latency was prolonged. A positive TPBS finding was defined as diffuse increased tracer uptake on the delayed image. Thermographic findings were considered positive if a temperature asymmetry greater than 1.00℃ was detected between the extremities.

Results

Five of 6 CRPS patients showed prolonged latency on SSR (83% sensitivity). TPBS was positive in the 5 CRPS patients who underwent TPBS (100% sensitivity). Thermography was positive in 4 of 5 CRPS patients who underwent the procedure (80% sensitivity). The remaining 7 non-CRPS patients differed on examination. SSR latencies within normal limit were noted in 4 of 7 non-CRPS patients (57% specificity). Results were negative in 4 of 5 non-CRPS patients who underwent TPBS (80% specificity), and negative in 3 of 5 non-CRPS patients who underwent thermography (60% specificity).

Conclusion

SSR may be helpful in detecting CRPS.

Temporal and thermal variations in site-specific thermoregulatory sudomotor thresholds: precursor versus discharged sweat production

Temporal and thermal differences between the initiation of precursor, eccrine sweat and its surface discharge were investigated during passive heating. Sudomotor activity was evaluated using electrodermal (precursor) and ventilated sweat capsule measurements (dorsal fingers, dorsal hand, forehead, forearm). Passive heating significantly elevated auditory canal (0.5 degrees C) and mean body temperatures (0.9 degrees C). At each site, the precursor sudomotor thresholds occurred at a lower mean body temperature (P < .05), with an average elevation of 0.35 degrees C (SD 0.04). However, discharged thresholds were delayed until this temperature had risen 0.53 degrees C (SD 0.04), producing significant phase delays across sites (mean: 4.1 min [SD 0.5]; P < .05). It is concluded that precise sudomotor threshold determinations require methods that respond to sweat accumulating within the secretory coil, and not discharged secretions, reinforcing the importance of electrodermal techniques.

Physiological response to propranolol and diazepam in chronic anxiety

1 Twelve chronically anxious psychiatric out-patients, comprising six with somatic anxiety and six with psychic anxiety, were treated with (±)-propranolol, diazepam and placebo for one week each in flexible dosage using a balanced cross-over experimental design. 2 After each treatment, in addition to ratings completed by patient and psychiatrist, finger tremor, EEG, averaged auditory evoked response, skin conductance, heart and respiratory rate were measured. 3 Diazepam significantly increased the amount of fast activity (13.5-26 Hz) in the EEG but produced few peripheral effects apart from a reduction in finger tremor. 4 Propranolol had no central physiological effects but reduced both pulse rate and finger tremor. 5 The physiological effects of propranolol in chronic anxiety are different from those of diazepam and therapeutic benefit appears to be due to a direct effect on certain somatic symptoms.

Resonances in the cardiovascular system caused by rhythmical muscle tension

Paced 0.1 Hz breathing causes high-amplitude HR oscillation, triggering resonance in the cardiovascular system (CVS). This oscillation is considered to be a primary therapeutic factor in HRV biofeedback treatments. This study examined whether rhythmical skeletal muscle tension (RSMT) can also cause 0.1 Hz resonance in the CVS, and compared oscillatory reactivity in CVS functions caused by RSMT and paced breathing (PB). Sixteen young healthy participants completed five tasks: baseline, three RSMT tasks at frequencies of 0.05, 0.1, and 0.2 Hz, and a 0.1 Hz PB task. ECG, respiration, finger pulse, and skin conductance data were collected. Results showed that 0.1 Hz RSMT as well as 0.1 Hz PB triggered resonance in the CVS and caused equivalent oscillations in all measured CVS functions, although in women, RSMT compared to PB caused lower HR oscillation. Clinical application of 0.1 Hz RSMT is discussed.

Arterial blood pressure and electrodermal activity in hypertensive and normotensive subjects during inner- and outer-directed attention

Arterial blood pressure (BP), skin conductance level (SCL) and spontaneous fluctuations in skin conductance (SFs) were monitored in 14 subjects with essential hypertension (HT), and 14 matched normotensive (NT) controls during a letter identification task (L) and mental arithmetic (MA). During both tasks, the groups displayed different response patterns such that SFs and BP tended to be negatively correlated in the HT group but were positively correlated in the NT group. No correlation between BT and SCL was obtained in any group during either task. SFs and SCL were positively correlated in the NT group during both tasks whereas no correlation was found in the HT group. The results are consistent with the hypothesis that an increased BP is associated with the rejection of the environment.

Sweat testing to evaluate autonomic function

Sudomotor dysfunction is common in many subtypes of neuropathy but is one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathy. Clinical assessments of sudomotor function include thermoregulatory sweat testing (TST), quantitative sudomotor axon reflex testing (QSART), silicone impressions, the sympathetic skin response (SSR), the acetylcholine sweat-spot test and quantitative direct and indirect axon reflex testing (QDIRT). These testing techniques, when used in combination, can detect and localize pre- and postganglionic lesions, can provide early diagnosis of sudomotor dysfunction and can monitor disease progression or disease recovery. In this article, we describe many of the common clinical tests available for evaluation of sudomotor function with focus on the testing methodology and limitations while providing concrete examples of test results.

Usefulness of galvanic skin reflex monitor in CT-guided thoracic sympathetic blockade for palmar hyperhidrosis

Computed tomography (CT)-guided thoracic sympathetic blockade with ethanol was performed while monitoring sympathetic nerve activity, with an alternating current (AC) galvanic skin reflex (GSR) monitor, in a patient with palmar hyperhidrosis in whom endoscopic thoracic sympathectomy was impossible because of pleural adhesion. Sweating was suppressed after the thoracic sympathetic blockade, and the monitor showed a significant increase in skin resistance. The effect of sympathetic blockade could be evaluated directly and in real time using a GSR monitor.

Impaired sympathetic skin response in chronic obstructive pulmonary disease

The sympathetic skin response (SSR) is considered as one of the indexes of autonomic nervous system functions, especially related with the sudomotor function of unmyelinated sympathetic fibers. SSRs are recorded as the potentials with biphasic or multiphasic waveforms by conventional electromyography. SSRs are evaluated by measuring latency (time from the stimulus to the onset), amplitude, and area (the space under the curve of the waveform). Although dysautonomia is a feature of chronic obstructive pulmonary disease (COPD), as demonstrated by acetylcholine sweat-spot test, there are no data concerning SSR in COPD patients. In this study, we electrophysiologically investigated the sudomotor function of the sympathetic nervous system in patients with COPD. SSRs were recorded in 30 patients with COPD and 21 healthy volunteers. Normal responses were obtained from all subjects in the control group. No response was observed in three patients with COPD. The mean latency, amplitude and area values of the potentials recorded of the remaining 27 patients were compared to the control. The mean latency was longer (p<0.01) and the mean amplitude and area values were lower (p=0.012, p=0.021, respectively) in the patients compared to the control. We also demonstrated significant correlations between the latency, amplitude, or area values of the SSR and two parameters of pulmonary function tests forced expiratory volume one second/forced vital capacity (FEV1/FVC) and FEV1/FVC %. In conclusion, SSR is impaired in patients with COPD, which indicates the dysfunction of the sympathetic nervous system. Furthermore, the degree of impairment in SSR may reflect the severity of airway obstruction in patients with COPD.

Sympathetic skin response in patients with spinal cord injury

PURPOSE

To assess the effectiveness of sympathetic skin response in evaluating peripheral sympathetic nerve activity of patients with spinal cord injury, and to report on the basic properties of sympathetic skin response.

METHODS

Sympathetic skin response evoked by electrical stimulation was recorded from the palms and soles of healthy volunteers and patients with spinal cord injury.

RESULTS

Sympathetic skin response was recorded in 17 healthy volunteers and 14 patients with spinal cord injury. Of the 4 waveforms, the shortest latency was obtained from the palm; the sympathetic skin response was 1.2 to 1.4 ms at all stimulated sites, 1.9 to 2.0 ms at the sole, with a difference of about 0.6 ms between the palm and the sole. None of the patients with spinal cord injury responded at either the upper or lower limbs. In patients with a thoracic cord injury, some responded at the upper limbs but none at the lower limbs; some responded at neither upper nor the lower limbs; and some responded at both upper and lower limbs. The conducting pathway of sympathetic skin response in the spinal cord for the upper limbs descends to the upper thoracic cord (T4-6), and the conducting pathway for the lower limbs departs from the spinal cord at the lower thoracic cord (T9-10).

CONCLUSION

It appears that sympathetic skin response should be used for the evaluation and morbid investigation of the functional abnormalities of the sympathetic nervous system in patients with spinal cord lesions such as spinal cord injuries, cervical spondylosis, and spinal canal stenosis.

Sympathetic skin response in psoriasis and vitiligo

The sympathetic skin response (SSR) which is considered to be one of the indexes of peripheral autonomic nerve function, especially evaluates sudomotor function of unmyelinated sympathetic fibers. This noninvasive technique has been studied in various neurological disorders particularly in peripheral neuropathies and also in some dermatological disorders associated with nervous system involvement. However, literature lacks sufficient data regarding SSR in immunologically mediated skin disorders. We enrolled patients with vitiligo and psoriasis to determine the possible effects of these disorders on SSR. Examination of SSR was performed in 30 patients with psoriasis and 15 patients with vitiligo as well as in 23 healthy volunteers as controls. Right and left median nerves were stimulated successively and responses were recorded from the palms simultaneously. SSR could be obtained from every subject. The groups were not statistically different for the values of the latency, the amplitude, and the area under the negative component of SSR. Our results indicated that vitiligo and psoriasis did not have any significant effects on SSR.

The effects of postmenopausal hormone replacement therapy on sympathetic skin response

OBJECTIVES

To determine the effects of postmenopausal hormone replacement therapy on 'sympathetic skin response' test which is one of the tests to evaluate autonomic functions.

METHODS

Sixty postmenopausal women, 30 of whom taking hormone replacement therapy and the remaining 30 without hormone replacement therapy, were enrolled in this study. Sympathetic skin responses were recorded in each subject by Medelec Premiere electromyograph. Latency and amplitude of sympathetic skin response and area under the negative component of sympathetic skin response were measured and the groups were compared statistically regarding these results.

RESULTS

Latency values of the groups were not significantly different, whilst the difference between the sympathetic skin response amplitudes of the groups, as well as the difference between the measurements of area under the negative component of sympathetic skin response of the groups were statistically significant.

CONCLUSION

The results of the current study seem to indicate that estrogen has a significant inhibitory effect on the sympathetic neuron pool at the spinal cord level.

Comparative assessment of peripheral sympathetic function by postural vasoconstriction arteriolar reflex and sympathetic skin response in NIDDM patients

PURPOSE

The aim of the study was to compare peripheral sympathetic adrenergic and cholinergic nerve function in NIDDM (non-insulin-dependent diabetes mellitus) patients with various degrees of diabetic neuropathy and neuropathic foot ulceration. The parameters used were postural vasoconstriction arteriolar reflex (VAR) and sympathetic skin response (SSR), respectively.

PATIENTS AND METHODS

Forty-seven NIDDM patients were studied. No patients had clinically significant peripheral vascular disease. They were divided according to peripheral somatic neuropathy, assessed by clinical score and vibration perception threshold (VPT). Twenty-two patients showed no significant evidence of peripheral neuropathy and normal VPT (DN-); 15 had signs and symptoms of neuropathy and VPT alteration (DN+); 10 had diabetic neuropathy and foot ulceration (DNU). Twenty-two normal subjects were also examined as a control group. Resting arteriovenous shunt skin blood flow, measured using laser-Doppler flowmetry, and the VAR of the big toe on lowering the foot were studied. Sympathetic skin response was assessed by an EMG apparatus. Autonomic function was also investigated by using standard cardiovascular reflex tests.

RESULTS

Resting blood flow values were similar in the three NIDDM groups and in the control group. VAR to foot lowering was significantly impaired in all NIDDM groups by comparison with controls (72.8 +/- 2.1%, mean +/- SEM), this impairment being progressively more pronounced in DN- (58.8 +/- 2.3%, P < 0.001), DN+ (33.3 +/- 3.0%, P < 0.001 versus DN-) and DNU (8.6 +/- 2.7%, P < 0.001 versus DN+). Sympathetic skin response was assessed in 28 patients and was significantly impaired in DN-compared with the control group (2.53 +/- 0.04 versus 2.71 +/- 0.04 log mcV, P < 0.01). This impairment was severe in the DNU compared with the DN+ group (1.36 +/- 0.05 versus 2.26 +/- 0.04 log mcV, P < 0.005). A positive correlation was found between VAR values and SSR (P < 0.001), and these measurements were also closely correlated with several parameters of central autonomic and somatic neuropathy.

CONCLUSION

These results indicate that peripheral sympathetic adrenergic and cholinergic fibers simultaneously undergo early alterations in diabetic patients, even when there is no clinical neuropathy. Our data also show almost complete abolition of peripheral sympathetic activity in NIDDM patients with foot ulceration.

Electrophysiological tests of autonomic function in patients with idiopathic autonomic failure syndromes

Three electrophysiological tests of autonomic function were performed in patients with autonomic nervous system dysfunction to define test sensitivities and specificities. The skin sympathetic response, Valsalva ratio, and heart rate variation with deep breathing were studied in 10 patients with multiple system atrophy (MSA) and in 7 patients with pure (also called progressive or primary) autonomic failure (PAF); control subjects were 17 normal individuals of similar age. Thirteen patients had abnormal skin sympathetic responses, and 16 had abnormal Valsalva ratios. Fourteen patients had an abnormal variation of the heart rate with deep breathing. Taking the three tests together, binary logistic regression for distinguishing between patients and normal subjects correctly classified 91% of the 33 individuals for whom there were complete data with sensitivity of 88% and specificity of 94%. However, only 69% of the patients could be correctly classified by a logistic regression for discriminating between MSA and PAF. Electromyography (EMG) studies showed that 7 of 8 patients with MSA but only 2 of 7 patients with PAF (both multiparous women) had denervation of the rectal sphincter muscle. The EMG study is, therefore, valuable in men, but has a high false positive rate in women, probably because of pudendal nerve injury from parturition.

Sympathetic skin response and regeneration of sudomotor fibers after complete division of peripheral nerves

Sympathetic skin responses (SSRs) were studied in hands of patients during regeneration of their median or ulnar nerves following complete severance and suture. The SSRs were elicited with electrical stimuli presented to the forearm of the normal side and recorded between the dorsum of the hand and three sites in the innervation area of the two nerves. The amplitude and area of the SSRs were compared to those obtained at the identical points on the uninjured hand. The responses were followed up for 16 months at 1-1.5-month intervals in a group of 6 adults and for 14 months at monthly intervals in 7 children. After an initial absence, the SSRs appeared after about 4 months postoperatively at the most proximal site in the adults and 2-3 months in the children. It progressed subsequently over a 14- or 16-month observation period to less than 50% of the normal side in the adults and to close to 100% in children, fastest and most complete for the proximal recording site, considerably earlier in the children. End-stage recovery studied in another group of 14 adults and 7 children 2-7 years postoperatively reached an average of 80-100% at the most proximal recording site in most adults and children. The intermediate and the distal sites showed less complete return of the SSR. The method of recording SSRs is considered suitable to follow regeneration of the sudomotor fibers in the cut and sutured nerves of the hand.

Measurement of sudomotor fibre regeneration by sympathetic skin response after complete division of peripheral nerves in children

Sympathetic Skin Response (SSR) was measured in 14 paediatric patients (age range 3-15 years, mean 7.2 years) following repair of lacerated upper limb peripheral nerves (median, ulnar or both). All nerves had been completely divided and were repaired by primary epineural repair. Measurements of SSR were made at regular, 1-2 monthly, intervals during nerve regeneration in 6 patients. A further group of 7 patients had single SSR measurements at the end of nerve regeneration (21-63 months). A 4-year-old boy was also followed up from 10 to 21 months following replantation of a proximally amputated right upper limb. The method was first standardised in 16 healthy volunteers (age range 3-17 years, mean 9.4 years). Patients over 6 years of age were also clinically tested for return of sensation. The results show that the objective measurement of sudomotor nerve regeneration in children is possible with this method. They demonstrate its universal acceptance by children as young as 3 years old.

Post-stroke autonomic nervous system function: palmar sympathetic skin responses thirty or more days after cerebrovascular accident

We studied sympathetic nervous system (SNS) function after cerebrovascular accident (CVA) by measuring hypothenar sympathetic skin responses (SSR) to normal or hemiplegic arm electrical stimulation. We anticipated SNS function after CVA to be asymmetric and selected null hypotheses of bilaterally symmetric SSR latencies and amplitudes irrespective of side of stimulation and/or recording. Thirteen patients between ages 44 and 77 years (median 59) were tested between 1 and 72 months (median 15) after CVA. Hypothenar recording and dorsal reference surface electrodes were used. Amplifier bandwidth was set from 0.5 to 100 Hz. Gain was adjusted to allow adequate recognition of the waveforms. Sweep speed was set to 500ms/div. Stimulus width was set to 0.2 ms and intensity was increased stepwise from 10mA initially until optimum responses were obtained. Nonparametric statistics were used to analyze the data. SSRs were present in all patients on both the normal and the hemiplegic sides irrespective of the side of stimulation. Median SSR latency recorded homolaterally to the stimulus site was found to be 80ms shorter than median SSR latency recorded heterolaterally. Median SSR latency in left hemiplegics was found to be 16% longer than in right hemiplegics. Otherwise, neither side of hemiplegia, side of stimulation, side of recording nor any paired combination thereof were found to be significant. Our finding of bilaterally obtainable SSRs after CVA diverges from that of Uncini and colleagues but presumably only reflects the difference in poststroke chronology between the respective samples.

Neurophysiology in Lower Urinary Tract Dysfunction

Although there is a great mass of data about specific aspects of normal vesico-urethral function, the physiology of the lower urinary tract remains poorly understood. Any attempt to write a coherent account of the subject will necessarily reflect the Author's bias. The reader should therefore remember that speculation will often creep in when substance is lacking.

Skin potential recordings during cystometry in spinal cord injured patients

In order to investigate autonomic mechanisms associated with bladder filling and bladder contraction, skin potentials from the hands and the feet of 32 spinal cord injured patients were recorded during cystometry. All had a complete clinical loss of motor and sensory function below the lesion, but in 3 patients, the autonomic lesion was electrophysiologically assessed as incomplete. In patients with a complete autonomic lesion, any rise in intravesical pressure associated with bladder hyperreflexia induced SP responses below the level of the lesion. SP responses were never obtained during bladder filling, as the intravesical pressure remained low. These results tend to confirm those of Guttmann and Whitteridge, but differ in so far as SP responses at the foot were a regular finding in all paraplegic and in most tetraplegic patients. Furthermore, bladder contraction failed to elicit SP responses below the level of the lesion in patients with an incomplete autonomic lesion. This study emphasises the importance of assessing the integrity of the autonomic nervous pathways when dealing with autonomic mechanisms in spinal cord injured patients. The possible relation between SP responses and bladder neck dysfunction is further discussed.

Regional differences in skin blood flow and temperature during total spinal anaesthesia

Three patients were studied to determine the changes in regional skin temperature and blood flow during extensive sympathetic blockade following total spinal anaesthesia (TSA). Skin temperature was measured at the right upper arm, the right anterior chest at the nipple level, the right hand and the foot, using infrared thermography. Skin blood flow of the right upper arm (C6 area) was measured with a laser Doppler flowmeter. The temperature of the truncal area, arm and leg decreased by 1 degree C following TSA, whereas the temperature of the hand and foot increased by 3 degrees C. The mean blood flow in three patients decreased to 26.1, 61.4, 51.7% of the control values 15 min after TSA. Our results indicate that extensive sympathetic nervous blockade during total spinal anaesthesia induces regional different changes in skin temperature and decrease in truncal skin blood flow.

Skin conductance and arousal in the newborn

We measured skin conductance continuously from the sole of a foot in babies of different conceptional ages before, during, and for 10 minutes after a 'heel prick' carried out for routine blood sampling. We studied 82 healthy babies whose gestational and postnatal ages ranged from 25-42 weeks, and 1-73 days. The median skin conductance level (preheel prick) in babies of 40-43 weeks' conceptional age was 0.6 microS (microsiemens) and differed significantly between awake babies (1.2 microS) and those who were asleep (0.5 microS). In contrast babies less than 40 weeks had a significantly lower median skin conductive level (0.3 microS) which was identical in awake and asleep babies. In response to the heel prick all babies became aroused and skin conductance rose sharply and immediately in 21 out of 22 (95%) babies 40-43 weeks' conceptional age, and in seven out of 23 (30%) babies 36-39 weeks. The median rise at one minute in babies of 40-43 weeks was significantly higher than those 36-39 weeks (2.7 microS compared with 0.5 microS). No babies less than 36 weeks had a change in their skin conductance after the heel prick. These results are consistent with the notion that 'emotional sweating' is a function of maturity and does not develop until 36 weeks' conceptional age.

Sympathetic skin response: normal results in different experimental conditions

(1) The sympathetic skin response (SSR) is a slow wave, generated in deep layers of the skin, resulting from reflex activation of the sudomotor sympathetic efferent fibres. The aim of this study was to define experimental conditions, best stimulation and recording procedures, and the criteria for validation of the responses. (2) Thirty normal subjects (aged 25-56) were tested. The stimulation was an electrical pulse train applied to the median nerve at the wrist, a binaural tone burst, or both simultaneously. Records were made with surface electrodes on hand and foot contralateral to the stimulated median nerve. (3) Response shape was most often biphasic in feet, biphasic or triphasic in hands. SSR amplitude was 3.1 +/- 1.8 mV in hands, 1.4 +/- 0.8 mV in feet. Normal mean onset latency was 1.5 +/- 0.08 sec for hand response, 2.05 +/- 0.10 sec for foot response. The mean conduction velocity along peripheral sympathetic nerve fibres was 1.40 +/- 0.14 m/sec in lower limbs. (4) Bimodal stimulation (burst + median) provided responses of larger amplitude. The influence of stimulation intensity was also investigated. A decrease in amplitude and lengthening of latencies were observed after 15-20 min of testing. (5) The criteria for validation of responses are discussed. The importance of central processing time in the response delay is pointed out. In good methodological conditions, SSR would appear to be a simple, effective means of assessing sympathetic sudomotor outflow in central and peripheral nervous system disorders.

Sympathetic discharges in the human supraorbital nerve and their relation to sudo- and vasomotor responses

1. Sympathetic nerve activity occurring as bursts of multi-unit impulses was recorded with tungsten microelectrodes in the supraorbital nerve of awake healthy subjects. Within the fascicular innervation zone on the forehead, skin resistance was measured as an indicator of sweat gland activity, and skin blood flow was measured with laser-doppler flowmetry. 2. At room temperature, there was little or no background burst activity, but arousal stimuli or mental stress evoked bursts followed by a vasodilator response. Provided repeated arousal stimuli were delivered, individual bursts were followed by a decrease in skin resistance. 3. Body heating induced increasing background burst activity. After an initial period without associated electrodermal activity, there were decreases in skin resistance, which showed a positive linear correlation with the amplitude of the preceding burst. Individual bursts were followed by a vasodilator response with an average onset latency of 2.8 s and an average duration of 9.1 s, and rapid increases in blood flow coincided with a marked increase in burst activity. Arousal stimuli evoked bursts followed by both vasodilator and skin resistance responses. 4. During body cooling, there was no background burst activity, but signs of relatively weak, probably neurally mediated vasoconstriction were observed and arousal-evoked bursts were reduced or abolished, as were the associated vasodilator and skin resistance responses. 5. It is concluded that body heating induces active sympathetic vasodilatation in the skin of the human forehead, and that this is either sudomotor-mediated or caused by vasodilator fibres firing in synchrony with sudomotor fibres. A similar sympathetic mechanism probably underlies the vasodilator responses evoked by arousal stimuli and mental stress.

Quantitative noninvasive electrophysiological evaluation of the activity of the cutaneous division of the sympathetic nervous system

The functional status of the cutaneous division of the orthosympathetic nervous system was indirectly and non-invasively assessed by monitoring the skin electrical relative resistance variations (SERV). The advantages of our recording system of second generation were (1) simultaneous recording on two or four channels of the evoked electrodermal response to psychic or to sensorial stimulus; (2) self-balancing system which allows the recording of the relative variation of the electric parameter, i.e. its variation with time; (3) precise determination of the amplitude (omega/s, mu F/s) of the evoked response; (4) reference of the latency time (LT) of the evoked response to the length of the anatomical pathway of the signal giving the autonomic conduction velocity (ACV). Decrease in diabetic autonomic neuropathy of both spontaneous and evoked electrodermal activities suggested their relationship with cutaneous sympathetic activity.

Neuroleptic effects on electrodermal responsivity to soft tones and loud noise in schizophrenia

Electrodermal procedures have consistently yielded two groups of schizophrenic patients--responders and nonresponders--on the basis of their electrodermal responsivity to auditory stimuli. The reliability of this finding has proved to be a cornerstone of autonomic research in schizophrenia. Previous investigators have reported that neuroleptic medications have little or no effect on electrodermal responsivity to mild tones. The current research found that patients receiving neuroleptics with high anticholinergic properties showed significantly less electrodermal responsivity compared with those receiving low anticholinergic neuroleptics. This was true for both loud and mild auditory stimuli.

Sympathetic skin response in diabetic neuropathy

The sympathetic skin response (SSR) was studied in 47 diabetic patients selected for the presence of symptoms and clinical signs of peripheral neuropathy and in 24 normal control subjects. The SSR was present in all controls but was absent at the foot in 66% and at the hand in 27.7% of the diabetic patients. Absence of the SSR failed to correlate with other electrophysiologic parameters on routine nerve conduction and electromyographic studies. Although absent SSR was more often found in patients with symptoms of autonomic dysfunction (P less than 0.05), there was no correlation with any specific symptoms of autonomic involvement. The SSR was frequently absent, at least in the foot, in those patients with abnormal cardiac beat-to-beat variability (expiratory: inspiratory, E:I, ratio) and pupil cycle time (PCT). In addition there was a good correlation between the amplitude of the SSR and the value of the E:I ratio (r = 0.81, P less than 0.001). The SSR may be a valuable adjunct in the assessment of autonomic involvement in diabetic neuropathy, but its sensitivity requires further evaluation.

Skin potentials (SP) recorded from the extremities and genital regions in normal and impotent subjects

Skin potentials (SP) were evoked by peripheral nerve stimulation from the hands and feet of 41 and from the genital skin of 28 male, controls. The same methods were also applied in 10 functionally impotent cases, 32 diabetic impotent and 8 diabetic normopotent cases. The SP was easily obtained from all 3 sites in all normal subjects and in 10 functionally impotent cases. The SP recorded from the genital skin was either absent or abnormal in 53% of diabetic impotent cases with or without polyneuropathy, while the incidence of abnormalities encountered in the hand and/or foot recordings was 28%. In 8 diabetic normopotent cases the SP recorded from the genital and extremity skin were completely normal. SP recorded from the genital skin is a useful method of evaluating the autonomic-sympathetic dysfunction causing impotence, especially in patients who may have autonomic disorders either located in lumbosacral spinal cord and its efferents, or generalized autonomic-peripheral dysfunction.

Disorders of the autonomic nervous system: Part 2. Investigation and treatment

Autonomic function may be adequately tested with noninvasive tests of sympathetic and parasympathetic pathways, including: the response of blood pressure to change in posture and isometric contraction, heart rate response to standing, variation in heart rate with respiration, Valsalva ratio, sweat tests, and plasma noradrenaline measurements. Abnormal results in two or more of these tests indicate autonomic dysfunction. Intraarterial catheterization and tests of vasomotor function are usually required only in doubtful cases or for research purposes. Treatment of autonomic dysfunction is focused primarily on bladder control and control of orthostatic hypotension. Orthostatic hypotension is best treated with physical measures, pharmacologically with 9-alpha-fluorohydrocortisone and dihydroergotamine mesylate. A number of other agents may be tried but results have been less effective.

Peripheral autonomic surface potential. A quantitative technique for recording sympathetic conduction in man

Using EMG equipment with time locked recording and standard averaging facilities we were able to record a previously poorly defined skin potential. The potential, termed by us the peripheral autonomic surface potential (PASP), was recorded from the palmar surface of the hand and the plantar surface of the foot in 30 normal subjects. The PASP usually consisted of a biphasic potential with an initial negative and a later positive peak. It was elicited by randomly timed electrical stimuli over the median nerve at the wrist. The mean palmar PASP latency was 1.52 +/- 0.13 s and the mean plantar PASP latency was 2.07 +/- 0.16 s. The mean palmar and plantar PASP amplitudes were 479 +/- 105 microV and 101 +/- 40 microV, respectively. A mean sympathetic conduction velocity was calculated to be 1.28 +/- 0.18 m/s. In 5 normal subjects a similar technique was used to record a PASP from the volar surface of the left middle finger. Iontophoresis of atropine into the skin under the recording site abolished the PASP in all subjects. Palmar and plantar PASPs were recorded in 10 diabetic patients. The amplitudes (palmar 179 +/- 158 microV, plantar 17 +/- 16 microV) were significantly reduced compared to normals (P less than 0.001). Five patients with unilateral lumbar or cervical sympathectomy were studied. The PASP was absent or markedly reduced on the side of the sympathectomy in all patients.

Sympathetic skin response--a method of assessing unmyelinated axon dysfunction in peripheral neuropathies

The sympathetic skin response (SSR) was measured in 33 patients with peripheral neuropathies and in 30 normal control subjects. Abnormalities of the response were correlated with clinical, pathologic, and EMG observations. The response was usually absent in axonal neuropathies, but present in demyelinating disorders. Abnormalities of the sympathetic skin response did not correlate well with clinical evidence of dysautonomia, but were a reliable indicator of disorders affecting unmyelinated axons.

Development of emotional sweating in the newborn infant

Sweating from the palm and sole occurs independently of ambient temperature but is influenced by emotional factors. It thus provides a useful objective measure of emotional state. The development of this emotional sweating in the newborn was investigated by measuring palmar water loss and relating it to the infant's state of arousal. Although 433 individual measurements were made on 124 babies of gestational age 25 to 41 weeks and postnatal age 15 hours to 9 weeks. Palmar water loss was also recorded continuously in 22 infants undergoing heel prick for routine blood sampling. In babies of 37 weeks' gestation or more, there was a clear relationship between palmar water loss and arousal from the day of birth, and by the third week levels on vigorous crying were comparable with those of an anxious adult. Less mature babies did not show emotional sweating at birth; it was first seen at the equivalent of 36 to 37 weeks' gestation regardless of maturity. Continuous recordings confirmed the cross-sectional data and illustrated the abrupt nature of the response. Emotional sweating could be a useful tool for the assessment of emotional state of the newborn.

Haemodynamic and electrodermal correlates of psychogenic stimuli in hypertensive and normotensive subjects

This study compared tonic and phasic cardiovascular and electrodermal activity in subjects having essential arterial hypertension (HT) with that of sex- and age-matched normotensive (NT) controls. Fourteen subjects of each group were subjected to 'sensory intake' (letter identification) and 'rejection' (mental arithmetic) tasks while recordings were made of: systolic and diastolic arterial blood pressure, hand and forearm blood flows, heart rate, skin conductance level and fluctuations. The rejection task affected more physiological variables in both groups than the intake task did. The reaction pattern was similar in both groups. Except for systolic and diastolic blood pressures tonic cardiovascular and electrodermal activity of the HT group was not different from that of the NT group. The same pattern, although less clear cut, was observed when reactivity was studied. According to analyses based on pressure levels both tasks raised the systolic blood pressure of the HT group, whereas only the rejection task raised systolic blood pressure in the NT group. In contrast, an analyses based on blood pressure changes from base to task indicated that both groups increased systolic blood pressure to both tasks. Since virtually no other differences in reactivity were found, this study offers weak support for the notion that subjects having essential arterial hypertension are pressor hyper-reactors.

A pilot study of the changes of skin electrical conductance in patients undergoing general anaesthesia and surgery

Change of skin electrical conductance have been monitored from induction of anaesthesia to recovery in two groups of patients. The first group receiving inhalational anaesthesia with halothane and spontaneous respiration demonstrated no changes in response to surgical stimulus. Some patients from the second group receiving muscle relaxation and ventilation with nitrous oxide and oxygen without halothane demonstrated changes in response to surgery. The changes are mediated by the sympathetic nervous system and the technique forms a simple monitor of sympathetic activity during surgery.

Diabetic autonomic neuropathy in patients with vascular disease

An attempt has been made to determine the effect on vasomotor tone and sweating of peripheral neuropathy in the feet of diabetics with vascular disease. There was a loss of vasomotor tone in 48 per cent of patients with peripheral neuropathy and in 12 per cent of those without neuropathy (P less than 0.01). Complete loss of sudomotor activity was rare in both groups.

Changes in skin potential level during sleep in psychiatric patients

Skin potential levels and EEG changes were recorded in eight psychiatric patients during three nights of sleep. In a balanced design each patient took amylobarbitone sodium 200 mg, chlordiazepoxide 30 mg and placebo in turn. Skin potential did not distinguish between wakefulness and sleep as measured by the EEG nor did it clearly identify individual sleep stages. However, significant differences in skin potential were found between Awake and Stage I, between Awake and REM sleep and between REM sleep and Stage III/IV. The level was lowest during REM sleep but approached that of wakefulness during slow-wave sleep. These findings are discussed in terms of changes in arousal threshold during sleep. A cautious comment is made on the possible effects of psychiatric diagnoses and drugs.

Research report: Institute of Psychiatry Clinical Psychopharmacology Research Team

In 1960, the National Institute of Mental Health of the U.S.A. provided research support to Professor H. O. Schild of the Department of Pharmacology, University College London (U.C.L.) and to Dr. (now Professor) Michael Shepherd of the Department of Psychiatry, Institute of Psychiatry, University of London, for studies in human psychopharmacology. The research assistants initially employed were Dr. Lorna Wing, Dr. J. D. Montagu, and Dr. Malcolm Lader and work was carried out at U.C.L., the Institute of Psychiatry, and Runwell Hospital, Essex. In 1966, the Medical Research Council assumed responsibility by appointing Dr. Lader to their External Scientific Staff. Other support has come from the Bethlem Research Fund and from the pharmaceutical industry, in particular Roche (U.K.) Ltd. and May and Baker, Ltd. A group of six to eight workers has thus been built up based mainly in the Institute of Psychiatry but with continuing links to U.C.L. At present our team comprises pharmacologists, psychiatrists, psychologists, a physiologist, a chemist, and a mathematician. Several workers from abroad on British Council or Commonwealth Fellowships have been attached to the team at various times, and students for higher degrees such as PhD and MD have been welcomed.