Spinal Cord Motoneuron Excitability during Isoflurane and Nitrous Oxide Anesthesia

1997 ◽  
Vol 86 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Henry H. Zhou ◽  
Mahesh Mehta ◽  
Arturo A. Leis
Keyword(s):  
Spinal Cord ◽  
Nitrous Oxide ◽  
Wave Amplitude ◽  
Specific Effect ◽  
H Reflex ◽  
Reflex Amplitude ◽  
Isoflurane Concentration ◽  
Human Spinal Cord ◽  
Motoneuron Excitability ◽  
F Wave

Background Recent evidence suggests that the spinal cord is an important site of anesthesia that is necessary for surgical immobility, but the specific effect of anesthetics within the spinal cord is unclear. This study assessed the effect of isoflurane and nitrous oxide on spinal motoneuron excitability by monitoring the H-reflex and the F wave. Methods Eight adult patients, categorized as American Society of Anesthesiologists physical status 1 or 2, who were undergoing elective orthopaedic surgery were anesthetized with 0.6, 0.8, 1.0, and 1.2 times the estimated minimum alveolar concentration (MAC) of isoflurane. Nitrous oxide was added in graded concentrations of 30%, 50%, and 70%, whereas the isoflurane concentration was decreased to maintain a total MAC of 1. The H-reflex of the soleus muscle and the F wave of the abductor hallucis muscle were measured before anesthesia and 15 min after each change of anesthetic concentration. Four or more trials of the H-reflex and 18 trials of the F wave were recorded at each concentration of anesthesia. The effect of the anesthetics on the H-reflex and F wave was analyzed using. Dunnett's test. Results H-reflex amplitude was decreased to 48.4 +/- 18.6% of preanesthesia level at 0.6 MAC isoflurane and to 33.8 +/- 19.1% when isoflurane concentration increased from 0.6 MAC to 1.2 MAC. F wave amplitude and persistence decreased to 52.2 +/- 33.6% and 44.4 +/- 26% of baseline at 0.6 MAC isoflurane, and to 33.8 +/- 26% and 21.7 +/- 22.8% at 1.2 MAC isoflurane. Isoflurane plus nitrous oxide (total 1 MAC) decreased H-reflex amplitude to 30.4-33.3% and decreased F wave persistence to 42.8-56.3% of baseline. Conclusions Both isoflurane alone and isoflurane plus nitrous oxide decrease H-reflex and F-wave amplitude and F-wave persistence. These effects suggest that isoflurane and nitrous oxide decrease motoneuronal excitability in the human spinal cord. This may play an important role in producing surgical immobility.

Suppression of Spinal Cord Motoneuron Excitability Correlates with Surgical Immobility during Isoflurane Anesthesia 

1998 ◽  
Vol 88 (4) ◽  
pp. 955-961 ◽  
Author(s):  
Henry H. Zhou ◽  
Tsen-Tsen Jin ◽  
Binsheng Qin ◽  
Herman Turndorf
Keyword(s):  
Spinal Cord ◽  
Wave Amplitude ◽  
H Reflex ◽  
Movement Response ◽  
Electric Stimulus ◽  
Reflex Amplitude ◽  
Isoflurane Concentration ◽  
Anesthetic Action ◽  
F Wave ◽  
End Tidal

Background Recent evidence suggests that the spinal cord is an important site of anesthetic action that produces surgical immobility. Inhalation anesthetics depress the Hoffmann's reflex (H reflex) and F wave, indicating spinal motoneuron suppression. The aim of this study was to assess the correlation between isoflurane-induced immobility and H- and F-wave suppression. Methods The baseline H reflex and F wave were measured before anesthesia in 15 adult patients. After induction, 1% end-tidal isoflurane was maintained for 20 min before the H and F waves were reelicited. Using an electric stimulus applied to the forearm and grading the response as movement or no movement, the authors increased or decreased the isoflurane concentration in 0.1% steps, depending on the movement responses. The H and F waves were recorded 20 min after each change of isoflurane concentration. The correlation between H- and F-wave suppression and surgical immobility was analyzed using a paired t test with Bonferroni correction. Results H-reflex amplitude (2.74 +/- 1.63 mV) and F-wave persistence (70.69 +/- 26.19%) at the highest isoflurane concentration that allowed movement response to a stimulus are different (P < 0.01) from these (1.97 +/- 1.46 mV; 43.16 +/- 22.91%) at the lowest isoflurane concentration that suppressed response. At 0.8% isoflurane, the H-reflex amplitude was 3.69 +/- 1.83 mV with movement and 1.01 +/- 1.14 mV without movement (P < 0.01); F-wave amplitude was 0.29 +/- 0.15 mV with movement and 0.11 +/- 0.06 mV without movement (P < 0.01); F-wave persistence was 80 +/- 22.36% with movement and 34.9 +/- 25.75% without movement (P < 0.01). Conclusions The degree of H- and F-wave amplitude and F-wave persistence suppression correlates with movement response, suggesting that isoflurane-suppressive action in the spinal cord plays a significant role in producing surgical immobility.

scholarly journals Presynaptic and Postsynaptic Effects of the Anesthetics Sevoflurane and Nitrous Oxide in the Human Spinal Cord

2007 ◽  
Vol 107 (4) ◽  
pp. 553-562 ◽  
Author(s):  
Jan H. Baars ◽  
Michael Benzke ◽  
Falk von Dincklage ◽  
Josephine Reiche ◽  
Peter Schlattmann ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Nitrous Oxide ◽  
Presynaptic Inhibition ◽  
Femoral Nerve ◽  
Volatile Anesthetic ◽  
H Reflex ◽  
Receptor Subtype ◽  
Gamma Aminobutyric Acid ◽  
Human Spinal Cord ◽  
Two Parameters

Background Reduced spinal excitability contributes to the suppression of movement responses to noxious stimuli during the anesthetic state. This study examines and compares presynaptic and postsynaptic effects of two anesthetics in the human spinal cord. Methods The authors tested two parameters during the administration of 0.8 vol% sevoflurane or 40 vol% nitrous oxide compared with control states before and after drug administration: (1) the size of the soleus H reflex (integrating presynaptic and postsynaptic effects) at increasing stimulus intensities (recruitment curve) and (2) the amount of presynaptic inhibition on Ia afferents of the quadriceps femoris, evaluated by the heteronymous facilitation of the soleus H reflex caused by a conditioning stimulation of the femoral nerve. The study was performed in 10 subjects for each drug. Results At the chosen concentrations, the maximum H reflex was reduced by 26.3 +/- 8.4% (mean +/- SD) during sevoflurane and by 33.5 +/- 15.6% during nitrous oxide administration. The averaged recruitment curves were similarly depressed under the influence of the two drugs. The reduction of H-reflex facilitation was significantly stronger for sevoflurane (28.8 +/- 20.0%) than for nitrous oxide administration (6.2 +/- 26.4%). Conclusions These results demonstrate in humans presynaptic effects of the volatile anesthetic sevoflurane but not of nitrous oxide. A possible explanation for this difference may be the different potency of the respective drugs in enhancing gamma-aminobutyric acid type A receptor-mediated inhibition, because presynaptic inhibition in the spinal cord involves this receptor subtype.

37. H-reflex and F-wave of the patients of spinal cord injury before and after intrathecal baclofen injection

2010 ◽  
Vol 121 (7) ◽  
pp. e27
Author(s):  
Katsuhiro Mizuno ◽  
Kazushige Hasegawa ◽  
Osamu Uemura ◽  
Daisuke Matsuura ◽  
Masako Katahira ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Intrathecal Baclofen ◽  
H Reflex ◽  
Cord Injury ◽  
Before And After ◽  
F Wave

scholarly journals Effect of cervicolumbar coupling on spinal reflexes during cycling after incomplete spinal cord injury

2018 ◽  
Vol 120 (6) ◽  
pp. 3172-3186 ◽  
Author(s):  
R. Zhou ◽  
B. Parhizi ◽  
J. Assh ◽  
L. Alvarado ◽  
R. Ogilvie ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
H Reflex ◽  
Spinal Reflexes ◽  
Incomplete Spinal Cord Injury ◽  
Reflex Amplitude ◽  
Arm Cycling ◽  
Cord Injury ◽  
Leg Cycling ◽  
Cycling Training

Spinal networks in the cervical and lumbar cord are actively coupled during locomotion to coordinate arm and leg activity. The goals of this project were to investigate the intersegmental cervicolumbar connectivity during cycling after incomplete spinal cord injury (iSCI) and to assess the effect of rehabilitation training on improving reflex modulation mediated by cervicolumbar pathways. Two studies were conducted. In the first, 22 neurologically intact (NI) people and 10 people with chronic iSCI were recruited. The change in H-reflex amplitude in flexor carpi radialis (FCR) during leg cycling and H-reflex amplitude in soleus (SOL) during arm cycling were investigated. In the second study, two groups of participants with chronic iSCI underwent 12 wk of cycling training: one performed combined arm and leg cycling (A&L) and the other legs only cycling (Leg). The effect of training paradigm on the amplitude of the SOL H-reflex was assessed. Significant reduction in the amplitude of both FCR and SOL H-reflexes during dynamic cycling of the opposite limbs was found in NI participants but not in participants with iSCI. Nonetheless, there was a significant reduction in the SOL H-reflex during dynamic arm cycling in iSCI participants after training. Substantial improvements in SOL H-reflex properties were found in the A&L group after training. The results demonstrate that cervicolumbar modulation during rhythmic movements is disrupted in people with chronic iSCI; however, this modulation is restored after cycling training. Furthermore, involvement of the arms simultaneously with the legs during training may better regulate the leg spinal reflexes.NEW & NOTEWORTHY This work systematically demonstrates the disruptive effect of incomplete spinal cord injury on cervicolumbar coupling during rhythmic locomotor movements. It also shows that the impaired cervicolumbar coupling could be significantly restored after cycling training. Actively engaging the arms in rehabilitation paradigms for the improvement of walking substantially regulates the excitability of the lumbar spinal networks. The resulting regulation may be better than that obtained by interventions that focus on training of the legs only.

TIME COURSE OF H-REFLEX AMPLITUDE AFTER SPINAL CORD REINFORCEMENT MANEUVERS (SCRM)

1997 ◽  
Vol 76 (2) ◽  
pp. 162
Author(s):  
Elmer G. Pinzon ◽  
Tien-Yow Chuang ◽  
Faye Y. Chiou-Tan ◽  
Stephen M. Tuel
Keyword(s):  
Spinal Cord ◽  
Time Course ◽  
H Reflex ◽  
Reflex Amplitude

Mechanisms within the spinal cord are involved in the movement-induced attenuation of an H reflex in the dog

1996 ◽  
Vol 76 (5) ◽  
pp. 3589-3592 ◽  
Author(s):  
J. E. Misiaszek ◽  
J. K. Barclay ◽  
J. D. Brooke
Keyword(s):  
Spinal Cord ◽  
H Reflex ◽  
Spinal Transection ◽  
Contralateral Limb ◽  
Reflex Amplitude ◽  
Contralateral Knee ◽  
Passive Rotation

1. H reflexes were elicited in the second interosseous muscle of the hindpaw of the anesthetized dog during passive rotation of the shank about the ipsilateral or contralateral knee. Reflexes sampled at four points in the cycle of movement were compared with stationary controls. For both the ipsilateral and contralateral limb manipulations, reflexes were significantly reduced (P < 0.05) across the cycle of movement. Position-related modulation of the reflex amplitude was not detected (P > 0.05) in either instance. 2. The experiments were then repeated after the spinal transection of each animal at the level of T13. Passive rotation about either the ipsilateral or contralateral knee significantly attenuated (P < 0.05) the H reflex across a cycle of movement in the spinal dog. There was little difference in the amount of inhibition produced by the movement between the intact and spinal animals. On average, the reflex was attenuated 29 +/- 2.4% (mean +/- SE) in the intact animals and 32 +/- 2.1% in the spinal animals. 3. It is concluded that passive rotation about the knee of either leg leads to suppression of the H reflex of the second interosseous muscle both in the ipsilateral, moving leg and the contralateral, stationary one. This reflex suppression occurs across the cycle of movement. The mediating circuitry lies within the spinal cord, caudal to T13.

Memory traces in primate spinal cord produced by operant conditioning of H-reflex

1989 ◽  
Vol 61 (3) ◽  
pp. 563-572 ◽  
Author(s):  
J. R. Wolpaw ◽  
C. L. Lee
Keyword(s):  
Spinal Cord ◽  
Operant Conditioning ◽  
Internal Control ◽  
H Reflex ◽  
Triceps Surae ◽  
Reflex Response ◽  
Reflex Amplitude ◽  
Memory Traces ◽  
Spinal Stretch Reflex ◽  
Root Stimulation

1. Study of memory traces in higher animals requires experimental models possessing well-localized and technically accessible memory traces--plasticity responsible for behavioral change, not dependent on control from elsewhere, and open to detailed investigation. Our purpose has been to develop such a model based on the wholly spinal, largely monosynaptic path of the spinal stretch reflex. Previous studies described operant conditioning of this reflex and of its electrical analog, the H-reflex. In this study, we sought to determine whether conditioning causes changes in the spinal cord that affect the reflex and are not dependent on continued supraspinal influence, and thus qualify as memory traces. 2. Sixteen monkeys underwent chronic conditioning of the triceps surae H-reflex. Eight were rewarded for increasing H-reflex amplitude (HR increases mode), and eight were rewarded for decreasing it (HR decreases mode). In each animal, the other leg was an internal control. Over several months of conditioning, H-reflex amplitude in the conditioned leg rose in HR increases animals and fell in HR decreases animals. H-reflex amplitude in the control leg changed little. 3. After HR increases or HR decreases conditioning, each animal was deeply anesthetized and surgically prepared. The reflex response to supramaximal dorsal root stimulation was measured from the triceps surae nerve as percent of response to supramaximal ventral root stimulation, which was the maximum possible response. Data from both legs were collected before and for up to 3 days after thoracic (T9-10) cord transection. The animal remained deeply anesthetized throughout and was killed by overdose. 4. The reflex asymmetries produced by conditioning were still present several days after transection removed supraspinal influence: reflexes of HR increases animals were significantly larger in HR increases legs than in control legs and reflexes of HR decreases animals were significantly smaller in HR decreases legs than in control legs. 5. Reflex amplitude was much greater in the control legs of anesthetized HR decreases animals than in the control legs of anesthetized HR increases animals. 6. Chronic conditioning had at least two effects on the spinal cord. The first effect, task-appropriate reflex asymmetry, was evident both in the awake behaving animal and in the anesthetized transected animal. The second effect, larger control leg reflexes in HR decreases than in HR increases animals, was evident only in the anesthetized animal. By removing supraspinal control, anesthesia and transection revealed a previously hidden effect of conditioning.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Simultaneous Cervical and Lumbar Spinal Cord Stimulation Induces Facilitation of Both Spinal and Corticospinal Circuitry in Humans

2021 ◽  
Vol 15 ◽  
Author(s):  
Behdad Parhizi ◽  
Trevor S. Barss ◽  
Vivian K. Mushahwar
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Stimulation ◽  
Motor Evoked Potential ◽  
H Reflex ◽  
Spinal Reflex ◽  
Lumbar Spinal Cord ◽  
Reflex Amplitude ◽  
Leg Cycling ◽  
Lumbar Spinal ◽  
Neurologically Intact

Coupling between cervical and lumbar spinal networks (cervico-lumbar coupling) is vital during human locomotion. Impaired cervico-lumbar coupling after neural injuries or diseases can be reengaged via simultaneous arm and leg cycling training. Sensorimotor circuitry including cervico-lumbar coupling may further be enhanced by non-invasive modulation of spinal circuity using transcutaneous spinal cord stimulation (tSCS). This project aimed to determine the effect of cervical, lumbar, or combined tSCS on spinal reflex (Hoffmann [H-]) and corticospinal (motor evoked potential [MEP]) excitability during a static or cycling cervico-lumbar coupling task. Fourteen neurologically intact study participants were seated in a recumbent leg cycling system. H-reflex and MEP amplitudes were assessed in the left flexor carpi radialis (FCR) muscle during two tasks (Static and Cycling) and four conditions: (1) No tSCS, (2) tSCS applied to the cervical enlargement (Cervical); (3) tSCS applied to the lumbar enlargement (Lumbar); (4) simultaneous cervical and lumbar tSCS (Combined). While cervical tSCS did not alter FCR H-reflex amplitude relative to No tSCS, lumbar tSCS significantly facilitated H-reflex amplitude by 11.1%, and combined cervical and lumbar tSCS significantly enhanced the facilitation to 19.6%. Neither cervical nor lumbar tSCS altered MEP amplitude alone (+4.9 and 1.8% relative to legs static, No tSCS); however, combined tSCS significantly increased MEP amplitude by 19.7% compared to No tSCS. Leg cycling alone significantly suppressed the FCR H-reflex relative to static, No tSCS by 13.6%, while facilitating MEP amplitude by 18.6%. When combined with leg cycling, tSCS was unable to alter excitability for any condition. This indicates that in neurologically intact individuals where interlimb coordination and corticospinal tract are intact, the effect of leg cycling on cervico-lumbar coupling and corticospinal drive was not impacted significantly with the tSCS intensity used. This study demonstrates, for the first time, that tonic activation of spinal cord networks through multiple sites of tSCS provides a facilitation of both spinal reflex and corticospinal pathways. It remains vital to determine if combined tSCS can influence interlimb coupling after neural injury or disease when cervico-lumbar connectivity is impaired.

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