Biomedical subjects

Carmen L Dominguez

Publications and source records attributed to Carmen L Dominguez.

4 recordsLinked to original sources

PubMed2005

The effect of isoflurane and halothane on electroencephalographic activation elicited by repetitive noxious c-fiber stimulation.

Windup is the progressive increase in neuronal response to a repetitive noxious stimulus. This response is most often observed in the spinal cord, but it is unclear how this response is manifested in supraspinal structures. We investigated the effects of isoflurane and halothane on electroencephalographic responses to repetitive noxious electrical stimuli (20 pulses at 0.1, 1 and 3 Hz) applied to the tail in rats. Halothane and isoflurane concentrations were adjusted to 0.8 and 1.2 minimum alveolar concentration (MAC), where MAC is the concentration needed to prevent gross and purposeful movement in 50% of animals. At 0.8 MAC halothane, the 3 Hz stimulus caused electroencephalographic (EEG) activation primarily by increasing the median edge frequency (MEF), while at 1.2 MAC halothane the spectral edge frequency (SEF) was increased by the 1 and 3 Hz stimuli, and the MEF was increased by the 3 Hz stimuli. At 0.8 MAC isoflurane, the 1 and 3 Hz stimuli evoked EEG activation by increasing the MEF and SEF, while at 1.2 MAC only the MEF was increased by the 1 Hz stimulus. No EEG activation occurred with the 0.1 Hz repetitive stimulus with either isoflurane or halothane. These data suggest that repetitive electrical stimulation normally associated with windup in spinal neurons can evoke EEG activation.

Anesthetics, Inhalation↗

PubMed2005

Drastic decrease in isoflurane minimum alveolar concentration and limb movement forces after thoracic spinal cooling and chronic spinal transection in rats.

BACKGROUND: Individuals with spinal cord injury may undergo multiple surgical procedures; however, it is not clear how spinal cord injury affects anesthetic requirements and movement force under anesthesia during both acute and chronic stages of the injury. METHODS: The authors determined the isoflurane minimum alveolar concentration (MAC) necessary to block movement in response to supramaximal noxious stimulation, as well as tail-flick and hind paw withdrawal latencies, before and up to 28 days after thoracic spinal transection. Tail-flick and hind paw withdrawal latencies were measured in the awake state to test for the presence of spinal shock or hyperreflexia. The authors measured limb forces elicited by noxious mechanical stimulation of a paw or the tail at 28 days after transection. Limb force experiments were also conducted in other animals that received a reversible spinal conduction block by cooling the spinal cord at the level of the eighth thoracic vertebra. RESULTS: A large decrease in MAC (to </= 40% of pretransection values) occurred after spinal transection, with partial recovery (to approximately 60% of control) at 14-28 days after transection. Awake tail-flick and hind paw withdrawal latencies were facilitated or unchanged, whereas reflex latencies under isoflurane were depressed or absent. However, at 80-90% of MAC, noxious stimulation of the hind paw elicited ipsilateral limb withdrawals in all animals. Hind limb forces were reduced (by >/= 90%) in both chronic and acute cold-block spinal animals. CONCLUSIONS: The immobilizing potency of isoflurane increases substantially after spinal transection, despite the absence of a baseline motor depression, or "spinal shock." Therefore, isoflurane MAC is determined by a spinal depressant action, possibly counteracted by a supraspinal facilitatory action. The partial recovery in MAC at later time points suggests that neuronal plasticity after spinal cord injury influences anesthetic requirements.

Anesthetics, Inhalation↗

PubMed2005

Isoflurane disrupts central pattern generator activity and coordination in the lamprey isolated spinal cord.

BACKGROUND: Although volatile anesthetics such as isoflurane can depress sensory and motor neurons in the spinal cord, movement occurring during anesthesia can be coordinated, involving multiple limbs as well as the head and trunk. However, it is unclear whether volatile anesthetics depress locomotor interneurons comprising central pattern generators or disrupt intersegmental central pattern generator coordination. METHODS: Lamprey spinal cords were excised during anesthesia and placed in a bath containing artificial cerebrospinal fluid and D-glutamate to induce fictive swimming. The rostral, middle, and caudal regions were bath-separated using acrylic partitions and petroleum jelly, and in each compartment, the authors recorded ventral root activity. The authors selectively delivered isoflurane (0.5, 1, and 1.5%) only to the middle segments of the spinal cord. Spectral analyses were then used to assess isoflurane effects on central pattern generator activity and coordination. RESULTS: Isoflurane dose-dependently reduced fictive locomotor activity in all three compartments, with 1.5% isoflurane nearly eliminating activity in the middle compartment and reducing spectral amplitudes in the anesthetic-free rostral and caudal compartments to 23% and 31% of baseline, respectively. Isoflurane decreased burst frequency in the caudal compartment only, to 53% of baseline. Coordination of central pattern generator activity between the rostral and caudal compartments was also dose-dependently decreased, to 42% of control at 1.5% isoflurane. CONCLUSION: Isoflurane disrupts motor output by reducing interneuronal central pattern generator activity in the spinal cord. The effects of isoflurane on motor output outside the site of isoflurane application were presumably independent of effects on sensory or motor neurons.

Anesthetics, Inhalation↗

PubMedDate not supplied

An injection from the past: fluoroscopic evidence of remote injections of radiopaque substances.

OBJECTIVE: Although uncommon, residual effects from contrast agents used more than 2 decades ago are possible. This case report is to alert clinicians to the implications of residual oil-based ionic contrast agents in the intrathecal space. CASE REPORT: A 70-year-old female with evidence of degenerative disc disease underwent a series of lumbar epidural steroid injections. Fluoroscopy during the procedure revealed diffuse residual intrathecal iophendylate (Pantopaque) dye. We were able to demonstrate unrestricted epidural spread of 1 mL iohexol (Omnipaque 180) alongside the preexisting dye. CONCLUSIONS: The goal of this case report is to highlight the potential of residual myelographic dye to complicate interventional procedures. Such residual dye can increase the level of difficulty in performing interventional pain treatments and perhaps the rate of complications associated with epidural injections, such as dural puncture. The presence of large amounts of residual oil-based intrathecal dye can lead to erroneous interpretations of the dye patterns as intraspinal lipoma or hemorrhage. As a consequence, the patient can be submitted to unnecessary diagnostic and therapeutic interventions. In addition, concerns of worsening oil-based dye-induced arachnoiditis with the use of epidural steroid injections can complicate the treatment of patients with back pain.

Adrenal Cortex Hormones↗