Electroencephalography (EEG) is a non-invasive examination method for the assessment of functional central nervous system (CNS) disturbances. In human medicine it has a special importance as a diagnostic tool for epilepsy. Although many studies were done on the use of EEG for diagnostics of canine central nervous system disorders, the technique is still not applied routinely. The purpose of this paper was to review the use of the electroencephalography in canine neurological disorders of central nervous system diagnosis and assess the future perspectives of this technique in veterinary medicine.

Electroencephalography (EEG) is a non-invasive examination method for the assessment of functional central nervous system (CNS) disturbances. In human medicine it has a special importance as a diagnostic tool for epilepsy. Although many studies were done on the use of EEG for diagnostics of canine central nervous system disorders, the technique is still not applied routinely. The purpose of this paper was to review the use of the electroencephalography in canine neurological disorders of central nervous system diagnosis and assess the future perspectives of this technique in veterinary medicine.

OBJECTIVE To compare intraosseous pentobarbital treatment (IPT) and thoracic compression (TC) on time to circulatory arrest and an isoelectric electroencephalogram (EEG) in anesthetized passerine birds. ANIMALS 30 wild-caught adult birds (17 house sparrows [Passer domesticus] and 13 European starlings [Sturnus vulgaris]). PROCEDURES Birds were assigned to receive IPT or TC (n = 6/species/group). Birds were anesthetized, and carotid arterial pulses were monitored by Doppler methodology. Five subdermal braided-wire electrodes were used for EEG. Anesthetic depth was adjusted until a continuous EEG pattern was maintained, then euthanasia was performed. Times from initiation of euthanasia to cessation of carotid pulse and irreversible isoelectric EEG (indicators of death) were measured. Data (medians and first to third quartiles) were summarized and compared between groups within species. Necropsies were performed for all birds included in experiments and for another 6 birds euthanized under anesthesia by TC (4 sparrows and 1 starling) or IPT (1 sparrow). RESULTS Median time to isoelectric EEG did not differ significantly between treatment groups for sparrows (19.0 and 6.0 seconds for TC and IPT, respectively) or starlings (88.5 and 77.5 seconds for TC and IPT, respectively). Median times to cessation of pulse were significantly shorter for TC than for IPT in sparrows (0.0 vs 18.5 seconds) and starlings (9.5 vs 151.0 seconds). On necropsy, most (14/17) birds that underwent TC had grossly visible coelomic, pericardial, or perihepatic hemorrhage. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that TC might be an efficient euthanasia method for small birds. Digital pressure directly over the heart during TC obstructed venous return, causing rapid circulatory arrest, with rupture of the atria or vena cava in several birds. The authors propose that cardiac compression is a more accurate description than TC for this procedure.

Quantitative electroencephalography (QEEG) was assessed in 5 dogs anesthetized with 1.6% end-tidal concentration of isoflurane and after subsequent administration of the benzodiazepine midazolam (0.2 mg/kg of body weight, IV). Ventilation was controlled to maintain normocapnia. Effect of the benzodiazepine antagonist, flumazenil (0.04 mg/kg, IV), on QEEG in midazolam-isoflurane-anesthetized dogs was determined. Heart rate, arterial blood pressure, esophageal temperature, arterial pH and blood gas tensions, end-tidal CO2 concentration, and end-tidal isoflurane concentration were monitored throughout the study. A 21-lead linked-ear montage was used for recording the EEG data. Quantitative EEG data were stored on an optical disk for later analysis. Values for absolute power of EEG were determined for delta, theta, alpha, and beta-frequencies. Cardiovascular variables remained stable throughout the study. Midazolam administration was associated with decreased absolute power in all frequencies of EEG at all electrode sites. Administration of flumazenil antagonized midazolam-induced decreased absolute power of EEG in all frequencies at all electrode sites. We conclude that QEEG provides a noninvasive, objective measure of midazolam- and flumazenil-induced changes in cortical activity during isoflurane anesthesia.

The central arterial pharmacokinetics of alfentanil, a short-acting opioid agonist, were studied in rabbits, sheep, and dogs after short-duration infusion of the drug. Alfentanil was infused until a set end point (high-amplitude, slow-wave activity on the EEG) was reached. This required a larger alfentanil dose and a higher alfentanil arterial concentration in sheep, compared with rabbits and dogs. The plasma concentration-time data for each animal were fitted, using nonlinear regression, and in all animals, were best described by use of a triexponential function. In this study, differences in the disposition kinetics of alfentanil among the 3 species were found for only distribution clearance and initial distribution half-life. In dogs, compared with rabbits and sheep, the first distribution half-life was longer, probably because of pronounced drug-induced bradycardia (mean +/- SD, 48 +/- 21 beats/min). Distribution clearance was faster in sheep, compared with dogs, also probably because of better blood flow in sheep. Elimination half-life was similar in all species (rabbits, 62.4 +/- 11.3 minutes; sheep, 65.1 +/- 27.1 minutes; dogs, 58.3 +/- 10.3 minutes). This rapid half-life resulted from a small steady-state volume of distribution (rabbits, 908.3 +/- 269.0 ml/kg; sheep, 720.0 +/- 306.7 ml/kg; dogs, 597.7 +/- 290.2 ml/kg) and rapid systemic clearance (rabbits, 19.4 +/- 5.3 ml/min/kg; sheep, 13.3 +/- 3.0 ml/min/kg; dogs, 18.7 +/- 7.5 ml/min/kg). On the basis of these pharmacokinetic variables, alfentanil should have short duration of action in rabbits, sheep, and dogs. This may be beneficial in veterinary practice where rapid recovery would be expected after bolus administration for short procedures or after infusion for longer procedures.

Quantitative electroencephalography was assessed in dogs under controlled, 2% end-tidal isoflurane anesthetic conditions, and each variable at each electrode site was tested for normal distribution. With the quantitative electroencephalographic system used, 16 values for each of 21 electrode sites were evaluated. Absolute power ratios also were evaluated. The methods for quantitative electroencephalographic recording and analysis appear to be readily adaptable to the dog. Most of the data do not conform to a normal distribution. Therefore, distribution-free nonparametric statistics should be used when looking for differences under experimental or clinical conditions. Quantitative electroencephalography appears to be a sensitive noninvasive method that could be used to evaluate brain function under anesthetic, clinical, and experimental settings.

During 1986 and 1987, electroencephalographic examinations were done on 8 dogs with intracranial mass lesions confirmed by computerized tomography, biopsy, necropsy, or a combination of these techniques. Tumor types included 1 astrocytoma, 1 undifferentiated glioma, 2 mixed gliomas, 2 meningiomas, 1 choroid plexus papilloma, and 1 cholesterol granuloma. It was found that no EEG pattern was pathognomonic for tumor type or location. Slow-wave activity was observed in the EEG of most of the dogs; asymmetry in amplitude or frequency was observed in approximately half the cases.

Scalp electrode impedance measurements recorded by wired and wireless electroencephalography (EEG) machines in 7 healthy dogs were compared. Eight recordings resulted in 80 impedance readings from subdermal wire electrodes (locations F7/F8, F3/F4, T3/T4, C3/C4, Fz, and Cz). Impedance values were measured first from the wired and then the wireless EEG machine. Wireless impedance measurements were higher than the wired EEG machine in 79/80 readings (P ≤ 0.05), being on average 2.83 kΩ [P ≤ 0.05, 95% confidence interval (CI): 2.51 to 3.14, SD = 1.42] higher. Impedances from the wired machine ranged between < 0.5 and 9 kΩ (mean = 3.09, median = 2.00, SD = 2.15), whereas impedances from the wireless machine ranged between 2.69 and 6.07 kΩ (mean = 5.92, median = 5.05, SD = 2.59). Despite these differences in impedance measurements, both machines measured similar impedance patterns. The wireless EEG machine's impedance measurements, therefore, should be acceptable for veterinary clinical settings.

Objective- To evaluate physical methods for inducing death during the slaughter of American alligators (Alligator mississippiensis). Animals- 24 captive hatched-and-reared American alligators. Procedures- Baseline electroencephalograms (EEGs) were obtained for awake and anesthetized alligators. Corneal reflex, spontaneous blinking, and EEGs were evaluated after severance of the spinal cord, severance of the spinal cord followed by pithing of the brain, application of a penetrating captive bolt, or application of a nonpenetrating captive bolt (6 alligators/group). Results- Overall, alligators subjected to spinal cord severance alone differed from those subjected to the other techniques. Spinal cord severance alone resulted in postprocedure EEG power values greater than those in anesthetized alligators, whereas the postprocedure EEG power values were isoelectric for the other 3 techniques. Corneal reflex and spontaneous blinking were absent in all alligators immediately after application of a penetrating or nonpenetrating captive bolt. One of 6 alligators had a corneal reflex up to 1 minute after pithing, but all others within that group had immediate cessation of reflexes after pithing. Mean time to loss of spontaneous blinking and corneal reflex for alligators subjected to spinal cord severance alone was 18 minutes (range, 2 to 37 minutes) and 54 minutes (range, 34 to 99 minutes), respectively. Conclusions and Clinical Relevance- Spinal cord severance followed by pithing of the brain and application of a penetrating or nonpenetrating captive bolt appeared to be humane and effective techniques for inducing death in American alligators, whereas spinal cord severance alone was not found to be an appropriate method.

Objective: To evaluate the influence of various anesthetic protocols and 3 multiples of isoflurane minimum alveolar concentration (MAC) before and after supramaximal stimulation on electroencephalographic (EEG) variables in dogs. Animals: 6 healthy adult Beagles (mean ± SD body weight, 16.3 ± 1.0 kg). Procedures: All dogs underwent 3 anesthesia sessions with a minimum of 1 week separating sessions: isoflurane alone, isoflurane and a constant rate infusion of dexmedetomidine (3 μg/kg/h, IV; ID), and isoflurane and a constant rate infusion of remifentanil (18 μg/kg/h, IV; IR). The MAC of isoflurane was determined via supramaximal electrical stimulation. Quantitative variables (frequency bands and their ratios, median frequency, 95% spectral edge frequency [SEF], and an EEG index) were determined directly before and after supramaximal stimulation at 0.75, 1.0, and 1.5 times the MAC for each session of 20-second epochs. Results: Mean ± SD isoflurane MACs for isoflurane alone, ID, and IR were 1.7 ± 0.3%, 1.0 ± 0.1%, and 1.0 ± 0.1%, respectively. Prestimulation 95% SEF decreased significantly with increasing MAC during the isoflurane alone and ID sessions. Significant decreases in δ frequency band (0.5 to 3.5 Hz) presence and significant increases in β frequency band (> 12.5 Hz) presence, median frequency, and 95% SEF after stimulation were dependent on the MAC and anesthetic protocol. The EEG index had the strongest correlation with increasing MAC during the isoflurane-alone session (ρ = −0.89) and the least in the IR session (ρ = −0.15). Conclusions and Clinical Relevance: Anesthesia with isoflurane alone resulted in the greatest overall EEG depression of all protocols. Use of remifentanil depressed the EEG response to nociceptive stimulation more strongly than did dexmedetomidine. The EEG variables evaluated did not appear useful when used alone as indicators of anesthetic depth in dogs.