A new method for determining levels of sedation in dogs: A pilot study with propofol and a novel neuroactive steroid anesthetic.

BACKGROUND: Different levels of consciousness are required in order to perform different medical procedures. Sedation scales established to objectively define various levels of sedation in humans have not been thoroughly characterized in non-human species. Postural changes in rats or dogs are useful as gross measures of sedation but are inadequate for quantitative assessment since graded levels of sedation are difficult to delineate and obscured by movement abnormalities. NEW METHOD: A new canine sedation scoring (CSS) method was developed based on the modified observer's assessment of alertness and sedation score (MOAA/S) used in humans. The method employed a combination of physical, auditory and somatosensory stimuli of increasing intensity. Cardiovascular, respiratory, and a neurophysiological measure of sedation (bispectral index: BIS) data were recorded. Validation studies were performed following intravenous loading and constant rate infusion of propofol or a novel synthetic neuroactive steroid (SGE-746). RESULTS: Four levels of consciousness were identified: 1) Awake, 2) Moderate Sedation (MS), 3) Deep Sedation (DS) and 4) General Anesthesia (GA). Cardiorespiratory measurements obtained after bolus administration of propofol and SGE-746 and at the end of each CRI remained within normal limits. Canine sedation scores correlated with BIS for SGE-746. SGE-746 exhibited a more gradual exposure-response relationship than propofol. Larger increases in the plasma concentration from awake values were required to achieve different levels of sedation with SGE-746 compared to propofol. COMPARISON WITH EXISTING METHODS: No other canine sedation scoring methods are widely accepted. CONCLUSION: A CSS method, based on the human MOAA/S scale defined four levels of consciousness in dogs and provided better resolution of sedation depth than BIS alone.

Efficacy of a mephentermine-based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle.

The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY® INJETÁVEL (POT), a mephentermine-based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized-complete-block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume-matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six-day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end-tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady-state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post-treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dtmax : +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dtmin : +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo-control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection.

Emergence from anesthesia in the prone versus supine position in patients undergoing lumbar surgery.

BACKGROUND: Conventional supine emergence in patients undergoing prone lumbar surgery frequently results in tachycardia, hypertension, coughing, and loss of monitoring as the patient is rolled supine. The prone position might facilitate a smoother emergence because the patient is not disturbed. No data describe this technique. METHODS: Fifty patients were anesthetized with fentanyl, nitrous oxide, isoflurane, and rocuronium. By the conclusion of surgery, all patients achieved spontaneous ventilation and full reversal of neuromuscular blockade in the prone position, as the volatile anesthetic level was reduced. Baseline heart rate and mean arterial pressure were recorded. Patients were then randomized at time 0 to the supine (n = 24) or prone (n = 21) position as 100% oxygen was administered. Patients in the supine position were then rolled over, while those in the prone position remained undisturbed. Heart rate, mean arterial pressure, and coughs were recorded until extubation. Tracheas were extubated on eye opening or purposeful behavior. RESULTS: When compared with the supine group, prone patients had significantly less increase in heart rate (P = 0.0003, maximum increase 9.3 vs. 25 beats/min), less increase in mean arterial pressure (P = 0.0063, maximum increase 4.8 vs. 19 mmHg), less coughing (P = 0.0004, 7.0 vs. 23 coughs), and fewer monitor disconnections (P < 0.0001). Time to extubation from time 0 was similar (4.0 vs. 3.7 min, prone vs. supine). No one required airway rescue. There was no significant difference in need for restraint (three prone, four supine). CONCLUSIONS: Prone emergence and extubation is associated with less hemodynamic stimulation, less coughing, and less disruption of monitors, without specifically observed adverse effects, when compared with conventional supine techniques.