PubMed · 7818074
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P J Duff, R A Rollison, T W Lee. 1994. Selectatec problems: again and again.. https://pubmed.ncbi.nlm.nih.gov/7818074/
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OBJECTIVE: To examine the physiologic effects of inhalation anesthesia in aquatic turtles to improve anesthetic techniques and postanesthetic monitoring. DESIGN: Retrospective case series. ANIMALS: 9 Kemp's ridley sea turtles. PROCEDURE: Isoflurane was used as the general anesthetic during 14 minor surgical procedures. Turtles were orotracheally intubated, and a surgical plane of anesthesia was maintained with 2.7 +/- 0.4% (mean +/- SE) isoflurane. The duration of anesthesia was 131 +/- 12 minutes. Pulse rate, blood pressure, blood gases (PaO2 and PaCO2) and pH, blood lactic acid concentration, and capnography were used to evaluate the physiologic responses of sea turtles to isoflurane. RESULTS: An isoflurane concentration of 3.4 +/- 0.3% provided anesthetic induction in 7 +/- 1 minutes. The mean duration of the recovery phase was 241 +/- 31 minutes. The duration of the recovery phase was not affected by the duration of anesthesia, type of carrier gas, method of ventilatory weaning, or use of selected pharmacologic agents. The recovery phase was characterized by hypoxemia, progressive acidemia, hypercapnia, and lactic acidosis. Awakening in the turtles was preceded by a characteristic tachycardia and tachypnea. All sea turtles recovered from isoflurane anesthesia without apparent adverse effects within 24 hours. CLINICAL IMPLICATIONS: Isoflurane appears to be safe and effective in providing surgical anesthesia in turtles that require a timely return to an aquatic environment. This study should assist veterinarians in predicting the physiologic responses of aquatic turtles to inhalation agents.
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BACKGROUND: In contrast to that of inhalational anesthetics, quantitation of anesthetic depth for intravenous agents has not been well defined. In this study, using rodents, the relationship between the constant plasma thiopental concentrations and the clinical response to multiple nociceptive stimuli were investigated characterizing the anesthetic state from light sedation to deep anesthesia and correlated to the degree of electroencephalogram (EEG) drug effect. METHODS: Thirty rats were instrumented with chronically implanted EEG electrodes, arterial and venous catheters. A computer-driven infusion pump was used to rapidly attain and then maintain constant, target plasma thiopental concentrations ranging from 7 to 100 micrograms/ml. Three different target plasma thiopental concentrations were achieved in each rat. Electroencephalographic effects were monitored with aperiodic waveform analysis. The following nociceptive stimuli were applied: (1) unprovoked righting reflex, (2) provoked righting reflex, (3) noise stimulus, (4) tail clamping with an alligator clip, (5) constant tail pressure with an analgesiameter, (6) corneal reflex, and (7) tracheal intubation. For tail clamping, tail pressure, and intubation, either purposeful extremity movement or abdominal muscle contraction response was noted to be present or absent. The clinical responses (present or absent) were modeled using logistic regression to estimate the Cp50, the plasma thiopental concentration with a 50% probability of no response. RESULTS: The following mean Cp50 values (95% confidence interval) were obtained: unprovoked righting reflex, 15.9 (15.1-16.6) micrograms/ml; provoked righting reflex, 21.4 (20.2-22.7) micrograms/ml; noise stimuli, 31.3 (29.7-33.0) micrograms/ml; tail clamp and limb movement, 38.3 (36.1-40.4) micrograms/ml; tail pressure and limb movement, 39.2 (37.1-41.3) micrograms/ml; tail pressure and abdominal muscle contraction, 52.5 (50.0- 55) micrograms/ml; tail clamping and abdominal muscle contraction, 56.1 (50.0-56.2) micrograms/ml; corneal reflex, 60.0 (56.6-63.4) micrograms/ml; and limb movement or muscle abdominal contraction response to intubation, 67.7 (59.2-76.1) micrograms/ml. At an EEG-effect of 9.1 and 2.2 waves/s, there was a 50% chance of limb movement response to tail clamping and tracheal intubation, respectively. There was a poor relationship between the plasma thiopental concentration and the percent increase of either heart rate or mean arterial blood pressure after applying either tail pressure or tail clamp stimuli. CONCLUSIONS: A range of nociceptive stimuli and their observed clinical responses can be used to quantitate thiopental anesthetic depth, ranging from light sedation to deep anesthesia (isoelectric EEG and unresponsive to intubation) in the rodent. Clinical response can be mapped to surrogate EEG measures.