Anesthetic potency of desflurane in the horse: determination of the minimum alveolar concentration.

OBJECTIVE: To determine the minimum alveolar concentration (MAC) of desflurane (DES) in the horse. STUDY DESIGN: Prospective study. ANIMALS: Six healthy adult horses (three males and three females) weighing 370 +/- 16 kg and aged 9 +/- 2 years old. METHODS: Anesthesia was induced with DES vaporized in oxygen via a face mask connected to a large-animal, semiclosed anesthetic circle system. The horses were endotracheally intubated and positioned in right lateral recumbency. Inspired and end-tidal DES were monitored using a calibrated Ohmeda RGM 5250 multigas analyzer (Ohmeda-BOC, Spain). The MAC of desflurane that prevented gross purposeful movement in response to 60 seconds of noxious electrical stimulation of oral mucous membranes was determined. RESULTS: The time from the start of DES administration to lateral recumbency was 6.1 +/- 0.9 min. The MAC of DES in these horses was 7.6 +/- 0.4%. Time required for the animal to regain sternal recumbency after 98 +/- 4 minutes of anesthesia was 6.6 +/- 0.5 minutes and the time to standing was 14.3 +/- 2.7 minutes. CONCLUSIONS: The MAC of desflurane in these horses was 7.6 +/- 0.4%. DES provided a rapid induction to, and recovery from, anesthesia. CLINICAL RELEVANCE: Desflurane offers the potential for more precise control during anesthesia, and may allow a faster and uneventful recovery. It is important to know the MAC of an inhalant to use it clinically.

Improved distribution of pulmonary flush solution to the tracheobronchial wall in pulmonary transplantation.

This report describes the experimental results obtained with conventional (pulmonary artery, PA) flushing versus retrograde perfusion (via left atrium, LA) using 99mTc-labeled macroaggregated albumin (MAA-99mTc) to ascertain the distribution throughout the tracheobronchial (TB) tree in 10 Large-White pigs. Lung preservation was achieved with 4 degrees C Euro-Collins solution (60 ml/kg) instilled via PA (n = 5) or LA (n = 5). Simultaneously, MAA-99mTc was given using the same respective route and the isotope uptake quantified at different TB levels after heart-lung block harvest and dissection of all tissue adjacent to TB: proximal and distal trachea and right and left main bronchi. Retrograde distribution resulted in a significantly higher 99mTc count compared to the PA route (p < 0.01).

Actions of xylazine in young swine.

OBJECTIVE: To determine sedative, analgesic, and basic cardiovascular effects of xylazine administered to pigs. ANIMALS: 6 two-month-old Landrace x Large White pigs. PROCEDURE: Xylazine was administered i.v. at increasing dosages (1, 2, 4, 8, and 16 mg/kg of body weight) to otherwise unmedicated, conscious pigs, and the aforementioned effects were determined before xylazine administration and 2, 5, 10, and 15 minutes later. Then a higher xylazine dosage was given after the 15-minute measurements were taken. RESULTS: None of the xylazine dosages induced sufficient analgesia to prevent painful response to tail clamping; considerable excitation with vocalization and without appreciable sedative effect was observed at all dosages. At lower dosages, cardiovascular effects were characterized by bradycardia and biphasic blood pressure response; initial hypertension was followed by hypotension. At higher dosages, severe hypotension with moderate bradycardia was followed by marked bradycardia and return to normal baseline values or slight increase in blood pressure. CONCLUSION: Xylazine did not induce adequate sedative or analgesic effects in pigs at any dosage tested; however, cardiovascular effects were considerable. These effects of xylazine differ from those observed in other domestic species.

[Cardiorespiratory and analgesic effects of continuous infusion of propofol in swine as experimental animals]. / Efectos cardiorrespiratorios y analgésicos de la infusión continua de propofol en el cerdo como animal de experimentación.

HYPOTHESIS AND OBJECTIVES: To study the effects of 3 doses of continuous infusion of propofol on heart rate (HR), arterial pressure (AP), cardiac output (CO), pulmonary artery pressure (PAP), pulmonary capillary pressure (PCP), central venous pressure, flow volume, minute volume, arterial gases and analgesic effect. MATERIAL AND METHODS: Eighteen Landrace-Large-White pigs were randomly assigned to 3 groups of 6 based on dose of propofol used. An intravenous dose of 2 mg/kg propofol was followed by the continuous infusion corresponding to each group: group I (GI) received 9 mg/kg/h, group II (GII) received 11 mg/kg/h and group III (GIII) received 13 mg/kg/h, each for a period of 1 hour. Variables were recorded 5, 15, 30, 45 and 60 min after the intravenous induction dose. When the infusion was withdrawn, the time elapsing before recovery of sternal decubitus (SDT) position was recorded for each animal. RESULTS: The following changes from baseline values were statistically significant: AP and PAP increased and PaO2 and MV decreased in GI, with SDT recovery after 27 +/- 4 min; PA increased and FV decreased in GII, while SDT recovery was at 29 +/- 5 min; and diastolic arterial pressure, PCP, CO and HR decreased in GIII. All the pigs in the last group experienced apnea requiring mechanical ventilation and SDT was recovered after 63 +/- 7 min. PCP was significantly higher in GII and GIII than in GI. None of the doses produced an analgesic effect.

Cardiopulmonary and analgesic effects of xylazine, detomidine, medetomidine, and the antagonist atipamezole in isoflurane-anesthetized swine.

The cardiovascular and respiratory effects of three alpha(2)-adrenergic agonists (xylazine 2mg/kg of body weight; detomidine, 40 micrograms/kg; medetomidine, 40 micrograms/kg) and their specific antagonist, atipamezole (200 micrograms/kg) were examined in young, isoflurane-anesthetized (1.3% end-tidal concentration) swine (weight range, 15 to 35 kg). The intravenous administration of all three alpha(2)-agonists caused an initial significant (P < 0.05) but short-lived increase in arterial blood pressure. Atipamezole also increased blood pressure, and this effect persisted throughout the period of observation. All agonists caused a sustained significant bradycardia, whereas atipamezole significantly increased heart rate (30 +/- 7 beats per min). The cardiac index tended to transiently decrease 5 to 10 min after agonist injection (significant only for xylazine at 2 min after injection) from an average pre-injection value of 166 ml/kg per min and did not change in response to atipamezole. None of the drugs significantly modified arterial blood gas (PaO2, PaCO2) or pH values. Xylazine and medetomidine but not detomidine or atipamezole manifested short-lived analgesic properties in response to clamping of the interdigital fold.

Cardiopulmonary and analgesic effects of epidural lidocaine, alfentanil, and xylazine in pigs anesthetized with isoflurane.

To determine cardiopulmonary and analgesic effects of lidocaine, alfentanil, and xylazine in pigs anesthetized with isoflurane, 18 healthy Landrace-Large White pigs were studied (six for each drug). General anesthesia was induced with isoflurane in O2 and maintained with 1% to 1.2% end-tidal ISO, ensuring presence of a pain response before epidural drug administration. Heart rate (HR), arterial blood pressures (AP), cardiac output (CO), pulmonary arterial pressure, pulmonary capillary wedge pressure (PCWP), central venous pressure, respiratory rate (RR), tidal volume (TV), minute volume (MV), arterial blood gas data, core temperature (CT), and analgesic effects (by picking the lumbar area and the abdominal wall) were determined at various times (2, 5, 15, 30, 45, 60, and 90 minutes) after epidural administration of lidocaine (5 mg/kg), alfentanil (5 micrograms/kg), or xylazine (0.2 mg/kg), all diluted in NaCl 0.9% to 0.5 mL/kg. Statistical analysis included two-way analysis of variance for repeated measures and the least significant difference test for determining differences among means. A probability level of P < .05 was used. The following results were statistically significant decreases in systolic AP, HR, TV, RR, MV, CT, pH, PaO2, and TCO2 and increases in PCWP, PaCO2, and HCO3 after LID. After ALF, only CT and HCO3 decreased. Core temperature and TV decreased after XYL. Lidocaine provided 45 to 60 minutes of analgesia. Alfentanil had no analgesic effects, and xylazine provided 90 minutes of analgesia. The authors conclude that xylazine, when injected epidurally, provides suitable analgesia in isoflurane-anesthetized pigs.