Cardiorespiratory effects of different intraabdominal pressures in sheep: An experimental study.

Increased intraabdominal pressure (IAP) during laparoscopy can reduce venous return, but changes in respiratory system mechanics and their effect in left cardiac function are not well documented. This study evaluated the effects of different IAPs on respiratory mechanics and cardiac function in 10 healthy nonpregnant adult Santa Ines ewes randomly submitted to a crossover study using different IAPs: 0 mm Hg (G1), 10 mm Hg (G2), 12 mmHg (G3), and 15 mmHg (G4). Animals were anesthetized and mechanically ventilated (VT  = 15 ml/kg; positive end-expiratory pressure = 3 cmH2 O; FiO2  = 1.0). Pneumoperitoneum was induced by Hasson's trocar cannula. Variables were measured at INITIAL (IAP, 0 mmHg) and FINAL time points for each IAP after 1 h. At FINAL, driving airway pressure (ΔP,RS ), and percentage fraction of dead space (Vd/Vt) were higher in G3 and G4 than G1 (p = 0.002, difference in means [MD] 4.60, 95% CI: 7.91-1.28, and p < 0.001, MD 5.4, 95% CI: 8.7-2.0; p = 0.016, MD -9.5, 95% CI: -17.9 to -1.2; and p = 0.027, MD -8.7, 95% CI: -17.1 to -0.4). The ejection fraction and fractional shortening were lower in G3 (p = 0.039, MD -11.38, 95% CI: -0.07--22.68; p = 0.015, MD -13.05, 95% CI: -1.74--24.36) and G4 (p = 0.039, MD -9.94, 95% CI: -0.07 to -19.80; p = 0.015, MD -11.43, 95%CI: -1.57 to -21.30, respectively) than G2. In G3, the maximum pulmonary flow velocity correlated negatively with ΔP,RS (r = -0.740; p = 0.018), and Vd/Vt correlated positively with ΔP,RS (r = 0.738, p = 0.046). At IAP of 12 and 15 mm Hg impaired respiratory system mechanics, reduced left cardiac function and no change in maximum pulmonary artery flow velocity were detected. Therefore, respiratory mechanics should be monitored as an interplay to reduce left cardiac function.

Evaluation of different doses of propofol in xylazine pre-medicated horses.

OBJECTIVE: To characterize responses to different doses of propofol in horses pre-medicated with xylazine. ANIMALS: Six adult horses (five females and one male). METHODS: Each horse was anaesthetized four times with either ketamine or propofol in random order at 1-week intervals. Horses were pre-medicated with xylazine (1.1 mg kg-1 IV over a minute), and 5 minutes later anaesthesia was induced with either ketamine (2.2 mg kg-1 IV) or propofol (1, 2 and 4 mg kg-1 IV; low, medium and high doses, respectively). Data were collected continuously (electrocardiogram) or after xylazine administration and at 5, 10 and 15 minutes after anaesthetic induction (arterial pressure, respiratory rate, pH, PaO2, PaCO2 and O2 saturation). Anaesthetic induction and recovery were qualitatively and quantitatively assessed. RESULTS: Differences in the quality of anaesthesia were observed; the low dose of propofol resulted in a poorer anaesthetic induction that was insufficient to allow intubation, whereas the high dose produced an excellent quality of induction, free of excitement. Recorded anaesthesia times were similar between propofol at 2 mg kg-1 and ketamine with prolonged and shorter recovery times after the high and low dose of propofol, respectively (p < 0.05; ketamine, 38 +/- 7 minutes; propofol 1 mg kg-1, 29 +/- 4 minutes; propofol 2 mg kg-1, 37 +/- 5 minutes; propofol 4 mg kg-1, 50 +/- 7 minutes). Times to regain sternal and standing position were longest with the highest dose of propofol (32 +/- 5 and 39 +/- 7 minutes, respectively). Both ketamine and propofol reversed bradycardia, sinoatrial, and atrioventricular blocks produced by xylazine. There were no significant alterations in blood pressure but respiratory rate, and PaO2 and O2 saturation were significantly decreased in all groups (p < 0.05). CONCLUSION: The anaesthetic quality produced by the three propofol doses varied; the most desirable effects, which were comparable to those of ketamine, were produced by 2 mg kg-1 propofol.