Haemodynamic changes during halothane, sevoflurane and desflurane anaesthesia in dogs before and after the induction of severe heart failure:

Fluid heating system (SAF®): effects on clinical and biochemistry parameters in dogs submitted to inhalatory anesthesia

PURPOSE: To evaluate and describe immediate effects of the infusion of saline solution heated by SAF® in bitches submitted to halothane anesthesia. METHODS: Thirteen bitches were employed and submitted to elective ovariohysterectomy in acclimatized operating room at 22ºC, allocated in two groups: GI, which received non-heated fluid and GII, which received fluid heated at 37ºC by SAF®. The following parameters were evaluated in 30-minutes intervals (M0, M30, M60 and M90): rectal and cutaneous temperatures (TR and TC), cardiac and respiratory frequencies (HR and ƒ), mean arterial blood pressure (MAP), serum concentration of urea, creatinin, serum activities of alanin aminotranspherasis (ALT), alkaline phosphatasis (ALP) and also hypnosis parameters. RESULTS: There were no significant alterations on clinical and biochemical, but there was group effect on mean arterial blood pressure, urea, ALT, ALP and hypnosis parameters. CONCLUSION: The isolated use of Fluid Heating System (SAF®) was not enough to avoid hypothermia or lead to significant clinical and biochemical alterations in bitches submitted to halothane anesthesia.

The haemodynamic and catecholamine response to xenon/remifentanil anaesthesia in Beagle dogs

The noble gas xenon seems to have minimal cardiovascular side-effects and so may be an ideal anaesthetic agent when investigating cardiovascular physiology. In comparison with standard modern anaesthetics, we investigated the haemodynamic and hormonal effects of xenon in Beagle dogs. After a 30 min baseline period, anaesthesia was induced with propofol and maintained with either (1) 1.2% isoflurane/70% nitrous oxide (N2O), (2) 0.8% isoflurane/0.5 µg/kg/min remifentanil or (3) 63% xenon/0.5 µg/kg/min remifentanil ( n = 6 per group). Haemodynamics were recorded and blood samples taken before and 60 min after induction. Mean arterial blood pressure (MAP) was higher in conscious dogs than during isoflurane/N2O (86 ± 2 vs. 65 ± 2 mmHg, mean ± SEM) and isoflurane/remifentanil anaesthesia (95 ± 2 vs. 67 ± 3 mmHg), whereas MAP did not decrease significantly in response to xenon/remifentanil anaesthesia (96 ± 4 vs. 85 ± 6 mmHg). Bradycardia was present during isoflurane/remifentanil (54 ± 2/min) and xenon/remifentanil (40 ± 3/min), but not during isoflurane/N2O anaesthesia (98 ± 3/min, P < 0.05). Xenon/remifentanil anaesthesia induced the highest reduction in cardiac output (CO) (–61%), and the highest increase in systemic vascular resistance (+120%) among all treatment groups ( P < 0.05). A simultaneous increase in endogenous adrenaline and noradrenaline concentrations could only be observed in the xenon/remifentanil group, whereas angiotensin II and vasopressin concentrations increased in all groups. In conclusion, xenon/remifentanil anaesthesia maintains MAP but reduces heart rate and CO and is associated with a considerable stimulation of vasopressor hormones in Beagle dogs. Therefore, xenon/remifentanil exerts a new quality of adverse haemodynamic effects different from volatile anaesthetics and may not perform better during studies of cardiovascular physiology.

Minimum alveolar concentration of halogenated volatile anaesthetics in left ventricular hypertrophy and congestive heart failure in rats

BACKGROUND

Although many physiological and pathological conditions affect minimal alveolar concentration (MAC), there are no reliable data on the MAC for halogenated anaesthetics during left ventricular hypertrophy (LVH) and congestive heart failure (CHF). The aim of this experimental study was to determine the MAC values of halothane, isoflurane, and sevoflurane in rats, at early and later stages of cardiomyopathic hypertrophy.

METHODS

LVH was induced by ascending aortic stenosis in 3-4-week-old rats. LVH and CHF in each animal were assessed weekly by echocardiography. MAC of halothane, isoflurane, and sevoflurane was determined using the tail-clamp technique in spontaneously breathing rats from each group. Response vs no-response data were analysed using logistic regression analysis. Data are medians (95% confidence interval).

RESULTS

The MAC of halothane [1.30% (1.26-1.34)], isoflurane [1.52% (1.48-1.57)], and sevoflurane [2.93% (2.78-3.07)] in rats with LVH was not different from sham-operated rats [respectively, 1.23% (1.20-1.26), 1.52% (1.47-1.56), and 2.90% (2.79-3.00)]. Conversely, the MAC of halothane [1.44 (1.39-1.50)] and isoflurane [1.74 (1.69-1.78)], but not sevoflurane [2.99 (2.93-3.06)], was significantly increased in rats with CHF.

CONCLUSIONS

MAC values for halothane, isoflurane, and sevoflurane were unchanged in rats with pressure-induced overload LVH. Conversely, the MAC for halothane and isoflurane, but not sevoflurane, was significantly increased in rats with CHF.