Effects of hypercapnic hyperpnea on recovery from isoflurane or sevoflurane anesthesia in horses.

The research paper explores whether using an increased amount of carbon dioxide (hypercapnic hyperpnea) during the recovery phase of anesthetic can reduce the recovery time in horses. The paper also compares the recovery times between two commonly used anesthetics, isoflurane and sevoflurane.

Methodology

• The research used a randomized crossover study design involving eight healthy adult horses.
• Two anesthetic agents, isoflurane and sevoflurane, were used in the experiment. Each horse was administered a constant 1.2 times MAC (minimum alveolar concentration) of either isoflurane or sevoflurane for two hours.
• After this, the horses were disconnected from the anesthetic circuit and were given either no CO2, 5% CO2, or 10% CO2 mixed with oxygen.
• Data was collected on anesthetic washout kinetics by measuring end-tidal gas samples. Arterial and venous blood samples were also drawn to measure respiratory gas partial pressures.
• All horses recovered unaided in padded stalls. The recovery phase was videotaped and reviewed by blinded observers.

Results

• The findings showed that sevoflurane, compared to isoflurane, caused greater hypoventilation which was associated with a longer recovery time.
• The introduction of carbon dioxide significantly reduced anesthetic recovery time compared to providing only oxygen post-anesthesia.
• This reduction in recovery time was achieved without a significant increase in the partial pressure of carbon dioxide in the arterial blood (PaCO2).
• The pharmacokinetic parameters in horses recovering from isoflurane with CO2 were almost indistinguishable from those recovering from sevoflurane without CO2.
• Recovery quality was not affected by either the type of anesthetic agent used or the insufflation treatment.

Conclusions

• Hypercapnic hyperpnea (increased levels of carbon dioxide) can reduce the time to recover from anesthesia without influencing the quality of recovery.
• While sevoflurane has a lower blood gas solubility, which should theoretically make recovery time shorter, this advantage is offset by the greater degree of hypoventilation it causes in horses in comparison to isoflurane.