Читать книгу Manual of Equine Anesthesia and Analgesia - Группа авторов - Страница 338

 Will increase cerebral blood flow and intracranial volume through vasodilation.

 This could be detrimental in animals with existing increased ICP.

 Mechanical ventilation is required during anesthesia to ensure PaCO2 values are kept between 35 and 40 mmHg (normal PaCO2 in adult horse is approximately 40 mmHg) to reduce the risk of increasing ICP.Table 6.1 Reported effects of drugs on neurophysiology of the brain.DrugCerebral blood flowCerebral metabolic O2 requirementDirect cerebral vasodilationSeizure potentialXylazine−?VasoconstrictionHigh dose: AnticonvulsantLow dose: ProconvulsantDetomidine? probably? probably? probably vasoconstriction?Dexmedetomidine−−VasoconstrictionHigh dose: AnticonvulsantLow dose: ProconvulsantAcepromazine−NC?Possible NCKetamineNC with IPPV++ with hypercapnia+With hypercapniaProconvulsant or anticonvulsantThiopental−−NoAnticonvulsantKetamine/diazepam++??Propofol−−NoAnticonvulsantAlfaxalone(with alphadolone in Cremaphor EL)−−Probably noAnticonvulsantMidazolam−−NoAnticonvulsantGuaifenesin???Depresses EEGHalothane+++−YesNo effectIsoflurane+ or NC with IPPV−YesNo effectSevoflurane+ or NC with IPPV−YesNo effectNC = No change + = Increase − = Decrease.

  Excessive ventilation to below this PaCO2 range will cause excessive vasoconstriction and lead to poor perfusion of some parts of the brain.

 End‐tidal capnography often under‐estimates PaCO2; therefore, arterial blood gas analysis should be used periodically to check the accuracy of the capnogram.