title: Comparison of respiratory function during TIVA (romifidine, ketamine, midazolam) and isoflurane anaesthesia in spontaneously breathing ponies Part I: blood gas analysis and cardiorespiratory variables.
abstract: OBJECTIVE
  To compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique.
  
  
  METHODS
  Experimental, cross-over study.
  
  
  METHODS
  Six healthy ponies weighing mean 286 (range 233-388) ± SD 61 kg, age 13 (9-16) ± 3 years.
  
  
  METHODS
  The ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 μg kg(-1) intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg(-1)) and ketamine (2.5 mg kg(-1), then maintained either with inhaled isoflurane (Fe'Iso = 1.1 vol%) (T-ISO) or an IV infusion of romifidine (120 μg kg(-1) hour(-1)), midazolam (0.09 mg kg(-1) hour(-1) IV) and ketamine (3.3 mg kg(-1) hour(-1)) (T-TIVA). Ponies were placed in lateral recumbency. Breathing was spontaneous and Fi'O(2) 60%. After an instrumentation/stabilisation period of 30 minutes, arterial and mixed venous blood samples were taken simultaneously every 10 minutes for 60 minutes and analysed immediately. Oxygen extraction ratio (O(2)ER) and venous admixture were calculated. Tidal volume (TV), minute volume (MV), respiratory rate (f(R)), packed cell volume (PCV), arterial blood pressure and heart rate (HR) were measured and recorded. Data were analysed with mixed model anova (α = 0.05). Treatments were compared overall and at two selected time points (T30 and T60) using Bonferroni correction.
  
  
  RESULTS
  Arterial and mixed venous partial pressures of O(2) and CO(2), and TV were significantly lower and MV and f(R) were higher in T-TIVA compared to T-ISO. Venous admixture did not differ between treatments. O(2) R was significantly higher in T-TIVA. Mean arterial pressure was higher and HR was lower in T-TIVA compared to T-ISO.
  
  
  CONCLUSIONS
  Whilst arterial CO(2) was within an acceptable range during both protocols, the impairment of oxygenation was more pronounced with the T-TIVA evidenced by lower arterial and venous oxygen partial pressures.
authors.affiliation: Department of Surgery and Anaesthesia of Domestic Animals, Faculty of Veterinary Medicine, University of Ghent, Merelbeke, Belgium.
authors.forename: Barbara
authors.initials: B
authors.lastname: Steblaj
authors.forename: Stijn
authors.initials: S
authors.lastname: Schauvliege
authors.forename: Kiriaki
authors.initials: K
authors.lastname: Pavlidou
authors.forename: Frank
authors.initials: F
authors.lastname: Gasthuys
authors.forename: Ioannis
authors.initials: I
authors.lastname: Savvas
authors.forename: Luc
authors.initials: L
authors.lastname: Duchateau
authors.forename: Lidia
authors.initials: L
authors.lastname: Kowalczyk
authors.forename: Lidia
authors.initials: L
authors.lastname: Kowalczk
authors.forename: Yves
authors.initials: Y
authors.lastname: Moens
mesh_terms: D000769:Anesthesia, Inhalation / Q000379:methods / Q000662:veterinary*; D000771:Anesthesia, Intravenous / Q000379:methods / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D018592:Cross-Over Studies; D003964:Diaphragm / Q000187:drug effects; D005260:Female; D006736:Horses; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology; D007530:Isoflurane / Q000494:pharmacology; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008874:Midazolam / Q000008:administration & dosage / Q000494:pharmacology; D012143:Respiratory Physiological Phenomena / Q000187:drug effects*; D056152:Respiratory Rate / Q000187:drug effects
chemical_list: D018685:Anesthetics, Inhalation; D007093:Imidazoles; D007649:Ketamine; C076257:romifidine; D007530:Isoflurane; D008874:Midazolam
keywords: TIVA; blood gases; isoflurane; oxygen extraction ratio; ponies; pulmonary function