Influence of recumbency upon pulmonary shunt occurrence in inhalation-anaesthetized sheep

Author(s)

Roberto Romano do Prado Filho

• Document type: Master's Dissertation
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT)
• Defense date: 2021-04-28

Examining board members

Adriano Bonfim Carregaro; Eduardo Raposo Monteiro; Paulo Sergio Patto dos Santos

• Advisor: Adriano Bonfim Carregaro

Abstract

The present study analyzed the impact of different decubitus in sheep during inhalation anaesthesia, prioritizing ventilatory changes and pulmonary shunt. For this purpose, 7 female sheep were submitted to sevoflurane inhalation anesthesia, maintained on pressure-controlled ventilation (12 cmH2O), respiratory rate (ƒ) fixed on 10 mpm and a zero end-expiratory pressure (ZEEP). Immediately after anesthetic induction, the animals undergone three different treatments, namely: dorsal, left lateral or right lateral recumbency positions. Treatments order were determined randomly, being all animals subjected to all treatments, with duration of 120 minutes each. Interval between procedures was 48 hours. Arterial and central venous blood samples were collected for blood gas and electrolytes analysis immediately after anesthetic induction, after 60 minutes of induction and after 120 minutes of induction. Obtained values were used to calculate the pulmonary shunt fraction (V/Q), arterial oxygen content (CaO2), central venous oxygen content (CcvO2), pulmonary end-capillary oxygen content (Cc\'O2), alveolar oxygen partial pressure (PAO2), minute volume (VM), tidal volume (VT), alveolar-arterial oxygen gradient [P(A-a)O2] and arterial-end-tidal carbon dioxide gradient [(a-ET)CO2]. Results showed that V/Q greatly decreased from 0 to 120 min in all the groups (dorsal: 69.3% to 27.3%; left lateral: 59.1% to 25.0%; right lateral: 67.2% to 32.4%). CaO2, CcvO2, CcO2, PAO2, P(A-a)O2 values were significantly higher in all the groups, from 60 min after induction, and maintaining them further (p <0.05). Higher CaO2 levels in animals from the left lateral recumbency group were observed at 0 min (9.9±1.43 mL.dL-1) compared to the dorsal recumbency group (8.9±1.4 mL.dL-1) (p=0.0177). No differences between treatments were observed for CcvO2, CcO2 and PAO2. The left recumbency group showed lower P(A-a)O2 values at 0 min (p=0.0117) and 60 min compared to the right one (p=0.0282). No differences were found in VT and VM in all treatments and between time points, and the same was observed for P(a-ET)CO2 values. FiO2, HR and FE\'Sevo showed no statistical difference at different time points. PaO2 showed higher values at 60 and 120 min for all the groups, when compared to the 0 minute (p<0.001). PaCO2 followed the same pattern, but only for the right and left recumbency groups. Conversely, the dorsal recumbency group showed stable PaCO2 throughout the anaesthesia period, thus, being different from the others at 120 min. In conclusion, recumbency has little influence on pulmonary shunt occurrence. (AU)

• FAPESP's process: 18/15165-9 - Influence of recumbency upon the incidence of pulmonary shunt in inhalation-anaesthetized sheep
• Grantee: Roberto Romano do Prado Filho
• Support Opportunities: Scholarships in Brazil - Master