Respiratory mechanics and morphometric changes during anesthesia with ketamine in normal rats

Abstract

Ketamine is believed to reduce airway and pulmonary tissue resistance. The aim of the present study was to determine the effects of ketamine on the resistive, elastic and viscoelastic/inhomogeneous mechanical properties of the respiratory system, lungs and chest wall, and to relate the mechanical data to findings from histological lung analysis in normal animals. Fifteen adult male Wistar rats were assigned randomly to two groups: control (N = 7) and ketamine (N = 8). All animals were sedated (diazepam, 5 mg, ip) and anesthetized with pentobarbital sodium (20 mg/kg, ip) or ketamine (30 mg/kg, ip). The rats were paralyzed and ventilated mechanically. Ketamine increased lung viscoelastic/inhomogeneous pressure (26%) compared to the control group. Dynamic and static elastances were similar in both groups, but the difference was greater in the ketamine than in the control group. Lung morphometry demonstrated dilation of alveolar ducts and increased areas of alveolar collapse in the ketamine group. In conclusion, ketamine did not act at the airway level but acted at the lung periphery increasing mechanical inhomogeneities possibly resulting from dilation of distal airways and alveolar collapse.

Impact of respiratory pattern on lung mechanics and interstitial proteoglycans in spontaneously breathing anaesthetized healthy rats

“…Tissue stress increases at high P L , as a consequence of high V T , high R R and . The fact that C L‐dyn was higher, but C L‐stat was lower in P/U compared with that in K/M group is in agreement with the suggestion (Alves‐Neto et al. 2001) that ketamine increases lung resistances.…”

Sleep and Anesthesia

“…Studies on pharmacology of ketamine indicate that it alters airway muscle movement and tranquilizes respiratory activity by reducing the release of acetylcholine in medial pontine reticular formation [38,43,44]. In rat model, ketamine has found to be doing so by increasing viscoelasticity of lung and influencing alveoli [45]. Aforementioned results demonstrate ketamine as a promising sedative for the patients with OSAS because it highly avoids respiratory events during anesthesia [46,47].…”

Comparison of the respiratory effects of commonly utilized general anaesthesia regimes in male Sprague-Dawley rats

“…Elevation of G can most prominently indicate ventilation heterogeneity due to inhomogeneous small airway constriction and/or closure ( Hantos et al, 1992 ; Lutchen et al, 1996 ). As ketamine reportedly increases the collapsibility of the lung periphery, subsequent increases in ventilation heterogeneity may explain substantial increases in G ( Alves-Neto et al, 2001 ). While the protective effects of volatile anaesthetics (including sevoflurane) against cholinergic bronchoconstriction are well-established ( Mitsuhata et al, 1994 ; Habre et al, 1997 ; Habre et al, 2001 ; Balogh et al, 2017 ), we were unable to demonstrate a protective effect of sevoflurane on bronchoconstriction in the present study.…”