The Recovery Profile of Reduced Diaphragmatic Contractility Induced by Propofol in Dogs

Abstract

Propofol decreases contractility of the diaphragm, but no data are available for its effects on recovery. We studied the recovery profile of reduced diaphragmatic contractility induced by propofol in dogs. Animals were divided into 4 groups of 7 each. Group I, without fatigue, received only maintenance fluid; Group II, without fatigue, was infused with propofol; Group III, with fatigue, received no study drug; Group IV, with fatigue, was infused propofol. Propofol at an anesthetic dose (0.1 mg/kg initial dose plus 6.0 mg x kg(-1) x h(-1)) was administered for 60 min. In Groups III and IV, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at 20-Hz for 30 min. We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). In group II, Pdi at low-frequency (20-Hz) stimulation decreased to less than baseline (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. At 10 min after the end of propofol administration, Pdi at 20-Hz stimulation returned to baseline. When fatigue was established, in Groups III and IV, Pdi at 20-Hz stimulation decreased to less than baseline (P < 0.05), whereas Pdi at 100-Hz stimulation did not change. After administering propofol in Group IV, Pdi at 20-Hz stimulation decreased from fatigued values (P < 0.05). At 20 min after the end of propofol administration, Pdi at 20-Hz stimulation returned to fatigued values. We conclude that reduced contractility in nonfatigued and fatigued canine diaphragm induced by propofol recovers within 20 min after the cessation of administration.

Efeitos de diferentes frações inspiradas de oxigênio sobre a dinâmica respiratória em cães submetidos à infusão contínua de propofol e mantidos em ventilação espontânea

“…Segundo Jefferies 2 e Hedenstierna et al 5 , durante a anestesia geral, a atelectasia pulmonar pode ser encontrada em animais respirando 80 a 100% de oxigênio 1 , sugerindo, portanto, que os resultados obtidos nesses grupos foram oriundos de áreas de colapso pulmonar, comprometendo desta forma, a troca gasosa nesses cães. Ademais, Fujii et al 11,12 afirmaram que o propofol, em cães, causa diminuição na contratilidade do diafragma, e se esta musculatura não estiver rígida o suficiente entre as duas cavidades, a pressão abdominal será transmitida para o interior da cavidade torácica, aumentando, em particular, a pressão pleural nas regiões pulmonares, resultando em atelectasia. 10 Neste estudo, acredita-se que essa característica do anestésico empregado é mais um fator contribuinte para a formação de áreas de atelectasia, juntamente com o emprego de altas FiO 2 .…”

“…1,10 Fujii et al 11 afirmaram que o propofol, em doses sub-hipnóticas e anestésicas, causa diminuição na contratilidade do diafragma em cães, e que esta é recuperada 20 minutos após o final da administração deste fármaco. 12 Além disso, o propofol causa depressão no sistema respiratório de forma semelhante à verificada com o tiopental. Após sua administração pode ocorrer apnéia transitória, redução do volume minuto (VM) e da freqüência respiratória (f), com aumento da pressão parcial arterial de dióxido de carbono (PaCO 2 ) e diminuição da pressão parcial arterial de oxigênio (PaO 2 ), sendo a incidência destes efeitos diretamente proporcional à dose administrada.…”

Dopamine alleviation of diaphragm contractile dysfunction and reduction of deoxyribonucleic acid damage in rats

“…7 In vivo experiments have used a decrease in transdiaphragmatic pressure or electromyographic activity to quantify diaphragm fatigue. 8,9 However, in the intensive care unit, the assessment of diaphragm strength is difficult because there is no method to direct measure diaphragm contractility. 2 In this study, we have a direct measure of diaphragm shortening (contractility) that is possible in the animal model.…”

Two levels of the inspired oxygen fraction in propofol-anesthetized dogs with high intracranial pressure: cardiopulmonary function

“…However, we believe that the difference observed between G100 and G60 (Table 1) was not resultant of FRC decrease, because all dogs were positioned in left lateral recumbency and the propofol rate was the same for the both groups, considering that this drug reduces the contractility of the canine diaphragm (Fujii et al, 2004). Nevertheless, we suggest that V/Q was impaired in G100 when compared to G60.…”