RESEARCH PAPER Cardiopulmonary effects of thoracoscopy in anesthetized normal dogs SimonT Kudnig BVSc, MVS, MS, MACVSc, Eric Monnet DVM, PhD, DiplomateACVS, Diplomate ECVS, Miriam Riquelme DVM, James S Gaynor DVM, MS, DiplomateACVA, Denise Corliss CVT & Mowafak D Salman BVMS, PhD DepartmentofClinicalSciences,ColoradoStateUniversity,FortCollins,CO,USA Correspondence: EricMonnet,DepartmentofClinicalSciences,ColoradoStateUniversity,300W.DrakeRoad,FortCollins,CO80523,USA. E-mail:Eric.Monnet@colostate.edu Abstract Objective Toevaluatethee¡ectofanopen-chestcon- ditiononoxygendeliveryinanesthetizeddogs. Study design Prospective, controlled experimental study. Animals Eight clinically normal adult Walker Hounddogsweighing25.6^29.2kg. Methods Eight anesthetized dogs underwent an open-chestoperationafterthe insertionofthoraco- scopy cannulae in the lateral chest walls . A Swan Ganz catheter was used to both measure hemody- namic parameters and obtain mixed venous blood samplesforbloodgasanalysis.Adorsalpedalcathe- ter was placed to both measure arterial blood pres- sureandobtainbloodsamplesforbloodgasanalysis. Oxygen delivery index and oxygen extraction ratio were calculated. A randomized block ANOVA for repeatedmeasureswasusedtoevaluatethee¡ectof the treatment on hemodynamic and pulmonary parameters. Results Creation of an open chest did not signi¢- cantly a¡ect oxygen delivery index (DO 2 I; p  0.545). It induced a signi¢cant decrease in arterial oxygenpartialpressure(PaO 2 ; p  0.018)andarter- ial oxygen content (CaO 2 ; p  0.025). It induced a signi¢cant increase in shunt fraction ( p  0.023), physiologic dead space ( p  0.015), and alveolar- arterial oxygen di¡erence ( p  0.019). Arterial par- tial pressure of carbon dioxide (PaCO 2 ; p  0.766) and arterial hemoglobin oxygen saturation (SaO 2 ; p  0.178) were not signi¢cantlya¡ected. Diastolic (DPAP; p  0.050) and mean (MPAP; p  0.033) pul- monary arterial pressures were signi¢cantly increasedbyopeningthechest.Otherhemodynamic parameterswerenotsigni¢cantlya¡ected. Conclusions Openingthethoraciccavityisnotdet- rimentaltohemodynamicfunctionandoxygendeliv- ery in normal dogs, although impaired gas exchangedoesoccur. Clinical relevance Close monitoring of patients is recommended during open-chest thoracoscopy as adverse e¡ects on gas exchange can contribute to hypoxemia. Keywords cardiopulmonary, hemodynamic, oxygen delivery,shuntfraction,thoracoscopy. Introduction Patients undergoing thoracic surgeryareat risk for hypoxemia and hemoglobin (Hb) desaturation.The combined e¡ect of anesthetic agents (Rehder & Sessler1973;Hedenstiernaetal.1985),muscleparaly- sis and mechanical ventilation (Froese & Bryan 1974), lateralrecumbency (Craigetal.1962;Rehder et al.1972;Werner et al.1984), and atelectasis from openingthe chest (Yoshida & Takaori1991; de Gray et al.1997) can result in increased shunt fraction (Qç s /Qç t ), ventilation^perfusion (Vç /Qç ) mismatch, and arterial hypoxemia (Yoshida & Takaori 1991; de Grayet al.1997).The relationship between inspired VeterinaryAnaesthesiaand Analgesia, 2004, 31 , 121^128 121