54 VETERINARY SURGICAL OPERATIONS 



SEQUELiE AND ACCIDENTS.— Pneumothorax is by 



far the most serious accident of thoracocentesis. It is caused 

 by permitting the suction of air into the cavity through the 

 canula, after the major part of the fluid has been abstracted. 

 During the inspiration, as the lungs inflate with air, the fluid 

 around them is forced up to the level of the canula and a lim- 

 ited quantity will flow out, but as the thorax contracts for the 

 exhalation a certain amount of air will be drawn in, unless 

 preventive measures are taken. (See fourth step.) Al- 

 though but little air enters at each respiratory act, a sufficient 

 amount will find its way into the pleural sacs during the en- 

 tire last part of the aspiration to cause a pronounced distress 

 of the breathing. Normally the pleural sacs should each be a 

 vacuum ; in the horse they constitute a single vacuum, being 

 connected to each other through a fenestrated membrane in 

 the posterior mediastinum. When air is admitted into this 

 vacant space an important part of the mechanism of respira- • 

 tion is destroyed and a distressing dyspnoea immediately 

 supervenes and continues for some hours. This dyspnoea, 

 added to an already serious embarrassment of respiratory 

 function, at once deprives the operation of any curative value. 

 In fact, the patient, which now needs vigor more than ever, 

 is stricken with a demoralizing distress that leaves little 

 chance for recovery. The operation was, then, more harmful 

 than beneficial. On the other hand if no air has been permit- 

 ted to enter, the operation is followed by an immediate im- 

 provement of the labored breathing. The deep, heavy, 

 pumping respirations become calm and almost normal as the 

 fluid gradually flows out. 



Treatment. — Pneumothorax is easily prevented by at- 

 taching a rubber tube to the canula as prescribed above, but 

 is incurable except through nature's own forces, i.e., by re- 

 sorption of the air by the pleura. 



Shock.-^Old cases of hydrothorax, where the thorax is 

 full, where the respirations have gradually become more and 

 more labored, without having made a corresponding impres- 

 sion on the general health, are very prone to succumb to 

 shock after the fluid is removed. The acute cases and the 

 sub-acute cases are less susceptible to this sequel. It is the 

 chronic one that is actually dangerous from this standpoint. 

 Dropsy, in the absence of any existing or pre-existing inflam- 

 mation of the pleura, is the more dangerous. The danger of 

 shock is also augmented by rapid aspiration. If the thorax 

 were lanced and all of the contents suddenly evacuated, shock 

 would be the inevitable result in almost every case. A large 



