Was it cardiogenic or non cardiogenic pulmonary edema? You dont think the pt was fluid overload and The SaO2 dropped very fast? My guess is pt might have a bad mucus plug and developed non cardiogenic pulmonary edema but I could be wrong. Breathing through closed airway can create negative pressure inside the lungs and thus draw fluids inside the lungs and eventually pt develop non cardiogenic pulmonary edema. It's like pulmonary edema secondary to bronchospasm post extubation.
"The doc gave a bunch of orders, including morphine (to calm him down and stop air hunger? the pt was somewhat awake by then), nitro drip (do dilate blood vessels in the lungs?) and Lasix IV push. With Lasix I was puzzled. I read that Lasix is contraindicated to pt with anuria."
They normally give morphine primarily to decrease preload (it can also decrease the afterload) and to alleviate anxiety (decrease O2 demand). IMHO,Nitro drip is to decrease preload by venous dilation and not to dilate blood vessels in the lungs. I agree with you on the Lasix order,it doesn't make sense because the pt is anuric secondary to ESRD. But some nephrologists believe that Lasix causes a rapid venodilatory response (starts before an effect on diuresis). They believe that rapid venodilatory response has significant effect on preload.