‘House, M.D.’ season finale

“House, M.D.”, season finale

Fox, Monday, May 17, 8 p.m.

Episode: “Help Me”

The premise: A crane collapses onto a building in Trenton, N.J. Dr. Lisa Cuddy (Lisa Edelstein) and Dr. Gregory House ( Hugh Laurie) arrive with a team of doctors to help the fire department and emergency rescue workers treat the wounded. House finds Hanna, 25, trapped under the collapsed concrete. Her leg is stuck and the team is unable to free it. Cuddy suggests immediate amputation to treat the “compartment syndrome” she believes has developed from the injury, before it kills Hanna’s tissue and causes an increase in potassium levels, possibly leading to cardiac arrest. At first, House refuses to amputate. The rescue team begins to lift the concrete off Hanna and frees her leg, but there is an explosion and Hanna is injured further. Hanna begins to breathe rapidly because her lung has collapsed, and House puts a needle followed by a tube into her chest cavity to create a negative pressure and reinflate the lung. House now decides to amputate Hanna’s leg because he doesn’t want her to have to live with a crippled painful leg the way he does. He amputates with a small electrical saw, without anesthesia, as Hanna screams in pain. In the ambulance, Hanna’s blood pressure drops and she is again unable to breathe. House at first thinks there is a blood clot in the lung and he tries to break it up by injecting a clot dissolver, but Hanna continues to worsen. House realizes she must have a “fat embolism” (fat broken off from the wound that has traveled to the lungs) and there is nothing he can do. Hanna dies.

The medical questions: What is “compartment syndrome,” and is it cause for immediate amputation? Does it lead to a life-threateningly low potassium level? Can a lung be reinflated successfully at a trauma scene with a needle and tube to create negative pressure? Should a clot-dissolver be given, on a hunch, outside the hospital to a trauma patient? Is a fat embolism a common complication of being trapped and partly crushed? Is there a treatment?

The reality: A compartment syndrome results from the compression of muscle inside a closed space, says Dr. D.J. Green, assistant professor of trauma surgery at the USC Medical Center Naval Trauma Training Center. The muscle swells, Green says, compressing the blood vessels and nerves, causing tissue death. The fact that Hanna’s limb is trapped by the collapsed building doesn’t automatically mean she will have a compartment syndrome, adds Dr. Donald A. Wiss, director of orthopedic trauma at Cedars-Sinai Medical Center. If she did, cutting the connective tissue that holds the muscle together (a fasciotomy) to relieve the pressure would generally be the procedure of choice. An amputation might be indicated if the limb remained trapped or if the patient was unstable, Wiss says. But it would never be done without anesthesia, he adds; morphine would be the minimum used.

A crush injury can lead to a release of potassium from the tissues into the blood, Green says, especially after the leg is freed and the dying tissue regains its blood supply. But Wiss points out that the excess potassium would rarely be life-threatening in an otherwise healthy 25-year-old woman with working kidneys that are capable of removing excess potassium.

An early amputation is not generally done, Wiss adds, because it is hard to predict just how functional an injured leg will be later on.

House’s treatment of the collapsed lung — inserting a needle then a tube to draw air or fluid out of the chest cavity, thus allowing the lung to reinflate — is appropriate. But without a suction device to continue to maintain the negative pressure, the lung would only partly re-inflate, says Dr. Edward Newton, chairman of emergency medicine at USC’s Keck School of Medicine.

Newton believes it is inappropriate to use a clot-dissolving drug on a hunch in a major trauma patient with a crushed leg, collapsed lung and probably other internal injuries. The drug could lead to uncontrolled hemorrhage and death. Plus, Wiss says, a trauma surgeon would be much more suspicious of a fat embolism than a blood clot to begin with from a fractured or crushed leg like Hanna’s.

There is no specific treatment for a fat embolism, all three experts say — just supportive care. And most patients survive.

Finally, Newton points out that the fire department captain on the scene would never let physicians into the rubble in the first place unless he was certain it was safe.

Siegel is associate professor of medicine at NYU Langone Medical Center.

marc@doctorsiegel.com