Case Presentation by Dr. Arun Rajasekhar, MD
CHIEF COMPLAINT: Right leg injury.
HPI: A 43-year-old man stated that another person landed on his right leg. He felt and heard a snap and then he immediately experienced severe right knee pain. This happened within 1 hour prior to admission. He was brought here by EMS. He complains of severe right knee pain. He has not done anything for his symptoms.
PAST MEDICAL HISTORY: Denies diabetes, seizures, hypertension.
VITAL SIGNS: Blood pressure 184/86, pulse rate 93, respirations 20, temperature 36.3.
GENERAL: This is a well-developed, well-nourished 43-year-old man, awake, alert but uncomfortable due to pain.
MUSCULOSKELETAL: Normal muscle bulk and tone. He has a deformity of the right knee. He has normal dorsal pedis and posterior tibial pulses. He has good popliteal pulse. He has a deformity of the right knee.
1) The above xray shows anterior displacement of the tibia on the femur. Which ligament is most likely to have been completely torn?
2) Which of the following is NOT a hard sign of vascular injury associated with knee dislocations
a) absence of pulse
b) expanding hematoma
c) paresthesias in leg
d) bruit over site of wound
3) Patient required conscious sedation for reduction of his knee. Decision was made to use ketamine and propofol. Immediately after infusion, Pt starts gasping for air and immediately becomes tachycardic and tachypneic. He has equal breath sounds. Trachea is midline. What is your working diagnosis and which of the two agents is most likely responsible? What should be done?
a) Acute tension pneumothorax due to propofol administration. Needle decompression
b) Acute laryngospasm secondary to ketamine administration. Paralyze patient and intubate immediately
c) Acute laryngospasm secondary to propofol. Attempt to bag patient through laryngospasm
d) Acute laryngospasm secondary to ketamine. Perform cricthyrotomy.
Answers & Discussion:
1) A & D
1) PCL and ACL are both acceptable answers. The patient has an anterior knee dislocation. This is the most common type of knee dislocation. It is caused by hyperextension of the knee joint. Often both he PCL and MCL will be torn. With all knee dislocations it is important to have a high index of suspicion for popliteal artery injury. Initial assessment of the leg should include palpation of the dorsalis pedis and popliteal pulses. You can also perform ABIs to assess distal blood flow. It is important to note that PT and DP pulses will be normal in 5-15% of popliteal artery injuries. CT angiography can be used to detect arterial injury.
2) Parasthesias is the answer. Hard signs of vascular injury include active hemorrhage, expanding hematoma, bruit over wound, absent distal pulses, extremity ischemia (cold to touch, paralysis, pallor). In the setting of penetrating trauma, hard vascular injuries are 100% predictive of arterial injury and patient should be taken directly to operating room for surgical exploration. In the setting of blunt trauma, hard signs are less reliable and false positives are common. Repeat physical exam should be performed after resuscitation and reduction or orthopedic injury. If hard sign persists, get CT scan. Diagnosis of popliteal artery injury is time sensitive. Amputation rate increases the long repair is delayed. Rate of amputation is 90% eight hours out from the time of injury.
3) Patient is experiencing acute laryngospasm secondary to ketamine. This is a rare but known side effect of ketamine. It has been primarily reported in the pediatric literature. Patient’s will desaturate and decompensate quickly. In my scenario, the patient had a very visible reaction to the medication but there have been case reports of patients desaturating without showing a obvious signs of distress because of the sedative effect of the ketamine and the propofol. If a patient begins to desaturate and you are uncertain as to the exact etiology, the first and simplest thing to do is a jaw thrust maneuver to see if that relieves the hypoxia. You can also bag mask the patient. However, neither of these maneuvers will relieve laryngospasm. This patient needs neuromuscular blockade to relieve the laryngospasm and once the patient is paralyzed you should immediately proceed to intubation. Some sources stated that you could bag mask the patient until the paralytic wears off but I think if you are going to paralyze a patient, then you should give them a definitive air way.