Case of the Week COW #21

Resident: Yenisleidy Paez Perez 

CC:“I”m bringing in my son. He has been having tooth pain since last night, and I gave him Tylenol but then he seemed to pass out and had white stuff at the mouth and his face and hands look blue”

HPI: 5-year-old male presents to ED brought by his mother today after she noticed his mouth, legs, arms, and legs started turning blue. Patient was brought immediately after mother noticed the symptoms. Prior to arrival, patient was given Tylenol which mom bought a local store for a toothache he’s been having for the past few days. Patient has appointment with the dentist tomorrow. Patient’s mother denies any change in behavior, HA, dizziness, or syncope episode. Denies fever, chills, recent illnesses, nausea, vomiting, diarrhea, generalized weakness, or lethargy, abdominal pain, limitations in his activities, difficulty breathing, cough or URI symptoms. Upon arrival, patient is hypoxic, saturating 77% on room air. Despite this, pt denies SOB or Chest pain.

Physical Exam:
T: 35.6 °C (Tympanic) HR: 126 (Monitored) RR: 14 BP: 102/73 SpO2: 82% (on Non-rebreathing Mask) WT: 18.60 kg

Constitutional: Awake, alert, comfortable but irritable, crying but consolable by the mother. Head: Normocephalic, atraumatic


ENT: External ears are unremarkable. B/L external auditory canals are normal and clear, no cerumen impaction, non-erythematous. B/L TMs are normal, nonerythematous, no bulging or dullness or effusion. Posterior pharynx is grossly normal, non-erythematous, no tonsilar enlargement, or exudates. Multiple dental cavities with mild tenderness on palpation of right lower jaw.

Neck: Supple, full range of motion, no mass Chest: Normal appearance and motion, no deformity or crepitus.

Cardiovascular: Tachycardia. Rhythm is regular. Normal S1 and S2, No gallops, murmurs, or rubs., symmetric pulses bilaterally

Respiratory: Normal chest rise and fall, no respiratory distress or stridor despite hypoxia and cyanosis, equal breath sounds bilaterally, clear to auscultation bilaterally, no wheezing, rales or rhonchi. No stridor.

Abdomen/GI: Soft, non-tender, no rebound tenderness or guarding, nondistended, no organomegaly

Neuro: Alert and oriented, Mentation is appropriate for age, moves all fours, good tone. GCS 15. 5/5 strength in all extremities. Sensory intact

MS/extremity: ROM intact in all extremities. Pulses equal. Neurovascularly intact.

Skin: Acrocyanosis and periorbital cyanosis noted, no rashes, no erythema,

Laboratory Data:
Blood work was drawn and the blood was noticed to be chocolate brown

CMP: Na: 137    K+: 3.9    Cl: 104    CO: 21    BUN: 12    Cr: 48    Glucose: 116 Alk Phos: 279    AST: 25    ALT: 9

CBC: WBC: 8.4    Hg: 12.7    Hct: 38.1    Platelet: 312    PT: 13. 7    INR: 1    PTT: 32.6

D-dimer: 0.43      Troponin: < 0.010      VBG & MetHb: Pending!


Pertinent Images/EKG:
EKG: Sinus Tachycardia at 126 bpms. Normal PR- Interval and QRS- interval. No T waves changes.
Chest X ray: Normal chest X-ray, NO cardiomegaly, NO increased interstitial lung markings , no consolidation, no PTX.

Working Diagnosis at time of Disposition: Methemoglobinemia , CO Poisoning  and Anemia


VGB (Mixed Venous Gas) pH: 7.39   pCO2: 36   pO2: 265   HCO3: 21.8   Lactate 2.6   COHb: 0.2   MetHb: 30

5-year-old male presented to the ED with hypoxia, saturating 77% on room air. His saturations went up only to 85% – 87% while on a non-rebreather mask.. No evidence of anaphylaxis, no wheezing, rales or decreased breath sounds on exam. No rashes, no vomiting or abdominal pain. Chest x-ray did not reveal cardiomegaly or pulmonary infiltrate or pneumothorax. Blood work was drawn as well as Met hemoglobin levels, VBG and carboxyhemoglobin levels were obtained. Met hemoglobin level return at greater than 30%.

This is a case of methemoglobinemia, which was treated with Methylene blue (2mK/kg over 15 minutes). After it was administered, patient’s saturation increased to 97% while on non-rebreather mask.

On further questioning, patient’s mother asked the grandfather who had been taking care of him if he had given him any new medications. He admitted to administering Oragel to the patient’s teeth multiple times per day for the past couple of days.

In ED patient was given: methylene blue: 37 mg (2mg/kg over 15min) (02/24/19 12:02:00 EST) Sodium Chloride 0.9%: 372 mL (02/24/19 11:27:00 EST)

Hospital Course: ABG was repeated and MethB had normalized. Patient did not have return of cyanosis and never experience respiratory distress during his hospital stay. OMFS was also consulted for his toothache and patient started on IV Unasyn for right buccal swelling, which was fluctuant, erythematous and tender with palpation. He underwent drainage of dental abscess and tooth removal. He was transitioned Amoxicillin PO for 1 week, and discharged the next day

WHAT IS IN ORAGEL? 20% Benzocaine!

Pearls & Take Away: Methemoglobinemia!


  • Definition: An abnormal elevation of Methemoglobin, which refers to, the ferric form of hemoglobin (Fe+3) that is unableto bind to O2.
  • An abnormal MetHb level is any level > 1%
  • Suspect in any patient with cyanosis not responsive to supplemental oxygen!!!
  • Pulse Oximetry readings are inaccurate in the presence of MetHb


  • Oxidized Fe+3 sites on MtHb are unable to bind to oxygen
  • This results in a leftward shift in the oxyhemoglobin dissociate curve which leads to decreased oxygen delivery
  • Methemoglobinemia occurs when there is a deficiency of the reducing enzyme (NADH MetHb reducatase) OR when there is increased oxidative stress to the body


  1. NADH reductase deficiency – unable to reduce ferric to ferrous iron (Fe3+→ Fe2+)
  2. Exposure to oxidizing agent
  3. Benzocaine and other local anesthetics
  4. Contaminated well water
  5. Nitrofurantoin, Nitroprusside
  6. Sodium Nitrite, Amyl nitrite
  7. Antimalarials: Quinolones
  8. Dapsone (used to treat leprosy, PCP pneumonia, toxoplasmosis, dermatitis herpetiformis, brown recluse bite)
  9. Aniline dyes
  10. Phenazopyridine[3]


  • Patients with anemia or preexisting cardiopulmonary disease will show symptoms sooner (i.e. CHF, Pneumonia, COPD, anemia, etc)
  • Important diagnosis feature (Saturation < 85% without response to 100% FiO2)
  • Wavelength averaging by the pulse oximeter causes a falsely low O2 reading
  • Symptoms depend on level of metHb:
  • < 20%:Asymptomatic or very mild symptoms; gray-blue cyanosis, chocolate brown colored blood
  • 20-50%:Anxiety, HA, weakness, lightheadedness, tachycardia, dyspnea, dizziness, syncope
  • 50-60%:Myocardial ischemia, dysrhythmias, ischemia, tachypnea, depressed mental status due to CNS hypoxia, seizure
  • >70%:Severe hypoxia, Death


  • Emergent: Anaphylaxis, Angioedema, Airway Obstruction, Aspiration, Asthma, Cor pulmonale, Non-cardiogenic or Cardiogenic pulmonary edema, Pneumonia, Pulmonary Embolism, Tension Pneumothorax, Tamponade, MI, Pericarditis, Myocarditis
  • With normal/increased Respiratory effort—-Anemia, CO Poisoning, Salicylate toxicity, DKA, Sepsis, renal failure, metabolic acidosis


  • ABCs
  • Provide 100% Fio2, —-lack of response should raise concern for methemoglobinemia. If patient does response to supplemental oxygen then most likely it is from a cardiovascular or pulmonary etiology
  • Venous blood gas (VBG)
  • Arterial blood gas (ABG) would reveal a normal
  • Co-Oximeter panel for MetHb level (Can use VBG or ABG) : Measures levels of oxyhemoglobin, Carboxyhemoglobin,methemoglobin, reduced hemoglobin
  • “Chocolate brown” color of blood
  • If no response to Oxygen —– Draw MetHb concentration

MetHB > 30% ——àSpO2 will fall to 80-85% and will not increased despite additional oxygen.  This occurs due to light absorption of both oxyHb and deoxyHb.

  • Who gets treatment?
  1. MetHb < 25% with symptoms, abnormal vital signs, metabolic acidosis or end organ dysfunction (AMS, seizure, etc)
  2. MetHb > 25% regardless of symptoms


  • Initiate treatment if symptomatic OR asymptomatic with MetHB > 25%
  • 1-2mg/kg Methylene Blue IV over 5-15 minutes, repeat if no effect with initial dose. Flush line after infusion completed
  • Clinical improvement seen within 20 minutes
  • Contraindicated in G6PD deficiency as it can induce acute hemolytic anemia
  • Exchange transfusion for symptomatic patients with G6PD deficiency as well.
  • Hyperbaric oxygen when methylene blue ineffective or contraindicated