An 1-month-old baby boy presented to the skin outdoor in the arms of his mother. His mother complained of bluish to black discoloration of the right thumb of hand for 10 days and bluish-black followed by yellowish discoloration of the left thumb for almost 13 to 15 days. On further history taking, she elaborated that the child was prematurely born and was admitted to neonatal care unit (NICU) of the same hospital since birth. He was admitted to the NICU due to having breathlessness and abnormal behavior. He was kept in NICU for over 20 days. The baby boy was taken care of properly and all the necessary investigations were done on time. His complete blood count, erythrocyte sedimentation rate (ESR), liver function test (LFT), renal function test (RFT), urine complete and microscopy, bleeding time, clotting time, prothrombin time-INR got done and everything was within the normal range. ECG and chest X-ray were found normal. On further asking about the sequence of events of discoloration, the mother told that initially left thumb got affected and bluish color started appearing on its nail and slowly covering up the complete nail and also surrounding the skin with darkening of the discoloration than before. Likewise, after 4 to 5 days, right thumb nail got affected in the same manner. Meanwhile, when the right thumb nail was showing bluish/black discoloration, the left thumb nail started a change in color from bluish/black to yellowish. Assuming an occlusive vasculopathy, a call was made to the nursing staff in NICU who explained the prolonged admission in NICU and that the thumbs had continuous pressure due to usage of pulse oximeter during entire stay in NICU. After 3-4 days of admission, the nail color started changing. As the pediatrician applied a pulse oximeter to the right thumb after getting bluish discoloration of the left thumb, the right thumb also showed similar changes.
On examination, the left thumb nail was yellow with a peripheral rim of color spreading up to proximal and lateral nail folds for 10 days. The right thumb nail similarly showed blue color as of left thumb for 13 to 15 days [Figures 1 and 2]. Differential diagnoses in this case that were kept in mind were peripheral and central cyanosis, septicemia, discoloration due to any drug, and substance abuse in the mother. The baby’s mother was counselled about the nature of the lesions. She was convinced by the counselling and did not follow up after the proper explanation of the factors causing discoloration.
The pulse oximeter is considered a safe medical technology. It is used to measure oxygen saturation by illuminating the skin and measuring changes in light absorption of oxygenated and deoxygenated blood of arterial oxygen saturation in sick neonates.[1,2] Pulse oximeter probes have a light emitter and a sensor that should be aligned to capture the light on the other side of the tissue bed. Finger or toenail beds are the most commonly used tissue beds. Finger injuries due to pulse oximeter may have single or combinations of multiple mechanisms. It may be electrical, overheating of the light-emitting diode, resulting from a topical reaction to the probe itself or residual manufacturing chemicals, or resulting from mechanical pressure exerted by the probe. The situation can be further worsened by decreased blood flow consequent to controlled hypotension. Tight contact causing higher pressure for shorter periods or lower pressure for longer periods may cause ischemia. Besides, type of probe like clip-on probes are associated with an increased risk of finger damage. Sometimes, when an adult pulse oximeter is used for the pediatric population, even a shorter duration can cause damage.
The pediatric population is more susceptible to these injuries because anatomical and physiological characteristics make them more predisposed to the passage of electric current and heat of pulse oximeter probes. Also, their prematurity, thinner skin, lower fat content, higher water content, and a relatively smaller probe contact area can lead to deeper and extensive tissue damage.[7,8]
In our case, we believe the injury was caused by the pressure of the probe, which was used continuously and repeatedly, and also baby was premature, and so underlying thin skin, impaired barrier effect, and hypotension may be thought of as possible reasons. Though the pathophysiology of yellowish discoloration of nails has not been well established, it can be explained that it was an ischemic injury to the blood vessels causing extravasation of blood. When the blood got hemolyzed, all the color changes followed.
Proper monitoring of the patient and technique of using pulse oximetry probes is required in prevention and management of complications. The routine moving of the finger probe to a different finger is recommended every 3 to 4 hours. There should be frequent checks to make sure the probe is accurately placed on the finger. The site of placing should be inspected regularly for reduced blood flow. Flexible sensors should not be wrapped tightly around the end of the tissue bed. Staff should be educated to monitor patients.
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