Pre-operative instructions commonly require patients to remove all nail polish before surgery. This is not a cosmetic preference but a firm safety measure. Nail polish directly interferes with equipment used to monitor the body’s response while under anesthesia. This monitoring provides immediate, life-saving information to the surgical team, especially concerning the physiological changes that occur during sedation.
The Essential Monitoring System: Pulse Oximetry
The standard device used to continuously track a patient’s oxygen status during surgery is the pulse oximeter. This small, non-invasive clip is typically placed on a fingertip, earlobe, or toe. Its function is to measure the percentage of oxygen-carrying hemoglobin in the blood, known as peripheral oxygen saturation (SpO2).
The device works by emitting two different wavelengths of light—red and infrared—which shine through the tissue to a detector. Oxygenated hemoglobin and deoxygenated hemoglobin absorb these two light wavelengths differently. Oxygen-rich blood absorbs more infrared light, while oxygen-poor blood absorbs more red light.
By analyzing the ratio of the light that passes through the finger and reaches the sensor, the oximeter calculates how much hemoglobin is bound to oxygen. This measurement is displayed as a percentage, with 95% to 100% generally considered normal. Because the device uses the pulsing of arterial blood, it provides a real-time assessment of respiratory function.
How Pigmentation Blocks Critical Readings
The presence of nail polish creates a physical barrier that disrupts the light transmission needed for the pulse oximeter to function correctly. The pigments absorb or scatter the red and infrared light, preventing the necessary amount from reaching the detector. This interference causes the oximeter to generate an inaccurate or completely failed reading.
Darker colors, such as black, dark blue, green, and brown, interfere the most because their dense pigments absorb light across a broad spectrum. Studies show these dark shades can lead to an artificial underestimation of oxygen saturation by up to five percent. Furthermore, thick coatings like gel polish, acrylics, and shellac present a greater obstacle due to their opacity and thickness.
The issue is not limited to dark or vibrant colors, as even light or clear polishes can cause problems. These thick layers can scatter the light or block enough signal to make the reading unreliable. Since a surgical environment requires the highest degree of accuracy, any substance that compromises the light path must be removed before the procedure.
The Dangers of Undetected Low Oxygen Levels
The primary danger medical monitoring seeks to prevent is hypoxia, a state where the body’s tissues are not receiving enough oxygen. This is a particular concern during surgery because general anesthesia can suppress the normal respiratory drive. Anesthesia medications can temporarily paralyze breathing muscles, necessitating careful control over oxygen flow and ventilation.
If a patient’s oxygen level begins to drop, the pulse oximeter sounds an alarm, allowing the anesthesia team to intervene immediately. Undetected hypoxia, even for a short period, has severe consequences, as the brain and heart require a constant oxygen supply. Loss of oxygen for as little as 60 seconds can cause brain cells to die, leading to irreversible damage or coma.
A significant percentage of patients experience a hypoxemic event during surgery, particularly during the induction or emergence phases of anesthesia. The ability to accurately and instantly track oxygen saturation is a mandatory safety standard. When nail polish renders this device unreliable, it removes this safety net, making bare nails a non-negotiable requirement for patient safety.