The instruction to remove nail polish before surgery is common and relates purely to patient safety and the reliability of monitoring equipment. This rule ensures the surgical team receives immediate and accurate data about oxygen delivery, a critical bodily function. Without accurate monitoring, subtle changes in your condition could be missed, potentially leading to serious complications.
The Critical Role of Pulse Oximetry
During any surgery requiring anesthesia or deep sedation, the patient’s oxygen levels must be monitored continuously in real-time. This is accomplished using a small, non-invasive device called a pulse oximeter, which typically clips onto a finger or toe. The anesthesia team uses this data consistently to ensure your breathing and circulation remain stable throughout the procedure.
The pulse oximeter measures oxygen saturation (SpO2), which is the percentage of hemoglobin in your blood carrying oxygen. A normal reading is usually between 95% and 100%. This measurement is a direct indicator of how well oxygen moves from your lungs into your bloodstream and circulates to your tissues.
If a patient’s oxygen saturation drops (hypoxemia), the surgical team must know instantly to correct the problem before it harms the brain or other organs. The pulse oximeter provides a continuous, graphical display of this information, which is a significant advancement in modern surgical safety. This early warning allows for immediate intervention, preventing severe postoperative complications.
How Nail Polish Interferes with Light Signals
The core issue lies in the pulse oximeter’s technology, which relies on light absorption. The device shines two specific wavelengths of light—red and infrared—through the capillary bed beneath the nail. Hemoglobin, the protein in red blood cells that carries oxygen, absorbs these lights differently depending on whether it is bound to oxygen.
The oximeter measures the ratio of light absorption at the two wavelengths to calculate the percentage of oxygenated hemoglobin in the arterial blood. Pigments in nail polish, especially dark or opaque colors (blue, black, green, or purple), can absorb or scatter these light beams before they reach the sensor. This obstruction confuses the device, resulting in a reading that does not accurately reflect the actual oxygen saturation.
This interference can manifest in two problematic ways. It can cause a falsely low reading, which might lead the surgical team to administer unnecessary oxygen or treatment. More dangerously, it can cause a falsely high reading, which masks a true drop in oxygen saturation and delays life-saving interventions.
Why Removal is Non-Negotiable
The removal rule applies to all forms of nail coverage, not just traditional polish, to eliminate all risk of signal interference. Gel, shellac, and acrylic nails present a greater challenge than standard polish because they are often thicker and more opaque, further impeding light transmission. These materials can also cause the oximeter to overestimate the oxygen level, a particularly dangerous error in the operating room.
Although lighter colors or clear coats may interfere less than dark pigments, surgical protocols require the removal of all polish from at least one finger, usually the index finger. This universal requirement ensures there is no risk of error from color or brand variation, providing a guaranteed clean site for the most accurate reading. Furthermore, the natural color of the nail bed is an immediate visual cue for the medical team. A bluish tint indicates poor circulation or low oxygen levels, a sign that nail polish would completely conceal.
Alternative Sites for Oxygen Monitoring
If a patient cannot remove their nail coverings due to circumstances like prosthetic nails, the surgical team has alternative monitoring options. Continuous and accurate tracking of oxygen saturation is mandatory, and a clean site will always be found. The device can be repositioned away from the fingertips to other areas where the skin is thin and blood flow is easily accessible.
Common alternative sites for pulse oximeter placement include the earlobe, a toe, or the bridge of the nose. Specialized probes can also be placed on the forehead. These sites are less likely to be covered in polish or acrylics and allow the device to perform its essential function without obstruction. This flexibility ensures that patient safety is maintained, even if the preferred fingertip site is unavailable for monitoring.