Masimo's noninvasive SpMet provides measurements comparable to invasive methemoglobin testing

Masimo (Nasdaq: MASI) announced today that a new clinical study published in Anesthesia & Analgesia demonstrates that Masimo noninvasive and continuous methemoglobin (SpMet®) measurements provide a high degree of agreement in measurements with corresponding laboratory values of methemoglobin obtained by invasive methemoglobin testing.  In addition, the authors concluded that SpMet could facilitate early diagnosis and treatment of methemoglobinemia during high-risk procedures.

Methemoglobin (metHb) is an oxidized form of hemoglobin that is incapable of oxygen transport.  Methemoglobinemia is defined as higher than normal methemoglobin levels and can be induced by common topical anesthestics (e.g. Benzocaine, Cetacaine, Prilocaine, Lidocaine) and over 30 other therapeutic drugs prevalent in both the hospital and outpatient settings.  If undetected and untreated, methemoglobinemia can result in significant reduction in oxygen delivery to the tissues resulting in vital organ damage.  Prevention of vital organ injury requires prompt detection and treatment as significant organ injury can occur in as little as five minutes. However, traditional methods of detection rely on physical signs and symptoms, which may be non-specific and subtle or invasive laboratory blood tests that can take a long time.  Masimo SpMet provides an accurate, quick, and easy-to-use way to noninvasively and continuously measure methemoglobin levels in the blood, which helps clinicians assess methemoglobinemia to determine treatment and additional test options.

In the current study, researchers from the University Clinic of Schleswig-Hostein in Luebeck, Germany, compared the accuracy of SpMet from the Masimo Radical-7 Pulse CO-Oximeter with invasive arterial blood gas measurements in 40 patients receiving prilocaine as a regional anesthetic for orthopedic surgery.  A total of 20 patients received an interscalene brachial plexus block with 300 mg prilocaine while the other 20 patients received a combined femoral-sciatic nerve block with two 300 mg injections of prilocaine (600mg total).  Continuous monitoring of SpMet and SpO2 was initiated before the onset of regional anesthesia and blood gas analysis of methhemoglobin and oxygen saturation (SaO2) was performed at the first injection of prilocaine and at 15, 30, 60, 120, 180, 240, 300, and 360 minutes.  Study results showed a "high degree of agreement in measurement" between noninvasive and continuous SpMet and SpO2 and corresponding laboratory values of methemoglobin and SaO2 with a bias of 0.27% and 95% confidence limits of +1.33%—leading researchers to conclude that Masimo SpMet "may facilitate early diagnosis and treatment, when necessary, of dyshemoglobinemia."  

According to Steven J Barker, PhD, MD, Professor and Head of the Department of Anesthesiology at University of Arizona and Masimo Board Member, "I've seen the lifesaving benefits of Masimo SpMet monitoring first-hand when a surgical patient developed potentially fatal methemoglobin levels from local anesthestic toxicity.  Traditional laboratory blood testing did not provide results quickly enough to diagnose and treat this critically-ill patient.  Thankfully, SpMet provided immediate detection of her methemoglobinemia and successfully guided our treatment."

SpMet is available as part of the Masimo rainbow® SET platform—the first-and-only technology to noninvasively and continuously measure total hemoglobin (SpHb®), oxygen content (SpOC™), carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), Pleth Variability Index (PVI®), and acoustic respiration rate (RRa™), in addition to the 'gold-standard' Measure-Through Motion and Low Perfusion performance of Masimo SET® oxyhemoglobin (SpO2), perfusion index (PI), and pulse rate (PR).  

"Unrecognized methemoglobinemia is a patient safety problem in every hospital on the planet; however, most healthcare providers are not aware of the number of drugs that cause methemoglobinemia, which is not uncommon and often goes unrecognized," stated Michael O'Reilly, MD, EVP of Medical Affairs at Masimo   "Over 30 drugs have been shown to induce severe methemoglobinemia, including commonly-used local anesthesics such as Lidocaine, Benzocaine, and Prilocaine; antibiotics like Trimethoprim, Sulphonamides, and Dapsone; and many other therapeutic drugs such as Metoclopramide, Chlorates, Nitrates and Bromates to name a few.  The morbidity risks associated with methemoglobin, which significantly decreases oxygen delivery, is completely underappreciated and neonates and infants less than 6 months of age are particularly susceptible because of their immature metabolic pathways.  Given its prevalence and susceptible populations, I believe that SpMet offers a critical opportunity to noninvasively and continuously monitor every patient for this very serious, unrecognized and potentially deadly problem."


Masimo Corporation


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