Myasthenic crisis tied to high lactic acid levels after thymectomy
Data examined on 340 MG patients who had surgery to remove thymus gland
High levels of lactic acid in the bloodstream immediately after surgery to remove the thymus gland were associated with an increased risk of postoperative myasthenic crisis, or POMC, among people with myasthenia gravis (MG), a study reveals.
“These findings offer valuable insights for clinical decision-making and monitoring of prognosis in managing patients with MG,” the study’s researchers wrote.
The study, “Predictive Value of Perioperative Blood Lactic Acid Levels for Postoperative Crisis in Myasthenia Gravis Patients Undergoing Thymectomy,” was published in Muscle & Nerve.
MG is an autoimmune disease marked by muscle weakness and fatigue. It’s strongly associated with the thymus gland, an organ in the chest that’s part of the immune system. Thymus abnormalities, including thymic hyperplasia (thymus enlargement) and thymoma (thymus tumor), are found in up to 90% of patients, according to estimates.
A thymectomy, a surgery to remove the thymus, is frequently recommended to patients with generalized MG under age 65. The procedure can ease symptoms, lessen the need for medications, and, in some patients, lead to complete disease remission.
Myasthenic crises are life-threatening MG complications marked by severe muscle weakness and respiratory failure that requires breathing support. When a crisis occurs after a thymectomy, it’s called a POMC.
POMC and lactic acid levels
Research suggests that high levels of lactic acid in the bloodstream after surgery can be a sign of tissue hypoxia, or low oxygen, that comes with an increased risk of complications and death. The predictive value of blood lactic acid levels for POMC is unclear, according to researchers in China who examined clinical data on 340 MG patients who had a thymectomy in an effort to learn more.
Of the 144 males and 196 females identified, 26 developed POMC, which was defined as the need for invasive or noninvasive breathing support for more than 24 hours within 14 days after surgery.
Those who developed POMC had a higher incidence of myasthenic crises before surgery and worse disease severity after surgery, as indicated by a significantly higher MGFA clinical classification.
More than 90% of those who didn’t develop POMC underwent extended transsternal thymectomy, where an incision is made through the breastbone to reach the thymus. The proportion of POMC patients who underwent video-assisted thoracoscopic surgery (VATS) thymectomy, a less invasive method that uses a tiny camera to guide the surgery, was higher than that of the non-POMC group.
Before surgery, lactic acid levels were comparable between the two groups. However, a day after surgery, the patients who developed POMC had higher lactic acid levels. Also, the POMC group showed a greater increase in the ratio of lactic acid change and more frequently saw an increase in lactic acid levels that exceeded 50%.
In a statistical analysis, the risk of POMC was more than 67 times higher among those with a history of myasthenic crisis than in those without it, and 4.33 times higher for those who underwent VATS. An elevation in lactic acid levels by more than 50% increased the risk of POMC by 2.86 times, and for those with high postoperative lactic acid levels, the risk was 2.68 times higher.
Lastly, researchers found that postoperative lactic acid levels predicted POMC with an accuracy greater than 80% at a threshold of 1.98 millimoles of lactic acid per liter of blood.
“While the association between elevated postoperative lactic acid and POMC requires further validation, monitoring lactic acid levels through routine blood gas analysis may offer clinicians a practical tool to identify patients at risk for POMC,” the researchers wrote. “Future research should explore further the underlying mechanisms linking elevated lactate levels to POMC.”
About the Author
