New Scoring System Can Help ID Patients Who Need Intubation

Analysis calculates intubation risk from ER records of patients with angioedema

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by Steve Bryson, PhD |

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Researchers have developed a simple scoring system to help clinicians identify angioedema patients at high or low risk for intubation, a medical procedure in which a breathing tube is placed into the windpipe through the mouth or nose.

Specifically, the need for a breathing tube, called endotracheal intubation, due to angioedema-related swelling attacks was predicted by shortness of breath, drooling, swelling of the throat or the front of the tongue, and high blood pressure, according to an analysis of emergency room medical records in the U.S.

These findings require validation before clinical implementation, researchers noted.

The study, “Clinical predictors of endotracheal intubation in patients presenting to the emergency department with angioedema,” was published in The American Journal of Emergency Medicine.

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Swelling in neck and throat can be life-threatening

Angioedema is marked by swelling of the skin around the lips, face, tongue, neck, or genitals.

Swelling episodes can be triggered by genetic factors, such as hereditary angioedema, or by allergic reactions to certain foods, insect bites, and latex. Some medications can induce angioedema without an allergic reaction, especially ACE inhibitors used to treat high blood pressure.

When swelling occurs in the neck and throat, it may limit breathing and be life-threatening, requiring emergency assessment. In severe cases, patients may undergo endotracheal intubation to help them breathe.

However, guidance from the medical literature about clinical factors to predict the need for intubation is limited. As such, emergency physicians must rely largely on clinical experience alone to decide whether to safely discharge an angioedema patient or intubate, and/or admit them to the hospital for ongoing monitoring.

The lack of guidelines prompted researchers in the U.S. to review the medical records of angioedema patients to identify factors that led to intubation.

The team reviewed the charts of 594 patients with a primary diagnosis of angioedema who were admitted to a single emergency department over about five years (November 2012 to August 2017). Participants were randomly divided into a training set of 446 (75%) and a test set of 148 (25% patients). Overall, 103 patients were intubated (17.3%) over the study period.

Most angioedema patients were older, with 64.5% older than 50 years, 53.5% were female, and 77.9% were African American. Co-existing conditions (comorbidities) were common, including high blood pressure, or hypertension (75.1%), diabetes (26.4%), high blood fats (23.9%), tobacco use (36.2%), allergies (45.8%), and prior history of angioedema (24.9%). ACE inhibitors to treat high blood pressure were common (57.1%).

Among the 446 cases in the training set, 81 were intubated. Single factors significantly associated with increased intubation rates included drooling, wheezing, difficulty swallowing, hoarseness, or shortness of breath. Intubation was significantly more common among patients with swelling of the throat and the front or back of the tongue.

Intubation occurred more often among those older than 50, insured by Medicare, or with pre-existing heart disease, end-stage kidney disease, or high blood pressure. Intubation also occurred more frequently with any ACE inhibitor, specifically a medication called lisinopril. The researchers noted that lisinopril comprised the overwhelming majority of ACE inhibitors.

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Predictive value for intubation was high

After adjustments, a final model — which included factors such as high blood pressure, swelling of the throat or the front of the tongue, shortness of breath, and drooling — was used to develop an angioedema risk score ranging from 0 (low risk) to 15 (high risk). For the training set, the predictive value of the risk score for intubation was 87.55%.

Risk scores were then applied to the test set of 148 cases, which included 22 intubations. Here, the predictive value for intubation was 86.1% which was considered highly predictive. The team proposed that scores from 0–4 reflect low risk, and 5–7 for moderate risk. A score over 7 equals high risk and a need for intubation.

Based on these cut-off scores, for those in the training set, low-risk patients were intubated at a rate of 3.4%, moderate-risk patients at 22.6%, and high-risk at 72.1%. Among the test set, intubations occurred in 5.1% of the low-risk group, 16.7% in the moderate-risk group, and 78.6% in the high-risk group.

Finally, the team examined the duration of intubation versus the risk score to clarify the need for intubation. In patients with angioedema induced by allergies or ACE inhibitors, swelling lasted more than 24 hours.

Among the training set, a larger proportion of the low-risk group (56%) was intubated for less than 24 hours compared with the high-risk group (23%). This trend was also seen in the test set, in which 40% with low risk, and 28% with high risk, were intubated for less than 24 hours.

“This study suggests that a simple scoring algorithm may aid in predicting angioedema patients at high and low risk for intubation,” the researchers wrote. “The presence of a diagnosis of hypertension, shortness of breath, drooling, [throat] or anterior [front] tongue edema are predictors of intubation.”

“External validation of this scoring algorithm is necessary prior to clinical implementation,” the researchers noted.