Roy Cho

Measurement of Femoral Vein Diameter by Ultrasound to Estimate Central Venous Pressure

RATIONALEnCentral venous pressure (CVP) can be estimated by ultrasound of the inferior vena cava (IVC), but imaging the IVC is sometimes challenging. The femoral vein is easily imaged by ultrasound and might therefore provide an alternate target for estimating CVP.nnnOBJECTIVESnTo assess femoral vein diameter (FVD) measured by ultrasound imaging for estimating CVP.nnnMETHODSnWe prospectively measured CVP and FVD in 97 patients. Receiver operating characteristic curves were used to assess the ability of FVD to predict specific CVP values: less than 10 mm Hg, less than 8 mm Hg (low CVP), and greater than 12 mm Hg (high CVP). Interobserver variability of FVD measurement was assessed in 20 patients.nnnMEASUREMENTS AND MAIN RESULTSnThere was moderate correlation between FVD and CVP (ru2009=u20090.66, Pu2009<u20090.001). FVD less than or equal to 0.8 cm was the best predictor of CVPu2009<u200910 mm Hg, with an area under the curve (AUC) of 0.894 and a 95% confidence interval (CI) of 0.82 to 0.97. FVD less than or equal to 0.7 cm performed best for predicting low CVP (AUCu2009=u20090.97; 95% CI, 0.94-0.99) and FVD greater than or equal to 1.0 cm for high CVP (AUCu2009=u20090.80; 95% CI, 0.72-0.89). However, FVD greater than or equal to 1.2 cm had the greatest specificity (94%) for high CVP. Interobserver variability in FVD measurements was 8.3u2009±u20097.2%.nnnCONCLUSIONSnThe results of this exploratory study suggest that the accuracy of FVD measured by ultrasound imaging for estimating CVP is comparable to that which has been reported for ultrasound measurement of IVC diameter. FVD may provide an alternative approach when the IVC is difficult to image. Additional studies on other cohorts of patients are warranted to validate our proposed FVD cutoff values for predicting low and high CVP.

Heparin-Induced Hyperkalemia in a Patient Diagnosed with Thyroid Storm

Objective: To describe a case of heparin-induced hyperkalemia and the role for transtubular potassium gradient (TTKG) to guide fludrocortisone therapy. Case Summary: A 52-year-old white male developed hyperkalemia after receiving intravenous unfractionated heparin (UFH) for atrial fibrillation during thyroid storm. Admission laboratory results were noteworthy for normal potassium levels, undetectable thyroid-stimulating hormone, and mild transaminitis. Treatment for thyroid storm was initiated but UFH was stopped because the international normalized ratio was subsequently found to be elevated. Rising potassium levels developed just 24 hours after UFH discontinuation, without exogenous potassium supplementation, renal dysfunction, or acidosis. A TTKG was low, reflecting a hypoaldosterone state. In addition, the Naranjo probability scale indicated probable medication-associated hyperkalemia. Heparin-induced hyperkalemia (HIH) was suspected and oral fludrocortisone 0.2 mg was given daily alongside serial TTKG measurements. TTKG and hyperkalemia normalized with 2 days of treatment. Discussion: UFH is commonly used; therefore, clinicians must be cautious of hyperkalemia. Although HIH usually resolves after discontinuation of heparin, it may persist despite discontinuation of the drug, as highlighted by this case. In this setting, a TTKG should be determined, which can be used to guide fludrocortisone therapy. Conclusions: HIH can occur despite discontinuation of heparin, and TTKG can be helpful in guiding fludrocortisone treatment in this circumstance.

Endobronchial thermoplasty for asthma

Asthma is an incurable chronic disease affecting approximately 24 million people in the United States. The hallmark features of asthma are reversible airflow obstruction, airway hyperresponsiveness, airway inflammation, bronchoconstriction, and excessive mucus secretion. Clinical symptoms include episodic or persistent breathlessness, wheezing, cough, or chest tightness/pressure. Forty-five percent of asthmatics continue to have yearly exacerbations and the disease is responsible for approximately 3,600 annual deaths. Pharmacologic advancements have continued to grow as the individual phenotypes of asthma are better delineated but there continues to be small population of asthmatics that are less responsive to pharmacologic therapy. Bronchial thermoplasty (BT) is an innovative procedure targeted primarily at decreasing airway smooth muscle (ASM) which is considered by some to be a vestigial organ. Decreasing the ASM bulk decreases hyperresponsiveness and bronchoconstriction leading to decreased exacerbations, decreased cost on the healthcare system, and improvement in patient quality of life.