Category: Critical Care
Posted: 5/16/2017 by Kami Windsor, MD
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High flow nasal cannula (HFNC) is a valid option in the management of acute hypoxic respiratory failure (AHRF) without hypercapnia, as evidenced by multiple studies including the FLORALI trial. Failure of HFNC, however, may result in delayed intubation and worsened clinical outcomes.
Factors predicting HFNC failure and subsequent intubation include:
Consider whether or not HFNC is appropriate in your patient with AHRF, and if you use it, reevaluate your patient to ensure improvement, or escalate their respiratory support.
For patients with acute hypoxic respiratory failure without hypercapnia, the FLORALI trial demonstrated that high flow nasal cannula (HFNC) therapy increases ventilator-free days, reduces 90-day mortality, and is associated with better comfort and lower dyspnea severity when compared to conventional oxygen therapy and non-invasive ventilation (NIV). Failure of HFNC, however, may result in delayed intubation and worse clinical outcomes in patients with acute hypoxic respiratory failure. So how do we predict in the ED which patients are going to fail?
Sztrymf et al. evaluated patients placed on HFNC for nonhypercapneic acute hypoxic respiratory failure, who later went on to require endotracheal intubation. The cohort who failed HFNC had significantly:
- higher RR at 30 & 45 minutes after initiation of HFNC
- lower SpO2% at 15, 30, and 60 minutes
- higher incidence of paradoxical breathing (thoracoabdominal dyssynchrony) at 15, 30, 60, and 120 minutes
In an observational study of patients with ARDS,* Messika et al. found that factors predicting HFNC failure included:
- a higher Simplified Acute Physiology Score II (SAPS II; 46 v. 29, p=.001)
- additional organ system failure (mostly hemodynamic or neurological)
- trends towards lower PaO2:FiO2 ratios and higher RR
So don’t set it and forget it! Consider a different method of respiratory support if your patient has multi-organ system failure, especially if they are in shock or have altered mental status. If you do use HFNC, reevaluate your patient at 15 minutes and again at 30 minutes to make sure their respiratory rate and SpO2 have improved and that there is no paradoxic breathing (or it is resolving). If not, move on to NIV or invasive mechanical ventilation.
*acute respiratory failure occurring within 1 week of known clinical insult with PaO2:FiO2 <300mmHg and bilateral opacities on chest x-ray not attributable to cardiac failure/volume overload
1. Frat JP, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med. 2015;372:2185–96.
2. Sztrymf B, Messika J, Bertrand F, et al. Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med. 2011;37:1780–6.
3. Messika J, Ben Ahmed K, Gaudry S, et al. Use of high-flow nasal cannula oxygen therapy in subjects with ARDS: a 1-year observational study. Respir Care. 2015;60(2):162-9.
4. Hernandez G, Roca O, Colinas L. High-flow nasal cannula support therapy: new insights and improving performance. Crit Care. 2017;21(1):62.
Category: Critical Care
Keywords: Central venous catheter, ultrasound (PubMed Search)
Posted: 4/18/2017 by Kami Windsor, MD
(Updated: 4/27/2024)
Click here to contact Kami Windsor, MD
Save time by using bedside ultrasound to confirm above-the-diaphragm central venous catheter (CVC) placement rather than waiting for chest x-ray confirmation:
1. Perform rapid push of saline (it doesn’t have to be agitated) through CVC while cardiac probe is placed with right atrium in view. Immediate visualization of bubbles (or “atrial swirl”) essentially confirms correct placement.
2. Perform the usual search for ipsilateral lung-sliding and the waves-on-the-beach to rule out procedural pneumothorax.
It makes sense that it’s going to be faster for you to use that internal jugular/subclavian central venous catheter (CVC) you just placed if you confirm with bedside ultrasound instead of waiting for the radiology tech to get the chest x-ray. But what’s the data?
Using pooled data from of 15 studies with 1553 CVC placements, Ablordeppey et al. found that ultrasound had a sensitivity of 86% and 98% specificity for detecting catheter malposition, with a positive likelihood ratio (LR) of 31.1 and a negative LR of 0.25. There was an almost 100% sensitivity and specificity for pneumothorax detection, and reduced confirmation time by 58 minutes.These findings are generally consistent across the board for the other studies out there.
1. Ablordeppey EA, Drewry AM, Beyer AB, et al. Diagnostic accuracy of central venous catheter confirmation by bedside ultrasound versus chest radiography in critically ill patients: a systematic review and meta-analysis. Crit Care Med. 2017; 45(4): 715-24.
2. Gekle R, Dubensky L, Haddad S, et al. Saline flush test: Can bedside sonography replace conventional radiography for confirmation of above-the-diaphragm central venous catheter placement? J Ultrasound Med. 2015;34(7):1295-9.
3. Weekes AJ, Johnson DA, Keller SM. Central vascular catheter placement evaluation using saline flush and bedside echocardiography. Acad Emerg Med. 2014; 21:65-72.
