High Flow Nasal Cannula (HFNC) in acute respiratory hypoxemia

• HFNC has been used for a variety of patients with respiratory distress (See previous pearl: https://umem.org/educational_pearls/2411/)
• The benefits include:

1. Low levels of positive pressure in the upper airways
2. High flow rates, titratable oxygen levels, humidied air, more comfort than NIV
3. Decreases physiological dead space by flushing out CO2 therefore improving oxygenation

• A recent trial published in NEJM looked at using HFNC in patients with respiratory failure

The Trial:

• Patients without hypercapnia and with acute hypoxemic respiratory failure (PaO2/FiO2 <300 or less) were randomized to HFNC, standard oxygen therapy via face mask, or non-invasive positive pressure ventilation (NIV).
• Primary outcome was proportion of patients intubated at day 28
• 310 patients in European ICUs

Results:

• Intubation rate (p=0.18): 38% in the HFNC; 47% in the standard group; 50% in the NIV
• Number of ventilator free days at day 28 was significantly higher in the HFNC
• Higher mortality at 90 days with NIV
• No difference in intubation rates but there were more ventilator free dates as well as a lower 90 day mortality

Bottom line:

Consider using HFNC prior to or while deciding on intubation in patients with hypoxemic respiratory failure usually due to pneumonia

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We all dread performing lumbar punctures on the obese patient. The traditional standard length spinal needle (9 cm) is becoming increasingly inadequate in reaching the subdural space in our overweight society.

Abe et al developed a formula for selecting the proper needle length to reach the middle of the spinal canal from the skin using retrospective CT data from 178 patients.

Length of needle (cm) = 1+ 17 x Weight (kg)/ Height (cm)

Given the average height of the American woman (163 cm or 5’4’’) our standard length spinal needle will FAIL to reach the mid-thecal space if a woman weighs more than 170 lb (75 kg)!!!

Paul Blart Mall Cop, and King of Queens star Kevin James (5’8’’, 285 lb) would require a 13.7 cm spinal needle. This means even our long spinal needles (12.7 cm) would FAIL by 1 cm.

Note that this formula resulted in selection of needles too small (6%) and too long (31%) of the time. Abe’s linear correlation had an R value of 0.81, (p<.001)

Bottom-Line: Consider use of a long spinal needle (12.7 cm) or IR guided LP in overweight /obese patients and the above formula to guide your depth of insertion

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Stress-Induced Cardiomyopathy

• Stress-induced cardiomyopathy (SIC) can be seen in a variety of critical illnesses, especially severe neurologic conditions.
• SIC is believed to be caused by excess sympathetic stimulation of the myocardium.
• When managing a patient with SIC, limit further catecholamine exposure by avoiding vasopressors if possible.
• If the patient requires inotropic support, consider using an agent without catecholamine activity, such as milrinone.

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Do you need to get stuff out of the thorax (like fluid or air) and don't want to place a HUGE chest tube? Consider a pigtail catheter; don't know how to place one? Well check out this video and learn how.

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Reperfusion Ventricular Fibrillation

Ventricular fibrillation during reperfusion in STEMI is an infrequent, but serious complication.

Among ~4000 with STEMI between 2007-2012, 71 (1.9%) had reperfusion Vfib.

Increased risk for reperfusion Vfib is associated with: history of MI, aspirin and b-blocker use, Vfib before PCI, left main CAD, inferior MI, symptom-to-balloon time <360 minutes, maximal ST-segment elevation in a single lead >300 μV, and sum of ST-segment deviations in all leads >1,500 μV.

The sum of ST-segment deviations in all leads >1500 μV was an independent predictor of reperfusion Vfib.

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Sx: pain to lateral arm, worse with overhead activity and sleeping/lying on arm

Anatomy: Pain generating structures include the rotator cuff, subacromial bursa, labrum and biceps tendon.

http://www.ortho-md.com/images/proceduresImg/SHOULDER2.jpg

Testing: Neer and Hawking tests

https://www.youtube.com/watch?v=U8-yLHQ_JaM

https://www.youtube.com/watch?v=OYK5qL2om-c

Done indepedently, Hawkings is more sensitive, however best to combine both tests.

Imaging: not indicated

Tx: rest, ice, physical therapy (modalities), subacromial steroid injection

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Methemoglobin (MetHb) is produce when Fe+2 in heme is oxidized to Fe+3 under oxidative stress (caused by mediation and chemicals). MetHb does not bind to oxygen and thus decrease RBC’s O2 carrying capacity.

Among medication, overdose of local anesthesia - benzocaine, dapsone, and phenazopyridine are often implicated. (Table 1)

Think about methemoglobinemia in presence of low pulse oximetry (~85%) with lack of response to supplemental oxygen, cyanosis, dyspnea, etc. (see Table 2 – signs and symptoms of MetHb) in patients who are taking or overdosed on medication listed in Table 1.

Diagnosis: CO-oximetry detects toxin-induced hemoglobinopathies, including COHb and MetHb.

Treatment: Methylene blue (1 mg/kg over 5 min) in symptomatic patients or MetHb level > 25%. Resolution of methemoglobinemia should be noted in 30 – 60 min.

G6PD deficiency: Prevalence in the U.S. is 4-7% with highest prevalence in African American population (11%). Methylene blue causes hemolytic anemia in patients with G6PD deficiency within 24 hours of administration. However, G6PD status is often unknown in ED patients.  When caring for patients with known G6PD deficiency and methemoglobinemia, providers must carefully consider the risk and benefit of treating MetHb (including severity of poisoning/MetHb) with methylene blue.

Table 1. Causes of MetHb

Table 2. Signs and symptoms

Background:

While diarrhea in adults can be inconvenient and briefly debilitating, in children it can be fatal.  Globally, diarrheal diseases are the second leading cause of death for children under five.

• Approximately 760,000 children under five die each year from diarrhea
  • Kills 2,200 children daily- more than AIDS, malaria and measles combined
• Most of the diarrhea can be prevented
  • Safe drinking water
  • Adequate sanitation and hygiene
• Diarrhea is also a leading cause of malnutrition

Clinical types of Diarrhea (with common infectious causes):

• Acute watery diarrhea lasting hours or days (e.g. rotavirus, norovirus, Vibrio cholerae)
• Acute bloody diarrhea, a.k.a. dysentery (e.g. Entamoeba histolytica, Shigella, Salmonella, Campylobacter, E. coli)
• Persistent diarrhea lasting longer than 14 days (e.g. parasites, C. difficile)

Clinical assessment:

• Early dehydration- no signs or symptoms
• Moderate dehydration
  • Thirst
  • Irritability/tiredness/lightheadedness
  • Dry mucous membranes/decreased tears
  • Decreased urine output/dark (concentrated) urine
  • Sunken eyes
  • Decreased capillary refill (2-4 sec)*
  • Decreased skin turgor*
  • Increased respiratory rate*
• Severe dehydration
  • Decreased mental status
  • Shock (rapid heart rate, low blood pressure)
  • Minimal or no urine output
  • Very sunken eyes/no tears
  • Parched/cracked mucous membranes
  • Marked decreased capillary refill (> 4 sec)*
  • Skin tenting*
  • Markedly increased respiratory rate*

*Best indicators of hydration status

Next week: Prevention and Treatment

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Advances in Catheter-Directed Therapy for Acute PE - The PERFECT Registry

Earlier this month, initial results from the multicenter PERFECT registry (Pulmonary Embolism Response to Fragmentation, Embolectomy, and Catheter Thrombolysis) were released. In this study, 101 consecutive patients with massive or submassive PE were prospectively enrolled to receive early catheter-directed therapy.

Inclusion criteria:

• Massive or submassive PE
• Presented within 14 days of symptoms
• Had CT evidence of proximal filling defect (main or lobar pulmonary artery)
• Age > 18 years old
• Had no contraindications to therapeutic anticoagulation
• PE not related to tumor thrombus

Therapy provided:

• Submassive PE: Low-dose (0.5 - 1.0 mg/hr of urokinase) infusion directly into clot
• Massive PE: catheter-directed mechanical or pharmacomechanical thrombectomy followed by low-dose thrombolytic therapy used for submassive PE patients.

Outcomes: Clinical success (stabilization of hemodynamics, improvement in pulmonary hypertension and/or right heart strain, and survival to discharge) was achieved in 86% of patients with massive PE and 97% of patients with submassive PE. There were no major procedure-related complications or major bleeding events.

Bottom Line: In patients with massive or submassive pulmonary embolism, there is growing evidence that early catheter-directed therapy may become first-line therapy for selected patients.

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Question

5 year-old with no past medical history, complains of a limp and mild left knee pain. No history of trauma. Physical exam is significant for a low-grade fever and is otherwise normal. What’s the diagnosis?

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Tensor Fascia Latae (Iliotibial Band) Pain Syndrome:

Some patients will complain of hip and back pain and can have multiple visits before somebody considers Tensor Fascia Latae Pain Syndrome AKA Iliotibial Band Syndrome.

The tensor fascia latae helps with thigh flexion at the hip, abduction, and medial rotation; and stabilizes the knee laterally

When this muscle/fascia gets tight and overcontracted it will lead to dysfunction of the gluteus and rectus femoralis muscles leading to increased hip pain due to abnormal movement of the joint.

Patients often complain of increased pain with running, especially downhill and exam is notable for local tenderness (approx. 2cm above lateral joint line) & occasional swelling over the distal lateral thigh.

Most patients respond to conservative treatment involving NSAIDs, stretching of the iliotibial band, physical therapy, strengthening of the gluteus medius, and altering their running regimens.

Lice are spread through direct contact as they crawl. Indirect contact (through brushes or hats) is less likely. One study showed that live lice were found in only 4% of infested volunteers pillowcases.

During an initial infestation, lice can reside on the head for up to 4 to 6 weeks before becoming symptomatic. Therefore, when lice are detected at school, there is no need to send the child home (or to the ED). Children also do not need to be kept out of school while receiving treatment.

Bonus: First line treatment is 1% Permethrin applied on day 0 and 9. The patient should wash their hair first with a non conditioned shampoo, apply Permethrin for 10 minutes and then rinse.

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Dabigatran is an orally administered, potent, direct thrombin inhibitor approved for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation, and for the treatment and secondary prevention of venous thromboembolism.

Several pharmacokinectic studies have suggested that dabigatran possesses a number of ideal properties for expedited removal via extracorporeal methods.  Dabigatran has low oral bioavailability (3-7%) and is predominantly cleared (80%) by the kidneys.  It is not significantly protein bound, low-to-moderate steady state volume of distribution, and has a low molecular weight.  All of these attributes make it a candidate for extracorporeal removal.  Low protein binding may suggest redistribution into the plasma post extracorporeal removal.  

Dabigatran is a substrate for the multidrug efflux transporter P-glycoprotein.  Administration of the drug with potent P-glycoprotein inhibitors (ketoconazole, verapamil, amiodarone, quinidine) may significantly increase risk of toxicity, i.e. bleeding.

Most of the current evidence is based on case reports/case series where HD was the primary mode of removal.  

Caution: Redistribution effect in plasma dabigatran concentration was also observed in several cases within 20 min to 12 hours post cessation of renal replacement therapy.   Other limitations include:

1) Hemodynamic instability such as hypotension that may make initiation of extracoporeal removal difficult

2) Availability of indicators demonstrating effectiveness of extracorporeal removal 

3) Amount of time needed to prepare patient to receive extracorporeal therapy

4) Use of extracorporeal removal as a treatment modality has not been prospectively evaluated

Bottom line: Extracorporeal removal may be an option for patients in the setting of life-threatening bleeding but with consideration of several limitations and should not preclude or delay use of other supplemental hemostatic therapies.

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Are We Using the Glasgow Coma Scale Reliably?

• The Glasgow Coma Scale (GCS), first described in 1974, has been a tool used worldwide to assess and communicate the consciousness of patients with traumatic brain injury (TBI).
• There have been reports of variations in which GCS is assessed, such as differences in technique used to elicit pain and how confounding factors such as intubation are reported.
• Reith et al. conducted an international survey of 613 health care practitioners on their methodology of GCS assessment, reporting of GCS, and attitudes toward its current use in daily practice.
  • Participants included nurses, intensivists, anesthesiologists, emergency physicians, and neurosurgeons
• Some variations in applications, methodology, and reporting from the survey include:

• This survey suggests that there is a lack of standardization of GCS assessment and reporting which affects its reliability as an assessment and communication tool
• A free educational tool has been developed (http://www.glasgowcomascale.org) to provide a standardized approach to the use of GCS

Bottom line: There are variations in the application, assessment, and reporting of the GCS.  A standardized approach is needed for it to be a reliable assessment and communication tool.

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There is little debate that ultrasound-guided central lines are safer, faster, and more reliable compared to a landmark technique; there is some debate, however, as to whether the short axis (SA) or long axis (LA) approach is the best (see clips below).

The referenced study compared the SA and the LA technique for both the internal jugular (IJ) and subclavian (SC) venous approach. The authors measured number of skin breaks, number of needle redirections, and time to cannulation for each method.

This study demonstrated that the LA technique for subclavian placement had fewer redirections, decreased cannulation time, and fewer posterior wall punctures as compared to the SA. With respect to the IJ approach, the LA was also associated with fewer redirections than the SA view.

Bottom line: Consider the long-axis technique the next time you place an ultrasound guided central line.

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Question

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Ischemic ECG Findings: Significance of the U-wave

The U-wave is a small deflection immediately following the T-wave, commonly with the same polarity as the T-wave and most prominently seen in precordial leads V2–V3.

Prominent U-waves are most often seen with bradycardia and hypokalemia, but can also be secondary to other electrolyte imbalances and medications.

Typically, T- and U-wave polarities are concordant; discordant U-waves have been identified several hours prior to other ECG changes in acute myocardial infarction.

Some studies note that exercise induced U-wave inversion is highly predictive of CAD; negative U -waves in the precordial leads during exercise had a higher specificity (88% vs. 70%) & positive predictive value (77% vs. 61%) for ischemia than ST-depression.

Reinig et al. 2005 showed that negative concordance of T- and U-waves have poor prognosis & is quite specific for ischemia.

·      ECG’s were divided into 3 groups:

o   Type 1 T-U discordance (negative T waves + positive U waves)

o   Type 2 T-U discordance (positive T waves + negative U waves)

o   Negative T-U concordance (both T & U waves negative)

* Significantly higher rate of CAD (88% vs. 58%) (P-value <. 0001) in the negative T-U concordance group 

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Posterior Shoulder Dislocations are uncommon (strong supporting structures vs. anterior)

But commonly missed by physicians

Mechanism: Direct blow anterior shoulder/FOOSH with shoulder internally rotated and ADDucted)

May also see with seizure/electric shock (tetanic contraction)

Clinical findings subtle

Shoulder held in ADDuction and internal rotation. Patient unable to externally rotate arm from this position. If habitus allows, anterior shoulder depression/posterior fullness.

Radiology: Decreased overlap between humeral head and glenoid fossa. Proximal humerus fixed in internal rotation looks like a light bulb on a stick.

Y view will show subtle posterior displacement of humeral head (not as dramatic as is in anterior dislocations!)

http://cdn.lifeinthefastlane.com/wp-content/uploads/2009/06/posterior_shoulder_dislocation_005.jpg

http://eorif.com/Shoulderarm/Images/Shoulder-dislocationP1.jpg

Background

In addition to the down regulation of GABA receptors in chronic ethanol users, there is an upregulation in NMDA receptor subtypes. Although the pathophysiology is much more complex, when ethanol abstinence occurs, there is a shortage of GABA-mediated CNS inhibition and a surplus of glutamate-mediated CNS excitation. If GABA agonists are the mainstay of treatment, why not also target the NMDA receptor? Enter ketamine.

The Data

Only one study exists and was published recently.

• Retrospective review of 23 adult patients administered ketamine specifically for management of AWS.
• Mean time to initiation of ketamine from first treatment of AWS, and total duration of therapy were 33.6 and 55.8 hours, respectively.
• Mean initial infusion dose and median total infusion rate were 0.21 and 0.20 mg/kg/h, respectively.
• No change in sedation or alcohol withdrawal scores within 6 hours of ketamine initiation.
• Median change in benzodiazepine requirements at 12 and 24 hours post-ketamine initiation were -40.0 and -13.3 mg, respectively.
• One documented adverse reaction of oversedation, requiring dose reduction.
• Authors concluded that ketamine appears to reduce benzodiazepine requirements and is well tolerated at low doses.

Application to Clinical Practice

While the dexmedetomidine studies should not be using reduction in benzodiazepine requirements as an endpoint, it may be acceptable for ketamine since it actually works on the underlying pathophysiology. More studies are needed but it's good to see we’re starting to look at it.

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