SIMV (Synchronized intermittent mandatory ventilation)

• A common mode of ventilation that all pratitioners should be familiar with
• It provides a minimum number of fully assisted breaths synchronized with patient respiratory effort
• Patient or time triggered
• Flow limited
• Volume cycled
• Any additional breaths are unassisted and determined by patient effort
• SIMV=AC when heavily sedated
• The idea is exercise the patients lungs but this can lead to increased work of breathing and fatigue, and prolong extubation when used

Hyperoxia in the Critically Ill

• Oxygen is liberally administered to many critically ill patients, thereby exposing them to supranormal arterial oxygen levels.
• Hyperoxia results in the formation of reactive oxygen species, which adversely affect the pulmonary, vascular, cnetral nervous, and immune systems.
• Though the optimal P_aO₂ remains unknown, recent evidence indicates that hyperoxia is associated with increased mortality in post-cardiac arrest, CVA, acute coronary syndrome, and traumatic brain injury patients.
• Take Home Point: Carefully titrate oxygen to the lowest tolerable level to meet the patient's needs.

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Your ESLD patient is hypotensive with a tense abdomen, and he needs a paracentesis!

--ALWAYS use ultrasound to localize a fluid pocket [Fig 1]! Take the time to use color Doppler to look for underlying abdominal wall varices [Fig 2]. Cirrhotic patients frequently have abnormal abdominal wall vasculature [1-2].

--Hemorrhage from paracentesis is exceedingly rare, and reversal of mild coagulopathy probably isn't that important [3-4].

--In hypotensive patients, consider placement of a small pigtail catheter for slow, continuous drainage (e.g. 8.3F pericardiocentesis catheter) instead of large-volume paracentesis. Non-tunneled catheter infection risk goes up after 72h [5].

--Albumin replacement improves mortality and incidence of renal failure in patients with SBP or other infection [6-7].

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Attachments

• 1509011640_Figure_1_--_Ascites_pocket.jpg (78 Kb)
• 1509011640_Figure_2_--_Color_over_abd_wall_varices.jpg (89 Kb)

The RV is a low-pressure chamber that doesn’t tolerate acute increases in pulmonary pressures (e.g., ARDS, pulmonary embolism, etc.); acute increases can lead to RV dysfunction / failure

Managing RV dysfunction requires a three-pronged approach:

• Optimize preload – give small fluid boluses (e.g., 250cc) but not too much, because too much can worsen RV function. Use ultrasound to determine volume status
• Optimize RV function – Consider starting inotropes (e.g., dobutamine) for better RV contractility and concurrently start pulmonary vasodilators (e.g., inhaled nitric oxide); also minimize hypoxemia and hypercarbia
• Prevent systemic hypotension – hypotension reduces coronary perfusion that leads to RV ischemia and dysfunction; use norepinephrine to keep blood pressure >65
• Bottom-line: Don't under-estimate the importance of the RV when resuscitating your patients 

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Pressure Regulated Volume Control (PRVC)

Here are some basic pearls about PRVC Ventilation

• Form of Assist Control (AC) ventilation: patient initiated or ventilator intiated
• Constant pressure through inspiration
• Decelerating inspiratory flow pattern
• Ventilator adjusts pressure breath to breath based on patient’s airway resistance and compliance
• Not recommended for asthma or COPD
• Set: RR, tidal volume, upper pressure limit, oxygen level, I:E ratio (can start at 1:2), PEEP

Benefits: minimum PIP, guaranteed tidal volume, patient can trigger more breaths, improved oxygenation, breath by breath changes 

Is It Really ARDS?

• Recent literature suggests that the incidence of ARDS in intubated ED patients may be as high as 10%.
• The Berlin Definition of ARDS includes the acute onset of bliateral opacities (CXR or chest CT) that is not fully explained by pulmonary edema or fluid overload.
• Emergency physicians and Intensivists are well versed in lung-protective ventilator settings for patients with ARDS.
• However, several diseases can appear simliar to ARDS and may require different ventilator strategies and treatments.
• In the absence of clinical risk factors for ARDS (e.g., sepsis, trauma), consider the following in your differential:
  • Idiopathic pulmonary fibrosis
  • Interstitial pneumonitis
  • Granulomatosis with polyangitis (Wegener's)
  • Diffuse alveolar hemorrhage
  • Goodpasture's syndrome

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Ever forget all the things that make up MUDPILES in your AG acidosis differential?

Instead, consider the less-complicated mnemonic "KILR"!

K Ketoacidosis (diabetic, alcoholic, starvation)

I Ingestion (salicylate, acetaminophen, methanol, ethylene glycol, CO, CN, iron, INH)

L Lactic acidosis (infection, hemorrhage, hypoperfusion, alcohol, metformin)

R Renal (uremia)

Once you rule out the KLR causes, begin to consider ingestion or a tox source as your source. Remember that many of the listed ingestions can also cause a lactic acidosis.

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It's July, that means new doctors are learning to do central-lines...here's a quick video with some quick pearls on how to do that. Enjoy!

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Care of Drowning Patients in the ED

• 500,000 worldwide deaths per year/10 per day in US on average
• Main goal of resuscitation is to reverse hypoxemia: endotracheal intubation, mouth-to-mouth, BVM depending on setting
• In water resuscitation can be considered (mouth-to-mouth only) while the patient is being actively rescued
• CPR with Airway emphasis- five rescue breaths, 30 compressions, then 2 breaths/30 compressions until the airway can be secured
• Turning the patient over and performing abdominal thrusts or back blows is not helpful
• ARDSnet protocol is generally used when intubated
• No steroids or prophylactic antibiotics are indicated
• Consider trauma (CT head and C-spine precautions based on history/exam)
• Warm up your patient as needed--assume hypothermia on presentation
• Can consider therapeutic hypothermia after ROSC and when rewarmed---no clear benefit here

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Blood Pressure Management in Severe Preeclampsia

• Severe preeclampsia (preeclampsia + at least one severe complication) accounts for almost 40% of deaths in obstetrical ICU admissions.
• Systolic arterial hypertension is the most important predictor of morbidity in patients with severe preeclampsia.
• First-line agents to reduce blood pressure in severe preeclampsia are nicardipine and labetalol.
• Hydralazine is no longer recommended as first-line therapy.
• Magnesium is used as an anticonvulsant and should not be considered an antihypertensive.

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With a new academic year starting, it is important to review some details on central lines

Complications of central lines (TLC-Triple lumen catheter)

• Pneumothorax (more common with subclavian)
• Arterial puncture (more common with femoral)
• Catheter malposition
• Subcutaneous hematoma
• Hemothorax
• Catheter related infection (historically more with femoral)
• Catheter induced thrombosis
• Arrhythmia (usually from guidewire insertion)
• Venous air embolism (avoid with Trendelenburg position)
• Bleeding

Avoiding infections: hand hygiene, chlorhexidine skin antisepsis, maximal barrier precautions, remove unnecessary lines, full gown and glove w/ mask and sterile technique.

Catheter position: 16-18cm for Right sided and 18-20 cm for Left sided. But can vary based on height, neck length, and catheter insertion site. Approximate length based on these factors.

Flow rates: Remember that putting in a central line does not necessarily improve your flow rates in resuscitation

16 G IV: 220 ml/min

Cordis/introducer sheath: 126 ml/min

18 G IV: 105 ml/min

16G distal port TLC: 69 ml/min

Ports (Can vary with type of catheter)

1. Distal exit port (16G)

2. Middle port (18G)

3. Proximal port (18G)

Arterial puncture: hold pressure for 5 mins and evaluate for hematoma formation (harder for subclavian approach)

Arterial cannulation: Has decreased due to ultrasound use but if you do cannulate an arterial site, don’t panic. Don’t remove the line. You can check a blood gas or arterial pulse waveform to confirm placement.  Call vascular surgery for open removal and repair or endovascular repair. You could potentially remove a femoral arterial line and hold pressure but seek vascular advice regarding possible closure devices to use after removal.

Renal Resuscitation using Renal Interlobar Artery Doppler (RIAD)

Shocked patient…. check! Adequate volume resuscitation…. check!  Vasopressors.… check! Mean arterial pressure (MAP) > 65 mmHg….. check!  Adequate urine output…. Wait, why isn’t my patient making urine?

As we begin to understand more about shock, hemodynamics, and the importance of perfusion over the usual macrocirculatory goals (MAP > 65), finding ways to assess regional blood flow is critical.  A recent study examined the effect of fluid administration on renal perfusion using renal interlobar artery Doppler (RIAD) to assess the interlobar resistive index (RI).  See how to perform a RIAD here.

They also recorded the fluid challenge’s effect on the traditional hemodynamic measurements of MAP and pulse pressure (PP) then observed the patient’s urine output (as a clinical marker of perfusion).  The authors reported 3 key findings:
 

1. In the hemodynamically impaired patient, a fluid challenge results in reduced intrarenal vasoconstriction (a reduction in the RI).
2. In the hemodynamically impaired patient, changes in RI are more effective than changes in MAP or PP in predicting an increase in urine output after a fluid challenge.
3. Using RI to guide fluid therapy may be limited by small changes and technical limitations.

Bottom Line: The use of ultrasound to determine intrarenal hemodynamics is an interesting strategy to guide renal resuscitation in the shocked patient.  There is mixed data on the use of RIAD, however this study could explain the findings of SEPSISPAM and also addresses the growing concern that traditional hemodynamic goals may be inadequate resuscitation targets.

References

1. Moussa MD, Scolletta S, Fagnoul D, et al. Effects of fluid administration on renal perfusion in critically ill patients. Crit Care. 2015;19(1):250.
2. Asfar P, Meziani F, Hamel JF, et al. High versus low blood-pressure target in patients with septic shock. N Engl J Med. 2014;370(17):1583-93.

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Intraosseous (IO) placement is a rapid and reliable method for obtaining venous access in critically ill patients; previous studies demonstrated that everything from vasopressors to packed RBCs can be infused through it.

This prospective observational study compared the first-pass success rate and time to successful placement of IO versus landmark-based (i.e., not ultrasound guided) central-line placement (femoral or subclavian access) during medical emergencies (e.g., cardiac arrest) in an inpatient population.

The first pass success rate for IO was found to be significantly higher than the landmark technique (90% vs. 38%) and placement was significantly faster for IOs (1.2 vs. 10.7 minutes).

Despite the fact that this study did not directly compare IO to ultrasound guided line placement, this study demonstrates that IO is a rapid and effective means to obtain central access during patients with emergent medical conditions.

Bottom-line: Consider placing an IO line when rapid central access is necessary.

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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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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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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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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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Safety of Thoracentesis

• Thoracentesis is routinely performed in both acute and non-acute patients while patients are admitted to the hospital for respiratory distress
• A recent 12 year cohort study of 9320 thoracenteses was published from Cedars-Sinai Hospital
• The clinicians that perform these procedures are well experienced
• The most common complications include pneumothorax, re-expansion pulmonary edema, and bleeding

Results after 24 hours of followup post-procedure

• 0.61% of iatrogenic pneumothoraces
• 0.01% rate of re-expansion pulmonary edema
• 0.18% of bleeding episodes

Other interesting points:

• Pneumothorax was associated with removing >1500 mL of fluid and more than one needle pass
• Ultrasound was routinely used
• A safety-tipped needle/catheter was used
• Fluid was removed by manual hand pumping (not vacuum bottles)
• CXR only done post-procedure if patients were symptomatic
• No blood products were given for low platelets or thrombocytopenia

Bottom line: Use your ultrasound to direct your tap and dont take out more than 1500 mL routinely

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SIRS and Severe Sepsis Screening

• Sepsis remains one of the most common critical illnesses managed by emergency medicine and critical care physicians.
• Many EDs and ICUs have screening protocols for early detection of the patient with sepsis. Most protocols use the systemic inflammatory response syndrome (SIRS) as a central component of early identification.
• A recent study stresses caution when simply using the SIRS criteria to screen for severe sepsis:
  • Retrospective review of the ANZICS Adult Database
  • Divided patients into SIRS-positive ( 2 SIRS criteria with at least 1 organ failure) and SIRS-negative ( < 2 SIRS criteria with at least 1 organ failure)
  • 109,663 patients
  • 12% of patients diagnosed with severe sepsis or at least 1 organ failure had < 2 SIRS criteria at admission.
  • Mortality for the SIRS-negative cohort remained relatively high at 16.1%
• Take Home Point
  • Using the SIRS criteria to screen patients for severe sepsis will miss 1 out of every 8 patients with infection and organ dysfunction.

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Updates in the Management of Large Hemispheric Infarction

Large hemispheric infarctions (LHI) are estimated to occur in 2-8% of all hospitalized ischemic strokes and 10 15% of all MCA territory infarcts. LHI carry high rates of morbidity and mortality, in fact, if left untreated associated cerebral edema can rapidly progress to transtentorial herniation and death in 40 80% of patients.

Recognized risk factors for progressive cerebral edema include:

• NIH stroke scale > 20 in dominant hemispheric infarct
• NIH stroke scale > 15 in nondominant hemispheric infarct
• Rapid decline in level of consciousness (LOC) indicates effect on contralateral hemisphere (due to ipsilateral swelling)

Evidence based medical strategies for LHI include:

• Positioning: Elevation of the head of the bed (HOB) > 30 degrees
• Glucose control: 140 180 mg/dL (hyperglycemia associated with increased ICP and progression to hemorrhagic conversion)
• Blood pressure control: 15% reduction MAP over 24 hours if BP exceeds 220/120 (likely best accomplished with nicardipine infusion to avoid overcorrection)
• Osmotic therapy: In the deteriorating patient, consider hypertonic saline (23%) with goal Na of 160 mEq/L or mannitol with goal plasma osmolality of 320 mOsm/kg.
• Adjunctive therapies: Prevent fever and hypercapnea

Prophylactic hemicraniectomy

• Consider early neurosurgical consultation for patients with LHI as newer evidence suggests prophylactic hemicraniectomy may improve survival if performed within 24 48 hours.

Bottom Line: Early recognition of large hemispheric stroke is critical as it is associated with a high rate of morbidity and mortality. Aggressive medical management and early neurosurgical involvement may improve outcomes.

References

1. Zha AM, Sari M, Torbey MT. Recommendations for management of large hemispheric infarction. Curr Opin Crit Care. 2015;21(2):91-8.

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