Questions of the Week for 8/8/2023

Author: Christian Gerhart

How does the location and approach of blade insertion differ when performing video vs. direct laryngoscopy with a standard geometry Mac blade? 

  • When performing VIDEO laryngoscopy, the blade should be inserted and advanced in the midline towards the hyoeppiglottic ligament. When performing DIRECT laryngoscopy, the blader should be inserted on the right side of the mouth and the tongue swept to the side, then advanced toward the midline to engage the hyoepiglottic ligament. This helps maximize direct visualization of the vocal cords.

What are the advantages of using a Mac 3 vs. Mac 4 for intubation?

  • There is some observational data that using a Mac 3 has higher first pass success than a Mac 41 (this study only examined direct laryngoscopy). Using a Mac 3 allows for easier following of landmarks and makes it less likely you will insert the blade too far. It has the advantage of more subtle adjustments to optimize view. Mac 4 blades have the advantage that it will nearly always be long enough to reach the vallecula in taller patients or can be used more effectively as Miller blade (direct lifting of the epiglottis rather than engaging vallecula) in patients with a floppy epiglottis. However, it can be more challenging to take a stepwise approach with a Mac 4 and sometimes tube passage can be more challenging given its larger profile compared to a Mac 3.

A patient on peritoneal dialysis presents with abdominal pain. You suspect peritonitis and want to obtain peritoneal fluid for analysis. How is this done and what is the criteria for diagnosis? 

  • At our institution we need to consult nephrology to obtain peritoneal dialysate cultures. Some patients may be able to provide dialysate themselves if the institution does not have the resources to assist with this process in the ED. Typically, a liter of fluid is instilled and allowed to dwell for at least two hours, at which point it can be sent for cell count with differential, gram stain and culture. If the dialysate is not allowed to dwell long enough the cell counts can be falsely low. A cell count of WBC > 100/µL with > 50% PMN is indicative of peritonitis (this is different than SBP in liver disease!). The official criteria from the International Society of Peritoneal Dialysis is below:

    1) Clinical feautres of peritonitis (abdominal pain and/or cloudy dialysis effluent)

    2) Dialysis effluent white cell count >100uL after a dwell time of at least two hours with >50% PMNs

    3) Positive dialysis effluent culture

    Nephrology may recommend intraperitoneal antibiotics. If the patient is systemically ill, then IV antibiotics are probably appropriate.

    *Always be sure to rule out causes of secondary peritonitis such as appendicitis or other intra-abdominal infections! Surgical abdomens do not respond well to misdiagnosis.

Describe the difference between a type and screen and a type and cross (called “Prepare Unit” when you order it in Epic). Which patients should have a type and CROSS ordered?

  • The blood bank does ABO typing, Rh typing, and an antibody screen when a type and screen is ordered. The antibody screen looks specifically for non-ABO antibodies, particularly anti-Rh, anti-Kell, anti-Duffy. The presence of non-ABO antibodies makes getting compatible blood much more difficult.

    The type and cross is very dependent on the type and screen. There are three main types of crossmatches. Electronic, immediate spin, and full. Today most crossmatching is done electronically or by an “immediate spin”, which are both rapid (within a few seconds to a few minutes). Immediate spin simply checks for ABO compatibility and is valid as long we already know there are no antibodies. It does not assess for compatibility regarding non-ABO antibodies. The electronic crossmatch requires two separate type and screen results and for the patient to not have antibodies. This is even faster than the immediate spin. Therefore, for many of our patients, the crossmatch is instant and sending a type and cross does not expedite blood administration of typed blood for our patients but does take those units out of circulation for other patients, which can be costly and many of these units simply expire and are wasted.

    However, there are a few scenarios where computer or immediate spin crossmatching does NOT work. For these specific scenarios, a full crossmatch, which generally at least two hours, is required. These are cases where it is advised to cross blood early since there may be a significant delay for the blood bank to prepare it.

    1) Patients with clinically significant antibodies

    - In these patients, it can be very helpful to crossmatch blood since it can take many hours to find and crossmatch blood.

    2) ABO discrepancy on electronic crossmatch

    - this is a blood bank thing and it is hard for us to know ahead of time if this will happen

    You can always call the bloodbank and ask them how long it will take for them to find crossmatched blood. If they can perform an electronic cross or immediate spin, you may not need to cross units ahead of time. If not, then consider crossing units early for your bleeding patient.

A patient presents to the ED with alcohol withdrawal. You want to treat them with phenobarbital. What are some key contraindications to this medication?

  • Advanced cirrhosis, possibility of hepatic encephalopathy, and pregnancy are important contraindications. We should have caution with phenobarbital in patients who have the possibility of multiple neurological problems since it is a very long-lasting medicine and if overdosed can lead to prolonged sedation. Be careful about giving a full loading dose to anyone who is on phenobarbital chronically or who has already received a large amount of benzodiazepines.

A patient presents to the ED after lower extremity trauma. Based on the history, you suspect that they had a tibiofemoral knee dislocation that self-reduced in the field. The patient has no other injuries. On your examination they have palpable, symmetric DP and PT pulses bilaterally. You perform and ABI and it is 0.95. How should this patient be managed? 

  • The patient should at least be admitted to observation and serial neurovascular checks. It would also be reasonable to obtain a CTA of the lower extremity, though observation is also acceptable if the patient’s neurovascular exam and ABIs are normal. Tibiofemoral knee dislocations have a very high risk of neurovascular compromise and clinical signs of injury may be delayed. Therefore, ALL patients with a proven or suspected knee dislocation should at least be admitted for monitoring as the risk of ischemia is high even with an initially reassuring exam. Patients with an abnormal neurovascular exam need emergent vascular surgery consultation and CTA.

A dialysis patient presents with pulsatile, bright red blood from their left upper extremity fistula. Describe your approach to managing this.

  • Direct pressure is a good first step. At dialysis centers they have clamps, though you likely will not have access to this in the ED. You can try Surgicel and/or Quikclot on the site to slow bleeding. If these do not work, vascular surgery should be called. Consider anticoagulation reversal and repletion of platelets if severe thrombocytopenia is present. If the patient received heparin with a recent dialysis session, protamine can be considered. Additionally, consider desmopressin since patients with end stage renal disease have baseline platelet dysfunction. A figure of eight suture or a proximal tourniquet can be trialed if the bleeding is life-threatening though this places the fistula at risk of damage and carries a risk for distal limb ischemia. Remember that once you get control, the fistula patency needs to be assessed. If the bleeding was minor and resolved with direct pressure, documenting a palpable thrill may be all that is necessary. However, if you had to suture or tourniquet the extremity, then they likley need a fistulogram ultrasound and a trial of the site for functionality.

A patient receives a transfusion of packed red blood cells for an acute GI bleed. Shortly afterwards, they become hypotensive, tachycardic, and tachypneic. On exam they have bilateral expiratory wheezing and an urticarial rash. What is the clinical syndrome and which individuals are at higher risk for this?

  • This is an example of anaphylaxis from blood transfusion. This can occur with any type of blood product. It is seen more frequently in patients with IgA deficiency as they can develop anti-IgA antibodies that lead to anaphylaxis. This is managed the same way as any anaphylaxis case with addressing the ABCs, and giving epinephrine. The main difference is that you need to STOP THE TRANSFUSION.

References: 

1) Godet T, De Jong A, Garin C, et al. Impact of Macintosh blade size on endotracheal intubation success in intensive care units: a retrospective multicenter observational MacSize-ICU study. Intensive Care Med. 2022;48(9):1176-1184. doi:10.1007/s00134-022-06832-9. 

2) Li PK-T, Chow KM, Cho Y, et al. ISPD peritonitis guideline recommendations: 2022 update on prevention and treatment. Peritoneal Dialysis International. 2022;42(2):110-153. doi:10.1177/08968608221080586 

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