Emergency Medical Minute

Contributor: Aaron Lessen MD

Educational Pearls:

Why is airway management more difficult in obesity?

• Larger body habitus causes the chest to be above the head when the patient is lying supine, creating difficult angles for intubation.
• Reduced Functional Residual Capacity (FRC) causes these patients to deoxygenate much more quickly, reducing the amount of time during which the intubation can take place.

What special considerations need to be made?

• Positioning. The auditory canal and sternal notch should be aligned in a horizontal plane. Do this by stacking blankets to lift the neck and head. Also, try to make the head itself parallel to the ceiling.
• Pre-oxygenation. Use Bi-level Positive Airway Pressure (BiPAP) with Positive End Expiratory Pressure (PEEP) or a Bag-Valve-Mask (BVM) with a PEEP valve. PEEP helps prevent alveoli from collapsing after every breath and improves oxygenation.
• Dosing of paralytics. Succinylcholine is dosed on total body weight so the dose will be much larger for the obese patient. Rocuronium is dosed on ideal body weight, but adjusted body weight may also be used in obese cases.

References

1. De Jong A, Wrigge H, Hedenstierna G, Gattinoni L, Chiumello D, Frat JP, Ball L, Schetz M, Pickkers P, Jaber S. How to ventilate obese patients in the ICU. Intensive Care Med. 2020 Dec;46(12):2423-2435. doi: 10.1007/s00134-020-06286-x. Epub 2020 Oct 23. PMID: 33095284; PMCID: PMC7582031.
2. Langeron O, Birenbaum A, Le Saché F, Raux M. Airway management in obese patient. Minerva Anestesiol. 2014 Mar;80(3):382-92. Epub 2013 Oct 14. PMID: 24122033.
3. Sharma S, Arora L. Anesthesia for the Morbidly Obese Patient. Anesthesiol Clin. 2020 Mar;38(1):197-212. doi: 10.1016/j.anclin.2019.10.008. Epub 2020 Jan 2. PMID: 32008653.
4. Singer BD, Corbridge TC. Basic invasive mechanical ventilation. South Med J. 2009 Dec;102(12):1238-45. doi: 10.1097/SMJ.0b013e3181bfac4f. PMID: 20016432.

Summarized by Jeffrey Olson, MS2 | Edited by Jorge Chalit, OMSII

Contributor: Nick Tsipis MD

Educational Pearls:

• The scaphoid bone is the most proximal carpal bone just distal to the radius
• Fractures of the scaphoid bone are sometimes missed by plain X-rays
• A 2020 review found a 21.8% incidence of missed scaphoid fractures later diagnosed by advanced imaging modalities
• Only MRI has a sensitivity above 90% for diagnosing scaphoid fractures
• Sensitivity of plain-film radiography is low unless it is a displaced fracture
• Physical examination techniques fail to definitively rule out scaphoid fractures
• A 2023 systematic review assessed the sensitivity and specificity of several common physical exam maneuvers:
• Tenderness of the anatomical snuffbox has a sensitivity of 92.1% and specificity of 48.4%; i.e. absence reduces the likelihood of an occult scaphoid fracture but does not rule it out
• Another common physical exam maneuver is pain with ulnar deviation, which carries a sensitivity of 55.2% and specificity of 76.4%.
• Elicitation of pain with supination against resistance demonstrated a sensitivity of 100% and specificity of 97.9% in the study, so the authors recommend externally validating this method
• Patients should be counseled on the importance of follow-up given that a fracture may not show up on imaging unless an MRI or repeat XR is done

References

1. Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020;09(01):081-089. doi:10.1055/s-0039-1693147

2. Coventry L, Oldrini I, Dean B, Novak A, Duckworth A, Metcalfe D. Which clinical features best predict occult scaphoid fractures? A systematic review of diagnostic test accuracy studies. Emerg Med J. 2023;40(8):576 LP - 582. doi:10.1136/emermed-2023-213119

Summarized by Jorge Chalit, OMSII | Edited by Meg Joyce & Jorge Chalit, OMSII

Contributor: Aaron Lessen MD

Educational Pearls:

• A recent randomized controlled trial compared ondansetron 8 mg IV with droperidol 2.5 mg IV for the treatment of nausea & vomiting in the emergency department.
• Overall, droperidol and ondansetron had similar primary outcomes in acute nausea control
• Symptom improvement in 93% of patients receiving droperidol vs. 87% receiving ondansetron (P = 0.362)
• Secondary measures were, however, statistically significantly different between groups
• Patients needed fewer rescue/additional antiemetics in the droperidol group (16%) compared with the ondansetron group (37%); p = 0.016
• Similarly, more patients in the droperidol group reported they achieved the desired effect of the medication (85% vs. 63%; p = 0.006)
• Patients receiving droperidol did experience increased drowsiness
• 40% in the droperidol group vs. 11% in the ondansetron group
• The trial did not assess the length of stay in the ED after administering medications, which is a potential avenue for future research.

References

1. Philpott L, Clemensen E, Lau GT. Droperidol versus ondansetron for nausea treatment within the emergency department. EMA - Emerg Med Australas. 2023;(December 2022):605-611. doi:10.1111/1742-6723.14174

Summarized & Edited by Jorge Chalit, OMSII

Contributor: Travis Barlock MD

Education Pearls:

• The Cushing Reflex is a physiologic response to elevated intracranial pressure (ICP)
• Cushing’s Triad: widened pulse pressure (systolic hypertension), bradycardia, and irregular respirations
• Increased ICP results from systolic hypertension, which causes a parasympathetic reflex to drop heart rate, leading to Cushing’s Triad.
• The Cushing Reflex is a sign of herniation
• Treatment includes:
• Hypertonic saline is comparable to mannitol and preferable in patients with hypovolemia or hyponatremia
• Give 250-500mL of 3%NaCl
• 20% Mannitol - given at a dose of 0.5-1 g/kg
• Each additional dose of 0.1 g/kg reduces ICP by 1 mm Hg
• 23.4% hypertonic saline is more often given in the neuro ICU
• 8.4% Sodium bicarbonate lowers ICP for 6 hours without causing metabolic acidosis
• Non-pharmacological interventions:
• Raise the head of the bed to 30-45 degrees
• Remove the c-collar to improve blood flow to the head
• Hyperventilation induces hypocapnia, which will vasoconsrict the cerebral arterioles
• You hyperventilate on the way to the OR. Otherwise, maintain normocapnia.

References

1. Alnemari AM, Krafcik BM, Mansour TR, Gaudin D. A Comparison of Pharmacologic Therapeutic Agents Used for the Reduction of Intracranial Pressure After Traumatic Brain Injury. World Neurosurg. 2017;106:509-528. doi:10.1016/j.wneu.2017.07.009
2. Bourdeaux C, Brown J. Sodium bicarbonate lowers intracranial pressure after traumatic brain injury. Neurocrit Care. 2010;13(1):24-28. doi:10.1007/s12028-010-9368-8
3. Dinallo S, Waseem M. Cushing Reflex. [Updated 2023 Mar 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549801/
4. Godoy DA, Seifi A, Garza D, Lubillo-Montenegro S, Murillo-Cabezas F. Hyperventilation therapy for control of posttraumatic intracranial hypertension. Front Neurol. 2017;8(JUL):1-13. doi:10.3389/fneur.2017.00250

Summarized by Jorge Chalit, OMSII | Edited by Meg Joyce & Jorge Chalit, OMSII

Contributor: Aaron Lessen MD

Educational Pearls:

What is measured in an ABG/VBG?

• Blood values for oxygen tension (pO2), carbon dioxide tension (pCO2), acidity (pH), oxyhemoglobin saturation, and bicarbonate (HCO3) in either arterial or venous blood
• Other tests can measure methemoglobin, carboxyhemoglobin, hemoglobin levels, base excess, and lactate

What are they used for?

• Identification of ventilation/acid-base disturbances. For example: if a patient is in septic shock, oxyhemoglobin saturation can be used to guide resuscitation efforts (early goal- directed therapy)

What's the difference between an ABG and VBG?

• One of the main differences is how the blood samples are collected. Venous blood gas is normally collected from existing venous access such as a central venous catheter. Arterial blood gases must be drawn from an artery, such as the radial artery.
• Arterial blood draws can be difficult, painful, and contraindicated in many situations.
• ABGs have traditionally provided more accurate measurements for assessing oxygenation, ventilation, and acid-base status.
• However, several studies have found that VBGs can still be used to accurately assess pH, pCO2, HCO3, lactate, sodium, potassium, chloride, ionized calcium, blood urea nitrogen, base excess, and arterial/alveolar oxygen ratio. This is supported by a recent study in 2023 in the International Journal of Emergency Medicine which specifically studied patients with hypotension and use of VBGs for resuscitation guidance.

Are there other non-invasive methods that can be used to fill in the gaps to avoid ordering an ABG?

• Oxygenation can be measured by pulse oximetry
• Arterial carbon dioxide tension can be estimated by end-tidal carbon dioxide (PetCO2)
• Mixed venous blood gases are another alternative for patients who already have a pulmonary artery catheter

References

1. Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, Peterson E, Tomlanovich M; Early Goal-Directed Therapy Collaborative Group. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001 Nov 8;345(19):1368-77. doi: 10.1056/NEJMoa010307. PMID: 11794169.
2. Prasad H, Vempalli N, Agrawal N, Ajun UN, Salam A, Subhra Datta S, Singhal A, Ranjan N, Shabeeba Sherin PP, Sundareshan G. Correlation and agreement between arterial and venous blood gas analysis in patients with hypotension-an emergency department-based cross-sectional study. Int J Emerg Med. 2023 Mar 10;16(1):18. doi: 10.1186/s12245-023-00486-0. PMID: 36899297; PMCID: PMC9999648.

Summarized by Jeffrey Olson, MS2 | Edited by Jorge Chalit, OMSII