EM Quick Hits 25 Cerebral Venous Thrombosis, Diphenhydramine Alternatives, Abdominal Compartment Syndrome, Neonatal Constipation, Intubating Metabolic Acidosis

Topics in this EM Quick Hits podcast

Justin Morgenstern on when to consider cerebral venous thrombosis (00:53)

Maria Ivankovic on diphenhydramine alternatives (07:38)

Brit Long on abdominal compartment syndrome (13:13)

Sarah Reid on neonatal constipation  (19:37)

Anand Swaminathan on intubating metabolic acidosis (27:40)

Podcast: Play in new window | Download (Duration: 34:31 — 31.7MB)

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Podcast production, editing and sound design by Anton Helman; voice editing by Raymond Cho

Podcast content by Justin Morgenstern, Maria Ivankovic, Brit Long, Sarah Reid, Anand Swaminathan & Anton Helman 

Written summary & blog post by Graham Mazereeuw, edited by Anton Helman

Cite this podcast as: Helman, A. Morgenstern, J. Ivankovic, M. Long, B. Reid, S. Swaminathan, A. EM Quick Hits 25 – Cerebral Venous Thrombosis, Diphenhydramine Alternatives, Abdominal Compartment Syndrome, Neonatal Constipation, Intubating Metabolic Acidosis. Emergency Medicine Cases. January, 2021. https://emergencymedicinecases.com/em-quick-hits-january-2021/. Accessed [date].

When to Consider Cerebral Venous Thrombosis

Presentation is nonspecific and highly variable:

• Headache in nearly all patients (the only symptom in 25% of patients)
• Other features: focal neurological deficit (40%), seizure (40%), encephalitis (rarely)

Key demographics:

• Young (39 years old on average)
• Female (3x more commonly)
• Usually at least one thrombotic risk factor

Consider this diagnosis in 4 groups of patients:

Group 1: severe or prolonged headache without a clear cause and with at least one thrombotic risk factor

Group 2: thunderclap headache with a negative CT head

Group 3: severe headache with stroke symptoms or neurological findings not clearly mapping to a vascular territory

Group 4: intracranial hemorrhage without a classic bleeding pattern, particularly younger patients or those with thrombotic risk factors

-MR venogram is gold standard; contrast CT venogram has good sensitivity (95%)

-Treat the sequelae (ABCs, treat seizure, treat raised ICP)

-Specific treatment is anticoagulation (even if intracranial hemorrhage!) in consultation with neurology/hematology

-Full recovery = 80%; 30-day mortality = 5%

Bottom line: CVT is the DVT of the brain; be on high alert for CVT in patients with thrombotic risk factors and atypical headache or stroke symptoms.

Ep181 Cerebral Venous Thrombosis, Idiopathic Intracranial Hypertension, Giant Cell Arteritis and Peripartum Headaches

Episode 14 Part 2: Thunderclap Headache – Cerebral Venous Thrombosis and Cervical Artery Dissection

Diphenhydramine Alternatives

• First-generation antihistamines are “dirty drugs”: diphenhydramine and hydroxyzine have poor receptor selectivity, binding muscarinic, serotonergic, and alpha-adrenergic receptors, as well as cardiac potassium channels in addition to the H₁ histamine receptor
• First-generation antihistamines side effects:
  • CNS suppression, psychomotor impairment, delirium, coma, and death
  • QT prolongation and torsades de pointes
  • Recreational misuse (“Benadryl challenge” parties)
  • A therapeutic dose of diphenhydramine (50mg) can impair driving similarly to a 0.1% blood-alcohol level (4-5 alcoholic drinks in some people)!
• Second-generation antihistamines are generally safer: less likely to have drug-drug interactions, faster onset, much less sedating
• A second-generation antihistamine is a reasonable (perhaps superior) alternative for post-anaphylaxis urticaria without the potential side-effects of diphenhydramine

Bottom line: First-generation antihistamines such as diphenhydramine and hydroxyzine have multiple side effects and can be replaced by second-generation antihistamines for allergy and post-anaphylaxis urticaria.

Abdominal Compartment Syndrome

• Abdominal compartment syndrome is a potentially deadly condition caused by increased pressure within the abdominal compartment and is most often diagnosed in the ICU
• Abdominal compartment syndrome is defined by intra-abdominal pressure (IAP) > 20 mm Hg with organ dysfunction
• Suspect abdominal compartment syndrome in penetrating abdominal trauma and post open abdominal surgery with abdominal pain out of proportion, abdominal distension and shortness of breath/increase work of breathing; note that these findings are not accurate for diagnosis, making the clinical diagnosis challenging
• History, physical examination, labs and imaging may suggest the diagnosis, but they should not be used to exclude it
• Diagnosis: IAP measurement, typically through measuring bladder pressure with a Foley catheter
• Management: increase abdominal wall compliance, evacuate gastrointestinal contents, avoid excessive fluid resuscitation, drain intraperitoneal contents, and decompressive laparotomy in select cases; patients typically require admission to an ICU

Procedural video measuring intra-abdominal pressure

Bottom line: Consider abdominal compartment syndrome in critically ill patients with multi-organ failure; measure intra-abdominal pressure through the bladder using a Foley catheter.

Neonatal “Constipation” Red Flags, DDx and ED Management

• Poor stooling in a newborn is common and often triaged as “constipation”; however, it is most often a result of breastfeeding not being fully established

Management:

• Fractionated bilirubin if concerns about feeding, hydration or weight loss; use bilitool.org to determine the need for phototherapy or exchange transfusion
• Abdominal X-ray with two views if concern for obstruction (bilious vomiting, abdominal distension) if you don’t have other imaging modalities available
• IV fluid resuscitation with strong consideration of full septic workup and empiric antibiotics in any newborn who is lethargic, dehydrated, appears unwell 

Disposition:

• Home if: baby is well and there are no red flags; parents are comfortable with increasing feeds, stimulating baby to stay awake during feeds, seeking close follow up with primary care (in next 1-2 days for weight check)
• Admission to paediatrics if: baby is significantly dehydrated, weight loss ³ 10%, concern about underlying abnormality on exam, or social concerns
• General surgery consultation if: concerned about obstruction, Hirschsprung disease, or anal abnormalities

Bottom line: “constipation” in a newborn is likely attributable to ineffective breastfeeding, but be sure to assess for red flags and rule out serious illness

Intubating Patients with Metabolic Acidosis: Apnea Time and Minute Ventilation

• Patients with metabolic acidosis employ a compensatory respiratory alkalosis, which they rely on for pH management
• Apnea induced during intubation impairs this compensation, which can lead to peri-intubation cardiac arrest
• If intubation is necessary, minimize apneic time and ensure adequate minute ventilation
• Approach

1. 1. Resuscitate the underlying problem/consider NaHCO₃ IV drip
   2. Start NIPPV, which can support the patient and estimate minute ventilation (which you will need when setting the ventilator)
   3. Consider an awake intubation to maintain ventilation; use ketamine if unable to topically anesthetize the airway (consider KOBI); if RSI needed, use succinylcholine to minimize time of paralysis

• It is critical to maintain pre-intubation minute ventilation in order to maintain pH balance
  • If unable to do this on a ventilator, provide pressure support while the patient breathes on their own, or bag-mask ventilate them to the minute-ventilation required

Bottom line: Avoid intubation if you can in the severely acidotic patient; if you must intubate, be sure to minimize apnea time and support minute ventilation to pre-intubation levels.

None of the authors have any conflicts of interest to declare