Questions of the Week for 12/5/2023

Authors: Christian Gerhart, Erica Blustein, Robbie Paulsen, Sarah Flores

You diagnose your patient with a corneal abrasion related to contact-lens wear and decide to prescribe a topical antibiotic to prevent the development of bacterial ulcerative keratitis. Which organism do you want to ensure your antibiotic has coverage against? 

• Answer

  Pseudomonas aeruginosa. Contact lens wear associated with up to 42% culture-proven corneal infections. Often presenting with thick yellow-green or blue-green mucopurulent tenacious exudate, this organism is capable of destroying the cornea within 6 to 12 hours; however permanent damage associated with keratitis is rare. Example antibiotic prophylaxis options include ciprofloxacin (Ciloxan) 0.3% drops.

You see a patient in the ED having a miscarriage at 8 weeks of pregnancy.  You see an open cervix on US, so you consult OB.  They recommend discharge with medications to help with passage of POC at home.  What potential complications are they at risk for if products do not completely pass? Related to this, what specific ED return precautions should you be giving to these patients? 

• Answer

  These patients are at most risk for 1- significant hemorrhage and 2- significant infection. If left untreated, both of these carry high morbidity and mortality. Specifically related to infection, if severe this could require hysterectomy which is a particularly significant complication in a child bearing age female. All women should therefore be counseled about significant bleeding risks, and to return if they are bleeding through >1 pad per hour, or any symptoms of symptomatic anemia. If they are still bleeding and they have not seen passage of products within 36-48 hours, they should re-present to the ED, but in particular if they have foul smelling vaginal discharge, significant abdominal pain or fevers.

You are taking care of a pregnant patient who presents for vaginal bleeding.  She is a G4P1, LMP about 7 weeks ago.  She has history of pregnancy loss and prior right sided ectopic pregnancy, s/p surgical evacuation and right fallopian tube reconstruction.  She continues to desire pregnancy and is receiving fertility treatments with a high-risk OB.  Her US is pictured below. Are you concerned for an abnormal pregnancy? What on this US points to an abnormal pregnancy?  

• Answer

  This ultrasound has free fluid in the pelvis and a right sided circular extrauterine structure concerning for an ectopic pregnancy. Though this is a limited slice, there also does not appear to be a yolk sac or fetal pole present in the uterus, which should immediately raise your concern for an abnormal pregnancy.

A 28-year-old G1P0 woman at 24 weeks gestation presents to the emergency department with painless, bright red vaginal bleeding for one day. She has not had contractions and has felt normal fetal movement. Her current pregnancy has been uncomplicated, but she has been missing her obstetrics appointments. In the ED, her vital signs are BP 110/80, HR 80, RR 18, and oxygen saturation 100% on room air. What is the most appropriate next step in the management of this patient?

• Answer

  This patient should undergo a pelvic ultrasound to elucidate the cause for her bleeding. In this case her bleeding is painless and the primary diagnoses to be considered are placenta previa, vasa previa or placental abruption (can also present without pain). If the patient has not had a confirmed IUP by this time, then an ectopic pregnancy should also be considered. IV access, a CBC and type and screen should be obtained. Remember that placental abruption is a clinical diagnosis and the main purpose of the pelvic ultrasound is to assess for placenta previa or vasa previa rather than diagnose abruption, though a retroplacental hematoma may be seen. These cases should be discussed with OB.

A 30-year-old woman who is 37 weeks pregnant presents with bilateral lower extremity edema and blurry vision. Her BP is 175/110. She is placed on a magnesium sulfate infusion given concern for pre-eclampsia. What is usually the first sign of magnesium toxicity?

• Answer

  Hyporeflexia. Loss of deep tendon reflexes usually occurs at a serum magnesium level of approximately 8-10 mg/dL and is usually the first sign of supratherapeutic magnesium levels. The antidote to magnesium toxicity is calcium. This is usually reserved for patients with respiratory or cardiac symptoms, which can occur as levels approach 10-12 mg/dL. The reference range at our institution for the normal levels of magnesium is 1.4-2.5 mg/dL.For pre-eclamptic patients with normal renal function, a loading dose of 4-6 g IV is given followed by an infusions at 1-2 g/hr IV. The target range for these patients is between 5-8 mg/dL.

Tricyclic antidepressants exert their therapeutic effects by inhibiting presynaptic neurotransmitter uptake of serotonin and norepinephrine. Below are the additional six receptors that TCAs interact with. Name the effects that can be caused by each in toxicity.

Peripheral alpha-1 receptors

Peripheral muscarinic acetylcholine receptors

Cardiac Na+ channels

iKR channels

CNS GABA-A receptors

Histamine H1 receptors

• Answer

  Antagonism of peripheral alpha-1 receptors: hypotension; treat w/ fluids, consider phenylephrine or norepinephrine if refractory

  Antagonism of peripheral muscarinic acetylcholine receptors: tachycardia, delirium, mydriasis, dry mouth, urinary retention, fever; treated with benzodiazepines

  Antagonism of cardiac Na+ channels: wide QRS (i.e., > 100 ms) + R’ in aVR >/= 3 mm + R-ward deviation of terminal 40 ms of QRS complex (last small box); treated with sodium bicarbonate

  Antagonism of iKr channels: Prolongs QT, risk of Torsades de Pointe (TdP); treated with optimization of electrolytes, consideration of magnesium, avoidance of QTc-prolonging agents

  Antagonism of CNS GABA-A receptors: Seizures; treated with benzodiazepines

  Antagonism of histamine H1 receptors: Sedation; treated with supportive care

References

Stapleton F, Carnt N. Contact lens-related microbial keratitis: how have epidemiology and genetics helped us with pathogenesis and prophylaxis. Eye (Lond). 2012 Feb;26(2):185-93. doi: 10.1038/eye.2011.288. Epub 2011 Dec 2. PMID: 22134592; PMCID: PMC3272197.

Maier P, Betancor PK, Reinhard T. Contact Lens-Associated Keratitis-an Often Underestimated Risk. Dtsch Arztebl Int. 2022 Oct 7;119(40):669-674. doi: 10.3238/arztebl.m2022.0281. PMID: 35912449; PMCID: PMC9830382.

Okusanya BO, Oladapo OT, Long Q, et al. Clinical pharmacokinetic properties of magnesium sulphate in women with pre-eclampsia and eclampsia. BJOG. 2016;123(3):356-366. doi:10.1111/1471-0528.13753

Salinger DH, Mundle S, Regi A, et al. Magnesium sulphate for prevention of eclampsia: are intramuscular and intravenous regimens equivalent? A population pharmacokinetic study. BJOG. 2013;120(7):894-900. doi:10.1111/1471-0528.12222

Bruccoleri RE, Burns MM. A Literature Review of the Use of Sodium Bicarbonate for the Treatment of QRS Widening. J Med Toxicol. 2016;12(1):121-129. doi:10.1007/s13181-015-0483-y

Emamhadi M, Mostafazadeh B, Hassanijirdehi M. Tricyclic antidepressant poisoning treated by magnesium sulfate: a randomized, clinical trial. Drug Chem Toxicol. 2012;35(3):300-303. doi:10.3109/01480545.2011.614249

Salhanick S. Tricyclic antidepressant poisoning. UpToDate. https://www-uptodate-com.beckerproxy.wustl.edu/contents/tricyclic-antidepressant-poisoning?search=tricyclic%20&source=search_result&selectedTitle=3~144&usage_type=default&display_rank=2. Published June 24, 2022. Accessed Decem