Vignette

History of Present Illness: The patient is a 29-year-old male who is admitted to the neuroscience intensive care unit with acute brain trauma. He was struck by a bus while waiting at the bus stop. The patient was unconscious when emergency medical services (EMS) arrived. Upon arrival to the emergency department, he is intubated. The patient has a Glasgow Coma Scale of 6, and his head CT reveals intracerebral contusions and swelling.

Past Medical History: Anxiety

Social History: Single; Social alcohol drinker; No history of smoking or recreational drug use

Current Medications: None

Allergies: Penicillin (Reaction: Hives)

Vital Signs: On Admission: Blood Pressure 116/62 mmHg, Heart Rate 70 bpm, Height 68 in (173 cm),

Lab Values: Na: 142 mEq/L (SI 142 mmol/L); K: 4 mEq/L (SI 4 mmol/L)l Cl: 103 mEq/L (SI 103 mmol/L)l HCO₃: 22 mEq/L (SI 22 mmol/L)l BUN: 18 mg/dL (SI 6.4 mmol/L)l SCr: 0.8 mg/dL (SI 70.7 micromol/L)l Glu: 110 mg/dL (SI 6.1 mmol/L)l Hgb: 13 g/dL (SI 130 g/L)l Hct: 36% (SI 0.36)l WBC: 10x10³/microL (SI 10x10⁹/L)l PLT: 180x10³/microL (SI 180x10⁹/L)l Alb: 4 g/dL (SI 40 g/L)l INR: 0.9

Procedure Data: External ventricular drain (EVD) placed on admission

Question 1

The team would like to use mannitol to decrease the patient’s intracranial pressure. Which is an adverse effect associated with mannitol administration?

1. Cardiotoxicity
2. Hepatotoxicity
3. Nephrotoxicity
4. Pulmonary toxicity

Answer:  3. Nephrotoxicity

Rationale: Mannitol has been associated with renal dysfunction. The renal dysfunction occurs more commonly in patients with concomitant nephrotoxic medications, sepsis, and pre-existing renal dysfunction. Monitoring to ensure the serum osmolality stays less than 320 mOsmol/L is one method to decrease the risk of nephrotoxicity

Citation: LexiComp Online® [Internet database]. Hudson, OH: Wolters Kluwer Clinical Drug Information Inc. Updated periodically. Accessed February 2, 2021.

Mannitol [package insert]. Schaumburg, IL. Fresenius Kabi USA, LLC, 2019.

Question 2

Your patient received one dose of mannitol about 6 hours ago, and the team is asking if an additional dose of mannitol can be administered. His measured serum osmolality is 320 mOsm/kg (SI Units: 320 mmol/kg) and the patient's calculated serum osmolality is 312 mOsm/kg (SI units: 312 mmol/kg) What is the osmolar gap ( mOsm/kg) in this patient?

1. -8
2. 1
3. 8
4. 316

Answer: 3. 8 mOsm/kg

Rationale: The osmolar gap is calculated by subtracting the calculated osmolality from the measured osmolality. For mannitol, the serum osmolarity and the osmolar gap can be used to determine when it is safe to redose to minimize risk of adverse effects.

Citation: García-Morales EJ, Cariappa R, Parvin CA, Scott MG, Diringer MN. Osmole gap in neurologic-neurosurgical intensive care unit: Its normal value, calculation, and relationship with mannitol serum concentrations. Crit Care Med. 2004;32(4):986-991. doi:10.1097/01.ccm.0000120057.04528.60

Question 3

Hyperosmolar, pain, and sedation regimens have been optimized and the team is starting a neuromuscular blockade via a continuous infusion for salvage therapy. Which is an adverse event associated with neuromuscular blockade in intensive care unit patients?

1. Hyperglycemia
2. Limb ischemia
3. Myocardial ischemia
4. Neuromuscular weakness

Answer:  4. Neuromuscular weakness

Rationale: There is a potential association between the use of neuromuscular blocking agents and the presence of neuromuscular weakness. As a result of the risk of the critical care acquired neuromuscular weakness with neuromuscular blocker use, neuromuscular blocker infusions are reserved for patients who have disease states that are refractory to preferred treatments. Hyperglycemia is a common ICU-related complicated from vasopressors and a stress response but it is not commonly associated with neuromuscular blockers. Limb ischemia and myocardial ischemia are risks associated more with vasopressor utilization.

Citation: De Jonghe B, Sharshar T, Lefaucheur JP, et al. Paresis acquired in the intensive care unit: a prospective multicenter study. JAMA. 2002;288(22):2859-2867. doi:10.1001/jama.288.22.2859

Price DR, Mikkelsen ME, Umscheid CA, Armstrong EJ. Neuromuscular blocking agents and neuromuscular dysfunction acquired in critical illness: A systematic review and meta-analysis. Crit Care Med. 2016;44(11):2070-2078. doi:10.1097/CCM.0000000000001839

LexiComp Online® [Internet database]. Hudson, OH: Wolters Kluwer Clinical Drug Information Inc. Updated periodically. Accessed February 2, 2021.

Question 4

The patient has an intracranial pressure (ICP) of 26 mmHg. Which medication intervention is most appropriate for this patient?

1. 0.9% sodium chloride at 500 mL administered once over 15-30 minutes
2. 23.4% hypertonic saline at 30 mL administered once over 5-15 minutes
3. Mannitol 15 g/kg administered once over 45 minutes
4. No intervention is needed

Answer: 2.       23.4% hypertonic saline at 30 mL administered once over 5-15 minutes

Rationale: The patient has an elevated intracranial pressure (ICP), so intervention is needed. 23.4% hypertonic saline is correct since it is a treatment that is appropriate to lower ICP and the dosing is appropriate for efficacy and safety. Sodium chloride 0.9% administration is incorrect because it is not hyperosmolar and will not cause a decrease in the ICP. Mannitol 15 g/kg is incorrect because the dosing is typically 0.5-1.5 g/kg so this is a 10-fold error in the recommended dose.

Citation: Carney N, Totten AM, O'Reilly C, et al. Guidelines for the management of severe traumatic brain injury, fourth edition. Neurosurgery. 2017;80(1):6-15. doi:10.1227/NEU.0000000000001432

LexiComp Online® [Internet database]. Hudson, OH: Wolters Kluwer Clinical Drug Information Inc. Updated periodically. Accessed February 2, 2021.

Question 5

The team requests a sedative with a fast onset and with a short duration of action for frequent neurologic checks. The patient is receiving fentanyl intravenous (IV) infusion at 200 mcg/hr. Blood pressure is 118/78 mmHg and heart rate is 80 bpm currently. Which is the best intravenous infusion sedation option to add to this patient's fentanyl infusion?

1. Hydromorphone
2. Lorazepam
3. Midazolam
4. Propofol.

Answer: 4. Propofol

Rationale: Propofol has a half-life of 1-2 minutes and a duration of action of 3-10 minutes. Propofol is preferred because it’s short duration of action allows for frequent neurologic assessments to be completed with minimal time off of sedation. Also, propofol’s fast onset of action allows for sedative effects to return quickly once restarting propofol after the neurocheck. The other options have longer onsets and durations of action. Midazolam has an onset of 2-5 minutes and a duration of 2 hours. Hydromorphone would be inappropriate as it would results in duplicate opioid therapy.

Citation:

Devlin JW, Skrobik Y, Gélinas C, et al. Clinical practice guidelines for the prevention and management of pain, agitation/sedation, delirium, immobility, and sleep disruption in adult patients in the ICU. Crit Care Med. 2018;46(9):e825-e873. doi:10.1097/CCM.0000000000003299

Barr J, Fraser GL, Puntillo K, et al. Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Crit Care Med. 2013;41(1):263-306. doi:10.1097/CCM.0b013e3182783b72

LexiComp Online® [Internet database]. Hudson, OH: Wolters Kluwer Clinical Drug Information Inc. Updated periodically. Accessed February 2, 2021.