A 62-year-old patient recovering from craniotomy for tumor resection has an external ventricular drain (EVD) in place. On postoperative day 5, he develops a fever of 38.8 °C and subtle mental status changes. Initial CSF analysis from the EVD shows WBC 25 cells/mm³ (80% neutrophils), protein 80 mg/dL, and glucose 45 mg/dL (serum glucose 120 mg/dL). Empiric broad-spectrum antibiotics were started. Over the next 48 hours, his fever resolves and mental status returns to baseline. Repeat CSF analysis shows WBC 10 cells/mm³ (60% neutrophils), protein 60 mg/dL, and glucose 55 mg/dL (serum glucose 110 mg/dL). The CSF Gram stain remains negative and cultures are still pending. Which of the following is the most appropriate management at this time?

A 45-year-old man is admitted to the ICU and is mechanically ventilated for altered mental status. He presented with 3 days of progressive confusion, fever, severe headache, and a new generalized tonic–clonic seizure. He is receiving a propofol infusion, and a central venous catheter is in place. Initial labs show WBC 12,000/mm3 and CRP 80 mg/L. Lumbar puncture reveals CSF with 150 WBCs/mL (90% lymphocytes), protein 0.8 g/L, and glucose 60 mg/dL (serum glucose 100 mg/dL). Given these findings, which statement best interprets the diagnostic significance of the CSF profile?

A 62-year-old man is admitted to the ICU for septic shock requiring vasopressor support and mechanical ventilation. He presented with altered mental status, fever (39.5°C), and new generalized tonic-clonic seizures. Laboratory evaluation shows serum creatinine 1.1 mg/dL (eGFR >60 mL/min/1.73 m2). Initial cerebrospinal fluid (CSF) analysis reveals 25 cells/µL (80% lymphocytes; normal <5 cells/µL), protein 65 mg/dL (normal 15–45 mg/dL), and glucose 70 mg/dL (serum glucose 120 mg/dL; normal CSF/serum ratio ~0.6). CSF Gram stain is negative. Head CT demonstrates subtle temporal lobe hypodensities. Empiric vancomycin and ceftriaxone were started, but his neurologic status remains unchanged, and he experienced another seizure overnight. Given the high suspicion for herpes simplex virus encephalitis, which of the following therapies should be initiated first as part of his initial management plan?

A 62-year-old man is 5 days post-craniotomy for glioblastoma resection and remains on minimal ventilator support with a propofol infusion. He develops a subtle drop in Glasgow Coma Scale from 10 to 8, intermittent low-grade fevers to 38.1°C, and mild diffuse headache. His peripheral WBC count has risen from 9,000/mm³ post-operatively to 13,500/mm³. CSF obtained by lumbar puncture shows 15 WBCs/mm³ (80% lymphocytes), glucose 60 mg/dL, and protein 80 mg/dL. Recognizing that post-neurosurgical inflammation can obscure infection, which principle is most critical when evaluating this patient for a healthcare-associated CNS infection?

A 62-year-old man presents with fever (39.5 °C), severe headache, acute altered mental status, and a witnessed generalized tonic-clonic seizure. Cerebrospinal fluid analysis shows 15 leukocytes/µL (80% lymphocytes), protein 65 mg/dL, glucose 70 mg/dL (serum glucose 120 mg/dL), and a negative Gram stain. Empiric ceftriaxone and acyclovir are initiated. Which of the following is the MOST critical element of the monitoring plan to assess efficacy of this empiric therapy?

A 65-year-old man presents with 2 days of fever (38.8°C), headache, altered mental status, and new-onset generalized seizures. A noncontrast head CT is normal. Lumbar puncture reveals CSF with 8 WBC/µL (80% lymphocytes), protein 65 mg/dL, and glucose 60 mg/dL (serum glucose 100 mg/dL). Which of the following best describes the diagnostic utility of these CSF findings for infectious encephalitis?

A 62-year-old man is in the ICU 10 days after craniotomy for brain tumor resection. He is receiving synchronized intermittent mandatory ventilation and has both an external ventricular drain and a central venous catheter in place. Over the past 24 hours, he has developed intermittent confusion, worsening lethargy, and a new headache unrelieved by acetaminophen. Vital signs are temperature 37.8°C, heart rate 88 bpm, and blood pressure 122/78 mmHg. Neurologic exam shows no nuchal rigidity or photophobia. A lumbar puncture reveals cerebrospinal fluid with WBC 2 cells/mm³ (100% lymphocytes), protein 35 mg/dL, and glucose 65 mg/dL (serum glucose 100 mg/dL). Which of the following findings most strongly suggests a healthcare-associated central nervous system infection in this patient?

A 62-year-old patient was admitted with suspected central nervous system infection presenting as fever, headache, and altered mental status. Despite empirical antimicrobial therapy, no pathogen was identified, and after a week the patient’s neurological status has fully recovered. The patient is being discharged to a skilled nursing facility for rehabilitation. Given ongoing diagnostic uncertainty, which of the following is the most critical component of the discharge process to ensure a safe and effective transition of care?

A 65-year-old, 70 kg male is 3 days into empiric treatment for healthcare-associated ventriculitis following craniotomy. He is receiving vancomycin 1 g IV every 12 hours (15 mg/kg/dose) and meropenem 2 g IV every 8 hours via a right internal jugular central line. His baseline serum creatinine was 0.9 mg/dL. Today, his creatinine has risen to 2.1 mg/dL, and urine output has decreased to 0.3 mL/kg/hr over the past 6 hours. A vancomycin trough level drawn just before his last dose returned at 32 mcg/mL. He is hemodynamically stable without signs of hypovolemia or hypotension, and his mental status is unchanged. Which of the following is the most appropriate immediate intervention?

A 45-year-old comatose patient presents to the intensive care unit with fever (39.5°C), acute altered mental status, and generalized tonic–clonic seizures. Despite an initial lorazepam dose, she remains unresponsive with intermittent myoclonic jerks. Head CT is unremarkable and lumbar puncture is pending. Which intervention is the highest priority to prevent secondary brain injury (additional neuronal damage due to impaired cerebral perfusion and dysregulated intracranial pressure) in this patient?