What is the differential diagnosis for a 98-year-old lady presenting with temperature dysregulation (feeling hot and cold) and nausea?

Differential Diagnosis for a 98-Year-Old Woman with Temperature Dysregulation and Nausea

In a 98-year-old woman presenting with feelings of hot and cold alternating with nausea, the most critical immediate considerations are sepsis/infection, medication-induced temperature dysregulation, heat-related illness, and gastrointestinal pathology—with infection being the most life-threatening and requiring urgent evaluation.

Life-Threatening Conditions Requiring Immediate Evaluation

Sepsis and Severe Infection

• Elderly patients may present with atypical fever patterns or hypothermia during serious infections, making temperature dysregulation a red flag for sepsis 1
• Look specifically for: altered mental status (confusion, lethargy), leukopenia (WBC <4.5 x 10⁹ cells/L), thrombocytopenia (platelets <150 x 10⁹ cells/L), and elevated liver enzymes 1
• Blood cultures, urinalysis, and complete blood count must be obtained immediately before initiating empiric antibiotics 1
• Common pitfall: Dismissing vague symptoms as "gastroenteritis" in elderly patients when sepsis is evolving 1

Heat-Related Illness

• Heat exhaustion or early heat stroke can present with nausea, temperature dysregulation, and altered mental status 1
• Critical distinguishing features: recent heat exposure, inability to cool down, progression to confusion or decreased responsiveness 1
• If core temperature approaches 39-40°C with CNS changes, this becomes a medical emergency requiring immediate active cooling 1

Medication-Induced Temperature Dysregulation

Antipsychotic-Induced Hypothermia

• Antipsychotics (particularly those with pronounced 5HT2 and D2 antagonism) can cause life-threatening hypothermia in elderly patients 2, 3
• Aripiprazole, benperidol, levomepromazine, and zuclopenthixole have been specifically associated with recurrent hypothermia episodes 2, 3
• Look for: core temperature <35.5°C, bradycardia, hypotension, and somnolence 2, 3
• If hypothermia is present, immediately discontinue the offending antipsychotic 3

Neuroleptic Malignant Syndrome (NMS)

• NMS presents with hyperthermia, muscle rigidity, altered consciousness, and autonomic instability (irregular pulse/BP, tachycardia, diaphoresis) 4
• This is a rare but potentially fatal complication of metoclopramide and other antipsychotics 4
• Immediate discontinuation of all antipsychotics is mandatory if NMS is suspected 4

Gastrointestinal and Metabolic Causes

Cyclic Vomiting Syndrome (CVS)

• CVS can present with prodromal symptoms including feeling hot or cold, nausea, mental fog, anxiety, and diaphoresis 1
• Constitutional symptoms (feeling hot/cold, flushing, shakiness) occur in most patients during prodromal and emetic phases 1
• However, CVS typically affects younger adults and would be unusual as a new diagnosis at age 98 1

Gastroenteritis and Foodborne Illness

• Viral gastroenteritis can cause nausea with subjective temperature dysregulation 1
• Critical distinction: If symptoms persist beyond 24-48 hours or worsen, escalate evaluation for serious infection 1

Neurologic Causes

Central Thermoregulatory Dysfunction

• Lesions in hypothalamic or brainstem areas controlling temperature regulation can cause dysregulation 5, 6
• Consider: stroke, intracranial hemorrhage, or mass lesion if acute onset 5
• Associated findings would include other focal neurologic deficits 5

Motion Sickness and Vestibular Dysfunction

• Nausea associated with thermoregulatory changes (hypothermia, vasodilation) can occur with vestibular dysfunction 7
• Less likely in a bedridden or immobile elderly patient 7

Immediate Diagnostic Approach

Obtain these tests urgently:

• Core temperature measurement (rectal or bladder preferred over oral in elderly) 1
• Complete blood count with differential (looking for leukopenia, thrombocytopenia, left shift) 1
• Comprehensive metabolic panel including liver enzymes 1
• Blood cultures before antibiotics 1
• Urinalysis and urine culture 1
• Procalcitonin if probability of bacterial infection is low-to-intermediate 1

Critical historical elements to elicit:

• Complete medication list (especially antipsychotics, antiemetics, anticholinergics) 4, 2, 3
• Recent heat exposure or inability to maintain comfortable temperature 1
• Presence of altered mental status, confusion, or lethargy 1
• Pattern of symptoms: episodic vs. continuous, triggers, duration 1
• Recent tick exposure, pet illness, or outdoor activities 1

Management Priorities

If infection suspected with high probability:

• Do not delay antibiotics waiting for procalcitonin results 1
• Initiate broad-spectrum coverage (e.g., ceftriaxone) immediately after cultures obtained 8

If hypothermia present (<35.5°C):

• Discontinue any antipsychotic medications immediately 3
• Passive rewarming with blankets and warm environment 1
• Active rewarming if resources available 1

If hyperthermia with altered mental status:

• Activate emergency response and initiate immediate cooling 1
• Target core temperature <39°C 1

Common pitfall: Attributing vague symptoms to "old age" or "viral illness" in a 98-year-old when life-threatening infection or medication toxicity is evolving 1, 2