What is the best course of action for a patient presenting with vomiting, slight fever, hypotension, tachycardia, who is oriented to time, place, etc., and has not eaten?

Immediate Management of Acute Volume Depletion with Hemodynamic Instability

This patient requires immediate IV fluid resuscitation and identification of the underlying cause, as the combination of vomiting, hypotension, tachycardia, and fever indicates volume depletion with compensatory physiologic stress that demands urgent intervention. 1

Initial Assessment and Stabilization

Recognize the Clinical Picture

• The tachycardia (HR 114) with hypotension represents a compensatory sinus tachycardia secondary to volume depletion, not a primary arrhythmia requiring cardioversion. 1
• With heart rate <150 bpm and no ventricular dysfunction, the tachycardia is almost certainly secondary to the underlying condition (fever, dehydration, vomiting) rather than the primary cause of instability 1
• The preserved mental status (oriented to time, place, person) indicates the patient has not yet progressed to severe shock, but hypotension with tachycardia signals significant volume depletion requiring immediate action 1

Immediate Actions Required

• Establish IV access immediately and initiate aggressive fluid resuscitation with isotonic crystalloid (normal saline or lactated Ringer's). 1
• Attach continuous cardiac monitoring and pulse oximetry to assess for hypoxemia as a contributing cause of tachycardia 1
• Obtain vital signs including temperature measurement (core temperature preferred over oral), oxygen saturation, and orthostatic vital signs if safe 1, 2

Diagnostic Workup

Essential Laboratory Testing

• Obtain complete blood count, comprehensive metabolic panel (electrolytes, glucose, creatinine, liver function tests), lipase, and urinalysis to assess for dehydration severity, electrolyte abnormalities, and metabolic causes. 3, 4
• Check serum lactate and blood gas analysis if hypotension persists, as elevated lactate (≥4 mmol/L) with hypotension carries 46% mortality in sepsis 1
• Obtain blood cultures if septic shock is suspected or if results will change management 2

Critical Metabolic Abnormalities to Identify

• Assess for hypoglycemia, hypokalemia, hypochloremia, and metabolic alkalosis—all common with prolonged vomiting. 3
• Consider testing for hypercalcemia, thyroid function, and cortisol if initial workup is unrevealing 3, 4
• Urine drug screen may be warranted to assess for cannabis use, as Cannabis Hyperemesis Syndrome presents with cyclic vomiting and can cause significant volume depletion 3

Imaging Considerations

• Obtain chest X-ray to evaluate for pneumonia or other pulmonary causes of fever 2
• Consider abdominal imaging (CT or ultrasound) only if clinical suspicion exists for intra-abdominal pathology, obstruction, or abscess 4

Fluid Resuscitation Strategy

Initial Resuscitation Targets

• Administer 30 mL/kg of isotonic crystalloid within the first 3 hours for patients with hypotension or lactate ≥4 mmol/L. 1
• Target mean arterial pressure (MAP) ≥65 mmHg as the initial hemodynamic goal 1
• Monitor for improvement in heart rate, blood pressure, urine output, and mental status as markers of adequate resuscitation 1

Monitoring Response to Fluids

• Reassess vital signs every 15-30 minutes during active resuscitation 1
• A decrease in elevated heart rate with fluid administration is a useful marker of improving intravascular volume 1
• If hypotension persists despite adequate fluid resuscitation, consider septic shock and need for vasopressor support 1

Antiemetic Management

Initial Antiemetic Therapy

• Initiate dopamine receptor antagonists such as metoclopramide 10 mg IV every 6 hours or prochlorperazine 10 mg IV/IM every 6-8 hours, titrated to maximum benefit. 3
• Metoclopramide is particularly effective for gastric stasis and promotes gastric emptying 3
• Administer antiemetics on a scheduled basis rather than PRN, as prevention is easier than treating established vomiting 3

Second-Line Therapy

• Add ondansetron 8 mg IV if vomiting persists after initial dopamine antagonist therapy. 3, 5
• Ondansetron acts on different receptors (5-HT3) than dopamine antagonists, providing complementary antiemetic coverage 3
• Monitor for QTc prolongation when using ondansetron, especially with other QT-prolonging agents 3, 5

Critical Antiemetic Pitfall

• Never use antiemetics if mechanical bowel obstruction is suspected, as this can mask progressive ileus and gastric distension. 3, 5
• If abdominal distension, absent bowel sounds, or severe abdominal pain develops, obtain imaging before continuing antiemetics 3

Identifying Underlying Cause

Infectious Etiologies (Most Likely Given Fever)

• Gastroenteritis is the most common cause of acute vomiting with fever, but consider more serious infections including pneumonia, urinary tract infection, or intra-abdominal infection. 4, 2
• Fever may not always be present in true infection, especially in elderly or immunocompromised patients 2
• Temperature >38°C (101°F) on two measurements warrants contact with healthcare provider per sick day guidance 1

Severe Symptoms Requiring Immediate Escalation

• Vomiting >4 times in 12 hours or inability to keep fluids down requires immediate medical attention and possible hospitalization. 1
• Reduced level of consciousness, new confusion, systolic BP <80 mmHg, or drop of 20 mmHg in systolic BP are severe warning signs 1
• If symptoms do not resolve within 72 hours despite treatment, escalate care and consider alternative diagnoses 1

Electrolyte Correction

Specific Electrolyte Management

• Correct hypokalemia and hypomagnesemia aggressively, as these are common with vomiting and can cause cardiac arrhythmias. 3
• Address metabolic alkalosis by correcting volume depletion and potassium deficiency 3
• Monitor electrolytes daily until normalized 3

Disposition and Follow-Up

Criteria for Hospitalization

• Persistent hypotension despite 30 mL/kg fluid bolus 1
• Inability to tolerate oral fluids after initial treatment 1
• Severe electrolyte abnormalities requiring IV correction 3
• Suspected sepsis or serious underlying infection 1
• Altered mental status or signs of end-organ dysfunction 1

Outpatient Management (If Stabilized)

• Ensure patient can maintain oral fluid intake of at least 1.5 L/day with small, frequent meals. 3
• Prescribe scheduled antiemetics (not PRN) for 24-48 hours 3
• Provide clear return precautions: inability to keep fluids down, worsening symptoms, fever >38°C, dizziness/syncope, or no improvement within 72 hours 1
• Consider thiamin supplementation to prevent Wernicke's encephalopathy if vomiting has been prolonged 3

Common Pitfalls to Avoid

• Do not attribute tachycardia to anxiety or primary arrhythmia without first addressing volume depletion and fever. 1
• Do not delay fluid resuscitation while waiting for laboratory results 1
• Do not use oral temperature alone if concern for fever exists—obtain core temperature 2
• Do not assume viral gastroenteritis without considering serious bacterial infections, especially with hypotension 1, 2
• Monitor for extrapyramidal symptoms with dopamine antagonists and treat with diphenhydramine 50 mg IV if they develop 3