How should I set the infusion rate for a midazolam drip prepared with 15 mg (5 mg/1 mL) diluted in 97 mL of normal saline to deliver 2.5 mg per hour to a 70‑kg adult?

Midazolam Infusion Rate Calculation

To deliver 2.5 mg/hr from your prepared solution of 15 mg midazolam in 100 mL total volume (15 mg in 97 mL PNSS + 3 mL midazolam), set your infusion pump to 16.7 mL/hr.

Calculation Breakdown

Your prepared concentration is:

• 15 mg midazolam in 100 mL total volume = 0.15 mg/mL

To achieve 2.5 mg/hr:

• 2.5 mg/hr ÷ 0.15 mg/mL = 16.7 mL/hr (or approximately 17 mL/hr if your pump doesn't allow decimal settings)

Weight-Based Dosing Context for 70 kg Patient

Your target rate of 2.5 mg/hr equals 0.036 mg/kg/hr for this 70 kg patient, which falls within the recommended ICU sedation range of 0.02-0.1 mg/kg/hr (1-7 mg/hr initially) 1, 2.

Critical Safety Considerations Before Starting

Midazolam should not be first-line for ICU sedation. Propofol or dexmedetomidine are strongly preferred as they result in significantly fewer delirium days (54% vs 76.6%, P<0.001), fewer ventilator days (3.7 vs 5.6 days, P=0.01), and improved mortality outcomes 1.

Mandatory Dose Reductions

• Reduce dose by at least 20% if concurrent opioid use due to synergistic respiratory depression risk 1
• Reduce dose by at least 20% in hepatic or renal impairment due to decreased clearance 1
• Reduce dose by 30% if patient is on H2-receptor antagonists (e.g., ranitidine, famotidine) due to increased bioavailability 1
• Reduce dose by 50% in patients ≥60 years or ASA III-IV status 1

Essential Monitoring Requirements

• Continuous pulse oximetry throughout infusion 1
• Blood pressure and respiratory rate assessment every 1-2 hours initially 1
• Have flumazenil immediately available for reversal of life-threatening respiratory depression, though note it may precipitate seizures if used in seizure patients 3, 4
• Respiratory depression can occur up to 30 minutes after dose changes 1

Titration Protocol

• For breakthrough agitation: Give bolus doses equal to 1-2 times the hourly infusion rate (2.5-5 mg) every 5 minutes as needed 1
• If patient requires 2 bolus doses within 1 hour: Double the infusion rate to 5 mg/hr (33.3 mL/hr with your concentration) 1
• Decrease infusion rate by 10-25% every few hours to find minimum effective rate and minimize accumulation 2

Common Pitfalls to Avoid

• Inadequate time between dose adjustments - allow at least 5 minutes for peak effect after bolus doses 3
• Failure to reduce doses when combining with opioids - this combination caused hypoxemia in 92% of volunteers versus 50% with opioid alone 1
• Not considering alternative agents first - dexmedetomidine and propofol have superior outcomes for ICU sedation 1
• Inadequate monitoring duration - continue monitoring for at least 30 minutes after any dose change 1