🧮 剂量计算 · 第3课，共5课 · 6 min
每小时毫升数与每分钟滴数
mL per Hour and Drops per Minute
💧 输液泵需要每小时的mL数。重力输液器需要每分钟的滴数。输液袋标注1,000 mL在8小时内输完。两个公式都会在考试中出现，只要你不再把它们混淆，两者都很简单。
💧 The pump wants mL per hour. The gravity set wants drops per minute. The bag says 1,000 mL over 8 hours. Two formulas, both on the exam, both easy once you stop mixing them up.
💡 核心要点
输液泵：容量 ÷ 小时数。重力输液：容量 × 滴数系数 ÷ 分钟数。微滴管：gtt/min等于mL/hr。将滴数四舍五入为整数。
Pump: volume ÷ hours. Gravity: volume × drop factor ÷ minutes. Microdrip: gtt/min equals mL/hr. Round drops to a whole number.
🧠 为什么重要
对于输液泵：mL/hr = 总容量 ÷ 总小时数。1,000 mL在8小时内输完 = 125 mL/hr。如果时间以分钟计，则进行换算：250 mL在30分钟内输完 = 250 ÷ 0.5 = 500 mL/hr。对于重力输液器：gtt/min =（容量（mL）× 滴数系数（gtt/mL））÷ 时间（分钟）。滴数系数印在输液管上：大滴管输液器通常是10、15或20 gtt/mL；微滴管输液器是60 gtt/mL。1,000 mL在8小时内输完，使用15 gtt/mL输液器：（1,000 × 15）÷ 480 min = 31.25，四舍五入为31 gtt/min。使用微滴管输液器时，gtt/min始终等于mL/hr，因为60 gtt/mL ÷ 60 min相互抵消了。滴数始终四舍五入为整数。对于按剂量输注，先确认医嘱剂量是每小时的剂量，然后求出浓度（每mL的剂量），再用每小时剂量除以浓度得到mL/hr：heparin 25,000 units在250 mL中以1,000 units/hr输注，其浓度是100 units/mL，所以1,000 ÷ 100 = 10 mL/hr。
For a PUMP: mL/hr = total volume ÷ total hours. 1,000 mL over 8 hours = 125 mL/hr. If the time is in minutes, convert: 250 mL over 30 minutes = 250 ÷ 0.5 = 500 mL/hr. For a GRAVITY set: gtt/min = (volume in mL × drop factor in gtt/mL) ÷ time in minutes. The drop factor is printed on the tubing: macrodrip sets are commonly 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL. 1,000 mL over 8 hours with a 15 gtt/mL set: (1,000 × 15) ÷ 480 min = 31.25, rounded to 31 gtt/min. With a microdrip set, gtt/min always equals mL/hr, because 60 gtt/mL ÷ 60 min cancels. Always round drops to a whole number. For a DOSE-BASED infusion, make sure the ordered dose is per hour, then find the concentration (dose per mL) and divide the hourly dose by it to get mL/hr: heparin 25,000 units in 250 mL to run at 1,000 units/hr is 100 units/mL, so 1,000 ÷ 100 = 10 mL/hr.
🏥 真实场景
🔢 医嘱：500 mL生理盐水在4小时内通过重力输注，使用20 gtt/mL输液管。(500 × 20) ÷ 240 = 41.7，所以每分钟42滴。护士数一整分钟的滴数，并调节滚轮夹。在考试中，时间往往以小时给出，而公式需要分钟；这个换算就是陷阱。
🔢 Order: 500 mL of normal saline over 4 hours by gravity with 20 gtt/mL tubing. (500 × 20) ÷ 240 = 41.7, so 42 drops per minute. The nurse counts drops for a full minute and adjusts the roller clamp. On the exam, the time will often be given in hours and the formula needs minutes; that conversion is the trap.
📌 要点总结
- mL/hr = 容量 ÷ 小时数mL/hr = volume ÷ hours
- gtt/min =（mL × 滴数系数）÷ 分钟数gtt/min = (mL × drop factor) ÷ minutes
- 微滴管（60 gtt/mL）：每分钟滴数等于每小时mL数Microdrip (60 gtt/mL): drops per minute equals mL per hour
📖 本课术语
滴数系数 (Drop factor): 重力IV输液器每毫升输送的滴数，印在输液管包装上。
✅ 自我测试
医嘱开具1,200 mL D5W在10小时内通过输液泵输注，护士应设置什么速度？An order is for 1,200 mL of D5W to infuse over 10 hours by pump. What rate should the nurse set?
- 100 mL/hr
- 150 mL/hr
- 200 mL/hr
- 120 mL/hr
答案: D · 120 mL/hr
1,200 ÷ 10 = 120 mL/hr。100 mL/hr是一个常见的默认速度，但它在同样时间内只能输送1,000 mL，10小时后还剩200 mL未输注。
1,200 ÷ 10 = 120 mL/hr. 100 mL/hr is a familiar default rate, but it would deliver only 1,000 mL in 10 hours, leaving 200 mL still to infuse.
医嘱开具250 mL抗生素溶液在30分钟内通过重力输注，使用10 gtt/mL输液器，滴速是多少？An order is for 250 mL of an antibiotic solution to infuse over 30 minutes by gravity using a 10 gtt/mL set. What is the drip rate?
- 63 gtt/min
- 125 gtt/min
- 83 gtt/min
- 42 gtt/min
答案: C · 83 gtt/min
(250 × 10) ÷ 30 = 83.3，四舍五入为83 gtt/min。42 gtt/min是除以60分钟而不是30分钟得出的，仿佛输注持续了一整小时。
(250 × 10) ÷ 30 = 83.3, rounded to 83 gtt/min. 42 gtt/min comes from dividing by 60 minutes instead of 30, as if the infusion ran over a full hour.
Heparin 20,000 units在500 mL中，医嘱以1,200 units/hr输注，输液泵速度是多少？Heparin 20,000 units in 500 mL is ordered to infuse at 1,200 units/hr. What is the pump rate?
- 40 mL/hr
- 60 mL/hr
- 20 mL/hr
- 30 mL/hr
答案: D · 30 mL/hr
20,000 ÷ 500 = 40 units/mL；1,200 ÷ 40 = 30 mL/hr。40 mL/hr是将40 units/mL的浓度与输液泵速度混淆，并跳过了最后的除法。
20,000 ÷ 500 = 40 units/mL; 1,200 ÷ 40 = 30 mL/hr. 40 mL/hr confuses the concentration of 40 units/mL with the pump rate and skips the final division.
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