一氧化二氮 (笑氣)
Nitrous oxide
Dinitrogen monoxide (N2O)
別名: Entonox · Laughing gas · N2O · Dinitrogen monoxide · Nitrogen oxide
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Adjunct for induction and maintenance of anaesthesia | Inspired concentrations of 50-70% | Inhalational | Continuous during anaesthesia | Duration of procedure | 🌍 EU |
- Adjunct for induction and maintenance of anaesthesia: Must be administered with a minimum of 30% oxygen.
貓
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Adjunct for induction and maintenance of anaesthesia | Inspired concentrations of 50-70% | Inhalational | Continuous during anaesthesia | Duration of procedure | 🌍 EU |
- Adjunct for induction and maintenance of anaesthesia: Must be administered with a minimum of 30% oxygen.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
概覽
一氧化二氮（N2O，俗稱笑氣）是一種吸入性氣體，通常與氧氣混合使用，作為揮發性麻醉劑（如異氟醚）的輔助藥物，用於全身麻醉的誘導與維持。它能降低主要吸入性麻醉劑的需求濃度，並透過第二氣體效應 (second gas effect)與濃度效應 (concentration effect)加速達到穩定的麻醉深度。
臨床警告： N2O 會導致體內任何充滿氣體的空間迅速擴張，增加體積或壓力。對於患有氣胸或胃擴張扭轉 (GDV) 的病患絕對禁用。
臨床警告： 停止使用 N2O 後，必須持續補充氧氣 5-10 分鐘，以防止擴散性缺氧 (diffusion hypoxia)。
作用機轉
Nitrous oxide causes generalized CNS depression.
When administered at the beginning of volatile agent anaesthesia, it increases the speed of uptake of the volatile agent from the alveoli → second gas effect and concentration effect → hastens attainment of a stable plane of anaesthesia. It has minimal direct respiratory and cardiovascular effects.
安全性與警告
禁忌症
- Patients with air-filled spaces within the body (e.g., pneumothorax, gastric dilatation/GDV, intestinal obstruction)
- Marked respiratory compromise (due to hypoxia risks)
- Raised intracranial pressure (due to associated increases in cerebral blood flow)
不良反應
- Diffusion hypoxia (if oxygen is not supplemented upon discontinuation)
- Megaloblastic changes in bone marrow (with exposure lasting a few hours)
- Agranulocytosis (with prolonged exposure of a few days)
注意事項
Human Safety & Scavenging: Prolonged exposure can have serious adverse effects on human health. Active scavenging is essential.
Important: N2O is not absorbed by activated charcoal in passive scavenging systems.
Hypoxia Risk: A minimum oxygen concentration of 30% is required during anaesthesia. The inspired concentration of oxygen may fall to critically low levels when N2O is used in rebreathing circuits during low flow rates. Do not use in such systems unless the inspired oxygen concentration can be measured on a breath-by-breath basis.
Diffusion Hypoxia: Always supplement with 100% oxygen for 5-10 minutes after turning off N2O.
監測
- Inspired oxygen concentration (FiO2) - especially in rebreathing circuits
- Pulse oximetry (SpO2)
- Capnography (ETCO2)
- Respiratory rate and effort
- Cardiovascular parameters (HR, BP)
藥物動力學
半衰期
吸收
Rapidly absorbed across the alveolar membrane into the blood.
分佈
Distributes rapidly to highly perfused tissues including the brain.
代謝
Virtually no biotransformation; the cobalt ion in vitamin B12 is oxidized by N2O, inhibiting methionine synthase.
排除
Rapidly excreted unchanged via the lungs upon discontinuation.
過量
Overdosage primarily presents as hypoxia if the inspired oxygen concentration falls below 30%. Treatment consists of immediately discontinuing nitrous oxide and providing 100% oxygen via positive pressure ventilation if necessary.
可用產品
劑型
- 100% nitrous oxide (N2O) gas
- Nitrous oxide plus oxygen (Entonox)
獸醫用
- Nitrous oxide medical gas cylinders
人用標示
- Entonox (50% N2O / 50% O2) cylinders
- Nitrous oxide medical gas cylinders
各地核准狀態
Regulated as a medical gas.
POM (Prescription Only Medicine)
POM-V. Strict regulations regarding occupational exposure and scavenging apply.
暫無法規資料: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store in pressurized medical gas cylinders in a cool, dry, well-ventilated area away from combustible materials. Cylinders must be secured to prevent falling.
飼主須知
一氧化二氮（俗稱笑氣）是獸醫在全身麻醉期間常用的一種安全氣體，通常與氧氣及其他麻醉藥物搭配使用，以確保您的寵物在手術過程中保持熟睡且無痛。它能幫助主要麻醉藥物更快發揮作用，並讓獸醫能減少其他藥物的劑量。手術結束後，它會非常迅速地排出體外，讓寵物能平穩地甦醒。
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