Sevoflurane is the most ideal inhalation anesthetic in clinical practice and is currently used in a wider range of applications. Although many beginners know that sevoflurane usage and dosage are: induction 8%, oxygen flow 6L/min; maintain 2.5% -3%, oxygen flow 2L/min, but do not know how many ml of liquid sevoflurane is used in a single operation? Below we simply calculate it.
Under standard conditions (0°C, 1 atmospheric pressure): The volume of 1 mol of gas is 22.4L. In other words, the conversion of 1 mol of sevoflurane liquid to gaseous state produces 22.4 L of gas.
Ø 1ml of sevoflurane liquid can change the number of ml gas?
Known: sevoflurane molecular weight: 200.06 (1 mol sevoflurane mass 200.06 g), sevoflurane specific gravity 1.5 g/ml
Therefore: 1 ml sevoflurane = 1 x specific gravity / molecular weight x 22.4 x [(273 °C + temperature) / 273 °C] = 1 x 1.5/200.06 x 22.4L x (273 + 0) / 273 ≈ 168 ml
Ø 1 hour consumption of gaseous (liquid) sevoflurane?
Formula: oxygen flow × inhalation concentration × inhalation time
For example: 1L/min oxygen flow rate, 1% inhalation concentration, 1 hour surgical consumption of gaseous sevoflurane: (1000ml/min) x 1% x 60min = 600ml
The liquid 1ml of sevoflurane can be converted to 168ml of gas, so 600ml of the gas is 3.6ml liquid (coefficient K=3.6)
Ø How many ml of sevoflurane should be used in one surgery?
From the above calculations, we have come to calculate the sevoflurane coefficient K = 3.6
Surgical consumption of sevoflurane volume = 3.6 × oxygen flow × inhalation concentration × inhalation time
For example: Our clinical sevoflurane recommended to maintain the concentration of 3%, oxygen flow 2L/min, 1h of sevoflurane dose for surgery: 3% concentration x2L/min oxygen flow x1h x3.6 = 3x2x3.6 = 21.6ml
Induction period consumption ≈ 8% concentration x 6L/min oxygen flow rate x (2min/60min) x 3.6 = 5.7ml
Therefore, a 1 h operation would consume approximately 27.3 ml if sevoflurane anesthesia was used for induction and maintenance.