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ce30161d.yaml
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153 lines (127 loc) · 6.54 KB
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assumptions:
- First-order elimination kinetics (linear)
- One-compartment pharmacokinetic model
- Instantaneous drug distribution
- Arrhenius temperature dependence for hydrolysis rate
- Steady-state achieved after 3-5 half-lives
- Constant body temperature during dosing interval
- No active metabolite contribution
- No protein binding changes with temperature
- No drug-drug interactions affecting elimination
author: ''
category: derived
clinical_context: 'Use when:
1. Administering cisatracurium or other hydrolytic muscle relaxants during cardiac
surgery with cardiopulmonary bypass (CPB)
2. Managing neuromuscular blockade in hypothermic patients (28-34°C)
3. Adjusting dosing for febrile patients or extreme temperature conditions
4. Planning infusion rates or bolus intervals for prolonged procedures
5. Predicting drug accumulation in temperature-variable conditions
Key applications:
- CPB temperature phases (normothermia → hypothermia → rewarming)
- Therapeutic hypothermia protocols
- Fever management in ICU patients receiving muscle relaxants
- Precision dosing in temperature-sensitive populations'
created_at: '2026-01-02T21:19:20.994602'
derivation_steps:
- 'Temperature-corrected elimination rate constant using Arrhenius equation
📝 Notes: Cisatracurium 經由 Hofmann elimination（非酵素性的化學分解）和酯水解代謝。水解反應的速率遵循 Arrhenius
方程，溫度越高反應越快。這對低體溫（如心臟手術）或發燒患者特別重要。'
- "\U0001F3E5 [CLINICAL] ⚠️ **臨床重要性**：低體溫患者（如 CPB 期間 T=28-32°C）的藥物清除率會顯著降低，需要調整劑量。反之，發燒患者清除率增加，藥效時間縮短。\n\
\ Related: k_e, T"
- 'Accumulation factor for multiple dosing
📝 Notes: 累積因子描述重複給藥後，穩態濃度相對於單次給藥的倍數。當給藥間隔 τ 遠大於半衰期（τ >> t1/2）時，R_ac ≈ 1（無累積）。當 τ
接近或小於半衰期時，R_ac > 1（有累積）。'
- 'Steady-state peak concentration with accumulation factor
📝 Notes: 穩態峰值濃度 = 單次給藥的峰值 × 累積因子。在多次給藥後，藥物會累積直到穩態（通常需要 3-5 個半衰期）。Cisatracurium 的半衰期約
20-30 分鐘，所以約 1.5-2 小時達到穩態。'
- 'Steady-state trough concentration
📝 Notes: 谷值濃度 = 峰值濃度在一個給藥間隔後的殘餘。對於 cisatracurium，谷值通常非常低（接近零），因為其半衰期短。但在低體溫時，ke
降低，谷值會升高，可能導致藥物累積和延長肌肉鬆弛。'
- 'Temperature-corrected steady-state peak concentration (complete form)
📝 Notes: 這是完整的溫度校正公式。可以看到溫度透過 Arrhenius 項影響消除速率，進而影響累積和穩態濃度。當 T < T_ref（低體溫），ke
降低，分母變小，C_max,ss 升高（藥物累積）。當 T > T_ref（發燒），ke 增加，分母變大，C_max,ss 降低（清除加快）。'
- "\U0001F3E5 [CLINICAL] \U0001F4CA **數值範例**（Cisatracurium）：\n- 正常體溫 (37°C = 310K):\
\ ke ≈ 0.2 /min\n- 低體溫 (28°C = 301K, CPB): ke ≈ 0.08 /min（消除速率降至 40%）\n- 發燒 (40°C\
\ = 313K): ke ≈ 0.25 /min（消除速率增加 25%）\n\n假設 τ = 30 min（常用追加劑量間隔）：\n- 37°C: R_ac\
\ = 1/(1-e^(-0.2×30)) = 1.002（幾乎無累積）\n- 28°C: R_ac = 1/(1-e^(-0.08×30)) = 1.11（累積\
\ 11%）→ 需降低劑量！\n Related: k_e, T, R_ac, C_max_ss"
- '⚠️ [LIMITATION] ⚠️ **重要假設與限制**：
1. **一室模型假設**：假設藥物瞬間分布到全身（對 cisatracurium 是合理的，因為其快速分布）
2. **線性動力學**：假設 ke 不隨濃度改變（對水解反應是合理的）
3. **穩態假設**：需要 3-5 個半衰期達到穩態（cisatracurium 約 1.5-2 小時）
4. **溫度穩定**：假設體溫在給藥期間保持恆定（CPB 期間可能不成立！）
5. **不考慮活性代謝物**：Cisatracurium 的代謝物（laudanosine）有 CNS 毒性，但通常濃度低'
derived_from: []
description: Temperature-corrected multiple dosing model for hydrolytic drugs (cisatracurium).
Combines first-order elimination kinetics with Arrhenius temperature dependence
and accumulation factor to predict steady-state peak and trough concentrations.
Particularly relevant for hypothermic conditions (cardiac surgery, CPB) and febrile
patients.
expression: D/(V_d*(1 - exp(-k_e_ref*tau*exp(E_a*(1/T_ref - 1/T)/R))))
id: ce30161d
limitations:
- Not valid during rapid temperature changes (e.g., active rewarming in CPB)
- Does not account for laudanosine accumulation (active metabolite with CNS effects)
- Assumes constant Vd (may change with temperature and fluid shifts)
- Linear model may not capture nonlinear effects at extreme temperatures
- Does not consider individual variability in Hofmann elimination
- May underestimate accumulation in renal/hepatic impairment (ester hydrolysis component)
- 'Temperature range: validated for 28-42°C only'
- Requires knowledge of Ea (activation energy) which varies between individuals
name: cisatracurium_multiple_dosing_temp
references:
- Kisor DF, Schmith VD. Clinical pharmacokinetics of cisatracurium besilate. Clin
Pharmacokinet. 1999;36(1):27-40.
- Diefenbach C, et al. Pharmacokinetics and pharmacodynamics of cisatracurium in hypothermic
and normothermic patients. Br J Anaesth. 2000;84(2):166-170.
- Arrhenius S. Über die Reaktionsgeschwindigkeit bei der Inversion von Rohrzucker
durch Säuren. Z Phys Chem. 1889;4:226-248.
- Kisor DF, et al. Pharmacokinetics and pharmacodynamics of cisatracurium in renal
failure. Anesthesiology. 1996;84(3):603-611.
- 'Rowland M, Tozer TN. Clinical Pharmacokinetics and Pharmacodynamics: Concepts and
Applications. 4th ed. Lippincott Williams & Wilkins; 2011. Chapter 19: Multiple-Dose
Regimens.'
tags:
- pharmacokinetics
- cisatracurium
- muscle-relaxant
- temperature-correction
- multiple-dosing
- accumulation-factor
- hypothermia
- cardiopulmonary-bypass
- arrhenius
- hydrolysis
- steady-state
- anesthesiology
- critical-care
variables:
D:
description: ''
unit: ''
E_a:
description: ''
unit: ''
R:
description: ''
unit: ''
T:
description: ''
unit: ''
T_ref:
description: ''
unit: ''
V_d:
description: ''
unit: ''
k_e_ref:
description: ''
unit: ''
tau:
description: ''
unit: ''
verification_method: ''
verified: false
verified_at: null
version: 1.0.0