Fentanyl
Max concentration : Undiluted (50 µg/ml)
Solution: NSS, D5W
Dosing instruction: Bolus Dose 0.35-0.5 µg/kg (50-100 µg V bolus)
Infusion rate: 5 - 10 µg/kg/h (25-500 ug/h)
Titrate dose by 25 µg/h q 30 mins to achieve the desired effect
If used with sedatives, titrate to a RASS score of 0 to -2
Calculate lean body weight
Body Weight
kg.
Height
cm.
Sex
Lean Body Weight
kg.
Lean body weight (Janmahasatian)
Male: LBW = (9270 x TBW)/(6680+(261 x BMI))
Female: LBW = (9270 x TBW)/(8780+(244 x BMI))
Fentanyl 200ug/100ml (2 ug/ml)
Rate (ml/hr)
Dose (µg/kg/h)
Fentanyl 100ug/100ml (1 ug/ml)
Rate (ml/hr)
Richmond Agitation-Sedation Scale (RASS)
RASS score
RASS scoring and interpretation should be based on the sedation protocol being used. For minimal sedation protocols (RASS -2 to 0), sedation should be modified or decreased for a RASS score of -3 or less.
+4 Combative, violent, danger to staff
+3 Pulls or removes tube(s) or catheters; aggressive
+2 Frequent non-purposeful movement, fights ventilator
+1 Anxious, apprehensive, but not aggressive
0 Alert and calm
-1 Awakens to voice (eye opening/contact) > 10 seconds
-2 Light sedation; briefly awakens to voice (eye opening/contant) < 10 seconds
-3 Moderate sedation; movement or eye opening. No eye contact
-4 Deep sedation; no response to voice, but movement or eye opening to physical stimulation
-5 Unarousable; no response to voice or physical stimulation
Voice
Weight descriptors for dose adjustment of ICU drugs in obese patients
Group | Drug | Recommended Dosing |
|---|---|---|
Analgesic | Fentanyl | LBW [1] |
Morphine | LBW [1] | |
Sedative | Dexmedetomidine | LBW [2] |
Midazolam | LD: TBW, MD: LBW [3] | |
Propofol | LD: LBW, MD: TBW [1] | |
Vasopressor & Inotropic | Dobutamine | IBW [7] |
Dopamine | IBW [7] | |
Epinephrine | IBW [7] | |
Levosimendan | TBW [8] | |
Milrinone | TBW [7] | |
Norepinephrine | IBW [7] | |
Beta-blocker | Esmolol | TBW [4] |
Labetalol | IBW [6] | |
Anti-arrhythmic | Lidocaine | LBW [5] |
Neuromuscular Blocking agent | Atracurium | IBW [1] |
Cisatracurium | IBW [1] | |
Anticoagulant | Enoxaparin | TBW [7] |
TBW: True body weight, LBW: Lean body weight, IBW: Ideal body weight, LD: loading dose, MD: maintenance dose
References
1) Ingrande J, Lemmens HJ. Dose adjustment of anaesthetics in the morbidly obese. Br J Anaesth. 2010 Dec;105 Suppl 1:i16-23. doi: 10.1093/bja/aeq312. PMID: 21148651.
2) Rolle A, Paredes S, Cortínez LI, Anderson BJ, Quezada N, Solari S, Allende F, Torres J, Cabrera D, Contreras V, Carmona J, Ramírez C, Oliveros AM, Ibacache M. Dexmedetomidine metabolic clearance is not affected by fat mass in obese patients. Br J Anaesth. 2018 May;120(5):969-977. doi: 10.1016/j.bja.2018.01.040. Epub 2018 Mar 28. PMID: 29661414.
3) Bian L. Critical Care Pharmacotherapy. 1 st ed. the United States of America: American College of Clinical Pharmacy; 2016.
4) Kane-Gill S, Dasta J, editors. High-Risk IV Medications in Special Patient Populations [Internet]. London: Springer London 2011 [cited 2025 May 8] Available from: https://link.springer.com/book/10.1007/978-0-85729-606-1
5) Tognolini AR, Liu X, Pandey S, Roberts JA, Wallis SC, Jackson D, Eley VA. Dosing optimisation of intravenous lidocaine in patients with class 1-3 obesity by population pharmacokinetic analysis. Anaesthesia. 2025 May;80(5):511-521. doi: 10.1111/anae.16531. Epub 2025 Jan 2. PMID: 39745506.
6) Cheymol G, Poirier JM, Carrupt PA, Testa B, Weissenburger J, Levron JC, Snoeck E. Pharmacokinetics of beta-adrenoceptor blockers in obese and normal volunteers. Br J Clin Pharmacol. 1997 Jun;43(6):563-70. doi: 10.1046/j.1365-2125.1997.00609.x. PMID: 9205815; PMCID: PMC2042788.
7) Erstad BL, Barletta JF. Drug dosing in the critically ill obese patient: a focus on medications for hemodynamic support and prophylaxis. Crit Care. 2021 Feb 23;25(1):77. doi: 10.1186/s13054-021-03495-8. PMID: 33622380; PMCID: PMC7901103.
8) Simdax. Simdax SPC [Internet] 2021 [Cited 08 May 2025]. Available from: https://www.simdax.com/siteassets/simdax-spc.pdf
9) Sessler CN, Grap MJ, Brophy GM. Multidisciplinary management of sedation and analgesia in critical care. Semin Respir Crit Care Med. 2001;22(2):211-26. doi: 10.1055/s-2001-13834. PMID: 16088675.