Assessing frailty with the Clinical Frailty Scale and using it to shape goals and post-operative care, and the practical ICU management of the obese surgical patient: weight scalars for drug dosing, airway and ventilation, OSA, VTE and pressure care.
At the bedside
Timed steps- 1
Score frailty
AdmissionRecord the Clinical Frailty Scale (CFS) based on the patient's function 2 weeks BEFORE the acute illness (ask family). CFS ≥5 = frail. Use it to inform discussions and care planning, not as a sole triage tool.
- 2
Frailty-focused care
Day 0–1Goals-of-care conversation early with patient and family; delirium prevention (orientation, sleep, glasses/hearing aids, avoid benzodiazepines/anticholinergics); careful fluid and drug dosing (low muscle mass — creatinine overestimates GFR); early mobilisation and nutrition; review polypharmacy.
- 3
Measure and calculate weights
Obese: weighMeasure actual (total) body weight and height; calculate BMI, predicted (ideal) body weight, lean body weight and adjusted body weight. Asian populations have higher metabolic risk at lower BMI.
- 4
Airway and extubation
Obese: airwayExpect difficult mask ventilation and rapid desaturation: ramped/head-up position, preoxygenate with CPAP/HFNC, videolaryngoscope. Extubate fully awake and sitting up; apply HFNC or CPAP early after extubation, especially with known/suspected OSA.
- 5
Lung-protective ventilation
Obese: ventilateSet tidal volume by predicted body weight (6–8 mL/kg PBW), not actual weight; use higher PEEP (often 8–12 cmH₂O or titrated) and head-up 30–45° to counter atelectasis; consider recruitment if haemodynamically stable.
- 6
Choose the right weight scalar
Obese: drugsLipophilic induction agents and opioids by lean body weight; propofol infusion by total or adjusted weight; suxamethonium by total weight; rocuronium by ideal/lean weight; titrate to effect and monitor (TOF, BIS if available). Antibiotics and LMWH often need higher doses — check local protocol.
- 7
VTE, pressure areas, rhabdomyolysis
Obese: preventWeight-adjusted VTE prophylaxis plus mechanical methods; bariatric beds and appropriately sized cuffs; check pressure areas and CK after long surgery (gluteal rhabdomyolysis); screen and treat OSA with CPAP; glucose control.
Analgesia in frail, low-weight patients
Paracetamol (acetaminophen)
- Dose
- 15 mg/kg every 6 h if <50 kg (max 60 mg/kg/day, ≤3 g/day if hepatic risk)
- Worked example
- 42 kg frail patient: 630 mg (≈ 650 mg tablet) every 6 h; max 2.5 g/day.
Clinical Frailty Scale (summary)
| Score | Description |
|---|---|
| 1 | Very fit — robust, active, energetic |
| 2 | Fit — no active disease, exercise occasionally |
| 3 | Managing well — medical problems well controlled, not regularly active beyond walking |
| 4 | Living with very mild frailty — not dependent but symptoms limit activities ('slowed up') |
| 5 | Living with mild frailty — needs help with higher-order activities (finances, transport, heavy housework) |
| 6 | Living with moderate frailty — needs help with all outside activities and keeping house; help with bathing |
| 7 | Living with severe frailty — completely dependent for personal care, but stable |
| 8 | Living with very severe frailty — completely dependent, approaching end of life |
| 9 | Terminally ill — life expectancy <6 months, otherwise not evidently frail |
Score the baseline state ~2 weeks before the acute illness. The CFS is not validated in younger people (<65 years) or stable single-disability (e.g. learning disability).
Weight scalars in obesity (simplified)
| Drug/parameter | Weight to use |
|---|---|
| Tidal volume | Predicted (ideal) body weight |
| Propofol induction, thiopental, fentanyl, morphine boluses | Lean body weight |
| Propofol infusion (maintenance) | Total or adjusted body weight, titrated to effect |
| Suxamethonium | Total body weight |
| Rocuronium, vecuronium | Ideal / lean body weight |
| Sugammadex | Total body weight (some use ideal + 40%) |
| Aminoglycosides | Adjusted body weight, with levels |
| LMWH prophylaxis | Increased fixed dose by weight band (local protocol) |
Use the shared calculators for PBW, adjusted body weight and BMI; verify against local formulary.
STOP-BANG screening for obstructive sleep apnoea
| Item | Question |
|---|---|
| S | Snoring loudly? |
| T | Tired or sleepy during the day? |
| O | Observed apnoeas? |
| P | High blood Pressure (treated)? |
| B | BMI >35 kg/m²? |
| A | Age >50 years? |
| N | Neck circumference >40 cm? |
| G | Gender male? |
Score ≥3 = increased risk of OSA (higher score, higher risk); plan post-operative CPAP/HFNC and opioid-sparing analgesia.
Calculators for this topic
Body mass index
Weight ÷ height². Asian cut-offs differ (overweight ≥ 23, obese ≥ 25 in Indian guidance).
Predicted (ideal) body weight
ARDSNet predicted body weight from height and sex. Use for tidal volume, not for most drug doses.
Adjusted body weight
IBW + 0.4 × (actual − IBW). Used for some drug doses (e.g. aminoglycosides) and nutrition in obesity.
Tidal volume from predicted body weight
Lung-protective tidal volume (usually 6 mL/kg PBW; range 4-8).
Creatinine clearance (Cockcroft-Gault)
(140 − age) × weight ÷ (72 × creatinine), × 0.85 if female. Not valid in unstable AKI.
References
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Extubating the obese post-operative patient
Step 1 of ~6
Reducing post-extubation respiratory failure in obesity/OSA.
Decision: Fully awake, TOF ratio ≥0.9, warm, stable, low FiO₂?
Based on Nightingale CE, Margarson MP, Shearer E, et al; Association of Anaesthetists of Great Britain and Ireland and Society for Obesity and Bariatric Anaesthesia; Chung F, Yegneswaran B, Liao P, et al. Educational use; follow local protocol.
Pathophysiology
Frailty reflects cumulative deficits across systems (sarcopenia, reduced cardiorespiratory and immune reserve, cognitive vulnerability). Obesity reduces FRC and chest-wall compliance, increases oxygen consumption, promotes atelectasis and OSA, and alters drug distribution (lipophilic drugs distribute into fat; hydrophilic drugs mostly into lean mass).
Evidence
- Rockwood 2005 (CSHA, CMAJ): Clinical Frailty Scale correlated with the frailty index and predicted death and institutionalisation; now extended to 9 points (version 2.0, 2020).
- Frailty in ICU patients is consistently associated with higher mortality, longer stay, delirium and discharge to institutional care; it should inform but not replace individual decisions.
- ESC 2022 non-cardiac surgery guideline highlights frailty assessment in older surgical patients as part of risk evaluation.
- AAGBI/SOBA 2015: obese surgical patient guidance — 'obesity paradox', weight scalars, airway management, OSA, regional anaesthesia, post-operative monitoring and VTE.
- STOP-BANG (Chung 2008): simple OSA screening; high sensitivity at a score ≥3.
Controversies
- Use of frailty scores in ICU triage or rationing (risk of discrimination; best used alongside individual assessment).
- 'Obesity paradox' in critical illness — lower observed mortality in mildly obese ICU patients may reflect confounding.
- Optimal PEEP strategy in obese patients (PROBESE: higher PEEP + recruitment did not reduce pulmonary complications).
🇮🇳 India notes
- India's ageing population and rising obesity/diabetes ('thin-fat' phenotype with central adiposity at lower BMI) mean frailty and metabolic disease frequently coexist in surgical ICUs.
- Indian consensus guidance commonly classifies overweight as BMI 23–24.9 and obesity as ≥25 kg/m² (aligned with WHO Asian action points) — verify current national guidance.
- OSA is widely under-diagnosed in India; STOP-BANG at pre-op and ICU admission is cheap and useful.
- Bariatric beds, large BP cuffs and lifting equipment may be scarce — plan before elective bariatric or major surgery.
References
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Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.