I’m going to wean off a patient from ventilator and extubate him following the coronary artery bypass graft surgery the same day of operation. His weight is 90 kg and his age is 52 years. His ejection fraction of heart was 45-50% pre operatively. I will upload his latest ventilatory settings photograph. His urinary output is 60ml per hour. His muscle power is satisfactory. I want you to interpret the values and teach me how to proceed what to do and when to do with underlying physiological basis
Excellent case, and this is **exactly** the right time to think carefully and physiologically. I’ll break this into **clear, practical steps**, interpreting the ventilator **screen you uploaded**, then walking you through **how to wean and extubate safely after CABG**, with **why** we do each step.
I’ll speak to you like a CT-ICU consultant at the bedside.
---
## 1. First — interpret the ventilator screen (what you showed)
### Ventilator & Mode
**Machine:** Puritan Bennett 840
**Mode:** **SIMV (VC) + Pressure Support**
This is a **classic weaning mode** after cardiac surgery.
---
### Key displayed parameters (from screen)
#### A. Respiratory mechanics
* **Ppeak:** ~19 cmH₂O
* **Pmean:** ~10 cmH₂O
* **PEEP:** 5 cmH₂O
➡️ **Excellent**.
Peak < 20 suggests **good lung compliance**, no major bronchospasm or secretion load.
---
#### B. Gas exchange / ventilation
* **Set VT:** 600 mL
* **Measured VTe:** ~576 mL
* **Minute ventilation:** ~8.2 L/min
* **FiO₂:** 40%
* **Total RR:** 14/min
* **SIMV rate:** 10/min → patient contributing breaths
➡️ This is **very reassuring**:
* Adequate tidal volume
* Patient triggering spontaneous breaths
* No tachypnoea
* Reasonable FiO₂
---
#### C. Pressure support & triggering
* **PS:** 10 cmH₂O
* **Flow trigger (V-sens):** 3.3 L/min
* **E-sens:** 25%
➡️ Indicates **comfortable patient–ventilator synchrony**
---
#### D. I:E ratio
* **1 : 1.3**
➡️ Slightly shortened expiration, but acceptable in post-op cardiac patient with normal lungs.
---
### Summary of ventilator interpretation
> š¹ This patient is **already doing most of the work of breathing**
> š¹ Ventilator pressures are low
> š¹ Oxygen requirement is modest
> š¹ This is a **good extubation candidate**
---
## 2. Now interpret the patient as a whole (very important)
### Patient factors
* **Age:** 52 → favourable
* **Weight:** 90 kg → IBW ~70–75 kg → VT appropriate
* **EF:** 45–50% → **moderate LV function**, acceptable
* **Urine output:** 60 mL/h → **adequate perfusion**
* **Muscle power:** satisfactory → NMB fully reversed
* **Post-CABG same-day extubation** → standard fast-track pathway
➡️ **Nothing here is stopping extubation**
---
## 3. Physiological criteria for extubation (checklist with reasons)
### A. Oxygenation
You want:
* **SpO₂ > 94%**
* **FiO₂ ≤ 40%**
* **PEEP ≤ 5**
✅ Your patient already meets this.
**Why?**
After extubation, you lose:
* PEEP
* Fixed FiO₂
So the patient must tolerate **lower oxygen support**.
---
### B. Ventilation
You want:
* RR < 25
* VT > 5–6 mL/kg IBW
* No hypercapnia (ABG preferred)
✅ RR 14, VT ~576 mL → good.
**Physiology:**
Adequate alveolar ventilation =
> VT × RR – dead space
> He is clearly ventilating well.
---
### C. Haemodynamics
You want:
* MAP ≥ 65 mmHg
* Minimal or no inotropes/vasopressors
* Good urine output
✅ Urine output confirms adequate cardiac output.
**Why important post-CABG?**
Extubation → ↑ venous return + ↑ sympathetic tone → LV must cope.
---
### D. Neurology & airway protection
You want:
* Awake or easily arousable
* Follows commands
* Strong cough & gag
* Head lift / hand grip
✅ You said muscle power satisfactory.
---
## 4. Step-by-step: HOW to wean him now (practical bedside plan)
### STEP 1 — Reduce ventilator support gradually
#### Do this:
* Reduce **SIMV rate** from **10 → 6**
* Reduce **PS** from **10 → 8 cmH₂O**
* Keep:
* PEEP = 5
* FiO₂ = 40%
⏱ Observe for **10–15 minutes**
**What you’re looking for:**
* RR < 25
* No accessory muscle use
* Stable BP and HR
* No anxiety or diaphoresis
---
### STEP 2 — Switch to spontaneous breathing trial (SBT)
Two acceptable methods:
#### Option A (preferred post-cardiac):
* **PS 5 cmH₂O + PEEP 5**
* FiO₂ 40%
* Duration: **30 minutes**
#### Option B:
* **CPAP 5 cmH₂O**
* FiO₂ 40%
* Duration: **30 minutes**
**Physiology:**
This simulates post-extubation work of breathing while maintaining minimal alveolar recruitment.
---
### STEP 3 — ABG during or after SBT (important in CABG)
Check:
* **PaO₂ > 70 mmHg**
* **PaCO₂ normal or mildly elevated**
* **pH > 7.32**
If acceptable → proceed.
---
## 5. Extubation sequence (do not rush this)
### Before extubation
1. **Suction ETT + oral cavity**
2. Ensure:
* Normothermia
* Electrolytes ok (K⁺, Mg²⁺ especially post-CPB)
3. Stop sedatives completely
4. Position patient **45° head-up**
---
### Extubation
* Deflate cuff
* Ask patient to **take a deep breath**
* Remove tube at **peak inspiration**
* Apply **oxygen immediately**
---
### Post-extubation oxygen
Preferred:
* **Venturi mask 40%** or
* **High-flow nasal oxygen (if available)**
---
## 6. Immediate post-extubation monitoring (first 30–60 min)
Watch for:
* Tachypnoea
* Desaturation
* Hypertension / tachycardia (pain, LV strain)
* Poor cough or secretion retention
**Post-CABG pearl:**
Early pain control reduces:
* Sympathetic surge
* Myocardial oxygen demand
š Use **IV fentanyl boluses** or low-dose infusion if needed.
---
## 7. Common post-CABG extubation pitfalls (important teaching)
### ❌ Premature extubation
Leads to:
* Reintubation
* Myocardial stress
* Increased mortality
### ❌ Fluid overload
Pulmonary oedema after extubation
→ watch CVP, urine output, lung auscultation
### ❌ Electrolyte imbalance
* Low Mg²⁺ → AF
* Low K⁺ → arrhythmias
---
## 8. Bottom-line decision for YOUR patient
> ✅ **He is READY for extubation today**
### Recommended plan:
1. Reduce SIMV rate & PS
2. Perform 30-min SBT (PS 5 / CPAP 5)
3. ABG
4. Extubate with oxygen
5. Close monitoring
---
If you want, next I can:
* Teach you **how to recognise extubation failure early**
* Walk you through **ABG interpretation post-extubation**
* Or create a **CABG fast-track extubation checklist** you can keep on your phone
Just tell me š
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