I now have solid textbook backing across all three symptoms. Here is the full clinical answer:
Post-CABG: Cough, Constipation & Nausea - Causes and Clinical Significance
Yes, all three symptoms are common after traditional open CABG. They each have multiple, overlapping causes rooted in surgery, anesthesia, and post-op medications.
1. COUGH
Post-CABG cough is very common and almost always has an identifiable cause.
A. ACE Inhibitor-Induced Cough (Most Common Drug Cause)
ACE inhibitors (ramipril, enalapril, lisinopril) are routinely started after CABG to reduce LV remodeling and mortality. They cause a dry, persistent, tickling cough in up to 20% of patients - mediated by accumulation of bradykinin in the airway mucosa.
- Onset: days to weeks after starting the drug
- Character: dry, irritating, non-productive
- Management: switch to an ARB (e.g., valsartan), which does not cause cough
"ACE inhibitors are not associated with the cough that may occur in up to 20% of persons receiving an ACE inhibitor" - Brenner and Rector's The Kidney
B. Pleural Effusion
After CABG, pleural effusions are extremely common (especially left-sided when the LITA is harvested). Fluid accumulates in the pleural space and irritates the lung, causing:
- Productive or dry cough
- Positional cough (worse lying flat)
- Associated breathlessness
- Requires drainage if large
C. Pulmonary Congestion / Left Heart Failure
Low cardiac output syndrome or fluid overload from CPB can lead to pulmonary edema with frothy cough, orthopnea, and crackles on auscultation.
D. Atelectasis and Secretion Retention
Post-sternotomy pain discourages deep breathing and effective coughing, leading to lobar collapse, mucus plugging, and productive cough. This is called "splinting" - the patient guards the sternal wound and cannot generate enough force to clear secretions effectively.
"Splinting may promote atelectasis and interfere with the patient's ability to cough and clear secretions" - Miller's Anesthesia, 10th Ed.
E. Amiodarone Pulmonary Toxicity
Amiodarone, frequently used to treat post-CABG AF, can cause subacute pulmonary toxicity presenting as cough, dyspnea, fever, and patchy infiltrates. Rare but important to recognize.
"Amiodarone-induced pulmonary toxicity usually presents as a subacute illness characterized by cough, dyspnea, fever, and patchy pulmonary infiltrates" - Fishman's Pulmonary Diseases and Disorders
F. Hospital-acquired Pneumonia
Prolonged intubation and ICU stay increase aspiration and infection risk, causing productive cough with fever and consolidation.
2. CONSTIPATION
Constipation is almost universal in the first days to weeks after CABG and is multifactorial.
A. Opioid Analgesia (Primary Cause)
Post-CABG pain is managed with opioids (morphine, fentanyl, oxycodone). Opioids act on mu-receptors throughout the GI tract causing:
- Decreased gastric motility and emptying
- Decreased pyloric tone
- Reduced intestinal peristalsis
- Constipation, ileus, and occasionally nausea/vomiting
"Common adverse side effects associated with opioid therapy include nausea, vomiting, constipation, urinary retention, delirium..." - Barash Clinical Anesthesia, 9th Ed.
"Opioids: Gastrointestinal - decreased motility, constipation, biliary colic" - Schwartz's Principles of Surgery, 11th Ed.
B. General Anesthesia and Reduced Gut Motility
General anesthesia suppresses autonomic GI function. Combined with CPB-related splanchnic hypoperfusion, the gut motility remains suppressed for days post-operatively.
C. Immobility and Reduced Oral Intake
Bed rest, restricted fluids, and reduced diet in the ICU further slow bowel transit.
D. Electrolyte Disturbances
Hypokalemia (common post-CPB) impairs smooth muscle function in the bowel wall, worsening constipation.
E. Reduced Fiber and Fluid Intake
Hospital diet restrictions and IV fluid management reduce the bulk and moisture that normally stimulate peristalsis.
Management: Routine stool softeners (docusate) and laxatives (senna, lactulose) should be prescribed prophylactically alongside opioids. Methylnaltrexone or naldemedine can be used for opioid-induced constipation specifically.
3. NAUSEA
Nausea is extremely common post-operatively and often clusters with constipation as part of opioid-induced bowel dysfunction.
A. Opioid-Induced Nausea
Opioids stimulate the chemoreceptor trigger zone (CTZ) in the medulla and reduce pyloric tone, causing nausea and vomiting.
"Decreased pyloric tone [from opioids leads to] nausea and vomiting" - Miller's Anesthesia, 10th Ed.
B. General Anesthesia / Post-Operative Nausea and Vomiting (PONV)
PONV affects 30-80% of surgical patients in the first 24-48 hours. Volatile anesthetics (sevoflurane, isoflurane) and nitrous oxide are the biggest triggers.
- Risk factors in CABG: female sex, non-smoking, history of motion sickness, prolonged procedure time
C. Digoxin Toxicity
Digoxin is sometimes used for rate control in post-CABG AF. Even at therapeutic levels, nausea, vomiting, and anorexia are classic early signs of digoxin toxicity - particularly if the patient has renal impairment (common post-CABG).
D. Hypokalemia and Electrolyte Disturbances
Low potassium (from diuretics, CPB hemodilution) causes generalized GI dysmotility with nausea and bloating.
E. Gastric Stasis / Ileus
CPB-related mesenteric hypoperfusion and opioid use together cause gastroparesis and ileus, with nausea, abdominal distension, and inability to tolerate oral feeds.
F. Amiodarone and Other Medications
Amiodarone, antibiotics, and other post-op drugs frequently list nausea as a side effect.
Summary Table
| Symptom | Most Common Cause | Other Important Causes |
|---|
| Cough | ACE inhibitor (up to 20%), pleural effusion | Atelectasis/splinting, pulmonary congestion, amiodarone toxicity, pneumonia |
| Constipation | Opioid analgesia | Anesthesia, immobility, hypokalemia, reduced intake |
| Nausea | Opioids / PONV | Digoxin toxicity, ileus, electrolytes, amiodarone, gastric stasis |
Is This Expected?
Yes - these symptoms together are the norm, not the exception. The combination of cough + constipation + nausea in a post-CABG patient almost always points to:
- ACE inhibitor started on discharge (cough)
- Opioid pain management (constipation + nausea)
The priority is to:
- Assess the cough - rule out pulmonary edema, effusion, or pneumonia first; if clear, switch ACE-I to ARB
- Treat constipation prophylactically with docusate/senna when opioids are prescribed
- Manage nausea with ondansetron or metoclopramide; check digoxin levels and potassium
- Encourage early mobilization - key to restoring GI function and clearing pulmonary secretions
Sources: Sabiston Textbook of Surgery; Miller's Anesthesia 10th Ed.; Barash Clinical Anesthesia 9th Ed.; Schwartz's Principles of Surgery 11th Ed.; Fishman's Pulmonary Diseases; Brenner and Rector's The Kidney