Post-Operative Complications د. صباح نوري السعد M.B.Ch.B, D.A, F.I.M.S, C.A.B.A & I.C

1-The Respiratory System: 1. Hypoxia: a common problem in early post-operative period Causes: Reduced central drive to ventilation (anaesthetic drugs, CO2 washout). Residual effect of muscle relaxant Upper airway obstruction Bronchospasm Increased ventilation-perfusion mismatching Reduced functional residual capacity Aspiration of blood/stomach contents Pneumothorax Pain Sputum retention Pulmonary embolism

Clinical Diagnosis of hypoxia: The first and most sensitive organ to hypoxia is the BRAIN. Effect of hypoxia on cerebral cortex: restlessness, agitation; if not treated → coma and death. Hypothalamus (which control the function of Autonomic Nervous System): tachycardia, hypertension, and if not treated → bradycardia and cardiac arrest. Medulla: tachypnoea (shallow rapid respiration), if not treated → bradypnoea and apnoea.

Hypercapnia: Causes: Reduced central drive to ventilation by anaesthetic drugs, especially opioid anagelsics. Excessive oxygen administration to chronic bronchitic patient who rely on their hypoxic drive. Consequences: Cardiovascular system: tachycardia, hypertension and arrhythmia Central nervous system: CO2 narcosis → Delayed patient recovery from anaesthesia with delayed return of protective reflexes.

2- The Cardiovascular System: Hypotension: Causes Most common cause is a low blood volume (blood loss often occult, or loss of other fluids, e.g. significant mesenteric oedema after extensive and prolonged abdominal surgery → 3rd space loss). Residual effect of anaesthetics (especially spinal and epidural) N.B: Post-operative hypotension is due to hypovolemia until proved otherwise. Rarely due to a cardiac causes (e.g. fast atrial fibrillation, complete heart block, myocardial ischemia, or myocardial infarction).

Management: most causes of hypotension respond well to: Head—down tilt Administration of intravenous fluid Oxygen should always be given, because hypotension increases ventilation-perfusion mismatching.

Arrhythmias: most commonly occur in: Hypertension: Causes: Most common cause is pain, especially in patients who are already hypertensive. Hypoxia, hypercapnia, or both. Sometimes distended bladder Rarely: metabolic derangement such as malignant hyperthermia, thyroid crisis. Arrhythmias: most commonly occur in: Patient with pre-existing cardiac disease Hypoxia or hypercapnia Drugs: adrenaline has been infiltrated during surgery, or the volatile anaesthetic halothane.

Major cardiac events: such as: Myocardial infarction Unstable angina Pulmonary oedema Ventricular tachycardia

Pre-operative risk factors: Recent myocardial infarction Significant heart failure (pulmonary oedema, gallop rhythm, raised jugular venous pressure). Intra-operative risk factors: abnormality of the haemodynamic state, such as tachycardia, hypotension, and hypertension. Post-operative risk factors: prolonged post-operative ischemia with tachycardia

Pulmonary embolism: Common in patient with: History of previous pulmonary embolism Abdominal (mainly pelvic) malignancies Female on oestrogen - oral contraceptive pills Prevention: Prophylactic low molecular weight heparin (LMWH) 2 hours before operation in high risk patients. Encourage early ambulation Good hydration Regional anaesthetic techniques

3-The Gastro-Intestinal System: Nausea and vomiting: patients at risk: Female > male Young > old History of motion sickness, and post-operative nausea and vomiting. Type of surgery; more common in eye, ear, pelvic and laparoscopic surgeries. Post-operative pain. Non-smokers

Prevention and treatment of post-operative nausea and vomiting: Prophylactic anti-emetic therapy with a 5-hydroxytryptamine 3 (5HT3) antagonist drugs as: Ondansetron (Zofran®) 8mg intravenously combined with Dexamethasone 8mg intravenously. The above regimen is superior to a combination of: Metclopramide 5-10mg and dexamethasone 8 mg. Generous intravenous hydration Aggressive pain control with non-opioid analgesic drugs Post-operative O2 therapy

4-The Urinary System: Oliguiria: Causes: Pre-renal causes (hypovolemia): are common in the post-operative period (mainly due to inadequate fluid or blood replacement during surgery) Renal causes: Mismatch blood transfusion Precipitation of bile salts in the renal tubules (obstructive jaundice) Post-renal causes: Prostatism Blocked or misplaced urinary catheter

Management: Adequate fluid hydration till we reach a urine output which is >30ml/hour (preferably gauged by central venous pressure). If no urine inspite of good hydration, then enhanced dieresis with diuretics (furosemide).