Post-Operative Complications
د. صباح نوري السعدM.B.Ch.B, D.A,F.I.M.S, C.A.B.A & I.C1-The Respiratory System: 1. Hypoxia: a common problem in early post-operative periodCauses:Reduced central drive to ventilation (anaesthetic drugs, CO2 washout).Residual effect of muscle relaxantUpper airway obstructionBronchospasmIncreased ventilation-perfusion mismatchingReduced functional residual capacityAspiration of blood/stomach contentsPneumothoraxPainSputum retentionPulmonary 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 arrhythmiaCentral nervous system: CO2 narcosis → Delayed patient recovery from anaesthesia with delayed return of protective reflexes.
2- The Cardiovascular System: Hypotension: CausesMost 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 tiltAdministration of intravenous fluidOxygen should always be given, because hypotension increases ventilation-perfusion mismatching.
Hypertension: Causes:Most common cause is pain, especially in patients who are already hypertensive.Hypoxia, hypercapnia, or both.Sometimes distended bladderRarely: metabolic derangement such as malignant hyperthermia, thyroid crisis.Arrhythmias: most commonly occur in:Patient with pre-existing cardiac diseaseHypoxia or hypercapniaDrugs: adrenaline has been infiltrated during surgery, or the volatile anaesthetic halothane.
Major cardiac events: such as:Myocardial infarctionUnstable anginaPulmonary oedemaVentricular tachycardia
Pre-operative risk factors:Recent myocardial infarctionSignificant 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 embolismAbdominal (mainly pelvic) malignanciesFemale on oestrogen - oral contraceptive pillsPrevention:Prophylactic low molecular weight heparin (LMWH) 2 hours before operation in high risk patients.Encourage early ambulationGood hydrationRegional anaesthetic techniques
3-The Gastro-Intestinal System: Nausea and vomiting: patients at risk:Female > maleYoung > oldHistory 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 hydrationAggressive pain control with non-opioid analgesic drugsPost-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 transfusionPrecipitation of bile salts in the renal tubules (obstructive jaundice)Post-renal causes:ProstatismBlocked 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).