Transcript Breathing
BREATHING KIRSTIE MCPHERSON ANAESTHETICS SPR UCLH the centre for Anaesthesia UCL AIMS • • • • How is breathing affected by anaesthesia? Who is most at risk? What can you do about it? Common problems How is breathing affected by anaesthesia? General Anaesthesia • • • • • • Loss of pharyngeal tone Obstruction Soft Palate Base of Tongue Epiglottis Airway management Neuraxial blockade and regional anaesthesia • • • • • • • Less commonly affects breathing Opiates Local anaesthetic “High blocks” Intercostal muscles Diaphragm Hypoventilation Who is most at risk? What can you do about it? Preoperatively Preoperatively • • • • • • • • Assessment History Risk-stratification (scoring systems) Medical optimisation Investigations Multi-disciplinary meetings Surgical options Planning post-operative destination Intraoperatively • Pre-operative monitoring & IV access • Pre-oxygenation • Induction of anaesthesia Apnoea Airway obstruction Take over ventilation & secure airway How Anaesthesia affects Ventilation • • • • • • Loss of airway patency Ability to manage secretions is lost Airway obstruction hypoxaemia hypercapnia The O2 in the FRC is the lung’s store of O2 Important to Preoxygenate Apnoea and time to desaturation Intraoperatively: General anaesthesia Spontaneous Ventilation • Ventilatory response to CO2 • Respiratory rate indicator of pain BUT • Prone to hypoventilation • Some types of surgery require muscle paralysis Controlled Ventilation • Prevent atelectasis • Can control end-tidal CO2 BUT • Can cause barotrauma & volutrauma • Higher risk of awareness Assessment of breathing under anaesthesia Saturations • Oxygenation not ventilation • Waveform Capnography: End-Tidal CO2 • Adequacy of ventilation • Confirms circuit is intact • Immediate information • Flat line: failure of ventilation • Slow rising initial phase: • Upper airway obstruction Inspired O2 • • • • • • Tidal Volume (6-8ml/kg) Frequency Pressure limits PEEP Lung protective strategies Normocarbia Postoperatively • • • • • • Reverse muscle relaxation Suction High flow Oxygen Extubation Supplemental Oxygen Monitoring in recovery Postoperative Problems • • • • • • • • Prevention better than Cure Inadequate reversal Atelectasis Pneumonia Asthma Pain and hypoventilation Analgesia Poor mobility Case Scenario • Mrs Miggins is a 44 year old lady who had an emergency laparotomy and repair of perforated duodenal ulcer 5 days ago • There were no intra-operative complications • Blood loss 450ml • PMH: Asthma, chronic back pain • She is a non-smoker • Medications: Salbutamol and beclometasone inhalers, cocodamol (as required) • NKDA: (Tolerates NSAIDS) Deterioration 5 days post op, she is drowsy and less responsive BP 102/68mmHg HR 110 bpm RR 8 breaths/min SpO2 92% RA (FiO2 0.21) Temp 36.7C BM 3.9 mmol/L U.O 20 ml/h GCS 14/15 (eyes open to command) Can you comment on the drug chart? Summary • Important to understand the changes in physiology under anaesthesia • Identify those most at risk for complications • Protective strategies with mechanical ventilation • Think OXYGENATION and VENTILATION