Overdose etc

• Patients are at an increased risk of developing hepatotoxicity following a paracetamol overdose if they are taking liver enzyme-inducing medications e.g. rifampicin, phenytoin, carbamazepine, chronic alcohol excess, St John's Wart
• Patients who have taken a paracetamol overdose should have a(n) paracetamol level taken at 4 hours post-ingestion and 2 hours before completion of N-acetylcysteine Paracetamol is only useful for a nomogram if taken >4 hours after ingestion If ingestion time is unknown then take a paracetamol level at presentation If level remains >10mg/L at 2 hours pre-completion then continue acetylcysteine [Medicines and Healthcare products Regulatory Agency. Drug Safety Update September 2012, vol 6, issue 2: A1]
• Management of paracetamol overdose <2hrs after ingestion: Activated charcoal & N-acetylcystine (NAC) [Medicines and Healthcare products Regulatory Agency. Drug Safety Update September 2012, vol 6, issue 2: A1]
• Management of paracetamol overdose >2hrs after ingestion: N-acetylcystine (NAC) Activated charcoal may be considered up to 4hrs if >30g of paracetamol is ingested [Medicines and Healthcare products Regulatory Agency. Drug Safety Update September 2012, vol 6, issue 2: A1]
• A nomogram may be used in paracetamol overdose to determine if treatment is indicated [Medicines and Healthcare products Regulatory Agency. Drug Safety Update September 2012, vol 6, issue 2: A1] The nomogram should only be use if all the following are met:Time of ingestion knownAcute overdose (not staggered)Immediate release paracetamol has been taken (not prolonged release)Paracetamol level taken >4 hours since ingestion
• Liver transplantation is indicated for paracetamol overdose if arterial pH is <7.3 at 24 hours post ingestion [Dr. John O'Grady [1989] King's College Criteria for Acetaminophen Toxicity. Available from https://en.wikipedia.org/wiki/King's_College_Criteria]
• Warfarin should be stopped 5 days before elective surgery Give oral Vit K the day before surgery if INR is ≥1.5 [NICE BNF [Accessed 2024] Treatment summaries. Oral anticoagulants. Available from https://bnf.nice.org.uk/treatment-summaries/oral-anticoagulants/]
• Warfarin should be stopped 5 days before elective surgery. If the INR is ≥1.5 the day before surgery, give oral vitamin K [NICE BNF [Accessed 2024] Treatment summaries. Oral anticoagulants. Available from https://bnf.nice.org.uk/treatment-summaries/oral-anticoagulants/]
• When can warfarin be resumed following surgery? Evening of the surgery OR next day If patient had a bridging dose of LMWH and there is a high risk of bleeding, wait until at least 48hrs after surgery [NICE BNF [Accessed 2024] Treatment summaries. Oral anticoagulants. Available from https://bnf.nice.org.uk/treatment-summaries/oral-anticoagulants/]
• Patients scheduled for surgery who are at high risk of thromboembolism and take warfarin may be given a bridging dose of LMWH during the 5 days before surgery. Stop the LMWH 24 hours before surgery If patient had a bridging dose of LMWH and there is a high risk of bleeding, wait until at least 48hrs after surgery [NICE BNF [Accessed 2024] Treatment summaries. Oral anticoagulants. Available from https://bnf.nice.org.uk/treatment-summaries/oral-anticoagulants/]
• Patients taking warfarin who require emergency surgery that cannot be delayed should be given dried prothrombin complex AND IV vitamin K to reverse the anticoagulation INR should be checked before surgery [NICE BNF [Accessed 2024] Treatment summaries. Oral anticoagulants. Available from https://bnf.nice.org.uk/treatment-summaries/oral-anticoagulants/]
• Definitions: Type 1 respiratory failure: Hypoxia (<8kPa) AND normo/hypocapnia Type 2 respiratory failure: Hypoxia (<8kPa) AND hypercapnia (>6.0kPa) Normal values: - PaO2: 10-14kPa - PaCO2: 4.5-6kPa
• What pathophysiological mechanisms cause type 1 respiratory failure? Ventilation/Perfusion (V/Q) mismatch, hypoventilation, abnormal diffusion, right to left cardiac shunts Examples of each: V/Q mismatch - Pneumonia - PE - COPD - Asthma Hypoventilation - Opioids - Neuromuscular diseases (MND) - Obesity hypoventilation syndrome - Chest wall abnormalities Abnormal diffusion - Pulmonary oedema - Interstitial lung disease (e.g. pulmonary fibrosis) Right to left cardiac shunts - Tetralogy of Fallot - ASD - VSD - PDA
• What pathophysiological mechanism causes type 2 respiratory failure? hypoventilation with or without V/Q mismatch Pulmonary - Asthma - COPD - Pnuemonia Decreased resp drive - Opioids - Trauma - CNS compromise Neuromuscular disease - GBS - MND - Cervical spinal cord lesion Chest wall abnormalities - Flail chest - Kyphoscoliosis
• Patients with long-standing hypoxia may have polycythaemia, pulmonary hypertension or cor pulmonale
• Patients with hypercapnia may experience cardiovascular features such as peripheral vasodilation, tachycardia and bounding pulse
• What investigation is most useful for monitoring respiratory failure? ABG Critical for monitoring PaO2 and PaCO2
• Both type 1 & 2 respiratory failure are managed with oxygen and by treating the underlying cause Oxygen therapy in type 2 respiratory failure should be increased started at a lower FiO2 as they may be insensitive to CO2 and respiration could be driven by hypoxia
• Oxygen therapy in type 2 respiratory failure should be started at a lower FiO2 as they may be insensitive to CO2 and respiration could be driven by hypoxia
• What are the different types of oxygen therapy? Nasal cannula - 24-44% FiO2 Simple face mask - 40-60% FiO2 Venturi mask - 24-60% FiO2 Non-Rebreather mask - 60-95% FiO2
• What are the different types of respiratory pressure support (least → most invasive)? High-flow nasal cannula (HFNC) CPAP NIV (BiPAP) Mechanical ventilation
• Positive end-expiratory pressure (PEEP) helps to prevent airway collapse, improves ventilation and reduces atelectasis in patients who require respiratory support HFNC & NIV
• CPAP provides a constant pressure to keep the airways expanded Not technically NIV as it does not involve ventilation
• BiPAP provides a higher pressure during inspiration AND a lower pressure during expiration The higher pressure during inspiration helps to force air into the lungs, the lower end-expiratory pressure prevents the airway from collapsing
• Mechanical ventilation is only used when other respiratory support is inadequate. Patients do require sedation Used for the shortest amount of time possible ETT (endotracheal tube) or tracheostomy
• Extracorporeal membrane oxygenation (ECMO) is the most extreme respiratory support only used VERY RARELY when intubation with ventilation is not adequate Only available in specialist centres - not available in most ICUs
• The most common blood test abnormalities seen in patients with dehydration are ↑Urea, ↑Albumin, ↑Haematocrit ↑Urea - due to increased renal reabsorption of urea mediated by ADH ↑Albumin - serum concentration increases due to relative decrease in intravascular fluid (dehydration is the most common cause of hyperalbuminaemia) ↑Haematocrit - serum concentration of RBCs increases due to relative decrease in intravascular fluid Urea:Creatinine ratio will also be increased due to greater increase in urea compared to creatinine eGFR will appear reduced due t...
• What is the most common cause of hyperalbuminaemia? Dehydration ↑Urea - due to increased renal reabsorption of urea mediated by ADH ↑Albumin - serum concentration increases due to relative decrease in intravascular fluid (dehydration is the most common cause of hyperalbuminaemia) ↑Haematocrit - serum concentration of RBCs increases due to relative decrease in intravascular fluid Urea:Creatinine ratio will also be increased due to greater increase in urea compared to creatinine eGFR will appear reduced due to ↑creatinine
• Diarrhoea and vomiting may cause dehydration due to increased fluid losses
• Long durations of sun exposure during hot weather may cause dehydration if fluid intake is insuffcient
• Intense exercise and excessive sweating may cause dehydration if fluid intake is insuffcient
• The most common iatrogenic cause of dehydration is diuretics e.g. furosemide
• Fatigue, nausea & lightheadedness are all symptoms of mild dehydration in adults Adults with mild dehydration may experience orthostatic hypotension
• Lightheadedness, headache & muscle cramp are all symptoms of moderate dehydration in adults Signs include: reduced urine output, prolonged CRT, reduced skin turgor, tachycardia, orthostatic hypotension
• Extreme fatigue, fainting & confusion/coma are all symptoms of severe dehydration in adults Signs include: cold skin and extremities, hypotension, tachypnoea/cardia, oliguria/anuria, shock, sunken eyes and hollow cheeks
• Postural hypotension alone may be a sign of mild dehydration in adults Symptoms include: fatigue, nausea, light-headedness
• Prolonged CRT, sunken eyes, reduced skin turgor, oliguria may be a sign of moderate dehydration in adults Symptoms include: lightheadedness, headache & muscle cramp
• Cold skin/extremities, hypotension, tachypnoea/cardia & anuria may be a sign of severe dehydration in adults Symptoms include: extreme fatigue, fainting, confusion→coma
• Oliguria is defined as urinary output of <400ml per day in adults Or <20ml/kg/hr
• What is the management of Moderate dehydration in children/adults? oral rehydration solution (ORS) ORS contains glucose, NaCl, KCl & sodium citrate [MSF [2013] Management of A MEASLES EPIDEMIC. Available from https://medicalguidelines.msf.org/en/viewport/mme/english/management-of-a-measles-epidemic-30542833.html] [NICE [2009] Diarrhoea and vomiting caused by gastroenteritis in under 5s: diagnosis and management [CG84] Available from https://www.nice.org.uk/guidance/cg84/chapter/Recommendations]