Understanding Anaphylaxis

Anaphylaxis

• Anaphylaxis is a generalized immunological condition of sudden onset that occurs after exposure to a foreign substance
• The mechanism of anaphylaxis can involve an IgE-mediated reaction to a foreign protein, be complement mediated, or be unknown
• Regardless of the mechanism, mast cells and basophils release mediators, which produce clinical manifestations.
• Angio-oedema caused by ACE inhibitors and hereditary angio-oedema may present similarly to anaphylaxis
• Hereditary angio-oedema is not usually accompanied by urticaria and is treatable with a C1 esterase inhibitor.

Anaphylaxis Common Causes

• Drugs and vaccines like antibiotics and aspirin
• Hymenoptera stings from bees/wasps
• Foods like nuts, shellfish, strawberries, and wheat
• Latex exposure

Anaphylaxis Clinical Features

• The speed of onset and severity vary, but onset is usually in minutes/hours.
• A prodromal aura or a feeling of impending death may be present
• Those on B-blockers or with ischaemic heart disease (IHD) or asthma may have especially severe features
• Usually, two or more systems are affected.
• Respiratory symptoms include swelling of the lips, tongue, pharynx, and epiglottis, potentially leading to upper airway occlusion
• Lower airway involvement is similar to acute severe asthma — dyspnoea, wheeze, chest tightness, hypoxia, and hypercapnia.
• Skin symptoms include pruritus, erythema, urticarial, and angio-oedema.
• Cardiovascular symptoms include peripheral vasodilation and increased vascular permeability, causing plasma leakage, decreased intravascular volume, hypotension, and shock. Arrhythmias, ischaemic chest pain, and ECG changes may be present.
• Gastrointestinal symptoms include nausea, vomiting, diarrhea, and abdominal cramps.

Anaphylaxis Treatment

• Stop giving the suspected factor causing the reaction and carefully scrape away any stings
• Administer 100% oxygen
• Open and maintain the airway
• Get expert help immediately if there is upper airway oedema, and emergency intubation or a surgical airway and ventilation may be needed
• For patients with shock, airway swelling, or respiratory difficulty: administer 0.5mg (0.5mL of 1:1000 solution) adrenaline intramuscularly, repeating after 5 minutes if there is no improvement
• For adults treated with an adrenaline auto-injector, the 300mcg dose is often enough, but more doses may be needed
• Those taking tricyclic antidepressants, MAOIs, or B-blockers should only receive 50% of the usual adrenaline dose
• In profound shock or life-threatening situations, CPR/ALS is needed, and slow IV adrenaline (1:10,000 or 1:100,000 solution) should be considered
• The slow IV adrenaline is recommended only for experienced clinicians with IV access, noting the different adrenaline strengths based on use
• If there is no response to adrenaline, consider glucagon 1-2mg IM/IV every 5 minutes, particularly in those taking B-blockers
• Give a B2-agonist like salbutamol 5mg, nebulized with O2 for bronchospasm, potentially adding nebulized ipratropium bromide 500mcg.
• If hypotension does not respond rapidly to adrenaline, give IV fluid like a rapid infusion of 1-2L IV 0.9% saline, and further infusion based on clinical state
• Antihistamine H1 blockers (eg chlorphenamine 10-20mg slow IV) and H2 blockers (eg ranitidine 50mg IV) are commonly given as secondary drugs
• With hydrocortisone 100–200mg slow IV, antihistamines might reduce the severity/duration of symptoms
• Look for prolonged reactions and biphasic responses after initial treatment, and observe for at least 4-6 hours after all symptoms have settled

Other Anaphylaxis Considerations

• An inhaled B2-agonist, such as salbutamol, can be an adjunctive measure for severe bronchospasm that does not respond rapidly to other treatment.
• Slow IV adrenaline (epinephrine) 1:10,000 solution should only be considered if profound shock is immediately life-threatening and CPR/ALS is necessary
• This is a hazardous option only for an experienced practitioner who can obtain IV access without delay
• If adults are treated with an EpiPen®, the 300mcg dose is usually sufficient, but a second dose may be required
• Half doses of adrenaline (epinephrine) may be safer for patients on amitriptyline, imipramine, or B-blockers
• A crystalloid might be safer than a colloid.

Anaphylaxis Algorithm for Adults

• Airway, Breathing, Circulation, Disability, Exposure
• Diagnoses to look for include acute onset of illness, life-threatening airway and/or breathing and/or circulation problems, and skin changes
• Patients should lie flat with their legs raised

Adrenaline Doses (IM unless with IV experience)

• Adult: 500 micrograms
• Child more than 12 years: 500 micrograms
• Child 6-12 years: 300 micrograms
• Child less than 6 years: 150 micrograms
• Titrate adrenaline IV to adults at 50 micrograms and children at 1 microgram/kg, only administered by experienced specialists

Drugs for Anaphylaxis

• Adult or child more than 12 years: 10 mg chlorphenamine, 200 mg hydrocortisone
• Child 6-12 years: 5 mg chlorphenamine, 100 mg hydrocortisone
• Child 6 months to 6 years: 2.5 mg chlorphenamine, 50 mg hydrocortisone
• Child less than 6 months: 250 micrograms/kg chlorphenamine, 25 mg hydrocortisone

Choking

• Recognize choking, often indicated by a person clutching their neck while experiencing a sudden airway problem when eating
• Victims with severe airway obstruction may be unable to speak or breathe and lose consciousness

Choking Algorithm for Adults

• Encourage coughing if there is mild airway obstruction with effective cough
• Continue checking to see if the cough becomes ineffective or the obstruction is relieved
• If there is severe airway obstruction with ineffective cough, but the person is still conscious
• Give 5 back blows
• Give 5 abdominal thrusts
• Start CPR if the person is unconscious

Cardiac Arrest

• Suspect cardiac arrest in any unconscious patient without signs of life, examining only a major (carotid or femoral) pulse for 10 seconds
• Most patients experienced a sudden and unexpected out-of-hospital event
• The cardiac arrest team (ED staff, the hospital team, or a combination of both) should be present in the resuscitation room with all equipment ready to receive the patient if an ambulance brings the patient
• Perform resuscitation in a calm, quiet, confident manner with minimal interruption to the performance of basic life support (BLS) or defibrillation
• Prior warning to the department is usually relayed by radio or direct telephone link from the Ambulance Service, while relatives/friends are taken to an appropriate room

Procedures to Start Simultaneously for Cardiac Arrest

• Continue BLS
• Remove/cut clothing to allow defibrillation, ECG monitoring, chest compression, and IV access
• Obtain the ECG trace through defibrillator pads or monitor leads
• Follow the ALS algorithm
• Do not interrupt CPR to perform defibrillation

In-hospital Resuscitation Algorithm

• If the patient is collapsed/sick, shout for help and assess the patient
• Assess for signs of life
• If no signs of life, call the resuscitation team and start CPR 30:2 with oxygen and airway adjuncts. Then apply pads/monitor and attempt defibrillation if appropriate
• If there are signs of life, assess ABCDE (Airway, Breathing, Circulation, Disability, Exposure), recognize and treat, including Oxygen, monitoring, and IV access, and call the resuscitation team if appropriate

Adult Basic Life Support — Airway and Ventilation

• Use advanced airway techniques from the start if possible
• Tilt the head and lift the chin to open the airway, or use jaw thrust if neck trauma is suspected and leave well-fitting dentures in place
• Aim for each breath to last approximately 1 second and make the chest rise, holding head tilt/chin lift and watching for the chest to fall

Adult Basic Life Support — Chest Compression Technique

• Put the heel of one hand over the middle of the lower half of the patient’s sternum, with the other hand on top, and extend or interlock the fingers to avoid pressure on the ribs
• Depress the sternum 5–6cm while releasing all pressure at a rate of 100–120/min, with compression and release phases taking the same time
• Use a ratio of 30 chest compressions to 2 ventilations (30:2)
• Aim to change the person providing chest compressions every 2 minutes, while ensuring minimal pauses

Cardiac Arrest Management — Defibrillation

• Most survivors have an initial rhythm of VF/VT, which is treated with defibrillation
• With time, chances of successful defibrillation and survival drop dramatically
• Adhesive pads have replaced manual paddles in many hospitals
• Place one pad to the right of the upper sternum below the clavicle and the other in the mid-axillary line level with V6 electrode position, avoiding the female breast and keeping pads over 15cm away from pacemakers
• Use shock energy of 150J with biphasic defibrillators or 360J energy for older monophasic defibrillators.
• Compress as continuously as possible with minimal delays
• Pause briefly to assess the rhythm, recommence compressions until the defibrillator is charged, pause briefly to deliver a shock, then immediately restart CPR and continue for 2 minutes before reassessing the rhythm or feeling for a pulse
• In a monitored patient with pulseless VT/VF where defibrillation is unavailable, give a precordial thump of approximately 20cm to the lower half of the sternum using a tightly clenched fist

Cardiac Arrest Management — Airway Management

• Only attempt tracheal intubation with the correct experience, as the laryngeal mask airway is a readily available, rapid alternative
• Aim to ventilate with 100% O2, using an inspiratory time of 1 second, a volume sufficient to produce a normal rise of the chest, at a rate of 10/min
• Ventilate continuously when using tracheal tubes or laryngeal mask airways, aside from defibrillation or pulse checks
• End-tidal CO2 monitoring is useful for confirming correct tracheal tube placement and indirectly measure cardiac output during CPR

Drugs for Cardiac Arrest

• There is little evidence that drugs improve outcome, and central IV cannulation is difficult, risky, and interrupts CPR
• Giving a 20mL saline bolus and elevating the limb for 10-20 seconds is adequate after giving a peripheral IV drug
• Consider the intraosseous route if you are unable to gain IV access

Non-shockable Rhythms for Cardiac Arrest

• PEA is cardiac arrest with an ECG trace
• PEA may be caused by failure of the normal cardiac pumping mechanism or obstruction to cardiac filling or output
• Prompt and appropriate correction can result in survival as the 4 H's and 4 T's

4 H's

• Hypoxia
• Hypovolaemia
• Hyper/hypokalaemia/metabolic disorders
• Hypothermia

4 T's

• Tension pneumothorax

• Tamponade (cardiac)

• Toxic substances

• Thromboembolic/mechanical obstruction

• Asystole is the absence of cardiac electrical activity, but chest compressions and ventilation should be continued in an attempt to increase the amplitude and frequency of VF to make it more susceptible to defibrillation

• Continue resuscitation based on the time since onset, the nature of the event, and the estimated prospects for a successful outcome

• Continue resuscitation while VF/pulseless VT persists if initially appropriate to commence resuscitation

• Asystole unresponsive to treatment and arrests lasting more than 1 hour are rarely associated with survival, barring some younger patients, hypothermia, near drowning, and drug overdose

Mechanical CPR Devices

• AutoPulse involves a circumferential load-distributing band chest compression device, while LUCAS is a gas-driven sternal compression device
• Useful in situations where the attempt is prolonged, such as cardiac arrest associated with hypothermia, poisoning, or following fibrinolytic treatment, to ensure consistent CPR and free up an additional member of the team

Advanced Life Support Algorithm

• Call the resuscitation team if the patient is unresponsive and not breathing or only occasionally gasping
• CPR 30:2, attach defibrillator/monitor and minimize interruptions
• Assess rhythm, leading to shockable (VF/Pulseless VT) or non-shockable (PEA/Asystole) paths
• Give 1 shock if shockable and immediately resume CPR for 2 minutes, and after the return of spontaneous circulation use the ABCDE approach and treat the precipitating cause

Steps During CPR

• Maintain high-quality CPR with rate, depth, and recoil
• Plan actions before interrupting CPR
• Give oxygen
• Consider advanced airway and capnography
• Maintain continuous chest compressions when needing advanced airways
• Ensure Vascular access using Intravenous and Intraosseous methods
• Give adrenaline every 3–5 minutes and correct reversible causes

Notes on Using the Advanced Life Support Algorithm

• Know underlying cardiac rhythm as soon as possible to guide treatment, and do not interrupt CPR except to perform defibrillation
• Search for and correct reversible causes of the arrest and exercise caution before using adrenaline/epinephrine in arrests associated with cocaine or other sympathomimetic drugs
• Give IV adrenaline 1mg and amiodarone 300mg for VF/pulseless VT that does not respond to three shocks, followed by 1mg adrenaline every 3–5min, or give lidocaine 1mg/kg IV as an alternative
• Give IV magnesium sulphate 2g (= 8mmol = 4mL of 50% solution) for torsade de pointes and refractory VF in patients with suspected digoxin toxicity or hypomagnesaemia
• Give IV 1mg adrenaline for asystole and PEA as soon as possible and thereafter every 3–5min
• Give 10mL 10% IV calcium chloride (6.8mmol) for PEA arrests associated with hyperkalaemia, hypocalcaemia, or Ca2+-channel blocking drug or magnesium overdose
• Follow algorithm loops as long as it is considered appropriate for the resuscitation, and stop after commencement if the rhythm is not VF

Post Resuscitation Care

• Early post-resuscitation, coma or pupil reflexes do not reliably indicate accurate prognosis
• Accurate prognostication is possible 24-72 hours in, and involve the intensive care unit/critical care unit (ICU/CCU) team early

Steps Pending and Following ROSC

• Ensure that the airway is protected and oxygenation/ventilation is maintained through high-flow oxygen, use pulse oximetry and titrate to achieve SPO2 of 94-98%
• May require IPPV, Correct hypoxia and prevent hypercapnoea under ABG guidance
• Insert an oro- or nasogastric tube in intubated patients to decompress the stomach
• Obtain a 12-lead ECG and a CXR to check the position of the tracheal tube and lines and presence of pneumothorax, etc
• Optimize cardiac output, optimizing vasopressors and fluids under hemodynamic monitoring guidance
• Maintain arterial pressures 'normal' to patient, and address seizures with medication
• Administer appropriate anticonvulsants and ensure adequate oxygenation and ventilation
• Measure and correct abnormalities to treat any contributing conditions -Ensure proper treatment of seizures if applicable, check blood counts for anemia, and watch plasma glucose level
• No drug has been shown to improve cerebral outcome following cardiac arrest
• Avoid or treat hyperthermia with antipyretic or active cooling
• There is compelling data to support inducing mild therapeutic hypothermia (32-34°C) in patients who are comatose after out-of-hospital VF arrest, typically maintained for 12-24 hours through cooling or an infusion

Central Venous Access

• Central venous access may be required for administering emergency drugs, measure central venous pressure, administer IV fluids, or transvenous cardiac pacing
• Other routes like the femoral vein are generally preferred for giving large volumes rapidly
• The external jugular vein is often readily visible and can be cannulated easily
• Iinternal jugular and subclavian veins are useful for central venous access in the ED, favouring the internal jugular vein via a 'high' approach with US guidance on the right side of the neck
• The femoral vein is useful for temporary access in severe trauma, burns, and in drug addicts with many thrombosed veins.

Seldinger Technique for Central Venous Access

• This method of choice involves inserting a hollow metal needle into the vein and a flexible guidewire through the needle, removing said needle
• A tapered dilator and plastic cannula are inserted over the guidewire, then the cannula is secured before lastly, checking the flow of blood through the cannula

Precautions and Problems with Central Line Placement

• Central venous access is a specialized technique with potentially life-threatening complications, including pneumothorax, haemothorax, arterial puncture, thoracic duct damage, air embolism, and infection
• Bleeding dyscrasias and anticoagulant treatment are contraindications to internal jugular and subclavian vein access
• Severe pulmonary disease is a relative contraindication to central venous access, especially by the subclavian route due to the risk of pneumothorax
• Expert supervision is essential

Severe Sepsis and Septic Shock

• Septic patients experience SIRS due to infection, while severe sepsis involves septic patients with evidence of organ hypoperfusion
• A patient is in septic shock if they exhibit hypotension or a lactate of >3 mmol/L, unresponsive to intravenous fluid resuscitation

Diagnosing SIRS

• Body temperature of >38°C or 90/min

• Respiratory rate >20 breaths/min or PaCO2 < 4.3kPa

• WCC >12 × 109/L or 10% immature (band) forms

• Management involves ICU therapy for severely septic patients, aiming for certain therapeutic goals like a CVP of 8–12mmHg and a a mean arterial pressure >65mmHg

• Take blood cultures to measure glucose before administering antibiotics or treat infections. Administer noradrenaline or fluids.

Shock

• Shock is a clinical condition where vital organs are not oxygenated or perfused, recognized by hypotension, altered consciousness, poor peripheral perfusion, oliguria, and tachypnoea

Classifying Shock

• Hypovolemic: Blood loss, fluid loss/redistribution.
• Cardiogenic: Myocardial infarction (MI), arrhythmias, valve dysfunction.
• Septic: More common in extremes of age, those with DM, renal/hepatic failure and more
• Anaphylactic is induced by anaphylactic shock
• Neurogenic shock involves neurogenic causes

Managing Shock

• Priorities include addressing priorities, giving ample high-flow oxygen, securing venous access and taking blood for FBC, U&E, glucose, etc
• Monitor and stabilize signs by providing IV fluids and monitoring vital signs Give crystalloid (0.9% saline) 20mL/kg as bolus and provide treatments to address causes:
• Treat specifically and determine treatmens needed using imaging and testing
• Provide Laparotomy ,Thrombolysis/angioplasty,
• Manage antibiotics