Shock

Consultant in Intensive Care Medicine and Clinical Senior Lecturer Cardiff University September 2009

Paul Frost

Shock

Shock

Introduction

Shock is a state of circulatory insufficiency which if untreated can cause cellular injury, organ failure and death. Shock may complicate many common, acute illnesses. It is important that medical practitioners are able to recognise and manage this dangerous condition.

Introduction

Shock

Learning Objectives

On completion of this module the student should be able to;• Define and classify shock• Describe the pathophysiology of shock• Describe the clinical approach to a shocked patient using the ABCDE algorithm• Describe investigation and management of shock

Learning Objectives

Shock

Definition

• Shock is best defined as the inadequate delivery or utilisation of oxygen for cellular metabolic needs, i.e. any process which results in hypoxia at the cellular level.

• Most often shock arises as a result of ineffectual perfusion rather than impaired cellular oxygen consumption.

Definition

Shock

Classification

Traditionally shock is classified into four groups according to the main mechanism of decompensation:

• Cardiogenic• Obstructive• Hypovolaemic• Distributive

Classification

Shock

Cardiogenic

• Myocardial infarction• Myocardial contusion• Myocarditis• Acute valvular failure• Arrhythmia• Acute ventricular septal wall defect

Classification

Shock

Obstructive

• Pulmonary embolus• Cardiac tamponade• Tension pneumothorax

Classification

Shock

Hypovolaemic

• Fluid depletion• Vomiting and diarrhoea• Burns• Polyuria

• Haemorrhagic• Trauma• Gastrointestinal• Retroperitoneal

Classification

Shock

Distributive

• Sepsis• Neurogenic• Anaphylaxis

Classification

Shock

Classification

There may be considerable overlap between shock states classified in this way. For example sepsis, an example of distributive shock, frequently co-exists with myocardial depression and relative hypovolaemia.

Classification

Shock

Pathophysiology

• At the cellular level:

• Switch from aerobic to anaerobic metabolism• Accumulation of lactate, hydrogen ions and inorganic phosphates • Precipitating energy crisis in the cell

» Loss of cellular integrity » Cellular swelling» Oxidative stress» Lipid peroxidation» Mitochondrial dysfunction» APOPTOSIS

Pathophysiology

ShockClinical approach

At the bedside three questions need to be addressed:

• Is the patient critically ill?• Does the patient have shock?• If so, what type of shock is it?

Clinical approach

ShockClinical approach

• Critical illness is any disease process which causes physiological instability leading to disability or death within minutes or hours.

• Physiological instability can be detected by deviations from the normal range in simple clinical observations such as LOC, blood pressure, pulse, respiratory rate and urine output

Clinical approach

ShockClinical approach

• Rapidly assimilate history at bedside

• Conduct clinical examination using the Airway, Breathing, Circulation, Disability and Exposure (ABCDE) algorithm.

Clinical approach

ShockClinical approach

Airway assessment

• Compromised airway commonly associated with impaired LOC. Clinical signs include:• Noisy breathing (snoring, grunting) or stridor• Absence of protective cough and gag reflexes• Drooling, with inability to clear oropharyngeal secretions

Clinical approach

ShockClinical approach

Breathing assessment.

Signs of respiratory distress include:• Increased respiratory rate• Diaphoresis• Use of accessory muscles• Tracheal tug• Intercostal indrawing• Cyanosis (late and unreliable sign)

Clinical approach

ShockClinical approach

Cardiovascular assessment .

Signs of Cardiovascular instability include:• Altered mental status• Cold extremities• Delayed capillary refill• Tachycardia• Hypotension• Oliguria

Clinical approach

ShockClinical approach

Disability assessment

Level of consciousness (LOC) can be assessed using AVPU system. Alert, responds to Voice, responds to Pain or is Unrousable.

Clinical approach

ShockClinical approach

Exposure .

Requirement to fully expose patient for relevant systematic examination. Practitioner should be aware of environmental temperature and potentially adverse effects of cooling (shivering causes increased metabolic work and contributing to further cardiovascular decompensation).

Clinical approach

ShockClinical approach

Does the patient have shock?

Clinical findings which might suggest this include:• Relevant history• Tachycardia (heart rate > 120 beats/minute)• Hypotension (SBP < 90 mmHg)• Tachypnoea (Respiratory rate > 25 breaths per minute)• Altered mental status• Delayed capillary refill time/cold extremities• Oliguria (<0.5 ml/kg/hr)

Clinical approach

ShockClinical approach

The sensitivity and specificity of the clinical findings associated with shock are greatly improved if they are considered all together. The presence of two or more clinical signs strongly suggests that the patient is critically ill and at increased risk of death.

Clinical approach

ShockClinical approach

What type of shock is it?

Consider history and use shock classification system as aide memoireSpecific clinical findings can help discriminate between different shock states:

• Jugular Venous Pressure (elevated in cardiogenic and obstructive shock states)• Purpuric rash seen in meningococcal sepsis

Clinical approach

ShockInvestigations

The causes of shock can usually be established using routine radiology and laboratory investigations.

Chest X-ray, electrocardiogram, arterial blood gases including lactate, full blood count, urea and electrolytes, troponin, blood clotting screen, C-reactive protein and appropriate microbiological cultures.

Investigations

ShockInvestigations

Transthoracic echocardiogram invaluable:

Provide diagnostic information• Left ventricular failure• Tamponade• Pulmonary embolus

Provide information on volume status• Ventricular filling

Investigations

ShockGeneral measures

General measures.

• Ensure patent airway (may need intubation), provide oxygen using mask with reservoir bag, restore circulation

• Nurse in appropriate area ICU or HDU

• Full monitoring• Continuous ECG, respiratory rate, blood pressure• LOC, urine output and pulse oximetery.

Management

ShockFluid therapy

Fluid therapy

• Crystalloid, colloid or blood products• Fluid requirement assessed by clinical response in particular urine output, pulse and

blood pressure and lactate• In sepsis fluid requirement may be substantial as replacement fluid leaks into

interstitium

• All fluid may have deleterious side effects• Coagulopathy (colloids) acidosis (normal saline)

Management

ShockSeptic Shock

Septic shock.

• Source control • Blood cultures• Early empiric broad spectrum antibiotics• Measure lactate• Treat hypotension with fluids and vasopressors• If persistent hypotension then maintain • CVP > 8 mmHg and ScVO2 >70%

Management

ShockHypovolaemic Shock

Hypovolaemic shock.

• Arrest further fluid losses by treating underlying cause for example antibiotics for clostridium difficile, covering burns or haemostasis either surgical, radiological or endoscopic techniques for haemorrhage

• Fluid replacement guided by circulatory response

Management

ShockCardiogenic Shock

Cardiogenic shock.

• Revascularisation for myocardial infarction• Surgery for acute valvular failure• Drainage of tamponade• Aortic balloon pump• Inotropic drugs• Advanced haemodynamic monitoring

Management

ShockObstructive Shock

Obstructive shock.

• Intercostal catheter for tension pneumothorax• Drain for pericardial tamponade• Thrombolysis or embolectomy for massive pulmonary embolus

Management

ShockKey Points

History, examination and simple investigations are usually sufficient to diagnose the presence and cause of shock At the bedside use ABCDE algorithm Specific therapy for shock is dependent on underlying cause

Summary of Key Points

ShockResources

NICE Short Clinical Guidelines Technical Team (2006). Acutely ill patients in hospital: recognition of and responses to acute illness in adults. London: National Institute for Health and Clinical Excellence. Available from www.nice.org.uk

Frost P, Wise M. Recognition and early management of the critically ill ward patient. Br J Hosp Med 2007;68(10):M180-3

Frost P, Wise M. Recognition and management of patient with shock. Acute Medicine 2006;5(2):43-47

Resources

ShockResources

O; Driscoll Br, Howard LS, Davison AG. On behalf of the British Thoracic Society Emergency Oxygen Guideline Development Group. Guideline for emergency oxygen use in adult patients. Thorax 2008; 63: Supplement VI

Scottish Intercollegiate Guidelines Network. Management of acute upper and lower gastrointestinal bleeding. A national clinical guideline September 2008: Available from http://www.sign.ac.uk

Scottish Intercollegiate Guidelines Network. Acute coronary syndromes. A national clinical guideline February 2007. Available from http://www.sign.ac.uk

Resources

ShockResources

Joint Formulary Committee. British National Formulary. 57th edition, London: British Medical Association and Royal Pharmaceutical Society of Great Britain; 2009: 2.10.1: Management of myocardial infarction.

Dellinger RP, Levy MM, Carlet JM, Bion J et al. Surviving sepsis campaign: International guidelines for management of sepsis and septic shock: Crit Care Med 2008;36:296-327

Resources