Critical care and emergency medicine

3 Critical care and emergency medicine


A critically ill patient is one at imminent risk of death. The approach required in managing the critically ill patient differs from that required in less severely ill patients, with immediate resuscitation and stabilisation of the patient’s condition taking precedence. Intensive care units (ICUs) are for patients with potential or established organ failure. Initially established for the provision of mechanical ventilation for patients with respiratory failure, ICUs now monitor and support all the major organ systems. High-dependency care provides an intermediate level between intensive care and general ward care; it is appropriate for patients who have had major surgery and for those with single-organ failure.


Rigid rules to determine admission to ICU/HDU are destined to fail because every case must be evaluated on its own merits. The guiding principle when considering ICU/HDU admission should be the timely use of this resource in patients who have a realistic prospect of recovering to achieve a reasonable quality of life. Early identification and admission of critically ill patients improves survival and reduces the length of stay on the ICU (Box 3.1).



3.1 FACTORS IN THE ASSESSMENT OF A POSSIBLE ICU ADMISSION image



• Primary diagnosis and other active medical problems

• Prognosis of underlying condition

• Severity of physiological disturbance—is recovery still possible?

• Life expectancy and anticipated quality of life post-discharge (age alone should not be a contraindication to admission)

• Wishes of the patient and/or relatives

• Availability of the required treatment/technology


MONITORING


On entering an ICU, relatives, students and even clinicians may be intimidated by the numerous tubes and cables attaching each patient to a battery of ‘alarming’ machines. Trends in data collected provide an important guide to a patient’s progress.



CLINICAL EXAMINATION OF THE CRITICALLY ILL PATIENT



image


Recognising the critically ill patient











Cardiovascular signs Respiratory signs Neurological signs

• Cardiac arrest

• Pulse rate < 40 or > 140 bpm

• Systolic blood pressure (BP) < 100 mmHg

• Tissue hypoxia
Poor peripheral perfusion

Metabolic acidosis

Hyperlactataemia

• Poor response to volume resuscitation

• Oliguria: < 0.5 ml/kg/hr (check urea, creatinine, K+
• Threatened or obstructed airway

• Stridor, intercostal recession

• Respiratory arrest

• Respiratory rate < 8 or > 35/min

• Respiratory ‘distress’: use of accessory muscles; unable to speak in complete sentences

• SpO2 < 90% on high-flow O2

• Rising PaCO2 > 8 kPa (> 60 mmHg), or > 2 kPa (> 15 mmHg) above ‘normal’ with acidosis
• Threatened or obstructed airway

• Absent gag or cough reflex

• Failure to maintain normal PaO2 and PaCO2

• Failure to obey commands

• Glasgow Coma Scale (GCS) < 10

• Sudden fall in level of consciousness (GCS fall > 2 points)

• Repeated or prolonged seizures



MONITORING THE CIRCULATION



• ECG monitoring records changes in heart rate and rhythm.

• Arterial BP is measured continuously using an arterial line placed in the radial artery.

• Central venous pressure (CVP) is monitored using a catheter placed in the right internal jugular vein or the subclavian vein with the distal end sited in the upper right atrium. If the CVP is low in the presence of a low BP, fluid resuscitation is necessary. However, a raised CVP does not necessarily mean that the patient is adequately volume-resuscitated, as pulmonary hypertension or right ventricular dysfunction can also lead to a raised CVP.

• If CVP interpretation is difficult, it may be appropriate to insert a pulmonary artery flotation catheter so that pulmonary artery pressure and pulmonary artery ‘wedge’ pressure (PAWP), which approximates to left atrial pressure, can be measured and used to guide fluid resuscitation.

• Cardiac output can be assessed with the thermodilution technique using a PA catheter. Less invasive alternative methods include oesophageal Doppler USS.

• Urine output is a sensitive measure of renal perfusion, provided that the kidneys are not damaged (e.g. acute tubular necrosis) or affected by drugs (e.g. diuretics, dopamine), and can be monitored accurately if a urinary catheter is in place.

• Fluid balance should be accurately assessed. The insensible loss from skin, respiration etc. is normally 500–1000 ml/day but can exceed 2 litres/day in a pyrexial patient with open wounds.

• A metabolic acidosis with base deficit >5 mmol/l often indicates increased lactic acid production in poorly perfused, hypoxic tissues. Serial lactate measurements may help in monitoring response to treatment.


MONITORING RESPIRATORY FUNCTION



• Oxygen saturation (SpO2) is measured continuously.

• ABGs are measured several times a day in a ventilated patient so that inspired oxygen and minute volume can be adjusted to achieve the desired PaO2 and PaCO2.

• Capnography measures CO2 in expired air continuously and helps to assess the adequacy of alveolar ventilation in intubated patients.


PRESENTING PROBLEMS



CIRCULATORY FAILURE: ‘SHOCK’


Circulatory failure or ‘shock’ exists when the oxygen delivery fails to meet the metabolic requirements of the tissues. ‘Shock’ is often considered to be synonymous with hypotension, although hypotension may be a late manifestation of circulatory failure. The causes of ‘shock’ may be classified into:


Hypovolaemic: Any condition provoking a major reduction in blood volume, e.g. haemorrhage, severe burns, dehydration.

Cardiogenic: Any form of severe heart failure, e.g. myocardial infarction, acute mitral regurgitation.

Obstructive: Obstruction to blood flow around the circulation, e.g. major pulmonary embolism, cardiac tamponade, ‘tension’ pneumothorax.

Neurogenic: Caused by major brain or spinal injury producing disruption of brain-stem and neurogenic vasomotor control; may be associated with neurogenic pulmonary oedema.

Anaphylactic: Inappropriate vasodilatation triggered by an allergen (e.g. bee sting).

Septic/SIRS: Infection or other causes of a systemic inflammatory response syndrome (SIRS) that produce widespread endothelial damage with vasodilatation, arteriovenous shunting, microvascular occlusion and tissue oedema, resulting in organ failure.

General features of shock are shown in Box 3.2.



3.2 GENERAL FEATURES OF SHOCK image



• Hypotension (systolic BP <100 mmHg)

• Tachycardia (>100/min)

• Cold, clammy skin

• Rapid, shallow respiration

• Drowsiness, confusion, irritability

• Oliguria (urine output <30 ml/hr)

• Elevated or reduced CVP

• Multi-organ failure

Hypovolaemic, cardiogenic and obstructive causes of circulatory failure produce the ‘classical’ image of shock, with cold peripheries, weak central pulses and evidence of a low cardiac output. In contrast, neurogenic, anaphylactic and septic shock is usually associated with warm peripheries, bounding pulses and features of a high cardiac output.



RESPIRATORY FAILURE, INCLUDING ARDS


The majority of patients admitted to ICU/HDU will have respiratory problems either as the primary cause of their admission or secondary to pathology elsewhere. Attempts should be made to reduce the work of breathing, e.g. by treating bronchoconstriction or using continuous positive airways pressure (CPAP). The patient’s appearance (tachypnoea, difficulty speaking in complete sentences, laboured breathing, exhaustion, agitation or increasing obtundation) is more important than measurement of ABGs in deciding when to intubate and ventilate.


Acute respiratory distress syndrome (ARDS): This describes the acute, diffuse pulmonary inflammatory response to either direct (via airway or chest trauma) or indirect blood-borne insults from extrapulmonary pathology. It is characterised by neutrophil sequestration in pulmonary capillaries, increased capillary permeability and protein-rich pulmonary oedema. If this early phase does not resolve with treatment of the underlying cause, a fibroproliferative phase ensues and causes pulmonary fibrosis. It is frequently associated with other organ dysfunction as part of multiple organ failure. The term ARDS is often limited to patients requiring ventilatory support on the ICU, but less severe forms, conventionally referred to as acute lung injury (ALI) and with similar pathology, occur on acute medical and surgical wards. The clinical picture is non-specific and shares features that are common in other conditions (diffuse bilateral shadowing on CXR in the absence of raised left atrial pressure, hypoxaemia, impaired lung compliance).

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Apr 3, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Critical care and emergency medicine

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