Critical Care Medicine - Introduction to ICU and ICU care

Question 1

Functions of the ICU

Answer 1

Monitoring of unstable patients

Provide intensive therapy and organ support, with intensive monitoring

Supportive treatment of organ failure before irreverisble EOD, buy time for recovery: e.g.
- Respiration: mechanical ventilation
- Cardiovascular: inotropes / vasopressors / aortic balloon pump
- Renal: renal replacement therapy- Liver failure: MARS

Question 2

Triage logic for ICU admission

Answer 2

Patients referred are assessed early as to need and suitability

Highest priority given to patients suffering from (potentially) reversible organ failures, commonly hypoxia and shock

Factors for consideration:
- Reversibility of active medical problem
- Clinical condition/ critical illness?
- Premorbid state: QoL, ADLs, Exercise tolerances
- Co-morbidities: malignant or non-malignant terminal diseases?
- Age

Question 3

Define the ICU priority scale

Answer 3

Priority I
Critically ill with organ failure(s) requiring support
e.g. Respiratory failure need Ventilation; Shock need Inotropes and vasopressors

Priority II
Same as priority Ill, but not requiring organ support
e.g. Respiratory failure need Oxygen supplementation; Shock need Fluid challenge

Priority III
Critically ill, with poor prognosis
e.g. Terminal illness, end-stage chronic disease, acute irreversible disease, very poor functional status

Question 4

Options for CVS support

Answer 4

Aim: Maintain adequate blood pressure for organ perfusion, Provide adequate cardiac output for the delivery of oxygen

Options:
- inotropes: dopamine, dobutamine, adrenaline, ephedrine
- chronotropes
- vasopressors: noradrenaline, pheylephrine, vasopressin
- pacemaker
- Intra-aortic balloon counterpulsation (IABP)
- Extracorporeal membrane oxygenation

Question 5

Options for renal support

Renal monitoring

Answer 5

Renal support:
* Haemodialysis, peritoneal dialysis
* Continuous renal replacement therapy/ Haemofiltration
* Fluid management
* Remove renal toxins
* Treat perfusion or outflow obstruction

Monitoring:
Clinical:
* Uraemic symptoms
* Urine output, fluid balance
* Urine microscopy

Biochemical:
* Acid base status, electrolytes, urea & creatinine
* Creatinine clearance

Indications include ARF, severe metabolic acidosis, hyperkalaemia, some poisonings

Question 6

Define DNR and use

Answer 6

Patients may progressively worsen despite treatment for the underlying disease(s)

Beyond a point, recovery is impossible and the patient may be said to be dying, the continuation of supportive treatment may delay the inevitable death

In such cases, resuscitation in the case of arrest is inappropriate and a Do Not Resuscitate order is initiated

Question 6

Terms for withdrawal of treatment in the ICU

Forms of withdrawal

Answer 6

Terms:
* On-going futile treatment is undesirable from both ethical and economic points of view
* Withdrawal of treatment allows the natural process of death to occur unimpeded by artificial organ support
* All treating physicians must be unanimous in agreement that this is an appropriate step
* Family members must be counseled until the family understand the concept and do not object

Forms of withdrawal:
* Withdrawal of Inotropes / Vasopressors
* Limiting blood products
* Limitation of Ventilator settings
* Stopping Renal Replacement Therapy

Question 7

General monitoring of ICU patients

Answer 7

• Posture/ appearance/ movement
• Neuromonitoring: GCS, EEG, Transcranial doppler, ICP
• Respiration: RR, breathing pattern, breath sounds
• Cardiac: BP, ECG, Arterial BP, CVP, Pulmonary artery catheter
• CVS: Fluid IO, Pulse oximeter, perfusion, peripheries

Question 8

Fluid monitoring in ICU

Metrics

Answer 8

Fluid IN:
* Volume
* Composition (determines distribution in the body)
* Rate
* Route of infusion
* Fluid intake and food intake

Fluid OUT:
* Urine
* Faeces. other GIT losses
* Insensible loss through respiration and skin
* Bleeding

Question 9

ECMO

• Types
• Function

Answer 9

2 forms of ECMO: veno-arterial (VA) and veno-venous (VV)
In both modalities, blood drained from the venous system is oxygenated outside of the body
- In VA ECMO, this blood is returned to the arterial system
- In VV ECMO the blood is returned to the venous system & no cardiac support is provided

Anticoagulants (heparin) are given to prevent blood clotting

Question 10

Pulse oximeter

• Function
• MoA
• Factors that affect accuracy

Answer 10

MoA:
- Pulse oximetry uses a light emitter with red and infrared LEDs that shines through a reasonably translucent site with good blood flow.
- Typical sites: finger, toe, pinna or lobe of the ear.
- Opposite the emitter is a photodetector that receives the light that passes through the measuring site.

Function: Measure SpO2 = (oxygenated Hb/ oxy + deoxy Hb) x 100

Inaccuracy:
- high concentration of metHb or carboxyHb, there will be a falsely high oxyHb estimate (SpO2).
- Hypotension
- Anaemia: Accurate down to Hb>3g/dl
- Skin pigmentation: False reduction with very dark skin & patient with hyperbilirubinaemia
- Nail polish: False reduction with blue or black colour

Question 11

Define type 1 and type 2 respiratory failure mechanisms

Answer 11

Type I Failure: Hypoxaemic Failure, Low PaO2
5 Mechanisms
* Hypoxia
* Hypoventilation
* Alveolo-Capillary Block
* Ventilation Perfusion Mismatch
* Shunting

Type II Failure: Hypercapneic Failure, High PaCO2
2 Major Mechanisms
- Hypoventilation: Muscular Weakness, Sedation/Hypnotics, Central Apnoea, Respiratory Muscles Fatigue
- Dead Space: COPD, obstructive lung diseases

Question 18

Risk of excessive oxygen supplementation

Answer 18

• Toxic Metabolites of Oxygen
  superoxide radical, hydrogen peroxide & hydroxyl radical damage cell membranes, denaturing proteins & breakdown DNA
• Activation of granulocytes (as part of the inflammatory response) involves a marked increase in O2 consumption
• Pulmonary O2 toxicity
  Can cause tracheobronchitis, ARDS, absorption atelectasis-> reduce vital capacity