Critical Care Flashcards
What is the function of a chronotrope?
To increase the heart rate
What is the function of an inotrope?
To increase the contractile force of the cardiac muscle, thereby increasing stroke volume
What is the function of a vasopressor?
Constrict the arterial tree, increasing systemic vascular resistance
Where are alpha1 adrenergic receptors located, and what is their function?
Located in vascular smooth muscle, hence activation causes vasoconstriction
Also located in heart, and increases duration of contraction without increasing chronotropy
Where are beta adrenergic receptors located?
Beta1 in the heart, increasing inotropy and chronotropy without vasoconstriction
Beta2 in blood vessels and cause vasodilation
Where are dopamine receptors located and what is their function?
In renal, splanchnic (mesenteric), coronary, cerebral vascular beds.
Induces vasodilation
Second subtype causes vasoconstriction by inducing norepinephrine release
What receptors does adrenalin act on, and therefore what are its effects and uses?
Beta 1- adrenaline acts strongly on this receptor to increase inotropy and chronotropy
Beta 2, alpha 1- adrenaline acts moderately on these receptors
Used in anaphylaxis and second line in septic shock
What receptors does dobutamine act on and what effect does it have?
Beta 1 and beta 2- increases inotropy and chronotropy, reduces LV filling pressure
Has no vasopressor effects as has no action on alpha 1 receptors
What receptors does noradrenaline act on and what effect does it have?
Alpha 1 and beta 1 receptors
Producing vasoconstriction and inotropic effects
At low doses, a reflex bradycardia in response to increased mean arterial pressure, which cancels out the mild chronotropic effect and therefore there is no increase in heart rate!
What receptors does phenylephrine act on and what effect does it have?
Alpha 1 only
So purely vasoconstriction!
In septic shock, which is the first line vasoactive agent?
Noradrenalin
As it causes vasoconstriction to counteract the vasodilation from sepsis
Pure vasoconstriction alone can cause reflex bradycardia and reduce cardiac output, so the inotropic effects of noradrenalin helps to counteract this.
The inotropic effects of noradrenalin also helps to counteract the decrease in cardiac function which typically occurs in septic shock
What vasoactive drug is first line in anaphylactic shock?
Adrenalin
Vasopressin is second agent
What vasoactive drug is used in neurogenic shock?
Phenylephrine as it has purely vasoconstriction effects
What is the most appropriate vasoactive drug in cardiogenic shock
Norepinephrine
After establishing adequate perfusion, dobutamine can be added, as it is a potent inotropic drug, and it’s effects on beta 2 receptors causes vasodilation, so the heart has less pressure to pump against
What is a level 0 patient?
A patient whose needs can be met through normal ward care - eg observations greater than four hourly
What is a level 1 patient?
A patient at risk of their condition deteriorating, or recently discharged from a higher level of care.
Patients requiring additional monitoring <4 hour obs, clinical interventions or advice from critical care outreach.
What is a level 2 patient?
Patients needing pre-operative optimisation or extended postoperative care.
Patients stepping down from level 3 care.
Patients requiring single organ support! Greater than 50% oxygen or NiV Vasoactive drugs/CVP monitoring Renal replacement therapy ICP monitoring Dermatological support - burns
This is achieved on HDU
What is a level 3 patient?
Patients requiring advanced respiratory support alone - invasive mechanical ventilation
Patients requiring more than one organ supported
This is achieved on ICU
What are some early complications of endotracheal intubation?
Trauma to mouth, teeth etc Aspiration of stomach contents Tube malposition Airway obstruction Hypoxia from prolonged attempts
What are some late complications of endotracheal intubation?
Infection
Mucosal damage to mouth or trachea from cuff pressure
Injury to vocal cords
Tracheal stenosis
What are early complications of tracheostomy?
Haemorrhage Pneumothorax Tube misplacement Surgical emphysema Blockage with secretions Stomal infections Mucosal ulceration or perforations Tracheoeseophageal fistula
What are late complications of tracheostomy?
Late haemorrhage Tracheal granulomata Tracheal stenosis Scarring persistent sinus Tracheal necrosis
What precautions and monitoring should be taken when using vasoactive drugs?
Administered by central venous catheter
Haemodynamic monitoring via arterial and central venous catheters
How can death be defined?
The irreversible loss of the capacity to breath combined with the irreversible loss of the capacity for consciousness
These capacities reside in the brainstem, in the medulla and reticular activating system respectively
Can brainstem dead patients move?
Yes!
They may demonstrate residual limb movement due to intact spinal cord reflexes.
These do not require intact higher centres.
What are the cardiovascular criteria for diagnosing death?
The simultaneous and irreversible onset of apnoea and unconsciousness in the absence of a circulation
AND
The individual meets the criteria for not attempting CPR
OR
Attempts at CPR have failed
OR
Life sustaining treatments have been withdrawn in the best interests of the patient
How can you assess if the patient meets the cardiovascular criteria for death?
The individual should be observed for a minimum of five mins
Absence of central pulse on palpation
Absence of heart sounds on auscultation
No cardiac activity on ECG, echo etc
If continuous cardio respiratory arrest for five mins, move on to assess pupillary light reflexes, corneal reflexes, motor response to supra-orbital pressure
Why conditions must be excluded to diagnose brainstem death?
Must be due to irreversible brain damage of known aetiology!
Exclude reversible causes of coma:
Depressant drugs
Hypothermia- core temp above 34 deg
Metabolic/endocrine disturbance
Exclude reversible causes of apnoea:
Neuromuscular blockers
High cervical cord injury
What five brainstem reflexes can be used to exclude brainstem death?
The pupils are fixed and non responsive to light
There is no corneal reflex
Absent oculo-vestibular reflexes
No motor response to supra orbital pressure
No gag reflex/cough reflex
Basically all the cranial nerve reflexes!
What is the apnoea test for the diagnosis of brain stem death?
Assessing the respiratory response of the brainstem to hypercapnoea
Do not perform if previous tests have suggested brainstem activity!
Set fi02 to 1.0
Commence apnoiec oxygenation
If no response, check ABG has demonstrated paCO2 has risen by 0.5kpa
Then reconnect ventilator
At what age are the adult criteria for brainstem death applied?
Over 2 months
How many doctors are needed to assess brain stem death
Two, both registered for five years
At least one consultant
No members of the transplant team
How many times must the tests for brainstem death be repeated?
Twice
At what point when diagnosing death in a brain stem dead patient is the legal time of death confirmed?
The legal time of death is the time at which the first set of tests is completed
What are the physiological causes of type 1 respiratory failure?
Ventilation perfusion mismatch Due to either: Under ventilated alveoli Venous blood bypasses ventilated alveoli (right to left cardiac shunts) Low inspired oxygen fraction Low barometric pressure
What are the physiological causes of type 2 respiratory failure?
Reduced central respiratory drive
Hypo ventilation due to abnormalities of motor nerves, muscles, chest wall, spinal cord
Abnormalities of airways and lungs
What is acute respiratory distress syndrome?
A common condition which can affect all adult patients.
It occurs when non cardiogenic pulmonary oedema (secondary to acute damage to the alveoli ) leads to respiratory failure
What is the diagnostic criteria for ARDS?
Three things
Acute onset after lung injury
CXR shows bilateral infiltrates
Refractory hypoxaemia: pa02 : fiO2 ratio is less than 200
How is ARDS managed?
CPAP may be effective, but usually mechanical ventilation is required
