Hypothermia Post Cardiac Surgery

OVERVIEW

• common
• multi-factorial: residual hypothermia post CPB, failure to rewarm, open thoracic cavity, cold OT, administration of cold fluids

CARDIOVASCULAR

• increased Q -> fall in Q when T poor peripheral perfusion
• increased myocardial ischaemia and infarction (catecholamine release mediated)
• increased arrhythmia (AF and VT)
• hypotension on warming because of vasodilation

RESPIRATORY

• increased chance of laryngospasm
• increased O2 demand (shivering)
• shift of oxygen-Hb dissociation curve to left -> decreased O2 off loading
• bronchodilation -> increased dead space, decreased hypoxic pulmonary vasoconstriction
• longer time on mechanical ventilation

CENTRAL NERVOUS SYSTEM

• decreased sensitivity to hypoxia and hypercapnoea
• increased sensitivity to opioids and sedatives
• decreased LOC (agitation and confusion)
• decreased cerebral function
• decreased protection of airway

NEUROMUSCULAR

• increased duration of action of; NMBD, volatiles (increase in tissue solubility), propofol and fentanyl
• increased shivering and shiver like tremor (thermal discomfort) -> increased metabolic rate, myocardial work, oxygen consumption

RENAL

• polyria (electrolyte loss)
• decreased ADH
• decreased RBF and GRF

HAEMATOLOGICAL

• coagulation and increased blood loss – reduced number of platelet activators, release of circulating anti-coagulants
• fibrinolysis -> increased bleeding and transfusion risk
• increased viscosity -> increased VTE risk, poor microcirculation perfusion

METABOLIC

• hyperglycaemia (decrease peripheral utilisation of glucose)
• acidosis from poor peripheral perfusion

INFECTIONS/WOUND

• increase in wound infections
• vasoconstriction -> decreased O2 supply, impairs immune function
• slow wound healing

HEPATIC

• decreased hepatic blood flow
• decreased enzyme activity
• slower drug metabolism

RESOURCE ALLOCATION

• longer ICU stay

References and Links

LITFL

• CCC – Haemorrhage post-cardiac surgery
• CCC – Hypertension post-cardiac surgery
• CCC – Hypotension post-cardiac surgery
• CCC – Hypoxaemia post-cardiac surgery