What, why and how to monitor blood glucose in critically ill patients

Table 2 Comparison between arterial and capillary monitoring of glucose

	Arterial	Capillary
Accuracy	As accurate as laboratory testing	Accuracy affected by poor perfusion states, pH, anaemia, renal failure, and high oxygen tension levels (old generation glucose oxidase based glucometers)
		Overestimation in all glucose range, especially in hypoglycaemic range
Sample volume	0.25-1 mL (can be more depends on method)	Minimal
Other variables	Simultaneous measurement of electrolytes, haemoglobin, and blood gases (partial pressure of oxygen and carbon dioxide, pH)	Single variable measured is sugar
Pain	Arterial sampling required	Repeated pin prick may cause patient discomfort
	Convenient in patients with indwelling arterial line
Need of expertise	Needs arterial line or arterial sampling which needs expertise	Simple finger stick, no expertise needed