Perfusion indices revisited

Table 1 Perfusion indices: evidence and disadvantages

Measure	Evidence	Disadvantages
Lactate	Meta-analysis	Needs blood sampling Laboratory time Could be elevated in other conditions than shock
ScvO₂	RCT	Needs central catheter Less useful under anesthesia
P (v-a) CO₂	Cohort	Needs central catheter Needs blood sampling Laboratory time
Temperature gradients	Cohort	T _c-toe is affected by hypothermia and room temperature
LV strain	Cohort	Needs expert operator
Skin mottling	Cohort	Limited value in burns, amputations, and in dark skin
Capillary refill time	Cohort	Index CRT: inter-rater variability Knee CRT: limited value in dark skin
PPI	Cohort	Needs an expensive device and electrodes
StO₂	Cohort	Needs NRIS and electrodes Less accurate in septic shock Less accurate in early shock stages
Ptco₂	Cohort	Needs special monitor and electrodes No definitive cutoff value
OCT	RCT	Needs special monitor and electrodes Restricted to intubated patients
Sublingual microcirculation	Cohort	Needs special device

CRT capillary refill time, LV left ventricular, NRIS near-infrared spectroscopy, OCT oxygen challenge test, Ptco ₂ subcutaneous partial oxygen pressure, PPI peripheral perfusion index, P (v-a) CO ₂ central-venous-arterial oxygen gradient, RCT randomized controlled trial, ScvO ₂ central venous oxygen saturation, StO ₂ tissue oxygen saturation, T _c-toe central-to-toe temperature gradient, T _skin-diff temperature gradient between fingertip and forearm