The use of peripheral perfusion index as a predictor for patient’s response to deliberate hypotension during functional endoscopic sinus surgery. A prospective observational study

Figures & data

Table 1. Patients and surgery characteristics. Values are means (SD), median (range) or number.

Variable	Values
Weight (kg) Age (years)	67.2 (7.1) 27 (18–53)
Gender (male/female)	22/25
Duration of surgery (min)	89.4 (31.6)
Duration of anesthesia (min)	131.6 (34.3)

Table 2. Comparison of the area under the curve (AUC) of peripheral perfusion index (PPI) at different time interval to predict the nitroglycerin dose requirement to reach the target mean arterial blood pressure.

PPI	AUC	95% CI	PPI cut-off value	Sensitivity (%)	Specificity (%)	+ve	-ve	P value
PPI (T0)	0.85	0.71–0.94	2.8	69.5	100	100	75	<0.0001
PPI (T1)	0.59	0.34–0.72	9.4	21.7	95.4	83.3	53.8	< 0.87
PPI (T2)	0.59	0.43–0.73	6.2	78	50	62	68.7	< 0.27
PPI (T3)	0.55	0.40–0.70	4.5	39	77	64.3	54.8	< 0.49

PPI (T0): Baseline; PPI (T1): PPI at one minute after induction; PPI (T2): PPI at one minute after endotracheal intubation; PPI (T3): PPI just before initiation of nitroglycerin infusion; CI: confidence interval; +ve: positive predictive value, -ve: negative predictive value.

Figure 1. Receiver operating characteristic curve comparing the predictive ability of peripheral perfusion index (PPI) at different time interval to the patients’ response to nitroglycerin-induced hypotension. PPI (T0) = baseline PPI, PPI (T1) = PPI at one minute after induction, PPI (T2) = PPI at one minute after intubation, PPI (T3) = PPI just before initiation of nitroglycerin infusion.

Table 3. Comparison between patient with low and high baseline peripheral perfusion index (PPI). Values are means (SD).

Variable	All patients (n = 47)	Low PPI ≤ = 2.8 (n = 27)	High PPI > 2.8 (n = 20)	P value
Baseline PPI	2.45 (1.89)	1.08 (0.33)	3.75 (1.85)
Mean nitroglycerin infusion rate (µg/kg/min)	1.39 (1.09)	0.69 (0.29)	2.07 (1.15)	p < 0.0001
Total nitroglycerin consumption (mg)	8.31 (7.91)	3.45 (2.48)	12.96 (8.55)	p < 0.0001
Time to reach target mean arterial pressure (min)		6.3 (3.3)	24.4 (14.4)	P < 0.0001

Figure 2. Intraoperative changes of perfusion index. T0; baseline, T1: after induction, T2: before endotracheal intubation, T3: before nitroglycerin infusion, Intraoperative PPI values (10–60 min): Values are means and error bars represent the standard deviation. * Denotes significant difference between the two subgroups. † Denotes significance relative to the baseline value.