Effects of manual and syringe pump induction of total intravenous anaesthesia on propofol waste: a single-centre retrospective analysis

Abstract

Background: Propofol accounts for a substantial proportion of medication waste. Evidence-based waste reduction methods are scarce.

Methods: In a retrospective analysis of 331 procedures, the total propofol waste per surgery was compared between manual and syringe pump induction of anaesthesia during total intravenous anaesthesia (TIVA), with a syringe pump used to maintain TIVA after induction. The secondary endpoint was the amount of propofol administered. Subgroup analyses examined the influence of biological sex, age, weight or BMI, American Society of Anesthesiologists (ASA) physical status, substance use, and anaesthesia duration on propofol waste.

Results: Syringe pump induction was associated with 32.8% less waste of propofol (P<0.001); this effect was most pronounced in procedures lasting 20-60 min (up to 46.9% less in procedures lasting 20-40 min, P<0.001) and 80-120 min (up to 48.8% less in procedures lasting 100-120 min, P=0.003). The amount of waste was not affected by biological sex, age, weight, BMI, or ASA physical status. Syringe pump induction was consistently associated with less waste, except in patients with obesity. Patients with active substance use had 27.6% more waste with manual induction (P=0.031) but not with syringe pump induction. In patients with and without active substance use, syringe pump induction resulted in less waste (substance use: 48.7% less, P=0.0015; without substance use: 22.7% less, P=0.0045).

Conclusions: Syringe pump induction reduced propofol waste during TIVA, regardless of patient characteristics. Manual induction using a separate syringe should be reconsidered from an environmental and economic viewpoint.

Clinical trial registration: DRKS00032518I.

Keywords: TIVA; climate change; economic anaesthesia; green anaesthesia; propofol waste; substance use; sustainability; waste reduction.

Fig 1

(a) Comparison of propofol waste per surgery between manual (blue box-plot, mean 226 mg, median 220 mg, n=117) vs syringe pump induction (purple box-plot, mean 154 mg, median 140 mg, n=214): 32.8% less waste per surgery (P<0.0001 [∗∗∗∗]). (b) Waste per surgery (mg) in procedures of various durations; 20–40 min: 46.9% less waste (manual: mean 304 mg vs syringe pump: 161 mg, P<0.0001 [∗∗∗∗]); 40–60 min: 37.5% less waste (manual: mean 198 mg vs syringe pump: 124 mg, P=0.004 [∗∗]); 80–100 min: 32.9% less waste (manual: mean 217 mg vs syringe pump: 179 mg, P=0.03 [∗]); 100–120 min: 48.8% less waste (manual: mean 324 mg vs syringe pump: 166 mg, P=0.003 [∗∗]). All results are listed in Supplementary Table S1. (Box-plots indicate 25th and 75th percentiles with whiskers at the 10th and 90th percentiles. Median values are depicted as horizontal lines; mean values are presented as plus or dot in (a) and (b), respectively.).

Fig 2

Comparison of propofol waste per surgery (mg) between manual (blue box-plot) and syringe pump induction (purple box-plot) in patients with different BMIs (kg m⁻²). BMI<25 kg m⁻²: 37.8% less waste (manual: mean 237 mg, median 230 mg, n=51 vs syringe pump: mean 147 mg, median 150 mg, n=105, P<0.0001 [∗∗∗∗], unpaired t-test). Overweight: mean 28.9% less waste (manual: mean 237 mg, median 250 mg, n = 31 vs syringe pump: mean 168 mg median: 150 mg, n=63, P=0.014 [∗]). No difference in patients with obesity grade I and obesity grade ≥II (P=0.19 and 0.13, respectively). All results are listed in Supplementary Table S1 (box-plots indicate 25th and 75th percentiles with whiskers at the 10th and 90th percentiles. Median values are depicted as horizontal line; mean values are presented as plus).

Fig 3

(a) Comparison of propofol waste per surgery (mg) between manual (blue box-plot) and syringe pump induction (purple box-plot) in patients with and without (W/O) substance use. Manual induction: patients without substance use had 38% less waste (mean 200 mg, median 200 mg, n=91) than patients with substance use (mean 277 mg, median 310 mg, n=17, P=0.031 [∗]). No difference during syringe pump induction (W/O: mean 155 mg, median 150 mg, n=184 vs substance use: mean 142 mg, median 120 mg, n=29, P=0.17). In both groups, syringe pump induction revealed less waste (W/O: 22.7% less, P=0.0045 [∗∗] vs substance use: 48.7% less, P=0.0015 [∗∗]). (b) Induction dose per surgery (mg) was 18.5% higher in patients with substance use (mean 214 mg, median 200 mg, n=17) than in patients without use (mean 180 mg, median 180 mg, n=93, P=0.03 [∗]). All results are listed in Supplementary Table S1 (box-plots indicate 25th and 75th percentiles with whiskers at the 10th and 90th percentiles. Median values are depicted as horizontal line; mean values are presented as plus).