British journal of anaesthesia
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What's the deal?
This lab study from Zhong et al. challenges the assumption that low-flow anaesthesia is economically and environmentally superior during TIVA anaesthetics when volatile agents are not used.
What did they do?
Zhong used a test lung model with fixed CO2 inflow (250 ml/min) ventilated via circle systems of two anaesthetic machines (Dräger Primus and GE Aisys CS2). FGF rates of 1, 2, 4, and 6 L/min were tested, measuring the time to CO2 absorbent exhaustion (when inspired CO2 >0.3 kPa).
An inspired 30% O2/air mixture was used, with the test lung volume-control-ventilated at 12 bpm with 500 mL tidal volumes.
Findings
Results showed that increasing FGF from 1 to 6 L/min resulted in over 90% reduction in running costs with minimal net change to global warming potential. The time to absorbent exhaustion increased non-linearly with higher FGFs, taking over 5-8 days at 6 L/min. Notably, removing the CO2 absorbent entirely and using very high FGF (15-18 L/min) provided minimal additional economic benefit while more than doubling the environmental impact.
"We suggest that 'high-flow anaesthesia', with FGF around 6 L/min, is a viable cost-saving strategy when using a circle system for anaesthetic maintenance without inhalational anaesthetic agents in adults."
Hang-on...
The absolute cost saving (due to reduced soda lime consumption) was actually pretty small, being less than 4% of the total non-staff anaesthetic cost. Although this might still be economically significant when scaled across an entire health system, especially given the simplicity of implementation and the lack of drawback.
Bottom-line
When using total intravenous anaesthesia with modern HME filters, higher fresh gas flows (~6 L/min) are more cost-effective than traditional low-flow techniques, without compromising environmental impact or patient safety.
summary -
Randomized Controlled Trial Comparative Study
Effects of anaesthesia method and tourniquet use on recovery following total knee arthroplasty: a randomised controlled study.
Recovery after total knee arthroplasty was similar for spinal and general anaesthesia across broad post-operative indicators.
pearl -
Observational Study
MicroRNA signatures of perioperative myocardial injury after elective noncardiac surgery: prospective observational mechanistic cohort study.
Elevated plasma or serum troponin, indicating perioperative myocardial injury (PMI), is common after noncardiac surgery. However, underlying mechanisms remain unclear. Acute coronary syndrome (ACS) is associated with the early appearance of circulating microRNAs, which regulate post-translational gene expression. We hypothesised that if PMI and ACS share pathophysiological mechanisms, common microRNA signatures should be evident. ⋯ Circulating microRNAs associated with cardiac ischaemia were universally elevated in patients after surgery, independent of development of myocardial injury.