Pulse contour techniques for perioperative hemodynamic monitoring: A nationwide carbon footprint and cost estimation.

BACKGROUND: The question of environmentally sustainable perioperative medicine represents a new challenge in an era of cost constraints and climate crisis. The French Society of Anaesthesia and Intensive Care (SFAR) recommends stroke volume optimization in high-risk surgical patients. Pulse contour techniques have become increasingly popular for stroke volume monitoring during surgery. Some require the use of specific disposable pressure transducers (DPTs), whereas others can be used with standard DPTs. OBJECTIVE: Quantify and compare the carbon footprint and cost of pulse contour techniques using specific and standard DPTs on a yearly basis and at a national level. METHODS: We estimated the number of high-risk surgical patients monitored every year in France with a pulse contour technique, and the plastic waste, carbon footprint and cost associated with the use of specific and standard DPTs. MAIN FINDINGS: When compared to pulse contour techniques working with a standard DPT, techniques requiring a specific DPT are responsible for an increase in carbon dioxide emission estimated at 65-83 tons/yr and for additional hospital cost estimated at €67 million/yr. If, as recommended by the SFAR, all high-risk surgical patients were monitored, the difference would reach 179-227 tons/yr for the environmental impact and €187 million/yr for the economic impact. CONCLUSION: From an environmental and economic standpoint, pulse contour techniques working with standard DPTs should be recommended for the perioperative hemodynamic monitoring of high-risk surgical patients.

Preload-adjusted left ventricular dP/dtmax: a sensitive, continuous, load-independent contractility index.

The classical indicators of left ventricular (LV) performances have been derived from pressure-volume (PV) and stroke work-volume plots obtained during various loading or pharmacological interventions. More recently, the preload-adjusted maximal change in pressure over time (PAdP/dtmax), derived from single beat PV analysis, has been shown to reflect the LV systolic performance accurately in varying conditions of inotropy and afterload. The objective of this study was to address whether PAdP/dtmax is a valid indicator of LV function in the setting of large preload variations, compared with the classical dP/dtmax-end-diastolic volume (EDV) and stroke work-EDV (preload recruitable stroke work) relationships. Nine anaesthetized and mechanically ventilated rats were instrumented with a ventricular conductance catheter. Stepwise preload reduction was achieved by repeated blood withdrawals (up to a total of 5 ml). Steady-state and dynamic PV loops were recorded during brief occlusion of the inferior vena cava, and LV function parameters were derived from these recordings. Our results demonstrate that PAdP/dtmax behaved in a similar manner to preload recruitable stroke work, reflecting well-maintained LV contractility during controlled haemorrhage until mean arterial pressure decreased below 40 mmHg. In contrast, dP/dtmax-EDV increased significantly and exhibited a curvilinear response that was associated with a large inter- and intra-animal variability. In a model of acute preload reduction, PAdP/dtmax was found to be the best indicator of systolic LV function. Given its simplicity, this real-time index derived from single beat analysis should be tested further in clinical settings.

Adverse effects of methylene blue on the central nervous system.

BACKGROUND: An increasing number of clinical observations suggest adverse neurologic outcome after methylene blue (MB) infusion in the setting of parathyroid surgery. Hence, the aim of the current study was to investigate the potentially neurotoxic effects of MB using a combination of in vivo and in vitro experimental approaches. METHODS: Isoflurane-anesthetized adult rats were used to evaluate the impact of a single bolus intravascular administration of MB on systemic hemodynamic responses and on the minimum alveolar concentration (MAC) of isoflurane using the tail clamp test. In vivo, MB-induced cell death was evaluated 24 h after MB administration using Fluoro-Jade B staining and activated caspase-3 immunohistochemistry. In vitro, neurotoxic effects of MB were examined in hippocampal slice cultures by measuring excitatory field potentials as well as propidium iodide incorporation after MB exposure. The impact of MB on dendritic arbor was evaluated in differentiated single cell neuronal cultures. RESULTS: Bolus injections of MB significantly reduced isoflurane MAC and initiated widespread neuronal apoptosis. Electrophysiologic recordings in hippocampal slices revealed a rapid suppression of evoked excitatory field potentials by MB, and this was associated with a dose-dependent effect of this drug on cell death. Dose-response experiments in single cell neuronal cultures revealed that a 2-h-long exposure to MB at non-cell-death-inducing concentrations could still induce significant retraction of dendritic arbor. CONCLUSIONS: These results suggest that MB exerts neurotoxic effects on the central nervous system and raise questions regarding the safety of using this drug at high doses during parathyroid gland surgery.

Operative mortality and respiratory complications after lung resection for cancer: impact of chronic obstructive pulmonary disease and time trends.

BACKGROUND: Smoking is a common risk factor for chronic obstructive pulmonary disease (COPD), cardiovascular disease, and lung cancer. In this observational study, we examined the impact of COPD severity and time-related changes in early outcome after lung cancer resection. METHODS: Over a 15-year period, we analyzed an institutional registry including all consecutive patients undergoing surgery for lung cancer. Using the receiver-operating characteristic (ROC) curve, we analyzed the relationship between forced expiratory volume in 1 second (FEV1) and postoperative mortality and respiratory morbidity. Multiple regression analysis has also been applied to identify other risk factors. RESULTS: A preoperative FEV1 less than 60% was a strong predictor for respiratory complications (odds ratio [OR] = 2.7, confidence interval [CI]: 1.3 to 6.6) and 30-day mortality (OR = 1.9, CI: 1.2 to 3.9), whereas thoracic epidural analgesia was associated with lower mortality (OR = 0.4; CI: 0.2 to 0.8) and respiratory complications (OR = 0.6; CI: 0.3 to 0.9). Mortality was also related to age greater than 70 years, the presence of at least three cardiovascular risk factors, and pneumonectomy. From the period 1990 to 1994, to 2000 to 2004, we observed significant reductions in perioperative mortality (3.7% versus 2.4%) and in the incidence of respiratory complications (18.7% versus 15.2%), that was associated with a higher rate of lesser resection (from 11% to 17%, p < 0.05) and increasing use of thoracic epidural analgesia (from 65% to 88%, p < 0.05). CONCLUSIONS: Preoperative FEV1 less than 60% is a main predictor of perioperative mortality and respiratory morbidity. Over the last 5-year period, diagnosis of earlier pathologic cancer stages resulting in lesser pulmonary resection as well as provision of continuous thoracic epidural analgesia have contributed to improved surgical outcome.

The effects of beta1-adrenergic blockade on cardiovascular oxygen flow in normoxic and hypoxic humans at exercise.

At exercise steady state, the lower the arterial oxygen saturation (SaO(2)), the lower the O(2) return (QvO(2)). A linear relationship between these variables was demonstrated. Our conjecture is that this relationship describes a condition of predominant sympathetic activation, from which it is hypothesized that selective beta1-adrenergic blockade (BB) would reduce O(2) delivery (QaO(2)) and QvO(2). To test this hypothesis, we studied the effects of BB on QaO(2) and QvO(2) in exercising humans in normoxia and hypoxia. O(2) consumption VO(2), cardiac output Q, CO(2) rebreathing), heart rate, SaO(2) and haemoglobin concentration were measured on six subjects (age 25.5 +/- 2.4 years, mass 78.1 +/- 9.0 kg) in normoxia and hypoxia (inspired O(2) fraction of 0.11) at rest and steady-state exercises of 50, 100, and 150 W without (C) and with BB with metoprolol. Arterial O(2) concentration (CaO(2)), QaO(2) and QvO(2) were then computed. Heart rate, higher in hypoxia than in normoxia, decreased with BB. At each VO(2), Q was higher in hypoxia than in normoxia. With BB, it decreased during intense exercise in normoxia, at rest, and during light exercise in hypoxia. SaO(2) and CaO(2) were unaffected by BB. The QaO(2) changes under BB were parallel to those in Q.QvO(2) was unaffected by exercise in normoxia. In hypoxia the slope of the relationship between QaO(2) and VO(2) was lower than 1, indicating a reduction of QvO(2) with increasing workload. QvO(2) was a linear function of SaO(2) both in C and in BB. The line for BB was flatter than and below that for C. The resting QvO(2) in normoxia, lower than the corresponding exercise values, lied on the BB line. These results agree with the tested hypothesis. The two observed relationships between QvO(2) and SaO(2) apply to conditions of predominant sympathetic or vagal activation, respectively. Moving from one line to the other implies resetting of the cardiovascular regulation.