Daily Anesthesiology Research Analysis

BACKGROUND: Chronic neuropathic pain generally has a poor response to treatment with conventional drugs. Sympathectomy can alleviate neuropathic pain in some patients, suggesting that abnormal sympathetic-somatosensory signaling interactions might underlie some forms of neuropathic pain. The molecular mechanisms underlying sympathetic-somatosensory interactions in neuropathic pain remain obscure. METHODS: Lumbar sympathectomy was performed in spared nerve injury (SNI) mice or rats, and the up-down method was used to measure the mechanical paw withdrawal threshold. Dorsal root ganglia (DRG) injection and perfusion were used to deliver virus or drugs. Methylated RNA immunoprecipitation sequencing, RNA-sequencing, and immunoelectron microscopy were used to identify neurotransmitters. RESULTS: We found that sprouting tyrosine hydroxylase-positive sympathetic fibres in DRG mediated the maintenance of mechanical allodynia after SNI (day 28, P<0.001). We further found that SNI significantly increased the N

BACKGROUND: Long-term controlled mechanical ventilation in the intensive care unit induces ventilator-induced diaphragm dysfunction (VIDD). The transition from controlled mechanical ventilation to assisted mechanical ventilation is a challenge that requires clinicians to balance overassistance and underassistance. While the effects of overassistance on the diaphragm are well known, the authors aimed to assess the impact of underassistance on diaphragm function and structure in a piglet model with preexisting VIDD (after long-term controlled mechanical ventilation) or without VIDD (short-term controlled mechanical ventilation). METHODS: Twenty-two Large White female piglets were anesthetized, ventilated, and separated into two groups: a VIDD group (n = 10) with long-term 72-h controlled mechanical ventilation, and a no-VIDD group (n = 12) with short-term 2-h controlled mechanical ventilation. After sedation reduction at the end of the controlled mechanical ventilation period, each piglet was switched to underassisted ventilation for 2 h. Diaphragm function (supramaximal diaphragm pressure-generating capacity assessed by negative tracheal pressure after transvenous phrenic nerve stimulation) and diaphragm structure (mini-invasive in vivo biopsies) were assessed before and after underassisted ventilation. RESULTS: In the VIDD group, supramaximal diaphragm pressure-generating capacity decreased by 22% from (mean ± SD) 69.9 ± 12.7 to 54.9 ± 19.7 cm H 2 O ( P = 0.04) after 72 h of controlled mechanical ventilation evidencing VIDD, then dropped by a further 29% from 54.9 ± 19.7 to 38.9 ± 15.5 cm H 2 O ( P < 0.01) after 2 h of underassisted ventilation. Diaphragm pressure-generating capacity remains stable from 55.3 ± 22.7 to 58.2 ± 24 cm H 2 O ( P = 0.24) in the no-VIDD group. Diaphragm structure showed that sarcomeric injuries increase from 13 ± 10% to 24 ± 19% ( P < 0.01) and lipid droplets decrease from 14 ± 8% to 11 ± 6% ( P = 0.03) of the total micrograph area after 2 h of underassisted ventilation in the VIDD group. Sarcomeric injuries and lipid droplets accounted, respectively, for 17 ± 16% and 2 ± 3% of the total micrograph area after underassisted ventilation in the no-VIDD group. CONCLUSIONS: In this porcine model, a short 2-h exposure of underassisted ventilation induces impairment of diaphragm function with damage to the diaphragm structure in intensive care unit condition with preexisting VIDD.

INTRODUCTION: Assessment of functional capacity is an essential part of peri-operative risk stratification. Subjective functional capacity is easier to examine than objective tests of patient fitness. However, the association between subjective functional capacity and postoperative outcomes has not been established. METHODS: Four databases were searched for studies describing the associations between subjective functional capacity and postoperative outcomes in adults undergoing non-cardiac surgery. Meta-analysis was conducted among studies where functional capacity was expressed in metabolic equivalents. The primary outcome was postoperative major adverse cardiovascular events. Secondary outcomes were mortality and postoperative overall complications. We estimated the ORs of the outcomes in patients with poor functional capacity (< 4 metabolic equivalents) as compared with those with good functional capacity (≥ 4 metabolic equivalents). Random-effects models were used for the meta-analysis. RESULTS: We identified 7835 abstracts. After screening and a full-text review, 23 studies were selected. Evaluation methods of functional capacity included: questionnaires (n = 7); specific questions (n = 6); and subjective assessment by anaesthetists (n = 5). The probability of major postoperative adverse cardiovascular events was significantly higher in patients with poor functional capacity (OR 1.84, 95%CI 1.62-2.08) than in those with good functional capacity. Patients with poor functional capacity also had higher odds of mortality (OR 2.48, 95%CI 1.45-4.25) and postoperative complications (OR 1.85, 95%CI 1.34-2.55). DISCUSSION: Subjective functional capacity of < 4 metabolic equivalents was associated with postoperative complications including cardiovascular events and other serious outcomes. The results need to be interpreted with caution due to the diverse measures used to assess functional capacity.