Efficacy and safety of intraoperative controlled hypotension: a systematic review and meta-analysis of randomised trials.

BACKGROUND: Intraoperative controlled hypotension improves surgical field visibility by reducing blood loss (efficacy) but poses potential risks linked to organ hypoperfusion (safety). The use of controlled hypotension persists despite increasing evidence of associations between intraoperative inadvertent hypotension and adverse outcomes. Therefore, we tested the hypothesis that the focus and results of intraoperative controlled hypertension research differ across anaesthesia and surgery investigators because of differing priorities. METHODS: We systematically reviewed randomised trials comparing controlled hypotension with usual care with trials categorised by investigators' affiliation. RESULTS: We identified 48 eligible trials, of which 37 were conducted by anaesthesia investigators and 11 by surgery investigators. For the primary outcome, 54% of the anaesthesia-led trials focused on safety, whereas all (100%) surgery-led trials focused on efficacy (P=0.004). Compared with usual care, mean arterial pressure in controlled hypotension was 23% (95% confidence interval [CI] 17-29%) lower in anaesthesia trials and 30% (95% CI 14-37%) lower in surgery trials; estimated blood loss was 44% (95% CI 30-55%) less in anaesthesia trials and 38% (95% CI 30-49%) less in surgery trials. Overall, blood loss was reduced by 43% (95% CI 32-53%), and trial sequential analysis supported an efficacy conclusion. Mean arterial pressure and estimated blood loss reductions were associated (R2=0.41, P=0.002). All trials were underpowered for safety outcomes, and none adequately evaluated myocardial or renal injury. CONCLUSIONS: Anaesthesia researchers prioritised safety outcomes, whereas surgery researchers emphasised efficacy in controlled hypotension trials. Controlled hypotension significantly reduces blood loss. In contrast, safety outcomes were poorly studied. Given increasing observational evidence linking inadvertent hypotension to myocardial and renal injury, the safety of controlled hypotension remains to be addressed. SYSTEMATIC REVIEW PROTOCOL: PROSPERO (CRD42023450397).

Characteristics associated with effectiveness in postoperative delirium research: a systematic review of randomised controlled trials with meta-regression and meta-analysis.

BACKGROUND: Postoperative delirium remains prevalent despite extensive research through randomised trials aimed at reducing its incidence. Understanding trial characteristics associated with interventions' effectiveness facilitates data interpretation. METHODS: Trial characteristics were extracted from eligible trials identified through two systematic literature searches. Multivariable meta-regression was used to investigate trial characteristics associated with effectiveness estimated using odds ratios. Meta-analysis was used to investigate pooled effectiveness. RESULTS: We identified 201 eligible trials. Compared with China, trials from the USA/Canada (ratio of odds ratio, 1.89; 95% confidence interval, 1.45-2.45) and Europe/Australia/New Zealand (1.67; 1.29-2.18) had an 89% and 67% higher odds ratio, respectively, suggesting reduced effectiveness. The effectiveness was enhanced when the incidence of postoperative delirium increased (0.85; 0.79-0.92, per 10% increase). Trials with concerns related to deviations from intended interventions reported increased effectiveness compared with those at low risk (0.69; 0.53-0.90). Compared with usual care, certain interventions appeared to have reduced the incidence of postoperative delirium in low-risk trials with low-to-moderate certainty of evidence. However, these findings should be considered inconclusive because of challenges in grouping heterogeneous interventions, the limited number of eligible trials, the prevalence of small-scale studies, and potential publication bias. CONCLUSIONS: The effectiveness of postoperative delirium trials varied based on the region of trial origin, the incidence of delirium, and the risk of bias. The limitations caution against drawing definitive conclusions from different bodies of evidence. These findings highlight the imperative need to improve the quality of research on a global scale. SYSTEMATIC REVIEW PROTOCOL: PROSPERO (CRD42023413984).

Integrated Feedforward and Feedback Mechanisms in Neurovascular Coupling.

Neurovascular coupling (NVC) is the mechanism that drives the neurovascular response to neural activation, and NVC dysfunction has been implicated in various neurologic diseases. NVC is driven by (1) nonmetabolic feedforward mechanisms that are mediated by various signaling pathways and (2) metabolic feedback mechanisms that involve metabolic factors. However, the interplay between these feedback and feedforward mechanisms remains unresolved. We propose that feedforward mechanisms normally drive a swift, neural activation-induced regional cerebral blood flow (rCBF) overshoot, which floods the tissue beds, leading to local hypocapnia and hyperoxia. The feedback mechanisms are triggered by the resultant hypocapnia (not hyperoxia), which causes cerebral vasoconstriction in the neurovascular unit that counterbalances the rCBF overshoot and returns rCBF to a level that matches the metabolic activity. If feedforward mechanisms function improperly (eg, in a disease state), the rCBF overshoot, tissue-bed flooding, and local hypocapnia fail to occur or occur on a smaller scale. Consequently, the neural activation-related increase in metabolic activity results in local hypercapnia and hypoxia, both of which drive cerebral vasodilation and increase rCBF. Thus, feedback mechanisms ensure the brain milieu's stability when feedforward mechanisms are impaired. Our proposal integrates the feedforward and feedback mechanisms underlying NVC and suggests that these 2 mechanisms work like a fail-safe system, to a certain degree. We also discussed the difference between NVC and cerebral metabolic rate-CBF coupling and the clinical implications of our proposed framework.

Noradrenaline-induced changes in cerebral blood flow in health, traumatic brain injury and critical illness: a systematic review with meta-analysis.

BACKGROUND: Noradrenaline is a standard treatment for hypotension in acute care. The precise effects of noradrenaline on cerebral blood flow in health and disease remain unclear. METHODS: We systematically reviewed and synthesised data from studies examining changes in cerebral blood flow in healthy participants and patients with traumatic brain injury and critical illness. RESULTS: Twenty-eight eligible studies were included. In healthy subjects and patients without critical illness or traumatic brain injury, noradrenaline did not significantly change cerebral blood flow velocity (-1.7%, 95%CI -4.7-1.3%) despite a 24.1% (95%CI 19.4-28.7%) increase in mean arterial pressure. In patients with traumatic brain injury, noradrenaline significantly increased cerebral blood flow velocity (21.5%, 95%CI 11.0-32.0%), along with a 33.8% (95%CI 14.7-52.9%) increase in mean arterial pressure. In patients who were critically ill, noradrenaline significantly increased cerebral blood flow velocity (20.0%, 95%CI 9.7-30.3%), along with a 32.4% (95%CI 25.0-39.9%) increase in mean arterial pressure. Our analyses suggest intact cerebral autoregulation in healthy subjects and patients without critical illness or traumatic brain injury., and impaired cerebral autoregulation in patients with traumatic brain injury and who were critically ill. The extent of mean arterial pressure changes and the pre-treatment blood pressure levels may affect the magnitude of cerebral blood flow changes. Studies assessing cerebral blood flow using non-transcranial Doppler methods were inadequate and heterogeneous in enabling meaningful meta-analysis. CONCLUSIONS: Noradrenaline significantly increases cerebral blood flow in humans with impaired, not intact, cerebral autoregulation, with the extent of changes related to the severity of functional impairment, the extent of mean arterial pressure changes and pre-treatment blood pressure levels.

Evaluation of a modified ultrasound-assisted technique for mid-thoracic epidural placement: a prospective observational study.

BACKGROUND: Although mid-thoracic epidural analgesia benefits patients undergoing major surgery, technical difficulties often discourage its use. Improvements in technology are warranted to improve the success rate on first pass and patient comfort. The previously reported ultrasound-assisted technique using a generic needle insertion site failed to demonstrate superiority over conventional landmark techniques. A stratified needle insertion site based on sonoanatomic features may improve the technique. METHODS: Patients who presented for elective abdominal or thoracic surgery requesting thoracic epidural analgesia for postoperative pain control were included in this observational study. A modified ultrasound-assisted technique using a stratified needle insertion site based on ultrasound images was adopted. The number of needle passes, needle skin punctures, procedure time, overall success rate, and incidence of procedure complications were recorded. RESULTS: One hundred and twenty-eight subjects were included. The first-pass success and overall success rates were 75% (96/128) and 98% (126/128), respectively. In 95% (122/128) of patients, only one needle skin puncture was needed to access the epidural space. The median [IQR] time needed from needle insertion to access the epidural space was 59 [47-122] seconds. No complications were observed during the procedure. CONCLUSIONS: This modified ultrasound-assisted mid-thoracic epidural technique has the potential to improve success rates and reduce the needling time. The data shown in our study may be a feasible basis for a prospective study comparing our ultrasound-assisted epidural placements to conventional landmark-based techniques.

Causes of Perioperative Cardiac Arrest: Mnemonic, Classification, Monitoring, and Actions.

Perioperative cardiac arrest (POCA) is a catastrophic complication that requires immediate recognition and correction of the underlying cause to improve patient outcomes. While the hypoxia, hypovolemia, hydrogen ions (acidosis), hypo-/hyperkalemia, and hypothermia (Hs) and toxins, tamponade (cardiac), tension pneumothorax, thrombosis (pulmonary), and thrombosis (coronary) (Ts) mnemonic is a valuable tool for rapid differential diagnosis, it does not cover all possible causes leading to POCA. To address this limitation, we propose using the preload-contractility-afterload-rate and rhythm (PCARR) construct to categorize POCA, which is comprehensive, systemic, and physiologically logical. We provide evidence for each component in the PCARR construct and emphasize that it complements the Hs and Ts mnemonic rather than replacing it. Furthermore, we discuss the significance of utilizing monitored variables such as electrocardiography, pulse oxygen saturation, end-tidal carbon dioxide, and blood pressure to identify clues to the underlying cause of POCA. To aid in investigating POCA causes, we suggest the Anesthetic care, Surgery, Echocardiography, Relevant Check and History (A-SERCH) list of actions. We recommend combining the Hs and Ts mnemonic, the PCARR construct, monitoring, and the A-SERCH list of actions in a rational manner to investigate POCA causes. These proposals require real-world testing to assess their feasibility.

Classification and effectiveness of different oxygenation goals in mechanically ventilated critically ill patients: network meta-analysis of randomised controlled trials.

BACKGROUND: The optimal oxygenation in mechanically ventilated critically ill patients remains unclear. METHODS: We performed a systematic review of randomised controlled trials (RCTs) with the aim to classify oxygenation goals and investigate their relative effectiveness. RCTs investigating different oxygenation goal-directed mechanical ventilation in critically ill adult patients were eligible for the analysis. The trinary classification classified oxygenation goals into conservative (partial pressure of arterial oxygen (P aO2 ) 55-90 mmHg), moderate (P aO2 90-150 mmHg) and liberal (P aO2 >150 mmHg). The quadruple classification further divided the conservative goal from the trinary classification into far-conservative (P aO2 55-70 mmHg) and conservative (P aO2 70-90 mmHg) goals. The primary outcome was 30-day mortality. The secondary outcomes included intensive care unit, hospital and 90-day mortalities. The effectiveness was estimated by the relative risk and 95% credible interval (CrI) using network meta-analysis and visualised using surface under the cumulative ranking curve (SUCRA) scores and survival curves. RESULTS: We identified eight eligible studies involving 2532 patients. There were no differences between conservative and moderate goals (relative risk 1.08, 95% CrI 0.85-1.36; moderate quality), between moderate and liberal goals (relative risk 0.83, 95% CrI 0.61-1.10; low quality) or between conservative and liberal goals (relative risk 0.89, 95% CrI 0.61-1.30; low quality) based on the trinary classification. There were no differences in secondary outcomes among the different goals. The results were consistent between the trinary and quadruple classifications. The SUCRA scores and survival curves suggested that the moderate goal in the trinary and quadruple classifications and the conservative goal in the quadruple classification may be superior to the liberal and far-conservative goals. CONCLUSIONS: Different oxygenation goals do not lead to different mortalities in mechanically ventilated critically ill patients. The potential superiority of maintaining P aO2 in the range 70-150 mmHg remains to be validated.

Treatments Associated with Lower Mortality among Critically Ill COVID-19 Patients: A Retrospective Cohort Study.

BACKGROUND: Mortality in critically ill COVID-19 patients remains high. Although randomized controlled trials must continue to definitively evaluate treatments, further hypothesis-generating efforts to identify candidate treatments are required. This study's hypothesis was that certain treatments are associated with lower COVID-19 mortality. METHODS: This was a 1-yr retrospective cohort study involving all COVID-19 patients admitted to intensive care units in six hospitals affiliated with Yale New Haven Health System from February 13, 2020, to March 4, 2021. The exposures were any COVID-19-related pharmacologic and organ support treatments. The outcome was in-hospital mortality. RESULTS: This study analyzed 2,070 patients after excluding 23 patients who died within 24 h after intensive care unit admission and 3 patients who remained hospitalized on the last day of data censoring. The in-hospital mortality was 29% (593 of 2,070). Of 23 treatments analyzed, apixaban (hazard ratio, 0.42; 95% CI, 0.363 to 0.48; corrected CI, 0.336 to 0.52) and aspirin (hazard ratio, 0.72; 95% CI, 0.60 to 0.87; corrected CI, 0.54 to 0.96) were associated with lower mortality based on the multivariable analysis with multiple testing correction. Propensity score-matching analysis showed an association between apixaban treatment and lower mortality (with vs. without apixaban, 27% [96 of 360] vs. 37% [133 of 360]; hazard ratio, 0.48; 95% CI, 0.337 to 0.69) and an association between aspirin treatment and lower mortality (with vs. without aspirin, 26% [121 of 473] vs. 30% [140 of 473]; hazard ratio, 0.57; 95% CI, 0.41 to 0.78). Enoxaparin showed similar associations based on the multivariable analysis (hazard ratio, 0.82; 95% CI, 0.69 to 0.97; corrected CI, 0.61 to 1.05) and propensity score-matching analysis (with vs. without enoxaparin, 25% [87 of 347] vs. 34% [117 of 347]; hazard ratio, 0.53; 95% CI, 0.367 to 0.77). CONCLUSIONS: Consistent with the known hypercoagulability in severe COVID-19, the use of apixaban, enoxaparin, or aspirin was independently associated with lower mortality in critically ill COVID-19 patients.

Heterogeneous impact of hypotension on organ perfusion and outcomes: a narrative review.

Arterial blood pressure is the driving force for organ perfusion. Although hypotension is common in acute care, there is a lack of accepted criteria for its definition. Most practitioners regard hypotension as undesirable even in situations that pose no immediate threat to life, but hypotension does not always lead to unfavourable outcomes based on experience and evidence. Thus efforts are needed to better understand the causes, consequences, and treatments of hypotension. This narrative review focuses on the heterogeneous underlying pathophysiological bases of hypotension and their impact on organ perfusion and patient outcomes. We propose the iso-pressure curve with hypotension and hypertension zones as a way to visualize changes in blood pressure. We also propose a haemodynamic pyramid and a pressure-output-resistance triangle to facilitate understanding of why hypotension can have different pathophysiological mechanisms and end-organ effects. We emphasise that hypotension does not always lead to organ hypoperfusion; to the contrary, hypotension may preserve or even increase organ perfusion depending on the relative changes in perfusion pressure and regional vascular resistance and the status of blood pressure autoregulation. Evidence from RCTs does not support the notion that a higher arterial blood pressure target always leads to improved outcomes. Management of blood pressure is not about maintaining a prespecified value, but rather involves ensuring organ perfusion without undue stress on the cardiovascular system.

Renal tissue desaturation and acute kidney injury in infant cardiac surgery: a prospective propensity score-matched cohort study.

BACKGROUND: Previous studies on the association between renal tissue desaturation and acute kidney injury (AKI) in infant cardiac surgery are limited by small sample sizes and inconsistent results. This prospective study aimed to determine the association between renal desaturation and AKI in infants undergoing surgical repair of an isolated ventricular septal defect (VSD). METHODS: Infants undergoing VSD repair involving cardiopulmonary bypass participated in this prospective cohort study. The exposure of interest was renal tissue desaturation, defined as at least 20% decrease in saturation from baseline for at least 60 consecutive seconds. Intraoperative care was not guided by renal oxygenation, as the anaesthesiologists were blinded to the monitor. The outcome was AKI arising within postoperative Days 1-3. The primary analysis was based on propensity score-matched infants with and without intraoperative renal desaturation. RESULTS: Intraoperative renal desaturation was detected in 38 of 242 infants using near-infrared spectroscopy. This group of infants was matched with 114 infants without intraoperative renal saturation after propensity score matching. Acute kidney injury occurred in 47% (18/38) and 27% (31/114) of infants with or without renal desaturation, respectively. Infants with renal desaturation had higher odds of developing AKI than infants without renal desaturation based on conditional logistic regression (odds ratio 2.79; 95% confidence interval: 1.21-6.44; P=0.016). The cumulative time of renal desaturation correlated moderately with the ratio of postoperative peak creatinine to preoperative baseline creatinine (r=0.51; P<0.001). CONCLUSIONS: Intraoperative renal desaturation is associated with increased odds of developing AKI after surgical repair of an isolated VSD involving cardiopulmonary bypass in infants. CLINICAL TRIAL REGISTRATION: NCT03941015.

Association Between Cerebral Desaturation and Postoperative Delirium in Thoracotomy With One-Lung Ventilation: A Prospective Cohort Study.

BACKGROUND: The association between cerebral desaturation and postoperative delirium in thoracotomy with one-lung ventilation (OLV) has not been specifically studied. METHODS: A prospective observational study performed in thoracic surgical patients. Cerebral tissue oxygen saturation (Scto2) was monitored on the left and right foreheads using a near-infrared spectroscopy oximeter. Baseline Scto2 was measured with patients awake and breathing room air. The minimum Scto2 was the lowest measurement at any time during surgery. Cerebral desaturation and hypersaturation were an episode of Scto2 below and above a given threshold for ≥15 seconds during surgery, respectively. The thresholds based on relative changes by referring to the baseline measurement were <80%, <85%, <90%, <95%, and <100% baseline for desaturation and >105%, >110%, >115%, and >120% baseline for hypersaturation. The thresholds based on absolute values were <50%, <55%, <60%, <65%, and <70% for desaturation and >75%, >80%, >85%, and >90% for hypersaturation. The given area under the threshold (AUT)/area above the threshold (AAT) was analyzed. Delirium was assessed until postoperative day 5. The primary analysis was the association between the minimum Scto2 and delirium using multivariable logistic regression controlled for confounders (age, OLV time, use of midazolam, occurrence of hypotension, and severity of pain). The secondary analysis was the association between cerebral desaturation/hypersaturation and delirium, and between the AUT/AAT and delirium using multivariable logistic regression controlled for the same confounders. Multiple testing was corrected using the Holm-Bonferroni method. We additionally monitored somatic tissue oxygen saturation on the forearm and upper thigh. RESULTS: Delirium occurred in 35 (20%) of 175 patients (65 ± 6 years old). The minimum left or right Scto2 was not associated with delirium. Cerebral desaturation defined by <90% baseline for left Scto2 (odds ratio [OR], 5.82; 95% confidence interval [CI], 2.12-19.2; corrected P =.008) and <85% baseline for right Scto2 (OR, 4.27; 95% CI, 1.77-11.0; corrected P =.01) was associated with an increased risk of delirium. Cerebral desaturation defined by other thresholds, cerebral hypersaturation, the AUT/AAT, and somatic desaturation and hypersaturation were all not associated with delirium. CONCLUSIONS: Cerebral desaturation defined by <90% baseline for left Scto2 and <85% baseline for right Scto2, but not the minimum Scto2, may be associated with an increased risk of postthoracotomy delirium. The validity of these thresholds needs to be tested by randomized controlled trials.

The effect of selective cerebral perfusion on cerebral versus somatic tissue oxygenation during aortic coarctation repair in neonates and infants.

BACKGROUND: Suboptimal tissue perfusion and oxygenation may be the root cause of certain perioperative complications in neonates and infants having complicated aortic coarctation repair. Practical, effective, and real-time monitoring of organ perfusion and/or tissue oxygenation may provide early warning of end-organ mal-perfusion. METHODS: Neonates/infants who were scheduled for aortic coarctation repair with cardiopulmonary bypass (CPB) and selective cerebral perfusion (SCP) from January 2015 to February 2017 in Children's Hospital of Nanjing Medical University participated in this prospective observational study. Cerebral and somatic tissue oxygen saturation (SctO2 and SstO2) were monitored on the forehead and at the thoracolumbar paraspinal region, respectively. SctO2 and SstO2 were recorded at different time points (baseline, skin incision, CPB start, SCP start, SCP end, aortic opening, CPB end, and surgery end). SctO2 and SstO2 were correlated with mean arterial pressure (MAP) and partial pressure of arterial blood carbon dioxide (PaCO2). RESULTS: Data of 21 patients were analyzed (age=75±67 days, body weight=4.4±1.0 kg). SstO2 was significantly lower than SctO2 before aortic opening and significantly higher than SctO2 after aortic opening. SstO2 correlated with leg MAP when the measurements during SCP were (r=0.67, p<0.0001) and were not included (r=0.46, p<0.0001); in contrast, SctO2 correlated with arm MAP only when the measurements during SCP were excluded (r=0.14, p=0.08 vs. r=0.66, p<0.0001). SCP also confounded SctO2/SstO2's correlation with PaCO2; when the measurements during SCP were excluded, SctO2 positively correlated with PaCO2 (r=0.65, p<0.0001), while SstO2 negatively correlated with PaCO2 (r=-0.53, p<0.0001). CONCLUSIONS: SctO2 and SstO2 have distinct patterns of changes before and after aortic opening during neonate/infant aortic coarctation repair. SctO2/SstO2's correlations with MAP and PaCO2 are confounded by SCP. The outcome impact of combined SctO2/SstO2 monitoring remains to be studied.

Response of Chinese Anesthesiologists to the COVID-19 Outbreak.

The coronavirus disease 2019, named COVID-19 officially by the World Health Organization (Geneva, Switzerland) on February 12, 2020, has spread at unprecedented speed. After the first outbreak in Wuhan, China, Chinese anesthesiologists encountered increasing numbers of infected patients since December 2019. Because the main route of transmission is via respiratory droplets and close contact, anesthesia providers are at a high risk when responding to the devastating mass emergency. So far, actions have been taken including but not limited to nationwide actions and online education regarding special procedures of airway management, oxygen therapy, ventilation support, hemodynamic management, sedation, and analgesia. As the epidemic situation has lasted for months (thus far), special platforms have also been set up to provide free mental health care to all anesthesia providers participating in acute and critical caring for COVID-19 patients. The current article documents the actions taken, lesson learned, and future work needed.

Intubation and Ventilation amid the COVID-19 Outbreak: Wuhan's Experience.

The COVID-19 outbreak has led to 80,409 diagnosed cases and 3,012 deaths in mainland China based on the data released on March 4, 2020. Approximately 3.2% of patients with COVID-19 required intubation and invasive ventilation at some point in the disease course. Providing best practices regarding intubation and ventilation for an overwhelming number of patients with COVID-19 amid an enhanced risk of cross-infection is a daunting undertaking. The authors presented the experience of caring for the critically ill patients with COVID-19 in Wuhan. It is extremely important to follow strict self-protection precautions. Timely, but not premature, intubation is crucial to counter a progressively enlarging oxygen debt despite high-flow oxygen therapy and bilevel positive airway pressure ventilation. Thorough preparation, satisfactory preoxygenation, modified rapid sequence induction, and rapid intubation using a video laryngoscope are widely used intubation strategies in Wuhan. Lung-protective ventilation, prone position ventilation, and adequate sedation and analgesia are essential components of ventilation management.

Muscular Tissue Oxygen Saturation and Posthysterectomy Nausea and Vomiting: The iMODIPONV Randomized Controlled Trial.

BACKGROUND: Suboptimal tissue perfusion and oxygenation during surgery may be responsible for postoperative nausea and vomiting in some patients. This trial tested the hypothesis that muscular tissue oxygen saturation-guided intraoperative care reduces postoperative nausea and vomiting. METHODS: This multicenter, pragmatic, patient- and assessor-blinded randomized controlled (1:1 ratio) trial was conducted from September 2018 to June 2019 at six teaching hospitals in four different cities in China. Nonsmoking women, 18 to 65 yr old, and having elective laparoscopic surgery involving hysterectomy (n = 800) were randomly assigned to receive either intraoperative muscular tissue oxygen saturation-guided care or usual care. The goal was to maintain muscular tissue oxygen saturation, measured at flank and on forearm, greater than baseline or 70%, whichever was higher. The primary outcome was 24-h postoperative nausea and vomiting. Secondary outcomes included nausea severity, quality of recovery, and 30-day morbidity and mortality. RESULTS: Of the 800 randomized patients (median age, 50 yr [range, 27 to 65]), 799 were assessed for the primary outcome. The below-goal muscular tissue oxygen saturation area under the curve was significantly smaller in patients receiving muscular tissue oxygen saturation-guided care (n = 400) than in those receiving usual care (n = 399; flank, 50 vs. 140% · min, P < 0.001; forearm, 53 vs. 245% · min, P < 0.001). The incidences of 24-h postoperative nausea and vomiting were 32% (127 of 400) in the muscular tissue oxygen saturation-guided care group and 36% (142 of 399) in the usual care group, which were not significantly different (risk ratio, 0.89; 95% CI, 0.73 to 1.08; P = 0.251). There were no significant between-group differences for secondary outcomes. No harm was observed throughout the study. CONCLUSIONS: In a relatively young and healthy female patient population, personalized, goal-directed, muscular tissue oxygen saturation-guided intraoperative care is effective in treating decreased muscular tissue oxygen saturation but does not reduce the incidence of 24-h posthysterectomy nausea and vomiting.

Knowledge and perceptions about perioperative stroke: a cross-sectional survey of patients scheduled for non-neurologic and non-cardiac surgery.

PURPOSE: Perioperative stroke is associated with significant morbidity and mortality yet patients may not be aware of their risk or receive appropriate counselling. Our objectives were to 1) compare patient's perceived vs calculated risk of stroke; 2) determine level of worry; and 3) assess prior discussion about perioperative stroke risk amongst elective patients undergoing non-cardiac, non-neurologic surgery. METHODS: Over a consecutive four-week period, surveys were distributed at two pre-anesthetic clinics to adult patients scheduled for non-cardiac, non-neurologic surgery. The survey included questions about demographics, perioperative stroke risk factors, patient perception of their quantitative and qualitative stroke risk, level of worry about stroke, and risk discussions. We identified independent predictors of risk underestimation amongst medium- and high-risk patients. RESULTS: Six hundred patients completed the survey (response rate 78%). Of these, 479, 104, and 15 patients were classified as low-, medium-, and high-risk, respectively (with two patients missing this data point). Most medium- (86%) and high-risk (80%) patients did not identify their elevated risk. Amongst medium- and high-risk patients, independent predictors of risk underestimation were lower education and absence of kidney disease. Medium- and high-risk patients were more worried than low-risk patients about perioperative stroke (median [interquartile range] visual analogue scale score 2 [0.5-4] vs 1 [0-2], P = 0.001). Fewer than half of patients had discussed perioperative stroke previously (40%, 23%, and 12% of high-, medium-, and low-risk patients, respectively). CONCLUSIONS: Patients at higher risk of stroke frequently underestimate their risk of perioperative stroke. The majority of patients had not discussed perioperative stroke prior to anesthetic consultation.

Do cerebral and somatic tissue oxygen saturation measurements correlate with each other during surgery?

Intraoperative maintenance of optimal tissue oxygenation is critical; however, it is uncertain whether measurements of different tissue beds correlate with each other. Cerebral tissue oxygen saturation (SctO2) measured on the forehead and somatic tissue oxygen saturation (SstO2) measured on limbs, using a tissue near-infrared spectroscopy, were simultaneously recorded every 2 s in patients having spine surgery or robotic hysterectomy. Simple linear regression was used to determine the static correlation between SctO2 and SstO2 using the median values of each min for each patient. The dynamic correlation between SctO2 and SstO2 was assessed by Pearson's correlation coefficient (CC) for each non-overlapping 2-min epoch. In patients having spine surgery (n = 99), SctO2 and SstO2 (mean ± SD) were 69.8 ± 4.9% and 75.5 ± 8.7%, whereas in patients having robotic hysterectomy (n = 106), the corresponding values were 74.9 ± 6.8% and 83.7 ± 6.2%. The static correlation between SctO2 and SstO2 was inconsistent (r ranging from - 0.86 to 0.93 in spine surgery and from - 0.74 to 0.85 in robotic hysterectomy). The proportional durations with CC ≤ - 0.3 (negative correlation), - 0.3 < CC < 0.3 (poor correlation) and CC ≥ 0.3 (positive correlation) were 18.3 ± 9.6%, 52.6 ± 12.1% and 29.0 ± 9.6%, respectively, in patients having spine surgery and 19.6 ± 9.0%, 58.6 ± 13.1% and 21.8 ± 8.0%, respectively, in patients having robotic hysterectomy. There are a large discrepancy and inconsistent correlation between intraoperative SctO2 and SstO2 measurements, suggesting their non-interchangeability.

Double standards: why is pulse oximetry standard care, whereas tissue oximetry is not?

PURPOSE OF REVIEW: Why is pulse oximetry a standard monitor, whereas tissue oximeter is not? Is this a double-standard treatment? RECENT FINDINGS: There appears to be a lack of enthusiasm for a continual investigation into whether the use of pulse oximetry leads to reduced morbidity and mortality in acute care although there is no robust evidence attesting to its outcome benefits. In contrast, research investigating the outcome effectiveness of tissue oximetry-guided care is consistently ongoing. A recent randomized controlled trial involving 800 patients who underwent laparoscopic hysterectomy found that, although muscular tissue oxygen saturation-guided care did not reduce the overall occurrence of postoperative nausea and vomiting for all patients, it did reduce the occurrence of these symptoms in patients who had a body mass index ≥25. It was also observed that muscular tissue oxygen saturation increases when blood pressure falls following the administration of nicardipine. These studies highlight the persistence of interest in understanding the value of tissue oximetry in patient care. SUMMARY: Pulse oximetry and tissue oximetry are treated differently although neither monitor has robust evidence attesting to its outcome benefits. This difference may root in the difference in the physiology they monitor, the cost, the ease of use/interpretation/intervention and the relevance to patient safety and care quality. Pulse oxygen saturation represents a vital sign, whereas tissue oxygen saturation is likely a quality sign; however, further research endeavors are required to fully understand how to best use tissue oximetry.

Heterogeneity and Variability in Pressure Autoregulation of Organ Blood Flow: Lessons Learned Over 100+ Years.

OBJECTIVES: Pressure autoregulation is an organ's intrinsic ability to maintain blood flow despite changes in perfusion pressure. The purpose of this review is to discuss autoregulation's heterogeneity among different organs and variability under different conditions, a very clinically relevant topic. DATA SOURCES: Systematic search of Ovid MEDLINE; nonsystematic search of PubMed, Google Scholar, and reference lists. STUDY SELECTION: Animal or human studies investigating the potency or variation of pressure autoregulation of any organs or the association between autoregulation and outcomes. DATA EXTRACTION: Two authors screened the identified studies independently then collectively agreed upon articles to be used as the basis for this review. DATA SYNTHESIS: Study details, including subjects, organ investigated, methods of blood pressure intervention and blood flow measurement, and values of the lower limit, upper limit, and plateau were examined. Comparative canine studies were used to demonstrate the heterogeneity of pressure autoregulation among different organs and validate the proposed scale for organ categorization by autoregulatory capacity. Autoregulatory variability is discussed per organ. The association between cerebral autoregulation and outcome is summarized. CONCLUSIONS: The organs with robust autoregulation are the brain, spinal cord, heart, and kidney. Skeletal muscle has moderate autoregulation. Nearly all splanchnic organs including the stomach, small intestine, colon, liver, and pancreas possess weak autoregulation. Autoregulation can be readily affected by a variety of clinically relevant factors. Organs with weak or weakened autoregulation are at a greater risk of suboptimal perfusion when blood pressure fluctuates. Cerebral autoregulation and outcomes are closely related. These lessons learned over 100+ years are instructive in clinical care.

Tourniquet-induced tissue hypoxia characterized by near-infrared spectroscopy during ankle surgery: an observational study.

BACKGROUND: Pneumatic tourniquet inflation during extremity surgery leads to profound and prolonged tissue ischemia. Its effect on tissue oxygenation is inadequately studied. METHODS: Patients undergoing elective ankle surgery with tourniquet application participated in this observational cohort study. Somatic and cerebral tissue oxygen saturation (SstO2 and SctO2) were monitored using tissue near-infrared spectroscopy. Oxygenation was monitored distally (SstO2-distal) and proximally to the tourniquet, on the contralateral leg, and the forehead (a total of 4 tissue beds). Tissue oxygenation at different time points was compared. The magnitude, duration, and load (product of magnitude and duration) of tissue desaturation during tourniquet inflation were correlated with tissue resaturation and hypersaturation after tourniquet deflation. RESULTS: Data of 26 patients were analyzed. The tourniquet inflation time was 120 ± 31 mins. Following a rapid desaturation from 77 ± 8% pre-inflation to 38 ± 20% 10 mins post-inflation, SstO2-distal slowly and continuously desaturated and reach the nadir (16 ± 11%) toward the end of inflation. After deflation, SstO2-distal rapidly resaturated from 16 ± 11% to 91 ± 5% (i.e., hypersaturation); SstO2 monitored proximally to the tourniquet and on contralateral leg had significant but small desaturation (~ 2-3%, p <  0.001); in contrast, SctO2 remained stable. The desaturation load had a significant correlation with resaturation magnitude (p <  0.001); while the desaturation duration had a significant correlation with hypersaturation magnitude (p = 0.04). CONCLUSIONS: Tissue dys-oxygenation following tourniquet application can be reliably monitored using tissue oximetry. Its outcome significance remains to be determined.