Renin Levels and Angiotensin II Responsiveness in Vasopressor-Dependent Hypotension.

OBJECTIVES: The relationship between renin levels, exposure to renin-angiotensin system (RAS) inhibitors, angiotensin II (ANGII) responsiveness, and outcome in patients with vasopressor-dependent vasodilatory hypotension is unknown. DESIGN: We conducted a single-center prospective observational study to explore whether recent RAS inhibitor exposure affected baseline renin levels, whether baseline renin levels predicted ANGII responsiveness, and whether renin levels at 24 hours were associated with clinical outcomes. SETTING: An academic ICU in Melbourne, VIC, Australia. PATIENTS: Forty critically ill adults who received ANGII as the primary agent for vasopressor-dependent vasodilatory hypotension who were included in the Acute Renal effects of Angiotensin II Management in Shock study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: After multivariable adjustment, recent exposure to a RAS inhibitor was independently associated with a relative increase in baseline renin levels by 198% (95% CI, 36-552%). The peak amount of ANGII required to achieve target mean arterial pressure was independently associated with baseline renin level (increase by 46% per ten-fold increase; 95% CI, 8-98%). Higher renin levels at 24 hours after ANGII initiation were independently associated with fewer days alive and free of continuous renal replacement therapy (CRRT) (-7 d per ten-fold increase; 95% CI, -12 to -1). CONCLUSIONS: In patients with vasopressor-dependent vasodilatory hypotension, recent RAS inhibitor exposure was associated with higher baseline renin levels. Such higher renin levels were then associated with decreased ANGII responsiveness. Higher renin levels at 24 hours despite ANGII infusion were associated with fewer days alive and CRRT-free. These preliminary findings emphasize the importance of the RAS and the role of renin as a biomarker in patients with vasopressor-dependent vasodilatory hypotension.

Postoperative Pulmonary Complications in the ENIGMA II Trial: A Post Hoc Analysis.

BACKGROUND: Nitrous oxide promotes absorption atelectasis in poorly ventilated lung segments at high inspired concentrations. The Evaluation of Nitrous oxide In the Gas Mixture for Anesthesia (ENIGMA) trial found a higher incidence of postoperative pulmonary complications and wound sepsis with nitrous oxide anesthesia in major surgery compared to a fraction of inspired oxygen of 0.8 without nitrous oxide. The larger ENIGMA II trial randomized patients to nitrous oxide or air at a fraction of inspired oxygen of 0.3 but found no effect on wound infection or sepsis. However, postoperative pulmonary complications were not measured. In the current study, post hoc data were collected to determine whether atelectasis and pneumonia incidences were higher with nitrous oxide in patients who were recruited to the Australian cohort of ENIGMA II. METHODS: Digital health records of patients who participated in the trial at 10 Australian hospitals were examined blinded to trial treatment allocation. The primary endpoint was the incidence of atelectasis, defined as lung atelectasis or collapse reported on chest radiology. Pneumonia, as a secondary endpoint, required a diagnostic chest radiology report with fever, leukocytosis, or positive sputum culture. Comparison of the nitrous oxide and nitrous oxide-free groups was done according to intention to treat using chi-square tests. RESULTS: Data from 2,328 randomized patients were included in the final data set. The two treatment groups were similar in surgical type and duration, risk factors, and perioperative management recorded for ENIGMA II. There was a 19.3% lower incidence of atelectasis with nitrous oxide (171 of 1,169 [14.6%] vs. 210 of 1,159 [18.1%]; odds ratio, 0.77; 95% CI, 0.62 to 0.97; P = 0.023). There was no difference in pneumonia incidence (60 of 1,169 [5.1%] vs. 52 of 1159 [4.5%]; odds ratio, 1.15; 95% CI, 0.77 to 1.72; P = 0.467) or combined pulmonary complications (odds ratio, 0.84; 95% CI, 0.69 to 1.03; P = 0.093). CONCLUSIONS: In contrast to the earlier ENIGMA trial, nitrous oxide anesthesia in the ENIGMA II trial was associated with a lower incidence of lung atelectasis, but not pneumonia, after major surgery.

Low tidal volume ventilation for patients undergoing laparoscopic surgery: a secondary analysis of a randomised clinical trial.

BACKGROUND: We recently reported the results for a large randomized controlled trial of low tidal volume ventilation (LTVV) versus conventional tidal volume (CTVV) during major surgery when positive end expiratory pressure (PEEP) was equal between groups. We found no difference in postoperative pulmonary complications (PPCs) in patients who received LTVV. However, in the subgroup of patients undergoing laparoscopic surgery, LTVV was associated with a numerically lower rate of PPCs after surgery. We aimed to further assess the relationship between LTVV versus CTVV during laparoscopic surgery. METHODS: We conducted a post-hoc analysis of this pre-specified subgroup. All patients received volume-controlled ventilation with an applied PEEP of 5 cmH2O and either LTVV (6 mL/kg predicted body weight [PBW]) or CTVV (10 mL/kg PBW). The primary outcome was the incidence of a composite of PPCs within seven days. RESULTS: Three hundred twenty-eight patients (27.2%) underwent laparoscopic surgeries, with 158 (48.2%) randomised to LTVV. Fifty two of 157 patients (33.1%) assigned to LTVV and 72 of 169 (42.6%) assigned to conventional tidal volume developed PPCs within 7 days (unadjusted absolute difference, - 9.48 [95% CI, - 19.86 to 1.05]; p = 0.076). After adjusting for pre-specified confounders, the LTVV group had a lower incidence of the primary outcome than patients receiving CTVV (adjusted absolute difference, - 10.36 [95% CI, - 20.52 to - 0.20]; p = 0.046). CONCLUSION: In this post-hoc analysis of a large, randomised trial of LTVV we found that during laparoscopic surgeries, LTVV was associated with a significantly reduced PPCs compared to CTVV when PEEP was applied equally between both groups. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry no: 12614000790640.

The relationship between study findings and publication outcome in anesthesia research: a retrospective observational study examining publication bias.

PURPOSE: Many areas of medicine have shown bias towards the publication of studies with positive results. To estimate publication bias in the anesthesia literature, we reviewed all abstracts presented at the American Society of Anesthesiologists (ASA) annual meetings over a four-year period and compared study results (positive vs negative) with publication outcomes. METHODS: This review included all abstracts from the 2001-2004 ASA annual meetings performed as randomized-controlled trials in humans. We scored their outcome results as positive or negative and assessed abstract quality using a 13-point scoring system. We then performed a systematic literature search to identify any subsequent publication of the studies and calculated the relative risk (RR) for journal publication by comparing positive vs negative studies. RESULTS: Of 5,918 abstracts reviewed, 1,052 met inclusion criteria, and 564 (53.6%) of the abstracts proceeded to publication. The RR for abstracts with positive results proceeding to journal publication was 1.42 (95% confidence interval, 1.22 to 1.66; P < 0.001). This result did not change significantly after adjusting for study size and abstract quality score during logistic regression modelling. There was no significant difference in the abstract quality score between positive vs negative studies or between abstracts proceeding vs not proceeding to publication. CONCLUSIONS: Approximately half of the ASA annual meeting abstracts proceed to publication. After adjustment for study quality and size, abstracts with positive results were more likely to proceed to journal publication than those with negative results, suggesting publication bias in the anesthesia literature.

Dose equivalence for metaraminol and noradrenaline - A retrospective analysis.

BACKGROUND: Noradrenaline and metaraminol are commonly used vasopressors in critically ill patients. However, little is known of their dose equivalence. METHODS: We conducted a single centre retrospective cohort study of all ICU patients who transitioned from metaraminol to noradrenaline infusions between August 26, 2016 and December 31, 2020. Patients receiving additional vasoactive drug infusion were excluded. Dose equivalence was calculated based on the last hour metaraminol dose (in µg/min) and the first hour noradrenaline dose (in µg/min) with the closest matched mean arterial pressure (MAP). Sensitivity analyses were performed on patients with acute kidney injury (AKI), sepsis and mechanical ventilation. RESULTS: We studied 195 patients. The median conversion ratio of metaraminol to noradrenaline was 12.5:1 (IQR 7.5-20.0) for the overall cohort. However, the coefficient of variation was 77% and standard deviation was 11.8. Conversion ratios were unaffected by sepsis or mechanical ventilation but increased (14:1) with AKI. One in five patients had a MAP decrease of >10 mmHg during the transition period from metaraminol to noradrenaline. Post-transition noradrenaline dose (p < 0.001) and AKI (p = 0.045) were independently associated with metaraminol dose. The proportion of variation in noradrenaline dose predicted from metaraminol dose was low (R2 = 0.545). CONCLUSIONS: The median dose equivalence for metaraminol and noradrenaline in this study was 12.5:1. However, there was significant variance in dose equivalence, only half the proportion of variation in noradrenaline infusion dose was predicted by metaraminol dose, and conversion-associated hypotension was common.

Exploring the norepinephrine to angiotensin II conversion ratio in patients with vasodilatory hypotension: A post-hoc analysis of the ARAMIS trial.

PURPOSE: Angiotensin II is approved for catecholamine-refractory vasodilatory shock but the conversion dose ratio from norepinephrine to angiotensin II remains unclear. METHODS: We conducted a post-hoc analysis of the Acute Renal effects of Angiotensin II Management in Shock (ARAMIS) trial involving patients with vasodilatory hypotension. We determined the norepinephrine equivalent dose immediately prior to angiotensin II initiation and calculated the conversion dose ratio between norepinephrine and angiotensin II. We performed subgroup analyses based on recent exposure to angiotensin receptor blockers (ARBs) and renin levels at baseline. RESULTS: In 37 patients, the median conversion dose ratio between norepinephrine equivalent and angiotensin II was to 10:1 for norepinephrine bitartrate (5:1 for norepinephrine base). The conversion ratio was not affected by the baseline renin, with a median ratio of 10 (7-21) in the high renin group versus 12 (5-22) in the low renin group. Finally, exposure to ARBs prior admission appeared to diminish the conversion ratio with a median ratio of 7 (4-13) in ARB patients vs. 12 (7-22) in non-ARB patients. CONCLUSIONS: The norepinephrine to angiotensin II conversion dose ratio is 10:1 in a vasodilatory hypotension population. These findings can guide clinicians and researchers in the use, dosing, and study of angiotensin II in critical care.

A PILOT STUDY OF ANGIOTENSIN II AS PRIMARY VASOPRESSOR IN CRITICALLY ILL ADULTS WITH VASODILATORY HYPOTENSION: THE ARAMIS STUDY.

ABSTRACT: Objective: The aim of the study is to evaluate the efficacy and safety of using angiotensin II (Ang2) as primary vasopressor for vasodilatory hypotension. Methods: This was a prospective observational study of critically ill adults admitted to an academic intensive care unit (ICU) with vasodilatory hypotension. We treated 40 patients with Ang2 as primary vasopressor and compared them with 80 matched controls who received conventional vasopressors (norepinephrine, vasopressin, metaraminol, epinephrine, or combinations). Results : Mean age was 63 years and median Acute Physiology and Chronic Health Evaluation III score was 65. Ang2 patients had lower ICU mortality (10% vs 26%, P = 0.04); however, their 28- and 90-day mortality was not significantly different (18% vs 29%, P = 0.18; 22% vs 30%, P = 0.39). Peak serum creatinine levels were similar (128 vs 126 µmol/L, P = 0.81), as was the incidence and stage of acute kidney injury (70% vs 74%, P = 0.66), requirement for continuous renal replacement therapy (14% vs 13%, P = 0.84), and risk of major adverse kidney events at 7 days (20% vs 29%, P = 0.30). However, Ang2 patients with prior exposure to renin angiotensin aldosterone system inhibitors had a lower peak serum creatinine ( P = 0.03 for interaction) than conventional vasopressors patients, and serum troponin elevations were less common with Ang2 (8% vs 22%, P = 0.04). The incidence of thromboembolic complications was similar. Conclusions: Primary Ang2 administration in vasodilatory hypotension did not seem harmful compared with conventional vasopressors. Although Ang2 did not decrease peak serum creatinine levels or major adverse kidney events, its effects on intensive care unit survival, serum troponin, and renal function in patients on renin angiotensin aldosterone system inhibitors warrant further exploration in randomized trials (ACTRN12621000281897).

The relationship between study findings and publication outcome in anesthesia research following implementation of mandatory trial registration: A systematic review of publication bias.

Previously, we reviewed 1052 randomized-controlled trial abstracts presented at the American Society of Anesthesiologists annual meetings from 2001-2004. We found significant positive publication bias in the period examined, with the odds ratio for abstracts with positive results proceeding to journal publication over those with null results being 2.01 [95% confidence interval: 1.52, 2.66; P < 0.001]. Mandatory trial registration was introduced in 2005 as a required standard for publication. We sought to examine whether mandatory trial registration has decreased publication bias in the anesthesia and perioperative medicine literature. We reviewed all abstracts from the 2010-2016 American Society of Anesthesiologists meetings that reported on randomized-controlled trials in humans. We scored the result of each abstract as positive or null according to a priori definitions. We systematically searched for any subsequent publication of the studies and calculated the odds ratio for journal publication, comparing positive vs null studies. We compared the odds ratio from the 2010-2016 abstracts (post-mandatory trial registration) with the odds ratio from the 2001-2004 abstracts (pre-mandatory trial registration) as a ratio of odds ratios. We defined a 33% decrease in the odds ratio as significant, corresponding to a new odds ratio of 1.33. We reviewed 9789 abstracts; 1049 met inclusion criteria as randomized-controlled trials, with 542 (51.7%) of the abstracts going on to publication. The odds ratio for abstracts with positive results proceeding to journal publication was 1.28 [95% CI: 0.97, 1.67; P = 0.076]. With adjustment for sample size and abstract quality, the difference in publication rate between positive and null abstracts was statistically significant (odds ratio 1.34; 95% CI: 1.02, 1.76; P = 0.037). The ratio of odds ratios, comparing the odds ratio from the 2010-2016 abstracts (post-mandatory trial registration) to the odds ratio from the 2001-2004 abstracts (pre-mandatory trial registration), was 0.63 (95% CI: 0.43, 0.93); P = 0.021). We present the first study in the anesthesia and perioperative medicine literature that examines and compares publication bias over two discrete periods of time, prior to and after the implementation of mandatory trial registration. Our results suggest that the amount of publication bias has decreased markedly following implementation of mandatory trial registration. However, some positive publication bias in the anesthesia and perioperative medicine literature remains.

Trial registration of abstracts from the American Society of Anesthesiologists Meetings 2010-2016: A review of prospective trial registration and selective outcome reporting.

Mandatory prospective trial registration was introduced in 2005 to reduce publication bias and selective outcome reporting. In this study, we measured the proportion of prospective trial registration in randomized controlled trials in the anesthesia literature after this introduction, discrepancies between these trial protocols and subsequent publications, the association between being prospectively registered and reporting positive or negative results, and between being prospectively registered and achieving publication. We reviewed all abstracts from the American Society of Anesthesiologists annual meetings between 2010-2016 and included randomized controlled trials in humans. The abstract conclusions were scored as positive or negative according to predetermined definitions. We conducted a systematic search for trial registration and subsequent publication. Of the 9789 abstracts reviewed, 1070 abstracts were included. 222 (21%) of these abstracts had undergone prospective trial registration. 168/222 (76%) had a corresponding journal publication. 81(48%) had a major discrepancy between registration and publication. 149 (67%) of the abstracts with registration had positive outcomes compared with 616 (73%) of those without (Odds Ratio 0.77; 95% CI: 0.56 to 1.06; P = 0.105). Abstracts that had been registered were more likely to proceed to publication than those that had not (Odds Ratio 3.82; 95% CI 2.73 to 5.35; P < 0.001). The proportion of randomized controlled trials being prospectively registered in anesthesia remains low. Discrepancies between registry entries and corresponding journal publications are common. There was no association between prospective trial registration and subsequent positive outcomes. There was a strong association between prospective trial registration and the likelihood of progression to journal publication.