Perioperative ketamine for postoperative pain management in patients with preoperative opioid intake: A systematic review and meta-analysis.

STUDY OBJECTIVE: Postoperative pain management in opioid users remains challenging. The perioperative administration of ketamine might lead to favourable pain outcomes in these patients. STUDY DESIGN: A systematic review of randomised controlled trials (RCT) with meta-analysis and assessment of the quality of evidence by GRADE was performed. SETTING: Perioperative pain treatment. PATIENTS: Adult opioid users undergoing surgery. INTERVENTIONS: Perioperative administration of ketamine. MEASUREMENTS: Primary outcomes were postoperative acute pain at rest/during movement after 24 h and number of patients with ketamine-related adverse events. MAIN RESULTS: Nine RCTs (802 patients with at least two weeks opioid-intake) were included. There is low-quality evidence that ketamine may slightly reduce postoperative pain during movement after 24 h (mean difference: -0.79; 95% confidence interval (CI): -1.22 to -0.36). Based on a very low-quality of evidence, we are uncertain on any effect of ketamine on pain at rest after 24 h and incidences of adverse events like hallucinations and confusion within 48 h. However, perioperative ketamine reduced cumulative mean opioid consumption by 97.3 mg (95%CI: -164.8 to -29.7) after 24 h and 186.4 mg (95%CI: -347.6 to -25.2) after 48 h. The relative risks (RR) for opioid-related adverse events were significantly different for sedation within 24 h (RR: 0.54; 95%CI 0.37 to 0.78). CONCLUSIONS: There is currently limited evidence for a reduced postoperative pain intensity using perioperative ketamine in preoperative opioid-consuming patients. However, a clinically relevant opioid-sparing effect was evident associated with a reduced risk for postoperative sedation and without increased harm. Therefore, ketamine might be a useful anti-hyperalgesic adjuvant in these patients. Nevertheless, with clinical heterogeneity being considerable, it's too premature to suggest any specific ketamine protocol. Furthermore, many questions (like ideal dosing, treatment duration and more favourable patient-related outcome measures including long-term effects) remain open and need to be addressed in future studies. PROTOCOL REGISTRATION: Prospero CRD42020185497.

Role of selective V2-receptor-antagonism in septic shock: a randomized, controlled, experimental study.

INTRODUCTION: V(2)-receptor (V(2)R) stimulation potentially aggravates sepsis-induced vasodilation, fluid accumulation and microvascular thrombosis. Therefore, the present study was performed to determine the effects of a first-line therapy with the selective V(2)R-antagonist (Propionyl(1)-D-Tyr(Et)(2)-Val(4)-Abu(6)-Arg(8,9))-Vasopressin on cardiopulmonary hemodynamics and organ function vs. the mixed V(1a)R/V(2)R-agonist arginine vasopressin (AVP) or placebo in an established ovine model of septic shock. METHODS: After the onset of septic shock, chronically instrumented sheep were randomly assigned to receive first-line treatment with the selective V(2)R-antagonist (1 µg/kg per hour), AVP (0.05 µg/kg per hour), or normal saline (placebo, each n = 7). In all groups, open-label norepinephrine was additionally titrated up to 1 µg/kg per minute to maintain mean arterial pressure at 70 ± 5 mmHg, if necessary. RESULTS: Compared to AVP- and placebo-treated animals, the selective V(2)R-antagonist stabilized cardiopulmonary hemodynamics (mean arterial and pulmonary artery pressure, cardiac index) as effectively and increased intravascular volume as suggested by higher cardiac filling pressures. Furthermore, left ventricular stroke work index was higher in the V(2)R-antagonist group than in the AVP group. Notably, metabolic (pH, base excess, lactate concentrations), liver (transaminases, bilirubin) and renal (creatinine and blood urea nitrogen plasma levels, urinary output, creatinine clearance) dysfunctions were attenuated by the V(2)R-antagonist when compared with AVP and placebo. The onset of septic shock was associated with an increase in AVP plasma levels as compared to baseline in all groups. Whereas AVP plasma levels remained constant in the placebo group, infusion of AVP increased AVP plasma levels up to 149 ± 21 pg/mL. Notably, treatment with the selective V(2)R-antagonist led to a significant decrease of AVP plasma levels as compared to shock time (P < 0.001) and to both other groups (P < 0.05 vs. placebo; P < 0.001 vs. AVP). Immunohistochemical analyses of lung tissue revealed higher hemeoxygenase-1 (vs. placebo) and lower 3-nitrotyrosine concentrations (vs. AVP) in the V(2)R-antagonist group. In addition, the selective V(2)R-antagonist slightly prolonged survival (14 ± 1 hour) when compared to AVP (11 ± 1 hour, P = 0.007) and placebo (11 ± 1 hour, P = 0.025). CONCLUSIONS: Selective V(2)R-antagonism may represent an innovative therapeutic approach to attenuate multiple organ dysfunction in early septic shock.