Stapelfeldt, Wolf H.

BACKGROUND: Postoperative hypotension (POH) is associated with major adverse events. However, little is known about the association of blood pressure thresholds and outcomes in postoperative patients without intraoperative hypotension (IOH) on the general-care ward. We evaluated the association of POH with major adverse cardiac or cerebrovascular events (MACCE) in patients without IOH. METHODS: This retrospective analysis included 67,968 noncardiac patient-procedures (2008–2017) for patients discharged to the ward with postoperative mean arterial pressure (MAP) readings, managed for ≥48 hours postsurgery, with no evidence of IOH. The primary outcome was 30-day MACCE evaluated by postoperative MAP thresholds: ≤75, ≤65, and ≤55 mm Hg (POH defined as a single measurement below threshold). Secondary outcomes included all-cause mortality (30-/90-day), 30-day acute myocardial infarction, 30-day acute ischemic stroke, 30-day readmission, 7-day acute kidney injury, and 30-day readmission. Associations between POH and adverse events were also evaluated in a cohort (#2) of 16,034 patient-procedures with IOH (intraoperative MAP ≤65 mm Hg). RESULTS: In patients without IOH, exposure to POH was not associated with MACCE at any investigated MAP threshold ( P < .016 was considered significant: ≤75 mm Hg, hazard ratio [HR] 1.18 [98.4% confidence interval {CI} 0.99-1.39], P = .023; ≤65 mm Hg, HR 1.18 [0.99–1.41], P = .028; ≤55 mm Hg, HR 1.23 [0.90–1.71], P = .121); however, associations were observed at all MAP thresholds for secondary outcomes of acute kidney injury and 30-day readmission, for 30-/90-day mortality for MAP ≤65 mm Hg, and 90-day mortality for MAP ≤55 mm Hg, compared to those without POH. No associations were detected between POH and secondary outcomes of acute ischemic stroke or acute myocardial infarction at any MAP threshold. No interaction between POH and IOH was found when we evaluated the association of POH on outcomes in the data set including all patients, regardless of IOH status ( P values for interaction terms nonsignificant). When the interaction term was utilized, the association between POH without IOH and MACCE was significant for MAP ≤75 mm Hg (HR 1.20 [1.01–1.41]) and MAP ≤65 mm Hg (HR 1.21 [1.02-1.45]), but not MAP ≤55 mm Hg. Cohort #2 (POH with IOH) showed largely similar results for MACCE: not significant for MAP ≤75 and ≤65 mm Hg, but significant for MAP ≤55 mm Hg (HR 1.53 [1.05–2.22], P = .006). CONCLUSIONS: POH in patients without IOH was not associated with MACCE at any MAP investigated. No interaction was identified between POH and IOH. Large prospective randomized trials are necessary to develop better evidence and inform clinicians the value of postoperative blood pressure management.

BACKGROUND: Intraoperative hypotension (IOH) occurs frequently during surgery and may be associated with organ ischemia; however, few multicenter studies report data regarding its associations with adverse postoperative outcomes across varying hemodynamic thresholds. Additionally, no study has evaluated the association between IOH exposure and adverse outcomes among patients by various age groups. METHODS: A multicenter retrospective cohort study was conducted between 2008 and 2017 using intraoperative blood pressure data from the US electronic health records database to examine postoperative outcomes. IOH was assessed in 368,222 noncardiac surgical procedures using 5 methods: (a) absolute maximum decrease in mean arterial pressure (MAP) during surgery, (b) time under each absolute threshold, (c) total area under each threshold, (d) time-weighted average MAP under each threshold, and (e) cumulative time under the prespecified relative MAP thresholds. MAP thresholds were defined by absolute limits (≤75, ≤65, ≤55 mm Hg) and by relative limits (20% and 40% lower than baseline). The primary outcome was major adverse cardiac or cerebrovascular events; secondary outcomes were all-cause 30- and 90-day mortality, 30-day acute myocardial injury, and 30-day acute ischemic stroke. Residual confounding was minimized by controlling for observable patient and surgical factors. In addition, we stratified patients into age subgroups (18–40, 41–50, 51–60, 61–70, 71–80, >80) to investigate how the association between hypotension and the likelihood of major adverse cardiac or cerebrovascular events and acute kidney injury differs in these age subgroups. RESULTS: IOH was common with at least 1 reading of MAP ≤75 mm Hg occurring in 39.5% (145,743) of cases; ≤65 mm Hg in 19.3% (70,938) of cases, and ≤55 mm Hg in 7.5% (27,473) of cases. IOH was significantly associated with the primary outcome for all age groups. For an absolute maximum decrease, the estimated odds of a major adverse cardiac or cerebrovascular events in the 30-day postsurgery was increased by 12% (95% confidence interval [CI], 11-14) for ≤75 mm Hg; 17.0% (95% CI, 15-19) for ≤65 mm Hg; and by 26.0% (95% CI, 22-29) for ≤55 mm Hg. CONCLUSIONS: IOH during noncardiac surgery is common and associated with increased 30-day major adverse cardiac or cerebrovascular events. This observation is magnified with increasing hypotension severity. The potentially avoidable nature of the hazard, and the extent of the exposed population, makes hypotension in the operating room a serious public health issue that should not be ignored for any age group.

The aims of these experiments were to determine in vitro whether colonic distension releases acetylcholine, vasoactive intestinal polypeptide (VIP), and substance P in the guinea pig inferior mesenteric ganglia (IMG) and whether cholinergic and peptidergic mechanosensory nerves projecting from the colon to the IMG receive cholinergic input from other enteric neurons. Colonic distension significantly increased the release of [3H]-acetylcholine, VIP-like immunoreactivity, and substance P-like immunoreactivity in the IMG. Nicotinic receptor blockade in the colon diminished the increase in [3H]acetylcholine release, abolished the increase in VIP-like immunoreactivity release during distension, but had no effect on the release of substance P-like immunoreactivity. Nicotinic receptor blockade in the colon also decreased fast mechanosensory input and significantly reduced by 54% the slow excitatory postsynaptic potential amplitude evoked by colonic distension. The data suggest that enteric cholinergic and VIP mechanosensory neurons that project from the colon to sympathetic neurons in the IMG receive peripheral cholinergic input from other enteric neurons. There was no evidence for enteric cholinergic input to the mechanosensory substance P pathway.

Background Paraplegia is a devastating complication for patients undergoing repair of thoracoabdominal aortic aneurysms. A monitor to detect spinal cord ischemia is necessary if anesthesiologists are to intervene to protect the spinal cord during aortic aneurysm clamping. Methods The medical records of 60 patients who underwent thoracoabdominal aortic aneurysm repair with regional lumbar epidural cooling with evoked potential monitoring were reviewed. The authors analyzed latency and amplitude of motor evoked potentials, somatosensory evoked potentials, and H reflexes before cooling and clamping, after cooling and before clamping, during clamping, and after release of aortic cross clamp. Results Twenty minutes after the aortic cross clamp was placed, motor evoked potentials had 88% sensitivity and 65% specificity in predicting spinal cord ischemia. The negative predictive value of motor evoked potentials at 20 min after aortic cross clamping was 96%. Conclusions Rapid loss of motor evoked potentials or H reflexes after application of the aortic cross clamp identifies a subgroup of patients who are at high risk of developing spinal cord ischemia and in whom aggressive anesthetic and surgical interventions may be justified.