Incidence, Outcomes, and Risk Factors of Intraoperative Cardiac Arrest During Orthotopic Liver Transplantation.

BACKGROUND: Intraoperative cardiac arrest (ICA) during liver transplantation (LT) is a rare surgical complication that results in devastating outcomes. Moreover, previous worldwide studies have found inconsistencies in the risk factors associated with ICA in LT. METHODS: This was a retrospective cohort study of adult patients who underwent LT between January and October 2021 at Siriraj Hospital, a tertiary care hospital. The incidence of ICA and outcomes of patients who experienced ICA were examined. Risk factors associated with ICA were investigated as a secondary objective. RESULTS: Among 342 patients, the incidence of ICA was 3.5% (95% CI 1.8%-6.1%). Of these, 33.3% died intraoperatively. Among patients with ICA, 41.7% died within 30 days, compared with only 7.6% in those without ICA (P = .002). Moreover, the in-hospital mortality rate of those with ICA was 58.3%, which was significantly higher than that of those without ICA (9.7%, P < .001). However, 41.7% of patients with ICA were discharged alive with long-term survival. Because ICA is a rare event, we found only 2 independent factors significantly associated with ICA. These factors include intraoperative temperature below 35°C, with an odds ratio (OR) of 6.07 (95% CI:1.32-27.88, P = .02) and elevated intraoperative serum potassium, with an OR of 4.57 (95% CI:2.15-9.67, P < .001). CONCLUSIONS: ICA is associated with high perioperative and in-hospital mortality. However, our findings suggest that with effective management of ICA, more than 40% of these patients could be discharged with excellent long-term outcomes. Hypothermia and hyperkalemia were independent risk factors significantly associated with ICA.

Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle?

Sympathetic vasoconstriction of muscle vascular beds is important in the regulation of systemic blood pressure. However, vasoconstriction during exercise can also compromise blood flow support of muscle metabolism. This study tested the hypothesis that local factors in exercising muscle blunt vessel responsiveness to sympathetic vasoconstriction. We performed selective infusions of three doses of tyramine into the brachial artery (n = 8) to evoke endogenous release of noradrenaline (norepinephrine) at rest and during moderate and heavy rhythmic handgrip exercise. In separate experiments, tyramine was administered during two doses of adenosine infusion (n = 7) and two doses of sodium nitroprusside (SNP) infusion (n = 8). Vasoconstrictor effectiveness across conditions was assessed as the percentage reduction in forearm vascular conductance (FVC), calculated from invasive blood pressure and non-invasive Doppler ultrasound blood flow measurements at the brachial artery. Tyramine evoked a similar dose-dependent vasoconstriction at rest in all three groups, with the highest dose resulting in a 42-46 % reduction in FVC. This vasoconstriction was blunted with increasing exercise intensity (e.g. tyramine high dose percentage reduction in FVC; rest -43.4 +/- 3.7 %, moderate exercise -27.5 +/- 2.3 %, heavy exercise -16.7 +/- 3.6 %; P < 0.05). In contrast, tyramine infusion resulted in a greater percentage reduction in FVC during both doses of adenosine vs. rest (P < 0.05). Finally, percentage change in FVC was greater during low dose SNP infusion vs. rest (P < 0.05), but not different from rest at the high dose of SNP infusion (P = 0.507). A blunted percentage reduction in FVC during endogenous noradrenaline release in exercise but not vasodilator infusion indicates that sympathetic vasoconstriction is blunted in exercising muscle. This blunting appears to be exercise intensity-dependent.