Intraoperative haemodynamic stability in patients with phaeochromocytoma--minimally invasive vs conventional open surgery

OBJECTIVE: There is conflicting evidence, whether or not minimally invasive adrenalectomy (MA) is associated with an increased perioperative cardiovascular instability in phaeochromocytomas compared to conventional open adrenalectomy (CA). DESIGN AND PATIENTS: In a retrospective analysis of 49 patients with phaeochromocytoma we compared 27 cases of MA to 22 cases of CA by assessing intraoperative haemodynamic parameters and perioperative complications. Patients undergoing MA for adrenocortical adenomas (aldosteronomas n = 15, inactive adenomas n = 13) served as controls. Additionally, we investigated the effect of phenoxybenzamine (POB) pretreatment on intraoperative cardiovascular stability in 42 patients (ranked by maximum daily POB-dose) by comparing the highest (n = 10) with the lowest (n = 10) POB dose quartile (0.32 +/- 0.2 and 2.17 +/- 0.6 mg/kg/day, P < 0.001). RESULTS: In phaeochromocytomas we found no significant difference in intraoperative haemodynamic parameters or complications when comparing MA with CA. In comparison to adrenocortical adenomas, MA in phaeochromocytomas was associated with a significantly higher maximum systolic BP (188 +/- 29 vs 154 +/- 22 mmHg, P < 0.001), more frequent hypertensive episodes (1[0-4]vs 0[0-1], P < 0.001), more episodes of systolic BP > 200 mmHg (0[0-4]vs 0[0-1], P = 0.03) and a higher demand for intraoperative fluids (3194 ml vs 1750 ml, P < 0.001). Most haemodynamic parameters did not differ significantly between high-dose POB pretreatment and low-dose POB pretreatment, but high-dose POB pretreatment was associated with a significantly higher intraoperative heart rate (120 +/- 19.5 vs 94 +/- 15.2 min(-1), P < 0.01). CONCLUSION: There is no significant difference in haemodynamic stability between MA and CA in phaeochromocytomas, but it is significantly inferior when compared to MA for cortical adenomas. We could not detect a beneficial effect of high-dose compared to low-dose POB pretreatment on intraoperative cardiovascular stability.     

Cardiac alternans do not rely on diastolic sarcoplasmic reticulum calcium content fluctuations

Cardiac alternans are thought to be a precursor to life-threatening arrhythmias. Previous studies suggested that alterations in sarcoplasmic reticulum (SR) Ca2+ content are either causative or not associated with myocyte Ca2+ alternans. However, those studies used indirect measures of SR Ca2+. Here we used direct continuous measurement of intra-SR free [Ca2+] ([Ca2+]SR) (using Fluo5N) during frequency-dependent Ca2+ alternans in rabbit ventricular myocytes. We tested the hypothesis that alternating [Ca2+]SR is required for Ca2+ alternans. Amplitudes of [Ca2+]SR depletions alternated in phase with cytosolic Ca2+ transients and contractions. Some cells showed clear alternation in diastolic [Ca2+]SR during alternans, with higher [Ca2+]SR before the larger SR Ca2+ releases. However, the extent of SR Ca2+ release during the small beats was smaller than expected for the modest decrease in [Ca2+]SR. In other cells, clear Ca2+ alternans was observed without alternations in diastolic [Ca2+]SR. Additionally, alternating cells were observed, in which diastolic [Ca2+]SR fluctuations occurred interspersed by depletions in which the amplitude was unrelated to the preceding diastolic [Ca2+]SR. In all forms of alternans, the SR Ca2+ release rate was higher during large depletions than during small depletions. Although [Ca2+]SR exerts major influence on SR Ca2+ release, alternations in [Ca2+](SR) are not required for Ca2+ alternans to occur. Rather, it seems likely that some other factor, such as ryanodine receptor availability after a prior beat (eg, recovery from inactivation), is of greater importance in initiating frequency-induced Ca2+ alternans. However, once such a weak SR Ca2+ release occurs, it can result in increased [Ca2+]SR and further enhance SR Ca2+ release at the next beat. In this way, diastolic [Ca2+]SR alternans can enhance frequency-induced Ca2+ alternans, even if they initiate by other means.