Outcomes of a Single Transverse Chest Roll for Prone Positioning Technique During Percutaneous Nephrolithotomy.

OBJECTIVE: To compare anesthetic parameters using a novel prone single transverse chest roll technique (STR) to the standard thoraco-pelvic dual transverse roll technique (DTR). METHODS: A retrospective review of 441 patients who underwent PCNL between 2018 and 2022 was performed. A total of 4 surgeons were included-surgeon 1 utilized the STR technique while surgeons 2, 3, and 4 used the DTR technique. Anesthetic parameters including end-tidal CO2 (ETCO2), mean arterial pressure (MAP), peak airway pressure (Ppeak), plateau airway pressure (Pplat), positive end-expiratory pressure (PEEP), oxygen saturation (SpO2), and tidal volume (TV) were compared between both groups at 0 (supine), 15-, 30-, and 60-minute post-intubation intervals. Mixed effects regression models with interaction and pairwise comparisons were made between both groups (P <.05). RESULTS: A total of 581 PCNLs were performed with 199 using STR and 382 using DTR. Surgery duration, ASA class, and age were similar amongst the STR and DTR groups. Estimated blood loss (59cc vs 83cc, P = .007) and length of stay (77 hrs vs 163 hrs, P = <.001) was significantly lower in the STR group. There was a significantly lower Ppeak, Pplat and TV in the STR compared to DTR group at 0, 15, 30, and 60 minutes (P <.001). CONCLUSION: Usage of a single transverse chest roll during prone PCNL appears to be a safe positioning method. STR patients had lower Ppeak and Pplat at all time points, which has been shown to be predictive of lower blood loss.

Evolving the [myoglobin, cytochrome b(5)] complex from dynamic toward simple docking: charging the electron transfer reactive patch.

We describe photoinitiated electron transfer (ET) from a suite of Zn-substituted myoglobin (Mb) variants to cytochrome b(5) (b(5)). An electrostatic interface redesign strategy has led to the introduction of positive charges into the vicinity of the heme edge through D/E → K charge-reversal mutation combinations at "hot spot" residues (D44, D60, and E85), augmented by the elimination of negative charges from Mb or b(5) by neutralization of heme propionates. These variations create an unprecedentedly large range in the product of the ET partners' total charges (-5 < -q(Mb)q(b(5)) < 40). The binding affinity (K(a)) increases 1000-fold as -q(Mb)q(b(5)) increases through this range and exhibits a surprisingly simple, exponential dependence on -q(Mb)q(b(5)). This is explained in terms of electrostatic interactions between a "charged reactive patch" (crp) on each partner's surface, defined as a compact region around the heme edge that (i) contains the total protein charge of each variant and (ii) encompasses a major fraction of the "reactive region" (Rr) comprising surface atoms with large matrix elements for electron tunneling to the heme. As -q(Mb)q(b(5)) increases, the complex undergoes a transition from fast to slow-exchange dynamics on the triplet ET time scale, with a correlated progression in the rate constants for intracomplex (k(et)) and bimolecular (k(2)) ET. This progression is analyzed by integrating the crp and Rr descriptions of ET into the textbook steady-state treatment of reversible binding between partners that undergo intracomplex ET and found to encompass the full range of behaviors predicted by the model. The generality of this approach is demonstrated by its application to the extensive body of data for the ET complex between the photosynthetic reaction center and cytochrome c(2). Deviations from this model also are discussed.

Photoinitiated singlet and triplet electron transfer across a redesigned [myoglobin, cytochrome b5] interface.

We describe a strategy by which reactive binding of a weakly bound, 'dynamically docked (DD)' complex without a known structure can be strengthened electrostatically through optimized placement of surface charges, and discuss its use in modulating complex formation between myoglobin (Mb) and cytochrome b(5) (b(5)). The strategy employs paired Brownian dynamics (BD) simulations, one which monitors overall binding, the other reactive binding, to examine [X --> K] mutations on the surface of the partners, with a focus on single and multiple [D/E --> K] charge reversal mutations. This procedure has been applied to the [Mb, b(5)] complex, indicating mutations of Mb residues D44, D60, and E85 to be the most promising, with combinations of these showing a nonlinear enhancement of reactive binding. A novel method of displaying BD profiles shows that the 'hits' of b(5) on the surfaces of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) progressively coalesce into two 'clusters': a 'diffuse' cluster of hits that are distributed over the Mb surface and have negligible electrostatic binding energy and a 'reactive' cluster of hits with considerable stability that are localized near its heme edge, with short Fe-Fe distances favorable to electron transfer (ET). Thus, binding and reactivity progressively become correlated by the mutations. This finding relates to recent proposals that complex formation is a two-step process, proceeding through the formation of a weakly bound encounter complex to a well-defined bound complex. The design procedure has been tested through measurements of photoinitiated ET between the Zn-substituted forms of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) and Fe(3+)b(5). Both mutants convert the complex from the DD regime exhibited by Mb(WT), in which the transient complex is in fast kinetic exchange with its partners, k(off) >> k(et), to the slow-exchange regime, k(et) >> k(off), and both mutants exhibit rapid intracomplex ET from the triplet excited state to Fe(3+)b(5) (rate constant, k(et) approximately 10(6) s(-1)). The affinity constants of the mutant Mbs cannot be derived through conventional analysis procedures because intracomplex singlet ET quenching causes the triplet-ground absorbance difference to progressively decrease during a titration, but this effect has been incorporated into a new procedure for computing binding constants. Most importantly, these measurements reveal the presence of fast photoinduced singlet ET across the protein-protein interface, (1)k(et) approximately 2 x 10(8) s(-1).

Cognitive Aids for the Diagnosis and Treatment of Neuroanesthetic Emergencies: Consensus Guidelines on Behalf of the Society for Neuroscience in Anesthesiology and Critical Care (SNACC) Education Committee.

Cognitive aids and evidence-based checklists are frequently utilized in complex situations across many disciplines and sectors. The purpose of such aids is not simply to provide instruction so as to fulfill a task, but rather to ensure that all contingencies related to the emergency are considered and accounted for and that the task at hand is completed fully, despite possible distractions. Furthermore, utilization of a checklist enhances communication to all team members by allowing all stakeholders to know and understand exactly what is occurring, what has been accomplished, and what remains to be done. Here we present a set of evidence-based critical event cognitive aids for neuroanesthesia emergencies developed by the Society for Neuroscience in Anesthesiology and Critical Care (SNACC) Education Committee.