Validation of Preload Assessment Technologies at Altitude in a Porcine Model of Hemorrhage.

INTRODUCTION: Dynamic preload assessment measures including pulse pressure variation (PPV), stroke volume variation (SVV), pleth variability index (PVI), and hypotension prediction index (HPI) have been utilized clinically to guide fluid management decisions in critically ill patients. These values aid in the balance of correcting hypotension while avoiding over-resuscitation leading to respiratory failure and increased mortality. However, these measures have not been previously validated at altitude or in those with temporary abdominal closure (TAC). METHODS: Forty-eight female swine (39 ± 2 kg) were separated into eight groups (n = 6) including all combinations of flight versus ground, hemorrhage versus no hemorrhage, and TAC versus no TAC. Flight animals underwent simulated aeromedical evacuation via an altitude chamber at 8000 ft. Hemorrhagic shock was induced via stepwise hemorrhage removing 10% blood volume in 15-min increments to a total blood loss of 40% or a mean arterial pressure of 35 mmHg. Animals were then stepwise transfused with citrated shed blood with 10% volume every 15 min back to full blood volume. PPV, SVV, PVI, and HPI were monitored every 15 min throughout the simulated aeromedical evacuation or ground control. Blood samples were collected and analyzed for serum levels of serum IL-1ß, IL-6, IL-8, and TNF-α. RESULTS: Hemorrhage groups demonstrated significant increases in PPV, SVV, PVI, and HPI at each step compared to nonhemorrhage groups. Flight increased PPV (P = 0.004) and SVV (P = 0.003) in hemorrhaged animals. TAC at ground level increased PPV (P < 0.0001), SVV (P = 0.0003), and PVI (P < 0.0001). When TAC was present during flight, PPV (P = 0.004), SVV (P = 0.003), and PVI (P < 0.0001) values were decreased suggesting a dependent effect between altitude and TAC. There were no significant differences in serum IL-1ß, IL-6, IL-8, or TNF-α concentration between injury groups. CONCLUSIONS: Based on our study, PPV and SVV are increased during flight and in the presence of TAC. Pleth variability index is slightly increased with TAC at ground level. Hypotension prediction index demonstrated no significant changes regardless of altitude or TAC status, however this measure was less reliable once the resuscitation phase was initiated. Pleth variability index may be the most useful predictor of preload during aeromedical evacuation as it is a noninvasive modality.

How Informed Is Your Informed Consent: Evaluating Differences Between Resident and Attending Obtained Consents for Cholecystectomy.

OBJECTIVE: There is considerable variability in surgeons' approach to write and obtain informed consent for surgery, particularly among resident trainees. We analyzed differences in procedures and complications described in documented surgical consents for cholecystectomy between residents and attendings. We hypothesized that attending consents would describe more comprehensive procedures and complications than those done by residents. DESIGN: This is a retrospective analysis of 334 patients who underwent cholecystectomy. Charts were queried for demographics, surgical approach, whether the consent was completed electronically, and which provider completed the consent. Specifically, consents were evaluated for inclusion of possible conversion to open procedure, intraoperative cholangiogram, bile duct injury, injury to nearby structures, reoperation, bile leak, as well as if the consent matched the actual procedure performed. SETTING: This study was conducted at an accredited general surgery training program at an academic tertiary care center in the Midwest. PARTICIPANTS: This was a review of 334 patients who underwent cholecystectomy over a 1 year period. RESULTS: Of all documented consents analyzed, 153 (47%) specifically included possible intraoperative cholangiogram, 156 (47%) included bile duct injury, 76 (23%) included injury to nearby structures, 22 (7%) included reoperation, and 62 (19%) included bile leak. In comparing residents and attendings, residents were more likely to consent for bile duct injury (p = 0.002), possible intraoperative cholangiogram (p = 0.0007), injury to nearby structures (p < 0.0001), reoperation (p < 0.0001), and bile leak (p < 0.0001). CONCLUSIONS: Significant variation exists between documentation between resident and attending cholecystectomy consents, with residents including more complications than attendings on their consent forms. These data suggest that experience alone does not predict content of written consents, particularly for common ambulatory procedures. Education regarding the purpose of informed consent and what should be included in one may lead to a reduction in variability between providers.