Peripheral Intravenous Waveform Analysis Responsiveness to Subclinical Hemorrhage in a Rat Model.

BACKGROUND: Early detection and quantification of perioperative hemorrhage remains challenging. Peripheral intravenous waveform analysis (PIVA) is a novel method that uses a standard intravenous catheter to detect interval hemorrhage. We hypothesize that subclinical blood loss of 2% of the estimated blood volume (EBV) in a rat model of hemorrhage is associated with significant changes in PIVA. Secondarily, we will compare PIVA association with volume loss to other static, invasive, and dynamic markers. METHODS: Eleven male Sprague Dawley rats were anesthetized and mechanically ventilated. A total of 20% of the EBV was removed over ten 5 minute-intervals. The peripheral intravenous pressure waveform was continuously transduced via a 22-G angiocatheter in the saphenous vein and analyzed using MATLAB. Mean arterial pressure (MAP) and central venous pressure (CVP) were continuously monitored. Cardiac output (CO), right ventricular diameter (RVd), and left ventricular end-diastolic area (LVEDA) were evaluated via transthoracic echocardiogram using the short axis left ventricular view. Dynamic markers such as pulse pressure variation (PPV) were calculated from the arterial waveform. The primary outcome was change in the first fundamental frequency (F1) of the venous waveform, which was assessed using analysis of variance (ANOVA). Mean F1 at each blood loss interval was compared to the mean at the subsequent interval. Additionally, the strength of the association between blood loss and F1 and each other marker was quantified using the marginal R2 in a linear mixed-effects model. RESULTS: PIVA derived mean F1 decreased significantly after hemorrhage of only 2% of the EBV, from 0.17 to 0.11 mm Hg, P = .001, 95% confidence interval (CI) of difference in means 0.02 to 0.10, and decreased significantly from the prior hemorrhage interval at 4%, 6%, 8%, 10%, and 12%. Log F1 demonstrated a marginal R2 value of 0.57 (95% CI 0.40-0.73), followed by PPV 0.41 (0.28-0.56) and CO 0.39 (0.26-0.58). MAP, LVEDA, and systolic pressure variation displayed R2 values of 0.31, and the remaining predictors had R2 values ≤0.2. The difference in log F1 R2 was not significant when compared to PPV 0.16 (95% CI -0.07 to 0.38), CO 0.18 (-0.06 to 0.04), or MAP 0.25 (-0.01 to 0.49) but was significant for the remaining markers. CONCLUSIONS: The mean F1 amplitude of PIVA was significantly associated with subclinical blood loss and most strongly associated with blood volume among the markers considered. This study demonstrates feasibility of a minimally invasive, low-cost method for monitoring perioperative blood loss.

Venous waveform analysis detects acute right ventricular failure in a rat respiratory arrest model.

BACKGROUND: Peripheral intravenous analysis (PIVA) has been shown to be more sensitive than central venous pressure (CVP) for detecting hemorrhage and volume overload. We hypothesized that PIVA is superior to CVP for detecting right ventricular (RV) failure in a rat model of respiratory arrest. METHODS: Eight Wistar rats were studied in accordance with the ARRIVE guidelines. CVP, mean arterial pressure (MAP), and PIVA were recorded. Respiratory arrest was achieved with IV Rocuronium. PIVA utilizes Fourier transform to quantify the amplitude of the peripheral venous waveform, expressed as the "f1 amplitude". RV diameter was measured with transthoracic echocardiography. RESULTS: RV diameter increased from 0.34 to 0.54 cm during arrest, p = 0.001, and returned to 0.33 cm post arrest, p = 0.97. There was an increase in f1 amplitude from 0.07 to 0.38 mmHg, p = 0.01 and returned to 0.08 mmHg, p = 1.0. MAP decreased from 119 to 67 mmHg, p = 0.004 and returned to 136 mmHg, p = 0.50. There was no significant increase in CVP from 9.3 mmHg at baseline to 10.5 mmHg during respiratory arrest, p = 0.91, and recovery to 8.6 mmHg, p = 0.81. CONCLUSIONS: This study highlights the utility of PIVA to detect RV failure in small-caliber vessels, comparable to peripheral veins in the human pediatric population. IMPACT: Right ventricular failure remains a diagnostic challenge, particularly in pediatric patients with small vessel sizes limiting invasive intravascular monitor use. Intravenous analysis has shown promise in detecting hypovolemia and volume overload. Intravenous analysis successfully detects right ventricular failure in a rat respiratory arrest model. Intravenous analysis showed utility despite utilizing small peripheral venous access and therefore may be applicable to a pediatric population. Intravenous analysis may be helpful in differentiating various types of shock.

Anesthetic Considerations for Patients With Williams Syndrome.

Williams syndrome (WS) is a relatively rare congenital disorder which manifests across multiple organ systems with a wide spectrum of severity. Cardiovascular anomalies are the most common and concerning manifestations of WS, with supravalvar aortic stenosis present in up to 70% of patients with WS. Although a relatively rare disease, these patients frequently require sedation or anesthesia for a variety of medical procedures. The risk of sudden death in this population is 25 to 100 times that of the general population, with many documented deaths associated with sedation or anesthesia. This increased risk coupled with a disproportionately frequent need for anesthetic care renders it prudent for the anesthesiologist to have a firm understanding of the manifestations of WS. In the following review, the authors discuss pertinent clinical characteristics of WS along with particular anesthetic considerations for the anesthesiologist caring for patients with WS presenting for non-cardiac surgery.

Apneic oxygenation via nasal cannula for intubation of a premature neonate with multiple airway anomalies.

Intubating a neonate under non-emergent conditions may be quite stressful, even for experienced providers, due to the potential for rapid oxygen desaturation. Pulmonary physiology and increased metabolic oxygen demand in this patient population contribute to accelerated oxygen desaturation during induction of anaesthesia and intubation. Using a nasal cannula, placed prior to induction of anaesthesia and left in place until the airway is secured, is a simple and effective way to provide apneic oxygenation and may help maintain adequate oxygen saturation. This technique may be particularly useful for patients who require additional time for intubation, including those with suspected difficult airways.

Evaluation of Dynamic Ultrasound for Arterial Access in Children Undergoing Cardiac Surgery.

OBJECTIVE: To evaluate the effect of dynamic ultrasound (US) on the need for surgical intervention to achieve successful arterial cannulation in the pediatric cardiac surgery population. DESIGN: Retrospective, observational study. SETTING: Single, academic, pediatric hospital in the United States. PARTICIPANTS: The study comprised 3,569 consecutive patients who had an arterial catheter placed in the operating room before undergoing congenital heart surgery between January 2004 and September 2016. INTERVENTIONS: Dynamic US was used in 2,064 cases (57.83%) to obtain arterial access. Arterial cannulation by palpation was performed in the remaining 37.8% of cases. Surgical cutdown for arterial access was required in 192 cases after failed cannulation attempts by the anesthesia team. MEASUREMENTS AND MAIN RESULTS: Use of US was associated with an overall decrease in the need for surgical access from 10.43% to 1.70% (p < 0.0001). In patients younger than 30 days, US decreased the rate of surgical access, from 19.62% to 2.65% (p < 0.0001). This significant decrease also was observed in patients 1 to 6 months old (13.93% v 3.73%; p < 0.0001), 7 to 12 months old (7.34% v 0.00%, p < 0.0001), and older than 2 years (1.12% v 0%; p = 0.0083). For children between 13 and 24 months old, there was no statistically significant benefit to using US for avoiding surgical access (3.33% v 0.79%; p = 0.1411). Throughout all age groups, use of US was associated with a significant improvement in optimal arterial line location, defined as placement in an upper extremity (73.75% v 91.13%; p < 0.0001). CONCLUSIONS: Dynamic US resulted in a significant reduction in surgical intervention to achieve arterial cannulation in children presenting for cardiac surgery.

Development of a Rescue Echocardiography Protocol for Noncardiac Surgery Patients.

Intraoperative transesophageal echocardiography (TEE) is a helpful diagnostic tool when hemodynamic compromise is encountered during noncardiac surgery. At our institution, a Rescue Echo Protocol was created to provide a structured means for requesting and performing a rescue TEE. We analyzed our institutional utilization of this service and found that it was used throughout the spectrum of patients' American Society of Anesthesiologists classifications and surgical services. We demonstrated that 72.9% of rescue examinations resulted in a change in management, supporting the use of TEE as a diagnostic tool during hemodynamic compromise.

Incidental Discovery of an Atypical Cardiac Tumor.

Primary cardiac tumors are rare, present in roughly 0.05% of the population. Cardiac papillary fibroelastoma (CPF) is the second most common, accounting for 10% of primary cardiac tumors.[1] Most cases of CPFs are discovered incidentally on autopsy; however, they may present clinically with systemic embolization or heart failure symptoms. The recommended treatment for symptomatic CPF patients is surgical resection.[1] Treatment in asymptomatic patients remains somewhat controversial with incidentally discovered tumors presenting a clinical dilemma. We present a case of an atypically located CPF that was discovered incidentally on intraoperative transesophageal echocardiography (TEE) during a routine coronary artery bypass graft operation. This case highlights several important points for cardiac anesthesiologists. The first is the importance of performing a comprehensive intraoperative TEE. Next, this case reinforces the broad utility of TEE for evaluation of intracardiac tumors. Finally, this case demonstrates the importance of precise localization of intracardiac tumors.

Successful pregnancy and delivery in a patient with Carney complex: implications for anesthesiologists.

Carney complex is an autosomal dominant condition with widespread manifestations, including cardiac myxomas, nerve sheath tumors, and endocrinopathies. Although often associated with infertility, there are several reports of successful pregnancies in patients with Carney complex. However, none of the previous reports describe anesthetic considerations. Herein, we present a patient with Carney complex who successfully delivered vaginally with labor epidural analgesia.