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.

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.

Intraoperative diagnosis of type 1 diabetes and diabetic ketoacidosis during scoliosis surgery.

Diabetic ketoacidosis is the leading cause of morbidity and mortality in children with type 1 diabetes. Management of diabetic ketoacidosis requires meticulous monitoring and treatment of severe dehydration and metabolic derangement. We present an adolescent patient who was diagnosed with diabetic ketoacidosis during spinal fusion for idiopathic scoliosis and discuss the management of this unexpected intraoperative emergency.

An Unusual Finding in a Patient Presenting for Pulmonary Thromboendarterectomy: Pulmonary Venous Thrombosis.

Pulmonary venous thrombosis (PVT) is a rare but potentially devastating disease state with a largely unknown incidence. The most common etiologies of PVT are secondary to complications of lung surgery, malignancy, catheter ablation for atrial fibrillation, and idiopathic causes. Diagnosis can be challenging because presenting symptoms often are vague and nonspecific, or even asymptomatic, and traditional diagnostic modalities, such as chest radiography and arterial phase computed tomography scans, are poor techniques for diagnosis. The authors present a case of a patient presenting for pulmonary thromboendarterectomy for a presumed diagnosis of chronic thromboembolic pulmonary hypertension who was found incidentally to have a PVT, on intraoperative transesophageal echocardiography. Due to significant thrombus burden, the new finding of PVT, and known association of PVT and malignancy, a biopsy of mediastinal lymph nodes was obtained, which revealed metastatic cervical carcinoma. The pulmonary endarterectomy procedure was aborted.

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.

Unintended ICD discharge in a patient undergoing bladder tumor resection utilizing monopolar cautery and full-body return electrode.

Patients with cardiac implantable electronic devices (CIED) and implantable cardioverter-defibrillator (ICD) devices frequently present for surgical procedures. If electrocautery is used, careful planning is needed to avoid inappropriate device function or device damage. Published consensus statements suggest that if the surgery is below the umbilicus, interference is typically minimal, and therefore it is not recommended to reprogram or disable the CIED. When these guidelines were published, full-body return electrodes were not commonly used in clinical practice, and therefore were not addressed in the recommendations. A 76-year-old male with a single chamber ICD underwent bladder surgery under general anesthesia. Monopolar cautery was used with a full-body return electrode. The patient had undergone a similar procedure multiple times prior utilizing a traditional thigh adhesive return electrode without any inappropriate ICD discharges. During the procedure, the patient's movement was noted with electrocautery use which was suspected to be an inappropriate discharge of his ICD. Device interrogation was performed confirming two antitachycardia pacing therapies and four defibrillations due to interference from the electrocautery. This case examines inappropriate ICD discharge related to interference from electrocautery when utilizing a full-body return electrode, despite a subumbilical location of surgery. Current consensus statement guidelines do not recommend device reprogramming or magnet used when surgery is below the umbilicus, however, these full-body return electrodes were not routinely used when these guidelines were published. Based on these results, the authors avoid full-body return electrodes in patients with CIEDs.

Observational Study of Noninvasive Venous Waveform Analysis to Assess Intracardiac Filling Pressures During Right Heart Catheterization.

BACKGROUND: Outpatient monitoring and management of patients with heart failure (HF) reduces hospitalizations and health care costs. However, the availability of noninvasive approaches to assess congestion is limited. Noninvasive venous waveform analysis (NIVA) uses a unique physiologic signal, the morphology of the venous waveform, to assess intracardiac filling pressures. This study is a proof of concept analysis of the correlation between NIVA value and pulmonary capillary wedge pressure (PCWP) and the ability of the NIVA value to predict PCWP > 18 mmHg in subjects undergoing elective right heart catheterization (RHC). PCWP was also compared across common clinical correlates of congestion. METHODS AND RESULTS: A prototype NIVA device, which consists of a piezoelectric sensor placed over the skin on the volar aspect of the wrist, connected to a data-capture control box, was used to collect venous waveforms in 96 patients during RHC. PCWP was collected at end-expiration by an experienced cardiologist. The venous waveform signal was transformed to the frequency domain (Fourier transform), where a ratiometric algorithm of the frequencies of the pulse rate and its harmonics was used to derive a NIVA value. NIVA values were successfully captured in 83 of 96 enrolled patients. PCWP ranged from 4-40 mmHg with a median of 13 mmHg. NIVA values demonstrated a linear correlation with PCWP (r = 0.69, P < 0.05). CONCLUSIONS: This observational proof-of-concept study using a prototype NIVA device demonstrates a moderate correlation between NIVA value and PCWP in patients undergoing RHC. NIVA, thus, represents a promising developing technology for noninvasive assessment of congestion in spontaneously breathing patients.

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.

Hyperlactemia Predicts Surgical Mortality in Patients Presenting With Acute Stanford Type-A Aortic Dissection.

OBJECTIVE: Inspired by the limited facility of the Penn classification, the authors aimed to determine a rapid and optimal preoperative assessment tool to predict surgical mortality after acute Stanford type-A aortic dissection (AAAD) repair. DESIGN: Patients who underwent an attempted surgical repair of AAAD were determined using a de-identified single institution database. The charts of 144 patients were reviewed retrospectively for preoperative demographics and surrogates for disease severity and malperfusion. Bivariate analysis was used to determine significant (p≤0.05) predictors of in-hospital and 1-year mortality, the primary endpoints. Receiver operating characteristic curve generation was used to define optimal cut-off values for continuous predictors. SETTING: Single center, level 1 trauma, university teaching hospital. PARTICIPANTS: The study included 144 cardiac surgical patients with acute type-A aortic dissection presenting for surgical correction. INTERVENTIONS: Surgical repair of aortic dissection with preoperative laboratory samples drawn before patient transfer to the operating room or immediately after arterial catheter placement intraoperatively. MEASUREMENTS AND MAIN RESULTS: The study cohort comprised 144 patients. In-hospital mortality was 9%, and the 1-year mortality rate was 17%. Variables that demonstrated a correlation with in-hospital mortality included an elevated serum lactic acid level (odds ratio [OR] 1.5 [1.3-1.9], p<0.001), a depressed ejection fraction (OR 0.91 [0.86-0.96], p = .001), effusion (OR 4.8 [1.02-22.5], p = 0.04), neurologic change (OR 5.3 [1.6-17.4], p = 0.006), severe aortic regurgitation (OR 8.2 [2.0-33.9], p = 0.006), and cardiopulmonary resuscitation (OR 6.8 [1.7-26.9], p = 0.01). Only an increased serum lactic acid level demonstrated a trend with 1-year mortality using univariate Cox regression (hazard ratio 1.1 [1.0-1.1], p = 0.006). Receiver operating characteristic analysis revealed optimal cut-off lactic acid levels of 6.0 mmol/L and 6.9 mmol/L for in-hospital and 1-year mortality, respectively. CONCLUSION: Lactic acidosis, ostensibly as a surrogate for systemic malperfusion, represents a novel, accurate, and easily obtainable preoperative predictor of short-term mortality after attempted AAAD repair. These data may improve identification of patients who would not benefit from surgery.

Prediction of Prolonged Ventilation after Coronary Artery Bypass Grafting: Data from an Artificial Neural Network.

OBJECTIVES: The need for mechanical ventilation 24 hours after coronary artery bypass grafting (CABG) is considered a morbidity by the Society of Thoracic Surgeons. The purpose of this investigation was twofold: to identify simple preoperative patient factors independently associated with prolonged ventilation and to optimize prediction and early identification of patients prone to prolonged ventilation using an artificial neural network (ANN). METHODS: Using the institutional Adult Cardiac Database, 738 patients who underwent CABG since 2005 were reviewed for preoperative factors independently associated with prolonged postoperative ventilation. Prediction of prolonged ventilation from the identified variables was modeled using both "traditional" multiple logistic regression and an ANN. The two models were compared using Pearson r2 and area under the curve (AUC) parameters. RESULTS: Of 738 included patients, 14% (104/738) required mechanical ventilation ≥ 24 hours postoperatively. Upon multivariate analysis, higher body-mass index (BMI; odds ratio [OR] 1.10 per unit, P < 0.001), lower ejection fraction (OR 0.97 per %, P = 0.01) and use of cardiopulmonary bypass (OR 2.59, P = 0.02) were independently predictive of prolonged ventilation. The Pearson r2 and AUC of the multivariate nominal logistic regression model were 0.086 and 0.698 ± 0.05, respectively; analogous statistics of the ANN model were 0.159 and 0.732 ± 0.05, respectively.BMI, ejection fraction and cardiopulmonary bypass represent three simple factors that may predict prolonged ventilation after CABG. Early identification of these patients can be optimized using an ANN, an emerging paradigm for clinical outcomes modeling that may consider complex relationships among these variables.

Race as a predictor of delay from diagnosis to endarterectomy in clinically significant carotid stenosis.

OBJECTIVE: Prompt carotid endarterectomy (CEA) in clinically significant carotid stenosis is important in the prevention of neurologic sequelae. The greatest benefit from surgery is obtained by prompt revascularization on diagnosis. It has been demonstrated that black patients both receive CEA less frequently than white patients do and experience worse postoperative outcomes. We sought to test our hypothesis that black race is an independent risk factor for a prolonged time from sonographic diagnosis of carotid stenosis warranting surgery to the day of operation (TDO). METHODS: From 1998 to 2013 at a single institution, 166 CEA patients were retrospectively reviewed using Synthetic Derivative, a de-identified electronic medical record. Factors potentially affecting TDO, including demographics, preoperative cardiac stress testing, degree of stenosis, smoking status, and comorbidities, were noted. Multivariate analysis was performed on variables that trended with prolonged TDO on univariate analysis (P < .10) to determine independent (P < .05) predictors of TDO. Subgroup analyses were further performed on the symptomatic and asymptomatic stenosis cohorts. RESULTS: There were 32 black patients and 134 white patients studied; the mean TDO was 78 ± 17 days vs 33 ± 3 days, respectively (P < .001). In addition to the need for preoperative cardiac stress testing, black race was the only variable that demonstrated a trend with (P < .10) or was an independent risk factor for (P < .05) prolonged TDO among all patients (B = 42 days; P < .001) and within the symptomatic (B = 35 days; P = .08) and asymptomatic (B = 35 days; P = .003) cohorts. On Kaplan-Meier analysis, black patients in each stratum of symptomatology (all, symptomatic, and asymptomatic patients) experienced prolonged TDO (log-rank, P < .03 for all three groups). CONCLUSIONS: Black race is a risk factor for a temporal delay in CEA for carotid stenosis. Awareness of this disparity may help surgeons avoid undesirable delays in operation for their black patients.

High central venous pressure amplitude predicts successful defibrillation in a porcine model of cardiac arrest.

AIM: Increasing venous return during cardiopulmonary resuscitation (CPR) has been shown to improve hemodynamics during CPR and outcomes following cardiac arrest (CA). We hypothesized that a high central venous pressure amplitude (CVP-A), the difference between the maximum and minimum central venous pressure during chest compressions, could serve as a robust predictor of return of spontaneous circulation (ROSC) in addition to traditional measurements of coronary perfusion pressure (CPP) and end-tidal CO2 (etCO2) in a porcine model of CA. METHODS: After 10 min of ventricular fibrillation, 9 anesthetized and intubated female pigs received mechanical chest compressions with active compression/decompression (ACD) and an impedance threshold device (ITD). CPP, CVP-A and etCO2 were measured continuously. All groups received biphasic defibrillation (200 J) at minute 4 of CPR and were classified into two groups (ROSC, NO ROSC). Mean values were analyzed over 3 min before defibrillation by repeated-measures Analysis of Variance and receiver operating characteristic (ROC). RESULTS: Five animals out of 9 experienced ROSC. CVP-A showed a statistically significant difference (p = 0.003) between the two groups during 3 min of CPR before defibrillation compared to CPP (p = 0.056) and etCO2 (p = 0.064). Areas-under-the-curve in ROC analysis for CVP-A, CPP and etCO2 were 0.94 (95% Confidence Interval 0.86, 1.00), 0.74 (0.54, 0.95) and 0.78 (0.50, 1.00), respectively. CONCLUSION: In our study, CVP-A was a potentially useful predictor of successful defibrillation and return of spontaneous circulation. Overall, CVP-A could serve as a marker for prediction of ROSC with increased venous return and thereby monitoring the beneficial effects of ACD and ITD.

Venous Waveform Analysis Correlates With Echocardiography in Detecting Hypovolemia in a Rat Hemorrhage Model.

BACKGROUND: Assessing intravascular hypovolemia due to hemorrhage remains a clinical challenge. Central venous pressure (CVP) remains a commonly used monitor in surgical and intensive care settings for evaluating blood loss, despite well-described pitfalls of static pressure measurements. The authors investigated an alternative to CVP, intravenous waveform analysis (IVA) as a method for detecting blood loss and examined its correlation with echocardiography. METHODS: Seven anesthetized, spontaneously breathing male Sprague Dawley rats with right internal jugular central venous and femoral arterial catheters underwent hemorrhage. Mean arterial pressure (MAP), heart rate, CVP, and IVA were assessed and recorded. Hemorrhage was performed until each rat had 25% estimated blood volume removed. IVA was obtained using fast Fourier transform and the amplitude of the fundamental frequency (f1) was measured. Transthoracic echocardiography was performed utilizing a parasternal short axis image of the left ventricle during hemorrhage. MAP, CVP, and IVA were compared with blood removed and correlated with left ventricular end diastolic area (LVEDA). RESULTS: All 7 rats underwent successful hemorrhage. MAP and f1 peak amplitude obtained by IVA showed significant changes with hemorrhage. MAP and f1 peak amplitude also significantly correlated with LVEDA during hemorrhage (R = 0.82 and 0.77, respectively). CVP did not significantly change with hemorrhage, and there was no significant correlation between CVP and LVEDA. CONCLUSIONS: In this study, f1 peak amplitude obtained by IVA was superior to CVP for detecting acute, massive hemorrhage. In addition, f1 peak amplitude correlated well with LVEDA on echocardiography. Translated clinically, IVA might provide a viable alternative to CVP for detecting hemorrhage.