Accuracy and clinical utility of heart rate variability derived from a wearable heart rate monitor in patients undergoing major abdominal surgery.

Low heart rate variability (HRV) can potentially identify patients at risk of intraoperative hypotension. However, it is unclear whether cheaper, readily accessible consumer heart rate (HR) monitors can provide similar utility to clinical Holter electrocardiograph (ECG) monitors. The objectives of this study were (1) to assess the validity of using the Polar H10 HR monitor as an alternative to a clinical Holter ECG and (2) to test total power (TP) as a predictor of intraoperative hypotension. The primary outcome was the level of agreement between Polar H10 and Holter ECG. Twenty-three patients undergoing major abdominal surgery with general anesthesia had 5-minute HR recordings taken concurrently with both devices during a pre-anesthetic consultation. Agreement between Polar H10 and Holter ECG was compared via Bland-Altman analysis and Lin's Concordance Correlation Coefficient. Patients were divided into groups based on TP < 500 m s 2 and TP > 500 m s 2 . Intraoperative hypotension was defined as MAP < 60 mmHg, systolic blood pressure < 80 mmHg, or 35% decrease in MAP from baseline. There was substantial agreement between Polar H10 and Holter ECG for average R-R interval, TP and other HRV indices. Reduced TP (< 500 ms 2 ) had a high sensitivity (80%) and specificity (100%) in predicting intraoperative hypotension. Patients with reduced TP were significantly more likely to require vasoactive drugs to maintain blood pressure.The substantial agreement between Polar H10 and Holter ECG may justify its use clinically. The use of preoperative recordings of HRV has the potential to become part of routine preoperative assessment as a useful screening tool to predict hemodynamic instability in patients undergoing general anesthesia.

Smaller rectus femoris size measured by ultrasound is associated with poorer outcomes after cardiac surgery.

OBJECTIVE: We sought to evaluate the association of low rectus femoris cross-sectional area (RFCSA) with hospital length of stay and poorer outcomes in patients undergoing cardiac surgery. METHODS: A single right-leg RFCSA was measured with ultrasound preoperatively and baseline characteristics, clinical data, and outcomes recorded. Patients were categorized as low rectus femoris muscle size (lowRF) or normal rectus femoris muscle size (normalRF), if they were in the lowest quartile or not, respectively. All analyses were performed on both body surface area (BSA)- and sex-adjusted RFCSA. RESULTS: One hundred eight-four patients had a RFCSA measured with a mean of 5.01 cm2 (1.41 cm2), and range of 0.71 to 8.77 cm2. When analyzing the BSA-adjusted RFCSA, we found the lowRF group had a longer hospital stay, 11.0 days [7.0-16.3] versus 8.0 days [6.0-10.0] for the normalRF group (P < .001), and a greater proportion of extended hospital stay (≥18.5 days) of 19.6% compared with 6.2% (P = .010). When the RFCSA was adjusted for sex, the lowRF group had a greater length of hospital stay, 9.0 days [7.0-14.5] versus 8.0 days [6.0-11.0] (P = .049). In both the BSA- and sex-adjusted RFCSA, the lowRF group suffered greater morbidity and were more likely discharged to a destination other than home. In multivariate analyses adjusting for European System for Cardiac Operative Risk Evaluation II, BSA-adjusted lowRF but not sex-adjusted lowRF was independently associated with log-transformed hospital length of stay. LowRF was not independently associated with increased major morbidity and death for both BSA and sex-adjusted RFCSA. CONCLUSIONS: Low RFCSA has a significant association with increased hospital length of stay, morbidity, and nonhome discharge in patients undergoing cardiac procedures. TRIAL REGISTRY NUMBER: ACTRN12620000678998.

Carbon Dioxide Elimination After Sodium Bicarbonate Administration as a Novel Method to Assess Cardiac Output: A Pilot Study.

Introduction Cardiac output/pulmonary blood flow measurement is an important way to assess patients during the perioperative period, as well as patients who are critically ill. Current methods of assessing cardiac output have limitations. One indicator of cardiac output may be the expired carbon dioxide (CO2) partial pressure response to intravenous sodium bicarbonate (IVSB), which is rapidly converted to CO2. Methods We conducted an initial evaluation of the relationship between expired CO2 partial pressure and blood flow after a bolus of IVSB. To assess this relationship, we used a cardiopulmonary bypass circuit with predetermined blood flows in a laboratory trial and then assessed 18 patients undergoing surgery requiring cardiopulmonary bypass. Results For the laboratory portion of this pilot study, higher peak expired CO2, faster time to reach peak, higher area under the curve, and greater kurtosis of peak were observed at higher cardiac output flow rates, and higher mean expired CO2 was significantly associated with higher flow rates (p < 0.001). In the human study, higher mean (p = 0.023) and peak expired CO2 (p = 0.028) were both significantly associated with higher cardiac output flow rates. Conclusions This technique may be a way to intermittently assess cardiac output or improve accuracy when used in conjunction with other continuous output monitors.

High-flow Nasal Oxygen Versus Standard Oxygen During Flexible Bronchoscopy in Lung Transplant Patients: A Randomized Controlled Trial.

BACKGROUND: Diagnostic and interventional flexible bronchoscopy (FB) is increasingly utilized in complex and high-risk patients. Patients are often sedated for comfort and procedure facilitation and hypoxia is commonly observed in this setting. We hypothesized that high-flow nasal oxygen (HFNO) would reduce the incidence of patients experiencing oxygen desaturation. METHODS: In this randomized controlled trial, postlung transplant patients booked for FB with transbronchial lung biopsy were assigned to either HFNO or low-flow nasal oxygen (LFNO). The patient and bronchoscopist were blinded to group allocation. The primary endpoint was the proportion of patients experiencing mild desaturation [peripheral oxygen saturation (SpO2)<94%]. Secondary endpoints included desaturation (SpO2<90%), the number of airway interventions required and procedure interruptions, the duration of oxygen desaturation and patient, bronchoscopist and anesthesiologist satisfaction scores. RESULTS: The trial analyzed data from 76 patients (LFNO, n=39; HFNO, n=37). HFNO reduced the proportion of patients experiencing SpO2<94% (43.2% vs. 89.7%, P<0.001) and SpO2<90% (16.2% vs. 69.2%, P<0.001). The FB was interrupted 11 times in 9 patients in the LFNO group, whereas there were no interruptions in the HFNO group. There were no differences in patient and bronchoscopist satisfaction scores between groups, anesthesiologists had higher satisfaction scores when using HFNO (P<0.001). CONCLUSION: Hypoxia occurred less commonly in postlung transplant patients receiving HFNO during FB. Further studies are warranted in other high-risk populations undergoing longer duration FB.

Anesthetic Management of Staged Bilateral Adrenalectomy for Neuroendocrine Tumors in a Heart-Lung Transplant Patient: A Case Report.

Neuroendocrine tumors may rarely present after organ transplantation, including cardiac transplant. Treatment is surgical resection with careful perioperative management to optimize blood pressure and intravascular volume. We present the anesthetic management of a patient who was diagnosed with bilateral neuroendocrine tumors soon after heart-lung transplantation and underwent successful staged bilateral adrenalectomy.

The effect of intravenous lidocaine infusion on bispectral index during major abdominal surgery.

Intraoperative lidocaine infusion has become widely accepted as an adjunct to general anesthesia where its use has been associated with opioid-sparing and enhanced recovery. The aims of this study were to determine whether or not intravenous (IV) lidocaine infusion (a) has an anesthetic sparing effect during major colorectal procedures and (b) if it also affects level of hypnosis as measured by bispectral index (BIS). Twenty-five patients undergoing laparotomy for resection of colorectal tumours were randomized to receive either IV lidocaine (1.5 mg kg-1 bolus then 1 mg kg-1 per hour) or an equivalent volume of normal saline commenced after intravenous induction of general anesthesia. Anesthesia was maintained with volatile anesthetic agent combined with intermittent IV fentanyl titrated to hemodynamic stability. Minimum alveolar concentration (MAC) of volatile was calculated using an age-adjusted algorithm (corrected MAC). BIS values were recorded throughout; however, treating anesthesiologists were blinded to BIS values and hence they were not used to guide depth of anesthesia. No other regional anesthesia techniques were used. During the maintenance phase of anesthesia, corrected MAC of volatile agent was lower (1.0 versus 1.1, p = 0.003); whereas BIS values were higher (45 versus 39, p < 0.001) in patients who received lidocaine versus placebo. No differences in mean arterial pressure (80 versus 80 mmHg, p = 0.796) or total fentanyl dose (538 versus 444 mcg, p = 0.24) were observed between the two groups. Heart rate was slightly higher in patients who received lidocaine versus placebo (67 versus 64 bpm, p = 0.001). Lidocaine infusion resulted in mean plasma levels of 1.7 mcg ml-1 (1.3-2.0 mcg ml-1, 95% CI). Our results support an anesthetic sparing effect of lidocaine infusion indicated by lower MAC requirements. Higher BIS values in the lidocaine versus placebo group may indicate that levels of hypnosis were not equivalent. Alternatively, BIS may not be a sensitive indicator of synergistic interactions between local anesthetic and volatile agent. Our results advocate a cautious approach to titration of general anesthesia when combined with lidocaine infusion.

Lung Ultrasound After Transbronchial Biopsy for Pneumothorax Screening in Post-Lung Transplant Patients.

BACKGROUND: Lung ultrasound has been suggested as an alternative to routine chest radiography (CXR) to screen for pneumothorax after transbronchial lung biopsy. In post-lung transplant patients, who may have altered anatomy and pleural adhesions, the validity of lung ultrasound to screen for postbiopsy pneumothoraces has not been investigated. METHODS: Lung ultrasound using an ultraportable handheld device was performed in a standardized manner 2-hour after biopsy in post-lung transplant patients. Ultrasound assessment was then compared with CXR performed immediately after lung ultrasound. RESULTS: In total, 165 patients were enrolled in the study. Eight pneumothoraces were diagnosed by image intensifier or CXR before lung ultrasound. There were 8 pneumothoraces diagnosed on CXR 2-hour postbiopsy. Lung ultrasound had a sensitivity of 75% and specificity of 93%. Positive predictive value was 35% and negative predictive value was 99%. The mean number of biopsies taken in patients with and without a pneuomothorax on CXR was 10.6 (±3.1) and 10.9 (±2.1), respectively (P=0.79). The overall pneumothorax rate was 9.7%. CONCLUSIONS: Lung ultrasound is a valid tool in excluding penumothoraces after lung biopsy. Ultrasound scans with features of a pneumothorax or patients with symptoms should still undergo CXR. The high false positive rate may be due to small pneumothoraces being seen or the presence of pleural adhesions and altered lung anatomy in post-lung transplant patients.

Low pre-operative heart rate variability and complexity are associated with hypotension after anesthesia induction in major abdominal surgery.

Significant hypotension after induction of general anesthesia is common and has the potential for serious complications. This study aimed to determine if pre-operative heart rate variability (HRV) was associated with post-induction hypotension in patients undergoing major abdominal surgery. Patients undergoing semi-elective major abdominal surgery were consecutively recruited during pre-admission clinic assessment. Exclusion criteria included cardiac conduction disease, arrhythmias or severe liver or renal disease. Ten minutes of electrocardiogram at 1024 Hz were recorded a median of 3 days pre-operatively. Pre-operative HRV parameters were compared in patients who experienced significant hypotension (fall in systolic and mean arterial pressure (MAP) >30% baseline and MAP ≤60 mmHg) versus those who remained haemodynamically stable after induction of general anesthesia with propofol and fentanyl. Patients who experienced hypotension after general anesthesia induction had significantly lower pre-operative HRV (SDNN 16 vs. 37 ms, p < 0.001), reduced spectral power (total power 262 vs. 1236 ms2, p = 0.002) and reduced correlation dimension, a measure of signal complexity (0.11 vs. 2.13, p < 0.001). Hypotension occurred relatively frequently in our cohort and was associated with a higher ASA grade (36 vs. 6% ASA 3, p = 0.036), hence post-induction hypotension and lower HRV may be associated with severity of illness or poor physiological reserve. Pre-operative HRV was a useful screening tool in identifying patients undergoing major abdominal surgery who were at risk of haemodynamic instability after anesthesia induction.

Evaluation of Miniature Dynamic Light Scattering Technology for the Assessment of Hemodynamic Status During Graded Hemorrhage and Retransfusion in Pigs.

BACKGROUND: Hemorrhagic shock with occult hypoperfusion is a key challenge to prehospital staff during triage and transfer of patients, especially during mass casualty incidents. Recent advances in Dynamic Light Scattering (DLS), and miniaturization of this technology, has resulted in noninvasive sensors capable of continuously monitoring tissue perfusion. This study evaluated the ability of miniature DLS (mDLS) sensors to assess hemodynamic status in a porcine model of hemorrhage. METHODS: Following ethics committee approval, anesthetized and ventilated pigs underwent graded hemorrhage and then retransfusion. Standard vital signs were monitored in conjunction with a thermodilution cardiac output (CO), central venous pressure (CVP), and arterial blood gases. The mDLS sensor was attached to each animal's leg and all monitoring measurements were taken 5 minutes after completion of each period of hemorrhage and retransfusion to allow equilibration. RESULTS: All measured parameters changed during bleeding and retransfusion. During bleeding; p value were 0.011 for heart rate, 0.07 for CVP, <0.001 for both mean arterial pressure, and mDLS. During retransfusion; p values were 0.023 for heart rate, 0.008 for CVP, and <0.001 for both mean arterial pressure and mDLS. Pearson correlation between changes in mDLS and CO demonstrated r value of 0.917 during hemorrhage and 0.965 during retransfusion. Changes in hemoglobin were not statistically significant during bleeding (p = 0.331) but were during retransfusion (p = 0.0001). Changes of bicarbonate, base excess, and lactate were found to be statistically significant during both phases of the experiment (p = 0.001). CONCLUSIONS: In an animal model of hemorrhagic shock, the mDLS sensor strongly correlates with traditional measures of CO. This initial assessment supports further investigation of this technology in human studies.

A cross-sectional study of preoperative medication adherence and early postoperative recovery.

STUDY OBJECTIVE: To quantify the impact of preoperative medication adherence on recovery length of stays and complication rates. DESIGN: Cross-sectional analytical study. SETTING: Postanesthetic care unit (PACU) of a single-center tertiary hospital. PATIENTS: Surgical patients admitted for surgery at our institution over a 4-month period. INTERVENTION: A data collection tool was used to collect demographic data, length of stay in recovery, prespecified conditions likely to impact on PACU recovery (chronic pain, insulin-dependent diabetes, epilepsy, hypertension, on a methadone program, and Parkinson disease), medication compliance, and complications in PACU. MEASUREMENTS: Differences among categorical variables were assessed for significance using the χ2 test; continuous parametric data were compared using a time to survival analysis via Kaplan-Meier estimates and Cox proportional hazard regressions to account for possible confounders. MAIN RESULTS: Preoperative medication compliance for the prespecified conditions was 65.1%. Patients with a preoperative condition spent more time in the PACU compared to patients without a preoperative condition. Time in PACU was not significantly longer for patients who took their medications compared to those who failed to take their medications. Patients with multiple prespecified conditions were more likely to incur a postoperative complication compared to patients without a prespecified condition. Patients with preoperative hypertension and insulin-dependent diabetes incurred higher complication rates in PACU for medication nonadherence compared to medication adherence. CONCLUSION: This study taken together with accruing evidence suggests that preoperative medication omission remains an ongoing issue that can influence complication rates in the PACU. Patients with preoperative conditions stay longer in PACU, and medication omission was associated with higher rates of certain postoperative complications in PACU. This identifies patients likely to require more interventions and greater recovery resources. Further research into the impact of medication omission on recovery parameters after discharge from the PACU is warranted.

A Simple Diagnostic Test to Confirm Correct Placement of Dysfunctional Central Venous Catheters Before Chemotherapy in Children.

BACKGROUND: In children undergoing intravenous chemotherapy, partial dysfunction of the central venous catheter (CVC) is common. Fluids can be infused into the catheter; however, blood cannot be aspirated. In those situations, chemotherapy is withheld and a catheter investigation is performed. Usually, a radiographic study with contrast media or therapy with thrombolytic drugs followed by rechecking for blood return is undertaken. AIM: To evaluate if a previously described method using dilute sodium bicarbonate injection and the resultant rise in measured end-tidal carbon dioxide tracing can confirm correct intravascular placement of a dysfunctional CVC in children at the bedside. PATIENTS: Cohort group of 22 children scheduled for chemotherapy with partial dysfunction of a CVC in a tertiary hematology-oncology care facility. RESULTS: All children with a partial dysfunctional CVC that was proven to be intravascular after venogram or thrombolytic therapy had a distinct and predictable increase in end-tidal carbon dioxide response to injected bicarbonate. CONCLUSION: Injection of 1 mL/kg (maximum 20 mL) of 4.2% dilute sodium bicarbonate is a quick, simple, bedside test allowing confirmation of intravascular location of dysfunctional CVC.

A simple diagnostic test to confirm correct intravascular placement of peripheral catheters in order to avoid extravasation.

BACKGROUND: Intravenous catheters are ubiquitous among modern medical management of patients, yet misplaced or tissued cannulas can result in serious iatrogenic injury due to infiltration or extravasation of injectate. Prevention is difficult, and currently few reliable tests exist to confirm intravascular placement of catheters in awake spontaneously breathing patients. METHODS: Twenty conscious spontaneously breathing healthy volunteers were injected with 50 mL normal saline and 50 mL 4.2%, or 50 mL 2.1%, or 20 mL 4.2% sodium bicarbonate in a random order. A blinded anesthetist observed continuous sampling of exhaled carbon dioxide and was asked to differentiate between the sodium bicarbonate and saline injections. Peak increase in measured exhaled carbon dioxide was also calculated. RESULTS: Exhaled carbon dioxide increased significantly in participants injected with intravenous sodium bicarbonate. Mean peak increase was 7.4 mm Hg (±2.1 mm Hg) for 50 mL 4.2% sodium bicarbonate, 4.7 mm Hg (±2.5 mm Hg) for 20 mL 4.2% sodium bicarbonate, and 3.5 mm Hg (±1. 8 mm Hg) for 50 mL 2.1% sodium bicarbonate. The blinded observer correctly identified the injection as sodium bicarbonate or normal saline in every instance. DISCUSSION: Intravenous injection of dilute sodium bicarbonate with exhaled carbon dioxide monitoring reliably confirms correct intravascular placement of a catheter. A transient increase of exhaled carbon dioxide by 10% or more is an objective and reliable confirmation of intravascular location of the catheter. We recommend using 20 mL of 4.2% sodium bicarbonate to minimize the mEq dose of sodium bicarbonate required.

A simple diagnostic test to confirm correct placement of intravenous catheters before chemotherapy.

PURPOSE: To determine the feasibility and effectiveness of using a single injection of diluted sodium bicarbonate, while monitoring exhaled carbon dioxide changes, to reliably confirm correct placement of intravenous (IV) catheters. METHODS: The study was conducted in the oncology day care clinic at a tertiary care center and included a selected group of patients with various oncological conditions who required IV chemotherapy. In each patient a newly inserted peripheral IV catheter or newly accessed central line was deemed positively intravascular if they had good blood return or most probably intravascular if there was no blood return but they flushed easily. This clinical diagnosis of correct positioning, was correlated with the results of a single injection of dilute sodium on the exhaled carbon dioxide, and with the ability of a blinded observer to report whether sodium bicarbonate or saline was injected. RESULTS: A total of 67 patients were enrolled in the study; 56 had positively intravascular IV catheter while 11 had most probably intravascular IV catheter. A single injection of 20 mL 4.2% sodium bicarbonate had a positive and clinically detectable response that was diagnosed with high sensitivity and specificity. CONCLUSIONS: IV injection of 20 mL of 4.2% sodium bicarbonate with exhaled carbon dioxide monitoring can be used to reliably confirm correct intravascular placement of a catheter intended to be used for chemotherapy.

Electroencephalography for children with autistic spectrum disorder: a sedation protocol.

OBJECTIVES: To report the effectiveness and efficiency of a predetermined sedation protocol for providing sedation for electroencephalograph (EEG) studies in children with autism. METHODS: Sleep EEG has been advocated for the majority of children with autism spectrum disorder. In most cases, sedation is required to allow adequate studies. Most sedation drugs have negative effects on the EEG pattern. The sedation protocol we adopted included chloral hydrate, dexmedetomidine, and ketamine and was evaluated prospectively for 2 years. RESULTS: One hundred and eighty-three children with autistic spectrum disorder were sedated with the described drug protocol that was efficient, provided adequate EEG readings, and was not associated with serious adverse events. CONCLUSIONS: Our protocol kept costs to a minimum but provided appropriate escalation in care when required.

Depth of anesthesia monitoring: a survey of attitudes and usage patterns among Australian anesthesiologists.

BACKGROUND: Utility of depth of anesthesia (DoA) monitors is contentious as evidence appears ambiguous regarding their clinical effectiveness and exact role. We conducted a survey of Australian anesthesiologists to determine their attitudes toward, and how and why they use, DoA monitors. METHODS: A random sample of 963 anesthesiologists was invited to participate in an anonymous online survey. RESULTS: The overall response rate was 30% (289 respondents). Twenty-nine percent (95% confidence interval, 24%-34%) of respondents thought DoA monitoring was indicated in all cases under relaxant general anesthesia. During total IV anesthesia with muscle relaxants, 74% of respondents (69%-79%) opined that DoA monitoring should be mandatory. DoA usage was never used by 5% of respondents (3%-8%), used in less than one-third of cases by 66% (61%-72%), and in more than one-third of cases by 29% (24%-35%). Belief in the usefulness of DoA monitoring for prevention of awareness was strongly associated with higher usage (P < 0.0001, Pearson correlation 0.32). Anesthesiologists were more influenced by higher DoA numbers than lower ones. In comparison with end-tidal anesthetic concentration monitoring, 30% (25%-35%) of respondents felt that DoA monitoring was more effective for prevention of intraoperative awareness. Thirty percent (25%-36%) of respondents reported having a previous case of awareness. CONCLUSIONS: The relatively frequent use of DoA monitoring contrasts with patterns in the UK, suggesting greater acceptance by Australian anesthesiologists. "Awareness prevention" rather than "recovery enhancement" appears to be the primary driver in DoA monitoring use in Australia. Highly variable usage patterns of DoA monitoring in the context of the current body of evidence suggest the need for greater education on the appropriate use of these monitors.