Naveen G Singh

A comparison of a continuous noninvasive arterial pressure (CNAP™) monitor with an invasive arterial blood pressure monitor in the cardiac surgical ICU.

Accurate measurement and display of arterial blood pressure is essential for rational management of adult cardiac surgical patients. Because of the lower risk of complications, noninvasive monitoring methods gain importance. A newly developed continuous noninvasive arterial blood pressure (CNAP™) monitor is available and has been validated perioperatively. In a prospective study we compared the CNAP™ monitoring device with invasive arterial blood pressure (IAP) measurement in 30 patients in a cardiac surgical Intensive Care Unit (ICU). Patients were either mechanically ventilated or spontaneously breathing, with or without inotropes. CNAP™ was applied on two fingers of the hand contralateral to the IAP monitoring catheter. Systolic, diastolic and mean pressure data were recorded every minute for 2 h simultaneously for both IAP and CNAP™. Statistical analysis included construction of mountain plot and Bland Altman plots for assessing limits of agreement and bias (accuracy) calculation. Three thousand and six hundred pairs of data were analyzed. The CNAP™ systolic arterial pressure bias was 10.415 mmHg and the CNAP™ diastolic arterial pressure bias was -5.3386 mmHg; the mean arterial pressure (MAP) of CNAP™ was close to the MAP of IAP, with a bias of 0.03944 mmHg. The Bland Altman plot showed a uniform distribution and a good agreement of all arterial blood pressure values between CNAP™ and IAP. Percentage within limits of agreement was 94.5%, 95.1% and 99.4% for systolic, diastolic and MAP. Calculated limits of agreement were -4.60 to 25.43, -13.38 to 2.70 and -5.95 to 6.03 mmHg for systolic, diastolic and mean BP, respectively. The mountain plot showed similar results as the Bland Altman plots. We conclude CNAP™ is a reliable, noninvasive, continuous blood pressure monitor that provides real-time estimates of arterial pressure comparable to those generated by an invasive arterial catheter system. CNAP™ can be used as an alternative to IAP.

Evaluation of continuous non-invasive arterial pressure monitoring during induction of general anaesthesia in patients undergoing cardiac surgery

Background and Aims: Continuous arterial pressure monitoring is essential in cardiac surgical patients during induction of general anaesthesia (GA). Continuous non-invasive arterial pressure (CNAP) monitoring is fast gaining importance due to complications associated with the invasive arterial monitoring. Recently, a new continuous non-invasive arterial pressure device (CNAP™) has been validated perioperatively in non-cardiac surgeries. The aim of our study is to compare and assess the performance of CNAP during GA with invasive arterial pressure (IAP) in patients undergoing cardiac surgeries. Methods: Sixty patients undergoing cardiac surgery were included. Systolic, diastolic, and mean arterial pressure (MAP) data were recorded every minute for 20 min simultaneously for both IAP and CNAP™. Statistical analysis was performed using mountain plot and Bland Altman plots for assessing limits of agreement and bias (accuracy) calculation. Totally 1200 pairs of data were analysed. Results: The CNAP™ systolic, diastolic and MAP bias was 5.98 mm Hg, −3.72 mm Hg, and − 0.02 mm Hg respectively. Percentage within limits of agreement was 96.0%, 95.2% and 95.7% for systolic, diastolic and MAP. The mountain plot showed similar results as the Bland Altman plots. Conclusion: We conclude CNAP™ provides real-time estimates of arterial pressure comparable to IAP during induction of GA for cardiac surgery. We recommend CNAP can be used as an alternative to IAP in situations such as cardiac patients coming for non-cardiac surgeries, cardiac catheterization procedures, positive Allen′s test, inability to cannulate radial artery and vascular diseases, where continuous blood pressure monitoring is required.

Transesophageal echocardiography estimation of coronary sinus blood flow for the adequacy of revascularization in patients undergoing off-pump coronary artery bypass graft

Aims and Objectives: Physiologically coronary sinus (CS) drains the left coronary artery (LCA) territory. Stenosis of the branches of LCA may decrease the coronary sinus blood flow (CSBF). Any intervention that aims at restoring the flow of the stenosed vessel increases coronary artery flow that should consequently increase the CSBF. Hence, this study was undertaken to assess the CSBF before and after each branch of LCA to determine the adequacy of surgical revascularization in patients undergoing elective off pump coronary artery bypass grafting (OPCAB) using transesophageal echocardiography (TEE). Materials and Methods: Thirty consecutive patients scheduled for elective OPCAB were enrolled. CSBF was assessed before and after each branch of LCA revascularization using TEE. Left internal mammary artery (LIMA) Doppler was also obtained post LIMA to left anterior descending (LAD) grafting. Results: Hemodynamic and echocardiographic variables were compared by means of Students t-test for paired data before and after revascularization. The CSBF per beat (1.28 ± 0.71), CSBF per minute (92.59 ± 59.32) and total velocity time integral (VTI) (8.93 ± 4.29) before LAD grafting showed statistically significant increase to CSBF per beat (1.70 ± 0.89), CSBF per minute (130.72 ± 74.22) and total VTI (11.96 ± 5.68) after LAD revascularization. The CSBF per beat (1.67 ± 1.03), CSBF per minute (131.91 ± 86.59) and total VTI (11.00 ± 5.53) before obtuse marginal (OM) grafting showed statistically significant increase to CSBF per beat (1.91 ± 1.03), CSBF per min (155.20 ± 88.70) and total VTI (12.09 ± 5.43) after OM revascularization. In 9 patients, color flow Doppler of LIMA could be demonstrated which showed diastolic predominant blood flow after LIMA to LAD grafting. Conclusion: Demonstration of CSBF was simple and monitoring the trend of CSBF values before and after each graft of LCA territory will guide to determine the adequacy of surgical revascularization.

Effect of dexmedetomidine on diseased coronary vessel diameter and myocardial protection in percutaneous coronary interventional patients.

Introduction: Dexmedetomidine is an alpha-2 agonist used for conscious sedation. It has also been shown to have a myocardial protective effect in off-pump coronary artery bypass patients. The aim of the study was to assess the effect of dexmedetomidine for myocardial protection in percutaneous coronary interventional patients. Methodology: A total of 60 patients (group dexmedetomidine, n = 30 and group normal saline, n = 30) were enrolled in the study. Dexmedetomidine infusion (1 mcg/kg) over 15 min was given as a loading dose after coronary angiography in group dexmedetomidine (D) while normal saline was given in the control group (C) and later maintenance infusion was started at 0.5 mcg/kg/h in both the groups. Coronary vessel diameter was noted before (T0) and after (T1) loading dose of dexmedetomidine/saline in each group. Troponin T (Trop T) values were noted at baseline (T0), 6 h (T2), 12 h (T3) and 24 h (T4) after starting the loading dose. Hemodynamic variables (heart rate [HR] and blood pressure) were monitored at T0, T1, and at regular intervals till 2 h postprocedure. Results: Coronary vessel diameter and HR significantly decreased in group D as compared to control group (P < 0.05) whereas the decrease in Trop T at 6 h, 12 h, and 24 h were not statistically significant between the two groups. Conclusion: Dexmedetomidine decreases the coronary vessel diameter, but maintains the myocardial oxygen demand-supply ratio by decreasing the HR. The decrease in Trop T is statistically insignificant at the doses used.

Comparison between noninvasive measurement of central venous pressure using near infrared spectroscopy with an invasive central venous pressure monitoring in cardiac surgical Intensive Care Unit.

Introduction: Central venous pressure (CVP) measurement is essential in the management of certain clinical situations, including cardiac failure, volume overload and sepsis. CVP measurement requires catheterization of the central vein which is invasive and may lead to complications. The aim of this study was to evaluate the accuracy of measurement of CVP using a new noninvasive method based on near infrared spectroscopy (NIRS) in a group of cardiac surgical Intensive Care Unit (ICU) patients. Methodology: Thirty patients in cardiac surgical ICU were enrolled in the study who had an in situ central venous catheter (CVC). Sixty measurements were recorded in 1 h for each patient. A total of 1800 values were compared between noninvasive CVP (CVPn) obtained from Mespere VENUS 2000 CVP system and invasive CVP (CVPi) obtained from CVC. Results: Strong positive correlation was found between CVPi and CVPn (R = 0.9272, P < 0.0001). Linear regression equation - CVPi = 0.5404 + 0.8875 × CVPn (r2 = 0.86, P < 0.001), Bland-Altman bias plots showed mean difference ± standard deviation and limits of agreement: −0.31 ± 1.36 and − 2.99 to + 2.37 (CVPi-CVPn). Conclusion: Noninvasive assessment of the CVP based on NIRS yields readings consistently close to those measured invasively. CVPn may be a clinically useful substitute for CVPi measurements with an advantage of being simple and continuous. It is a promising tool for early management of acute state wherein knowledge of CVP is helpful.

Evaluation of adjusted central venous blood gases versus arterial blood gases of patients in post-operative paediatric cardiac surgical intensive care unit

Background and Aims: Central venous catheters are in situ in most of the intensive care unit (ICU) patients, which may be an alternative for determining acid-base status and can reduce complications from prolonged arterial cannulation. The aim of this study was to examine the reliability between adjusted central venous blood gas (aVBG) and arterial blood gas (ABG) samples for pH, partial pressure of carbon-di-oxide (pCO2), bicarbonate (HCO3−), base excess (BE) and lactates in paediatric cardiac surgical ICU. Methods: We applied blood gas adjustment rule, that is aVBG pH = venous blood gas (VBG) pH +0.05, aVBG CO2 = VBG pCO2 - 5 mm Hg from the prior studies. In this study, we validated this relationship with simultaneous arterial and central venous blood obtained from 30 patients with four blood sample pairs each in paediatric cardiac surgical ICU patients. Results: There was a strong correlation (R i.e., Pearsons correlation) between ABG and aVBG for pH = 0.9544, pCO2 = 0.8738, lactate = 0.9741, HCO3− = 0.9650 and BE = 0.9778. Intraclass correlation co-efficients (ICCs) for agreement improved after applying the adjustment rule to venous pH (0.7505 to 0.9454) and pCO2 (0.4354 to 0.741). Bland Altman showed bias (and limits of agreement) for pH: 0.008 (−0.04 to + 0.057), pCO2: −3.52 (–9.68 to +2.65), lactate: −0.10 (−0.51 to +0.30), HCO3−: −2.3 (–5.11 to +0.50) and BE: −0.80 (−3.09 to +1.49). Conclusion: ABG and aVBG samples showed strong correlation, acceptable mean differences and improved agreement (high ICC) after adjusting the VBG. Hence, it can be promising to use trend values of VBG instead of ABG in conjunction with a correction factor under stable haemodynamic conditions.

Comparison of left internal mammary artery diameter before and after left stellate ganglion block.

AIMS AND OBJECTIVES Left internal mammary artery (LIMA) is the preferred arterial conduit for coronary artery bypass grafting. Various pharmacological agents are known to increase LIMA blood flow. Sympathetic blockade mediated by stellate ganglion block (SGB) has been used to provide vasodilatation in the upper extremities and in the treatment of refractory angina. We investigated effect of left stellate ganglion block (LSGB) on LIMA diameter. MATERIALS AND METHODS In 30 diagnosed patients of triple vessel coronary artery disease, LSGB was given under fluoroscopic guidance by C6 transverse process approach using 10 ml of 1% lignocaine. LIMA diameter was measured before and 20 min after the block at 2 nd , 3 rd , 4 th and at 5 th rib level. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) were recorded before and 20 min after the block. RESULTS The LIMA diameter increased significantly at 2 nd (2.56 ± 0.39 vs. 2.99 ± 0.40; P < 0.0001), 3 rd (2.46 ± 0.38 vs. 2.90 ± 0.40; P < 0.0001), 4 th (2.39 ± 0.38 vs. 2.84 ± 0.41; P < 0.0001) and 5 th rib level (2.35 ± 0.38 vs. 2.78 ± 0.40; P < 0.0001). No statistically significant change occurred in HR, SBP, DBP and MAP before and 20 min after LSGB. CONCLUSIONS LSGB significantly increased the LIMA diameter. The LSGB can be considered as an alternative to topical and systemic vasodilators for reducing vasospasm of LIMA.

Anaesthetic management of an infant posted for ventricular septal defect closure with right-sided eventration of diaphragm

Eventration of the diaphragm is a rare entity, characterised by abnormal elevation of a dome of diaphragm. In this condition, the diaphragm is composed of fibrous tissue with few or no interspersed muscle fibres. Eventration can be congenital or acquired. Congenital eventration results from inadequate development of muscles or absence of phrenic nerve. The common cause of acquired eventration is injury to the phrenic nerve from traumatic birth injury or surgery for heart disease. The perioperative anaesthetic management of diaphragmatic eventration along with ventricular septal defect with severe pulmonary hypertension makes this case both challenging and unique.

Anesthetic management of a case of Gilbert's syndrome for mitral and aortic valve replacement: Role of transesophageal echocardiography

Gilberts syndrome (GS) is an autosomal inherited disorder characterized by relative deficiency of glucuronyl transferase and poor uptake of unconjugated bilirubin by hepatocytes. Cardiac surgery on cardiopulmonary bypass (CPB) in these patients triggers further hepatic dysfunction. Transesophageal echocardiography (TEE) and Doppler assessment of hepatic vein help in assessing hepatic blood flow (HBF) during cardiac surgery. Here, we discuss anesthetic management and role of TEE in maintaining HBF perioperatively in a 25-year-old male patient with GS undergoing double valve replacement with tricuspid valve plasty. TEE-guided HBF monitoring and management of hepatic perfusion by modifying anesthetic and CPB protocol resulted in the favorable outcome.

Transesophageal Echocardiographic Assessment of Pulmonary Artery-to-Ascending Aorta Ratio for the Detection of Pulmonary Hypertension in Cardiac Surgical Patients

OBJECTIVE The objective of the study was to investigate if the main pulmonary artery (mPA)-to-ascending aorta (AscAo), (mPA:AscAo) ratio could serve as a screening tool in identifying pulmonary artery hypertension (PAH). DESIGN A prospective observational study. SETTING Tertiary care center, university hospital. PARTICIPANTS Fifty-four adult patients undergoing off-pump coronary artery bypass grafting surgery (OPCAB). INTERVENTIONS mPA and AscAo transverse diameters were measured by transesophageal echocardiography (TEE) and the mean pulmonary arterial pressures (mPAP) were recorded simultaneously using a pulmonary artery catheter. MEASUREMENTS AND MAIN RESULTS mPA:AscAo ratio demonstrated significant linear correlation with mPAP measured by pulmonary artery catheterization (ie, r = 0.61, confidence interval [CI] = 0.5352-0.6736, p < 0.0001). Receiver operating characteristic curves were performed to evaluate sensitivity and specificity of mPA:AscAo ratio ≥1 for diagnosing PAH (mPAP ≥25 mmHg). Area under the curve for mPA:AscAo ratio was 0.91 (95% CI, 0.869-0.936, p < 0.0001), with a sensitivity of 84.27%, specificity of 83.92%, positive-predictive value of 87.6% and negative-predictive value of 81.1% for a mPAP ≥25 mmHg. CONCLUSIONS The ratio of mPA:AscAo is a simple, reliable, and reproducible method that can be obtained through TEE, which guides the clinician to screen patients with PAH.