Instruments for hemodynamic monitoring in cardiac anesthesia

The article was written by MSc Ho Thi Xuan Nga - Cardiac Anesthesiologist, Cardiovascular Center - Vinmec Central Park International General Hospital.

Operating room testing conditions do not allow electrocardiogram (ECG) electrodes to be placed precisely above standard recordings. However, reasonable placement of the electrodes provides sufficient capacity to explore the entire left ventricular myocardium and a large portion of the right ventricle.

In left coronary lesions (anterior interventricular and/or exponential branches), leads V5 and lead II together detect 80% of ischemic attacks, but the presence of right-sided lesions reduces sensitivity up to 65%; therefore, a right lead V4 (V4R) is needed to view the myocardium of the ventricle (P).
The combination of DII-V5-V4R allows monitoring of nearly all areas of coronary involvement. The combination DII-V4-V5 has a sensitivity of 96% for left ischemia.
For effective monitoring, at-risk patients, it is necessary for active ischemic risk areas to be displayed on the screen.
The three dominant regions of the coronary arteries have the following distribution scheme:
Anterior interventricular artery (IVA) DI, aVL, V3 - V4 Capillary artery (CX) DI, aVL, V4 - V6 Right coronary artery (CD) ) DII, DIII, aVF Location of ischemia or infarction can be determined according to potential ECG hints where it occurs:
Pre-DI, aVL, V3 - V4 Sub-DII, DIII , aVF Lateral region DI, aVL, V5 - V6 Reciprocal change posterior region V1 - V2 Anterior-lateral region V1 - V6 Anterior-septal region V1 - V4 inferior region - lower side + V5 - V6 Right ventricle V4R - V6R The value of the ST segment is measured 60-80 msec after the J point (the junction between the S wave and the ST segment). Criteria for ischemia:
Horizontal or downward displacement of less than 1.0 mm (> 0.1 mV); The descent is slower than 2 mm (> 0.2 mV); The difference is more than 1 mm (> 0.1 mV).

Several factors interfere with ST segment reading: ventricular hypertrophy (T), left bundle branch block, digital, hypoglycemia, hypothermia, change in heart position, chest opening.
The measurement is more relevant at 80 msec from the J point, but shortened by 60 msec in the case of tachycardia (frequency > 100 beats/min). The amplitude and degree of ST elevation are proportional to the ischemic myocardial volume.
Thus, ischemia of the right ventricle can cause only small changes in the ST segment, even if the damage is extensive and its hemodynamic consequences are significant. The existence of ST changes is a risk indicator for necrosis.
Specificity of ST-segment elevation for myocardial ischemia is very high, but varies with segment geometry: from 95% for ST depression, it increases to 85% for a variable ST-segment depression horizontally and up to 75% for a biphasic ST shift.
The more diffuse the coronary lesions, the higher the sensitivity of ST segment changes; an average of 75% for two-vessel disease and 85% for tri-vessel disease. Several conditions alter the ST segment without signs of ischemia:

In cardiac surgery, arterial catheters are placed aseptically before anesthesia, except in children. The choice of needle insertion site depends on technical ability, type of surgery, intervention for extracorporeal circulation (NCT) and hemodynamic status.
Radial artery: easy to palpate, clean, but curve and pressure values ​​depend on vasoconstriction (muscle surrounding artery); Femoral artery : easy to access but more difficult to maintain in the long term; best reliability of curve and pressure values ​​(elastic artery) and closest to the aorta; can be placed quickly in case of shock; Other arteries: ulnar, brachial, axillary (alternative in case of repeated failure). The complication rate due to arterial perforation in the operating room is about 0.01%. The rate of infection in the intensive care unit > 3 days is about 1% (doubling at the femoral artery site).

In cardiac surgery, the puncture site of the central vein must make it easily manageable perioperatively, allowing the installation of the Swan-Ganz catheter and not interfering with the catheter placement of the LVEF system. . Positions in order of preference:
Right internal jugular vein; Subclavian vein; The left internal jugular vein; The external jugular and basilar veins are just the solution to the problem. The main complications (incidence 3-9% for experienced physicians) are hematoma (arterial perforation), pneumothorax, hemothorax, and air embolism. Punching too deeply can injure the brachial plexus, spinal nerves, stellate ganglia, or thoracic duct (in the left internal jugular vein). In the internal scene, the complication rate is reduced with the use of ultrasound.

The floating pulmonary artery catheter with a balloon at the end was introduced in 1970 and has since become mainstream in the monitoring of critically ill patients. It is estimated that 2 million of these exploratory catheters are placed in patients annually around the world, representing an estimated global cost of $1 to $2 billion.
Although improvements in materials and usage habits by clinicians have reduced its complication rate, the cost/benefit ratio of this invasive technique remains difficult to assess and the Its complication rate is estimated to be 0.1 - 4% of cases. In recent years, several large-scale statistical analyzes have led to the conclusion that Swan-Ganz probably has no benefit at all, or is associated with increased mortality.
Pulmonary artery catheter provides several parameters:
Pulmonary artery pressure (PAP) Pulmonary arterial pressure (PAPO) Pulmonary capillary pressure (Pcap) Systolic volume (SV) Oxygen saturation of mixed venous blood (SvO2) Then it calculates cardiac output (DC), pulmonary arterial resistance (RAP), systemic arterial resistance (RAS), right and left ventricular systolic work (RVSW, LVSW ), right ventricular ejection fraction, ventricular end-diastolic volume (P).

4.1 Indication of pulmonary artery catheter Pathology of the pulmonary circulation
Pulmonary arterial hypertension (PAP > 50 mmhg) Right ventricular failure Serious lung disease: COPD, asthma Impaired pulmonary capillary permeability (ARDS, SIRS) toxic shock. Pulmonary overload
Left ventricular failure (left ventricular stagnation): impaired contractile function EF < 0.35, mitral valve disease Hypovolemia (end-stage renal failure, fluid overload, etc.) cardiac output and venous oxygen saturation SvO2
Activities leading to arterial hemodynamic changes in high-risk patients (aortic surgery, pulsating heart surgery) Measurement of cardiac output in situations has very unstable systemic vascular resistance Septic shock, vasomotor paralysis, ventricular support, burns, multiple trauma

4.2 Complications of the pulmonary artery catheter Complications related to the insertion of the lead: wrong puncture of the artery, hematoma, pneumothorax. Complications related to right heart chamber passage:
Multifocal ventricular extrasystoles; Bundle conduction block (P) (risk of complete block in case of previous left bundle branch block); Valve damage (balloon deflated), catheter coil. 4.3 Catheter-related complications in the distal pulmonary artery Pulmonary infarction : inadvertently inflated balloon at distal location; Pulmonary artery rupture: balloon swelling while the PAC is in the occluded position. Arterial rupture is the most serious complication (a mortality rate close to 50%) and is represented by catastrophic bronchial hemorrhage. The cause is lack of control when pumping the balloon: always make sure to have the AP curve before inflating the balloon. Infectious complications: incidence 2-5%; skin infection, thrombosis, endocarditis. Rate of serious complications: <1%.
Contraindications- Contraindications The first contraindication is incorrect! For the rest, there are several situations in which Swan-Ganz catheterization is more aggravating:
Severe ventricular arrhythmias : risk of a malignancy attack; Bundle block (T): risk of bundle branch block (P), causing complete block; Anticoagulation or coagulopathy: risk of bleeding at needle puncture site Anastomosis (P)-(T) (atrial septal defect): risk of entering the left chamber of the heart; Permanent pacemaker leads inserted less than 6 weeks ago: risk of lead displacement.

Cardiac output is measured by thermal dilution using the Stewart-Hamilton equation. Measurement is reliable if pulmonary flow and blood volume are constant during measurements (minimum of 3 measurements), if readings (0.9% NaCl or 5% glucose at 4-6°C) do not through any loss or circulation, there is no tricuspid regurgitation (underestimation of cardiac output) nor intracardiac shunts (overestimation of cardiac output).
Oxygen transport and DO2 / VO2 ratio
To ensure cellular oxygenation, oxygen transport (DO2) and oxygen consumption (VO2) must be in harmony. Metabolic demand is a major determinant of cardiac output, which is heterogeneously distributed to organs according to their specific functions and needs. Measures taken clinically usually only assess overall oxygen consumption.
All systems that infer cardiac output from the area under the arterial curve are sensitive to systemic vascular resistance and vascular elasticity. They must be rechecked each time they change. In the case of extreme changes in systemic vascular resistance (vasoparalysis, strong vasoconstriction) only the pulmonary catheter gives a reliable value.

Vinmec International General Hospital is one of the hospitals that not only ensures professional quality with a team of leading medical professionals, modern equipment and technology, but also stands out for its examination and consultation services. comprehensive and professional medical consultation and treatment; civilized, polite, safe and sterile medical examination and treatment space. Customers when choosing to perform tests here can be completely assured of the accuracy of test results.
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