Utility of transesophageal echocardiography and pulmonary artery catheterization during laparoscopic assisted abdominal aortic aneurysm repair

Background: Advanced laparoscopic procedures are more commonly performed in elderly patients with cardiac disease. There has been limited data on the use of pulmonary artery catheters (PAC) and transesophageal echocardiography (TEE) to monitor hemodynamic changes. Methods: We prospectively studied eight patients undergoing laparoscopic assisted abdominal aortic aneurysm repair. All patients had a PAC and all but one had an intraoperative TEE. Data included heart rate (HR), temperature (temp), pulmonary artery systolic (PAS) and diastolic (PAD) pressures, mean arterial pressure (MAP), central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), cardiac index (CI), mixed venous oxygen saturation (MVO₂), and oxygen extraction ratio (O₂Ex) and was obtained prior to induction, during insufflation, after desufflation, during aortic cross-clamp, and at the end of the procedure. End diastolic area (EDA), a reflection of volume status, was measured on TEE. ANOVA was used for data analysis. Results: No changes were noted in HR, temp, PAS, PCWP, CI, MVO₂, and O₂Ex. PAD and CVP were greater during insufflation compared with baseline and aortic cross-clamp without associated changes in EDA. MAP was higher at baseline compared with all other times during the procedure. Conclusions: Insufflation increased PAD and CVP. However, volume status as suggested by EDA and PCWP did not change. These data question the reliability of hemodynamic measurements obtained from the PAC during pneumoperitoneum and suggest that TEE may be sufficient for evaluation of volume status along with the added benefit of timely detection of ventricular wall motion abnormalities. Received: 27 March 1997/Accepted: 5 July 1997     

Hemodynamic changes due to Trendelenburg positioning and pneumoperitoneum during laparoscopic hysterectomy

More prolonged gynecological laparoscopic operations are being performed in recent years, and a steeper head-down position is required. The early reports of hemodynamic changes during gynecologic laparoscopy are conflicting, and the effects of anesthesia, head-down tilt and pneumoperitoneum have not been clearly separated. Invasive hemodynamic monitoring was carried out in 20 female ASA Class I-II patients who underwent laparoscopic hysterectomy. Baseline measurements were made in the supine, supine-lithotomy and Trendelenburg (25 30 degrees) positions in awake patients. Measurements were repeated in the supine-lithotomy and Trendelenburg positions after induction of anesthesia, during laparoscopy 5 minutes after the beginning of peritoneal CO₂-insufflation (intra-abdominal pressure 13–16 mmHg) and at 15-minute intervals thereafter, after laparoscopy in the Trendelenburg and supine positions, after extubation and in the recovery room at 30-minute intervals. Patients received balanced general anesthesia with isoflurane in 35% O₂ in an oxygen/air mixture. End tidal PGO₂ was maintained between 4.5–4.8 kPa (33—36 mmHg) by changing the minute volume of controlled ventilation. The Trendelenburg position in awake and anesthetized patients increased pulmonary arterial pressures (PAP), central venous pressure (GVP) and pulmonary capillary wedge pressure (PCWP). These pressures increased further at the start of CO₂-insufflation, decreased towards the end of the laparoscopy and reached pre-insufflation levels after deflation of pneumoperitoneum. The mean arterial pressure (MAP) increased at the beginning of laparoscopy in comparison with the pre-laparoscopic values. Heart rate (HR) was quite stable during laparoscopy. The cardiac index (CI) decreased with anesthesia from 3.8 to 3.2 1 · min^-1 · m^-2 and further during laparoscopy to 2.7 1 · min^-1 · m^-2, returning to pre-insufflation values soon after deflation. The stroke index (SI) changed in concert with the GI changes. The right ventricular stroke work index decreased during laparoscopy more than the left ventricular stroke work index. The right atrial pressure (GVP) exceeded the PCWP more often during laparoscopy than during any other phase of the procedure. Anesthesia and the Trendelenburg position increased the CVP, PCWP and pulmonary arterial pressures and decreased cardiac output. Pneumoperitoneum increased these pressures further mostly in the beginning of the laparoscopy, and cardiac output decreased towards the end of the laparoscopy. The risk of systemic CO₂-embolus was increased during laparoscopy.     

Vectorcardiographic changes during laparoscopic cholecystectomy may mimic signs of myocardial ischaemia

Background: Laparoscopic surgery involves the use of intra-ab-dominal carbon dioxide insufflation (pneumoperitoneum). The increased intra-abdominal pressure causes marked haemodyn-amic changes, which may influence electrocardiographic monitoring. The aim of the present study was to elucidate the influence of pneumoperitoneum on vectorcardiographic recordings.
Methods: Vectorcardiographic changes (QRS vector difference= QRSVD, QRS loop area, QRS magnitude, ST vector magnitude, spatial ST vector change) were recorded continuously applying computerized vectorcardiography in 12 anaesthetised cardio-vascularly healthy patients, scheduled for laparoscopic cholecystectomy.
Measurements were made before and during pneumoperitoneum in three different body positions (supine, Trendelenburg and reversed Trendelenburg), also employing transesophageal echo-cardiography and invasive blood pressure monitoring. Results: Pneumoperitoneum significantly increased QRSVD, in parallel with an enlargement in loop area and magnitude. The magnitude was significantly increased in the transversal and frontal planes and there was a tendency to increase the magnitude in the sagittal plane. The increase in QRS-VD reached levels previously associated with the development of myocardial ischaemia in patients with coronary artery disease. The ST-variables were not changed by the pneumoperitoneum. The positional changes also influenced QRSVD significantly.
Conclusions: When computerized vectorcardiography is used for ischaemia monitoring during pneumoperitoneum, the ST-variables seem reliable. However, vectorcardiographic QRS changes should be interpreted with caution, as the QRS alterations found during pneumoperitoneum mimic the changes seen during myocardial ischaemia.     

The use of transesophageal echocardiography for preload assessment in critically ill patients

IV volume is often administered to patients in an intensive care unit (ICU) to improve cardiovascular function. We investigated the relationship between stroke volume (SV) and left ventricular (LV) size by using transesophageal echocardiography (TEE) in a population of 20 ICU patients and 21 postoperative cardiac surgical patients. We also examined whether LV end diastolic area (EDA), by TEE, could identify patients who increased SV by 20% or more (responders) after 500 mL of pentastarch administration. There was only a modest relationship (r = 0.60) between the EDA and the SV in all patients. No relationship could be found between the pulmonary capillary wedge pressure (PCWP) and the EDA in all patients. Both responder and nonresponder PCWP increased significantly after volume administration. Only responder EDA increased significantly after volume administration. Responders had significantly lower EDA (15.3 +/- 5.4 cm(2)) and PCWP (12.2 +/- 2.2 mm Hg) when compared with nonresponders (20.2 +/- 4.8 cm(2)) and 15.9 +/- 3.1 mm Hg, respectively). Few ICU patients and only those with a small EDA responded to volume administration. It was not possible to identify an overall optimal LV EDA below which most patients demonstrate volume-recruitable increases in SV. IMPLICATIONS: In a ventilated intensive care unit and cardiac surgical population, transesophageal echocardiography and pulmonary artery catheter are sensitive in detecting changes in preload after volume administration. Few patients demonstrate volume-recruitable increases in stroke volume when compared to cardiac surgical patients. It is not possible to establish an overall end diastolic threshold below which a large proportion of ventilated patients respond to volume administration.     

Estimation of cardiac preload changes by systolic pressure variation in pigs undergoing pneumoperitoneum

BACKGROUND: Variations in systolic pressure arterial waveform (SPV) and its component have been shown to be a reasonable indicator of left ventricular preload. Creation of a pneumoperitoneum (PMOP) by insufflation of CO2 increases intrathoracic pressure, leading to overestimation of preload as assessed by pressure methods. The purpose of this study was to compare SPV with other standard methods in anaesthetized pigs. METHODS: We measured SPV and its DeltaDown component (deltaDown), pulmonary artery occlusion pressure (PAOP) and left ventricular short-axis cross-sectional area using transthoracic echocardiography (TTE) in 7 pigs, at baseline, after 12 mmHg PMOP and after an intravascular load with 10 ml/kg hydroxylethylstarch (HES). RESULTS: PMOP increased SPV from 12.9+/-4.9 to 16.9+/-5.5 mmHg (P<0.05) and decreased pulmonary compliance, with no change in PAOP or end-diastolic area assesssed by TTE. Intravascular volume loading significantly decreased SPV from 16.9+/-5.5 to 11.2+/-4.9 mmHg and deltaDown from 9.9+/-7.1 to 5.2+/-4.5 (P<0.05), and increased PAOP and end-diastolic area. Significant correlation between changes in deltaDown and EDA was noted following HES (r=0.78, P<0.05). CONCLUSION: In anaesthetized pigs, the creation of a PMOP alters SPV, likely by decreasing lung compliance. Once PMOP is established, changes in cardiac preload could be estimated by SPV analysis.     

Echocardiographic and Hemodynamic Evaluation of Cardiovascular Performance during Laparoscopy of Morbidly Obese Patients

Background: The effects of morbid obesity, pneumoperitoneum (PP) and body position on cardiac function during laparoscopy were studied. Methods: Transesophageal echocardiography (TEE) was performed on 10 obese patients (body mass index, BMI, 48.1±1.8 kg/m²) and 10 normal weight patients (BMI = 22.6±0.8 kg/m²) in supine, Trendelenburg and reverse Trendelenburg positions before and after PP. Left ventricular end-systolic wall stress (LVESWS) was calculated from invasive blood pressure (BP) values and LV dimensions obtained by TEE. Diastolic filling was assessed by mitral valve and pulmonary vein flow velocities. Results: LVESWS was higher in obese patients both at baseline (46.0±4.0x10³ dyn/cm²) and with PP (69.3±8.2x10³ dyn/cm²), than normal weight subjects (31.9±3.7x10³ dyn/cm² and 45.7±5.9x10³ dyn/cm²; P <0.05 obese vs normal weight patients at baseline). Systolic BP was not different between groups at baseline (normal weight 111±4 mmHg, obese 119±3 mmHg), but increased significantly with PP only in obese patients (normal weight 129±6 mmHg, obese 157±8 mmHg; P <0.05). Postural changes during PP had no impact on cardiac function in either obese or normal weight subjects. Conclusions: Anesthetized obese patients undergoing laparoscopy have higher LVESWS before pneumoperitoneum (due to increased end-systolic left ventricular dimensions) and during pneumoperitoneum (due to more pronounced increases in blood pressure). Since LVESWS is a determinant of myocardial oxygen demand, more aggressive control of blood pressure (ventricular afterload) in MO patients may be warranted to optimize the myocardial oxygen requirements.     

TRANSOESOPHAGEAL ECHOCARDIOGRAPHIC ASSESSMENT OF HAEMODYNAMIC FUNCTION DURING LAPAROSCOPIC CHOLECYSTECTOMY

We have measured cardiovascular changes associated with insufflationof carbon dioxide and the reverse Trendelenburg position duringlaparoscopic cholecystectomy, using trans-oesophageal echocardiographyin 13 healthy patients. End-tidal carbon dioxide values increasedafter insufflation of carbon dioxide, with values significantly(? < 0.05) increased after lateral tilt positioning. Creationof a pneumoperitoneum was associated with increases (? <0.05) in left ventricular end-systolic wall stress, concomitantwith increases (P < 0.01) in peak airway pressure and systemicarterial pressure. In addition, left ventricular end-diasto/icarea decreased (? < 0.05) after reverse Trendelenburg positioning.Left ventricular ejection fraction was maintained throughoutthe study. (Br. J. Anaesth. 1993; 70: 621–625)      

Trendelenburg positioning after cardiac surgery: effects on intrathoracic blood volume index and cardiac performance

BACKGROUND AND OBJECTIVE: The efficacy of the Trendelenburg position, a common first step to treat suspected hypovolaemia, remains controversial. We evaluated its haemodynamic effects on cardiac preload and performance in patients after cardiac surgery. METHODS: Twelve patients undergoing mechanical ventilation of the lungs who demonstrated left ventricular 'kissing papillary muscles' by transoesophageal echocardiography, thus suggesting hypovolaemia, were positioned 30 degrees head down for 15 min immediately after cardiac surgery. Cardiac output by thermodilution, central venous pressure, pulmonary artery occlusion pressure, left ventricular end-diastolic area by transoesophageal echocardiography and intrathoracic blood volume by thermo- and dye dilution were determined before, during and after this Trendelenburg manoeuvre. RESULTS: Trendelenburg's manoeuvre was associated with increases in central venous pressure (9 +/- 2 to 12 +/- 3 mmHg) and pulmonary artery occlusion pressure (8 +/- 2 to 11 +/- 3 mmHg). The intrathoracic blood volume index increased slightly (dye dilution from 836 +/- 129 to 872 +/- 112 mL m(-2); thermodilution from 823 +/- 129 to 850 +/- 131 mL m(-2)) as did the left ventricular end-diastolic area index (7.5 +/- 2.1 to 8.1 +/- 1.7 cm2 m(-2)), whereas mean arterial pressure and the cardiac index did not change significantly. After supine repositioning, the cardiac index decreased significantly below baseline (3.0 +/- 0.6 versus 3.5 +/- 0.8 L min(-1) m(-2)) as did mean arterial pressure (76 +/- 12 versus 85 +/- 11 mmHg), central venous pressure (8 +/- 2 mmHg) and pulmonary artery occlusion pressure (6 +/- 4 mmHg). The intrathoracic blood volume index and left ventricular end-diastolic area index did not differ significantly from baseline. CONCLUSIONS: Trendelenburg's manoeuvre caused only a slight increase of preload volume, despite marked increases in cardiac-filling pressures, without significantly improving cardiac performance.     

One versus two MAC halothane anesthesia does not alter the left ventricular diastolic pressure-volume relationship

Previous studies on halothane's effect on left ventricular diastolic compliance (LVDC) not only have had conflicting results, but are not directly applicable to most intraoperative settings. Therefore, the authors examined in dogs whether the depth of halothane anesthesia alters LVDC under surgical conditions over a wide range of hemodynamic stresses with the cardiovascular reflexes intact. The left ventricular diastolic pressure-volume relation was examined at 1 MAC and 2 MAC halothane in seven dogs over wide ranges of preload and afterload during left thoracotomy. Pulmonary capillary wedge pressure (PCWP), left ventricular end-diastolic pressure (LVEDP), and echocardiographic left ventricular end-diastolic volume (LVEDV) were analyzed with the exponential pressure-volume relation P = AeBV (where P = pressure, V = volume, and A and B are empirically derived coefficients). Multivariate analysis showed no significant differences for diastolic pressure-volume relations, comparing both levels of halothane using either PCWP or LVEDP for pressure. The authors conclude that in the intact cardiovascular system in the healthy open-chest dog: 1) LVDC does not change with the depth of halothane between 1 and 2 MAC (it is still possible LVDC changed between 0 and 1 MAC), and 2) PCWP does reflect the LVEDV during halothane anesthesia (between 1 and 2 MAC) under surgical conditions over a wide range of cardiovascular stresses.     

Validation of esophageal Doppler for noninvasive hemodynamic monitoring under pneumoperitoneum

Background Commonly used perioperative measurements of hemodynamics, such as Swan-Ganz catheter assessment, are invasive and may not be reliable under pneumoperitoneum. The purpose of this study was to validate the use of esophageal Doppler for noninvasive hemodynamic monitoring under pneumoperitoneum in an experimental pig model. Methods Eight female pigs were submitted to two 30-min study periods, one each for the baseline (no interventions) and pneumoperitoneum (12-mmHg carbon dioxide pneumoperitoneum) conditions. One pig was excluded because of tachycardia (>140 at baseline). A Swan-Ganz pulmonary artery catheter was used to measure cardiac output (CO-SG) and pulmonary capillary wedge pressure (PCWP). An esophageal Doppler probe was inserted to record cardiac output (CO-ED) and corrected flow time (FTc), an index of preload. Transthoracic echocardiography was used to measure left ventricular end-diastolic diameter (LVEDD) and cardiac output (CO-TTE). Pearson correlation was used to assess individual associations between the measured hemodynamic parameters. Results There was good correlation between CO-ED and CO-SG (r = 0.577; p < 0.001) and excellent correlation between CO-ED and CO-TTE (r = 0.815; p < 0.001). There was no correlation between FTc and LVEDD or PCWP. These relationships were consistent when analyzed separately at baseline and during pneumoperitoneum. Conclusion Esophageal Doppler monitoring is a valid noninvasive method of estimating cardiac output at baseline and during pneumoperitoneum in a porcine model. Corrected flow time did not correlate with other estimates of preload at baseline or during pneumoperitoneum. Presented at the annual meeting of the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), Dallas, TX, USA, April 2006     

Echocardiographic Doppler Assessment of Pulmonary Capillary Wedge Pressure in Surgical Patients with Postoperative Circulatory Shock and Acute Lung Injury

Background: In cardiac patients, pulmonary capillary wedge pressure (PCWP) is estimated using color M-mode Doppler study of left ventricular filling and Doppler tissue imaging. The goal of this study was to assess whether echocardiography accurately estimates PCWP in critically ill patients.

Methods: Sixty ventilated patients admitted for septic shock and acute lung injury were prospectively studied using simultaneously transesophageal echocardiography and pulmonary artery catheterization. Initial PCWP values and their changes measured invasively were compared to initial values and corresponding changes of early diastolic velocity of mitral annulus displacement measured by Doppler tissue imaging (Ea), flow propagation velocity of early diastolic mitral inflow measured by color M-mode Doppler (Vp), and their respective ratio to early mitral inflow velocity (E) measured by conventional Doppler: E/Ea and E/Vp. Relations between E/Ea, E/Vp, and PCWP were prospectively tested in 20 additional patients.

Results: E/Ea and E/Vp gave a rough estimate of initial PCWP values with mean biases of 0.4 +/- 2.2 and 0.1 +/- 2.9 mmHg, respectively. Receiving operating characteristic curves demonstrated that an E/Ea of 6 or greater is an accurate predictor of a PCWP of 13 mmHg or greater and that an E/Ea of 5.4 is a good predictor of a PCWP of 8 mmHg or less. Changes in PCWP were significantly correlated to changes in E/Ea (Rho = 0.84, P < 0.0001).     

Echocardiographic Doppler assessment of pulmonary capillary wedge pressure in surgical patients with postoperative circulatory shock and acute lung injury

BACKGROUND: In cardiac patients, pulmonary capillary wedge pressure (PCWP) is estimated using color M-mode Doppler study of left ventricular filling and Doppler tissue imaging. The goal of this study was to assess whether echocardiography accurately estimates PCWP in critically ill patients. METHODS: Sixty ventilated patients admitted for septic shock and acute lung injury were prospectively studied using simultaneously transesophageal echocardiography and pulmonary artery catheterization. Initial PCWP values and their changes measured invasively were compared to initial values and corresponding changes of early diastolic velocity of mitral annulus displacement measured by Doppler tissue imaging (Ea), flow propagation velocity of early diastolic mitral inflow measured by color M-mode Doppler (Vp), and their respective ratio to early mitral inflow velocity (E) measured by conventional Doppler: E/Ea and E/Vp. Relations between E/Ea, E/Vp, and PCWP were prospectively tested in 20 additional patients. RESULTS: E/Ea and E/Vp gave a rough estimate of initial PCWP values with mean biases of 0.4 +/- 2.2 and 0.1 +/- 2.9 mmHg, respectively. Receiving operating characteristic curves demonstrated that an E/Ea of 6 or greater is an accurate predictor of a PCWP of 13 mmHg or greater and that an E/Ea of 5.4 is a good predictor of a PCWP of 8 mmHg or less. Changes in PCWP were significantly correlated to changes in E/Ea (Rho = 0.84, P < 0.0001). CONCLUSIONS: In patients with postoperative circulatory shock and acute lung injury, transesophageal echocardiography estimates noninvasively PCWP. However, echocardiographic estimation of PCWP may not be accurate enough for adjusting therapy.     

Hemodynamic and pulmonary changes during open, carbon dioxide pneumoperitoneum, and abdominal wall-lifting cholecystectomy

Background: Carbon dioxide (CO2) pneumoperitoneum effects are still controversial. The aim of this study was to investigate cardiopulmonary changes in patients subjected to different surgical procedures for cholecystectomy. Methods: In this study, 15 patients were assigned randomly to three groups according to the surgical procedure to be used: open cholecystectomy (OC), CO2 pneumoperitoneum cholecystectomy (PP), and laparoscopic gasless cholecystectomy (abdominal wall lifting [AWL]), respectively. A pulmonary artery catheter was used for hemodynamic monitoring in all patients. A subcutaneous multiplanar device (Laparo Tenser) was used for abdominal wall lifting. To avoid misinterpretation of results, conventional anesthesia was performed with all parameters, and the position of the patients held fixed thoroughout surgery. The following parameters were analyzed: mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), cardiac index (CI), stroke volume index (SVI), central venous pressure (CVP), systemic vascular resistances index (SVRI), mean pulmonary arterial pressure (MPAP), pulmonary capillary wedge pressure (PCWP), pulmonary vascular resistances index (PVRI), peak inspiratory pressure (PIP), end-tidal CO2 pressure (ETCO)2, CO2 arterial pressure (PaCO2), and arterial pH. Results: All the operations were completed successfully. The Laparo Tenser allowed good exposition of the surgical field. A slight impairment of the cardiopulmonary functions, with reduction of SVRI, MAP, and CI and elevation of pulmonary pressures and vascular resistance, followed induction of anesthesia. However, these effects tended to normalize in the OC and AWL groups over time. In contrast, CO2 insufflation produced a complex hemodynamic and pulmonary syndrome resulting in increased right- and left side filling pressures, significant cardiac index reduction, derangement of the respiratory mechanics, and respiratory acidosis. All of these effects normalized after desufflation. Conclusions: Cardiopulmonary adverse effects of general anesthesia were significant but transitory and normalized during surgery. Carbon dioxide pneumoperitoneum caused a significant impairment in cardiopulmonary functions. In high-risk patients, gasless laparoscopy may be preferred for reliability and absence of cardiopulmonary alterations. apd: 21 December 2000     

The effects of elevated intraabdominal pressure, hypercarbia, and positioning on the hemodynamic responses to laparoscopic colectomy in pigs

Background: This study investigated three factors postulated to be sources of physiological stress in laparoscopic surgery: hypercarbia, elevated intraabdominal pressure, and the steep Trendelenburg position. Our research was designed to define the effects of each of these potential stressors on hemodynamic responses observed during laparoscopic colectomy in pigs. Methods: Twenty-four pigs were randomized into the following four groups, based on the method for obtaining surgical exposure while a colectomy or laparoscopic-assisted colectomy was performed: Open surgery (n = 6), CO₂ pneumoperitoneum (n = 6), Helium pneumoperitoneum (n = 6), and abdominal wall Lifter (n = 6). The animals were paralyzed with minute ventilation adjusted. All animals underwent extensive pulmonary and hemodynamic monitoring with measurements of the following parameters: RR, Vt, minute ventilation, O₂, sat, ETCO₂, PVR, HR, MAP, CO, PAP, CVP, PCWP, SV, LVSWI, DO₂, and VO₂. The laparoscopic pigs were placed in the steep Trendelenburg position during surgery. Results: The effect of a CO pneumoperitoneum was to increase PaCO₂ PVR and cause an acidemia that could not be prevented by an increase in minute ventilation. Elevated intraabdominal pressure decreased UO. Both pneumoperitoneum groups had a fourfold increase in IVCP, a measure of intraabdominal pressure. Some of this increase was due to placement into the Trendelenburg position; IVCP increased to a lesser degree in the Lifter group. The steep Trendelenburg position caused significant increases in PAP, CVP, and PCWP; however, a contributory effect of elevated intraabdominal pressure cannot be ruled out. None of these procedures had any significant effect on the HR or MAP. There was a significant increase in CO in the CO₂ and Lifter groups; however, when CO was controlled for HR effects, there was no significant effect on SV from any of these different procedures. LVSWI, DO₂, and VO₂ were not affected by any of the different exposure methods. Conclusions: The effects of laparoscopic surgery and open surgery on hemodynamic responses are minimal, and no one method is superior to another when performed in pigs that are healthy, hydrated, and hyperventilated to keep ETCO₂ <40. However, since elderly and sick patients have a lower threshold for physiologic decompensation, we can infer that the small hemodynamic changes noted in this study might become significant factors when surgery is performed on compromised patients. The finding that an abdominal wall lifting device causes the fewest metabolic and hemodynamic effects makes its use an important consideration when performing laparoscopic surgery in patients with cardiopulmonary compromise, hemodynamic instability, or any preexisting renal insufficiency.     

Haemodynamic assessment of hypovolaemia under general anaesthesia in pigs submitted to graded haemorrhage and retransfusion

We have compared the value of different variables used in the assessment of blood loss during progressive hypovolaemia and resuscitation under general anaesthesia in anaesthetized pigs. We measured mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), the negative component of the systolic arterial pressure variation (delta Down) and left ventricular end-diastolic area (LVEDa) using echocardiography. Blood was progressively withdrawn (up to 35 ml kg-1 in seven steps) and then reinfused after the same pattern. Regression coefficient (r) and normalized slope (nS) of the regression relationship between each variable and amount of blood loss were determined. The difference between the withdrawal and reinfusion curves was assessed by the area between the curves. We also estimated the minimal loss of blood volume which induced significant changes in each variable compared with that under control conditions during withdrawal of blood (minWBV) and maximal loss in blood volume which induced no significant changes in a variable compared with control conditions during retransfusion (maxRBV). During haemorrhage, MAP decreased (from mean 74 (SD 9) to 31 (5) mm Hg; P < 0.001), delta Down increased (from 1.2 (1.4) to 11.4 (4.2) mm Hg; P < 0.001), PCWP decreased (from 6.2 (2.1) to 0.3 (1.0) mm Hg; P < 0.001) and LVEDa decreased (from 13.8 (2.0) to 5.1 (2.0) cm2; P < 0.01). The highest r values were obtained with MAP and LVEDa, and the highest nS value with delta Down. The least difference between withdrawal and reinfusion was with LVEDa, the lowest values of minWBV were with PCWP and LVEDa, and the highest value of maxRBV was obtained with PCWP. During progressive haemorrhage under general anaesthesia, LVEDa was an accurate variable for assessment of blood volume loss, delta Down contributed no further information compared with MAP, and PCWP was the most reliable variable for assessing return to baseline blood volume.      

Trendelenburg versus PASG application--hemodynamic response in man

Diminished venous return is the primary determinant of reduced cardiac output in hemorrhagic hypoperfusion. In this study the hemodynamic response of two therapies commonly employed to increase venous return in hemorrhagic hypoperfusion--pneumatic antishock garment (PASG) application and Trendelenburg (TREND) positioning--were compared in normovolemic man. Five patients had PASG pressure of 20 mm Hg compared with 10 degrees Trendelenburg, eight patients had 20 and 40 mm Hg PASG application compared with 10 degrees Trendelenburg. PASG application at both 20 and 40 mm Hg resulted in a significant increase in CVP (11.1 +/- 1.9 baseline to 16.0 +/- 2.7 PASG 40; p less than 0.01) left atrial pressure (LAP) (10.1 +/- 1.3 baseline to 14.4 +/- 1.8 PASG 20; p less than 0.01) pulmonary capillary wedge pressure (PCWP) (11.6 +/- 2.0 baseline to 16.8 +/- 3.4 PASG 40; p less than 0.01) and esophageal pressure (Pes) (5.0 +/- 0.8 baseline to 8.6 +/- 0.9 PASG 40; p less than 0.01). However, transmural right and left atrial pressure (RATP, LATP) and cardiac index (CI) were unchanged. Ten degrees of Trendelenburg resulted in no increase in CVP, PCWP, RATP, or LATP, but CI (2.67 +/- 0.07 baseline to 2.82 +/- 0.1 TREND; p less than 0.01) was significantly increased. Systemic vascular resistance index (570 +/- 46 TREND vs. 668 +/- 53 PASG 40; p less than 0.01) was significantly less in Trendelenburg compared to PASG at 40 mm Hg. The data demonstrate that elevation in CVP, LAP, and PCWP following PASG application is secondary to an increase in intrathoracic pressure (as measured by Pes).(ABSTRACT TRUNCATED AT 250 WORDS)     

Usefulness and limitations of transesophageal echocardiography in anesthetic practice

Transesophageal echocardiography (TEE) has been used as a monitor of cardiovascular function and as a diagnostic tool in anesthetic practice. TEE is the only available monitor to detect anatomical abnormalities such as of wall motion as well as valvular abnormalities. Doppler TEE has wider diagnostic functions. TEE is a very sensitive monitor to detect myocardial ischemia by recognizing wall motion abnormalities and loss of systolic wall thickening. Preload defined by left ventricular end-diastolic volume may not correlate with left ventricular end-diastolic pressure or pulmonary capillary wedge pressure (PCWP) when left ventricular compliance changes such as after coronary artery surgery. PCWP can be misleading when transmural pressure across cardiac chambers are undetermined such as in patients with cardiac tamponade or those on high positive end-expiratory pressure. In these situations, TEE is a powerful tool to link physiologic parameters and anatomy. TEE is also a very sensitive monitor to diagnose air embolism during cardiac surgery and neurosurgery in sitting position. There are, however, several shortcomings such as its cost, "too much sensitivity", requirement of some experience, interobserver variability, and so on. The computer-assisted on-line analysis would greatly augment usefulness of TEE. When these shortcomings are overcome, TEE would be one of the most important monitors in anesthetic practice.     

Dose-related cardiovascular effects of amrinone during enflurane anesthesia in the dog

The dose-related cardiovascular effects of amrinone, a synthetic cardiotonic and vasodilating drug, were investigated in dogs anesthetized with enflurane (2.2-2.4% end-tidal concentration). Twelve mongrel dogs were divided into two groups of six animals: an enflurane group (E) that received only enflurane, and an amrinone group (A). In the latter group each dog received the following sequential boluses and 30-min infusions: 1) the amrinone solvent alone; 2) amrinone, 1 mg/kg + 5 micrograms X kg-1 X min-1; 3) amrinone, 2 mg/kg + 10 micrograms X kg-1 X min-1; 4) amrinone, 4 mg/kg + 20 micrograms X kg-1 X min-1. Over the course of the experiment, 2.2-2.4% end-tidal enflurane alone resulted in a gradual decrease in cardiac index (CI), stroke volume index (SVI), and the maximum left ventricular dP/dt (LV dP/dtmax), without changes in heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), or pulmonary capillary wedge pressure (PCWP) in group E. Significant differences from group E after 30 min of the lowest dose of amrinone included higher CI and SVI with lower systemic vascular resistance (SVR). The medium dose of amrinone, in addition to the effects already observed with the lowest dose of amrinone, decreased MAP and pulmonary vascular resistance (PVR), and increased LV dP/dtmax, when compared to group E only. Furthermore, the highest dose of amrinone caused lower pulmonary artery mean pressure (PAM), PCWP, and higher HR with shortened PR interval. The differences in MAP, CI, LV dP/dtmax, PCWP, PAM, PR interval, SVR, and PVR compared to E were still significant 30 min after the cessation of the highest dose. This study shows that the myocardial depressant effects of enflurane in an unstimulated canine model with a previously healthy heart can be overcome in a dose-related manner by amrinone. In contrast to other vasodilators, no reflex increase in plasma catecholamines was seen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Haemodynamic changes induced by two I:E ratios: a transoesophageal echocardiographic study

Purpose

To assess the effects of controlled ventilation with two I:E ratios on haemodynamic and left ventncular function m mechanically ventilated patients with moderate to severe respiratory disease, using fluctuation of the artenal pressure waveform and the changes in left ventncular areas obtained by transoesophageal echocardiography.

Methods

Nine patients had their lungs ventilated using volume controlled ventilation with two I:E ratios (1:3 and 1:1). Respiratory rate was adjusted so that six cardiac beats occurred during a respiratory cycle. Systolic Wood pressure vanation (SBPV). left ventricular area variations measured by TEE and haemodynamic variables measured by PA catheter were compared.

Results

When compared with I:E (1:3). I:E (1:1) decreased end diastolic area (EDA) throughout the respiratory cycle from 3% to 8% (P< 0.01) and increased SBPV from 6 ± I to 11 ± I mmHg (P< 0.01). In four patients. SBPV was > 12 mmHg with I:E 1: I. Conversely, SBPV was < 10 mmHg in all patients with I:E 1:3. With I:E (1: 1). EDA decreased up to 7% dunng expiration (P< 0.01). The ejection fraction area remained stable for both ventilatory patterns and throughout the ventilatory cycle for a given I:E. The usual invasive haemodynamic vanables were unchanged throughout the study, as was PaO₂/FIO₂.

Conclusion

In this setting. EDA and SBPV allow beat-to-beat evaluation of left ventncular preload during change of I:E ratio. Switch from I:E 1:3 to 1:1 may be used as a rapid, safe and reversible test to estimate intravascular volume status assessed by changes in SBPV or EDA.     

Dipyridamole-thallium myocardial scanning in the pre-operative assessment of patients undergoing abdominal aortic aneurysmectomy

Dipyridamole thallium scanning (DTS) is an imaging technique with good sensitivity for coronary artery disease (CAD). The purpose of this study was to compare the haemodynamic courses and the correlation between pulmonary capillary wedge pressure (PCWP) and central venous pressure (CVP) in patients with normal DTS (Group 1: n = 12) with those whose scans demonstrated CAD (Group2: n = 11). Haemodynamic profiles were obtained prior to anaesthesia and at several times during surgery. The haemodynamic courses in both groups were similar with significant decreases in cardiac index, stroke index, and left ventricular stroke work index during aortic cross-clamping compared with values prior to anaesthesia. There were no significant changes in PCWP and CVP throughout the study. The correlations between PCWP and CVP were significant in both groups as were the correlations between the changes in PCWP and the changes in CVP observed at the time of cross-clamping. These correlations all had large standard errors of the estimate, however, making it impossible to predict the PCWP from the CVP with precision. It is concluded that, in a limited study population, an abnormal DTS did not identify patients in whom the PCWP and CVP correlated poorly during abdominal aortic aneurysmectomy.