Cardiac dysfunction during abdominal aortic operation: The limitations of pulmonary wedge pressures

Monitoring Perioperative Ischemia

This report addresses monitoring for ischemia during surgery and whether perioperative ischemia leads to increased morbidity and mortality in patients with cor onary artery disease (CAD) who are undergoing sur gery. Based on previous studies, it is generally accepted that perioperative ischemia is common in patients with CAD undergoing noncardiac surgery. The incidence of ischemia during the operative period varies greatly with cardiac risk factors, type of surgery, duration of surgery, and the monitor used to detect ischemia. Be cause perioperative cardiac morbidity is the leading cause of death after anesthesia and surgery, it is pru dent for the anesthesia clinician to have an understand ing of the tools available for monitoring as well as their clinical utility. These tools are summarized, and recom mendations are made regarding their use.

Transoesophageal echocardiography during scoliosis repair: comparison with CVP monitoring

PURPOSE

Accurate haemodynamic assessment during surgical repair of scoliosis is crucial to the care of the patient. The purpose of this study was to compare transoesophageal echocardiography (TEE) with central venous pressure monitoring in patients with spinal deformities requiring surgery in the prone position.

METHODS

Twelve paediatric patients undergoing corrective spinal surgery for scoliosis/kyphosis in the prone position were studied. Monitoring included TEE, intra-arterial and central venous pressure monitoring (CVP). Haemodynamic assessment was performed prior to and immediately after positioning the patient prone on the Relton-Hall table. Data consisted of mean arterial blood pressure (mBP), heart rate (HR), CVP, left ventricular end-systolic and end-diastolic diameters (LVESD and LVEDD respectively) and fractional shortening (FS). Right ventricular (RV) function and tricuspid regurgitation (TR) were assessed qualitatively. Analysis was performed using descriptive statistics, Student's t test, sign rank, and correlation analysis.

RESULTS

There was an increase in CVP (8.7 mmHg to 17.7 mmHg; P < .01), and decreases in LVEDD (37.1 mm to 33.2 mm; P < .05), and mean blood pressure (75.0 mmHg to 65.7 mmHg; P < .05) when patients were placed in the prone position. Fractional shortening, LVESD, and HR did not change from the supine to the prone position. Right ventricular systolic function and tricuspid regurgitation were unchanged.

CONCLUSION

These data indicate that the CVP is a misleading monitor of cardiac volume in patients with kyphosis/scoliosis in the prone position. This is consistent with previous studies. In this clinical situation, TEE may be a more useful monitoring tool to assess on-line ventricular size and function.

The utility of hemodynamic measurements acquired by pulmonary artery catheterization

BACKGROUND

Concerns about the utility of pulmonary artery catheters (PAC) stimulated us to assess the impact of one of the parameters measured by the PAC, the pulmonary capillary wedge pressure (PCWP), on our clinical practice.

METHODS

The PCWP was recorded at 4- to 6-hour intervals on 50 patients for the first 48 hours following aortic aneurysm repair. We then reviewed the patients' records looking for evidence that the PCWP measurements were used to guide therapy. For the purpose of the study, we anticipated the administration of diuretics for PCWP > or =218 mm Hg and volume resuscitation for PCWP < or =8 mm Hg. Data were correlated using Pearson rank correlation coefficient using a P < 0.05 to determine statistical significance.

RESULTS

Patients with PCWPs <8 mm Hg were more likely to be treated with volume resuscitation (P < 0.05). There was no other correlation between PCWP measurements and fluid or pharmacologic management.

CONCLUSIONS

Data derived from the PAC are infrequently used to guide therapy in patients who undergo abdominal aortic reconstructive surgery.

The Role of Pulmonary Artery Catheterization in the Management of Cardiothoracic Surgical Patients

Pulmonary artery catheterization (PAC) is a commonly used method for assessment of perfusion in critically ill patients, especially cardiothoracic surgical patients. A vast amount of clinical experience indicates that PAC provides clinicians with information about the cardiovas cular system that is otherwise not readily available at the bedside. This information is then used for the diagnosis of various hemodynamic abnormalities and subsequently to guide and judge the efficacy of thera peutic interventions. A number of small, but highly controlled, studies have suggested that outcome can be improved when data from PAC are used to guide therapy in a specific manner. Studies that have not defined specific treatment endpoints based on findings derived from PAC have failed to demonstrate outcome differences, especially when relatively small numbers of low-risk patients have been studied. A large number of other factors have precluded formal scientific validation of definitive outcome differences with PAC, and, until data are available from appropriately designed, ad equately powered trials without randomization break down, rigorous analysis of available data does not justify any immediate change in the use of PAC. Hemo dynamic monitoring with PAC remains an important aspect of care during and especially after major cardio vascular surgery, and selective use in high-risk patients appears to be the most prudent and cost-effective application of this technology.

Effects of posture and pneumoperitoneum during anaesthesia on the indices of left ventricular filling

BACKGROUND

Laparoscopic surgery requires the use of pneumoperitoneum (PP). When combined with positional changes, pneumoperitoneum may cause marked circulatory alterations.

METHODS

Eight anaesthetized cardiovascularly healthy patients, scheduled for laparoscopic cholecystectomy, were studied before and during pneumoperitoneum in three different postures (supine, Trendelenburg and reversed Trendelenburg), employing transesophageal echocardiography and pulmonary artery pressure monitoring.

RESULTS

PP significantly increased end-diastolic area (EDA) and pulmonary capillary wedge pressure (PCWP) irrespective of posture. PCWP was significantly influenced by postural changes, whereas EDA was not. Further, changes in EDA and PCWP covaried during the investigation, but showed no linear correlation. Systolic function, measured as end-systolic area (ESA) and fractional area shortening (FAS), was not altered. Diastolic function, as assessed by the velocity rate of the transmitral flow during the early filling phase (E) and the atrial contraction (A), showed no change of the E/A ratio, whereas after the induction of PP there was a significant reduction of the E component.

CONCLUSIONS

In cardiovascularly healthy patients, the left ventricular volume is increased during pneumoperitoneum. Further, changes in invasive pressure determinations (PCWP) do not correlate linearly with changes in volume indices of left ventricular filling (EDA).

Left ventricular dysfunction during infrarenal abdominal aortic aneurysm repair

BACKGROUND

Clinical observations suggest that pulmonary artery occlusion pressure (PAOP) underestimates the resuscitative volumes required prior to release of aortic cross-clamp.

METHODS

To investigate pressure-volume relationships associated with repair of abdominal aortic aneurysm (AAA), we simultaneously monitored PAOP by pulmonary artery catheter (PAC) and estimated left ventricular (LV) diastolic volume using two-dimensional transesophageal echocardiography (TEE) in 22 patients undergoing AAA repair. Data from PAC monitoring and TEE were collected before, during, and after aortic occlusion. TEE cross-sectional images were obtained at the mid-papillary level.

RESULTS

Overall, PAOP correlated with left ventricular end-diastolic area (LVEDA), but the correlation was not particularly strong (r = 0.37, P < 0.0001). Even within individual patients, LVEDA varied widely for a given PAOP. The strength of the correlation between PAOP and LVEDA also appeared to deteriorate during the course of surgery. The best correlation was seen prior to aortic cross-clamping (r = 0.50, P < 0.0001), but fell somewhat during aortic cross-clamping (r = 0.41, P < 0.0001), and even further after unclamping (r = 0.25, P = 0.005).

CONCLUSION

This study demonstrates a relatively weak correlation between PAOP and LVEDA using intraoperative TEE during AAA repair. Furthermore, the strength of the correlation worsened during surgery, particularly after unclamping. Although unclear at this time, this finding may be attributable to changes in LV compliance. We found TEE to be a valuable adjunct in guiding volume resuscitation of patients undergoing AAA repair.

Transesophageal echocardiography for hemodynamic management of thoracoabdominal aneurysm repair

Maintenance of cardiovascular stability during thoracoabdominal aneurysm repair remains a formidable challenge. Transesophageal echocardiography (TEE) has been shown to be an excellent method for detecting myocardial ischemia and assessing left ventricular volume. We examined the utility of TEE in a group of 17 patients from an overall series of 33 patients who underwent thoracoabdominal aneurysm resection between 1988 and 1992. The mortality rate was 9%, whereas the incidences of myocardial infarction and paraplegia were 13% and 6%, respectively. Intraoperative management was significantly altered by TEE data in nine patients. Two patients were noted to have mitral valve insufficiency, and one had transient ischemia-induced regional wall abnormalities. In six patients, Swan-Ganz-derived filling data failed to identify severe hemodynamic alterations that were noted on TEE. Five patients were hypovolemic and hyperdynamic, whereas one was in florid congestive heart failure. Further investigation is warranted to prospectively validate this technique.

Do changes in pulmonary capillary wedge pressure adequately reflect myocardial ischemia during anesthesia? A correlative preoperative hemodynamic, electrocardiographic, and transesophageal echocardiographic study

Pulmonary capillary wedge pressure (PCWP) is monitored during anesthesia in an attempt to detect changes in myocardial function in patients at risk of preoperative cardiac complications. Because the sensitivity with which preoperative PCWP monitoring indicates myocardial ischemia is uncertain, we monitored PCWP, 12-lead electrocardiogram, and left ventricular wall motion abnormalities as defined by transesophageal echocardiography (TEE) in 98 anesthetized patients before coronary artery bypass grafting. Measurements were made five times in each patient, before and after induction of anesthesia. Myocardial ischemia was identified by TEE in 14 patients; in 10 of these, it was associated with concomitant ST segment depression of at least 1 mm. The onset of ischemia, as defined by TEE, was accompanied by a mean increase in PCWP of 3.5 +/- 4.8 mm Hg, as compared with a mean change of 0 +/- 2.2 mm Hg between observations not associated with the onset of ischemia (p less than 0.01). An increase in PCWP of at least 3 mm Hg, tested as an indicator of ischemia, had a sensitivity of 25% and a positive predictive value of 15%; after correction for background changes associated with anesthetic induction, the sensitivity of this indicator was 33%, and its positive predictive value was 16%. These figures were not improved by selecting cutoff points higher or lower than 3 mm Hg. In this study, the onset of myocardial ischemia was associated with a small yet significant increase in mean PCWP at group level.(ABSTRACT TRUNCATED AT 250 WORDS)

Visceral and limb perfusion during thoracoabdominal aortic aneurysm repair

Patients undergoing thoracoabdominal aortic aneurysm repair are at high risk of operative morbidity and death. Aortic clamping and unclamping stresses the myocardium, interrupts visceral and limb perfusion, and leads to metabolic acidosis. Use of a simple technique to preserve distal perfusion during the period of aortic clamping may reduce perioperative morbidity. We describe a technique of visceral and limb perfusion that may reduce surgical risk in high-risk patients.

Prevention and management of surgical complications during repair of abdominal aortic aneurysms

Abdominal aortic aneurysms can be repaired with a mortality rate of 3 per cent or less under optimal conditions. To achieve these results, every effort must be made to prevent disastrous surgical complications in this elderly population. This review covers some of the more common and serious complications associated with aneurysm repair: their causation, prevention, diagnosis, and treatment. The majority of these complications are preventable with a carefully planned and executed operation. The result will be a patient with a normal age-adjusted life expectancy.

Intraoperative management of abdominal aortic aneurysms. The anesthesiologist's viewpoint

Factors that influence the choice of anesthetic, monitoring methods, and fluid management for aneurysm repair are reviewed, with particular attention to epidural anesthesia and analgesia and the pulmonary artery catheter. Management of bleeding, renal preservation, temperature control, and myocardial ischemia are discussed, and special anesthetic issues associated with ruptured aneurysms and juxtarenal and suprarenal surgery are summarized.

Neuroleptanesthesia versus thoracic epidural anesthesia for abdominal aortic surgery

The hemodynamic consequences of abdominal aortic surgery with infrarenal cross-clamping were studied in 21 patients randomized in two groups. In Group I (11 patients), neuroleptanesthesia was utilized, while Group II (10 patients) received thoracic epidural anesthesia at the T8-9 level. Hemodynamic measurements were performed using Swan-Ganz catheters during the surgical procedures in all patients, with special attention to the periods of clamping and unclamping of the abdominal aorta. The thoracic epidural anesthesia group was characterized by greater hemodynamic stability during surgery, while patients in the neuroleptanesthesia group had significant lability of blood pressure, heart rate, and cardiac index. Nevertheless, in the two groups of patients, it is suggested that cardiac function was unfitted to the tissue oxygen demand after unclamping of the aortic prosthesis because the saturation in oxygen of the mixed venous blood and an increase in arteriovenous difference in oxygen were documented. These results point out that, whatever the anesthesia technique, the critical period in abdominal surgery could be aortic unclamping.

The influence of collateral vascularisation on haemodynamic performance during abdominal aortic surgery

The extent of periaortic collateral vascularisation has been proposed as a possible mechanism of an altered haemodynamic response to infra-renal aortic cross-clamp in patients undergoing by-pass grafting for aorto-iliac occlusive disease (AOD) compared with patients undergoing abdominal aortic aneurysm (AAA) resection. The haemodynamic responses following clamping, during the clamp time and following clamp release were studied in 18 patients undergoing AAA resection and 12 patients undergoing bypass grafting for AOD. The role of preoperative aortography in predicting cardiovascular performance during aortic vascular surgery was assessed. During the cross-clamp period LVSWI and CI decreased while SVR increased in the AAA group while the AOD group showed an improved CI, stable LVSWI and reduced SVR, which correlated with the extent of periaortic vascularisation on preoperative aortography. Chronic collateral circulation associated with AOD may permit continuous lower extremity perfusion during aortic cross-clamp. The extent of periaortic collateralisation may influence the choice of monitoring techniques and anaesthetic management.