Central venous pressure, pulmonary capillary wedge pressure and intrathoracic blood volumes as preload indicators in cardiac surgery patients

OBJECTIVE: Monitoring of cardiac preload is mainly performed by measurement of central venous and pulmonary capillary wedge pressure in combination with assessment of cardiac output, applying the pulmonary arterial thermal dilution technique. However, the filling pressures are negatively influenced by mechanical ventilation and the pulmonary artery catheter is criticized because of its inherent risks. Measurement of right atria, right ventricular, global end diastolic and intrathoracic blood volume index by arterial thermal dye dilution utilizing the COLD-system may represent an alternative. METHODS: In 30 CABG patients with an uncomplicated postoperative course the mentioned parameters were measured 1, 3, 6, 12 and 24 h postoperatively to prove their qualification as preload indicators: As patients received no inotropic support, changes of cardiac index and stroke volume index must correlate to changes of presumably preload indicating parameters. RESULTS: When arterial and pulmonary arterial thermal dilution were compared, no differences were found; the correlation coefficient being 0.96, the bias 0.16 l/min per m2 (2.4%) and coefficients of variation did not exceed 7%. Changes of central venous pressure, capillary wedge pressure, right atrial end diastolic volume index and right ventricular end diastolic volume index did not correlate at all to changes of cardiac and stroke volume index (coefficients ranged from -0.01 to 0.28). In contrast, intrathoracic and global end diastolic blood volume indices with coefficients from 0.76 to 0.87, did show a good correlation to cardiac and stroke volume index. CONCLUSION: Central venous pressure, capillary wedge pressure, right atrial and right ventricular end diastolic volumes are no suitable preload parameters in cardiac surgery intensive care, compared to intrathoracic and global end diastolic blood volumes. The latter show a higher clinical value and can be obtained by less invasive methods, as no pulmonary artery catheter is required.     

Complications of intravenous therapy. Influence of parenteral nutrition, central venous pressure and antibiotics

With regard to the controversy on whether the use of central venous catheters for the perfusion of other solutions as well as parenteral nutrition means an increase in the risk of sepsis caused by the catheter, a prospective study was made on 313 central intravenous catheters placed in patients admitted to the Intensive Medicine Unit of La Paz General Hospital over a one-year period. Collection of data on both catheters and patients was done following a protocol applied in all cases. From the results obtained, it can be concluded that in critical patients in whom a single central venous catheter has been placed, this can be used for the infusion of other liquids, apart from parenteral nutrition, without involving an increased risk of sepsis caused by the catheter. This pathology seems to bear more relation to the amount of time the catheter remains in place.     

Is urinary bladder pressure a sensitive indicator of intra-abdominal pressure?

Contribution of one case of right paratesticular rhabdomyosarcoma in a 3-year and 4-month old male patient. Following radical orchiectomy and clinical staging, grading is IRS Group I (fully resected localized disease). Subsequently, the patient received 7 polychemotherapy courses and was found to be asymptomatic 4 years after treatment.     

The role of intra-abdominal pressure in spinal unloading

Previous studies on how an increase in intra-abdominal pressure (IAP) effects the loading of the lumbar spine during back extension show diverging results. From a critical review of the literature we deduce a simplified, but consistent, model of the mechanisms involved in IAP-induced unloading of the lumbar spine. The model is then expanded by explicitly incorporating equilibrium equations for the pressurised abdomen and the abdominal wall. It is shown that the unloading effect of IAP can be viewed as that of a pressurised column of fixed cross-sectional area, between the rib cage and pelvis. Different abdominal forms are examined and a form with zero longitudinal curvature is found to have some important mechanical benefits for the generation of IAP-induced alleviation of compressive loading of the lumbar spine.     

Comparison of direct and acoustical area measurements in physical models of human central airways

Total cross-sectional areas were computed from direct measurements made on two human central airway casts. Acoustic pulse-response measurements were obtained on rigid-walled positive replicas of these casts. From the acoustic response data of each cast, we computed the area-distance function of the acoustically equivalent structure (i.e., the structure with regular branching and negligible viscous losses, but with similar acoustic properties). The acoustic data predicted equivalent areas that compared favorably to the total cross-sectional areas in the casts at all points from the beginning of the trachea to distances about 6 cm beyond the carina corresponding to airways of the third, fourth, or fifth generation. These results indicate that, at least in the central airways, branching asymmetry and internal energy losses introduced negligible errors in estimates of cross-sectional areas derived from acoustic pulse-response measurements. This rapid noninvasive technique thus shows promise as a method of detecting upper and central airway obstruction.     

Comparison of push-pull versus discard method from central venous catheters for blood testing

This article evaluates recent research results comparing two different methods for obtaining complete blood cell counts and chemistry profiles from central venous catheters. Complete blood cell count and chemistry profile samples were obtained from 25 patients at three hospital-based infusion clinics. The results indicate no appreciable difference between these two methods. Minimizing risks of blood loss, blood exposure to healthcare personnel, potential specimen contamination, and erroneous reporting are benefits of the push-pull method.     

Dysrhythmia update: The effect of intermittent heart block on the central venous pressure trace

A prospective study of 71 patients with hyponatraemia was undertaken over an 18-month period in one surgical unit at King Edward VIII Hospital, Durban, to study the incidence and pattern of hyponatraemia. Electrolytes and urea values were measured serially in all patients. Hyponatraemia was defined as a serum sodium level of < 130 mmol/l. The incidence of hyponatraemia was 2.2%, the most common type being normovolaemic hypotonic hyponatraemia. Hyponatraemia was either mild (sodium level 120-130 mmol/l) or moderate (111-120 mmol/l). No patient had severe hyponatraemia (< 110 mmol/l). Hyponatraemia was corrected within 1-6 days using normal saline; in 73% of patients it was corrected within 24 hours. No patient developed neurological symptoms. A mortality rate of 28% was attributed to underlying illness, and hyponatraemia per se was asymptomatic in this study. Aggressive sodium correction was therefore not indicated.     

Complications of 1303 central venous cannulations

Central venous catheterization (CVC), now a common procedure, has several major complications. We assessed their incidence in a prospective study of 1303 cannulations done in the intensive care unit or operating theatre. Chest radiographs were obtained to verify proper catheter placement and to detect pneumothorax. Complications were arterial puncture in 68 (5.2%) patients, arrhythmias in 21 (1.6%), cardiopulmonary arrest in 1 (0.1%), and pneumothorax in 5 (0.5%). The tip of the CVC was incorrectly located in 149 (11.2%). The chest radiograph was a valuable method for detecting complications of central venous catheterization.     

Management of central venous catheter occlusions and repairs

Central venous catheter (CVC) occlusions have the potential of compromising patient care because of the inability to administer needed medications, parenteral nutrition, and blood products. The practitioner responsible for the care of these catheters can be instrumental in the diagnosis and treatment of catheter-related occlusions by becoming familiar with typical complications and their causes. This article describes the causes and possible solutions for some of the most common types of mechanical, thrombus, and precipitate occlusions with the CVC. A discussion of CVC fracture will help the practitioner in the resolution of this complication.     

Mitral inflow and pulmonary venous Doppler measurements do not predict pulmonary capillary wedge pressure in heart transplant recipients

We examined the spectrum of p53 mutations found in 40 UV-induced skin tumors of xeroderma pigmentosum group A gene (XPA)-deficient mice. p53 mutations were detected in 48% of the tumors. Nearly all of the mutations were induced at dipyrimidine sites. Ninety-three % of the mutations were G.C-->A.T transitions at dipyrimidine sites, including tandem transitions (CC-->TT), which are the hallmark of the UVB-induced mutation. Seventy-two % of the mutations at dipyrimidine sites could be ascribed to damage on the transcribed strand. In addition, no evident mutational hot spots were detected. This is in contrast to the UVB-induced skin tumors of normal mice, in which 92% of p53 mutations occurred as a result of DNA damage on the nontranscribed strand, and clear hot spots were observed. Thus, XPA-deficient mice showed significant mutation features that might be characteristic of the absence of nucleotide excision repair and may provide a good animal model for the analysis of the high incidence of skin cancer in xeroderma pigmentosum group A patients.     

Prevention of indwelling central venous catheter sepsis

In an attempt to decrease the incidence of central venous catheter sepsis in children with cancer, we conducted a study to evaluate the benefit of adding broad-spectrum antibiotics to the catheter "flush solution." In a prospective, placebo-controlled, double-blinded, randomized trial, 69 children with different types of malignancies were studied. The central venous catheters in these children were flushed with either the standard solution (normal saline + 100 U/ml of heparin) or the study solution (25 microgram/ml of both amikacin and vancomycin added to the standard solution). At the conclusion of the study, 64 children with a total of 67 indwelling central venous lines were assessable. The total catheter days on study were 20,700 days, with a median of 323 catheter days per patient. We documented 10 events of catheter-related infections (0.49 events/1,000 catheter days at risk). Five of these events were catheter-related sepsis (0.24 sepses/1,000 catheter days): two were fungal and three were bacterial. Due to the low incidence of catheter-related sepsis in this study, no statement regarding the prophylactic use of antibiotics could be made. The extremely low rate of catheter-related sepsis reported herein may be retrospectively attributed to continuous staff education regarding aseptic techniques in handling these catheters. Staff education is essential, and probably the most effective factor in preventing catheter-related sepsis.     

Transfemoral repositioning of malpositioned central venous catheters

Sumatriptan, a 5-hydroxytryptamine1, (5-HT1) receptor agonist is an effective abortive agent for migraine headaches. A common side effect in 3% to 7.9% of patients is chest pain. Although most cases of chest pain are not thought to be of cardiac origin, its mechanism is not entirely understood. Rare examples of electrocardiogram changes consistent with transient ischemia have been reported. Isolated instances of angina, arrhythmia, myocardial infarction, and death have been temporally associated with sumatriptan administration. In most cases, it is unclear whether underlying cardiovascular disease existed or contributed to this adverse event. We report the history of a 56-year-old female patient with migraine who experienced a myocardial infarction shortly after using sumatriptan, despite having had a normal cardiovascular evaluation. As she had a normal cardiac catheterization after the event, we find it probable that sumatriptan induced coronary vasospasm and myocardial infarction.