Effect of airway pressure on inferior vena cava pressure as a measure of central venous pressure in children

Effect of airway pressure on inferior vena cava pressure as a measure of central venous pressure in children

The Journal of Pediatrics Volume 126, Number 6 8. Ng SC, Koong PL. A study of 31 patients with easy bruising from University Hospital, Kuala Lumpur. ...

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The Journal of Pediatrics Volume 126, Number 6

8. Ng SC, Koong PL. A study of 31 patients with easy bruising from University Hospital, Kuala Lumpur. Med J Malaysia 1990;45:325-8. 9. Karpatkin S, Lackner HL. Association of antiplatelet antibody with functional platelet disorders: autoimmune thrombocy-

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topenic purpura, systemic lupus erythematosus and thrombopathia. Am J Med 1975;59:599-604. 10. WeissHJ, Rosove MH, Lages BA, Kaplan KL. Acquired storage pool deficiencywith increased platelet-associatedIgG: report of five cases. Am J Med 1980;69:711-7.

Effect of airway pressure on inferior v e n a c a v a pressure as a measure of central venous pressure in children Zacharia Reda, MD, Sion Houri, MD, Alan L. Davis, MD, and Victor C. Baum, MD From the Departments of Pediatrics and Anesthesiology, University of California, Los Angeles, and Miller Children's Hospital Long Beach, California

We evaluated the effect of elevated airway pressure on the validity of intravascular pressure obtained in the distal inferior vena cava (IVC) as a measure of central venous pressure (CVP) in a group of children receiving mechanical ventilation. The IVC pressure correlated well with CVP in the patients without abdominal distention, but the disparity was wider in those with abdominal distention. Elevated mean airway pressure or positive end-expiratory pressure had no effect on the relationship of IVC to CVP. (J PEDIATR1995;126:961-5) Catheterization of the femoral vein in children has been shown to be safe, 1,2 but the comparability of pressure measured in the abdominal inferior vena cava as compared with the right atrium in patients receiving mechanical ventilation with increased intrathoracic pressure remains undetermined. In addition, the relationship of IVC and central venous pressure measured from within the thorax in the face of abdominal distention has not been evaluated. Three reports have evaluated the correlation of IVC and superior vena cava pressures. 3-5 However, these studies were done in dogs 3 or in children in the cardiac catheterization laboratory4 or the intensive care unit5 who did not have pulmonary disease or high airway pressures. This study was designed to address

Presented in part at the annual meeting of the Society for Pediatric Research, Seattle, Wash., May 1994. Submitted for publication Sept. 30, 1994; accepted Jan. 20, 1995. Reprint requests: Victor C. Bantu, MD, Department of Anesthesiology, Box 238, University of Virginia Medical Center, Charlottesville, VA 22908. Copyright © 1995 by Mosby-Year Book, Inc. 0022-3476/95/$3.00 + 0 9122163483

the appropriateness of using IVC catheters as a reflection of CVP in pediatric patients receiving mechanical ventilation at high airway pressures. Critically ill pediatric patients occasionally require multiple central venous catheters. We took advantage of this clinical practice to compare pressures obtained via femoral and thoracic venous catheters in patients whose lungs were mechanically ventilated with the use of routine clinical equipment in a clinical setting. We hypothesized that these presCVP IVC MAP PEEP SVC

Cen~calvenouspressure Inferiorvena cava Meanairway pressure Positiveend-expiratorypressure Superiorvena cava

sures would be similar. In addition, we analyzed separately data from a group of pediatric patients receiving mechanical ventilation who were judged clinically to have increased intraabdominal pressure, tt was expected that the disparity between IVC and SVC pressures in this group would be increased, making IVC pressure measurements unreliable as an indicator of CVP.

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METHODS This study was approved by the appropriate human subject protection committees. The need for informed consent was waived by these institutional review boards. No interventions were done solely for the purpose of the study. All patients had had percutaneous placement of 4F 8 cm double-lumen catheters (Cook Critical Care, Bloomington, Ind.) into a femoral vein and into the SVC through either the internal jugular or subclavian veins. Multiple data points were collected at different levels of positive end-expiratory pressure and mean airway pressure for each patient. Each

data point represented a mean of three readings done at least 30 minutes after any interventions. Catheter positions were verified radiographicalty. Femoral catheter tips were in the iliac vein and the SVC catheters were at the SVC-right atrium junction. All data were collected while patients with mechanically ventilated lungs were in the supine position. We previously documented that CVP as measured by our bedside monitors reliably reproduces measurements of CVP made manually at end-exhalation. 5 Auto-PEEP was measured by introducing an expiratory hold during mechanical ventilation. Patients

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Mean Venous Pressure (mm Hg) Fig. 2. Difference in pressures (IVC - SVC) versus MAP in patients with no abdominal distention (A) (bias, 1.0 mm Hg) and in patients with abdominal distention (B) (bias, 4.5 ram). were divided into two groups: group 1 had no apparent abdominal distention, and group 2 had apparent abdominal distention. The diagnosis of abdominal distention was made clinically, and no attempt was made to measure intraabdominal pressure. Diagnoses in group 2 included recuperation from liver transplantation, abdominal mass, tension pneumoperitoneum, and massive ascites. No attempt was made to measure venous pressure at different subjective levels of abdominal pressure. Bias (mean of differences) and precision (SD of differences) of venous pressures were determined for both groups of patients. 6 Data were compared by the two-tailed paired t

test. Statistical significance was considered at a p level less than 0.05. On the basis of preliminary data showing a variance of 1.63 in the difference between measurements obtained in the two catheter positions, there was a 91% chance of detecting a difference as small as 1 mm Hg with a sample size of 20 patients, and a 98% chance with a sample size of 30. Data are expressed as mean _+ SEM. RESULTS Patients in group 1 ranged from 14 days to 16 years of age (mean, 4.3 years) with PRISM (pediatric risk of mortality)

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scores of 12 to 48 (mean, 26). Four patients from group 1 received ventilation from a high-frequency oscillator. Three of these patients also had data collected during periods of conventional ventilation. Patients in group 2 ranged from 7 months to 16 years of age (mean, 4.4 years) with PRISM scores of 12 to 42 (mean, 22). Measurements were obtained at 47 levels of PEEP (2 to 12 cm H20; mean, 7.1 - 0.4 cm H20) and 76 levels of MAP (4 to 35 cm H20; mean, 18.3 -+ 0.9 cm H20) in 17 patients in group 1, and at 41 levels of PEEP (0 to 16 cm H20; mean, 7.7 + 0.5 cm H20) and 47 levels of MAP (2 to 29 cm H20; mean, 16.3 -+ 1.0 cm H20 ) in 11 patients in group 2. Measured PEEP represented the sum of auto-PEEP and applied PEEP. Patients in group 1 had a good correlation of IVC and SVC pressure (R2 = 0.93; maximum difference, 3 mm Hg). Group 2 showed wider variation (R2 = 0.86; maximum difference, 10 mm Hg) (Fig. 1). Neither PEEP nor MAP had any effect on the IVC-SVC pressure difference in group 1 (R2 = 0.003 and <0.001, respectively). Similarly, neither PEEP or MAP had any effect on the WC-SVC pressure relationship for group 2 ( R 2 = 0.1 and 0.05). Only two pressure differences in group 1 were as large as 3 mm Hg. In group 2, however, 50% of WC-SVC pressure differences were greater than 3 mm Hg. Bias was 1.0 mm Hg in group 1 and 4.5 mm Hg in group 2. Precision was 0.7 mm Hg for group 1 and 2.4 mm Hg for group 2 (Fig. 2). Data from individual patients were also evaluated. The IVC and SVC data from patients in group 1 were extremely close. For all data points from any single patient, only one patient had any IVC-SVC differences that were more than 1 mm Hg apart across the range of airway pressures measured. One patient had differences of 0, 1, and 2 mm Hg. The variances of the data for individual patients in group 1 ranged from 0.0 to 0.47 (mean, 0.19). Thus for any one patient the relationship of IVC to SVC pressure was unchanging as airway pressure varied. The data from individual group 2 patients were more widely dispersed. Variances for this group were from 0.06 to 7.36 (mean, 1.65).

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ever, that previous study did not specifically describe the patients or data from patients with abdominal distention. As we had hypothesized, we found that IVC pressure in the face of abdominal distention routinely overestimated and did not accurately reflect CVP, although the possibility had existed that increased fight atrial pressure and CVP from transmitted applied airway pressure might in some way keep open the inferior vena cava, equalizing IVC and SVC pressures in the presence of mild to moderate increased intraabdominal pressure. These data support the findings of the study by Lloyd et al.,4 which showed close agreement between the measurements (R2 = 0.99). Their study was done under the highly controlled and optimized conditions of the cardiac catheterization laboratory with a different technique, and did not address the effect of airway pressure on IVC. This study also confirms our previous findings in postoperative pediatric cardiac surgical patients who were spontaneously breathing and in those whose lungs were mechanically ventilated.5 That study documented good correlation between W C and right atrial pressures, with a maximum difference of 3 mm Hg. That study, however, was done in patients without significant lung disease or elevated intrathoracic pressure. None of those patients was receiving more than 3 mm Hg PEEP. Femoral venous catheters have been used successfully in pediatric populations to decrease the risk of injuring cervical and intrathoracic structures. I' 2 ff IVC pressure reliably reflects SVC and fight atrial pressure and is not affected by elevated airway pressure, it allows monitoring of CVP from short femoral catheters, avoiding the potential complications associated with SVC catheter insertion and avoiding the need to thread long catheters from the femoral vein into the thorax. In summary, this study reports the excellent correlation between SVC and W C pressures in patients undergoing mechanical ventilation with high PEEP, and MAP. This excellent correlation is valid only for supine patients with no abdominal distention.

DISCUSSION This study compared the effects of PEEP and MAP on the reliability of CVP as measured in the iliac vein in patients with and without abdominal distention. We have shown that high airway pressure (both PEEP mad MAP) does not affect this pressure as a valid measure of CVP; the difference was always 3 mm Hg or less in group 1. The two measurements with a difference of 3 mm Hg occurred in one patient early in the study, and we cannot exclude the possibility that this patient was not completely supine at the time data were collected. Unlike the situation in group 1, we found that the SVC-IVC pressure correlation in patients with abdominal distention was poor, in contrast to a previous report. 4 How-

We acknowledge the gracious help of the nurses and fellows of UCLA's and Miller Children's Hospital's pediatric intensive care units.

REFERENCES 1. Stenzel JP, Green TP, Furhrman BP. Percutaneous femoral venous catheterizations: a prospective study of complications. J PEDIA~ 1989;114:411-5. 2. Stenzel JP, Green TP, Furhrman BP. Percutaneous femoral venous catheterization in a pediatric intensive care unit: a survival analysis of complications. Crit Care Med 1989;17: 984-8. 3. Berg RA, Lloyd TR, Donnerstein RL. Accuracy of central

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venous pressure monitoring in the intraabdominal vena cava: a canine study. J PeD~ATR1992;120:67-71. 4. LIoyd TR, Donnerstein RL, Berg RA. Accuracy of central venous pressure monitoring in the intraabdominalinferior vena cava. Pediatrics 1992;89:506-8. 5. Chait HI, Kuhn MA, Baum VC. Inferior vena caval pressure

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reliably predicts right atrial pressure in pediatric cardiac surgical patients. Crit Care Med 1994;22:219-24. 6. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307-10.

Peutz-Jeghers syndrome in a neonate M. J. Fernandez Seara, MD, M. I. Martinez Soto, MD, J. R. Fernandez Lorenzo, MD, S. Trabazo, MD, E. Gamborino, MD, a n d J. Forteza Vila, MD From the Departments of Pediatrics and Pathology, Hospital General de Galicia, Santiago de Compostela, Spain

A 15-day-old girl was found to have generalized gastrointestinal polyposis resulting from Peutz-Jeghers syndrome. Her manifestations included abdominal distention, hematemesis, bloody diarrhea, and edema. She died at I year of age of multiple complications of her disease. (J PEDIATR1995;126:965-7) Submitted for publication July 11, 1994; accepted Dec. 20, 1994. Reprint requests: M. Jose Fernandez Seara, MD, Republica del Salvador No. 29-5 ° C, Santiago de Compostela 15701, La Corufia, Spain. Copyright © 1995 by Mosby-Year Book, Inc. 0022-3476/95/$3.00 + 0 9/22/62888

Peutz-Jeghers syndrome is characterized by mucocutaneous pigmentations and gastrointestinal polyps of the hamartomatous type; most polyps (50% to 90%) are located in the small intestine, t A family history of autosomal dominant transmission with incomplete penetrance is noted in 50% of the cases. 2 The clinical manifestations are recurrent abdom-

Fig. |. Jejunal polyp composed of intestinal crypts and villi with abnormal architectural arrangement. Note band of smooth muscle running between segments of this lesion. Gastric and colonic polyps had similar appearance; (Hematoxylin-eosin stain; original magnification, x40.)