Anesth Analg 2004;99:1035-1037
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000130853.58560.5D
CARDIOVASCULAR ANESTHESIA
Peripheral Venous Pressure as a Measure of Venous Compliance During Pheochromocytoma Resection
Toby N. Weingarten, MD,
Juraj Sprung, MD PhD, and
James R. Munis, MD PhD
Department of Anesthesiology, Mayo Clinic College of Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota
Address correspondence and reprint requests to James R. Munis, MD, PhD, Department of Anesthesiology, Mayo Clinic College of Medicine, Mayo Clinic, 200 First St., SW, Rochester, MN 55905. Address e-mail to munis.james{at}mayo.edu
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Abstract
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Venous pressures measured from peripheral venous catheters (PVP) closely estimate the central venous pressure (CVP) in surgical and critically ill patients. CVP is often used to estimate intravascular volume; however, fluctuations of CVP may also be induced by changes in venous tone caused by 
-adrenergic catecholamine stimulation. We simultaneously monitored PVP, CVP, and mean arterial blood pressure during resection of pheochromocytoma in a 63-yr-old woman and found excellent correlation between the three pressure variables, suggesting that fluctuations of PVP reflect overall changes in vascular tone.
IMPLICATIONS: Both peripheral and central venous pressures reflect changes in venous tone during resection of a pheochromocytoma.
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Introduction
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Under most circumstances, measurement of central venous pressure (CVP) provides the clinician with a value that is essentially equal to right atrial pressure. The CVP is influenced by numerous variables, including intravascular volume, venous tone or compliance, right ventricular function, intrathoracic pressure, as well as conditions such as decreased right ventricular compliance and tricuspid valve dysfunction (1). Clinically, CVP is often used to estimate right ventricular preload which serves as a surrogate for intravascular volume and can help guide fluid management. Recently, studies have demonstrated that venous pressures measured from peripheral venous catheters (PVP) closely estimate the CVP and/or CVP trends in both surgical (2–5) and critically ill (6,7) patients. Fluctuation of CVP may be induced by changes in venous compliance during administration of vasoactive drugs. It is not known if the PVP reflects these changes in venous compliance. Resection of pheochromocytoma is usually associated with minimal blood loss and with large hemodynamic oscillations caused by systemic catecholamine release (8); therefore, this surgery is an ideal model for studying the changes in venous compliance. We describe a case in which a pheochromocytoma was resected with simultaneous monitoring of PVP, CVP, and mean arterial blood pressure (MAP).
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Case Report
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A 63-yr-old, 66-kg woman with pheochromocytoma was admitted for a right adrenalectomy. Preoperative work-up revealed increased plasma-free metanephrine (15.3 nmol/L, normal <0.50 nmol/L), and free normetanephrine (143 nmol/L, normal <0.90 nmol/L). Twenty-four-hour urinalysis revealed increased urine metanephrine (5786 µg/24 h, normal 30–180 µg/24 h), normetanephrine (29,000 µg/24 h, normal 138–521 µg/24 h), total metanephrines (34,786 µg/24 h, normal 171–616 µg/24 h), norepinephrine (271 µg/24 h, normal 15–80 µg/24 h), and epinephrine (61 µg/24 h, normal 0.0–20 µg/24 h). An abdominal magnetic resonance imaging study demonstrated an 8 x 9 cm right adrenal mass consistent with pheochromocytoma. Her medical history included adult onset diabetes mellitus and a right carotid endarterectomy. A preoperative transthoracic echocardiogram found the left ventricle to be of normal size and function with mildly increased concentric wall thickness. Ejection fraction was 65%. Her preoperative medications were phenoxybenzamine 20 mg twice a day, propranolol 10 mg 4 times a day, amlodipine and benazepril 5/20 mg twice a day, pioglitazone 45 mg once a day, glipizide 5 mg twice a day, lantus insulin 20 U each morning, and simvastatin 40 mg once a day. Her physical examination was unremarkable at the time of surgery.
Upon arriving to the surgical suite, a 20-gauge 2-in. radial arterial catheter, a left internal jugular quad-lumen 16-cm central venous catheter, and a 14-gauge 2
-in. right antecubital peripheral IV catheter were placed. The 14-gauge catheter and the port of the central catheter used to monitor PVP and CVP, respectively, were used solely as monitors and were not used for fluid administration. MAP, CVP, and PVP were monitored independently using a standard analog disposable pressure transducer kit with a dynamic frequency response of 40 Hz for the fluid-filled tubing and >200 Hz for the pressure transducer alone (Pressure Monitoring Set PX-MK053; Edwards Lifesciences, Irvine, CA). The transducers were repeatedly zeroed during measurements at mid-thorax level. No drift was observed. We induced anesthesia with midazolam, fentanyl, and propofol and maintained it with isoflurane in a mixture of nitrous oxide and oxygen. Neuromuscular blockade was accomplished with vecuronium. The patient was maintained in the supine position. Her arms were abducted 80 degrees from her trunk, elbows extended, hands supinated, and the arms secured on padded arm boards. The 14-gauge antecubital catheter site was under direct vision of the anesthesiologist throughout the procedure. Surgical approach was via an open laparotomy. Intraoperative MAP and heart rate oscillations were treated with nitroprusside and esmolol infusions and intermittent boluses of esmolol and phenylephrine. No boluses of phenylephrine were administered during the data collection period. During the data collection period, 1150 mL of lactated Ringer’s solution and 500 mL of 6% hetastarch were administered. Urine output was 2.5 mL · kg–1 · h–1. Estimated blood loss was 300 mL. She was discharged home on postoperative day seven.
MAP, CVP, and PVP measurements were simultaneously recorded every 60 s, and analyzed from the electronic medical records. An 84-min recording period began just before incision and ended during skin closure. The patient had significant hemodynamic lability especially with surgical incision and during tumor manipulation. Linear regression analysis was performed to calculate Pearson correlation coefficients among the three variables. Figure 1 depicts the correlation between PVP and CVP (r2 = 0.87, P < 0.0001, PVP = 1.2 + 1.01 x CVP). Figure 2 depicts the correlation between CVP and MAP (r2 = 0.58, P < 0.0001, CVP = 4.05 + 0.10 x MAP), and PVP and MAP (r2 = 0.43, P < 0.0001, PVP = 6.06 + 0.09 x MAP).
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Figure 1. The correlation between venous pressure measured from peripheral venous catheters (PVP) and central venous pressure (CVP) during surgical resection of pheochromocytoma. The line represents the linear regression. Number of measurements is 84 (because of overlap, all points are not seen).
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Figure 2. The correlation between central venous pressure (CVP) and mean arterial blood pressure (MAP), and venous pressure measured from peripheral venous catheters (PVP) and MAP during surgical resection of pheochromocytoma. The line represents the linear regression.
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Discussion
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We simultaneously monitored PVP, CVP, and MAP during resection of pheochromocytoma and we found good correlation among these three variables. Acute variations in MAP during pheochromocytoma resection are typically caused by acute catecholamine release, and not by acute volume changes. Because -adrenergic stimulation increases vascular stiffness (9,10), good correlation between MAP, CVP, and PVP in our patient (Figs. 1 and 2) reflects simultaneous and same-direction changes in systemic vascular resistance and central and peripheral venous compliances. These correlations suggest that PVP reflects changes in vascular tone in a similar manner as CVP.
Several previous studies demonstrated that during volume loading PVP correlates with CVP, therefore measurement of PVP may be a reliable tool for estimating intravascular volume by a less invasive means (2–7). Two of these studies demonstrated that the gauge of the peripheral IV catheter did not affect PVP measurements (3,5). Although the PVP measurement does not give an accurate estimate of the absolute CVP value in individual patients (6), the changes in PVP parallel in direction the changes in CVP. Therefore, serial measurements of PVP may have a value in determining volume status and guiding fluid therapy even in critically ill patients (6). PVP has also been shown to estimate pulmonary artery pressure, as Milhoan et al. (7) found an excellent correlation (r = 0.97) between upper-extremity PVP and CVP or pulmonary artery pressure in patients who had undergone cavopulmonary or Fontan procedures. Finally, Munis et al. (2) measured PVP during planned circulatory arrest and their findings support the hypothesis that PVP approximates mean systemic pressure (circulatory arrest pressure), which is a direct ratio of total blood volume to vascular compliance independent of cardiac or respiratory activity.
Those studies (2–7) focused on PVP as an estimate for intravascular volume status. The observations made during this case build upon and reinforce the assumption that PVP reflects not only volume status, but venous tone as well. -Adrenergic agonists are venous and arterial constrictors (10). Vincent et al. (9) compared peripheral venous responsiveness (dorsal hand vein compliance technique) and systemic vascular responsiveness (arterial blood pressure changes) to -adrenergic stimulation and found that dorsal hand vein compliance approximates systemic hemodynamic changes. Pheochromocytoma resections are accompanied by rapid changes in circulatory catecholamines (8); however, these changes were not measured but rather presumed in our patient. The fact that PVP parallels changes in CVP in a relatively euvolemic state (pheochromocytoma resection) is consistent with a century-old assumption that venous pressures reflect venous tone and not just blood volume (11,12). Different methods have been developed and tested for measuring venous compliance in humans, but these methods are time consuming, have major limitations, and are technically not applicable for routine clinical use (13,14). Our case report is the first attempt to use the PVP as an estimate of global venous compliance.
Because PVP reflects changes in both volume (2–7) and venous tone, it may be a useful monitoring modality during surgeries that do not require insertion of central catheters (such as for administration of drugs centrally, measurement of cardiac output, and fast replenishing of lost blood volume). Measuring the PVP is an inexpensive and noninvasive means of obtaining this information. However, PVP has several limitations. If the column of fluid between the orifice of the catheter and the right atrium is interrupted (i.e., a tourniquet, or a clot at the catheter tip), the PVP value is not meaningful. Also, the value may be suspect if IV fluids are being administered in a vein in close proximity to the catheter (i.e., same limb).
In conclusion, our patient undergoing resection of a pheochromocytoma presented an opportunity to simultaneously monitor PVP and CVP during abrupt catecholamine changes. The fact that both the PVP and CVP correlated with catecholamine-induced acute MAP oscillations is consistent with the assumption that there is a close coupling between the systemic vascular response (MAP) and venous tone (PVP and CVP) (9). The correlation between PVP and CVP in this context (Fig. 1) suggests that either variable reflects venous tone, just as the prospective studies (2–7) suggest that changes in either variable reflect changes in blood volume.
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Acknowledgments
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Support for this study provided from the Department of Anesthesiology, Mayo Clinic, Rochester, MN.
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Footnotes
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Dr. Munis is a patent holder for a device which measures peripheral venous pressure (PVP; US Patent 6,623,470). That device was not used in the current studies.
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References
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Accepted for publication April 16, 2004.
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Abstract
Introduction
