CVP

central

[sen´tral] pertaining to a center; located at the midpoint.central cord syndrome injury to the central portion of the cervical spinal cord resulting in disproportionately more weakness or paralysis in the upper extremities than in the lower; pathological change is caused by hemorrhage or edema.

Central cord syndrome. From Ignatavicius and Workman, 2002.central fever sustained fever resulting from damage to the thermoregulatory centers of the hypothalamus.central nervous system the portion of the nervous system consisting of the brain and spinal cord. See also Plate 14.central venous catheterization insertion of an indwelling catheter into a central vein for administering fluid and medications and for measuring central venous pressure. The most common sites of insertion are the jugular and subclavian veins; however, such large peripheral veins as the saphenous and femoral veins can be used in an emergency even though they offer some disadvantages. The procedure is performed under sterile conditions and placement of the catheter is verified by x-rays before fluids are administered or central venous pressure measurements are made.
Selection of a large central vein in preference to a smaller peripheral vein for the administration of therapeutic agents is based on the nature and amount of fluid to be injected. Central veins are able to accommodate large amounts of fluid when shock or hemorrhage demands rapid replacement. The larger veins are less susceptible to irritation from caustic drugs and from hypertonic nutrient solutions administered during parenteral nutrition.Patient Care. Patients who have central venous lines are subject to a variety of complications. Air embolism is most likely to occur at the time a newly inserted catheter is connected to the intravenous tubing. Introduction of air into the system can be avoided by having the patient hold his breath and contract the abdominal muscles while the catheter and tubing are being connected. This maneuver increases intrathoracic pressure; if the patient is not able to cooperate, the connection should be made at the end of exhalation.
Sepsis is a potential complication of any intravenous therapy. It is especially dangerous for patients with central venous lines because they are seriously ill and less able to ward off infections. Careful cleansing of the insertion site, sterile technique during insertion, periodic changing of tubing and catheter, and firmly anchoring the catheter to prevent movement and irritation are all essential for the prevention of sepsis.
Formation of a clot at the tip of the catheter is indicated if the rate of flow of intravenous fluids decreases measurably or if there is no fluctuation of fluid in the fluid column. Preventive measures include maintaining a constant flow of intravenous fluids by IV pump or controller, periodic flushing of the catheter, heparin as prescribed, and looping and securing the catheter carefully to avoid kinks that impede the flow of fluids. Cardiac arrhythmias can occur if the tip of the catheter comes into contact with the atrial or ventricular wall. Changing the patient's position may eliminate the problem, but if ectopic rhythm persists, additional interventions are warranted.central venous pressure (CVP) the pressure of blood in the right atrium. Measurement of central venous pressure is made possible by the insertion of a catheter through the median cubital vein to the superior vena cava. The distal end of the catheter is attached to a manometer (or transducer and monitor) on which can be read the amount of pressure being exerted by the blood inside the right atrium or the vena cava. The manometer is positioned at the bedside so that the zero point is at the level of the right atrium. Each time the patient's position is changed the zero point on the manometer must be reset. For a multilumen catheter the distal port is used to measure central venous pressure; for a pulmonary artery catheter the proximal port is used.
An arterial line can also be used to monitor the central venous pressure. The waveform for a tracing of the pressure reflects contraction of the right atrium and the concurrent effect of the ventricles and surrounding major vessels. It consists of a, c, and v ascending (or positive) waves and x and y descending (or negative) waves. Since systolic atrial pressure (a) and diastolic (v) pressure are almost the same, the reading is taken as an average or mean of the two.
The normal range for CVP is 0 to 5 mm H₂O. A reading of 15 to 20 mm usually indicates inability of the right atrium to accommodate the current blood volume. However, the trend of response to rapid administration of fluid is more significant than the specific level of pressure. Normally the right heart can circulate additional fluids without an increase in central venous pressure. If the pressure is elevated in response to rapid administration of a small amount of fluid, there is indication that the patient is hypervolemic in relation to the pumping action of the right heart. Thus, CVP is used as a guide to the safe administration of replacement fluids intravenously, particularly in patients who are subject to edema" >pulmonary edema. Central venous pressure indirectly indicates the efficiency of the heart's pumping action; however, pulmonary artery pressure is more accurate for this purpose.
A high venous pressure may indicate heart failure" >congestive heart failure, hypervolemia, tamponade" >cardiac tamponade in which the heart is unable to fill, or vasoconstriction, which affects the heart's ability to empty its chambers. Conversely, a low venous pressure indicates hypovolemia and possibly a need to increase fluid intake.

pressure

(P) [presh´ur] force per unit area.arterial pressure (arterial blood pressure) blood pressure (def. 2).atmospheric pressure the pressure exerted by the atmosphere, usually considered as the downward pressure of air onto a unit of area of the earth's surface; the unit of pressure at sea level is one atmosphere. Pressure decreases with increasing altitude.barometric pressure atmospheric p.blood pressure 1. see blood pressure.2. pressure of blood on walls of any blood vessel.capillary pressure the blood pressure in the capillaries.central venous pressure see central venous pressure.cerebral perfusion pressure the mean arterial pressure minus the intracranial pressure; a measure of the adequacy of cerebral blood flow.cerebrospinal pressure the pressure of the cerebrospinal fluid, normally 100 to 150 mm Hg.continuous positive airway pressure see continuous positive airway pressure.filling pressure see pressure" >mean circulatory filling pressure.high blood pressure hypertension.intracranial pressure see intracranial pressure.intraocular pressure the pressure exerted against the outer coats by the contents of the eyeball.intrapleural pressure (intrathoracic pressure) pleural pressure.intrinsic positive end-expiratory pressure elevated pressure" >positive end-expiratory pressure and dynamic pulmonary hyperinflation caused by insufficient expiratory time or a limitation on expiratory flow. It cannot be routinely measured by a ventilator's pressure monitoring system but is measurable only using an expiratory hold maneuver done by the clinician. Its presence increases the work needed to trigger the ventilator, causes errors in the calculation of pulmonary compliance, may cause hemodynamic compromise, and complicates interpretation of hemodynamic measurements. Called also auto-PEEP and intrinsic PEEP.maximal expiratory pressure maximum expiratory pressure.maximal inspiratory pressure the pressure during inhalation against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H₂O is associated with successful weaning.maximum expiratory pressure (MEP) a measure of the strength of respiratory muscles, obtained by having the patient exhale as strongly as possible against a mouthpiece; the maximum value is near capacity" >total lung capacity.maximum inspiratory pressure (MIP) the inspiratory pressure generated against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H₂O is associated with successful weaning.mean airway pressure the average pressure generated during the respiratory cycle.mean circulatory filling pressure a measure of the average (arterial and venous) pressure necessary to cause filling of the circulation with blood; it varies with blood volume and is directly proportional to the rate of venous return and thus to cardiac output.negative pressure pressure less than that of the atmosphere.oncotic pressure the osmotic pressure of a colloid in solution.osmotic pressure the pressure required to stop osmosis through a semipermeable membrane between a solution and pure solvent; it is proportional to the osmolality of the solution. Symbol π.partial pressure the pressure exerted by each of the constituents of a mixture of gases.peak pressure in mechanical ventilation, the highest pressure that occurs during inhalation.plateau pressure in mechanical ventilation, the pressure measured at the proximal airway during an end-inspiratory pause; a reflection of alveolar pressure.pleural pressure the pressure between the visceral pleura and the thoracic pleura in the pleural cavity. Called also intrapleural or intrathoracic pressure.positive pressure pressure greater than that of the atmosphere.positive end-expiratory pressure (PEEP) a method of control mode ventilation in which positive pressure is maintained during expiration to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. A PEEP higher than the critical closing pressure prevents alveolar collapse and can markedly improve the arterial Po₂ in patients with a lowered functional residual capacity, as in acute respiratory failure.

Effects of the application of positive end-expiratory pressure (PEEP) on the alveoli. A, Atelectatic alveoli before PEEP application. B, Optimal PEEP application has reinflated alveoli to normal volume. C, Excessive PEEP application overdistends the alveoli and compresses adjacent pulmonary capillaries, creating dead space with its attendant hypercapnia. From Pierce, 1995.pulmonary artery wedge pressure (PAWP) (pulmonary capillary wedge pressure (PCWP)) intravascular pressure, reflecting the left ventricular end diastolic pressure, measured by a swan-ganz catheter wedged into a small pulmonary artery to block the flow from behind.pulse pressure the difference between the systolic and diastolic pressures. If the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg, the pulse pressure is 40 mm Hg; the normal pulse pressure is between 30 and 40 mm Hg.urethral pressure the pressure inwards exerted by the walls of the urethra, which must be counteracted in order for urine to flow through; see also profile" >urethral pressure profile.venous pressure the blood pressure in the veins; see also central venous pressure" >central venous pressure.water vapor pressure the tension exerted by water vapor molecules, 47 mm Hg at normal body temperature.wedge pressure blood pressure measured by a small catheter wedged into a vessel, occluding it; see also pulmonary capillary wedge pressure and wedged hepatic vein pressure.wedged hepatic vein pressure the venous pressure measured with a catheter wedged into the hepatic vein. The difference between wedged and free hepatic vein pressures is used to locate the site of obstruction in portal hypertension; it is elevated in that due to cirrhosis, but low in cardiac ascites or portal vein thrombosis.

CVP

Abbreviation for central venous pressure.

CVP

Central venous pressure, see there.

CVP

Abbreviation for central venous pressure.