Content area
Full Text
One of the functions of a hemodialysis machine is to measure and display arterial and venous pressures as well as to notify the operator when these pressures fluctuate outside of an established alarm limit. It is, however, the responsibility of the caregiver who monitors and interprets these pressure readings to determine how effectively or safely a treatment is being performed and to initiate appropriate interventions. A comparison of pressure readings from the patient's previous treatments at like blood pump speeds should be done each treatment to determine if the currently displayed pressures are typical or may be an indication of a problem. It is this comparison and the knowledge of acceptable pressure limits that enable caregivers to provide quality care for hemodialysis patients.
Arterial and venous pressure monitoring provides information regarding vascular access and the extracorporeal circuit in which a patient's blood is circulating. Correct interpretation of these pressures can:
1. prevent hemolysis and microbubbles in the blood tubing set from excessive negative pressure;
2. assess vascular access for adequate blood flow or problems such as venous stenosis; and
3. ensure accurate blood flow through the dialyzer for optimal dialysis therapy (Bosch & Ronco, 1993; Cogan & Schoenfeld, 1991; Francos et al., 1983; Keen, Lancaster, & Binkley, 1995; Levy, Sherman, & Nosher, 1992; National Kidney Foundation [NKF], 1997a, 1997b; Polaschegg, 1995; Twardowski, Haynie, & Moore, 1999).
To increase dialysis efficiency, high blood pump speeds are frequently used. With the limited diameters of fistula needles or catheters, high pressure gradients are created in the blood lines and high blood velocities in the narrow segments. This high blood velocity increases shear forces, which can hemolyze red blood cells. If a kink or occlusion occurs in the extracorporeal circuit, the velocity of the blood may be increased so much that, without warning (depending on the location of the kink or occlusion), massive hemolysis may occur. Symptoms of hemolysis include malaise, nausea, chest pain, shortness of breath, abdominal pain, back pain, emesis, cyanosis, headache, and increased [or decreased] blood pressure. Gallstones and pancreatitis frequently develop after a hemolytic episode (Twardowski et al., 1999).
To determine if hemolysis is occurring, place a blood sample into a clot tube and spin to separate the serum. If the serum appears pink, the...