Evaluation of the clinical usefulness of thermodilution volumetric catheters.

OBJECTIVE

To determine if treatment modalities (fluid, inotropes, and blood) would be altered based on preload measurements of right ventricular end-diastolic volume index measured by fast response thermodilution catheter, as compared with pulmonary artery occlusion pressure (PAOP).

DESIGN

A prospective clinical trial.

SETTING

An 11-bed surgical intensive care unit (ICU) at The Queen's Medical Center, an affiliate of the University of Hawaii Surgical Residency program.

PATIENTS

Surgical ICU patients who required pulmonary artery catheters, except those patients with arrhythmias or history of tricuspid valve disease.

INTERVENTIONS

During the first 48 hrs after catheter insertion, hemodynamic data were obtained at least every 4 hrs. Treatment of low preload was initiated only if clinical indications were present. These indications included a mean arterial pressure of < 70 mm Hg, heart rate of > 120 beats/min, urine output of < 40 mL/hr, stroke volume of < 40 mL/m2 with oxygen delivery of < 450 mL/min/m2, and lactic acidosis. Volume infusion was considered if PAOP was < 18 mm Hg and right ventricular end-diastolic volume index was < 140 mL/m2. Treatment was given tohigh preload, defined as a PAOP of > 18 mm Hg to prevent pulmonary edema. When PAOP and right ventricular end-diastolic volume index gave conflicting information, other clinical parameters were assessed to determine treatment.

MEASUREMENTS AND MAIN RESULTS

Twenty-seven patients requiring 70 catheters were evaluated for the study. Thirteen patients with 46 pairs of data points completed the study. Fourteen patients were excluded from analysis due to irregular heart rate, poor quality of cardiac output at the time of volume infusion, or lack of major volume manipulation. PAOP and right ventricular end-diastolic volume index measurements agreed in 42 of 46 instances (PAOP of < 18 mm Hg, right ventricular end-diastolic volume index of < 140 mL/m2), leading to fluid treatment. In one instance, PAOP was > 18 mm Hg, right ventricular end-diastolic volume index was < 140 mL/m2, and the patient had normal blood pressure and good urine output. PAOP was used in this instance as a guide to diurese the patient, which led to improvement of heart rate and stroke volume index. Three measurements in two patients with high intra-abdominal pressure indicated a PAOP of > 18 mm Hg with right ventricular end-diastolic volume index of < 140 mL/m2. A rigid abdomen accompanied hypotension, tachycardia and low urine output. Thus, a fluid bolus was administered, resulting in improved blood pressure, stroke volume, and heart rate. PAOP were obtained at end-expiration. Positive end-expiratory pressure (PEEP) was removed for < 1 sec, if patients were on PEEP > or = 10 cm H2O, to avoid the effects of high intrapleural pressure on PAOP readings. Cardiac output was measured at end-expiration, and stroke volume index and right ventricular end diastolic volume index were derived.

CONCLUSIONS

In this small sample of surgical patients with sepsis, adult respiratory distress syndrome, and hemorrhagic shock (n = 13), the additional information derived from right ventricular end-diastolic volume index did not change treatment in 43 of 46 instances. However, patients with increased intra-abdominal pressures may show misleadingly high PAOP despite low preload. These patients clearly benefitted from the additional information derived from ventricular volume measurements. Additionally, clinicians who are reluctant to take off-PEEP PAOP may also find this catheter useful.