Comparison of axillary artery or brachial artery pressure with aortic pressure after cardiopulmonary bypass using a long radial artery catheter

Hemodynamic Monitoring In The Cardiac Surgical Patient: Comparison of Three Arterial Catheters

OBJECTIVE

Systemic systolic (SAP) and mean (MAP) arterial pressure monitoring is the cornerstone in hemodynamic management of the cardiac surgical patient, and the radial artery is the most common site of catheter placement. The present study compared 3 different arterial line procedures. It is hypothesized that a 20-G 12.7- cm catheter inserted into the radial artery will be equal to a 20-G 12.7- cm angiocath placed in the brachial artery, and superior to a 20-G 5.00 cm angiocath placed in the radial artery.

DESIGN

A prospective randomized control study was performed.

SETTING

Single academic university hospital.

PARTICIPANTS

Adult patients ≥18 years old undergoing nonemergent cardiac surgery using cardiopulmonary bypass (CPB).

INTERVENTIONS

After approval by the Rhode Island Hospital institutional review board, a randomized prospective control study to evaluate 3 different peripheral intraarterial catheter systems was performed: (1) Radial Short (RS): 20-G 5- cm catheter; (2) Radial Long (RL): 20-G 12- cm catheter; and (3) Brachial Long (BL): 20-G 12- cm catheter.

MEASUREMENTS AND RESULTS

Gradients between central aortic and peripheral catheters (CA-P) were compared and analyzed before CPB and 2 and 10 minutes after separation from CPB. The placement of femoral arterial lines and administration of vasoactive medications were recorded. After exclusions, 67 BL, 61 RL, and 66 RS patients were compared. Before CPB, CA-P SAP and MAP gradients were not significant among the 3 groups. Two minutes after CPB, the CA-P SAP gradient was significant for the RS group (p = 0.005) and insignificant for BL (p = 0.47) and RL (p = 0.39). Two-group analysis revealed that CA-P SAP gradients are similar between BL and RL (p = 0.84), both of which were superior to RS (p = 0.02 and p = 0.04, respectively). At 10 minutes after CPB, the CA-P SAP gradient for RS remained significant (p = 0.004) and similar to the gradient at 2 minutes. The CA-P SAP gradients increased from 2 to 10 minutes for BL (p = 0.13) and RL (p = 0.06). Two minutes after CPB, the CA-P MAP gradients were significant for the BL (p = 0.003), RL (p < 0.0001), and RS (p < 0.0001) groups. Two-group analysis revealed that the CA-P MAP gradients were lower for the BL group compared with the RL (p = 0.054) and RS (p< 0.05) groups. Ten minutes after CPB, the CA-P MAP gradients in the RL and RS groups remained significant (p < 0.0001) and both greater than the BL group (p = 0.002). A femoral arterial line was placed more frequently in the RS group (8/66 = 12.1%) than in the RL group (3/61 = 4.9%) and the BL group (2/67 = 3.0%). Vasopressin was administered significantly more frequently in the RS group.

CONCLUSION

Regarding CA-P SAP gradients, the RL group performed equally to the BL group, both being superior to RS. Regarding CA-P MAP gradients, BL was superior to RL and RS. Clinically, femoral line placement and vasopressin administration were fewer for the BL and RL groups when compared with the RS group. This study demonstrated the benefits of a long (12.7 cm) 20- G angiocath placed in the radial artery.

Central Versus Peripheral Arterial Pressure Monitoring in Patients Undergoing Cardiac Surgery: A Prospective Observational Study

OBJECTIVE

The aortic-to-radial arterial pressure gradient is described during and after cardiopulmonary bypass (CPB), and can lead to underestimating arterial blood pressure. The authors hypothesized that central arterial pressure monitoring would be associated with lower norepinephrine requirements than radial arterial pressure monitoring during cardiac surgery.

DESIGN

An observational prospective cohort with propensity score analysis.

SETTING

At a tertiary academic hospital's operating room and intensive care unit (ICU).

PARTICIPANTS

A total of 286 consecutive adult patients undergoing cardiac surgery with CPB (central group: 109; radial group: 177) were enrolled and analyzed.

INTERVENTIONS

To explore the hemodynamic effect of the measurement site, the authors divided the cohort into 2 groups according to a femoral/axillary (central group) or radial (radial group) site of arterial pressure monitoring.

MEASUREMENT AND MAIN RESULTS

The primary outcome was the intraoperative amount of norepinephrine administered. Secondary outcomes included norepinephrine-free hours and ICU-free hours at postoperative day 2 (POD2). A logistic model with propensity score analysis was built to predict central arterial pressure monitoring use. The authors compared demographic, hemodynamic, and outcomes data before and after adjustment. Central group patients had a higher European System for Cardiac Operative Risk Evaluation. (EuroSCORE) compared to the radial group-7.9 ± 14.0 versus 3.8 ± 7.0, p < 0.001. After adjustment, both groups had similar patient EuroSCORE and arterial blood pressure levels. Intraoperative norepinephrine dose regimens were 0.10 ± 0.10 µg/kg/min in the central group and 0.11 ± 0.11 µg/kg/min in the radial group (p = 0.519). Norepinephrine-free hours at POD2 were 38 ± 17 hours versus 33 ± 19 hours in central and radial groups, respectively (p = 0.034). The ICU-free hours at POD2 were greater in the central group: 18 ± 13 hours versus 13 ± 13 hours, p = 0.008. Adverse events were less frequent in the central group than in the radial group-67% versus 50%, p = 0.007.

CONCLUSIONS

No differences in the norepinephrine dose regimen were found according to the arterial measurement site during cardiac surgery. However, norepinephrine use and length of stay in the ICU were shorter, and adverse events were decreased when central arterial pressure monitoring was used.

Non-invasive detection of a femoral-to-radial arterial pressure gradient in intensive care patients with vasoactive agents

BACKGROUND

In patient requiring vasopressors, the radial artery pressure may underestimate the true central aortic pressure leading to unnecessary interventions. When using a femoral and a radial arterial line, this femoral-to-radial arterial pressure gradient (FR-APG) can be detected. Our main objective was to assess the accuracy of non-invasive blood pressure (NIBP) measures; specifically, measuring the gradient between the NIBP obtained at the brachial artery and the radial artery pressure and calculating the non-invasive brachial-to-radial arterial pressure gradient (NIBR-APG) to detect an FR-APG. The secondary objective was to assess the prevalence of the FR-APG in a targeted sample of critically ill patients.

METHODS

Adult patients in an intensive care unit requiring vasopressors and instrumented with a femoral and a radial artery line were selected. We recorded invasive radial and femoral arterial pressure, and brachial NIBP. Measurements were repeated each hour for 2 h. A significant FR-APG (our reference standard) was defined by either a mean arterial pressure (MAP) difference of more than 10 mmHg or a systolic arterial pressure (SAP) difference of more than 25 mmHg. The diagnostic accuracy of the NIBR-APG (our index test) to detect a significant FR-APG was estimated and the prevalence of an FR-APG was measured and correlated with the NIBR-APG.

RESULTS

Eighty-one patients aged 68 [IQR 58-75] years and an SAPS2 score of 35 (SD 7) were included from which 228 measurements were obtained. A significant FR-APG occurred in 15 patients with a prevalence of 18.5% [95%CI 10.8-28.7%]. Diabetes was significantly associated with a significant FR-APG. The use of a 11 mmHg difference in MAP between the NIBP at the brachial artery and the MAP of the radial artery led to a specificity of 92% [67; 100], a sensitivity of 100% [95%CI 83; 100] and an AUC ROC of 0.93 [95%CI 0.81-0.99] to detect a significant FR-APG. SAP and MAP FR-APG correlated with SAP (r2 = 0.36; p < 0.001) and MAP (r2 = 0.34; p < 0.001) NIBR-APG.

CONCLUSION

NIBR-APG assessment can be used to detect a significant FR-APG which occur in one in every five critically ill patients requiring vasoactive agents.

Pressure difference between radial and femoral artery pressure in minimally invasive cardiac surgery using retrograde perfusion

Objective:

To investigate whether radial artery pressure is a reliable surrogate measure of central arterial pressure as approximated by femoral artery pressure in minimally invasive cardiac surgery with retrograde perfusion via femoral cannulation.

Method:

Fifty-two consecutive patients undergoing minimally invasive cardiac surgery were prospectively included in this study. Cardiopulmonary bypass was established via a femoral artery cannulation and femoral vein. Radial and femoral arterial pressures were recorded continuously, and the pressure differential between them was calculated for both systolic and mean arterial pressures. The agreement between measurements from the two arteries was compared using Bland–Altman plots. An interval of 95% limits of agreement of less than 20 mm Hg was set as satisfactory agreement.

Results:

Average age was 65 ± 14 years. With respect to systolic arterial pressure, 28 patients (54%) had a peak pressure differential between radial and femoral arteries ⩾20 mm Hg. With respect to mean arterial pressure, only five patients (9%) had a peak pressure differential ⩾20 mm Hg. The pressure differential changed with time. Pressure differential in systolic arterial pressure was 5 ± 8 mm Hg until aortic declamping, then increased to a peak of 23 ± 16 mm Hg when cardiopulmonary bypass was turned off. The femoral systolic arterial pressures were significantly greater than radial systolic arterial pressures from time of aortic declamping to 20 min after cardiopulmonary bypass. The Bland–Altman plots revealed large biases and poor agreement in this period.

Conclusion:

Radial and femoral systolic artery pressure readings can differ significantly in minimally invasive cardiac surgery with retrograde perfusion. Intraoperative arterial pressure management based solely on radial systolic arterial pressure readings should be avoided.

Risk Factors for Radial-to-Femoral Artery Pressure Gradient in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

OBJECTIVE

To identify risk factors associated with radial-to-femoral pressure gradient during cardiac surgery with cardiopulmonary bypass (CPB).

DESIGN

This is a retrospective, observational study.

SETTING

Single specialized cardiothoracic hospital in Montreal, Canada.

PARTICIPANTS

Consecutive patients that underwent heart surgery with CPB between 2005 and 2015 (n = 435).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A radial-to-femoral pressure gradient occurred in 146 patients of the 435 patients (34%). Based on the 10,000 bootstrap samples, simple logistic regression models identified the 17 most commonly significant variables across the bootstrap runs. Using these variables, a backward multiple logistic model was performed on the original sample and identified the following independent variables: body surface area (m²) (odds ratio [OR] 0.08, 95% confidence interval [CI] 0.030-0.232), clamping time (minutes) (OR 1.01, 95% CI 1.007-1.018), fluid balance (for 1 liter) (OR 0.81, 95% CI 0.669-0.976), and preoperative hypertension (OR 1.801, 95% CI 1.131-2.868).

CONCLUSION

A radial-to-femoral pressure gradient occurs in 34% of patients during cardiac surgery. Patients at risk seem to be of smaller stature, hypertensive, and undergo longer and more complex surgeries.

Needle-guided ultrasound technique for axillary artery catheter placement in critically ill patients: A case series and technique description

PURPOSE

Axillary arterial cannulation for blood pressure monitoring has been reported in adults since 1973. Reported failure rates using palpation landmarks are high. This report describes a needle-guided ultrasound technique for axillary arterial line placement in critically ill patients.

METHODS

A retrospective review of all patients requiring axillary arterial cannulation attempts with ultrasound-assisted needle guidance for hemodynamic monitoring was performed from July 2010 to June 2016 at a single institution.

RESULTS

One hundred fifty nine (159) cannulation attempts were performed in 155 patients. The overall success rate was 97%, with a first pass success rate of 84%. Inexperienced operators performed 49% of procedures under direct faculty supervision, and had a 99% success rate, which was not different from experienced operators. Almost 20% of patients had moderate-to-severe coagulopathy (platelets<50k/uL, INR>2.0 or PTT>60s). Complications reported included the following: nonfunctioning of catheter (6%) and hematoma (6%). Ischemia was noted in 2 patients (1%), but only one was attributed to the arterial catheter.

CONCLUSIONS

Use of the needle-guided ultrasound assisted approach for axillary arterial line placement is easily teachable and can be used to promote safe and successful placement of axillary arterial lines for novice learners.

Practical Suitability of a Stand-Alone Oscillometric Central Blood Pressure Monitor: A Review of the Microlife WatchBP Office Central

Accumulating evidence indicates that central blood pressure (CBP) is a better cardiovascular risk predictor than brachial blood pressure (BP). Although more additional benefits of CBP-based treatment above usual hypertension treatment are to be demonstrated, the demand for implementing CBP assessment in general clinical practice is increasing. For this, the measurement procedure must be noninvasive, easy to perform, and cost- and time-efficient. Therefore, oscillometric devices with the possibility to assess CBP seem the best option. Recently, such an oscillometric BP monitor, the Microlife WatchBP Office Central, was developed, which demonstrated its high accuracy in a validation study against invasive BP measurement. Calibration errors of this device are limited because the procedure is automated, standardized, and performed at the same place of and within 30 s from pulse wave assessment. The transformation from the peripheral pulse wave to CBP is done by means of an individual-based pulse wave analysis according to a theory of arterial compliance and wave reflections. In addition, the device has demonstrated to enable a more reliable diagnosis of hypertension by CBP than by peripheral BP, with a lower frequency of over- and underdiagnosis. Altogether, the available clinical evidence suggests that the Microlife WatchBP Office Central fulfills the criteria for general clinical use.

Risk Factors Involved in Central-to-Radial Arterial Pressure Gradient During Cardiac Surgery

BACKGROUND

A central-to-radial arterial pressure gradient may occur after cardiopulmonary bypass (CPB), which, in some patients, may last for a prolonged time after CPB. Whenever there is a pressure gradient, the radial artery pressure measure may underestimate a more centrally measured systemic pressure, which may result in a misguided therapeutic strategy. It is clinically important to identify the risk factors that may predict the appearance of a central-to-radial pressure gradient, because more central sites of measurements might then be considered to monitor systemic arterial pressure in high-risk patients. The objective of this study was to assess preoperative and intraoperative risk factors for central-to-radial pressure gradient.

METHODS

Seventy-three patients undergoing cardiac surgery using CPB were included in this prospective observational study. A significant central-to-radial arterial pressure gradient was defined as a difference of 25 mm Hg in systolic pressure or 10 mm Hg in mean arterial pressure for a minimum of 5 minutes. Preoperative data included demographics, presence of comorbidities, and medications. Intraoperative data included type of surgery, CPB and aortic clamping time, use of inotropic drugs, and vasodilators or vasopressors agents. The diameter of the radial and femoral artery was measured before the induction of anesthesia using B-mode ultrasonography.

RESULTS

Thirty-three patients developed a central-to-radial arterial pressure gradient (45%). Patients with a significant pressure gradient had a smaller weight (71.0 ± 16.9 vs 79.3 ± 17.3 kg, P = 0.041), a smaller height (162.0 ± 9.6 vs 166.3 ± 8.6 cm, P = 0.047), a smaller radial artery diameter (0.24 ± 0.03 vs 0.29 ± 0.05 cm, P < 0.001), and were at a higher risk as determined by the Parsonnet score (30.3 ± 24.9 vs 17.0 ± 10.9, P = 0.007). In addition, a longer aortic clamping time (85.8 ± 51.0 vs 64.2 ± 29.3 minutes, P = 0.036), mitral and complex surgery (P = 0.007 and P = 0.017, respectively), and administration of vasopressin (P = 0.039) were identified as potential independent predictors of a central-to-radial pressure gradient. By using multivariate logistic regression analysis, the following independent risk factors were identified: Parsonnet score (odds ratio [OR], 1.076; 95% confidence interval [CI], 1.027-1.127, P = 0.002), aortic clamping time >90 minutes (OR, 8.521; 95% CI, 1.917-37.870, P = 0.005), and patient height (OR, 0.933, 95% CI, 0.876-0.993, P = 0.029). The relative risk (RR) estimates remained statistically significant for the Parsonnet score and the aortic clamping time ≥90 minutes (RR, 1.010; 95% CI, 1.003-1.018, P = 0.009 and RR, 2.253; 95% CI, 1.475-3.443, P < 0.001 respectively) while showing a trend for patient height (RR, 0.974; 95% CI, 0.948-1.001, P = 0.058).

CONCLUSIONS

Central-to-radial gradients are common in cardiac surgery. The threshold for using a central site for blood pressure monitoring should be low in small, high-risk patients undergoing longer surgical interventions to avoid inappropriate administration of vasopressors and/or inotropic agents.

Radial mean arterial pressure reliably reflects femoral mean arterial pressure in uncomplicated pediatric cardiac surgery

OBJECTIVE

To see if radial mean arterial pressure reliably reflects femoral mean arterial pressure in uncomplicated pediatric cardiac surgery.

DESIGN

An ethics committee-approved prospective interventional study.

SETTING

Operating room of a tertiary care hospital.

PARTICIPANTS

Forty-five children aged 3 months to 4 years who underwent pediatric cardiac surgery with hypothermic cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Simultaneous femoral and radial arterial pressures were recorded at 10-minute intervals intraoperatively. A pressure gradient>5mmHg was considered to be clinically significant. The patients' mean age was 14±11 months and and mean weight was 8.0±3.0kg. A total of 1,816 simultaneous measurements of arterial pressure from the radial and femoral arteries were recorded during the pre-cardiopulmonary bypass, cardiopulmonary bypass, and post-cardiopulmonary bypass periods, including 520 (29%) systolic arterial pressures, 520 (29%) diastolic arterial pressures, and 776 (43%) mean arterial pressures. The paired mean arterial pressure measurements across the 3 periods were significantly and strongly correlated, and this was true for systolic arterial pressures and diastolic arterial pressures as well (r>0.93 and p<0.001 for all). Bland-Altman plots demonstrated good agreement between femoral and radial mean arterial pressures during the pre-cardiopulmonary bypass, cardiopulmonary bypass, and post-cardiopulmonary bypass periods. A significant radial-to-femoral pressure gradient was observed in 150 (8%) of the total 1,816 measurements. These gradients occurred most frequently between pairs of systolic arterial pressure measurements (n = 113, 22% of all systolic arterial pressures), followed by mean arterial pressure measurements (n = 28, 4% of all mean arterial pressures) and diastolic arterial pressures measurements (n = 9, 2% of all diastolic arterial pressures). These significant gradients were not sustained (ie, were not recorded at 2 or more successive time points).

CONCLUSIONS

The results suggested that radial mean arterial pressure provided an accurate estimate of central mean arterial pressure in uncomplicated pediatric cardiac surgery. There was a significant gradient between radial and femoral mean arterial pressure measurements in only 4% of the mean arterial pressure measurements, and these significant gradients were not sustained.

Peripheral arterial blood pressure monitoring adequately tracks central arterial blood pressure in critically ill patients: an observational study

INTRODUCTION

Invasive arterial blood pressure monitoring is a common practice in intensive care units (ICUs). Accuracy of invasive blood pressure monitoring is crucial in evaluating the cardiocirculatory system and adjusting drug therapy for hemodynamic support. However, the best site for catheter insertion is controversial. Lack of definitive information in critically ill patients makes it difficult to establish guidelines for daily practice in intensive care. We hypothesize that peripheral and central mean arterial blood pressures are interchangeable in critically ill patients.

METHODS

This is a prospective, observational study carried out in a surgical-medical ICU in a teaching hospital. Fifty-five critically ill patients with clinical indication of invasive arterial pressure monitoring were included in the study. No interventions were made. Simultaneous measurements were registered in central (femoral) and peripheral (radial) arteries. Bias and precision between both measurements were calculated with Bland-Altman analysis for the whole group. Bias and precision were compared between patients receiving high doses of vasoactive drugs (norepinephrine or epinephrine >0.1 microg/kg/minute or dopamine >10 microg/kg/minute) and those receiving low doses (norepinephrine or epinephrine <0.1 microg/kg/minute or dopamine <10 microg/kg/minute).

RESULTS

Central mean arterial pressure was 3 +/- 4 mmHg higher than peripheral mean arterial pressure for the whole population and there were no differences between groups (3 +/- 4 mmHg for both groups).

CONCLUSION

Measurement of mean arterial blood pressure in radial or femoral arteries is clinically interchangeable. It is not mandatory to cannulate the femoral artery, even in critically ill patients receiving high doses of vasoactive drugs.

Deep hypothermic circulatory arrest and the femoral-to-radial arterial pressure gradient

OBJECTIVES

To determine the femoral-to-radial arterial pressure gradient, as well as the factors associated with them, in patients receiving cardiopulmonary bypass (CPB) with profound hypothermia and circulatory arrest.

DESIGN

Retrospective automated hemodynamic record review.

SETTING

University hospital.

PARTICIPANTS

Patients undergoing pulmonary thromboendarterectomy with deep hypothermic circulatory arrest.

MEASUREMENTS AND MAIN RESULTS

The automated hemodynamic records of 54 consecutive patients undergoing pulmonary thromboendarterectomy with deep hypothermic circulatory arrest were reviewed, comparing the femoral and radial arterial pressures throughout the intraoperative period. In 20 of the patients, the hemodynamic data from the first 16 postoperative hours were also studied. Forty-one of 54 (76%) of the patients exhibited a mean arterial gradient of at least 10 mmHg either during or after CPB, femoral being higher. Clinically significant gradients were noted throughout the CPB period and the post-CPB period in these patients. In the 54 patients studied, the systolic blood pressure (SBP) gradient was 32 +/- 19 mmHg after CPB (95% confidence limits 28.2 mmHg, 39.0 mmHg), and the mean arterial pressure (MAP) gradient was 6.3 +/- 4.9 mmHg (95% confidence limits 5.5 mmHg, 8.6 mmHg). The duration of clinically significant SBP (>10 mmHg) and MAP (>5 mmHg) gradients in the postoperative period were 5.2 +/- 5.7 hours and 5.8 +/- 7.2 hours, respectively. Advanced age correlated with high post-CPB pressure gradients in this population and was associated with prolonged postoperative resolution of the gradients.

CONCLUSIONS

The femoral-to-radial arterial pressure gradients, particularly systolic, after CPB, were greater and of longer duration in these patients undergoing deep hypothermic circulatory arrest than gradients previously reported for routine CPB. Central arterial pressure monitoring is recommended for patients undergoing deep hypothermic circulatory arrest, being valuable both for intraoperative and postoperative care.

Radial artery pressure monitoring underestimates central arterial pressure during vasopressor therapy in critically ill surgical patients

OBJECTIVES

Radial artery pressure is known to differ from central arterial pressure in normal patients (distal pulse amplification) and in the early postcardiopulmonary bypass period. The adequacy of the radial artery as a site for blood pressure monitoring in critically ill patients receiving high-dose vasopressors has not been carefully examined.

DESIGN

Prospective observational study comparing simultaneous intra-arterial measurements of radial (peripheral) and femoral artery (central) pressures.

SETTING

Clinical investigation in a university-based surgical intensive care unit.

PATIENTS

Fourteen critically ill patients with presumed sepsis who received norepinephrine infusions at a rate of > or =5 microg/min.

INTERVENTIONS

All patients were managed in accordance with our standard practice for presumed sepsis, which consisted of intravascular volume repletion followed by vasopressor administration titrated to a mean arterial pressure of > or =60 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Systolic and mean arterial pressures were significantly higher when measured from the femoral vs. radial site (p < .005). The higher mean arterial pressures enabled an immediate reduction in norepinephrine infusions in 11 of the 14 patients. No change in cardiac output or pulmonary artery occlusion pressure was noted after dose reduction. In the two patients in whom simultaneous recordings were made after discontinuation of norepinephrine infusions, equalization of mean arterial pressures was observed.

CONCLUSIONS

Radial artery pressure underestimates central pressure in hypotensive septic patients receiving high-dose vasopressor therapy. Clinical management, based on radial pressures, may lead to excessive vasopressor administration. Awareness of this phenomena may help minimize adverse effects of these potent agents by enabling dosage reduction.

Central-to-peripheral arterial pressure gradient during cardiopulmonary bypass: relation to pre- and intra-operative data and effects of vasoactive agents

A significant central-to-peripheral arterial pressure gradient may exist during and after cardiopulmonary bypass (CPB). The etiology and mechanisms of this phenomenon remain controversial. We studied the pressure gradient between aorta, brachial artery and radial artery in 68 patients, scheduled for elective coronary artery bypass surgery. We evaluated whether choice of cardioprotection during CPB (use of cold cardioplegic solution or use of intermittent crossclamping under protection with lidoflazine), and choice of pulsatile or nonpulsatile flow during the course of CPB, affected the magnitude and duration of the systolic pressure gradient. We also studied whether central-to-peripheral pressure gradient was influenced by administration on CPB of different vasoactive drugs with different mode of action: sodium nitroprusside (direct action on the vessels), droperidol (alpha-adrenergic blocking action), ketanserin (5-hydroxytryptamine antagonist) and phenylephrine (selective alpha 1-agonist). It appeared that central-to-peripheral gradient occurred early during CPB and remained constant throughout the course of CPB. The gradient disappeared within 60 min after weaning from CPB. We found the main pressure gradient to occur between the brachial and the radial artery. There was no relation between magnitude of the gradient and sex, weight, length or age of the patient. There was also no relation between magnitude of the pressure gradient and type of cardioprotection, choice of pulsatile vs nonpulsatile flow on CPB and duration of CPB. We also found no relation between pressure gradients and changes in temperature, haematocrit and systemic vascular resistance. The pressure gradient was not affected by any of the vasoactive drugs.