The snuffbox technique: a reliable color Doppler method to assess hand circulation

Association Between Doppler Snuffbox Resistive Index and Tissue Perfusion in Septic Patients

BACKGROUND

Peripheral vascular disorders leading to tissue hypoperfusion play a central role in the pathophysiology of organ failure in septic shock. The Doppler snuffbox resistive index (SBRI) can be an accurate parameter to evaluate the status of peripheral vasculature at the bedside. We evaluated whether the SBRI is related to lactate levels or the peripheral perfusion index (PI) and its ability to predict lactate clearance in septic patients.

METHODS

We conducted a prospective observational study in a tertiary general and teaching hospital in China. From July 2019 to December 2019, all consecutive adult patients with septic shock who required intensive care unit admission were included. At the same time, 20 stable postoperative patients were studied as a control group. We recorded the hemodynamic parameters, including the SBRI and PI, which were measured simultaneously after patient recruitment.

RESULTS

We evaluated 44 patients with septic shock in the study group and 20 stable postoperative patients in the control group. Patients with septic shock had higher Sequential Organ Failure Assessment scores, procalcitonin levels, cardiac index (CI) and lactate levels than patients in the control group. The SBRI was correlated with the PI and lactate level. The CI was not correlated with lactate level in the patients examined. Based on lactate clearance in the first 6 h, the septic shock patients were divided into two groups: one with lactate clearance ≥20% (n = 28) and the other with lactate clearance <20% (n = 16). The CI was not significantly different between the two groups. The SBRI of the lactate clearance <20% group was higher than that of the lactate clearance ≥20% group and the control group. The PI of the lactate clearance <20% group was lower than that of the lactate clearance ≥20% group and the control group. The SBRI cutoff value for predicting 6-h lactate clearance after resuscitation was ≥1.09, with a sensitivity of 68.8% and a specificity of 85.7%. The PI cutoff value for predicting 6-h lactate clearance after resuscitation was ≤0.99, with a sensitivity of 64.3% and a specificity of 81.2%. The SBRI was significantly better than the PI for predicting 6-h lactate clearance after resuscitation (area under the curve: 0.805 vs. 0.703, P < 0.05).

CONCLUSIONS

The Doppler SBRI is correlated with tissue perfusion parameters in critically ill patients. An abnormal SBRI may be better than the PI for predicting poor lactate clearance in septic patients. Further investigations are required to determine whether correcting an abnormal SBRI and PI may improve the success rate of septic shock resuscitation.

Unusable radial artery for severe atherosclerosis in a young patient

We report a young diabetic patient who was found to have an unusable radial artery (RA) for coronary bypass grafting because of severe and diffuse atherosclerosis. Techniques to diagnose RA conduits, which are not usable for coronary surgery, are reviewed.

Radial artery as graft for coronary artery bypass surgery: Advantages and disadvantages for its usage focused on structural and biological characteristics

Radial artery (RA) is the most popular arterial graft after the left internal thoracic artery in both low- and high-risk patients undergoing coronary artery bypass grafting. Various arterial grafts such as the right internal thoracic artery, the right gastroepiploic artery, and the inferior epigastric artery have also gained ground over the past 30 years because of the intimal hyperplasia and atherosclerosis of the saphenous vein leading to late graft occlusion. In this review article we would like to present the utility of the RA as a graft, focused mainly on its structural and biological characteristics.

Radial artery cannulation: a comprehensive review of recent anatomic and physiologic investigations

Consistent anatomic accessibility, ease of cannulation, and a low rate of complications have made the radial artery the preferred site for arterial cannulation. Radial artery catheterization is a relatively safe procedure with an incidence of permanent ischemic complications of 0.09%. Although its anatomy in the forearm and the hand is variable, adequate collateral flow in the event of radial artery thrombosis is present in most patients. Harvesting of the radial artery as a conduit for coronary artery bypass grafting, advances in plastic and reconstructive surgery of the hand, and its use as an entry site for cardiac catheterization has provided new insight into the collateral blood flow to the hand and the impact of radial arterial instrumentation. The Modified Allen's Test has been the most frequently used method to clinically assess adequacy of ulnar artery collateral flow despite the lack of evidence that it can predict ischemic complications in the setting of radial artery occlusion. Doppler ultrasound can be used to evaluate collateral hand perfusion in an effort to stratify risk of potential ischemic injury from cannulation. Limited research has demonstrated a beneficial effect of heparinized flush solutions on arterial catheter patency but only in patients with prolonged monitoring (>24 h). Conservative management may be equally as effective as surgical intervention in treating ischemic complications resulting from radial artery cannulation. Limited clinical experience with the ultrasound-guided arterial cannulation method suggests that this technique is associated with increased success of cannulation with fewer attempts. Whether use of the latter technique is associated with a decrease in complications has not yet been verified in prospective studies. Research is needed to assess the safety of using the ulnar artery as an alternative to radial artery cannulation because the proximity and attachments of the ulnar artery to the ulnar nerve may potentially expose it to a higher risk of injury.

Hand perfusion with 99mTc-HSA in patients expecting to undergo coronary bypass surgery: elaboration of a new complex diagnostic protocol for the safe removal of a radial artery graft

BACKGROUND

The Allen test is used worldwide for radial artery graft removal. The postoperative examination of our patients' hand function and circulation proved that beside the transient neurological complications chronic hand circulatory disorders may arise.

AIM

To develop a non-invasive method suitable for an objective evaluation of the hand's circulation to make it possible to use radial arteries safely for the revascularization of coronary arteries.

METHODS

We examined 35 patients. After selective compression of the radial and ulnar arteries of both hands, we injected 400 MBq (99m)Tc-HSA intravenously and acquired 240 images, each of 1 s. After 30 s we released the ulnar artery first, and after 120 s the radial artery, too. Then computer analysis was performed.

RESULTS

The patients could be divided into two groups. In the majority of them, releasing only the ulnar artery resulted in a good circulation of the fingers. It meant that the time-activity curve rapidly reached its maximum, and the activity did not change even after releasing the radial artery. In a smaller proportion of the patients the activity of the fingers increased only slowly, and did not reach a plateau even after 30 s. Following the release of the radial artery a further increase in the activity could be observed. We assume that the latter patient group is at risk of consequent circulatory disorder of the fingers after the removal of the radial artery, whereas in the former group the artery could be removed safely.

CONCLUSIONS

Hand perfusion with (99m)Tc-HSA is useful in patients selected for coronary bypass operations, so we recommend the introduction of this method as a routine examination before the removal of the radial artery in patients with an abnormal Allen test.

Radial Artery Graft for Coronary Artery Bypass Surgery: Biological Characteristics and Clinical Outcome

The radial artery (RA) is gaining popularity as a bypass conduit for coronary artery bypass grafting, and its impact on clinical practice has been extensively explored. In the present article, we provide a review of postoperative hand circulation, vascular biological characteristics of the RA graft, the efficacy of vasodilator therapies, and mid-term clinical results of use of the RA graft. Fundamental studies revealed excellent vascular biological characteristics of the RA graft as a living arterial conduit, making it almost equivalent to the internal thoracic artery (ITA) graft. Clinical studies have yielded encouraging mid-term results. Most studies reported in favor of the RA graft over the saphenous vein graft with regard to patency rate, freedom from cardiac events, and survival. However, superiority of either the RA or right ITA graft has not been conclusively determined. The long-term results of RA grafts remain unknown, but at present, supplementary use of an RA graft with a left ITA graft appears feasible for CABG.

A novel endothelial function test using Doppler flow: the snuff-box technique

Precise measurement of Doppler estimated blood flow volume using the standard technique of flow-mediated vasodilation is not possible because the anatomic course of the brachial or radial artery goes against the principle of Doppler measurements that the insonation angle should be less than 30 degrees . The radial artery in the anatomic snuff-box area is useful for the measurement of Doppler signals as the insonation angle is less than 30 degrees and because the size of the artery allows observation of laminar flow. We introduce the snuff-box technique as a novel endothelial function test that enables measurement of both blood flow and diameter of the radial artery. Changes in diameter and blood flow volume during reactive hyperemia were examined in 15 healthy volunteers. Changes in blood flow determined using the snuff-box technique were compared with changes in forearm blood flow determined by plethysmography. The diameter of the radial artery increased from 2.3 +/- 0.2 mm at baseline to 2.8 +/- 0.4 mm at 60 s after deflation (P = 0.0017), and blood flow increased from 52.3 +/- 21.4 ml/min at baseline to 108.6 +/- 33.1 ml/min at 15 s after deflation (P = 0.0014). Percentile blood flow determined by the snuff-box technique correlated significantly with that determined by plethysmography (r = 0.824, P = 0.0002). Both blood flow volume and artery diameter can be measured with high reliability using the snuff-box technique, as has been shown in subjects with reactive hyperemia.

Preoperative Assessment of the Radial Artery for Coronary Artery Bypass Grafting: Is the Clinical Allen Test Adequate?

BACKGROUND

The clinical Allen test (AT) is widely adopted as the only preoperative assessment of the hand collateral circulation before radial artery (RA) harvest as a coronary artery bypass graft. Nevertheless, in some cases it may be misleading because of clinically undetectable anatomic anomalies of the forearm arteries.

METHODS

We evaluated the nondominant forearm arterial circulation by echo color Doppler (ECD) technique and by performing static and dynamic tests such as the AT, snuffbox test (SBT), and palmar arch test (PAT) in 150 patients who underwent elective coronary artery revascularization with a RA graft.

RESULTS

Although the clinical AT was normal in all patients, in 8 patients (5.3%) preoperative ECD AT, SBT, and PAT did contraindicate RA harvesting. We did not harvest the RA in these patients. In the remaining 142 patients the RA was harvested. We did not observe any case of postoperative forearm or hand ischemia. We examined the blood flow to the hand in all patients at both 5 days and 24 months after surgery. In all patients ECD showed adequate hand perfusion and a significant increase of the peak flow velocity in the ulnar artery at both follow-up times.

CONCLUSIONS

The clinical AT may be not sufficient to assess the hand collateral flow and the quality of the RA as a coronary artery bypass graft in at least 5% of patients. The ECD technique, performed during static and dynamic tests, does offer a safer and more objective preoperative noninvasive evaluation and it may have an important role also from the medicolegal point of view.

Novel Doppler Technique to Assess Systemic Vascular Resistance The Snuffbox Technique

BACKGROUND

To explore an alternative to the systemic vascular resistance index (SVRI) for monitoring peripheral circulation in patients in the intensive care unit (ICU), the resistive index (RI) in the upper extremity arteries was measured by using surface Doppler ultrasound.

METHODS AND RESULTS

The correlation between RI and vascular resistance was assessed in vitro using a vessel phantom in a Donovan-type mock circulation system. In addition, 15 ICU patients who had undergone open-heart surgery were studied. Mean arterial pressure, central venous pressure and cardiac output were measured 30 times at 10 min intervals after patients returned to the ICU following surgery, and the SVRI was calculated from these parameters. At the same time points, 3 parts of the upper extremity arteries (brachial artery in the cubital fossa (BA), radial artery at the wrist (RA), and radial artery at the anatomical snuffbox (SB)) were scanned by Doppler ultrasound, and the resistance index (RI) for each artery region was calculated. In vitro, RI increased with higher vascular resistance, exhibiting a significant correlation (r = 0.982, p < 0.0001). In vivo, the average incidence angles at the BA and RA were larger than 60 degrees , while that at the SB was only 11.5+/-10.8 degrees. The overall correlation between SVRI and RI for all patients was not significant for the BA or RA, but was significant for the SB (p < 0.0001). In individual patients, the correlation of SVRI with RI at the BA or RA was significant in 3 patients only, whereas significant correlation for the SB was observed in all patients. Doppler waveform analysis at the SB revealed diastolic flow reversal with increased SVRI.

CONCLUSIONS

Measurement at the SB provides an ideal ultrasound incidence angle for the measurement of blood flow velocity. Hence, RI measured in this way may serve as an indicator of peripheral vascular resistance, and may be effective for the evaluation of peripheral circulatory disturbance.