Cerebral effects in superior vena caval cannula obstruction: the role of brain monitoring

An Alternative Technique of Performing the Bidirectional Superior Cavopulmonary Connection without Cardiopulmonary Bypass

There is an increasing trend of performing the bidirectional superior cavopulmonary anastomosis or bidirectional Glenn (BDG) without cardiopulmonary bypass (CPB). However, there are concerns of neurological dysfunction due to cerebral congestion and systemic oxygen desaturation due to clamping the superior vena cava and pulmonary artery, respectively, required for the off-pump anastomosis. In this report we present our alternative technique of performing the procedure without CPB in 13 patients. This technique may be a useful alternative in a select anatomic group of patients.

Bidirectional Glenn operation without cardiopulmonary bypass: Single center experience and results

BACKGROUND

The bidirectional Glenn (BDG) shunt operation serves as temporary surgery for the treatment of single-ventricle physiology with the eventual Fontan procedure. In some cases, the procedure can be performed without the support of a cardiopulmonary bypass (CPB) machine. In this study, we present the surgical outcomes of off-pump BDG operation with the use of a temporary veno-atrial shunt to decompress the superior vena cava (SVC) during clamping time.

METHODS

A cohort of 23 patients underwent off-pump BDG operations at Cardiovascular Center, E Hospital. All patients were operated on using a veno-atrial shunt to decompress the SVC.

RESULTS

Satisfactory results with mean oxygen saturation increased from 79.6 ± 11.2% to 87.2 ± 4.7%. The SVC clamping time was 14 ± 2.4 min (ranging from 12 to 21 min). Among 23 patients, only six patients required blood transfusion, 17 patients had BDG without blood transfusion. No neurological complications or deaths occurred after the surgery, and the post-operative period was uneventful.

CONCLUSIONS

The use of veno-atrial shunts to decompress SVC during off-pump BDG operation is safe with good surgical outcomes and can avoid the deleterious effects caused by CPB. It is easily reproducible, at low cost and economically effective.

Superior Vena Cava Flow in Children With Attention Deficit Hyperactivity Disorder

OBJECTIVE

Attention deficit/hyperactivity disorder (ADHD), whose definition, diagnosis and treatment has been the subject of debate in the scientific community for a long time, is the most common neurobehavioral disorder in childhood. There are many studies on the pathophysiology of attention deficit. However, there is no study in the literature based on direct or indirect measurement of cerebral venous circulation in ADHD, and the effect of methylphenidate (MPH) treatment on cerebral venous circulation. Therefore, it was aimed to noninvasively measure superior vena cava (SVC) flow, which is an indirect indicator of cerebral venous flow, by transthoracic echocardiography in patients with ADHD.

METHODS

In the study, 44 healthy children, and 40 ADHD patients who were planned to start on osmotic-release oral system (OROS)- MPH were included. SVC flows were measured in healthy children and before and after drug therapy of ADHD patients.

RESULTS

SVC flow was found to be higher in ADHD patients compared to healthy children. A significant decrease was found in SVC flow of ADHD patients after OROS-MPH treatment. There was no decrease in SVC flow of patients who did not respond adequately to MPH treatment.

CONCLUSION

This first study of SVC flow in children with ADHD showed that ADHD was associated with increased SVC flow and MPH treatment had a reducing effect on this increased SVC flow. We believe that noninvasive, easily measurable, and reproducible SVC flow may be a new focus of interest for future comprehensive studies as a biomarker to support clinical evaluation in the diagnosis and treatment follow-up of ADHD patients.

Near-Infrared Spectroscopy in Pediatric Congenital Heart Disease

Near-infrared spectroscopy (NIRS) is widely used to monitor tissue oxygenation in the pediatric cardiac surgical population. Clinicians who use NIRS must understand the underlying measurement principles in order to interpret and use this monitoring modality appropriately. The aims of this narrative review are to provide a brief overview of NIRS technology, discuss the normative and critical values of cerebral and somatic tissue oxygen saturation and the interpretation of these values, present the clinical studies (and their limitations) of NIRS as a perioperative monitoring modality in the pediatric congenital heart disease population, and introduce the emerging and future applications of NIRS.

Human Auditory Evoked Potentials in the Assessment of Brain Function During Major Cardiovascular Surgery

Focal neurologic and intellectual deficits or memory problems are relatively frequent after cardiac surgery. These complications have been associated with cerebral hypoperfusion, embolization, and inflammation that occur during or after surgery. Auditory evoked potentials, a neurophysiologic technique that evaluates the function of neural structures from the auditory nerve to the cortex, provide useful information about the functional status of the brain during major cardiovascular procedures. Skepticism regarding the presence of artifacts or difficulty in their interpretation has outweighed considerations of its potential utility and noninvasiveness. This paper reviews the evidence of their potential applications in several aspects of the management of cardiac surgery patients. The sensitivity of auditory evoked potentials to the effects of changes in brain temperature makes them useful for monitoring cerebral hypothermia and rewarming during cardiopulmonary bypass. The close relationship between evoked potential waveforms and specific anatomic structures facilitates the assessment of the functional integrity of the central nervous system in cardiac surgery patients. This feature may also be relevant in the management of critical patients under sedation and coma or in the evaluation of their prognosis during critical care. Their objectivity, reproducibility, and relative insensitivity to learning effects make auditory evoked potentials attractive for the cognitive assessment of cardiac surgery patients. From a clinical perspective, auditory evoked potentials represent an additional window for the study of underlying cerebral processes in healthy and diseased patients. From a research standpoint, this technology offers opportunities for a better understanding of the particular cerebral deficits associated with patients who are undergoing major cardiovascular procedures.

Is venous congestion associated with reduced cerebral oxygenation and worse neurological outcome after cardiac arrest?

Background

Post-cardiac arrest (CA) patients are at risk of secondary ischemic damage in the case of suboptimal brain oxygenation during an ICU stay. We hypothesized that elevated central venous pressures (CVP) would impair cerebral perfusion and oxygenation (venous cerebral congestion). The aim of the present study was to investigate the relationship between CVP, cerebral tissue oxygen saturation (SctO₂) as assessed with near-infrared spectroscopy (NIRS) and outcome in post-CA patients.

Methods

This was an observational study in 48 post-CA patients with continuous CVP and SctO₂ monitoring during therapeutic hypothermia.

Results

The relationship between CVP and mean SctO₂ was best described by an S-shaped, third-degree polynomial regression curve (SctO₂ = −0.002 × CVP³ + 0.08 × CVP² – 1.07 × CVP + 69.78 %, R² 0.89, n = 1,949,108 data points) with high CVP (>20 mmHg) being associated with cerebral desaturation. Multivariate linear regression revealed CVP to be a more important determinant of SctO₂ than mean arterial pressure (MAP) without important interaction between both (SctO₂ = 0.01 × MAP – 0.20 × CVP + 0.001 × MAP × CVP + 65.55 %). CVP and cardiac output were independent determinants of SctO₂ with some interaction between both (SctO₂ = 1.86 × CO – 0.09 × CVP – 0.05 × CO × CVP + 60.04 %). Logistic regression revealed that a higher percentage of time with CVP above 5 mmHg was associated with lower chance of survival with a good neurological outcome (cerebral performance category (CPC) 1–2) at 180 days (OR 0.96, 95 % CI 0.92–1.00, p = 0.04). In a multivariate model, the negative association between CVP and outcome persisted after correction for hemodynamic variables, including ejection fraction and MAP.

Conclusions

Elevated CVP results in lower brain saturation and is associated with worse outcome in post-CA patients. This pilot study provides support that venous cerebral congestion as indicated by high CVP may be detrimental for post-CA patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1297-2) contains supplementary material, which is available to authorized users.

Experimental treatment of superior venous congestion during cardiopulmonary bypass

OBJECTIVES

Superior venous outflow obstruction affects cerebral perfusion negatively by reducing cerebral perfusion pressure (CPP). We present a randomized study designed to compare two alternative strategies to preserve the CPP during superior vena cava (SVC) congestion and cardiopulmonary bypass (CPB).

METHODS

Fourteen pigs on bi-caval CPB were subjected to 75% occlusion of the SVC flow. CPP was restored either by vasopressor treatment (VP, n = 7) or by partial relief (PR) of the congestion (n = 7). The cerebral effects of the interventions were studied for 60 min with intracranial pressure (ICP) monitoring, cerebral blood flow measurement, the near-infrared light spectroscopy tissue oxygen saturation index (StO2), arterial and venous blood gas analyses and serial measurements of the glial cell damage marker protein S100β.

RESULTS

Both strategies restored the CPP to baseline levels and no signs of severe ischaemia were observed. In the PR group, the venous and ICPs were normalized in response to the intervention, while in the VP group those parameters remained elevated throughout the experiment. The haemoglobin oxygen saturation in the sagittal sinus (SsagO2) was increased by both VP and PR, while significant improvement in the StO2 was observed only in the PR group. The S100β concentrations were similar in the two groups.

CONCLUSIONS

Experimental SVC obstruction during CPB may reduce the CPP, resulting in impaired cerebral perfusion. Both vasopressor treatment and improved venous drainage can, in the short term, individually restore the CPP during these circumstances.

Cavopulmonary anastomosis without cardiopulmonary bypass

OBJECTIVES

There is an increasing trend to perform the bidirectional superior cavopulmonary (Glenn) anastomosis without cardiopulmonary bypass. In this report, we present our results of off-pump bidirectional Glenn operation done without using a venoatrial shunt to decompress the superior vena cava during clamping. [corrected].

METHODS

A prospective, non-randomized comparative study was conducted in 50 patients with functional single ventricle anomalies who underwent bidirectional Glenn anastomosis without cardiopulmonary bypass. The patients were divided into two groups: Group I (n = 25), where it was done without a veno-atrial shunt, and Group II (n = 25), where it was done with a veno-atrial shunt. Two patients in Group I and 4 patients in Group II had a bilateral bidirectional Glenn shunt. Five patients in Group I and three patients in Group II had a previous left modified Blalock-Taussig shunt. All patients underwent a complete neurological examination both preoperatively as well as postoperatively.

RESULTS

The early hospital mortality was 4% (2/50), one in each group. The median follow-up was 14 months. The mean internal venous pressure on clamping the superior vena cava was 37.07 ± 7.12 mmHg in Group I and 24 ± 4.4 mmHg in Group II. The mean clamp time was 9.85 ± 3.52 min in Group I and 21.3 ± 4.4 min in Group II. The transcranial pressure gradient was 62.37 ± 15.01 mmHg in Group I, while 65.08 ± 13.89 in Group II. The mean intensive care unit stay was 2.57 ± 75 days in Group I, 3.3 ± 1.09 in Group II. There were no major neurological complications apart from treatable convulsions in one case in Group I (4%), 2 cases in Group II (8%), and delayed recovery in one case (4%) in Group I.

CONCLUSIONS

Off-pump bidirectional Glenn operation without caval decompression is a safe, simple and more economic procedure.

Multimodality Neuromonitoring for Pediatric Cardiac Surgery

Brain injury remains a source of morbidity associated with congenital heart surgery. Intraoperative neuromonitoring is used by many centers to help minimize neurologic injury and improve outcomes. Neuromonitoring at our institution is performed using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, electroencephalography, and somatosensory evoked potentials. Adverse or concerning parameters instigate attempts at corrective intervention. A review of the literature regarding neuromonitoring studies in pediatric cardiac surgery shows that evidence is limited to demonstrate that intraoperative neuromonitoring is associated with improved neurologic outcomes. Further clinical research is needed to assess the utility and cost-effectiveness of intraoperative neuromonitoring for pediatric heart surgery.

Veno-venous shunt-assisted cavopulmonary anastomosis

OBJECTIVE

The bidirectional Glenn shunt is commonly performed under cardiopulmonary bypass for conditions that lead to a single ventricle repair. We report our experience of bidirectional Glenn shunt done without cardiopulmonary bypass.

METHODS

Between June 2007 and May 2009, 186 consecutive patients underwent off-pump bidirectional Glenn shunt for a variety of complex cyanotic congenital heart defects. Age ranged from four months to six years and the median weight was 11.17 kg (range 4.3 - 18). After systemic heparinization, the procedure was done by creating a temporary shunt between the innominate vein and the right atrium connected across a three way connector for de-airing. Fifty one patients had bilateral cavae. All cases underwent complete clinical neurological examination.

RESULTS

No case required conversion onto cardiopulmonary bypass. Four patients (2.14%) died in the immediate postoperative period. The mean internal jugular venous pressure on clamping the decompressed superior vena cava was 24.69 +/- 1.81 mm Hg. There was no intra-operative hemodynamic instability and oxygen saturation was maintained at more than 70% throughout. Post Glenn shunt, the saturations improved to mid 80s. Seventy four cases had documented forward flow across the pulmonary valve. The mean duration of ventilation was 10.17 +/- 8.96 hours and there were no neurological complications. Six patients (3.22%) developed pleural effusions, 4 patients (2.15%) had nodal rhythm and 9 patients (4.83%) had superficial sternal wound infection.

CONCLUSIONS

Our results show that off-pump bidirectional Glenn shunt can be done safely in patients not requiring associated intra-cardiac correction. It avoids cardiopulmonary bypass and its related complications, is economical and associated with excellent results. In our opinion, this is the largest series of off-pump bidirectional Glenn shunt in the literature.

Venoatrial Shunt-Assisted Cavopulmonary Anastomosis

The bidirectional Glenn shunt operation is conventionally performed under cardiopulmonary bypass. Between June 2007 and September 2009, 218 consecutive patients underwent off-pump bidirectional Glenn shunt institution for single ventricle with pulmonary stenosis complex. Their mean age was 4.72 ± 1.80 years (range, 4 months to 6 years) and median weight was 10.12 kg (range, 4.1–19 kg). A temporary shunt was created between the innominate vein and the right atrium, with a 3-way connector for de-airing. Fifty-five patients had bilateral cavae. The mean internal jugular venous pressure on clamping the superior vena cava was 24.69 ± 1.81 mm Hg. Continuous end-tidal CO2 and O2 saturation were monitored. Adequate oxygen saturation and blood pressure were maintained by optimizing inotropics, volume, and inspired oxygen. The mean duration of ventilation was 10.17 ± 8.96 h (range, 1–73 h). There were no gross neurological complications. Postoperative pleural effusion developed in 6 (2.75%) patients, and 4 (1.83%) had nodal rhythm. Four (1.83%) patients died in the immediate postoperative period due to low cardiac output syndrome. Venoatrial shunt-assisted bidirectional Glenn shunt surgery can be performed safely by optimizing intraoperative management strategies. It is economical and avoids the deleterious effects cardiopulmonary bypass.

Results with continuous cardiopulmonary bypass for the bidirectional cavopulmonary anastomosis

OBJECTIVE

Some centres have proposed creating the bidirectional cavopulmonary anastomosis without cardiopulmonary bypass, while others continue to use deep hypothermic circulatory arrest. The purpose of this review is to evaluate the results of using continuous cardiopulmonary bypass with moderate hypothermia, perhaps the most commonly used of the three techniques for this procedure.

METHODS

Between 1990 and 2005, 114 patients, having a mean age of 1.58 years, with a median age of 8 months, and ranging from 3 months to 16 years, underwent creation of either a unilateral cavopulmonary anastomosis, in 94 cases, or bilateral anastomoses in 20 cases. All had continuous cardiopulmonary bypass with moderate hypothermia at 32 degrees Celsius, with 24 also having aortic cross-clamping with cardioplegia for simultaneous intracardiac procedures. Interrupted absorbable sutures were used to create the anastomosis in 105 patients.

RESULTS

Perioperative mortality was 5%, with 6 of the patients dying. The mean period of cardiopulmonary bypass for an isolated anastomosis was 91 minutes, with a range from 44 to 160 minutes. In 10 patients (8.8%), it was necessary to place a graft to augment the anastomosis. The average postoperative length of stay was 7.9 days for those undergoing an isolated unilateral anastomosis, and 16.4 days for patients undergoing combined cardiac operations. We have now created the Fontan circulation in 79 of the patients, at an average interval from the bidirectional cavopulmonary anastomosis of 2.1 plus or minus 1.14 years. In 76 patients, we performed postoperative angiograms, and none revealed any stenoses.

CONCLUSIONS

The bidirectional cavopulmonary anastomosis can be performed successfully with continuous cardiopulmonary bypass and moderate hypothermia with a beating heart, avoiding circulatory arrest. The use of interrupted and absorbable sutures was not associated with any late anastomotic stenosis.

Recent Advances in Application of Cerebral Oximetry in Adult Cardiovascular Surgery

Cerebral oximetry is a noninvasive technology that continuously monitors cerebral tissue oxygen saturation, which is a sensitive index of global cerebral hypoperfusion. On the basis of near-infrared spectroscopy technology, information is provided on the availability of oxygen in brain tissue at risk during numerous pathological conditions. Complementary to the arterial oxygen saturation measured by pulse oximetry, cerebral tissue oxygen saturation reflects regional cerebral metabolism and the balance of local cerebral oxygen supply/demand. Recently, patient management with the guidance of cerebral oximetry has resulted in improved patient outcomes. This review will briefly describe the physics behind cerebral oximetry and will provide an overview of the literature focusing primarily on articles published within the past 5 years.

New developments in pediatric cardiac anesthesia

As the practice of pediatric cardiac anesthesia continues to grow, anesthesiologists now routinely care for patients ranging in size from less than 2 kg to more than 100 kg. New clinical and laboratory research has enhanced our understanding of the effects of anesthetic drugs on the pediatric myocardium, and improvements in survival statistics for even the smallest and sickest infants have shifted the emphasis to evaluation of quality of life and neurological outcome in pediatric cardiac patients. The use of circulatory support in infants and children, both for rapid resuscitation and for more chronic indications such as bridge to transplantation, also continues to evolve, with the recent introduction of pulsatile and axial pumps for pediatric use. This article reviews anesthetic agents, bleeding and coagulation, neurological monitoring, and mechanical circulatory support in the treatment of infants and children.

Neurological Monitoring for Congenital Heart Surgery

The incidence of neurological complications after pediatric cardiac surgery ranges from 2% to 25%. The causes are multifactorial and include preoperative brain malformations, perioperative hypoxemia and low cardiac output states, sequelae of cardiopulmonary bypass, and deep hypothermic circulatory arrest. Neurological monitoring devices are readily available and the anesthesiologist can now monitor the brain during pediatric cardiac surgery. In this review we discuss near-infrared cerebral oximetry, transcranial Doppler ultrasound, and electroencephalographic monitors for use during congenital heart surgery. After review of the basic principles of each monitoring modality, we discuss their uses during pediatric heart surgery. We present evidence that multimodal neurological monitoring in conjunction with a treatment algorithm may improve neurological outcome for patients undergoing congenital heart surgery and present one such algorithm.

Bidirectional Glenn procedure without cardiopulmonary bypass

BACKGROUND

Whether the bidirectional Glenn procedure is better performed without the support of cardiopulmonary bypass is still a matter for debate. In this paper we discuss the indications and methods for bidirectional Glenn shunt without cardiopulmonary bypass.

METHODS

Twenty patients with complex cyanotic congenital heart defects underwent a bidirectional Glenn shunt without cardiopulmonary bypass between May 2000 and August 2002. There were 10 male and 10 female patients, the mean age was 2.7 +/- 2.6 years (range, 3 months to 11 years), and the mean weight was 11.0 +/- 6.0 kg (range, 4.5 to 32 kg). The mean transcutaneous oxygen saturation was 74.3% +/- 5.7% before the operation. The Glenn shunt was performed under venoatrial or venopulmonary shunt.

RESULTS

All patients survived. Mean superior vena cava clamping time was 24.3 +/- 4.7 minutes, and mean vena cava pressure was 26.9 +/- 5.5 mm Hg during clamping. There were no postoperative neurologic complications. Follow-up echocardiography showed functioning Glenn shunts without any obstruction at the anastomosis.

CONCLUSIONS

The adverse effects of cardiopulmonary bypass could be eliminated by this method. This is an advantage during the postoperative recovery, but patients should be strictly chosen.

Peri-operative comparison of different transient external shunt techniques in bidirectional cavo-pulmonary shunt

OBJECTIVE

In patients with functional single ventricular physiology, the avoidance of cardiopulmonary bypass offers many advantages including earlier extubation, decreased necessity of inotropic support, improved hemodynamical status and reduced likelihood of post-operative prolonged pleural effusion. We believe that the bidirectional cavopulmonary anastomosis operations may be performed with transient external shunt techniques. The purpose of this prospective study is the peri- and post-operative comparison of different transient external shunt methods used in bidirectional cavopulmonary shunt operations.

METHODS

Between years 1997 and 2000, 30 patients have undergone bidirectional cavo-pulmonary shunt operation by using three different types of external shunt. The mean patient age was 13 months (range, 3 months-3 years). Previous operations had been performed in ten patients (33%). All patients were divided into three groups according to type of external shunt used. In group A (ten patients), the transient external shunt was constructed between superior vena cava and right atrium by uniting two standard venous cannulas with a Y-connector. In group B (ten patients), the external shunt was performed with a single short venous cannula constructed between superior vena cava and right atrium. In group C (ten patients), the external shunt was constructed between superior vena cava and left pulmonary artery by using a single short venous cannula. During operation, central venous pressure (CVP), arterial O(2) saturation and mean arterial blood pressure were recorded continuously.

RESULTS

All operations are completed without the establishment of cardiopulmonary bypass. Hospital mortality was 3.3%. One patient in group A died because of low cardiac output at the end of postoperative day 2. All patients were extubated within 4h. In groups A-C mean superior vena caval pressures were measured 28, 24 and 21 mmHg, respectively during superior vena cava-right pulmonary artery anastomosis. In both groups A and B patients, arterial O(2) saturation decreased to a minimum 53+/-2 and 53+/-2%, respectively during the operation. In the group C, minimum arterial O(2) saturation was measured 82+/-2%. Although mean arterial pressure decreased in all groups during clampage; in group C patients, this drop is not significant.

CONCLUSION

Based on the study presented here, bidirectional cavo-pulmonary anastomosis can be carried out by using different types of transient external shunt. The best hemodynamical condition and arterial O(2) levels were achieved with the shunt constructed between superior vena cava and left pulmonary artery.

Cerebral vascular effects of aortovenous cannulations for pediatric cardiopulmonary bypass

BACKGROUND

The effects of aortovenous cannulations for pediatric cardiopulmonary bypass on cerebral blood flow velocity (CBFV) and electroencephalography (EEG) were evaluated.

METHODS

CBFV and EEG were continuously recorded before (baseline), during, and after cannulations until initiation of cooling (mean +/- 95% confidence interval). Vasopressors and/or volume replacement were administered if mean arterial pressure (MAP) decreased below 35 mm Hg. Cannulation-related EEG slowing was used as a criterion for electrocortical alteration.

RESULTS

We studied 124 children (3 days to 17 years of age). Aortic and venous cannulations decreased mean CBFV by 10+/-3% and 13+/-4%, respectively, from baseline (p < 0.001). MAP diminished (p < 0.01) by 8+/-3% and 12+/-4%, respectively, from precannulation values (53+/-2 mm Hg). Right atrial cannulation, which was often chosen because the patient was hemodynamically unstable, was more frequently associated with pharmacologic intervention when compared with superior vena cava (SVC) cannulation (p < 0.01). Transient EEG alterations (n = 20) were associated with persistently low MAP (< 30 mm Hg), low CBFV (< 69%), and aortic (n = 4) or SVC (n = 7) cannula malposition. Infants with right atrial cannulation and intervention had more frequent EEG alterations (p = 0.04). Patients requiring intervention were younger (p < 0.01) and had longer hospital stay (p < 0.01) than those without intervention.

CONCLUSIONS

Cerebral effects of cannulations are greater in young infants. This was found to be associated with low MAP during heart manipulation or consequence of cannula malpositions.

Cerebral blood flow velocity during occlusive manipulation of patent ductus arteriosus in children

Patent ductus arteriosus (PDA) with left-to-right shunting modifies the Doppler flow pattern of the intracranial circulation. The ability of increases in cerebral blood flow velocity (CBFV) to predict shunt resolution during PDA occlusion was evaluated. A 2 MHz transcranial Doppler (TCD) monitored diastolic and mean CBFV, plus the systolic/mean CBFV ratio in the middle cerebral artery from before (baseline) to immediately after PDA occlusion. Shunt resolution was verified by echocardiography and/or angiography. A minimum of 40% increase in diastolic-CBFV from baseline was considered successful resolution. Patients were age-stratified into group I (< 15 months; n = 23) and group II (> 15 months; n = 10). Thirty-three children were studied (age, 0.1 to 109 months) during surgical (n = 22) or coil occlusions (n = 11). Transcranial Doppler successfully identified shunt resolution in 78% of cases in group I, as compared to 0% in group II (p < 0.01). Identification rate decreased from 79% in cases of minimum ductal diameter of 3 mm (n = 19) to 21% in smaller ductuses (n = 14) (p < 0.01). Body weight and left-atrium size (p = 0.004) in group I and PDA diameter in group II (p = 0.02), were the only preoperative ductal parameters associated with diastolic-CBFV changes after ductus occlusion. Transcranial Doppler detects shunt resolution in infants with moderate to large PDAs.