Incidence of venous and paradoxical air embolism in neurosurgical patients in the sitting position: detection by transesophageal echocardiography

BACKGROUND

Venous air embolism (VAE) and paradoxical air embolism (PAE) are serious complications associated with the sitting position for neurosurgery. Although PAE is the result of VAE, the incidence of PAE according to the severity of VAE has not been investigated systematically in humans.

METHODS

Twenty-one patients scheduled for neurosurgery in the sitting position were investigated prospectively. VAE and PAE were continuously monitored by cardiac two-dimensional 4-chamber view using transesophageal echocardiography (TEE) and the severity of VAE and PAE was quantitatively graded from 0 to 3 by the microbubbles score. Haemodynamic parameters and end-tidal CO2 concentration (PETCO2) during VAE and PAE were also recorded.

RESULTS

Microbubbles in the right atrium appeared in all patients and the number of patients involved in grades 0, 1, 2 and 3 of VAE was 0, 10, 3 and 8, respectively. PAE occurred in 3 patients and only followed grade 3 of VAE. PAE always appeared from 20 to 30 s after the most severe VAE. A reduction of PETCO2 and an increase of pulmonary artery pressure were noted during all episodes of grades 2 and 3 VAE. In contrast, a significant reduction of systemic blood pressure occurred in 1 case of grade 2 and 3 cases of grade 3.

CONCLUSIONS

VAE detected by TEE appeared in all patients undergoing neurosurgery in the sitting position and PAE only occurred following the most severe grade of VAE. To prevent growth of VAE is an important prophylactic for PAE.

[Anesthetic management for Fontan procedure without the use of cardiopulmonary bypass]

We examined the anesthetic management for Fontan procedure performed without the use of cardiopulmonary bypass (Group N, n = 7) and that for equivalent procedure under cardiopulmonary bypass (Group E, n = 10) retrospectively. In Group N, surgical repairs of major vascular system were performed while bypassing the superior or inferior vena cava to the right atrium. The use of anesthetics and vasoactive agents was similar in both groups. Patients in Group N had significantly less blood loss and were extubated significantly earlier than those in Group E. However, significant metabolic acidosis was noted in Group N when reconstruction of the vascular system was completed and so-called Fontan circulation was initiated. Fontan procedure without the use of cardiopulmonary bypass may have advantage of less impairment for the cardiac performance and the pulmonary vasculature. However, its anesthetic management is another challenge to the anesthesiologist and requires meticulous control of both optimum preload and vascular resistance of the pulmonary artery.

Incidence of venous and paradoxical air embolism in neurosurgical patients in the sitting position: detection by transesophageal echocardiography

BACKGROUND

Venous air embolism (VAE) and paradoxical air embolism (PAE) are serious complications associated with the sitting position for neurosurgery. Although PAE is the result of VAE, the incidence of PAE according to the severity of VAE has not been investigated systematically in humans.

METHODS

Twenty-one patients scheduled for neurosurgery in the sitting position were investigated prospectively. VAE and PAE were continuously monitored by cardiac two-dimensional 4-chamber view using transesophageal echocardiography (TEE) and the severity of VAE and PAE was quantitatively graded from 0 to 3 by the microbubbles score. Haemodynamic parameters and end-tidal CO2 concentration (PETCO2) during VAE and PAE were also recorded.

RESULTS

Microbubbles in the right atrium appeared in all patients and the number of patients involved in grades 0, 1, 2 and 3 of VAE was 0, 10, 3 and 8, respectively. PAE occurred in 3 patients and only followed grade 3 of VAE. PAE always appeared from 20 to 30 s after the most severe VAE. A reduction of PETCO2 and an increase of pulmonary artery pressure were noted during all episodes of grades 2 and 3 VAE. In contrast, a significant reduction of systemic blood pressure occurred in 1 case of grade 2 and 3 cases of grade 3.

CONCLUSIONS

VAE detected by TEE appeared in all patients undergoing neurosurgery in the sitting position and PAE only occurred following the most severe grade of VAE. To prevent growth of VAE is an important prophylactic for PAE.

Increased plasma adrenomedullin concentrations during cardiac surgery

1. Adrenomedullin (AM), a potent hypotensive peptide, was originally isolated from human phaeochromocytoma. Plasma AM concentrations are elevated in hypertension, heart failure and renal failure in proportion to the severity of the disease. This study was performed to investigate the pathophysiological significance of AM during cardiac surgery. 2. Serial blood samples were obtained from patients undergoing cardiac surgery and plasma AM concentrations were determined by specific radioimmunoassay. 3. Plasma AM concentrations did not increase with anaesthesia or surgery (n = 9). Plasma AM concentrations gradually increased during cardiopulmonary bypass and after pulmonary reperfusion. After pulmonary reperfusion, plasma AM concentrations increased further. In addition, we measured plasma AM concentrations in the pulmonary vein (n = 8) and coronary sinus (n = 8) to examine the contribution of the lungs and heart to the increase in circulating AM concentrations after cardiopulmonary bypass. However, no significant differences were seen in plasma AM concentrations of the pulmonary vein or the coronary sinus and the aorta. Peak AM concentrations during cardiac surgery correlated with duration of surgery. Elevated plasma AM levels during and after surgery began to decline next day after surgery and returned to normal levels 7 days after surgery. 4. These results demonstrate that plasma AM concentrations increase during cardiac surgery and that the duration of surgery may be related to the changes in AM concentrations. Taken together with recent findings that vascular endothelial cells and vascular smooth muscle cells actively produce AM, these results suggest that plasma AM during cardiac surgery may act as a vasodilatory hormone.

[Early recovery after valvular heart surgery]

There have been published not a few reports concerning the early recovery from heart surgery. But most of them were restricted in CABG cases. We report our efforts and its results about the early recovery from valvular heart surgery. To make a contribution to the early recovery we have made some efforts since 1995, including normothermic perfusion, low-dose fentanyl and introduction of terminal warm blood cardioplegia. As the results, the tracheal intubation period was shortened from 12.6 +/- 5.3 (hour) to 6.7 +/- 4.1. The number of the cases who had tracheal extubation in the operative day increased from 27% to 84%. The postoperative cardiac function was satisfactory and there were no abdominal or neurologic disturbances among the patients those who were entered into the early recovery protocol. We obtained satisfied early recovery in safe after valvular heart surgery.

[A successful perioperative anticoagulation therapy and monitoring of a patient with hereditary plasminogen abnormality undergoing aortic valve replacement]

During perioperative period, plasminogen abnormality can result in unusual or unexplained clotting that occurs spontaneously or after minor trauma. However, there has been no report on perioperative anticoagulation therapy and monitoring in patients with hereditary plasminogen abnormality undergoing cardiac surgery. We performed a successful perioperative anticoagulation therapy and monitoring of a patient with hereditary plasminogen abnormality undergoing cardiac surgery. A 48-year-old male patient with severe aortic valve stenosis, who had had no episode of thrombosis, was scheduled for aortic valve replacement Preoperative laboratory screenings detected his abnormal plasminogen activity (7.6% normal), and he was diagnosed as hereditary plasminogen abnormality. Anesthetic course was uneventful until the initiation of cardiopulmonary bypass (CPB). During CPB, heparin level was monitored every 30 minutes by Hepcon/HMS (Medtronic Hemotec, Parker, CO). No thrombus was observed in the CPB circuit. Plasminogen activity, fibrin degradation products (FDP) and D-dimer were not elevated during perioperative period. Protamine dosage was determined by protamine titration method, and protamine was administrated after the termination of CPB. No major bleeding was observed after protamine administration. When the patient was admitted to ICU, anticoagulation therapy was started immediately. During perioperative period, no episode suggesting thrombosis was observed. In conclusion, we consider that this successful anticoagulation therapy and monitoring during CPB has been achieved by use of Hepcon/HMS.

[Regional cerebral hypoperfusion reduces the effect of rectal midazolam in children with Moyamoya disease]

To investigate the effect of regional cerebral blood flow on the effect of midazolam, we evaluated 99mTc-hexamethylpropylene-amine-oxime-single photon emission computed tomography (SPECT) in 37 cases of childhood moyamoya disease. They were divided into two groups according to the findings of SPECT; one group showed hypoperfusion in the bifrontal regions (n = 20), and the other did not (n = 17). Both groups received 1 mg.kg-1 of midazolam transrectally 30 min before the anesthesia induction and level of sedation was measured with six point scales. Significantly lower level of sedation score was recognized in the group that showed hypoperfusion in bifrontal regions (P < 0.05). Our finding may suggest that regional cerebral hypoperfusion may modify the sedative effect of midazolam in children with moyamoya disease.

Resection of a large, high-flow arteriovenous malformation during hypotension and hypothermia induced by a percutaneous cardiopulmonary support system. Case report

The key to successful surgical resection of cerebral arteriovenous malformations (AVMs) is control of bleeding and cerebral swelling. Induced hypotension is one of the most valuable means of achieving this control. The authors introduced induced hypotension with mild hypothermia by using a percutaneous cardiopulmonary support system (PCPS) to resect a large, high-flow AVM. The efficacy and technical points of this method are discussed. The PCPS, whose entire intraluminal surface was coated with heparin, was established through a transfemoral route. During resection of the AVM, a mean arterial blood pressure of 60 mm Hg and a mean body temperature of 30 degrees C were easily maintained by regulating the flow rate of the PCPS and by blood cooling. The activated coagulation time was maintained at approximately 250 seconds with a minimum systemic administration of heparin. The authors report the case of a 30-year-old woman who presented with intraventricular hemorrhage and was diagnosed as having a large, high-flow AVM located in the left sylvian fissure. The AVM was fed by the left middle, posterior, and anterior cerebral arteries and drained by the many cortical ascending veins and the basal vein. The patient underwent surgery after hypotension and hypothermia had been induced via the PCPS method. Induced hypotension decreased the tension of the nidus and made its dissection easier. The AVM was totally resected and no hemostatic difficulties were encountered. On the basis of the authors' experience, they suggest that hypotension and hypothermia induced by using the PCPS is a powerful tool for the successful resection of large, high-flow AVMs.

[A case of twice catastrophic pulmonary vasoconstriction-type shock induced with protamine sulfate]

A 71-year-old female was scheduled for the re-replacement of a mechanical mitral valve. After the cardiopulmonary bypass (CPB) she was administered protamine sulfate. Subsequently mean systemic blood pressure went down below 20 mmHg and central venous pressure and mean pulmonary blood pressure were above 50 mmHg, and immediately CPB was restarted as an assist device for circulation. After the second CPB, she was administered protamine sulfate again, and the same shock occurred. At last the third CPB was restarted and the third protamine administration was not undertaken after the third CPB. Although her postoperative drainage may have been relatively much more compared with cases of neutralization of heparin, postoperative course was uneventful in this patient. Administered protamine to neutralize the anticoagulat effects of heparin may often cause temporary treatable hypotension. Although protamine may rarely cause severe pulmonary vasocontriction and anaphylactoid reactions, clinical pictures become critical once these reactions occur. It is important in these cases to identify protamine as the cause of shock and avoid repeating the shocks.

A guide to preventing deep insertion of the cannulation needle during catheterization of the internal jugular vein

OBJECTIVE

Accidental puncture of the vertebral artery during the internal jugular vein cannulation produces lethal sequelae. To prevent this, the cannulation needle must not be inserted too deeply. However, there is no useful guide for the optimal length of insertion of the needle for accessing the internal jugular vein. The authors examined the length of the needle needed to reach the internal jugular vein with three different sizes of needle (16, 20, and 23 gauge).

DESIGN

Prospective study.

SETTING

An academic medical center.

PARTICIPANTS

Patients undergoing cardiovascular surgeries.

INTERVENTIONS

The cannulation of the internal jugular vein was performed through the right internal jugular vein by the high approach. The needle was slowly advanced, keeping constant negative pressure on the syringe at 45 degrees to the skin surface until blood was aspirated; if blood was not aspirated during insertion, the needle was slowly withdrawn until blood was aspirated. The distance to the internal jugular vein was assessed by calculating the entire length of needle minus the length of needle from the skin surface to the hub.

MEASUREMENTS AND MAIN RESULTS

The mean distance to the internal jugular vein ranged from 15.0 to 21.5 mm, and the larger needle required the longer distance to the internal jugular vein.

CONCLUSIONS

The results may be a useful guide to prevent too deep insertion of the needle during internal jugular vein catheterization, especially when teaching residents who have limited experience with internal jugular vein catheterization.

[Anesthesia for pediatric open heart surgery without transfusion]

We reviewed 50 recent anesthetic managements of pediatric patients for open heart surgery weighing between 6.5 to 12 kg to evaluate factors contributing to successful management without transfusion. Twenty six cases were managed without transfusion, whereas nine cases required less than 30 ml.kg-1 of transfusion and the other 15 cases needed massive transfusion amounting to more than 50 ml.kg-1. The followings are important factors to complete the open surgery without transfusion; 1) the patient's weight is 9 kg or more, 2) the duration of cardiopulmonary bypass is less than 120 minutes, and 3) intraoperative bleeding is less than 10 ml.kg-1. We could find several advantages in patients without transfusion, compared with those receiving transfusion, such as greater urine output, less bleeding during the surgery, more concentrated platelet and better respiratory condition after the surgery. In addition, the lager the amount of transfusion we observed the more disadvantageous to the patients. Even if transfusion can not be avoided, minimal transfusion of the washed red cell is favorable.

[Brain monitoring with near infrared spectroscopy during carotid endarterectomy]

We evaluated clinical efficacy of near infrared spectroscopy (NIR) as a monitoring system for cerebral oxygenation during anesthesia for carotid artery endarterectomy. NIR proved to be affected significantly by clamping of the external carotid artery. The present study suggests that this monitoring system may be useful for evaluation of cerebral blood flow following declamping of the internal carotid artery, although it has some limitations during clamping of the artery.

[Cardiac surgery using cardiopulmonary bypass in a patient with sickle-cell trait]

The sickle-cell gene is most concentrated in West Central Africa, the northeast corner of Saudi Arabia and East Central India. Sickle cell trait is the heterozygous condition for Hb S gene. Thirty to fifty per cent of their hemoglobin is Hb S and the remainder is Hb A. The sickle-cell crisis is induced by hypoxia, hypercarbia, acidosis, low flow condition, and hypothermia, which leads to vasoocclusion. A 39-year-old black man from Burkina Faso located in West Africa with left ventricular rupture was admitted for operation using cardiopulmonary bypass (CPB). He had been diagnosed as sickle-cell trait. The Hb S concentration was 36.2 per cent before operation with hemoglobin electrophoresis. During CPB, the minimum blood temperature was 31 degrees C and an aortic cross-clamp was not done. Total CPB time was 1 hour 31 minutes. Use of vasodilator and hyperventilation was effective. No neurological sequelae were observed.

[Aortic dissection after weaning from extracorporeal circulation]

Acute aortic dissection is a rare complication of cardiac surgery. But once it happens, its outcome is often miserable. We experienced this complication after discontinuing cardiopulmonary bypass (CPB). A 56-year old man with mitral regurgitation was referred for mitral valve replacement under CPB. After weaning from extracorporeal circulation (ECC), the right radial artery pressure decreased suddenly and its waveform became flat. After 5 minutes, dissection of the ascending aorta was diagnosed by transesophageal echocardiography (TEE). We started to prevent ischemic brain damage immediately, but a severe brain damage occurred. Its early diagnosis is necessary and the prevention of critical brain damage due to low perfusion of the blood is important for anesthetic management.

[The efficacy of transesophageal echocardiography during the pericardial drainage of the cardiac tamponade after cardiac surgery]

For two cases of cardiac tamponade following cardiac surgery, the approaches for pericardial drainage were determined by the transesophageal echocardiography under general anesthesia. In most cases of cardiac tamponade after cardiac surgery the pericardial effusion is regional and localized due to adhesions of pericardium. Therefore subxiphoid incision approach of pericardial drainage cannot often be accomplished. In these cases transesophageal echocardiography can image the presence, location and size of the pericardial effusion and is an available method to determine the approach of pericardial drainage.

[Comparison of cerebral oxygen metabolism during normothermic versus moderate hypothermic cardiopulmonary bypass]

We compared the effects of normothermic (NCPB, N = 5) and moderate hypothermic (HCPB, (N = 5) cardiopulmonary bypass on cerebral oxygen metabolism in patients undergoing coronary artery bypass grafting. For monitoring of cerebral oxygenation, we used jugular venous oxyhemoglobin saturation (SjVO2) and near infrared spectroscopy (NIR). In NCPB group, although SjVO2 decreased temporally at the start of cardiopulmonary bypass, it became stabilized above 50% during the rest of cardiopulmonary bypass. In HCPB group, on the contrary, oxyhemoglobin measured by NIR showed maximum decrease during rewarming under cardiopulmonary bypass. Furthermore, SjVO2 decreased under 50% at the end of cardiopulmonary bypass (3/5 cases). We consider that NCPB is a useful technique for preventing cerebral hypoxia, if the decrease of SjVO2 during the early period of cardiopulmonary bypass is avoidable. Lastly, we also advocate that both SjVO2 and NIR are useful monitoring systems for continuous evaluation of cerebral oxygen metabolism during cardiopulmonary bypass.

[Anesthetic management for AICD (automatic implantable cardioverter defibrillator) implant surgery]

We studied anesthetic management and monitoring during AICD (automatic implantable cardioverter defibrillator) implantation. For anesthetic management, complete sedation and amnesia are needed during implantation procedures with rapid awakening and extubation after the surgery. We chose inhalation anesthesia supplemented with small doses of fentanyl or thiamylal. Monitoring for AICD implantation should be less invasive, continuous and rapid in responsiveness. For brain and cardiac monitoring, a combination of near infrared spectroscopy and transesophageal echocardiography was quite useful.

[Relationship between retained microbubbles and neuropsychologic alterations after cardiac operation]

We studied the relationship between quantity of microbubble retained in the left heart and neuropsychologic alterations after surgery in 21 patients undergoing cardiac surgery including cardiopulmonary bypass. The neuropsychologic change was evaluated by three kinds of psychological test, which mainly analyzed memory and cognition. The microbubble was continuously monitored by the long axis view of the descending aorta of transesophageal echocardiography and then quantitatively analyzed and graded by the on-line computer. More microbubbles were detected in the valve surgery requiring the intracardiac procedure than in coronary artery bypass grafting and neuropsychologic deterioration, although the relationship did not reach statistical significance. Since most of the microbubbles were detected during the unclamping of aorta and the weaning from cardiopulmonary bypass, a technical improvement of the surgical procedures could reduce them. We think that transesophageal echocardiography is useful for monitoring microbubbles during operation.

[Usefulness of monitoring with near infrared spectroscopy during retrograde cerebral perfusion]

Recently retrograde cerebral perfusion (RCP), a newly developed technique for cerebral protection during surgical replacement for thoracic aortic aneurysm, has been used in many institutes. However, there is no established monitoring methods for cerebral oxygenation during this procedure. In the present study, we examined if near infrared spectroscopy (NIR) is useful for monitoring cerebral oxygenation during RCP. We studied 7 patients undergoing operations for aneurysms of the ascending aorta and transverse arch in the supine position (Group A) and another seven patients undergoing operations for aneurysms of the transverse arch and descending aorta in the lateral decubitus position (Group D) in this study and monitored cerebral oxygenation with NIR. NIR showed a slow but continuous decrease in oxygenated hemoglobin and an increase in deoxygenated hemoglobin during RCP, while these changes disappeared following the termination of RCP. The degree of these changes in Group D was significantly greater than that in Group A. In comparison, we observed rapid reduction of oxygenated hemoglobin during the period of circulatory arrest and low perfusion pressure with NIR, suggesting the usefulness of RCP for cerebral oxygenation. NIR may be a useful method of monitoring cerebral oxygenation during RCP.

Optimal placement of CVP catheter in paediatric cardiac patients

For correct monitoring of central venous pressure (CVP) the tip of the CVP catheter should be placed in the superior vena cava (SVC). Since there is no useful guide for the optimal depth of insertion of CVP catheter in children undergoing cardiovascular surgery, we examined the relationship between the depth of the CVP catheter and easily measured body-size variables, such as age, weight and height, and then created a guide for the optimal placement of the paediatric population. The CVP catheterization was performed through the right internal jugular vein by the high approach. The position of the catheter tip was determined by the wave form of the CVP tracing and the depth of insertion was assessed by the external marking on the catheter at the cannulation site. The position of the catheter tip, determined by postoperative AP chest x-ray, was identified by the level of thoracic vertebra (T) corresponding to the position of the catheter tip. We analyzed the relationship between the depth of the catheter and patient's age, weight and height by linear regression analysis. The position of tip was normally distributed from T1 to T7 and the tips were centralized at levels of T3, T4 and T5 which anatomically correspond to SVC. The r values between the catheter depth and the three factors at each level were comparable, although the correlation between the depth of catheter and height was best. A simple guide for placement of the catheter tip at T3, T4 and T5 levels as a function of patient's height was created.(ABSTRACT TRUNCATED AT 250 WORDS)

[Anesthetic management using percutaneous cardiopulmonary support for cesarean section in a patient with severe pulmonary hypertension]

A 27-year-old female with severe pulmonary hypertension was scheduled to undergo an elective cesarean section at the 32-week gestational age. Since the preoperative assessment revealed that the patient could not tolerate the hemodynamic changes during the operation under general anesthesia without any cardiopulmonary support, the percutaneous cardiopulmonary support (PCPS) with a centrifugal pump was applied for the anesthetic management of the patient during the operation. After the induction of anesthesia, percutaneous cannulation was performed via the femoral artery and vein, and the PCPS was started with an assisted flow ranged 1.5-2.0 l.min-1. Then, the operation was performed, during which the cardiopulmonary function of the patient was well maintained with the aid of the PCPS. The operation was finished uneventfully, and the patient could successfully emerge from the PCPS immediately after the operation. The PCPS is thought to be very useful for the anesthetic management of the patients with poor cardiopulmonary tolerance.