Venous air embolism during operative hysteroscopy

The world literature, including hospital and medicolegal case records, was reviewed to collate cases of venous air embolism resulting from the increasing number of operative hysteroscopies being performed. Seven women undergoing operative hysteroscopy for five different indications had clear-cut evidence of venous air embolism early in the course of the procedure. Five of these patients died. This complication is rare but devastating, resulting from traumatic opening into large uterine sinuses, especially with the patient in the Trendelenburg position, when the heart is below the level of the uterus. Several steps can be taken to try to prevent this problem.

Intracardiac air clearing in valvular surgery guided by transesophageal echocardiography

BACKGROUND AND AIMS OF THE STUDY

Air embolism during open heart surgery seems to be a common occurrence and may be responsible for neuropsychological deficit or myocardial damage.

MATERIAL AND METHODS

Forty-two consecutive patients undergoing valvular surgery were studied using the long axis view of the heart by two dimensional transesophageal echocardiography (TEE). The patients were randomized into two groups of 21 each. In group 1, the routine air evacuation method was used. In group 2, the same air evacuation method was used and controlled with a Doppler ultrasonic probe adjusted around the root of the aorta. At the end of air evacuation, intracardiac microbubbles and retained air were analyzed with TEE and when air was founded, its location was communicated to the surgeons who tried to remove it by shaking the heart and tilting the operating table for 15 minutes. The patients were assessed for detection of cardiac or neurological postoperative complications.

RESULTS

The incidences of microbubbles and retained air were 57% and 43% in group 1, and 62% and 38% in group 2 respectively (ns). The mean grade of microbubbles was lower in group 2: 1.4 +/- 0.8 vs. 2.2 +/- 0.9, p < 0.05. TEE allowed to significantly decrease (p < 0.05) retained air and mean grade of microbubbles to 14% and 1.3 +/- 0.8 in group 1, and to 10% and 0.8 +/- 0.8 in group 2, without statistical difference between the two groups. Despite the help of TEE, manual attempts to eradicate retained air were unsuccessful in five patients (three in group 1, two in group 2).

CONCLUSIONS

The use of aortic ultrasonic probe allowed to reduce the amount of microbubbles. TEE was a useful tool not only for the detection of retained air but also for locating it, and guiding the procedure to eliminate it.

Outcome of tunneled hemodialysis catheters placed by radiologists

PURPOSE

To compare the outcomes of hemodialysis catheters placed by interventional radiologists with those placed by surgeons.

MATERIALS AND METHODS

The outcomes were retrospectively analyzed of 237 hemodialysis catheters placed in 140 patients by a radiology service from January 1991 through December 1992. Follow-up data were available for 222 catheters (94%). Catheter secondary patency and freedom from infection were analyzed statistically and by means of life-table analysis.

RESULTS

Pneumothorax occurred after the placement of six catheters (2.5%); in two patients, a chest tube was required for decompression. Other short-term complications included air embolism with no clinical sequelae (two procedures) and prolonged oozing from the tunnel (two procedures). Long-term complications included infection and catheter failure. Infection occurred in 26 patients (18%) with 32 catheters (14%) and resulted in removal of 25 catheters. Ninety-three catheters (42%) failed, and 63 catheters (28%) were removed because of failure.

CONCLUSION

Hemodialysis catheters placed by radiologists do not have a higher rate of complications or failure than catheters placed by surgeons.

Lymphatic air embolism: a new hypothesis regarding the pathogenesis of neonatal systemic air embolism

Objective. Neonatal systemic air embolism (NSAE) has been thought to result from introduction of air into the pulmonary veins through hypothesized alveolar-capillary fistula. The objective of this paper is to reassess the distribution of intravascular air visualized radiographically in this entity. Based on these data, an alternative theory for the pathogenesis of NSAE is proposed. Materials and methods. Four cases from our institutions and 21 additional reviewable published radiographs of NSAE were evaluated for the presence and location of intravascular air. Nonparametric statistical analysis was performed to determine if the predominance of intravascular air was venous or arterial in location, and to determine the presence or absence of pulmonary interstitial emphysema (PIE), pneumothorax, pneumomediastinum, and pneumopericardium. Results. Isolated systemic venous air was present significantly more often than isolated systemic arterial air (p < 0.0005). In addition, the presence of isolated right-sided cardiac air was found significantly more often than air within left heart chambers alone (p < 0.0005). PIE in patients with NSAE was found to be statistically more prevalent than pneumomediastinum or pneumopericardium, though similar in prevalence to pneumothorax. Conclusion. Our data support the hypothesis that intravascular air in NSAE is predominantly venous in location. PIE was found to be a very common associated finding in NSAE. Based on our current knowledge of pulmonary lymphatics, radiographic anatomy, and the lymphatic location of PIE, we propose that air within the pulmonary lymphatic system (PIE) gains access to the systemic venous system via lymphatic ducts, which results in the clinical entity NSAE. This readily explains the venous predominance of air in NSAE.

Venous gas embolism during cryosurgery for bone tumors

Cryosurgery using liquid nitrogen is a method for treating benign- and low-malignant skeletal tumors. The advantage of preserving the supportive function of bone should be compared to the risk for its complications; postoperative fracture is well known, but less so the occurrence of intraoperative venous gas embolism. This paper describes 17 patients: 2 patients who had serious hemodynamic complications during cryosurgery and a study of 15 patients in whom end-tidal N2 tension was measured in an attempt to investigate the clinical incidence of venous gas embolism during cryosurgery. In the 15 cases analyzed, we did not detect any exhaled N2 during cryosurgery.

Epidural air injection assessed by transesophageal echocardiography

BACKGROUND AND OBJECTIVES

The object of this study, using transesophageal echocardiography (TEE) in anesthetized patients, was to investigate the occurrence of venous air embolism (VAE) when air is injected into the epidural space.

METHODS

Six patients between the ages of 18 and 50 years (ASA I-II) undergoing general anesthesia in a supine position for nonthoracic surgical procedures were studied. Prior to general anesthesia, an epidural catheter was placed into the epidural space using a Tuohy needle and a standard saline loss-of-resistance technique. Following verification of proper catheter placement, general anesthesia was induced and the trachea intubated. Thereafter, a TEE probe was inserted into the esophagus. After a 10-minute control period, and during continuous TEE videotape recording, 5 mL of air was rapidly injected into the epidural space through the epidural catheter. This was followed 10 minutes later by the epidural injection of 5 mL of room-temperature preservative-free saline. Microbubble echo targets were quantified in a range from 0 to 4+.

RESULTS

Venous air microbubble emboli appeared in the circulation within 15 seconds after injecting either air or saline into the epidural space.

CONCLUSIONS

No evidence of clinically significant VAE was seen in any patient. The results suggest that drugs injected into the epidural space may have unexpectedly easy access to the venous circulation with a potential to produce unwanted systemic effects. Clinicians should be alert to the possibility that local anesthetics, or any other drug placed epidurally, may rapidly enter the systemic circulation even without the intravenous placement of an epidural catheter.

Hepatic interstitial laser photocoagulation: demonstration and possible clinical importance of intravascular gas

PURPOSE

To investigate gas formation during hepatic interstitial laser photocoagulation (ILP).

MATERIALS AND METHODS

In vitro, ILP was performed with a neodymium yttrium aluminum garnet laser on a piece of liver in a water bath. In vivo, nine pigs underwent 24 ultrasound (US)-monitored ILP procedures. Fiber tips were more than 1 cm from (n = 16) or adjacent to (n = 8) intrahepatic veins. The gas production seen on US images was graded on a scale of 0 to 4. Precordial Doppler US was performed in all cases.

RESULTS

In vitro, smoke bubbles emanated from the vessels during ILP. In vivo, US showed intravascular gas production during nine of 15 exposures of at least 500 seconds duration. Gas production scores of 2 or more were recorded for nine exposures. Intracardiac gas was identified on eight precordial Doppler US recordings. All animals survived.

CONCLUSION

Gas was detected in the heart during some ILP exposures. Patients with a probe-patent foramen ovale (24% prevalence) could be at risk for paradoxic air embolus during ILP.

Epidemiology of decompression sickness under simulated space extravehicular activities

Several ground-based trials were conducted by NASA at the Lyndon B. Johnson Space Center, Houston, TX, during 1982-90 to examine the risk of altitude decompression sickness (DCS) during space extravehicular activities. There were 22 different pressure profiles involving single and staged decompression procedures, each lasting from 180 to 360 min at the final altitude. A total of 164 healthy subjects participated in 426 exposures to altitude. Symptoms of DCS occurred in 17% (74/426) and circulating microbubbles by precordial Doppler ultrasound were detected in 42% (179/426) of all exposures. About 27% (20/74) of exposures with symptoms resulted in test abort, and one-third of all test aborts required treatment in the hyperbaric chamber. There was about 3.20 times (95% Confidence Interval [95% CI] = 1.56-6.66) higher risk of symptoms in the presence of Doppler-detectable microbubbles. Examination of individual risk factors showed that there was about 4.3 times (95% CI = 1.62-11.50) higher risk of symptoms with increasing number of exposures. These findings emphasize the importance of evaluating risk factors from ground-based trials for application in operational decision-making and treatment strategies.

Venous air embolism during cesarean section: more common than previously thought

To confirm the incidence of venous air embolism (VAE), we simultaneously monitored expired nitrogen concentration (FEN2) and precordial Doppler in 30 patients undergoing cesarean delivery during general anesthesia. Patients were randomized into two groups and the effect of a 10 degrees reverse Trendelenburg tilt versus the horizontal position was evaluated. Forty-two episodes of VAE, defined by an increase in FEN2 of 0.1%, were detected in 97% (29/30) of patients. Doppler ultrasound failed to detect 9 of the episodes and 23 (41%) changes in Doppler tones were not associated with an increase in FEN2. These spurious Doppler signals were synchronous with compression of retroperitoneal structures, suggesting turbulent venous return to be the cause. The reverse Trendelenburg position did not reduce the incidence of VAE. Compared with the preinduction baseline, mean arterial blood pressure decreased by 31.5 +/- 10.1 mm Hg in this position and 22.6 +/- 13.4 mm Hg in the supine position after hysterotomy. We conclude that VAE in cesarean delivery during general anesthesia occurs very frequently, and that changes in Doppler tones may not be reliable indicators of this complication. Measures to reduce the size and effect of air emboli therefore should be applied routinely in all patients.

Retained intracardiac air in open heart operations examined by transesophageal echocardiography

Using transesophageal echocardiography during open heart operations, we found another form of retained intracardiac air, "pooled air," in addition to the form of "bubbles" that had been reported by other authors. The pooled air was detected in all of 13 patients (100%); it was located at the right upper pulmonary vein in 13 (100%), left ventricular apex in 9 (69.2%), left atrium in 8 (61.5%), right coronary sinus of Valsalva in 8 (61.5%), left atrial appendage in 4 (30.8%), and left upper pulmonary vein in 3 (23.1%). The pooled air was found also in the pulmonary artery in 6 of 8 patients (75.0%) in whom the pulmonary artery was clearly visualized. In 1 patient, 5 mL of air was aspirated from the left ventricular apex, followed by a reduced size of the air on the transesophageal echocardiographic image. Because intracardiac air rapidly changes its locations and appearances, continuous monitoring is important, especially at weaning from bypass. The long-axis view of the heart is useful not only for detecting and locating the air, but also for guiding and evaluating the procedures to remove air.

[The detection of gas embolisms in neurosurgery caused by joint monitoring with capnography and the Swan-Ganz probe. (Apropos of 7 patients operated on in the sitting position]

The aim of this study was to detect per-operative venous gas embolism in neurosurgery using capnography coupled to the Swan-Ganz catheter method. Using both methods, our study, carried out on seven patients operated in the sitting position, showed an occurrence of air embolism in four cases. The diagnosis of air embolism was made on a rapid and progressive drop of FECO2 with, at the same time, a rise of the pulmonary arterial pressure.

ST segment depression during labor and delivery

ECG changes suggestive of myocardial ischemia are common during cesarean delivery under regional anesthesia. To determine the time course, duration, and significance of these ECG changes, we monitored 111 parturients with continuous ambulatory ECG (Holter) during and after cesarean delivery. Twenty-two parturients undergoing vaginal delivery were similarly monitored. ST segment depression was present in 25% of patients undergoing cesarean delivery but was not found in those patients delivering vaginally. ST segment elevation was not detected in either group. The incidence of ST segment depression during cesarean delivery was similar with epidural (29%), spinal (17%), and general (18%) anesthesia, occurring most commonly in the 30 min following delivery (P less than 0.001). Transthoracic echocardiographic imaging was performed in 23 patients undergoing cesarean section. Five of the 23 patients had seven episodes of intraoperative ST segment depression. Regional wall motion abnormalities were not present in any patient. A decrease in ejection fraction area greater than 15% from baseline or from previous interval ejection fraction area was present during four episodes of ST change. Three episodes of ST depression were not associated with significant decreases in ejection fraction area. Precordial Doppler monitoring for detection of venous air embolism in 25 patients revealed no association between the occurrence of venous air embolism and ST segment depression. We conclude that although significant myocardial impairment during cesarean delivery does not occur, episodes of ST depression may not all be merely an artifact of parturition.

Paradoxical air embolism in pigs with a patent foramen ovale

Recent studies have indicated that divers with a patent foramen ovale (PFO) are at risk of developing some forms of decompression sickness. Thus, the objective of the present study was to investigate if the occurrence of paradoxical air embolism (PAE) was enhanced in pigs with a PFO compared to the occurrence in pigs without such a defect. Out of 54 pigs, 18 had a PFO (group PFO), and the other 36 composed the controls (group C). The pigs were anesthetized, mechanically ventilated, and received venous air infusion at four different rates (0.050, 0.075, 0.100, and 0.200 ml.kg-1.min-1). PAE was monitored by use of a transesophageal echocardiographic probe to detect if any arterial air bubbles were present in the left atrium or the aorta. We found that PAE appeared at a lower infusion rate in group PFO than in group C. When PAE occurred, the mean pulmonary arterial pressure and the mean arterial pressure were significantly higher in pigs with a PFO than in the control pigs. Finally, the infused air volume per kilogram of body weight in group PFO was significantly lower than that observed in group C. The results demonstrated that the risk of PAE occurring in mechanically ventilated pigs with a PFO was greater compared to the risk observed in pigs without a PFO.

Fifty percent nitrous oxide does not increase the risk of venous air embolism in neurosurgical patients operated upon in the sitting position

Although nitrous oxide (N2O) should theoretically increase the severity of venous air embolism (VAE), data confirming this hazard in clinical situations are not available. The effect of 50% N2O on the incidence and severity of VAE and on the emergence time from anesthesia was evaluated in 300 neurosurgical patients operated upon while in the sitting position. Of these, 110 patients underwent craniectomy for posterior fossa pathology and 190 patients underwent cervical spine surgery (CSS). Patients were randomized to receive either 50% N2O in oxygen (O2) (N2O group) or O2 (no-N2O group) as part of an isoflurane-fentanyl-based anesthetic. In patients in the N2O group, N2O administration was discontinued immediately upon Doppler-detection of VAE and was reinstituted in not less than 30 min after resolution of the episode. The incidence of Doppler-detected VAE was significantly greater in the craniectomy group than the CSS group (43% vs. 7%, respectively; P less than 0.001). N2O had no effect on the incidence of VAE or the severity of VAE as judged by the magnitude of the reduction in blood pressure during hemodynamically significant episodes of VAE, the volume of gas aspirated from the right atrial catheter during episodes of VAE, or the magnitude of the decrease in end-tidal carbon dioxide tension during episodes of VAE. Hemodynamically significant episodes of VAE (i.e., episodes associated with a reduction in systolic blood pressure of greater than or equal to 15 mmHg) occurred in 17 of the 61 patients experiencing VAE (28%) and was not different between the N2O and no-N2O groups. Similarly, hemodynamically significant episodes of VAE (n = 18) accounted for 15% of all episodes of VAE (n = 118) and was not different between the N2O and no-N2O groups. Emergence time was not significantly different between the N2O and no-N2O groups, with mean times of 2 +/- 6 and 3 +/- 7 min (+/- SD), respectively. Emergence time was significantly longer in the craniectomy group than in the CSS group (5 vs. 1 min, respectively; P less than 0.001). Within the craniectomy group, the incidence of Doppler-detected VAE was significantly less in patients with previous surgery at the operative site (21%) compared to patients without previous surgery at the operative site (47%). Postoperatively, no complications could be related to the use of N2O or directly attributed to the occurrence of VAE.(ABSTRACT TRUNCATED AT 400 WORDS)

Pressure monitoring can accurately position catheters for air embolism aspiration

Venous air embolism is a potentially catastrophic surgical complication. While prevention and early diagnosis represent the cornerstones of management, definitive therapy of a massive air embolus relies on aspiration of the air through an appropriately located multiorifice catheter. Currently, the most common method for accurately positioning a multiorifice catheter in the high right atrium is an intravenous electrocardiogram (IVECG). Because that method is not always technically feasible, we evaluated a right ventricular waveform as a marker for accurate and reliable catheter localization. Twenty patients were prospectively evaluated. After successful insertion of an antecubital introducer sheath, a multiorifice catheter was advanced into the central circulation (5 orifices, one at the distal tip and four 1.0 x 1.5 mm side orifices spaced 0.5 cm apart beginning 1.2 cm from the distal tip). Simultaneous IVECG and pressure waveforms were monitored. After the catheter was advanced into the right ventricle, it was withdrawn until an IVECG P-wave characteristic of the superior vena cava-right atrial junction was observed. The time from cannulation of the basilic vein until obtaining a characteristic IVECG of the superior vena cava-right atrial junction was 6.6 +/- 4.2 minutes (mean +/- SD). The distance between loss of the right ventricular waveform to the appearance of the desired IVECG P-wave configuration was 3.6 +/- 0.35 cm (mean +/- SD). Because the origin of the observed IVECG complex (1.7 cm proximal to the distal orifice) and of the right ventricular waveform are located in two different places, the tip of the catheter was not considered to be in an optimal position for air aspiration.(ABSTRACT TRUNCATED AT 250 WORDS)

The double-balloon and Inoue techniques in percutaneous mitral valvuloplasty: comparative results in a series of 232 cases

Immediate hemodynamic results of percutaneous mitral valvuloplasty were compared in two consecutive series of unselected patients from the same institution undergoing valvuloplasty with the double-balloon (161 patients) or the Inoue balloon (71 patients) technique. Before valvuloplasty, the patient series were comparable with regard to average age, gender repartition and most clinical, electrocardiographic, X-ray and hemodynamic variables. Poor anatomic forms of mitral stenosis were equally distributed in both series (41% vs. 45%, p = NS). The magnitude of mitral valve area increase and of mean mitral gradient decrease during percutaneous mitral valvuloplasty did not differ significantly in the Inoue balloon and double-balloon series (mean +/- SEM 1.1 +/- 0.2 to 1.95 +/- 0.5 and 1.0 +/- 0.2 to 1.97 +/- 0.5 cm2, respectively, for mitral valve area and 12 +/- 3 to 5 +/- 2 and 13 +/- 4 to 5 +/- 2 mm Hg, respectively, for mean mitral gradient). Four cases of 3+ mitral regurgitation occurred in the Inoue balloon series and 7 in the double-balloon series (p = NS). A good immediate result--defined as mitral valve area greater than or equal to 1.5 cm2 with greater than or equal to 25% in mitral valve area gain and mitral regurgitation less than 2+ at the end of the procedure--was observed in 78% of patients in both series. Three cases of tamponade due to chamber perforation and 14 cases of transient air embolism in the right coronary system due to balloon rupture were observed in the double-balloon series.(ABSTRACT TRUNCATED AT 250 WORDS)

[A repeated massive air embolism in a patient operated on in a sitting position]

A case of repeated massive air embolism in a patient with posterior cranial fossa tumour operated on in a sitting position is described. Early diagnosis and timely intensive therapy made it possible to arrest the complication development.

Venous emboli occurring caesarean section: the effect of patient position

The effect of position, horizontal versus 5 degrees reverse Trendelenburg's, on the incidence of venous emboli during Caesarean section was evaluated in 207 patients. Venous emboli were diagnosed using precordial ultrasonic Doppler monitoring. In the horizontal position, 44% (60 of 134) parturients had venous emboli compared with 1% (1 of 73) parturients in the 5 degrees reverse Trendelenburg's position (P less than 0.0001). Epidural anaesthesia was performed in 171 patients, and 36 patients had general anaesthesia. In the epidural group, pulse oximetric haemoglobin oxygen desaturation and complaints of chest pain and/or dyspnoea were associated with the venous emboli. Venous emboli, probably air, occur frequently during Caesarean section with the patient in the horizontal position. This occurrence was minimized by placing the patient in the 5 degrees reverse Trendelenburg's position.

Blood biochemical and cellular changes during decompression and simulated extravehicular activity

Blood biochemical and cellular parameters were measured in human subjects before and after exposure to a decompression schedule involving 6 h of oxygen prebreathing. The exposure was designed to simulate extravehicular activity for 6 h (subjects performed exercise while exposed to 29.6 kPa). There were no significant differences between blood samples from subjects who were susceptible (n = 11) versus those who were resistant (n = 27) to formation of venous gas emboli. Although several statistically significant (P less than 0.05) changes in blood parameters were observed following the exposure (increases in white blood cell count, prothrombin time, and total bilirubin, and decreases in triglycerides, very-low-density lipoprotein cholesterol, and blood urea nitrogen), the changes were small in magnitude and blood factor levels remained within normal clinical ranges. Thus, the decompression schedule used in this study is not likely to result in blood changes that would pose a threat to astronauts during extravehicular activity.

Air embolism in spinal surgery

We present two cases of fatal venous air embolism that occurred in previously healthy adolescents during posterior spine fusion and instrumentation for scoliosis. Previously recorded cases in the literature have been rare and only briefly discussed. Air embolism has been a complication noted in the anesthesia and neurosurgical literature, occurring primarily in total hip patients and those patients undergoing neurosurgical procedures in a sitting position. An examination of the pathophysiology of air embolism in posterior spinal procedures would indicate the use of properly placed central lines and end-expiratory CO2 monitoring as the primary modes of detection and treatment considering the potentially fatal risk factors for spinal patients.

Precordial Doppler monitoring and pulse oximetry during cesarean delivery: detection of venous air embolism

Venous air embolism (VAE) is a potential but rare complication of cesarean delivery that can be associated with morbidity and death. Uterine sinuses are susceptible to the entrance of air during cesarean delivery. To define the incidence of VAE and its relation to arterial oxygen saturation (SaO2) and consequent electrocardiographic (ECG) changes, a prospective study was undertaken in which precordial Doppler monitoring was conducted during cesarean delivery. Concomitant, SaO2 and ECG were recorded in 78 patients. Fifty-one of 78 (65%) of the subjects had Doppler changes consistent with VAE. Of these, 37 patients (72%) showed a decreased SaO2, (average decline 5.2%). The remainder of the patients with Doppler changes showed no SaO2 change. Twenty of the patients with Doppler changes and decreased SaO2 complained of chest pain and dyspnea. Three of these patients exhibited ECG changes including ST segment depression. Although all ECG changes resolved spontaneously without sequelae, the potential clearly existed for life threatening embolic events. Thus, precordial Doppler monitoring of cesarean delivery patients demonstrated a surprisingly high incidence of Doppler changes consistent with VAE. Some episodes were associated with a significant reduction in SaO2 and rarely with ECG changes.

The incidence of venous air embolism during total hip arthroplasty

Venous air embolism has been reported to occur during total hip arthroplasty. The incidence of venous air embolism, however, has not been previously studied in a large series using Doppler ultrasound and mass spectrometry. Seventy patients undergoing total hip arthroplasty were monitored for venous air embolism with precordial Doppler ultrasound, central venous catheter, end-tidal N2 and CO2 (mass spectrometry), and arterial blood gases (ABG). Changes in the monitored variables consistent with venous air embolism were noted in 57% by Doppler ultrasound, 9% by mass spectrometry, 4% by central venous catheter and 3% of the cases by ABG. A total of 77 Doppler ultrasound events were detected in 40 of the 70 patients studied. Hemodynamic changes consisting of either hypotension, defined as a greater than or equal to 20% decrease in mean arterial pressure (MAP), or cardiac dysrhythmia occurred during 43% of these events. The Doppler ultrasound was the only monitor that detected all cases of venous air embolism with concomitant hemodynamic changes. Air was aspirated from the central venous catheter during 10% of the detections of venous air embolism by Doppler ultrasound. Venous air embolism in total hip arthroplasty is a common event and may be responsible for hemodynamic changes previously ascribed to the use of methylmethacrylate cement. Routine monitoring with Doppler ultrasound appears warranted. The routine use of central venous catheterization may also be warranted.

Dysbaric cerebral air embolism in Hawaii

Cerebral air embolism is a major cause of death and disability among sport scuba divers. To better define the epidemiologic and clinical manifestations of this infrequently encountered disorder, the records of all recompression treatments in Hawaii from 1976 through 1979 were reviewed. Forty-two cases of dysbaric air embolism (DAE) were identified on the basis of clinical criteria, accounting for 18% of the patients undergoing recompression treatment for diving-related disorders during this four-year period. In 22 patients (52%), DAE was part of a dysbarism syndrome that involved one or more forms of decompression sickness and/or in which DAE could not be differentiated from neurologic decompression sickness. The presenting signs and symptoms varied, with asymmetric multiplegia being the most common finding. Two patients died, giving a case fatality rate of 5% for those who survived until reaching the recompression chamber. Overall, 78% of the cases manifested either complete (61%) or substantial (17%) recovery with recompression and adjunctive medical measures. Traditional concepts of dysbaric cerebral air embolism are not adequate to explain the spectrum of clinical manifestations encountered in this condition.

Delayed cerebral edema complicating cerebral arterial gas embolism: case histories

A disquieting and rarely described feature of the treatment of arterial gas embolism (AGE) is the high incidence of relapse following good to excellent initial responses to recompression therapy. This paper includes a discussion of the issues involved in the etiology and clinical approach to the specific problem of relapse and relates experience from selected clinical cases to a modified therapeutic approach that has been introduced into Royal Navy diving and submarine medicine practice. It illustrates how and why current treatment procedures have been expressly designed to minimize the incidence of relapse and to modify favorably the pathophysiological responses (particularly vasogenic cerebral edema) associated with cerebral AGE.

Air embolism: a lethal but preventable complication of subclavian vein catheterization

Air embolism (AE) is a rare but lethal complication of subclavian vein catheterization (SVC). Although treatable, if recognized promptly, attention should be directed towards prevention. SVC has been used at New York University Medical Center since 1969 for parenteral nutrition; its safety and complications have been recognized and reported. Since 1976, 14 patients with AE from SVC have been observed. Thirteen occurred as a sudden catastrophic event associated with disconnection of the catheter; all had significant morbidity; 4 (29%) died; 9 (65%) had associated profound neurologic deficit from which 5 recovered completely. Five others had cardiorespiratory morbidity but also recovered. In 1 surviving patient air was aspirated from the right atrium with immediate improvement. Survivors had evidence of pulmonary AE characterized by hypoxia. AE is a syndrome of respiratory distress, hypotension, and neurologic deficit of sudden onset. Immediate treatment is aspiration through the catheter in the left lateral steep Trendelenburg position. Review of our experience with AE suggests that lack of integrity of the connection between the catheter and the intravenous tubing was the responsible mechanism in the majority of case (93%). Secure fixation of these connections is vital for the prevention of AE.

Arterial air embolism

The incidence and the outcome of systemic air embolism in 340 consecutive patients who underwent cardiac surgery under cardiopulmonary bypass in this unit for congenital defects of the cardiac septa and diseases involving the aortic and mitral valves have been studied. This was thought to have occurred in 40 patients, of whom 10 died. The distribution of air embolism according to the types of operation undertaken was as follows: six of 127 for atrial septal defect; six of 36 for ventricular septal defect; seven of 42 for mitral valve replacement; seven of 47 for aortic valve débridement; and 14 of 55 for aortic valve replacement. The cause was considered to have been systolic ejection of air into the aorta which, following cardiotomy, had been trapped in the pulmonary veins, the left atrium, the ventricular trabeculae, and the aortic root. Since the adoption of a more rigid `debubbling' routine, air embolism has not occurred. The incidence of pulmonary complications occurring in these patients after bypass was studied. Unilateral atelectasis, which occurred in five patients, resulted from retained bronchial secretions in all and was cured by bronchoscopic aspiration in all. The cause of bilateral atelectases, occurring in nine patients and fatal in eight of these, appeared to be related to cardiopulmonary factors and not to air embolism. Acute air injection made into the pulmonary artery of a dog resulted in pulmonary hypertension and a grossly deficient pulmonary circulation, but changes were largely resolved within a week. In view of this, it is considered that pulmonary air embolism may temporarily embarrass the right heart after the repair of a ventricular septal defect in a patient with an elevated pulmonary vascular resistance and diminished pulmonary vascular bed.