Dominique Girard

Detection of gas embolism by transesophageal echocardiography during laparoscopic cholecystectomy

Using transesophageal echocardiography (TEE), 16 patients (ASA physical status I-III), undergoing laparoscopic cholecystectomy, were assessed for the occurrence of episodes of gas embolism and cardiovascular changes related to those emboli. The long-axis four-chamber view was monitored continuously, except for predetermined intervals where the transgastric short-axis view was obtained to derive the end-diastolic area (EDA), the end-systolic area (ESA), and the ejection fraction (EF). In one patient, we monitored the longitudinal view of the superior and the inferior vena cava. The monitoring of the patients also included: heart rate (HR), mean arterial pressure (MAP), arterial saturation by pulse oximetry (SpO2), end-tidal CO2 (ETCO (2)), minute ventilation (VE), and peak inspiratory pressure (PIP). Embolic events were defined as the appearance of gas bubbles in the right cardiac chambers. We observed gas embolism in 11/16 patients (five during peritoneal insufflation and six during gallbladder dissection). Using the longitudinal view of the superior and inferior vena cava (IVC), we found that these emboli were transmitted through the IVC. No episode of cardiorespiratory instability (decrease in MAP >or=to 10 mm Hg, SpO2 < 90%) was observed. There was no significant difference in cardiorespiratory variables between patients who presented gas embolism (n = 11) and patients who did not (n = 5) during the studied period. In this small group of patients, we conclude that gas embolism occurs commonly during laparoscopic cholecystectomy but that these gas emboli cause minimal cardiorespiratory instability. (Anesth Analg 1996;82:119-24)

Epidural analgesia and intravenous patient-controlled analgesia result in similar rates of postoperative myocardial ischemia after aortic surgery

To assess the role of postoperative analgesia on myocardial ischemia after aortic surgery, we compared intravenous patient-controlled analgesia (PCA) with thoracic epidural analgesia (TEA). One hundred twenty-four patients were prospectively randomized to the PCA or TEA group. In the TEA group, a T6-7 or T7-8 epidural catheter was inserted before the induction of general anesthesia. Within 1 h of the end of surgery, analgesia and 24-h two-channel Holter monitoring were begun. Myocardial ischemia was defined as ST segment depression >or=to1 mm, 0.06 s after the J point, and lasting for more than 1 min. In the PCA group, a bolus of morphine, 0.05 mg/kg, was given, followed by 0.02 mg/kg of morphine on demand every 10 min. Bupivacaine 0.125% and fentanyl 10 micro g/mL was used in the TEA group. Analgesics were titrated to maintain a visual analog scale score <or=to3. The overall incidence of myocardial ischemia was 18.4%-18.2% for TEA and 18.6% for PCA (P = not significant). There were no differences between the groups in the total duration of ischemia per patient (22.2 +/- 119.8 min for TEA and 20.5 +/- 99 min for PCA) and the number of episodes per patient (0.69 +/- 2.1 for TEA and 1.2 +/- 4.9 for PCA). Twenty-three patients had an adverse cardiac outcome, although there were no differences between the groups. The postoperative pain control was superior with TEA. In these patients undergoing elective aortic surgery, the use of postoperative TEA did not result in a lower incidence of early myocardial ischemia compared with intravenous PCA with morphine, despite better analgesia with TEA. Implications: Postoperative myocardial ischemia is associated with adverse cardiac outcome. Using Holter monitoring after aortic surgery, this study shows that the use of thoracic epidural analgesia with bupivacaine and fentanyl did not result in a lower incidence of myocardial ischemia compared with intravenous patient-controlled analgesia with morphine. (Anesth Analg 1997;85:1233-9)

Venous carbon dioxide embolism in pigs: an evaluation of end-tidal carbon dioxide, transesophageal echocardiography, pulmonary artery pressure, and precordial auscultation as monitoring modalities.

We evaluated the effects of CO2 embolism on end-tidal carbon dioxide (ETCO2) and compared four methods for detection of gas embolism. Fourteen pigs were monitored for CO2 embolism with transesophageal echocardiography (TEE), changes in ETCO2, changes in mean pulmonary artery pressure (MPAP), and precordial auscultation (AUSC). Serial injections of CO2 (ranging from 0.05 to 5.0 mL/kg) were performed in seven pigs (Group 1). In the other seven pigs, CO2 was infused at rates between 0.01 and 0.4 mL.kg-1.min-1 (Group 2). Positive responses were defined as an acute change in heart sounds (AUSC), visualization of gas bubbles in the right cardiac chambers on TEE, an increase in MPAP > or = 3 mm Hg, and an acute change (increase or decrease) in ETCO2 > or = 3 mm Hg. In both groups, positive responses to CO2 embolism were represented by an initial decrease in ETCO2. The frequency with which positive responses were observed revealed that TEE was the most sensitive method (P < 0.05), whereas no differences were found among the other methods. In conclusion, in this model, positive response to CO2 embolism was represented by a decrease in ETCO2. TEE was the most sensitive method of detection of CO2 embolism, and ETCO2, MPAP, and AUSC were equally sensitive.

Cisatracurium-Induced Neuromuscular Blockade Is Affected by Chronic Phenytoin or Carbamazepine Treatment in Neurosurgical Patients

The effect of chronic anticonvulsant therapy (CAT) on the maintenance and recovery profiles of cisatracurium-induced neuromuscular blockade has not been adequately studied. In this study, we compared the pharmacokinetics and pharmacodynamics of cisatracurium after a prolonged infusion in patients with or without CAT. Thirty patients undergoing intracranial surgery were enrolled in the study: 15 patients under CAT (carbamazepine and phenytoin, Group A) and 15 controls receiving no anticonvulsant therapy (Group C). Anesthesia was standardized and both groups received a bolus of cisatracurium followed by an infusion to maintain a 95% twitch depression. A steady-state was obtained and the infusion was kept constant for 2 additional hours. Neuromuscular blockade was then allowed to spontaneously recover. Blood samples were taken for measurement of cisatracurium plasma concentration during the steady-state period (Cpss95) and at various times during recovery. Demographic and intraoperative data were similar. CAT resulted in faster 25% and 75% recovery of the first twitch. The rate of infusion of cisatracurium needed to maintain a 95% twitch depression at steady-state was 44% faster in Group A (P < 0.001). The clearance of cisatracurium was significantly faster in Group A when compared with Group C (7.12 ± 1.87 versus 5.72 ± 0.70 L · kg−1 · min−1, P = 0.01). The Cpss95 was also significantly larger in Group A (191 ± 45 versus 159 ± 36 ng/mL, P = 0.04). In addition, patients receiving CAT had a 20% increase in the clearance of cisatracurium that, in turn, resulted in a faster recovery of neuromuscular blockade after an infusion of the drug. Also, patients under CAT had a 20% increase in their Cpss95, indicating an increased resistance to the effect of cisatracurium.

The effect of propofol sedation on the intracranial pressure of patients with an intracranial space-occupying lesion.

The fear of producing CO2 retention and a secondary increase of intracranial pressure (ICP) sometimes precludes the use of sedation for the spontaneously breathing patient in the presence of an intracranial space-occupying lesion. In this study we assessed the effect of moderately deep propofol sedation on the ICP of patients undergoing stereotactic brain tumor biopsy under regional anesthesia. Thirty patients were randomized into 2 groups to receive propofol titrated to a level of 2 on the Observer’s Assessment of Alertness/ Sedation Scale or no sedation. ICP was measured via the biopsy needle. Preoperative data were similar in both groups. During surgery, patients receiving propofol had a higher arterial PCO2 (48 ± 8 mm Hg versus 41 ± 3 mm Hg; P = 0.005) (95% confidence interval, 43–53 mm Hg and 39–43 mm Hg, respectively), resulting in a lower arterial pH (P = 0.002) than patients in the no-sedation group. The median ICP (95% confidence interval) for both groups was similar—13 mm Hg (8.2–16.2 mm Hg) and 15 mm Hg (8.3–21.7 mm Hg)—for the propofol and no-sedation groups, respectively (P = 0.66). Cerebral perfusion pressure was lower in the propofol group (76 ± 18 mm Hg versus 89 ± 18 mm Hg; P = 0.003). Moderately deep propofol sedation does not result in a higher ICP than no sedation in patients undergoing stereotactic brain tumor biopsy. Further studies are needed to assess the effect on ICP of other sedative medications.

Estimation of the pulmonary capillary wedge pressure from transesophageal pulsed doppler echocardiography of pulmonary venous flow: Influence of the respiratory cycle during mechanical ventilation

OBJECTIVE Pulsed Doppler measurement of pulmonary venous flow (PVF) in the left superior pulmonary vein has been suggested as a noninvasive method to evaluate pulmonary capillary wedge pressure (PCWP). In previous studies, PVF was measured at end-expiration, and it is unknown to what extent PVF is affected by the respiratory cycle. It is hypothesized that phasic variations of PVF during mechanical ventilation may be used to estimate PCWP. DESIGN Prospective clinical study. SETTING Tertiary care university hospital. PARTICIPANTS Thirty patients undergoing elective cardiac surgery. INTERVENTIONS At multiple intervals during the surgery, the PVF was measured with transesophageal pulsed Doppler echocardiography, and measurements of PCWP and airway pressure were simultaneously obtained. MEASUREMENTS AND RESULTS Components of PVF evaluated were the systolic (X), diastolic (Y), and atrial (Z) waves with their velocity-time integrals (VTI). The systolic fraction (SF = VTI X/[VTI X + VTI Y]) and respiratory variations of each component of PVF were determined and compared with PCWP. There was a greater respiratory variation of the X wave (X expiratory-X inspiratory/X expiratory) in patients with PCWP < 18 mmHg than in patients with PCWP > or = 18 mmHg (0.19 +/- 0.19 v 0.14 +/- 0.13, respectively, p < 0.01). PVF components measured at end-expiration that related best with PCWP were the X/Y peak velocities (r = -0.53), VTI X/VTI Y ratio (r = -0.42), and the SF (r = -0.49). When measured during end-inspiration, the relation of the X/Y ratio, VTI X/VTI Y, and SF with the PCWP were r = -0.54, r = -0.41, and r = -0.50, respectively. CONCLUSIONS It has been documented that PVF velocity is influenced by the respiratory cycle during mechanical ventilation in patients undergoing cardiac surgery, and the magnitude of this variation is influenced by PCWP. However, it is not actually possible to predict PCWP accurately using these findings. Further studies are needed in which preload is varied acutely to confirm the usefulness of the results.

Haemodynamic effects of mechanical peritoneal retraction during laparoscopic cholecystectomy

PurposeAbdominal wall retraction (AWR) was recently proposed as an alternative for CO2 pneumopentoneum. In this study we evaluated the cardiorespiratory effects of AWR during laparoscopic cholecystectomy.MethodsFifteen patients were studied during laparoscopic cholecystectomy using AWR. Monitoring included heart rate (HR). mean arterial pressure (MAP), pulse oxymetry (SpO2), end-tidal CO2 (P1, CO2), minute ventilation, and peak inspiratory pressure (PIP). Using transoesophageal echocardiography, the transgastric short axis view was obtained to derive the end-diastolic area (EDA), the end-systolic area (ESA), and the ejection fraction (EF). These parameters were measured at predetermined periods: I) five minutes after anaesthetic induction, 2) five minutes after AWR insertion, 3) 15 min after AWR insertion, and 4) after the end of surgery.ResultsNo change in any measured parameter was observed over time in the AWR group except for an increase in MAP (P < 0.05) after AWR insertion. There were no changes in EDA, ESA and EF dunng the study, reflecting stable global cardiac function. In addition, no embolic episodes were observed dunng surgery.ConclusionOur results demonstrate that the use of gasless abdominal distention for laparoscopic cholecystectomy results in a stable haemodynamic profile in healthy patients without cardiac disease, except for a bnef increase in MAP after the AWR insertion. The advantages of AWR over conventional pneumoperitoneum should be confirmed in higher risk patients in a prospective, randomized study.RésuméObjectifLa rétraction de la paroi abdominale (RPA) a éte récemment proposée comme solution de rechange au pneumopéntome au CO2. Cette étude évalue les effets cardiorespiratoires de la RPA pendant la cholécystectomie laparoscopique.MéthodesQuinze patients ont été étudiés pendant une cholécystectomie laparoscopique avec RPA. Le monitorage comprenait la fréquence cardiaque (FC), la pression arténelle moyenne (PAM), I’oxymétne de pouls (SpO2). le CO2 télé-expiratoire (PETCO2) et la pression inspiratoire de pointe (PIP). Par échocardiographie transoesophagienne, on a obtenu une image du I’axe court transgastrique avec lequel étaient dénvées les surfaces télédiastolique (STD), télésystolique (STS) et la fraction d’éjection (FE). Ces paramètres étaient mesurés à des pénodes prédéterminées: I) cinq minutes après l’induction de I’anesthésie, 2) cinq minutes après I’insertion de la RPA, 3) 15 minutes après I’insertion de la RPA, et 4) une fois la chirurgie terminée.RésułtatsAucun changement des paramètres mesurés n’a été observé dans le groupe RPA à part une augmentation de la PAM (P < 0,05) après I’insertion de la RPA. La STD. la STA et la FE n’ont pas changé pendant I’étude. ce qui reflète la stabilité de la fonction cardiaque globale. En outre, on n’a pas observé d’épisodes emboliques pendant la chirurgie.ConclusionNos résultats montrent que la distension abdominale sans insufflation gazeuse procure un profil hémodynamique stable chez des patients bien portants, à I’exception d’une brève augmentation de la PAM après I’insertion de la RPA. L’avantage de la RPA sur le pneumopéritoine conventionnel devrait être confirmé chez des patients à risque plus éléve par une étude prospective et aléatoire randomisée.

Cisatracurium pharmacodynamics in patients with oculopharyngeal muscular dystrophy.

The pharmacodynamics of muscle relaxants in patients with oculopharyngeal muscular dystrophy (OPMD) have never been studied. We designed this study to compare the pharmacodynamics of cisatracurium in OPMD patients versus a control group. Forty patients were enrolled: 20 OPMD patients requiring general anesthesia for cricopharyngeal myotomy and 20 age-matched controls undergoing an operation of similar duration and expected blood loss. Anesthesia was standardized, and both groups received a bolus of cisatracurium 0.1 mg/kg. Onset time, time to 10% T1 recovery, and the intervals 10%–25% and 25%–75% were calculated for both groups. A subgroup analysis was performed in patients with a more severe form of OPMD. Demographic and intraoperative data were similar. Onset time was significantly longer in OPMD patients compared with the control group (4.6 ± 1.5 min versus 3.4 ± 1.0 min; P = 0.001). There was no difference in recovery times or indices between groups, regardless of the severity of the disease. In conclusion, there was no difference in the duration of a cisatracurium-induced neuromuscular block between OPMD patients and a control group. A delayed onset of action of the drug may occur.

Fibreoptic bronchoscopic intubation after induction of general anaesthesia: another approach

To the Editor: Oral or nasal intubation of the trachea under fibreoptic guidance is now recognised as the safest and most effective technique in known or suspected cases of difficult intubation. However, it is most successful in awake spontaneously breathing patients. Poor results can be expected when the technique is used as a last resort approach in an anaesthetized, paralysed patient in whom difficult intubation could not or was not predicted before induction of anaesthesia. 1 In particular, the use of longacting non-depolarizing muscle relaxant drugs or megadoses of narcotics may create a situation that is not rapidly reversible. We recently experienced such a problem. After induction of anaesthesia in a patient for CABG, with 5 mg fentanyl, 5 mg midazolam and 10 mg vecuronium, it was impossible to visualize the vocal cords or intubate the patient after several attempts. Ventilation by mask was easy and the oxygen saturation remained >98%. After many attempts with a fibreoptic bronchoscope we were unable to visualize the vocal cords, because of oropharyngeal soft tissues and the presence of secretions and blood. To solve that problem, we combined two techniques: a bronchoscope (6 mm diameter) was inserted through an 8 mm ID endotracheal tube until its tip was visible in the oropharynx. At that time, a second anaesthetist inserted a laryngoscope (Mclntosh blade) in the usual manner in order to pull up the tongue, the epiglottis and soft tissues of the anterior larynx (Figure). The second anaesthetist was able to guide the first for his aim with the bronchoscope. It took less than a minute to intubate the trachea that way. We think such a technique may be helpful to others when confronted with a similar problem.

Voluntary hyperventilation before a rapid-sequence induction of anesthesia does not decrease postintubation PaCO2.

To prevent hypercapnia, voluntary hyperventilation is recommended for patients with increased intracranial pressure before the induction of general anesthesia. We sought to determine whether this maneuver results in a lower Paco2 than breathing 3 min of oxygen 100% by face mask (preoxygenation) after intubation. Thirty patients requiring general anesthesia were randomly assigned to breathe either 3 min of oxygen 100% by face mask (Group P) or 1 min of oxygen 100% followed by 2 min of voluntary hyperventilation with oxygen 100% (Group H). All patients received a standard rapid-sequence induction of anesthesia followed by a 90-s period of apnea. Patients were then tracheally intubated and mechanically ventilated. Five arterial blood gas samples were taken: with room air, after preoxygen- ation or hyperventilation, after 60 and 90 s of apnea, and after tracheal intubation. Voluntary hyperventilation decreased Paco2 before rapid-sequence induction (hyperventilation, 30.0 ± 3.5 mm Hg versus preoxygenation, 37.9 ± 5.2 mm Hg;P < 0.0001), but after 60 s of apnea, both groups had similar Paco2 (hyperventilation, 36.1 ± 3.3 mm Hg versus preoxygenation, 35.6 ± 3.4 mm Hg;P = 0.673), and no benefit was found after intubation (hyperventilation, 40.5 ± 3.9 mm Hg versus preoxygenation, 41.4 ± 2.7 mm Hg;P = 0.603). We conclude that voluntary hyperventilation before rapid-sequence induction does not provide protection against potential hypercapnia during intubation.