Anis Baraka

The authors report a case of 66-year-old female patient, 55 kg, ASA I who, under general anesthesia in supine position, developed gradual hypoxemia (from a baseline PaO2 of 250 to 91 mmHg), carbon dioxide build up (from a baseline PaCO2 31 to 41 mmHg) associated with gradual hyperthermia up to 38.3 degrees C over seven hours, intraoperatively. These observations were noted while using a semi-closed carbon dioxide absorption circuit in conjunction with the Hygroster filter at a fresh gas flow of 4 1/min of 50% nitrous oxide in oxygen. While the ventilation pattern was unchanged throughout the procedure, there was a change in exhaled tidal and minute ventilation volume with a net decrease of 28 ml and 0.4 l/min respectively. Findings are probably the result of pulmonary atelecatasis under general anesthesia due to the use of a relatively high-inspired oxygen concentration (50%). In addition, the use of a high humidity and temperature heat moisture exchanger (HME) filter (Hygroster) in conjunction with the circle absorber system may have resulted in over humidification and aggravated the pulmonary atelecatasis over the long operative time.

We describe the use of noninvasive bilevel positive airway pressure (BiPAP) in a critically ill, hypoxemic and morbidly obese patient for preoxygenation prior to rapid sequence induction of anesthesia. A critically ill morbidly obese patient (body mass index: 49 kg·m^-2) was scheduled for urgent laparoscopic cholecystectomy. Preoxygenation with 5 L·min^-1 oxygen flow resulted in a moderate increase in oxygen saturation (S_PO₂) from 79% to 90%. Prior to rapid sequence induction of anesthesia, a trial of noninvasive BiPAP with oxygen delivery at 5 L·min^-1 increased his S_PO₂to 95% initially, with full saturation of 99% achieved when oxygen flow was increased to 10 L·min^-1. Bilevel positive airway pressure with an inspiratory and expiratory pressures of 17 cm H₂O and 7 cm H₂O, respectively, was applied using a full face mask to achieve a tidal volume of 8 mL·kg^-1. Rapid sequence induction proceeded uneventfully. Prior to rapid sequence induction of anesthesia in patients with respiratory compromise secondary to factors which reduce FRC, noninvasive BiPAP in combination with supplemental oxygen may be indicated whenever traditional preoxygenation does not provide adequate oxyhemoglobin saturation. Improved oxygenation is most likely attributable to improved ventilation and alveolar recruitment. Nous décrivons l’utilisation de la ventilation en pression positive non invasive à bi-niveau (BiPAP) chez un patient sévèrement malade, hypoxémique et obèse morbide, pour la préoxygénation précédant l’induction de l’anesthésie en séquence rapide. Un patient sévèrement malade et obèse morbide (indice de masse corporelle: 49 kg·m^-2) s’est présenté pour une cholécystectomie laparoscopique urgente. La préoxygénation avec un débit d’oxygène de 5 L·min-1 a eu pour résultat une augmentation modérée de la saturation d’oxygène (S_PO₂) de 79 % à 90 %. Avant l’induction de l’anesthésie à séquence rapide, un essai de BiPAP non invasive avec un débit d’oxygène à 5 L·min^-1 a accru sa S_PO₂ à 95% initialement, avec une saturation complète achevée à 99 % lorsque le débit d’oxygène a été accru à 10 L·min^-1. La ventilation en pression positive bi-niveau avec des pressions inspiratoire et expiratoire de 17 cm H₂O et 7 cm H₂O respectivement a été appliquée à l’aide d’un masque facial total afin d’obtenir un volume courant de 8 mL·kg^-1. L’induction à séquence rapide s’est déroulée sans incident. Avant l’induction de l’anesthésie à séquence rapide chez les patients présentant des difficultés respiratoires secondaires à des facteurs réduisant la capacité fonctionnelle résiduelle, la BiPAP non invasive combinée à de l’oxygène supplémentaire pourrait être indiquée lorsque la préoxygénation traditionnelle ne fournit pas une saturation de l’oxyhémoglobine appropriée. Une meilleure oxygénation est sans doute attribuable à une meilleure ventilation et à un meilleur recrutement alvéolaire.

Summary: During apnoea following induction of anaesthesia, morbidly obese patients may suffer a rapid decrease in oxygen saturation. This study compares pre‐oxygenation alone with pre‐oxygenation followed by nasopharyngeal oxygen insufflation on the onset of desaturation occurring during the subsequent apnoea. A randomised controlled trial was performed in 34 morbidly obese patients undergoing gastric bypass or gastric band surgery. Seventeen patients received nasopharyngeal oxygen supplementation following pre‐oxygenation (Study group, body mass index = 41.8 (6.9) kg.m ⁻² ), and the other 17 patients received pre‐oxygenation alone (Control group, body mass index = 42.7 (5.4) kg.m ⁻² ). Time from the onset of apnoea until S _p o ₂ fell to 95% was compared between the two groups with a cut‐off of 4 min. In the control group, the S _p o ₂ fell from 100% to 95% during the subsequent apnoea in 145 (27) s, with a significantly negative correlation ( r ² = 0.66, p < 0.05) between the time to desaturation to 95% and the body mass index. In the study group, the S _p o ₂ was maintained in 16 of 17 patients at 100% for 4 min when apnoea was terminated. In conclusion, nasopharyngeal oxygen insufflation following pre‐oxygenation in morbidly obese patients delays the onset of oxyhaemoglobin desaturation during the subsequent apnoea.

Depolarizing Block Is an Endplate-Muscular Block, Not a Neuromuscular Block Anis Baraka; Anesthesiology