Difficult tracheal intubation in obstetrics

patients who have a cephalad displacement of the mediastinum and great vessels, faith in the classical anatomical landmarks needs to be tempered with great caution, especially when a 20-25" head-down tilt is used ro~t inely,~ since this exacerbates the effect of any abnormality. Marked upward displacement of the inferior pericardial surface accounted for the failure to aspirate blood from the pericardial sac by the subxiphisternal route in this case. Most authors suggest this is the safest route for pericardiocentesis,2*6 since the alternative parasternal approach has a higher incidence of dysrhythmias, cardiac puncture and laceration of the anterior descending coronary artery.' Sub-xiphoid pericardiostomy or window has been described as an emergency measure, as well as limited thoracotomy through the 4th or 5th left intercostal space,6 although the clinician who has no immediate access to cardiothoracic surgical expertise must exercise careful judgement before undertaking such heroic procedures. This case suggests that, in the presence of marked abdominal distension from any cause, including pregnancy, percutaneous subclavian cannulation particularly on the left side, is a hazardous procedure and should be undertaken with great caution. It may also be wiser practice to avoid long, large-bore needles and catheter-through-needle devices such as the one used in this case, and to limit venepuncture to shorter, small-gauge needles with a subsequent Seldinger wire technique, although this too has complications.