Internal jugular vein cannulation confused with carotid artery cannulation

We report an unusual finding which occurred during insertion of a catheter into the internal jugular vein. A 64-year-old man with ischaemic heart disease was scheduled for elective myocardial revascularisation. Central venous and arterial catheters were inserted under local anaesthesia prior to induction of general anaesthesia. The patient was receiving supplemental oxygen (6 l.min−1) via a facemask. Cannulation of the right internal jugular vein was attempted, using anatomical landmarks and palpation of the carotid artery to guide placement [1]. An 18 gauge ‘seeker’ needle technique was used and a vessel was located. Free aspiration of blood was obtained from an apparently low-pressure vessel lateral to the carotid pulse. However, the aspirated blood was bright red in appearance, suggesting an arterial sample. Further attempts achieved the same clinical finding. We were therefore reluctant to cannulate this vessel. Subsequent attempts on the left side by a more experienced operator resulted in the same finding. Closer inspection of the cardiac catheter report revealed an incidental finding of partial anomalous pulmonary venous drainage into the high right atrium. This caused an increase in central venous saturation (92% on room air). Blood gas analysis of the aspirated blood was not helpful in distinguishing the origin of the sample but analysis of the waveform and pressure trace was invaluable. There was immediate confirmation of venous rather than arterial cannulation. Inadvertent carotid artery puncture is the commonest complication associated with internal jugular vein cannulation. Arterial cannulation can result in adverse sequelae, particularly when unrecognised. This is a case report of the reverse, namely venous puncture being mistaken for arterial puncture, resulting in multiple attempts prior to successful catheter placement. Differentiation between arterial and venous cannulation is imperative. Jobes et al. [2] noted a 3.9% incidence of carotid artery puncture in a prospective study of internal jugular vein cannulation in 1284 patients. In 10 patients, arterial cannulation was not detected by simple observation of blood flow or colour. Pressure recordings were, however, diagnostic in all cases. Neustein et al. [3] described a ‘colour test’ in which a sample from the cannulated vein was visually compared with a sample simultaneously drawn from an arterial line. Supplementary oxygen was administered to enhance the colour difference. This test was found to be 100% reliable in more than 2000 patients. The comparison of colour may, however, be less than reliable in some circumstances. There may be decreased cerebral oxygen consumption in anaesthetised and hypothermic patients which could make colour comparison less sensitive [3]. High mixed venous oxygen saturations due to left-to-right shunts will reduce the arterio-venous gradient and can also cause confusion. Confusion in respect of needle placement occurred in a patient with 90% burns [4]. Bright red blood was obtained from a needle in the internal jugular vein and a partial pressure of oxygen in the blood (PO2) of 116 mmHg made the anaesthetist suppose that the needle was in the artery and remove the needle. Confirmation that the reinserted needle was in the vein was only made after a PO2 of 124 mmHg was measured in a second venous sample and a PO2 of 398 mmHg was measured in an arterial sample. Both systemic and central shunts result in mixing of arterial and venous blood. Yee and Despotis reported difficulty with colour comparison in a patient with a forearm anteriovenous haemodialysis fistula [5]. Such cases are of course very rare. Intracardiac left-to-right shunts demonstrate unpredictable mixing of oxygenated arterial and mixed venous blood, as was observed in our patient. We, however, had the benefit of a cardiac catheter report indicating previously measured venous oxygen saturation. This information may of course not always be available. Simple assessment of colour and flow is not always reliable. We would therefore recommend that monitoring equipment is always available to display the pressure waveform in a cannulated central vessel to ensure correct placement of the central venous catheter.