Robert H. Blackshear

Head rotation during internal jugular vein cannulation and the risk of carotid artery puncture.

We undertook a prospective laboratory study to examine the effect of head position on the relative positions of the carotid artery and the internal jugular vein (IJV).Volunteers (n = 12) from departmental staff, 18-60 yr of age, who had never undergone cannulation of the IJV underwent imaging of their IJV and carotid artery. With the subject in a 15 degrees Trendelenburg position, two-dimensional ultrasound images of the IJV and the carotid artery were obtained on the left and right sides of the neck at 2 and 4 cm from the clavicle along the lateral border of the sternal head of the sternocleidomastoid muscle at 0 degrees, 40 degrees, and 80 degrees of head rotation from the midline. The percent overlap of the carotid artery and IJV increased significantly at 40 degrees and 80 degrees head rotation to both the right and left (P < 0.05). Data from 2 and 4 cm above the clavicle did not differ and were pooled. The percent overlap was larger on the left than the right only with 80 degrees of head rotation (P < 0.05). The increased overlap of carotid artery and IJV with head rotation >40 degrees increases the risk of inadvertent puncture of the carotid artery associated with the common occurrence of transfixion of the IJV before it is identified during needle withdrawal. The IJV frequently collapses with needle insertion. This may result in puncture of the posterior wall of the vessel, and thus of the carotid artery when the two vessels overlap. To decrease this risk, the head should be kept in as neutral a position as possible, that is <40 degrees rotation, during IJV cannulation. (Anesth Analg 1996;82:125-8)

In vitro evaluation of relative perforating potential of central venous catheters: Comparison of materials, selected models, number of lumens, and angles of incidence to simulated membrane

Perforation of the vena cava or atrium is a serious complication of monitoring with a central venous catheter. We designed an in vitro model with a pulsating simulated membrane to evaluate a number of variables that could affect relative perforating potential of different types of central venous catheters. To determine the perforating potential of central venous catheters, we studied the effects of (1) the angle of incidence (n=6) between catheter and simulated membrane; (2) catheter material (polyurethane and polyethylene); (3) make (manufacturer and model) (n=6), with 3 catheters of each make tested; (4) design (n=3 each: silicone rubber, open-ended, blunt-ended, and polyurethane pigtail); and (5) number of lumens (single, double, or triple). Each trial was repeated five times with each catheter that was tested. Perforation was significantly more likely when the angle of incidence between catheter and pulsating simulated membrane was greater than 40° than when it was 40° (P<0.05). Perforation was less likely with single-lumen than comparable Frenchsized double- and triple-lumen catheters; among single-lumen catheters, perforation required many more pulsations with a polyurethane than a polyethylene catheter (P<0.001). Perforation potential differed significantly among 6 makes of 7-French triple-lumen catheters (P<0.05). Compared with other materials or designs, silicone rubber or a pigtail tip decreased the perforation potential of catheters (P<0.001). These data offer additional objective information to consider when choosing and positioning central venous catheters.

Increased pulmonary artery perforating potential of pulmonary artery catheters during hypothermia

The rate of major complications from the use of pulmonary artery (PA) catheters has been reported to be as high as 9%, 0.2% of which may be attributed to PA perforation, a catastrophe with a fatal outcome more than 50% of the time. Although an uncommon event generally, more than one third of catheter-related PA perforations occur during cardiac surgery. Several factors act to advance the balloon-tipped PA catheter into the distal PA, where, during hypothermia, the catheter hardens and, thus, may be more likely to perforate the vessel. The relative contribution of hypothermia, itself, to the perforating potential of previously used, triple-lumen PA catheters (n = 5) was examined in vitro by mounting them in a temperature-controlled testing chamber, at a 90 degrees incident angle to a polyethylene membrane, which represented the PA wall. The membrane was made to pulsate 80 times/min against the PA catheter until it was perforated. Each catheter was tested 5 times each at 3 temperatures. At 35 degrees C, 30 degrees C, and 25 degrees C, the number of pulsations to produce perforation (perforation rate) was 488 +/- 280, 309 +/- 242, and 97 +/- 234, respectively. The perforation rates differed significantly between temperatures (P less than 0.01), but not between catheters or tests at the same temperature. This study demonstrates that perforation of a model PA by a triple-lumen PA catheter is 500% more likely during hypothermia.

MULTILUMEN CENTRAL VENOUS CATHETERS IN CHILDREN: RELATIVE POTENTIAL TO PERFORATE VESSELS. AN IN VITRO STUDY

Objective. Because cardiovascular perforation by a central venouscatheter (CVC) is a serious complication of catheterization in pediatricpatients, we conducted an in vitro study of the relative potential forperforation of a standard material by the tips of multilumen pediatriccatheters. Since we could not simulate vessel tissue, we hypothesized thattesting catheters on a standard material would show whether catheters variedin tendency to perforate such a material and thus indicate a “relativepotential for perforation.” Methods. Each CVC protruding from asupport tube was suspended in a water-filled Plexiglas chamber at a 90°incident angle to a polyethylene film, which was made to bulge 6 mm into theCVC tip 120 times per minute by hydropressure. Perforation of the polyethylenefilm was documented on a time-based, strip-chart recording of pressure changeon the opposite side of the film. We recorded the number of pulsationsrequired for the following catheters to perforate the polyethylene: Arrow flextip, Cook polyurethane, Viggo hydrocath polyurethane, and Cook silicone CVCsof 4- and 5-Fr size with 2 or 3 lumens (n = 5 catheters of each type, eachcatheter being tested 5 times). Results. The number of pulsations toperforation ranged from 1 ± 0.4 SD to > 7000.Conclusions. This in vitro study of the worst-case condition(90° incident angle between CVC tip and polyethylene film) indicates thatpediatric multilumen CVCs vary significantly in their relative potential toperforate a standard material. We suggest that, when central venouscatheterization is contemplated in children, in addition to insertion site,catheter length, and depth of insertion, the type of catheter is anothervariable to consider in order to minimize the chance of cardiovascularperforation by the CVC tip.