Problems with telemetry monitoring systems

The purchaser of telemetry monitoring systems for operating and recovery rooms has little information available on the practical aspects of ownership and usage. To explore this problem, we recorded 76 telemetry failures (both operator and machine failure) occurring over six months among 18 telemetry channels located in operating and recovery rooms. We experienced approximately one telemetry failure every three days or every 60 surgical procedures. Factory repairs were required on 29 transmitters and 19 receivers during a two-year period. We observed that 28% of the failures were attributable to lead and electrode problems, 25% to battery depletion, 22% to mechanical or electronic component failures, 12% to inappropriate control settings and frequency mismatching, and 13% to miscellaneous difficulties. The following problems were observed. Transmitters were dropped frequently and occasionally immersed in liquids. Thus, waterproofing is recommended for OR use, and lead-failure warning circuitry is mandatory. Inappropriate control settings and frequency mismatching led to a previously unrecognized hazard: that is, it is possible to receive and display ECG data from the wrong patient located in a distant room. (Stethoscopic monitoring can be used to confirm that the data being displayed are from the correct patient.) Battery failure can occur at inopportune times, e.g., during cardiac arrest. Transmitters are frequently "lost" because of their small size and high mobility. This study indicated to us that, in the operating room, telemetry is not desirable because of its high cost compared to hard wired systems, poor reliability, and the possible hazard of displaying data from the wrong patient if improperly used.     

Cyclic nucleotides in platelet function.

Inhibition of adenylate cyclase in intact platelets by addition of compounds such as 2', 5' - dideoxyadenosine prevented the inhibition of platelet aggregation by PGE1 but did not affect the responses of platelets to aggregating agents in the absence of PGE1. This confirms that cyclic AMP mediates the effects of PGE1 but indicates that the level of cyclic AMP in unstimulated platelets is too low to affect the actions of aggregating agents. Studies on the phosphorylation of proteins in intact 32P-labelled platelets showed that PGE1 increased the phosphorylation of a membrane-bound polypeptide (P24) and prevented the increased phosphorylation of other polypeptides (P47 and P20) that occurred on addition of inducers of the release reaction. It is suggested that the cyclic AMP-dependent phosphorylation of P24 stimulates the active transport of Ca(2+) out of the platelet cytosol, so preventing phosphorylation of P47 and P20, reactions which may be involved in the release mechanism. As increases in platelet cyclic GMP could be dissociated from both platelet aggregation and the release reaction, it is proposed that the bidirectional regulation of platelet function is achieved primarily by the opposing actions of increases in the concentrations of Ca(2+) and cyclic AMP.     

Prospective study comparing three-dimensional computed tomography and magnetic resonance imaging for evaluating the renal vascular anatomy in potential living renal donors

OBJECTIVE: To prospectively compare the accuracy of multislice spiral computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) in evaluating the renal vascular anatomy in potential living renal donors. SUBJECTS AND METHODS: Thirty-one donors underwent multislice spiral CTA and gadolinium-enhanced MRA. In addition to axial images, multiplanar reconstruction and maximum intensity projections were used to display the renal vascular anatomy. Twenty-four donors had a left laparoscopic donor nephrectomy (LDN), whereas seven had right open donor nephrectomy (ODN); LDN was only considered if the renal vascular anatomy was favourable on the left. CTA and MRA images were analysed by two radiologists independently. The radiological and surgical findings were correlated after the surgery. RESULTS: CTA showed 33 arteries and 32 veins (100% sensitivity) whereas MRA showed 32 arteries and 31 veins (97% sensitivity). CTA detected all five accessory renal arteries whereas MRA only detected one. CTA also identified all three accessory renal veins whereas MRA identified two. CTA had a sensitivity of 97% and 47% for left lumbar and left gonadal veins, whereas MRA had a sensitivity of 74% and 46%, respectively. CONCLUSION: Multislice spiral CTA with three-dimensional reconstruction was more accurate than MRA for both renal arterial and venous anatomy.     

Effect of cricoid pressure on the view at laryngoscopy

The impact of cricoid pressure on laryngoscopy is unknown. We have developed a quantitative method of recording the laryngoscopic view using a rigid, zero-degree endoscope. We found that an image matching the laryngoscopist's view could be obtained by positioning the endoscope along the laryngoscopist's 'line of sight'. Photographing this image allowed us to measure laryngeal exposure. We set out to define the effect of cricoid pressure on laryngoscopy using this method. In 40 patients undergoing elective surgery, laryngoscopy was performed with cricoid pressures of 0-60 N, increasing by increments of 10 N. We photographed the laryngoscopic view at each force and recorded dynamic images as cricoid pressure was released. The change in laryngoscopic view with increasing cricoid pressure fell into one of four broad patterns: little change (11 subjects); gradual deterioration (10 subjects); improvement at low force (< 20 N) followed by deterioration (9 subjects); improvement at high force (> 30 N) (10 subjects). We identified five subjects with a good initial view (anteroposterior length of the rima glottidis > 5 mm) who showed a marked deterioration in laryngoscopic view as cricoid pressure increased; in three of these subjects this progressed to obscure the larynx completely at a force of 30 N, 40 N and 60 N, respectively. We conclude that the effect of cricoid pressure on laryngoscopy is complex. However, in some individuals, a force close to that currently recommended (30 N) may cause a complete loss of the glottic view.