Low negative predictive value of dobutamine stress echocardiography before abdominal aortic surgery

BACKGROUND

According to previous studies, a negative dobutamine stress echocardiography (DSE) test before major vascular surgery indicates that postoperative myocardial necrosis is very unlikely. We believe that the use of new cardiac troponin assays which can detect small amounts of myocardial necrosis results in a lower DSE negative predictive value for myocardial necrosis.

METHODS

A total of 418 consecutive patients were screened using the ACC/AHA Guideline for Perioperative Cardiovascular Evaluation for Noncardiac Surgery before scheduled abdominal aortic surgery. Of these 143 met ACC/AHA criteria for non-invasive testing and underwent DSE. Patients with a negative DSE were deemed to be fit for surgery. A positive DSE led to a coronary angiogram. DSE was negative in 110 (77%) and positive in 33 (23%) patients. Myocardial necrosis was monitored up to the third postoperative day by daily cardiac troponin I (cTnI) measurement and a daily 12-lead ECG.

RESULTS

Coronary angiography showed artery stenosis in 27 (84%) of 32 patients with a positive DSE. The negative predictive value of DSE for cTnI elevation was 92.7% (95% CI 86.2-96.8%). This was significantly lower than the lowest value of negative predictive value for myocardial necrosis assessed in previous studies.

CONCLUSION

A negative DSE prescribed before scheduled aortic surgery according to ACC/AHA guidelines does not rule out postoperative myocardial necrosis.

Is morphine-induced sedation synonymous with analgesia during intravenous morphine titration?

BACKGROUND

Postoperative morphine titration frequently induces sedation. The assumption is made that patients sleep when their pain is relieved. Some patients complain of persistent pain when they awake. We studied the time-course of sedation and analgesia to understand the determinants of patients' sleep during morphine titration.

METHODS

Seventy-three patients requiring morphine titration in a post-anaesthetic care unit after major surgery, were studied. Fifty-two patients slept (Sleep group) and 21 did not (Awake group). When a patient slept during titration, morphine was discontinued. Visual analogue pain scale (VAS), Ramsay score (RS), and the bispectral index (BIS) were recorded at the beginning of titration (STonset), at sleep onset (STsleep), then 5, 10, 20, and 30 min afterwards (ST4).

RESULTS

In the Sleep group, mean (SD) RS increased from 1.7 (0.4) to 2.4 (0.6) (P<0.05 vs STonset) and BIS decreased from 95 (5.0) to 89.8 (10.2) between STonset and STsleep (P<0.05), RS remained stable thereafter. Conversely, RS and BIS remained unaltered in the Awake group. The reduction in VAS was comparable between groups (from 78 (17) to 39 (21), and from 64 (16) to 30.4 (11), respectively). Even though mean (SD) VAS was 39 (21) at ST4 in the Sleep group, 13 patients (25%) maintained a VAS above 50 mm.

CONCLUSION

We observed dissociated effects of morphine on the time-course of sedation and analgesia with sedation occurring first, followed by analgesia. Therefore, morphine-induced sedation should not be considered as an indicator of an appropriate correct level of analgesia during i.v. morphine titration.

Delayed upper airway obstruction following a retropharyngeal haematoma after minor head trauma

The development of a retropharyngeal haematoma may occur rarely after major head, face or cervical spine injuries, and it is even less frequent following minor trauma. As these patients are commonly not intubated, a life-threatening upper airway obstruction may occur. We report the case of a man who experienced a late retropharyngeal haematoma with delayed, progressive upper airway obstruction after a minor frontal wound. After an emergency intubation a nuclear magnetic resonance highlighted the magnitude of the bleeding into the retropharynx accounting for the slow onset of the symptoms. Predisposing factors such as antithrombotic therapies and vascular lesions may enhance the risk of occurrence even after minor trauma. Hypotheses on how to identify this potentially fatal complication earlier are reported.