Near infrared spectroscopy during and after cardiac arrest--preliminary results

OBJECTIVE

To evaluate if regional cerebrovascular oxygen saturation (rSO2) is linked to systemic oxygenation and if impaired regional cerebral oxygenation affects outcome in cardiac arrest patients.

DESIGN

Prospective, observational study.

SETTING

Emergency department of a University Hospital.

SUBJECTS

Patients during cardiac arrest or after restoration of spontaneous circulation.

INTERVENTIONS

To measure rSO2 an infrared light-emitting probe was applied to the patient's forehead after arrival in the emergency department. Data were collected continuously together with blood pressure and pulse oximetry. Each variable measured immediately after arrival was used for calculation.

ENDPOINTS

Best outcome (cerebral performance category) or death within one week.

MEASUREMENTS AND MAIN RESULTS

Regional SO2 was measured in 18 consecutive patients. Six patients presented with cardiac arrest on arrival and rSO2 was measured during chest compression. Twelve patients had achieved restoration of spontaneous circulation before they arrived in the emergency department. No association was found between rSO2 and pulse oximetry or rSO2 and blood pressure. All patients surviving for one week (n = 9) achieved a significantly higher median rSO2 on arrival than nonsurvivors (n = 9) (63% and 46%, respectively; p = 0.003). Median rSO2 was lower in the group arriving without spontaneous circulation (n = 6) than in patients after restoration of spontaneous circulation (n = 12) (44% and 63%, respectively; p = 0.009). This difference was not found in pulse oximetry readings. Patients with restoration of spontaneous circulation surviving the first week after cardiac arrest (n = 8) had a higher rSO2 than patients with restoration of spontaneous circulation who did not survive (n = 4) (65% and 48%, respectively). Time from restoration of spontaneous circulation to arrival was not different between the two groups.

CONCLUSION

By showing that low rSO2 readings after cardiac arrest are associated with a higher mortality, this new, non-invasive and easily applicable technique might help to prognosticate outcome and offers new insights into monitoring cerebral oxygenation after cardiac arrest.

Action of ATP on ventricular automaticity

ATP is an effective treatment of supraventricular tachycardia when the atrioventricular (AV) node is part of the reentrant circuit. However, the lower a pace-maker in the pacemaker hierarchy, the more sensitive it is to adenosine. Therefore, we investigated the effects of ATP on ventricular automaticity in in vivo and in vitro conditions. Wide and narrow QRS complex tachycardia in 46 patients was treated with 6, 12, and 18 mg ATP as sequential intravenous (i.v.) bolus. ATP terminated tachycardias in 67%. Bolus infusion ATP caused < or = 6.4-s asystole that was self-limited. Perfusion of isolated spontaneously beating guinea pig heart with 100 microM ATP completely suppressed ventricular automaticity. After ATP-infusion was discontinued, the first ventricular beat was evident after 3.1 +/- 0.9 s and sinus node activity recovered with a time constant of 3.0 +/- 1.1 s. Because sinus node and ventricular automaticity recovered within seconds after ATP infusion was discontinued in vitro, recovery in vivo is also likely to be determined by the short half-life (+1/2) of ATP.

[Emergency intubation with the Combitube in a patient with persistent vomiting]

Prompt establishment of a patient airway and effective ventilation are the major goals during initiation of cardiopulmonary resuscitation in patients with cardiac arrest. Endotracheal intubation is the definitive method to maintain an optimal airway. However, endotracheal intubation is not always possible, even for the skilled physician. The Combitube has been developed to overcome this disadvantage. Studies have proved the effectivity of ventilation with this device. A case is reported where a patient suffered from acute respiratory failure and attempts at endotracheal intubation failed due to continued vomiting rendering fibre-optical visualisation of the vocal cords impossible. Blind insertion of the Combitube led to successful ventilation, and hence replacement by an endotracheal airway could be performed without danger of aspiration.

Sudden cardiac death of a teenage girl

Anomalies of coronary artery origin can be of little clinical significance and only an incidental autopsy finding. However recent case reports have shown that a wide range of potential pathologic alterations of congenital coronary anomalies are associated with clinical symptoms and exercise related sudden death. We describe the case of a 16-year-old girl who sustained a cardiac arrest and died after cardiopulmonary resuscitation (CPR) of intractable cardiogenic shock. The sporty and previously healthy girl suddenly fainted after swimming in a tributary of the Danube. Autopsy revealed an anomalous origin of the left coronary artery from the anterior sinus of Valsalva and its course between aorta and pulmonary artery. The cause of this anomalous origin and possible mechanism for sudden death is discussed. We conclude that this congenital anomaly should be considered in cases of major cardiac events in young people.

[Intravenous urapidil versus sublingual nifedipine in the treatment of hypertensive emergencies]

In a 6-month prospective study, the efficacy and safety of urapidil and nifedipine in an out-patient population with hypertensive urgencies (systolic blood pressure > 200 mmHg; diastolic blood pressure > 110 mmHg) was investigated. Response to treatment was defined as a stable reduction of systolic blood pressure below 180 mmHg and diastolic blood pressure below 100 mmHg 15 minutes after application of a single dose of either 25 mg urapidil intravenously (N = 26) or 10 mg nifedipine sublingually (N = 27). If the blood pressure was still elevated, a second dose of 10 mg nifedipine or 12.5 mg urapidil was given, and blood pressure response was evaluated 15 minutes after application of the second dose according to the aforementioned criterias. After the first application of nifedipine, 19 (70%) responders have been observed. Eight patients needed an additional 10 mg of nifedipine. In four of these patients, no reduction of blood pressure was observed after a second dose of nifedipine. In contrast, 24 (92%) patients responded well to the first application of 25 mg of urapidil. Two patients required a second dose of 12.5 mg of urapidil, but no nonresponder to urapidil was observed. No severe side-effects were noted in both groups. Intravenous urapidil is a highly effective drug in the treatment of hypertensive urgencies and is more effective than sublingual nifedipine, because the number of patients treated successfully was significantly higher.

A new preparation of nifedipine for sublingual application in hypertensive urgencies

A new preparation of nifedipine for sublingual application in hypertensive urgencies was investigated in a prospective study. Patients admitted to the Emergency Department with a persistent elevation of systolic blood pressure (SBP) greater than 190 mmHg and/or a diastolic blood pressure (DBP) greater than 100 mmHg received nifedipine 10 mg sublingual with a sprayer. A second dose was administrated fifteen minutes later if an adequate response defined as a stable reduction of SBP below 180 mmHg and DBP below 100 mmHg had not occurred. Of 30 patients, 21 (70%) responded to the first nifedipine application, 7 responded to the second dose, and 2 nonresponders had to be treated with urapidil. Overall mean SBP was 206 +/- 19 mmHg and mean DBP was 113 +/- 15 mmHg before treatment, and a significant antihypertensive effect was noted within fifteen minutes after nifedipine spray (p < 0.05). The maximum antihypertensive effect was for SBP in sixty minutes (146 +/- 19 mmHg) and for DBP after one hundred twenty minutes (78 +/- 18 mmHg). The average reduction in SBP was 29% and in DBP 31%. In first-dose responders (n = 21) a significant antihypertensive effect was noted within fifteen minutes. SBP declined from 205 +/- 21 to a minimum of 142 +/- 15 mmHg (22.3%) after sixty minutes and DBP from 113 +/- 13 to a minimum of 77 +/- 11 mmHg (22.2%) after one hundred twenty minutes. In second-dose responders (n = 7) a significant antihypertensive effect was noted within thirty minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mild hypothermia after cardiac arrest in dogs does not affect postarrest cerebral oxygen uptake/delivery mismatching

PURPOSE

To compare measurements of cerebral arteriovenous oxygen content differences (oxygen extraction ratios, oxygen utilization coefficients) in dogs after cardiac arrest, resuscitated under normothermia vs. mild hypothermia for 1-2 h or 12 h.

METHODS

In 20 dogs, we used our model of ventricular fibrillation (no blood flow) of 12.5 min, reperfusion with brief cardiopulmonary bypass, and controlled ventilation, normotension, normoxemia, and mild hypocapnia to 24 h. We compared a normothermic control Group I (37.5 degrees C) (n = 8); with brief mild hypothermia in Group II (core and tympanic membrane temperature about 34 degrees C during the first hour after arrest) (n = 6); and with prolonged mild hypothermia in Group III (34 degrees C during the first 12 h after arrest) (n = 6).

RESULTS

In Group I, the cerebral arteriovenous O2 content difference was 5.6 +/- 1.6 ml/dl before arrest; was low during reperfusion (transient hyperemia) and increased (worsened) significantly to 8.8 +/- 2.8 ml/dl at 1 h, remained increased until 18 h, and returned to baseline levels at 24 h after reperfusion. These values were not significantly different in hypothermic Groups II and III. The cerebral venous (saggital sinus) PO2 (PssO2) was about 40 mmHg (range 29-53) in all three groups before arrest and decreased significantly below baseline values, between 1 h and 18 h after arrest; the lowest mean values were 19 +/- 19 mmHg in Group I, 15 +/- 8 in Group II (NS), and 21 +/- 3 in Group III (NS). Postarrest PssO2 values of < or = 20 mmHg were found in 6/8 dogs in Group I, 5/6 in Group II and 4/6 in Group III. Among the 120 values of PssO2 measured between 1 h and 18 h after arrest, 32 were below the critical value of 20 mmHg.

CONCLUSIONS

After prolonged cardiac arrest, critically low cerebral venous O2 values suggest inadequate cerebral O2 delivery. Brief or prolonged mild hypothermia after arrest does not mitigate the postarrest cerebral O2 uptake/delivery mismatching.

Adenosine for the management of patients with tachycardias--a new protocol

We developed a new protocol for diagnosis and treatment of patients with sustained tachycardias (heart rate > 150 beats.min-1). The patients first underwent vagal manoeuvres; if those remained unsuccessful, i.v. adenosine in increasing doses of 6, 12, and 18 mg was administered until sinus rhythm (SR) or transient atrioventricular (AV) block, unmasking the underlying rhythm, was recorded. In the latter and in the non-responding cases other antiarrhythmics were applied. Ninety-three episodes of tachycardia in 46 patients were treated according to this protocol. Six episodes (6%) were terminated by carotid massage, 64 of the remaining 87 episodes (74%) responded to adenosine with return to SR. Conversion to SR occurred more often in episodes with narrow- than in wide-complex tachycardia (81 vs. 59%, P < 0.05). To achieve SR, the mean adenosine dose was lower in narrow- than in wide-complex tachycardia (13 +/- 8 vs 21 +/- 10 mg; P < 0.01). The duration of asystole after adenosine did not differ between these two groups, whereas the duration of arrhythmia after adenosine differed significantly (8.5 +/- 5.8 vs 18.6 +/- 22.9 s; P < 0.05). Side effects of adenosine such as flush, dyspnoea, and chest pain did not seem to be dose dependent and occurred in about 20%. According to our protocol, in more than 75% SR was achieved in patients with sustained tachycardias after vagal manoeuvres and adenosine.

Cerebral and systemic arteriovenous oxygen monitoring after cardiac arrest. Inadequate cerebral oxygen delivery

BACKGROUND

After prolonged cardiac arrest, under controlled normotension, cardiac output and cerebral blood flow are reduced for several hours. This dog study documents for the first time the postarrest reduction in oxygen (O2) delivery in relation to O2 uptake for brain and entire organism.

METHODS

In eight dogs we used our model of ventricular fibrillation (VF) cardiac arrest of 12.5 min, reperfusion with brief cardiopulmonary bypass, and controlled normotension, normoxemia, and mild hypocapnia to 24 h.

RESULTS

Between 4 and 24 h after cardiac arrest, cardiac output decreased by about 25% and the systemic arteriovenous O2 content difference doubled, while the calculated systemic O2 utilization coefficient (O2 UC) increased and the systemic venous PO2 decreased, both not to critical levels. The cerebral arteriovenous O2 content difference however, which was 5.6 +/- 1.7 ml/dl before arrest, increased between 1 and 18 h, to 10.8 +/- 3.2 ml/dl at 4 h. The cerebral O2 UC increased and the cerebral venous PO2 decreased, both to critical levels.

CONCLUSIONS

After prolonged cardiac arrest in dogs with previously fit hearts, the reduction of O2 transport to the brain is worse than its reduction to the whole organism. Monitoring these values might help in titrating life-support therapies.