Emergency intubation with the Combitube in a grossly obese patient with bull neck

A grossly obese patient with bull neck required immediate intubation. Endotracheal intubation failed because visualization of the vocal cords was not possible. As an alternative, the Combitube was inserted without difficulty and the patients lungs were ventilated via the Combitube until tracheotomy was performed on the following day. The patient survived and was discharged alive from the hospital 5 weeks later. The Combitube has gained worldwide interest and is now included in the Guidelines of the American Heart Association and the American Society of Anesthesiologists.

Intravenous urapidil versus sublingual nifedipine in the treatment of hypertensive urgencies

In a 6-month prospective study, the efficacy and safety of urapidil and nifedipine in an outpatient population with hypertensive urgencies (systolic blood pressure > 200 mm Hg; diastolic blood pressure > 110 mm Hg) was investigated. Response to treatment was defined as a stable reduction of systolic blood pressure below 180 mm Hg and diastolic blood pressure below 100 mm Hg 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.

Mild hypothermia after cardiac arrest in dogs does not affect postarrest multifocal cerebral hypoperfusion

BACKGROUND AND PURPOSE

Although mild resuscitative hypothermia (34 degrees C) immediately after cardiac arrest improves neurological outcome in dogs, its effects on cerebral blood flow and metabolism are unknown.

METHODS

We used stable xenon-enhanced computed tomography to study local, regional, and global cerebral blood flow patterns up to 4 hours after cardiac arrest in dogs. We compared a normothermic (37.5 degrees C) control group (group I, n = 5) with a postarrest mild hypothermic group (group II, n = 5). After ventricular fibrillation of 12.5 minutes and reperfusion with brief cardiopulmonary bypass, the ventilation, normotension, normoxia, and mild hypocapnia were controlled to 4 hours after cardiac arrest. Group II received (minimal) head cooling during cardiac arrest, followed by systemic bypass cooling (to 34 degrees C) during the first hour of reperfusion after cardiac arrest.

RESULTS

The postarrest homogeneous transient hyperemia was followed by global hypoperfusion from 1 to 4 hours after arrest, with increased "no-flow" and "trickle-flow" voxels (compared with baseline), without group differences. At 1 to 4 hours, mean global cerebral blood flow in computed tomographic slices was 55% of baseline in group I and 64% in group II (NS). No flow (local cerebral blood flow < 5 mL/100 cm3 per minute) occurred in 5 +/- 2% of the voxels in group I versus 9 +/- 5% in group II (NS). Trickle flow (5 to 10 mL/100 cm3 per minute) occurred in 10 +/- 3% voxels in group I versus 16 +/- 4% in group II (NS). Cerebral blood flow values in eight brain regions followed the same hyperemia-hypoperfusion sequence as global cerebral blood flow, with no significant difference in regional values between groups. The global cerebral metabolic rate of oxygen, which ranged between 2.7 and 4.5 mL/100 cm3 per minute before arrest in both groups, was at 1 hour after arrest 1.8 +/- 0.3 mL in normothermic group I (n = 3) and 1.9 +/- 0.4 mL is still-hypothermic group II (n = 5); at 2 and 4 hours after arrest, it ranged between 1.2 and 4.2 mL in group I and between 1.2 and 2.6 mL in group II.

CONCLUSIONS

After cardiac arrest, mild resuscitative hypothermia lasting 1 hour does not significantly affect patterns of cerebral blood flow and oxygen uptake. This suggests that different mechanisms may explain its mitigating effect on brain damage.

Frequency-dependent effects of adenosine and verapamil on atrioventricular conduction of isolated guinea pig hearts

Frequency-dependent depressant effects of a drug on slow channels in the atrioventricular (AV) node are important in its efficacy against supraventricular tachycardias. Verapamil terminates reentrant supraventricular arrhythmias by depressing conduction through the AV node. Similar effects have been described for adenosine. We compared the use-dependent effects of both drugs on AV nodal conduction in isolated guinea pig hearts perfused by the method of Langendorff. Adenosine 3 microM and verapamil 0.01 microM caused a comparable prolongation of AV conduction time (AVCT) and reduction in sinus rate (SR). The time dependence of drug-induced changes in AV conduction was characterized after the atrial pacing rate was changed abruptly. The basic cycle length was shortened abruptly from 240 to 180 ms. The resulting time constant for adenosine (tau = 467 +/- 187 beats, mean +/- SD) was significantly (p < 0.05) longer than that for verapamil (tau = 264 +/- 121 beats). At a pacing cycle length of 180 ms, the rate-dependent conduction slowing tended to be more pronounced in the presence of adenosine than of verapamil. Adenosine had more pronounced frequency-dependent effects on AV conduction than did the calcium channel blocker verapamil. This may explain the higher clinical efficacy of adenosine in supraventricular tachycardias in which the AV node forms a part of the reentrant circuit.

Early prediction of individual outcome after cardiopulmonary resuscitation

Prediction of individual outcome after cardiopulmonary resuscitation is of major medical, ethical, and socioeconomic interest but uncertain. We studied the early predictive potency of evoked potential recording after cardiac arrest in 66 resuscitated patients who returned to spontaneous circulation but were unconscious and mechanically ventilated. Detailed long-latency and short-latency sensory evoked potentials were recorded and neurological evaluations were done 4-48 h after admission to intensive care. In all 17 patients with favourable outcome (cerebral performance categories 1 and 2) the cortical evoked potential N70 peak, a reliable measure of cortical function, was detected between 74 and 116 ms. In 49 patients with bad outcome (categories 4 and 5) the N70 peak was absent in 35 or found with a delay between 121 and 171 ms in 14 (p < 0.05 vs favourable outcome). Thus the predictive ability was 100% with cutoff of 118 ms. To confirm reproducibility and validity, repeated tracings, and linked-earlobe referenced techniques were done and gave similar results. Early recording of long-latency evoked potentials after cardiopulmonary resuscitation is highly predictive of outcome.

Detoxification with hemabsorption after cardiac arrest does not improve neurologic recovery. Review and outcome study in dogs

We and others hypothesized that noxious substances released after prolonged cardiac arrest from malfunctioning liver, kidneys, or intestine (e.g. bacterial toxins, aromatic amino acids), might hamper recovery of the brain. The highly detoxifying effect of hemabsorption (i.e. hemoperfusion) with microencapsulated activated carbon has been demonstrated in other diseases. We used our dog model of ventricular fibrillation cardiac arrest of 15 min (n = 2 x 4) or 12.5 min (n = 2 x 6), reversed by brief (high flow) cardiopulmonary bypass (CPB). In half of the dogs in each insult group, a charcoal filter (HemoKart) was inserted into the circuit of CPB at low flow, from start of reperfusion to 4 h. Intermittent positive pressure ventilation was to 20 h and intensive care to 96 h after cardiac arrest. Bacterial blood cultures were positive in most of the dogs in both groups 30 min to 20 h after cardiac arrest (but not later) and were uninfluenced by hemabsorption. In the control groups to 4 h after cardiac arrest, serum levels of potentially injurious aromatic amino acids (e.g. phenylalanine, tyrosine) and of branched-chain/aromatic amino acid ratios, remained unchanged. From 12 to 48 h after cardiac arrest, aromatic amino acid levels increased (worsened). The branched-chain/aromatic amino acid ratios changed accordingly in the opposite direction. In the hemabsorption groups to 4 h after cardiac arrest, all amino acid levels were reduced, aromatic amino acids more so than branched-chain amino acids, thus increasing (improving) the ratio, compared with controls (P < 0.01). There was no group difference after discontinuance of hemabsorption at 4 h. Outcome in terms of overall performance categories and neurologic deficit scores from 24 to 96 h and brain histopathologic damage scores 96 h after cardiac arrest, were not significantly different between groups. The lack of a beneficial outcome effect of hemabsorption to 4 h after cardiac arrest does not support the self-intoxication hypothesis. The amino acid levels later after cardiac arrest suggest that more prolonged hemabsorption and more encompassing detoxification treatments, such as plasma phoresis or total body blood washout, might be evaluated.

Systematic development of cerebral resuscitation after cardiac arrest. Three promising treatments: cardiopulmonary bypass, hypertensive hemodilution, and mild hypothermia

Since 1970 we have investigated postischemic anoxic encephalopathy and potential treatments for cerebral resuscitation after cardiac arrest by cardiopulmonary-cerebral resuscitation (CPCR). The post-resuscitation syndrome has been studied at the levels of cell, organ, organism and community. Short-term and long-term models in rats, dogs, and monkeys have been developed, and an international multicenter randomized clinical trial mechanism was established. Clinical studies disproved the 5-min limit of reversible cardiac arrest and yielded other valuable data on treatments and prognostication. Thiopental loading or calcium entry blocker therapy (lidoflazine) gave no significant improvement in patients. Free radical scavengers are under investigation in the laboratory. We hypothesize that post-arrest perfusion failure and necrotizing cascades require etiology-specific combination treatments. Standard (control) therapy in a current dog model of cardiac arrest (no flow) of 12.5-20 min, reperfusion with cardiopulmonary bypass, and intensive care for 72-96 h has consistently resulted in survival with brain damage. After ventricular-fibrillation (VF) arrest of 17 min, moderate hypothermia (28-32 degrees C) inconsistently improved cerebral outcome. After VF arrest of 12.5 min, hypertension plus hemodilution normalized the local (multifocal) cerebral hypoperfusion post-arrest and, again, inconsistently improved cerebral outcome. Additional mild hypothermia (34-36 degrees C), however, consistently improved cerebral outcome, whether induced before or during and after arrest.

Effects of adenosine on electrical activity of isolated guinea pig hearts

Negative chronotropic and dromotropic effects of adenosine seem to be responsible for its antiarrhythmic action on supraventricular tachyarrhythmias. To further characterize the effects of adenosine on supraventricular arrhythmias heart rate, conduction, refractoriness, the time to steady-state of AV-nodal conduction slowing and of sinus rate reduction were evaluated. Changes of heart rate, conduction intervals and effective refractory periods were determined by the use of a high-resolution ECG recording technique in isolated guinea pig hearts perfused by the method of Langendorff. Adenosine in concentrations of 3 and 10 microM reduced sinus rate and prolonged AV-nodal conduction significantly, while intraventricular and His bundle conduction were not altered. The maximal effect of adenosine on the sinus node and AV nodal conduction occurred after 636 +/- 109 and 111 +/- 35 (mean +/- SE) beats, respectively. During programmed stimulation at a cycle length of 250 ms, adenosine reduced atrial ERP in a dose-dependent manner. At cycle lengths of 170 and 200 ms, adenosine increased the atrial ERP at 3 microM, and then progressively shortened the ERP at higher doses. At all adenosine concentrations used, the usual rate-dependent adaption in ERP was suppressed. These observations explain the efficacy of adenosine against supraventricular tachyarrhythmias where the AV-node forms a part of a reentrant circuit. Adenosine shortened the atrial ERP, but at high pacing rates also led to a relative prolongation of the atrial ERP as the rate-dependent adaption was suppressed. These opposite effects of adenosine may explain earlier contradictory findings of its action on atrial arrhythmias.

Multifocal cerebral blood flow by Xe-CT and global cerebral metabolism after prolonged cardiac arrest in dogs. Reperfusion with open-chest CPR or cardiopulmonary bypass

Using the stable xenon-enhanced computed tomography (Xe-CT) method in dogs, we studied local, regional and global cerebral blood flow (LCBF, rCBF and gCBF) in two sham experiments and nine cardiac arrest experiments. Within the same experiments without arrest, gCBF and rCBF values were reproducible and stable. LCBF values varied over time. In group I (n = 4), ventricular fibrillation cardiac arrest (no blood flow) of 10 min was reversed by open-chest cardiopulmonary resuscitation (CPR). In group II (n = 5), ventricular fibrillation cardiac arrest of 12.5 min was reversed by brief closed-chest cardiopulmonary bypass. This was followed by controlled ventilation, normotension, normoxia, normocarbia and normothermia to 4 h (n = 7) or 20 h (n = 2) postarrest. The postarrest CBF patterns were similar in both groups. Open-chest CPR during ventricular fibrillation generated near-baseline gCBF and lower LCBF ranges. During postarrest spontaneous circulation, transient diffuse hyperemia was without low-flow regions, longer in brain stem and basal ganglia than in neocortex. During delayed hypoperfusion at 1-4 h postarrest (n = 9), mean gCBF was 44-60% baseline, rCBF in primarily gray matter regions was 15-49 ml/100 cm3 per min and LCBF voxels with trickle-flow and low-flow values, in percent of CT cut area, were increased over baseline. Global CMRO2 (n = 3 of group II) recovered to near baseline values between 1 and 4 h postarrest, while gCBF and O2 delivery were about 50% baseline (mismatching of O2 uptake and O2 delivery).

[Resuscitation of patients using a cardiopulmonary bypass]

The use of cardiopulmonary bypass within the framework of resuscitation justifies hopes for better results after cardiovascular arrest. By restituting sufficient cardiovascular conditions both the global and especially the cerebral blood flow situation are improved, so that, in turn, better neurological results can be expected after cardiopulmonary resuscitation. However, further decisive successes by using the cardiopulmonary bypass can be expected only in connection with new therapeutic concepts of reanimation.

Hypertension with hemodilution prevents multifocal cerebral hypoperfusion after cardiac arrest in dogs

BACKGROUND

Improved neurological outcome with postarrest hypertensive hemodilution in an earlier study could be the result of more homogeneous cerebral perfusion and improved O2 delivery. We explored global, regional, and local cerebral blood flow by stable xenon-enhanced computed tomography and global cerebral metabolism in our dog cardiac arrest model.

METHODS

Ventricular fibrillation cardiac arrest of 12.5 minutes was reversed by brief cardiopulmonary bypass, followed by life support to 4 hours postarrest. We compared control group I (n = 5; mean arterial blood pressure, 100 mm Hg; hematocrit, greater than or equal to 35%) with immediately postarrest reflow-promoted group II (n = 5; mean arterial blood pressure, 140-110 mm Hg; hypervolemic hemodilution with plasma substitute to hematocrit, 20-25%).

RESULTS

After initial hyperemia in both groups, during the "delayed hypoperfusion phase" at 1-4 hours postarrest, global cerebral blood flow was 51-60% of baseline in group I versus 85-100% of baseline in group II (p less than 0.01). Percentages of brain tissue voxels with no flow, trickle flow, or low flow were lower (p less than 0.01) and mean regional cerebral blood flow values were higher in group II (p less than 0.01). Global cerebral oxygen uptake recovered to near baseline values at 3-4 hours postarrest in both groups. Postarrest arterial O2 content, however, in hemodiluted group II was 40-50% of that in group I. Thus, the O2 uptake/delivery ratio was increased (worsened) in both groups at 2-4 hours postarrest.

CONCLUSIONS

After prolonged cardiac arrest, immediately induced moderate hypertensive hemodilution to hematocrit 20-25% can normalize cerebral blood flow patterns (improve homogeneity of cerebral perfusion), but does not improve cerebral O2 delivery, since the flow benefit is offset by decreased arterial O2 content. Individualized titration of hematocrit or hemodilution with acellular O2 carrying blood substitute (stroma-free hemoglobin or fluorocarbon solution) would be required to improve O2 uptake/delivery ratio.

Effects of U74006F on multifocal cerebral blood flow and metabolism after cardiac arrest in dogs

Lipid peroxidation reactions during reperfusion after cardiac arrest may contribute to postischemic cerebral hypoperfusion, which in turn can contribute to permanent neurological dysfunction. We designed this study to determine whether the aminosteroid U74006F, a putative inhibitor of lipid peroxidation, mitigates cerebral multifocal hypoperfusion after cardiac arrest. We used our established dog model of ventricular fibrillation cardiac arrest (no blood flow) of 12.5 minutes, reperfusion by cardiopulmonary bypass of less than or equal to 5 minutes, and control of extracerebral variables during 4 hours postarrest. Cerebral blood flow was monitored by the stable xenon computed tomography method. Changes in cerebral oxygen consumption were obtained from mean blood flow values of coronal slices and the cerebral arteriovenous (sagittal sinus) oxygen content difference. A treatment group (n = 5) received U74006F starting with reperfusion (1.5 mg/kg i.a. plus 1.5 mg/kg i.v.) and three additional (graded) doses over 4 hours (total dose 4.5, 7.5, or 14.5 mg/kg). The U74006F-treated group showed the same postarrest transient hyperemia and protracted hypoperfusion in terms of global (computed tomography slice), regional, and local (multifocal) cerebral blood flow values and the same global cerebral oxygen consumption pattern as a concurrent control group (n = 5). At 1-4 hours postarrest, in both groups there was mismatching of global cerebral oxygen consumption, which reached baseline values, in relation to global cerebral blood flow and oxygen delivery, which remained at 50% of baseline. We conclude that treatment with U74006F after prolonged cardiac arrest causes no deleterious side effects and does not seem to alter multifocal postarrest cerebral blood flow and oxygen consumption.

Moderate hypothermia after cardiac arrest of 17 minutes in dogs. Effect on cerebral and cardiac outcome

Moderate hypothermia (30 degrees C) induced before circulatory arrest is known to improve neurologic outcome. We explored, for the first time in a reproducible dog outcome model, moderate hypothermia induced during reperfusion after cardiac arrest (resuscitation). In three groups of six dogs each (N = 18), normothermic ventricular fibrillation cardiac arrest (no blood flow) of 17 minutes was reversed by cardiopulmonary bypass--normothermic in control group I (37.5 degrees C) and hypothermic to 3 hours in groups II (32 degrees C) and III (28 degrees C). Defibrillation was achieved in less than or equal to 5 minutes and partial bypass was continued to 4 hours, controlled ventilation to 20 hours, and intensive care to 96 hours. All 18 dogs survived. Electroencephalographic activity returned significantly earlier in groups II and III. Mean +/- SD best neurologic deficit between 48 and 96 hours was 44 +/- 8% in group I, 38 +/- 12% in group II, and 35 +/- 7% in group III (differences not significant). Best overall performance category 2 (good outcome) between 48 and 96 hours was achieved in none of the six dogs in group I and in four of the 12 dogs in the combined hypothermic groups II and III (difference not significant). Mean +/- SD brain total histologic damage score was 130 +/- 22 in group I, 93 +/- 28 in group II (p = 0.05), and 80 +/- 26 in group III (p = 0.03). Gross myocardial damage was greater in groups II and III than in group I--numerically higher overall and significantly higher in group III for the right ventricle alone (p = 0.02). Moderate hypothermia after prolonged cardiac arrest may or may not improve cerebral outcome slightly and can worsen myocardial damage.

Cardiac resuscitability with cardiopulmonary bypass after increasing ventricular fibrillation times in dogs

Previous studies in dogs have shown resuscitation from prolonged cardiac arrest to conscious survival to be more effective with the use of cardiopulmonary bypass (CPB) than with standard advanced cardiac life support. This study compared cardiovascular resuscitability with CPB only after varying periods of cardiac arrest without artificial circulatory support in a canine model. Group 1 (ten) was subjected to ventricular fibrillation for 15 minutes; group 2 (ten) for 20 minutes; and group 3 (ten) for 30 minutes. All received total CPB after ventricular fibrillation without advanced cardiac life support to defibrillation at two to five minutes and partial CPB to four hours. In all three groups CPB with epinephrine generated normal coronary perfusion pressure and increased ventricular fibrillation amplitude significantly. In groups 1 and 2, CPB reperfusion allowed for successful defibrillation in less than five minutes, weaning from CPB in all dogs at four hours, and stable spontaneous circulation thereafter. In group 3, only five of ten dogs could be weaned from bypass at four hours, and all died early with myocardial necroses. It was concluded that CPB may be of value in the setting of prolonged cardiac arrest when advanced cardiac life support has not been provided or is unable to restore spontaneous heart-beat.

Hypertension with or without hemodilution after cardiac arrest in dogs

We studied blood flow-promoting therapies after cardiac arrest in 18 dogs. Our model consisted of ventricular fibrillation (no blood flow) lasting 12.5 minutes, controlled reperfusion with cardiopulmonary bypass and defibrillation within 5 minutes, controlled intermittent positive-pressure ventilation to 20 hours, and intensive care to 96 hours. Group I (control, n = 6) dogs were reperfused under conditions of normotension (mean arterial blood pressure 100 mm Hg) and normal hematocrit (greater than or equal to 35%). Group II (n = 6) and III (n = 6) dogs were treated with norepinephrine at the beginning of reperfusion to induce hypertension for 4 hours. In addition, group III dogs received hypervolemic hemodilution to a hematocrit of 20% using dextran 40. There were no differences in the time to recovery of electroencephalographic activity among groups. All six group I dogs remained severely disabled; in groups II and III combined, six of the 12 dogs achieved good outcome (p less than 0.01). Some regional histopathologic damage scores at 96 hours were better in groups II and/or III than in group I (neocortex: p less than 0.05 group II different from group I; hippocampus: p less than 0.01 both groups II and III different from group I). Total histopathologic damage scores were similar among the groups. A hypertensive bout with a peak mean arterial blood pressure of greater than or equal to 200 mm Hg beginning 1-5 minutes after the start of reperfusion was correlated with good outcome (p less than 0.01). Our results support the use of an initial bout of severe hypertension, but not the use of delayed hemodilution.

Therapeutic deep hypothermic circulatory arrest in dogs: a resuscitation modality for hemorrhagic shock with 'irreparable' injury

Early deaths from trauma are often caused by exsanguinating hemorrhage from injuries that appear "irreparable." We explored the limits of deep hypothermic circulatory arrest induced during hemorrhagic shock to enable repair of these injuries in a bloodless field. In 15 dogs, after 30 minutes of hemorrhagic shock (mean arterial pressure, 40 mm Hg), cardiopulmonary bypass (CPB) was used to cool to 15 degrees C in 13-37 minutes. After circulatory arrest of 60 (Group 1), 90 (Group 2), or 120 (Group 3) minutes, reperfusion and rewarming were accomplished by CPB. All dogs survived greater than 72 hours. Best neurologic deficit scores (ND) (0% = normal, 100% = brain death) were 0 +/- 0% (normal) in Group 1, 10 +/- 8% (mild disability) in Group 2, and 27 +/- 24% in Group 3. Outcome in Group 3 dogs ranged from near-normal to comatose. After perfusion-fixation sacrifice, brain histopathologic damage scores correlated with insult time, as did ND scores. Deep hypothermia can allow 60-90 min of circulatory arrest with good neurologic recovery, even after a period of severe hemorrhagic shock. This technique may allow repair of otherwise lethal injuries and survival without brain damage.

Emergency cardiopulmonary bypass for resuscitation from prolonged cardiac arrest

After cardiac arrest (no flow) of more than approximately 5 minutes' duration, standard external cardiopulmonary resuscitation (CPR) basic, advanced, and prolonged life support (BLS, ALS, PLS) do not reliably produce cerebral and coronary perfusion pressures to maintain viability and achieve stable spontaneous normotension; nor do they provide prolonged control over pressure, flow, composition, and temperature of blood. Since these capabilities are often needed to achieve conscious survival, emergency closed-chest cardiopulmonary bypass (CPB) by veno-arterial pumping via oxygenator is presented in this review as a potential addition to ALS-PLS for selected cases. In six dog studies by the Pittsburgh group (n = 221; 1982 through 1988), all 179 dogs that received CPB after prolonged cardiac arrest (no flow) or after CPR (low flow) states had restoration of stable spontaneous circulation. The use of CPB enhanced survival and neurological recovery over those achieved with CPR-ALS attempts only. With CPB and standard intensive care, it was possible to reverse normothermic ventricular fibrillation (VF) cardiac arrest (no flow) of up to 15 minutes and to achieve survival without neurologic deficit; VF of 20 minutes to achieve survival but with neurologic deficit; and VF of 30 minutes to achieve transient restoration of spontaneous circulation followed by secondary cardiac death. CPB could restore stable spontaneous circulation after ice water submersion of up to 90 minutes. Other groups' laboratory and clinical results agree with these findings in general. Clinical feasibility trials are needed to work out logistic problems and to meet clinical challenges. Future possibilities for emergency CPB require further research and development.

Mild cerebral hypothermia during and after cardiac arrest improves neurologic outcome in dogs

We previously found mild hypothermia (34-36 degrees C), induced before cardiac arrest, to improve neurologic outcome. In this study we used a reproducible dog model to evaluate mild hypothermia by head cooling during arrest, continued with systemic cooling (34 degrees C) during recirculation and for 1 h after arrest. In four groups of dogs, ventricular fibrillation (no flow) of 12.5 min at 37.5 degrees C was reversed with cardiopulmonary bypass and defibrillation in less than or equal to 5 min, and followed by controlled ventilation to 20 h and intensive care to 96 h. In Study A we resuscitated with normotension and normal hematocrit; Control Group A-I (n = 12) was maintained normothermic, while Treatment Group A-II (n = 10) was treated with hypothermia. In Study B we resuscitated with hypertension and hemodilution. Control Group B-I (n = 12) was maintained normothermic (6 of 12 were not hemodiluted), while Treatment Group B-II (n = 10) was treated with hypothermia. Best overall performance categories (OPCs) achieved between 24 and 96 h postarrest were in Group A-I: OPC 1 (normal) in 0 of 12 dogs, OPC 2 (moderate disability) in 2, OPC 3 (severe disability) in 7, and OPC 4 (coma) in 3 dogs. In Group A-II, OPC 1 was achieved in 5 of 10 dogs (p less than 0.01), OPC 2 in 4 (p less than 0.001), OPC 3 in 1, and OPC 4 in 0 dogs. In Group B-I, OPC 1 was achieved in 0 of 12 dogs, OPC 2 in 6, OPC 3 in 5, and OPC 4 in 1 dog. In Group B-II, OPC 1 was achieved in 6 of 10 dogs (p less than 0.01), OPC 2 in 4 (p less than 0.05), and OPC 3 or 4 in 0 dogs. Mean neurologic deficit and brain histopathologic damage scores showed similar significant group differences. Morphologic myocardial damage scores were the same in all four groups. We conclude that mild brain cooling during and after insult improves neurologic outcome after cardiac arrest.