Effects of dichloroacetate in spinal stroke in the rabbit.

High levels of brain lactate may contribute to cellular death and dysfunction in acute cerebral ischemia. Although sodium dichloroacetate (DCA) has been shown to lower brain lactate in incomplete cerebral ischemia, functional outcome has not been assessed with DCA. We examined the effects of DCA treatment on functional neurologic outcome using a previously developed model for "spinal stroke" in the rabbit. Thirty male New Zealand white rabbits weighing 1.3-2.8 kg were studied. After anesthesia with 15-40 mg/kg pentobarbital IV, a laparotomy was performed and the aorta exposed. A metal clamp was placed on the aorta just distal to the left renal artery for 20 minutes and then removed. The abdominal wound was closed in two layers. Animals then received either 2cc normal saline (n = 15) or 300 mg/kg DCA in 2cc normal saline (n = 15) over 10 minutes. The animals were returned to their cages when awake and were examined at 24 hours, 48 hours, and 72 hours for neurologic assessment. The exams were performed by a blinded examiner who was unaware of the treatment given. A three point ambulatory score (0 = can't walk, 1 = walk but not hop, 2 = hopping) and a two point activity score (0 = inactive, 1 = active) were used. At 24 hours, 67% of the DCA-treated animals were actively moving about compared to only 27% of the controls (P = 0.03; Fisher Exact Test). Ten of fifteen control animals were unable to walk, while only five of fifteen DCA-treated animals were unable to walk (P = 0.07). Sixty percent of the DCA animals were able to hop compared to 27% of controls (P = 0.06). These results suggest that DCA can reduce morbidity from spinal cord ischemia in the rabbit.

Hemodynamic effects of naloxone in anaphylactic shock.

Recent reports suggest that endorphins may contribute to hemodynamic depression in septic and hemorrhagic shock. There is also evidence that reversal of endorphin effects with high dose naloxone may improve hemodynamic function and improve survival in shock states. The purpose of this study was to examine the effects of naloxone on hemodynamic parameters in anaphylactic shock. Anaphylactic shock was induced in sensitized rabbits with horse serum. Three minutes after serum challenge, rabbits were treated with a 3 mg/kg bolus of naloxone followed by a 3 mg/kg per h infusion (group I, n = 8), or by injection with an equal volume of saline (group II, n = 8). Cardiac output, blood pressure, heart rate and body temperature were monitored continuously for 60 min and the experiment was terminated. There was a significant increase in cardiac index in group I animals at 10 min (P less than 0.01) and 15 min (P less than 0.01). Stroke volume index was also higher in naloxone treated animals at 10 min and 15 min (P less than 0.05). Although mean blood pressure was higher in group I animals at all time intervals after naloxone was begun, the difference was statistically significant only at 60 min (P less than 0.05). Peripheral vascular resistance index was not significantly different for the two groups.

A continuous hemorrhage model of fatal hemorrhagic shock in swine.

We studied the effect of bleed rate on survival time and hemodynamics in a continuous hemorrhage model of fatal hemorrhagic shock in lightly anesthetized swine. Fasted immature swine (12-16 kg) were sedated with intramuscular (i.m.) ketamine, endotracheally intubated, anesthetized with halothane (0.75%), nitrous oxide, and oxygen, and then prepared for experimentation by placement of a pulmonary artery thermodilution catheter, femoral arterial and venous catheters, and by splenectomy. After instrumentation, halothane was discontinued and sedation was maintained with nitrous oxide and intravenous lorazepam. Thirty minutes later, the animals were bled continuously at 1.0 ml/kg per min (n = 8, Group I) or 1.25 ml/kg per min (n = 8, Group II) by a roller pump connected to the femoral arterial catheter. Hemodynamic parameters were recorded every 15 min until death occurred. Mean survival time was 50.2 +/- 3.0 min in Group I and 39.8 +/- 3.2 min in Group II (P less than 0.001). There was a stepwise decrease in blood pressure and cardiac index consistent with progressive hemorrhagic shock. This model results in reproducible survival times with small standard deviations. Although the animals are lightly anesthetized and the experiments are performed acutely, the hemodynamic responses and survival times observed are similar to those reported in previous studies of chronically instrumented, unanesthetized swine. This model may be more practical than unanesthetized, chronically instrumented swine models for evaluating the effects of various interventions on survival time and hemodynamics in acute hemorrhagic shock.

Case conference: complete heart block in a young man.

A previously healthy 32-year-old man presented to the ED in complete heart block. Ischemic, infectious, and inflammatory conditions were considered in the differential diagnosis. Management options for complete heart block, the etiology of heart block in young adults, and treatment guidelines are reviewed.

A comparative study of the percutaneous versus intraoral technique for mental nerve block.

OBJECTIVE: Mental nerve block is frequently used to aid repair of facial lacerations; both percutaneous and intraoral approaches to blocking this nerve are used, but have never been compared. The authors compared the two techniques for pain of administration and effectiveness of anesthesia. METHODS: A prospective, randomized, single-blind, crossover study was conducted using ten healthy volunteers aged 22 to 33 years. Patients having prior experience with mental nerve blocks, lidocaine allergy, active oral/facial infection, or previous facial fractures were excluded. Bilateral mental nerve blocks were done using intraoral technique on one side and percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Subjective and objective pain (visual-analog scale), efficacy (anesthesia of lower lip), time to onset, and duration of anesthesia were evaluated. RESULTS: The intraoral technique was subjectively less painful than the percutaneous approach in nine of ten subjects (p = 0.02). Scores on the visual-analog pain scale were significantly lower for the intraoral technique (p = 0.03). Intraoral injection produced lower-lip anesthesia in 10/10 subjects versus 7/10 for percutaneous (p = 0.25). Times to onset (approximately 1-2 minutes) and durations of anesthesia (approximately one hour) were similar for the two techniques. CONCLUSION: The intraoral approach to the mental nerve block with adjunctive topical anesthesia was subjectively and objectively less painful than the percutaneous approach without adjunctive anesthesia. While the intraoral approach had a greater efficacy of lower-lip anesthesia and a longer duration of action, these differences were not statistically significant.

Comparison of intraoral and percutaneous approaches for infraorbital nerve block.

OBJECTIVE: The infraorbital nerve block is frequently used during repair of facial lacerations; both percutaneous and intraoral approaches are used. The authors compared the two techniques for pain of administration and anesthetic effectiveness. METHODS: A prospective, randomized, single-blind, crossover study was conducted using 12 healthy volunteers, aged 25-41 years. No patient had prior experience with infraorbital nerve anesthesia, lidocaine allergy, active oral/facial infection, or previous facial fractures. Bilateral infraorbital nerve blocks were done using the intraoral technique on one side and the percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Pain of injection, anesthetic efficacy (anesthesia of upper lip), time to anesthetic onset, and duration of anesthesia were evaluated. RESULTS: By visual-analog pain scale scores, there was less pain by the intraoral approach, although this difference did not achieve significance (p = 0.08). Overall, nine of the 12 subjects considered the intraoral technique less painful than the percutaneous approach (p = 0.14). The intraoral approach produced upper-lip anesthesia in 12 of 12 subjects, versus nine of 12 for the percutaneous technique (p = 0.25). The duration of anesthesia was longer with the intraoral approach (1.6 +/- 0.8 hours versus 0.9 +/- 0.4 hours) than with the percutaneous approach (p = 0.04). The two techniques were similar in times to anesthetic onset. CONCLUSION: The intraoral approach to the infraorbital nerve block after adjunctive topical anesthesia appeared at least as effective in producing upper-lip anesthesia as the percutaneous approach without adjunctive topical anesthesia. Although the volunteers subjectively preferred the intraoral approach and visual-analog pain scores were lower for this approach, these differences did not achieve statistical significance. The intraoral approach was associated with a longer duration of upper-lip anesthesia.

Electrocardiographic ST-segment elevation: the diagnosis of acute myocardial infarction by morphologic analysis of the ST segment.

UNLABELLED: Acute myocardial infarction (AMI) is one of many causes of ST-segment elevation (STE) in emergency department (ED) chest pain (CP) patients. The morphology of STE may assist in the correct determination of its cause, with concave patterns in non-AMI syndromes and non-concave waveforms in AMI. OBJECTIVES: To determine the impact of STE morphologic analysis on AMI diagnosis and the ability of this technique to separate AMI from non-infarction causes of STE. METHODS: The electrocardiograms (ECGs) of consecutive ED adult CP patients (with three serial troponin I determinations) were interpreted in two-step fashion by six attending emergency physicians (EPs): 1) the determination of STE by three EPs followed by 2) STE morphologic analysis (either concave or non-concave) in those patients with STE. The impact of STE morphology analysis was investigated in the identification of AMI and non-AMI causes of STE. Acute myocardial infarction was diagnosed by abnormal serum troponin I values (>0.1 mg/dL) followed by a rise and fall of the serum marker; STE diagnoses of non-AMI causes were determined by medical record review. Interobserver reliability concerning STE morphology was determined. Study inclusion criteria included at least three troponin values performed in serial fashion no more frequently than every three hours, initial ED ECG, ED diagnosis, and final hospital diagnosis. RESULTS: Five hundred ninety-nine CP patients were entered in the study, with 171 (29%) individuals having STE on their ECGs. Of the 171 patients who had STE, 56 had AMI, 50 had unstable angina pectoris (USAP), and 65 had non-coronary final diagnoses. Forty-nine patients had non-concave STE, 46 with AMI and three with USAP; no patient with a non-coronary diagnosis had a non-concave STE morphology. The sensitivity and specificity of the non-concave STE morphology for AMI diagnoses were 77% and 97%, respectively; the positive and negative predictive values for non-concave morphology in AMI diagnoses were 94% and 88%, respectively. Interobserver reliability in the STE morphology determination revealed a kappa coefficient of 0.87. CONCLUSIONS: A non-concave STE morphology is frequently encountered in AMI patients. While the sensitivity of this pattern for AMI diagnosis is not particularly helpful, the presence of this finding in adult ED chest pain patients with STE strongly suggests AMI. This technique produces consistent results among these EPs.

Technical considerations in the selection of a personal emergency response system.

It is the purpose of this report to provide an internal review of the personal response system (PRS) in our hospital. Our system is coordinated by volunteers without emergency physician supervision. It uses antiquated equipment in the client's homes and emergency response center. Calls are answered by individuals who have not been trained as dispatchers, and who do not record pertinent performance data. The technical considerations involved in the selection and operation of an ideal PRS system are described.

Threshold, enzymatic, and pathologic changes associated with prolonged transcutaneous pacing in a chronic heart block model.

Previous studies have shown that 30 minutes of transcutaneous cardiac pacing (TCP) can induce mild, clinically insignificant myocardial damage. Longer use of TCP may cause more severe cardiac damage which might result in an increase in the capture threshold for subsequent transvenous cardiac pacing (TVP). To assess this possibility, we examined changes induced by TCP in a canine chronic heart block model. Heart block was induced in conditioned dogs (n = 8) by His bundle ablation. Seven to 10 days after induction of heart block, six animals were paced. Cardiac enzymes were drawn before pacing and at 4, 24, 48, and 72 hours after pacing. Although there was a significant rise in CK at 4 and 24 hours (P less than 0.05), there was no detectable rise in the MB fraction in any of the paced animals. There was no elevation of LDH after pacing, although three animals did develop an LDH1/LDH2 isoenzyme flip indicative of myocardial damage. Animals were sacrificed 72 hours after pacing and their hearts were examined for gross and microscopic changes. The hearts of the paced animals revealed subendocardial, subepicardial, and perivascular areas of basophilic degeneration involving less than 1% of the myocardium in four of six animals. No evidence of such damage was seen in two heart-blocked control animals not undergoing pacing. TVP and TCP capture thresholds assessed before and after a 60-minute TCP pacing period showed no significant change. Hence, use of TCP for a 60-minute period prior to TVP appears to be a safe emergency pacing technique.

Bicarbonate therapy for the cardiovascular toxicity of amitriptyline in an animal model.

The beneficial hemodynamic effects of sodium bicarbonate as treatment for tricyclic antidepressant poisoning were investigated in an animal model. Seven adult dogs (17.5 to 20 kg) were poisoned by an intravenous infusion of amitriptyline. Toxicity was defined as a doubling of the initial QRS width. A continuous infusion was used to maintain toxicity for 30 minutes after which 44.5 mEq of sodium bicarbonate was administered intravenously. Five of the animals survived to completion of the experiment. Three of the surviving animals developed dysrhythmias. All dysrhythmias ceased within one minute of administration of sodium bicarbonate. An increase in mean blood pressure (P less than .05) and serum pH (P less than .05) and a decrease in mean QRS width (P less than .05) occurred following administration of sodium bicarbonate. The maintenance of toxicity for 30 minutes suggests that this model can be used for future studies of tricyclic antidepressant poisoning.

Closed thoracic cavity lavage in the treatment of severe hypothermia in human beings.

Life-threatening hypothermia can be treated by active and passive rewarming techniques, the treatment of choice being partial cardiopulmonary bypass. The use of closed thoracic cavity lavage has been evaluated in animals, but no formal presentations in human beings have been reported. We report two cases in which rapid rewarming in severe hypothermia was accomplished when cardiopulmonary bypass was not available.

Hemodynamic and metabolic effects of ethanol in canine hemorrhagic shock.

Ethanol has been reported to cause myocardial suppression, exaggerated hypotension, and increased mortality in various animal models of hemorrhagic shock. Previous studies have not used a fixed-volume graded hemorrhage model and have not monitored cardiac output or metabolic parameters such as serum glucose and lactate levels. We studied hemodynamic and metabolic changes after administration of ethanol in a 50% graded hemorrhage model in conditioned, anesthetized beagles after orogastric ethanol loading. The hemorrhage was done over a 60-min period followed by a 90-min stabilization period. The ethanol group (n = 6) had significantly higher heart rates during the stabilization period. Mean arterial pressures (MAP) were lower in the ethanol group during the stabilization period. The change from baseline MAP 30 min after hemorrhage was -31% in the control group and -53% in the ethanol group (P less than .05 using Wilcoxon ranked sum test). Serum glucose and lactate levels were higher in the ethanol group. These results indicate that ethanol impairs hemodynamics and alters glucose and lactate metabolism in dogs in the fixed-volume graded hemorrhage model. The effect of these changes on morbidity and mortality remains to be determined.

Consideration for primary angioplasty: impact on the door-to-drug time in AMI patients ultimately treated with thrombolytic agent.

The objective of this study was to determine if consideration for percutaneous transluminal coronary angioplasty (PTCA) delays administration of thrombolytic therapy in acute myocardial infarction (AMI) patients. Retrospective medical record review of patients ultimately diagnosed with AMI who presented to the ED with chest pain and ST segment elevation on the electrocardiogram; these patients also received acute reperfusion therapy (PTCA or thrombolytic agent). AMI was diagnosed by abnormal elevations in the creatinine phosphokinase MB fraction. The study period covered 2 years (July 1, 1994 to June 30, 1996) in a university hospital ED with an annual volume of 60,000 patient-visits. The use of reperfusion therapies, time intervals, and times of presentation were recorded. Patients were divided into two groups based on cardiac catheterization laboratory (CATH) availability: (group I, CATH currently in operation, Monday to Friday, 7 am to 7 pm and group II, CATH currently not in-operation, all other times). Fifty-two patients with AMI met entry criteria. Patients were treated with thrombolytic therapy in 25 cases; PTCA in 27 cases. Patients received thrombolytic agents within statistically equivalent time intervals regardless of the period of presentation; time to thrombolytic therapy for group I patients was 38 +/- 16 minutes compared with 36 +/- 26 minutes for group II patients (P =. 891). A trend toward significance was noted in the use of PTCA compared with thrombolytic agent; Group I patients were more often treated with PTCA (19) compared with group II patients (11, P =.067). Patients were more rapidly treated with PTCA during CATH operation; the mean time to PTCA for group I patients was 73.5 minutes compared with PTCA for group II patients with 107.8 minutes (P =.033). The consideration for PTCA did not significantly delay the administration of thrombolytic therapy at the study site institution. PTCA was initiated more rapidly in patients presenting with AMI during hours of CATH operation.

Emergency department use of transcutaneous pacing for cardiac arrests.

Transcutaneous cardiac pacing is a rapid technique for pacing the heart using skin electrodes to pass repetitive electrical impulses through the thorax. This paper reports the results of transcutaneous pacing in a series of 52 emergency department patients. Patients were selected for pacing if they were unconscious and in asystole (30 patients) or unconscious with a pulseless or hemodynamically ineffective bradycardia (22 patients). In all cases, transcutaneous pacing was attempted after initial resuscitative drug therapy failed. Of the 26 patients with successful ECG capture, 14 were initially in asystole, 11 were initially in a pulseless bradycardia, and one had a hemodynamically ineffective bradycardia. Of the eight patients developing a pulse, four developed a measurable BP. The four patients who developed a measurable BP were young (ages 22 to 39 yr) and only one had an underlying cardiac etiology for his cardiac arrest. No patient survived to be discharged from the hospital. Twenty-five of the 52 patients also had a transvenous pacemaker inserted, with successful electrical capture in five of the patients. Only one of the transvenously paced asystolic patients subsequently developed a BP. There were no patients successfully paced transvenously who were not successfully paced transcutaneously.

Developments in transcutaneous and transthoracic pacing during bradyasystolic arrest.

Transthoracic cardiac pacing historically has been relegated to the role of the technique of last resort in treating cardiac arrest. Recent studies have shown that this technique has a high rate of successful electrical capture, but often without mechanical activity. Survival rates have been shown to be dismal when the technique is used late in cardiac arrest. Results of several recent studies of patients paced by the transcutaneous technique have suggested that electrical capture can often be rapidly obtained in asystolic or pulseless bradycardic patients. Even though electrical capture can occur late in a cardiac arrest, the development of mechanical activity with survival is rare. Survivors generally have been treated early in their arrest and have had hemodynamically ineffective bradycardias. These findings suggest that rapid initiation of transcutaneous pacing in patients with Stokes-Adams attacks, increasing heart block associated with myocardial ischemia, postdefibrillation asystole, or pulseless bradycardia may improve survival. However, victims of a prolonged cardiac arrest whose myocardium has irreversibly ceased to function mechanically are unlikely to benefit from any pacing technique.

Transcutaneous and transvenous cardiac pacing for early bradyasystolic cardiac arrest.

Emergency transcutaneous cardiac pacing was studied prospectively in 19 patients presenting to the emergency department with a bradyasystolic cardiopulmonary arrest of 20 minutes duration or less. Pacing was initiated when conventional advanced cardiac life support (including atropine administration) and a fluid challenge failed to restore a pulse. Seventeen patients also had placement of transvenous pacemaker electrodes for cardiac pacing. Transcutaneous cardiac pacing rapidly established a blood pressure in the two patients who for clinical reasons did not receive a transvenous pacemaker. Five patients were transcutaneously paced within five minutes of cardiac arrest (Group 1) and the remaining 14 were paced between five and 20 minutes following cardiac arrest (Group 2). Two of the Group 1 patients were admitted and subsequently recovered full neurological and prearrest cardiac function. Fewer Group 2 patients developed a blood pressure (P = .04), and there were no patients with full neurologic recovery in this group (P = .06). Similar results were found for transvenous cardiac pacing; there was a greater incidence of a palpable pulse and measurable blood pressure (P = .05 for both) in the Group 1 patients than in the Group 2 patients. No difference in clinical outcome was noted between the two pacing techniques. These results support the concept that cardiac pacing must be initiated early if the outcome of bradyasystolic cardiac arrest is to be altered.

A hemodynamic model for anaphylactic shock.

The treatment of cardiovascular collapse and anaphylactic shock is largely empiric. A simple animal model was developed to evaluate the hemodynamic alterations in anaphylaxis. Eight adult New Zealand white rabbits of both sexes were studied. All animals weighed 3.8 kg to 5.3 kg. Sensitization was accomplished with a 2-mL subcutaneous dose of horse serum followed in two days with a 2-mL intravenous (IV) dose. At least 14 days elapsed after the IV dose before a 1-mL challenge dose of horse serum was given. On the day of the challenge dose, a femoral arterial catheter, arterial temperature probe, and right atrial catheter were placed under methoxyflurane anesthesia. The temperature probe was positioned in the aortic arch. The methoxyflurane was discontinued and the only sedation given during the shock phase was IV diazepam (0.1 mg/kg to 0.5 mg/kg). At least 30 minutes after methoxyflurane was discontinued, the challenge dose of horse serum was given through the right atrial catheter. Before and during the shock phase cardiac rhythm, arterial pressure, and intravascular temperature were monitored continuously. Cardiac outputs (CO) were performed by a thermodilution technique using 0.8 mL room temperature saline injectate through the right atrial catheter. Temperature deflection of the aortic probe was recorded and cardiac output was calculated. After giving the challenge dose, CO was measured at three, five, ten, 15, 25, 35, 45, and 60 minutes. All eight animals showed a significant (P less than .0005) fall in CO, cardiac index, and blood pressure within three minutes. The fall in cardiac index was 50% or more in all animals. Two animals died as a result of shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiologic assessment of transvenous pacemaker placement during CPR.

During an 18-month period we prospectively studied 36 emergency department patients who had a transvenous pacing catheter placed without fluoroscopic or ECG guidance during closed-chest massage. Transvenous pacing was instituted at a mean elapsed time of 35 minutes (range, ten to 80 minute) after the onset of cardiac arrest, including prehospital and ED care times. Catheter tip position was assessed using postresuscitation or postmortem chest radiographs. Pacing catheters were fixed in the position of electrical capture prior to radiographs; when capture was never achieved, the catheter was fixed at 35 cm from the point of insertion. Position of the catheter tip on radiographs was as follows: right ventricle, ten of 36 patients; right atrium, 18 of 36; and other location, eight of 36. Ectopic catheter tip positions included inferior vena cava (four), pulmonary artery (one), hepatic vein (two), and internal jugular vein (one). Catheter tip position within the right ventricle correlated with a significantly higher incidence of electrical capture when compared with other catheter tip locations (P less than .004). There was a significantly higher incidence of successful placement into the right ventricle when an internal jugular, rather than a subclavian venous, access route was used (P less than .004). Only one of 36 patients was resuscitated successfully; none lived to be discharged from the hospital. Misplacement of the catheter tip may contribute to the poor success rate of transvenous pacing during CPR. The internal jugular vein may be the access site of choice when transvenous pacing is attempted during chest compressions.(ABSTRACT TRUNCATED AT 250 WORDS)