Scott Syverud

Succinylcholine-assisted intubations in prehospital care

Although endotracheal intubation is considered the optimal technique for airway management in critically ill patients, performance of this task in the prehospital setting is at times difficult due to increased masseter muscle tone, vocal cord spasm, or patient combativeness. Use of short-acting paralyzing agents by paramedics to facilitate intubation in these situations is an uncommon practice. We report the recent experience of an emergency medical service system that has used succinylcholine (SUX) for more than ten years. We reviewed prehospital patient intubations for two years; 215 patients were intubated by paramedics without the use of SUX and 95 patients were intubated with the use of SUX. The patient group intubated with SUX was characterized by a greater percentage of women (48% vs 35%; P less than .05), a higher mean Glasgow Coma Scale score (8.6 vs 3.4), fewer intubations for cardiac arrest (3% vs 81%), and more hospital survivors (58% vs 24%; P less than .005). The groups were not different with respect to mean age or frequency of trauma. Paramedics chose to use SUX in 69% of nonarrested patients requiring intubation. SUX-assisted intubation was used most often for the indications of airway protection and respiratory distress. Review of hospital records showed no difference between the groups for frequency of either aspiration pneumonia or mechanical ventilation in patients surviving to hospital admission. No patient receiving SUX required emergency cricothyrotomy, nor was esophageal intubation noted in either group. Succinylcholine-assisted intubation was used safely and selectively by the paramedics in this EMS system to permit airway control and ventilation of patients with more difficult intubations.

Prehospital use of neuromuscular blocking agents in a helicopter ambulance program

We prospectively studied the use of succinylcholine chloride and pancuronium bromide by the physician/nurse flight team of our hospital-based helicopter ambulance service. Patients who received these agents at the scene of an accident (prehospital group, n = 39) were compared with patients who were paralyzed by the flight team in the emergency department of transferring hospitals (control group, n = 35). By protocol, succinylcholine was used primarily for endotracheal intubation and pancuronium for prolonged paralysis after endotracheal intubation. Seventy-four patients received one or both agents. Overall, 61 of 74 patients had intracranial pathology as their primary diagnosis (82%). Endotracheal intubation was the primary indication for paralysis in the majority of patients (67 of 74), although intracranial pressure control, ventilation, agitation control, and seizure control were frequent secondary indications. Prior intubation attempts had failed in 40 of 74 patients (54%). After paralysis, intubation was successful in 68 of 71 patients (96%). Serious complications (ie, dysrhythmia requiring drug therapy) occurred in three patients but resolved with appropriate therapy in each case. Minor complications (ie, dysrhythmia not requiring drug therapy, histamine flush, infiltrated IV line) occurred in 18 patients. There was no significant difference in successful intubation or complication rate between the prehospital and control group. Paralysis allowed airway stabilization in a significant number of critically ill patients who could not otherwise be endotracheally intubated, with a lower incidence of complications than has been previously reported for ED patients. These results suggest that neuromuscular blocking agents can be used safely and effectively at accident scenes by a physician/nurse team.

Prehospital trial of emergency transcutaneous cardiac pacing.

A prospective alternate-day controlled trial of prehospital transcutaneous cardiac pacing (PACE) of hemodynamically significant bradycardia and asystole was undertaken. All patients had a Glasgow coma scale score of 12 or less. Patients in the control group (n = 101) received standard advanced cardiac life support (ACLS) care. Patients in the pacing group (n = 101) were to receive PACE in addition to standard ACLS treatment; 89 patients were actually paced. The two groups were comparable in terms of age, sex, presenting rhythm, and mean times to cardiopulmonary resuscitation (CPR) and ACLS. For the 144 patients in whom the time of arrest could be estimated, the mean times to CPR and ACLS were 5.3 +/- 4.0 and 10.9 +/- 7.1 min, respectively. For the 65 paced patients in whom the time of arrest could be estimated, the mean time from arrest to pacing was 21.8 +/- 8.8 min (range 2 to 43). Multivariate analysis of outcome variables (presentation to emergency department with a pulse, admission to the hospital, and discharge from the hospital) revealed that an initial rhythm of ventricular tachycardia or fibrillation and a short time to ACLS were correlated with a favorable outcome (p less than .05; logistic regression analysis). A short time to PACE was associated with admission to the hospital (p = .20; logistic regression analysis). The use of a stand-alone transcutaneous pacing device in the prehospital arrest setting was associated with generally long times until pacing and did not appreciably improve outcome. Use of PACE in patients demonstrating prehospital bradycardia without neurologic impairment remains to be evaluated.

Improved outcome with early blood administration in a near-fatal model of porcine hemorrhagic shock

Current recommendations for the preoperative management of hemorrhagic shock include the initial infusion of 2 L of isotonic crystalloid regardless of the severity of hemorrhage. While this approach may be adequate for patients who experience only mild to moderate hemorrhagic insults, it has never been tested in a clinically relevant model of severe life-threatening hemorrhage. The authors used a porcine model of rapidly fatal hemorrhage with a reproducible and relevant physiologic end-point, the absence of vital signs, to test the hypothesis that even brief delays in blood replacement may result in higher mortality rates and worsen hemodynamic and metabolic responses to hemorrhage. Twenty-four immature swine (11-17 kg) were bled continuously at a decelerating rate until the following criteria were met: (1) respiratory arrest, (2) a pulse pressure of 0 and, (3) a slowing of cardiac electrical activity of 15% or more. Resuscitation was begun 1 minute later. The animals were randomly assigned to one of three resuscitation regimens. Group A (n = 8) received shed blood at a rate of 3 mL/kg/min for 10 minutes followed by normal saline (NS) at a rate of 3 mL/kg/min for 10 minutes. Group B (n = 8) received NS at a rate of 3 mL/kg/min for 10 minutes followed by shed blood at a rate of 3 mL/kg/min for 10 minutes. Group C, controls, (n = 8) received NS at a rate of 3 mL/kg/min for 20 minutes. Animals were observed for 30 minutes after resuscitation or until death. Mortality was 25%, 37.5%, and 100% for groups A, B, and C, respectively (P < .05 for group C versus group A or B).(ABSTRACT TRUNCATED AT 250 WORDS)

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 = cant 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.

Prehospital Transcutaneous Cardiac Pacing for Symptomatic Bradycardia

We studied patients with symptomatic bradycardia to determine the importance of presenting hemodynamic status and prehospital transcutaneous cardiac pacing (TCP) upon patient survival. Of 51 patients with witnessed cardiovascular decompensation and initial bradycardia, 27 (53%) received TCP. There were no significant differences between the paced patients and those without TCP for mean times from collapse until cardiopulmonary resuscitation, paramedic arrival and a paceable rhythm, or from paramedic arrival until a paceable rhythm. Overall, emergency department arrival with a palpable pulse (26% in paced vs 13% in nonpaced group; P = 0.20) and survival to hospital discharge (15% in paced vs 0% nonpaced group; P = 0.07) tended to be better for the paced group. No patient without a palpable pulse on paramedic arrival survived to leave the hospital. Of patients with a palpable pulse upon paramedic arrival, survival to hospital discharge was greater for the paced group (80% in paced vs 0% in nonpaced group; P = 0.024). TCP appears to be most beneficial in those patients with bradycardia who have a palpable pulse when first seen.

Intravenous fluid therapy in the prehospital management of hemorrhagic shock: improved outcome with hypertonic saline?6% dextran 70 in a swine model

The small quantities of 7.5% hypertonic saline (HTS) in 6% Dextran 70 (DEX 70; Travenol Laboratories, Deerfield, IL) required to produce marked improvement in tissue perfusion may make it an ideal solution for the prehospital management of hypotensive trauma patients. This study shows that the initial treatment of porcine hemorrhagic shock with 7.5% HTS/6% DEX 70 results in significantly improved hemodynamics and higher survival rates than those seen in animals treated with normal saline. These results are very encouraging and dictate the need for evaluation in human trials.

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.

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.