Influence of the mode of ventilation on ketamine/xylazine requirements in rabbits.

OBJECTIVE: To evaluate the effect of the mode of mechanical ventilation (MV) on the dose of intravenous anesthetic during 3 hours of ketamine/xylazine anesthesia. STUDY DESIGN: Prospective laboratory study. ANIMALS: Sixty-one adult male New Zealand White rabbits. METHODS: Rabbits were anesthetized (ketamine/xylazine 35 + 5 mg kg(-1), IM), the trachea was intubated and randomized to four groups - (1) CMV-1 (n = 14), ventilated with traditional conventional volume-cycled MV [V(T) = 12 mL kg(-1), RR = 20, positive end-expiratory pressure (PEEP) = 0 cmH(2)O]; (2) CMV-2 (n = 13), ventilated with a modern lung-protective regimen of volume-cycled MV (V(T) = 6 mL kg(-1), RR = 40, PEEP = 5 cmH(2)O); (3) HFPV (n = 17) ventilated with high-frequency percussive ventilation [high-frequency oscillations (450 minute(-1)) superimposed on 40 minute(-1) low-frequency respiratory cycles, I:E ratio = 1:1], oscillatory continuous positive airway pressure (CPAP) of 7-10 cmH(2)O, and demand CPAP of 8-10 cmH(2)O. (4) A fourth group, spontaneously ventilating (SV, n = 17), was anesthetized, intubated, but not ventilated mechanically. FiO(2) in all groups was 0.5. Anesthesia was maintained at a surgical plane by IV administration of a ketamine/xylazine mixture (10 + 2 mg kg(-1), as necessary) for 3 hours after intubation. Total dose of xylazine/ketamine administered and the need for yohimbine to facilitate recovery were quantitated. RESULTS: The total dose of xylazine/ketamine was significantly higher in the HFPV and SV groups compared with CMV-1 (p < 0.01). Fewer animals required yohimbine to reverse anesthesia in the HFPV than CMV-1 group (p < 0.05). CONCLUSIONS: The HFPV mode of MV led to higher doses of ketamine/xylazine being used than the other modes of MV. CLINICAL RELEVANCE: In rabbits, anesthetic dose for the maintenance of anesthesia varied with the mode of MV used. Investigators should be aware of the possibility that changing the mode of ventilation may lead to an alteration in the amount of drug required to maintain anesthesia.

Radial pulse character relationships to systolic blood pressure and trauma outcomes.

BACKGROUND: Patient measurements that do not require monitoring equipment may be the only way to evaluate casualties in austere conditions to determine treatment and transport priority. Objective. To test the hypothesis that palpable pulse characteristics in the radial artery would estimate systolic blood pressure (SBP) and predict outcome in trauma patients. METHODS: Data were analyzed from the medical records of 342 trauma patients ranging from 18 to 50 years of age. Prehospital data were collected by helicopter emergency medical personnel at the scene of the injury. Based on radial pulse character, patients were divided into normal (n = 313) and weak (n = 29) groups. Those whose medical records did not describe pulse characters were not considered. Differences in SBP, mortality, and medical interventions between the radial-pulse-character groups were evaluated. RESULTS: The SBP taken at the scene was a mean of 26 mm Hg lower in those patients with weak radial pulse characters (102 mm Hg versus 128 mm Hg). Similarly, the lowest mean SBPs recorded in the field between the normal- and weak-pulse-character groups were 112 mm Hg and 99 mm Hg, respectively. Patient mortality increased with weak pulse character such that the mortality rats were 3% for the normal-pulse-character group and 29% for the weak-pulse-character-group (odds ratio = 15.2). CONCLUSIONS: These preliminary data suggest that a weak radial pulse may be an acceptable method for initial rapid evaluation of trauma patients. This simple and rapid method of pulse evaluation should be considered for the triage of trauma patients in field conditions with limited instrumentation.