Sevoflurane-N2O versus propofol/isoflurane-N2O during elective surgery using the laryngeal mask airway in adults.

STUDY OBJECTIVES: To compare a sevoflurane-nitrous oxide (N2O) general anesthetic technique with a standard technique of propofol for induction, and isoflurane-N2O for maintenance. DESIGN: Prospective, randomized study. SETTING: University-affiliated tertiary-care hospital. PATIENTS: 62 adults undergoing elective surgery using the laryngeal mask airway (LMA). INTERVENTIONS: Patients received either the standard technique of propofol for induction and isoflurane-N2O for maintenance (controls) or sevoflurane-N2O for both induction and maintenance of general anesthesia. MEASUREMENTS: Induction and emergence times, heart rate, blood pressure, oxygen saturation, and end-tidal carbon dioxide were recorded. MAIN RESULTS: Time to loss of consciousness was faster after propofol (mean +/- SEM: 51 +/- 3 sec) than after sevoflurane-N2O (85 +/- 10 sec; p < 0.05). Ready for surgery times, were however, similar between groups (10 +/- 1 vs. 11 +/- 1 min, respectively). All patients in the control group had apnea after LMA insertion compared with 4 patients in the sevoflurane-N2O group (p < 0.05). Heart rate was lower 5 and 10 minutes after LMA insertion in the sevoflurane-N2O group (69 +/- 3 and 66 +/- 3 bpm) versus the control group (81 +/- 3 bpm and 74 +/- 3 bpm, p < 0.05). After cessation of anesthetic gases, there were no differences in time to LMA removal, eye opening, or exiting the operating room (OR) between the control group (7, 8, and 10 min) and sevoflurane-N2O groups (7, 8, and 12 min, respectively). The majority of patients in both groups (92% to 97%) rated their anesthetic experience as excellent or good. CONCLUSIONS: Sevoflurane-N2O and propofol provided comparable conditions for LMA insertion. Sevoflurane-N2O was not associated with a faster return of consciousness or faster time to exit the OR compared with isoflurane-N2O.

Total intravenous anesthesia with a propofol-ketamine combination during coronary artery surgery.

OBJECTIVE: To evaluate the cardiovascular effects of a propofol-ketamine combination in patients undergoing coronary artery surgery. DESIGN: Prospective, randomized study. SETTING: Tertiary care teaching hospital, single center. PARTICIPANTS: Seventy-eight adult patients. INTERVENTIONS: Patients were randomly allocated to receive propofol-ketamine for induction and maintenance of anesthesia (n = 36) or fentanyl-enflurane (controls, n = 42). MEASUREMENTS AND MAIN RESULTS: Hemodynamics and other variables were recorded during and after surgery and for 24 hours in the intensive care unit. Before cardiopulmonary bypass (CPB), there was similar incidence of treatment for hypotension (42% of patients in both groups), tachycardia (propofol-ketamine, 6%; controls, 5%), and myocardial ischemia (propofol-ketamine, 3%; controls, 12%). In the propofol-ketamine group, there was a decreased requirement for inotropic agents after CPB (22% of patients) compared with controls (49% of patients; p = 0.02). There was a reduced incidence of myocardial infarctions (creatine kinase myocardial band >133 U/L) in the propofol-ketamine group compared with the control group (0% v 14%; p = 0.02; Fisher's exact test). Patients in the propofol-ketamine group were more likely to have their tracheas extubated within 8 hours of arrival in the intensive care unit compared with controls (33% v 7%; p = 0.01; Cochran-Mantel-Haenzel test). CONCLUSIONS: The propofol-ketamine combination was associated with a similar incidence of pre-CPB hypotension and ischemia, a decreased need for inotropes after CPB, an earlier time to tracheal extubation, and a reduced incidence of myocardial infarctions compared with controls.

Oxygen consumption in the early postinjury period: use of continuous, on-line indirect calorimetry.

OBJECTIVE: To determine the patterns of oxygen consumption (Vo2) using indirect calorimetry (IC) for the first 24 hrs after serious blunt traumatic injury. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit of a Level 1 trauma center. PATIENTS: Sixty-six mechanically ventilated patients with blunt traumatic injury and Injury Severity Score >15. INTERVENTIONS: IC for 24 hrs postinjury. Patients were resuscitated to standard parameters of perfusion. MEASUREMENTS AND MAIN RESULTS: Mean patient age was 50.1+/-18.7 yrs with a mean Injury Severity Score 30.7+/-11.3). Mean Vo2 for all patients for the 24-hr study period was 168.5+/-29.5 mL/min/m2. The level of Vo2 was not related to Injury Severity Score, the number or combination of organ systems injured, or to the use of vasoactive agents. Patients >65 yrs of age had significantly lower Vo2 (P = .0038) compared with patients < or =50 yrs. Vo2 did not change over time after resuscitation to normal parameters of perfusion. Mean Vo2 was 156.5+/-63.2 mL/min/m2 in patients who developed multiple organ dysfunction, and 172.4+/-33.3 mL/min/m2 in those who did not develop multiple organ dysfunction (p = .16). CONCLUSIONS: Seriously injured patients are hypermetabolic in the early postinjury period. The level of Vo2 is unrelated to injury severity or number of organ systems involved. Elderly patients can be expected to have lower levels of Vo2. Vo2 does not change significantly in response to resuscitation to normal parameters of perfusion. Vo2 measured by IC did not predict the development of multiple organ dysfunction.

The failure of negative pressure rewarming (Thermostat) to accelerate recovery from mild hypothermia in postoperative surgical patients.

UNLABELLED: The Thermostat device (Aquarius Medical Corp., Phoenix, AZ) is used in a new technique to accelerate recovery from hypothermia by mechanically distending blood vessels in the hand, thereby increasing transfer of exogenous heat to the body core. We evaluated the use of the Thermostat device in patients with mild postoperative hypothermia (< 36 degrees C). We studied adult patients undergoing elective surgery, general anesthesia, and neuromuscular blockade. Patients with an initial postoperative tympanic membrane temperature < 36 degrees C were randomized into two groups: 1) Thermostat, which consisted of a hypothermia warming mitt/seal and thermal exchange chamber for 60 min, and 2) conventional treatment, which consisted of warm blankets and/or radiant heat. Of the 191 patients enrolled, 60 (31%) developed hypothermia and were randomized to receive the Thermostat (n = 30) or conventional methods (n = 30). Fourteen patients in the Thermostat group and 17 patients in the conventional group rewarmed to 36 degrees C before discharge from the recovery room (P is not significant). There were no differences in vital signs, rewarming time, time to discharge from the recovery room, or postoperative temperature between groups. We conclude that patients with mild postoperative hypothermia rewarmed in a similar fashion, regardless of whether the Thermostat or conventional methods were used. IMPLICATIONS: We found that a commercially available negative pressure rewarming device (Thermostat; Aquarius Medical Corp., Phoenix, AZ) was not effective in accelerating rewarming in postoperative hypothermic surgical patients after general anesthesia.

Evaluation of tracheal intubation difficulty in patients with cervical spine immobilization: fiberoptic (WuScope) versus conventional laryngoscopy.

BACKGROUND: The WuScope is a rigid, fiberoptic laryngoscope designed to facilitate tracheal intubation without the need for head extension. The study evaluated the WuScope in anesthetized patients with neck immobilization. METHODS: Patients were randomized to one of two groups: those receiving fiberoptic laryngoscopy (WuScope, n = 43) and those receiving conventional laryngoscopy (Macintosh blade, n = 44). Manual in-line stablization of the cervical spine was done during intubation. Seven parameters of intubation difficulty were measured (providing an intubation difficulty scale score): number of operators, number of attempts, number of techniques, Cormack view, lifting force, laryngeal pressure, and vocal cord position. RESULTS: Successful intubation occurred in 95% of patients in the fiberoptic group and in 93% of patients in the conventional group. There were no differences in number of attempts. In the fiberoptic group, 79% of patients had an intubation difficulty scale score of 0, representing an ideal intubation: that is, one performed by the first operator on the first attempt using the first technique with full glottic visualization. Only 18% of patients in the conventional group had an intubation difficulty scale score of 0 (P < 0.001). More patients had Cormack grade 3 or 4 views with conventional than with fiberoptic laryngoscopy (39 vs. 2%, P < 0.001). Intubation times in patients with one attempt were slightly longer in the fiberoptic (median, 25th-75th percentiles: 30, 23-53 s) compared with the conventional group (24, 17-30 s, P < 0.05). Corresponding times in patients requiring > one attempt were 155 (range, 112-201) s and 141 (range, 95-186) s in the fiberoptic and conventional groups, respectively (P value not significant). CONCLUSIONS: Compared with conventional laryngoscopy, tracheal intubation using the fiberoptic laryngoscope was associated with lower intubation difficulty scale scores and better views of the laryngeal aperture in patients with cervical imnmobilization. However, there were no differences in success rates or number of intubation attempts.

Rocuronium versus vecuronium during fentanyl induction in patients undergoing coronary artery surgery.

OBJECTIVE: To evaluate the neuromuscular, ventilatory, and cardiovascular effects of rocuronium and vecuronium. DESIGN: Randomized, prospective, blinded study. SETTING: Tertiary care teaching center, single institution. PARTICIPANTS: Patients undergoing elective coronary artery bypass graft procedure. INTERVENTIONS: Patients received rocuronium, 1.0 mg/kg (n = 17), or vecuronium, 0.15 mg/kg (n = 15), during fentanyl induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Measures consisted of time to visual loss of orbicularis oculi twitches in response to facial nerve stimulation, ease of mask ventilation, hemodynamics, need for vasoactive drugs, and tracheal intubating conditions. Median time to twitch loss was faster (p < 0.05) after rocuronium (60 s) than after vecuronium (>84 s). Within 45 seconds, only 3 of 17 patients in the rocuronium group had moderate-to-severe difficulty with mask ventilation versus 12 of 15 patients in the vecuronium group (p < 0.05). Tracheal intubating conditions were excellent in all patients after rocuronium. In the vecuronium group, intubating conditions were excellent in 46%, good in 27%, and poor in 27% (p < 0.05 vrocuronium). Patients receiving vecuronium were more likely to require ephedrine and phenylephrine for hypotension (10/15 patients v 5/17 patients for rocuronium, p < 0.05). There were no clinically important differences in hemodynamic variables, oxygen metabolism, or myocardial ischemia between groups. CONCLUSION: During narcotic induction of anesthesia, rocuronium was associated with lower requirement for vasopressors, faster onset of neuromuscular blockade, and better conditions for mask ventilation and tracheal intubation compared with vecuronium.

Preventing hypothermia: convective and intravenous fluid warming versus convective warming alone.

STUDY OBJECTIVE: To test the hypothesis that warming intravenous (i.v.) fluids in conjunction with convective warming results in less intraoperative hypothermia (core temperature < 36.0 degrees C) than that seen with convective warming alone. DESIGN: Prospective, randomized study. SETTING: University affiliated tertiary care teaching hospital. PATIENTS: 61 ASA physical status, I, II, and III adults undergoing major surgery and general anesthesia with isoflurane. INTERVENTIONS: All patients received convective warming. Group 1 patients received warmed fluids (setpoint 42 degrees C). Group 2 patients received room temperature fluids (approximately 21 degrees C). MEASUREMENTS AND MAIN RESULTS: Lowest and final intraoperative distal esophageal temperatures were higher (p < 0.05) in Group 1 (mean +/- SEM: 35.8 +/- 0.1 degrees C and 36.6 +/- 0.1 degrees C) versus Group 2 (35.4 +/- 0.1 degrees C and 36.1 +/- 0.1 degrees C, respectively). Compared with Group 1, more Group 2 patients were hypothermic at the end of anesthesia (10 of 26 patients, or 38.5% vs. 4 of 30 patients, or 13%; p < 0.05). After 30 minutes in the recovery room, there were no differences in temperature between groups (36.7 +/- 0.1 degrees C and 36.5 +/- 0.1 degrees C in Groups 1 and 2, respectively). Intraoperative cessation of convective warming because of core temperature greater than 37 degrees C was required in 33% of Group 1 patients (vs. 11.5% in Group 2; p = 0.052). CONCLUSIONS: The combination of convective and fluid warming was associated with a decreased likelihood of patients leaving the operating room hypothermic. However, average final temperatures were greater than 36 degrees C in both groups, and intergroup differences were small. Care must be taken to avoid overheating the patient when both warming modalities are employed together.

Warming intravenous fluids reduces perioperative hypothermia in women undergoing ambulatory gynecological surgery.

UNLABELLED: We evaluated whether warming i.v. fluids resulted in less hypothermia (core temperature < 35.5 degrees C) compared with room-temperature fluids. Thirty-eight adult outpatients undergoing elective gynecological surgery of > 30 min were randomized to two groups: fluid warming at 42 degrees C or control (room temperature fluids at approximately 21 degrees C). All patients received general anesthesia with isoflurane, tracheal intubation, standard operating room blankets and surgical drapes, and passive humidification of inspired gases. Tympanic membrane (core) temperatures were measured at baseline and at 15-min intervals after induction. The incidence of shivering and postoperative requirement for meperidine and/or radiant heat were evaluated. Core temperatures were lower in the control compared with the warm fluid group at the end of surgery (35.6 +/- 0.1 degrees C vs 36.2 +/- 0.1 degrees C; P < 0.05). More patients had final core temperature < 35.5 degrees C in the control compared with the warm fluid group (35% vs 0%; P < 0.05). There were no differences in time to discharge from the postanesthesia care unit or the incidence of shivering between the groups. We conclude that fluid warming, in conjunction with standard heat conservation measures, was effective in maintaining normothermia during outpatient gynecological surgery; however, there was no improvement in patient outcome. IMPLICATIONS: Women who received i.v. fluid at body temperature had significantly higher core temperatures during and after outpatient gynecological surgery compared with women who received i.v. fluids at the temperature of the operating room.

Oxygen delivery is an important predictor of outcome in patients with ruptured abdominal aortic aneurysms.

OBJECTIVE: The purpose of this study was to evaluate the relation of oxygen delivery (DO2) to the occurrence of multiple organ dysfunction (MOD) in patients with ruptured abdominal aortic aneurysms (AAA). SUMMARY BACKGROUND DATA: Patients with ruptured AAA are at high risk for the development of MOD and death. Previous reports of high-risk general surgical patients have shown improved survival when higher levels of DO2 are achieved. METHODS: Hemodynamic data were collected at 4-hour intervals on 57 consecutive patients (mean age, 70.5 years) who survived 24 hours after repair of infrarenal ruptured AAA. Patients were resuscitated to standard parameters of perfusion (pulse, blood pressure, urine output, normal base deficit). MOD was determined based on six organ systems. Standard parametric (analysis of variance, t tests) and nonparametric (chi square, Wilcoxon) tests were used to compare hemodynamic data, red blood cell requirements, colon ischemia, and organ failure for patients with and without MOD. RESULTS: Patients who developed MOD had a significantly lower cardiac index and DO2 for the first 12 hours; the difference was most significant at 8 hours. Logistic regression analysis demonstrated that the strongest predictors of MOD were DO2, early onset of renal failure, and total number of red blood cells transfused. CONCLUSIONS: DO2 is an earlier and better predictor of MOD after ruptured AAA than previously identified risk factors. Failure to achieve a normal DO2 in the first 8 hours after repair is strongly associated with the development of MOD and a high mortality. Strategies to restore normal DO2 may be useful to improve outcome in these high-risk patients.

Heat conservation vs convective warming in adults undergoing elective surgery.

PURPOSE: To determine the relative efficacy of heat conservation and convective warming in maintaining perioperative normothermia, (central temperature > or = 36 degrees C). METHODS: Thirty-seven patients undergoing elective gynaecological, orthopaedic, or general surgery scheduled to last two hours were prospectively studied. Patients were randomized to one of two groups. Group 1 patients received heat conservation with reflective blankets (Thermadrape, Vital Signs, Inc., Totowa, NJ) applied preoperatively and warmed i.v. fluids (Hotline SIMS Level I Technologies, Inc, Rockland, MA), Group 2 patients received convective warming (BairHugger, Augustine Medical Inc., Eden Prairie, MN) after induction of anaesthesia and i.v. fluids at room temperature. All patients received general anaesthesia with isoflurane. Tympanic membrane and forearm-fingertip skin temperature gradients were measured perioperatively at 15 min intervals. RESULTS: Central temperature decreased after induction to a minimum level of 35.9 +/- 0.1 degrees C in group 1 and 36.0 +/- 0.1 degrees C in group 2 and then increased towards pre-induction values in group 2, and were higher (P < 0.05) than in group 1: 95% group 2 patients had central temperature > or = 36.0 degrees C at the end of surgery (vs 69% of group 1, P < 0.05). During the first 30 min in PACU, central temperatures were higher in group 1 than in group 2 (36.8 +/- 0.1 degrees C vs 36.2 +/- 0.2 degrees C, P < 0.05). After 60 min, central temperatures were similar (36.8 degrees C). The incidence of shivering and degree of peripheral cutaneous vasoconstriction were also similar. CONCLUSION: Patients receiving convective warming were more likely to leave the operating room normothermic, and had higher central temperatures during the first 30 min in the recovery room. The intergroup temperature differences were small, and by 60 min, had disappeared.

Taping methods and tape types for securing oral endotracheal tubes.

PURPOSE: To evaluate tapes and taping methods with respect to the minimum force required to dislodge endotracheal tubes (ETTs). METHODS: A simulated face model consisting of a section of PVC pipe was used. The ETT was attached to a piezo-electric force transducer and pullout force was manually applied in a vertical, right or left direction. Five tape types were tested: Curity, Leukosilk, Hy.tape, Leukopore, and Transpore, Seven taping methods were used to secure the ETT. The methods differed with respect to tape width and whether the tape was split along its longitudinal axis. Each taping condition was replicated 20 times (7 methods x 5 tapes x 3 directions) for a total of 2100 pullout tests. RESULTS: Minimum forces to dislodge ETTs were higher (P < 0.05) with Curity tape (mean +/- SD; 135 +/- 75 N) than with the other tapes (Leukosilk: 93 +/- 51 N, Hy.tape: 78 +/- 34 N, Leukopore: 47 +/- 32, and Transpore: 37 +/- 23 N). The most secure taping method was achieved by taping the ETT, using 2.5 cm wide Curity tape, in a circumferential fashion to both the upper and lower borders of the simulated mouth opening, and reinforcing these tapes with two strips applied longitudinally across the borders of the mouth opening (method 7). Taping methods which involved splitting the tape along its longitudinal axis resulted in lower minimal pullout forces whenever the pullout force was directed towards the side of attachment (P < 0.05 vs right and vertical direction). CONCLUSION: There are differences in ETT pullout forces and mechanisms of dislodgement depending on taping method and tape type.

Intubating conditions and neuromuscular block after divided dose mivacurium or single dose rocuronium.

PURPOSE: To evaluate the tracheal intubating conditions and neuromuscular blocking characteristics of divided dose mivacurium or single dose rocuronium. METHODS: Thirty-two patients undergoing elective surgery were studied. Anaesthesia was with propofol 2 mg.kg-1, followed by an infusion of 150 micrograms.kg-1.min.1. Patients were randomized to receive either mivacurium-0.15 mg.kg-1 followed 30 sec later by 0.1 mg.kg-1, or rocuronium- 0.9 mg.kg-1, followed 30 sec later by placebo. Tracheal intubating conditions were assessed 90 sec after the initial dose of relaxant by an anaesthetists who was unaware of patient group. The electromyographic (EMG) response of the first dorsal interosseus muscle to ulnar nerve train-of-four was measured. RESULTS: Successful tracheal intubation was performed in all patients after both mivacurium and rocuronium. Intubating conditions (jaw relaxation, open visible vocal cords) were judged to be good-excellent in all but one patient before insertion of the tracheal tube. However, patients receiving mivacurium were more likely to experience coughing and bucking after tracheal tube insertion (10/16 patients) than those receiving rocuronium (3/16 patients, P < 0.05). No patient in the rocuronium group experienced moderately vigorous coughing and bucking after insertion of the tracheal tube vs six patients in the mivacurium group (P < 0.05). Time to 10 and 25% recovery of neuromuscular function was faster (P < 0.05) after divided dose mivacurium (20 +/- 1 and 23 +/- 1 min, respectively) than after rocuronium (45 +/- 5 and 57 +/- 8 min, respectively). CONCLUSION: The results suggest that, during conditions of the study, divided dose mivacurium is not recommended for a 90-sec tracheal intubation in patients where moderate coughing and bucking is deemed unacceptable.

Comparison of esophageal, tympanic, and forehead skin temperatures in adult patients.

STUDY OBJECTIVE: To compare esophageal, tympanic membrane, and forehead skin temperatures in patients undergoing elective surgeries. DESIGN: Prospective clinical study. SETTING: Operating room and postanesthesia care unit of a tertiary care teaching hospital. PATIENTS: 40 adult ASA status I, II and III patients requiring anesthesia and surgery. INTERVENTION: Application of crystalline thermometry strips to the forehead of patients. MEASUREMENTS AND MAIN RESULTS: Concurrent forehead skin, tympanic membrane, and lower esophageal temperatures were measured and compared. The overall bias between esophageal and skin temperatures was 0.3 degrees C, between tympanic membrane and skin was 0.5 degrees C, and between esophageal and tympanic membrane was -0.1 degrees C The limits of agreement (precision) between esophageal and skin temperatures were: -1.64 degrees C to +2.32 degrees C, between esophageal and tympanic membrane were: -1.02 degrees C to +0.74, and between tympanic membrane and skin were: -1.48 degrees C to +2.52 degrees C. There was no significant relation between the change in skin temperature and change in esophageal temperature, whereas there was a weak linear relation between change in skin temperature and change in tympanic membrane temperature (y = -0.03 + 0.09, r = 0.12). CONCLUSION: There was a lack of precision between the clinically accepted measurements (lower esophageal and tympanic membranes and the skin temperature measurement. The data suggest that forehead skin temperature is not interchangeable with standard core temperature measurements, and that sole reliance on the forehead skin measurement in the perioperative setting could adversely affect patient care.

Prospective, randomized comparison of the Flotem Iie and Hotline fluid warmers in anesthetized adults.

STUDY OBJECTIVE: To compare the fluid warming capabilities of the Hotline and Flotem IIe devices in surgical patients, and whether warming intravenous (i.v.) fluids with the Hotline device resulted in less hypothermia and less need for other warming methods compared with the Flotem IIe device. STUDY DESIGN: Part 1. Prospective, nonrandomized. Part 2. Prospective, randomized. SETTING: Teaching hospital, tertiary care center. PATIENTS: Part 1. 24 adult patients undergoing elective surgery. Part 2. 49 adult patients scheduled for major elective orthopedic or gynecologic surgery of greater than 2 hours' duration with general anesthesia. INTERVENTIONS: Part 1. Insertion of sterile in-line thermistors along the path of fluids delivered using the Hotline or Flotem device. Part 2. Patients were randomly assigned to receive i.v. fluids via the Hotline (n = 21) or Flotem IIe (n = 18) warmers. Intervention for core hypothermia [lower esophageal temperature (Teso) less than 35.5 degrees C], was with forced air warming. Intervention for postoperative shivering was with meperidine by a nurse who was blinded to the treatment group. MEASUREMENTS: Part 1. Temperature of infused fluids before and after the warmer (T in and T out) and before the fluid entered the patient after insertion of a standard 84 cm extension set having a stopcock for injection of medications (T distal). Part 2. Tympanic (Ttym) was recorded before induction of anesthesia (baseline) and at 15-minute intervals after induction. Teso was recorded at 15-minute intervals after induction. The maximum intraoperative Ttym decline from baseline (delta Ttym max) was calculated. MAIN RESULTS: Part 1. Flow rates were between 1 and 33 ml/min. T out and T distal (mean +/- SEM) of fluids infused through the Hotline device were warmer compared with those infused via the Flotem IIe device (Hotline T out: 35.7 +/- 0.1 degrees C and Hotline T distal: 33.4 +/- 0.2 degrees C vs. Flotem IIe T out: 28.9 +/- 0.2 degrees C and Flotem IIe T distal: 28.3 +/- 0.2 degrees C; p < 0.001 between warmers). Part 2. Maximal decrease in Ttym from preoperative baseline (before intervention) was greater in the Flotem IIe compared with the Hotline group (delta Ttym max = -1.4 +/- 0.1 vs. -0.9 +/- 0.1 degree C, p = 0.01). Five patients in the Flotem IIe group required forced air warming for treatment of hypothermia versus none in the Hotline group (p < 0.01). Postoperatively, five patients in the Flotem IIe group required treatment with meperidine for severe shivering versus one patient in the Hotline group (p < 0.05). CONCLUSIONS: The Hotline device delivered fluids to the patient at consistently warmer temperatures compared with the Flotem IIe device during actual clinical conditions. This was associated with maintenance of near normal core temperatures throughout the procedure in the Hotline group, and a decreased need for interventions such as forced-air warming and treatment for severe shivering.

Simulated clinical evaluation of conventional and newer fluid-warming devices.

The purpose of the study was to evaluate the ability of five commercially available devices utilizing a variety of heat exchange technologies to deliver normothermic (37 degrees C) fluids. Conditions of slow (6.5 mL/ min), moderate (13-25 mL/min), and rapid (gravity and pressure driven flows, roller clamp wide open) infusion were simulated. Fluid temperatures were measured using rapid response thermistors after the fluid exited the heat exchanger (T outlet) and before delivery to the patient intravenously (IV) (T distal). Devices tested were the FW537, H1000, Hotline, BairHugger, and Flotem IIe. Fluids tested were crystalloid at room temperature and red cells diluted with saline (11-19 degrees C). At slow and moderate flows, T distal of crystalloid was between 35.3 and 37.9 degrees C for Hotline at 42 degrees C, 33.8 and 37.7 degrees C for H1000 at 42 degrees C, 29.4 and 34.2 degrees C for BairHugger, 26.1 and 31.5 for Flotem IIe, and 23.8 and 32.1 for FW537 at 42 degrees C. With gravity and pressure driven flows, T distal of crystalloid were 39.0 and 38.9 for H1000 at 42 degrees C, 38.7 and 38.4 degrees C for FW537 at 42 degrees C, 34.7 and 28.9 degrees C for Hotline at 42 degrees C, 29.2 and 24.2 degrees C for BairHugger, and 29.7 and 24.2 degrees C for Flotem. In conclusion, only the H1000 at 42 degrees C was effective at delivering normothermic fluids at all clinically relevant flow rates. The Hotline at 42 degrees C was effective at slow and moderate flow, whereas the FW537 was effective only at rapid flow.

Desflurane is not associated with faster operating room exit times in outpatients.

STUDY OBJECTIVE: To determine the influence of anesthetic technique and primary drug on operating room (OR) exit time (time between end of surgery until time patient exists the OR) after addition of desflurane to the hospital formulary. DESIGN: Prospective study. SETTING: Ambulatory surgery unit of a university hospital. PATIENTS: 1,568 outpatients requiring anesthesia. INTERVENTIONS: Addition of desflurane to the hospital formulary, and substitution of desflurane vaporizers for enflurane vaporizers in the ambulatory surgery unit. MEASUREMENTS AND MAIN RESULTS: The following information was recorded for all anesthetic encounters over a six-month time interval: demographics, duration of surgery, primary anesthetic technique, primary anesthetic drug, and exit times. General anesthesia was used in 907 patients [desflurane: 209 patients, isoflurane: 429 patients, halothane: 192 patients, propofol: 72 patients, other intravenous (i.v.): 5 patients], major conduction anesthesia (spinal and epidural) in 43 patients, peripheral nerve blocks in 90 patients, and i.v. sedation in 528 patients. The exit time was significantly greater ( < 0.05) in patients who received general anesthesia (mean +/- SEM 14 +/- 0.2 min) compared with spinal/epidural (8 +/- 0.7 min), nerve blocks (8 +/- 0.4 min) and i.v. sedation (7 +/- 0.2 min). Exit times were longer in older patients receiving general anesthesia (exit time = 12.3 + 0.04 x age, SE = 6.7 min, p < 0.0009), whereas exit times were shorter in older individuals receiving i.v. sedation (exit time = 8.97 - 0.038 x age, SE = 3.6 min, p < 0.0001). For patients receiving i.v. sedation, exit times were shorter as duration of surgery increased (exit time = 7.86 - 0.015 x duration of surgery, SE = 3.6 min, p < 0.0002). Primary anesthetic drug did not affect exit times. CONCLUSION: Regional anesthesia and i.v. sedation were associated with faster OR exit times compared with general anesthesia. Despite desflurane's shorter elimination kinetics and recovery characteristics, use of this drug did not result in shorter exit times.

The effect of fiberoptic bronchoscopy on cerebral hemodynamics in patients with severe head injury.

STUDY OBJECTIVE: Concerns exist about the effect of flexible fiberoptic bronchoscopy (FFB) on intracranial pressure (ICP). We studied the effect of FFB on cerebral hemodynamics in patients with severe head injury. DESIGN: Prior to FFB, patients were anesthetized and muscle relaxants were given as necessary to eliminate coughing. Comparisons were made of mean arterial pressure (MAP), ICP, and cerebral perfusion pressure (CPP) prior to, during, and after FFB, as well as comparisons of mean cerebral hemodynamic values in an 8-hour period before and after FFB. Observations were made of changes in neurologic status post-FFB. SETTING: Surgical intensive care unit of Level 1 Trauma Center. PATIENT POPULATION: Fifteen patients with severe head injury in whom ICP was monitored and who required FFB for diagnosis of nosocomial pneumonia or treatment of lobar collapse. RESULTS: Pre-FFB ICP averaged 14.3 mm Hg (range, 6 to 26 mm Hg). During FFB, patients experienced a mean increase in ICP of 13.5 mm Hg above basal values (p = 0.0001). At peak ICP, MAP increased from a baseline of 92.3 mm Hg (SD +/- 16.1) to 111.5 mm Hg (+/- 13.9). Mean CPP was 83.7 mm Hg at peak ICP (range, 52 to 121 mm Hg), a 14.0% increase over baseline. The ICP and MAP returned to basal levels following bronchoscopy. No patient had a clinically significant increase in ICP or demonstrated any deterioration in Glasgow Coma Scale score or neurologic examination findings post-FFB. CONCLUSIONS: Although FFB causes an increase in ICP in patients with severe head injury, MAP also rises, and an adequate CPP is maintained. The ICP returns to basal levels after the procedure. When properly performed, FFB does not adversely affect neurologic status in patients with severe head injury.

Comparison of fluid warmer performance during simulated clinical conditions.

The study evaluated the warming ability and flow rates associated with four fluid warming devices during pressure driven infusion and during wide open gravity driven roller clamp infusion. Warmers tested were the Astotherm, Flotem IIe, Level 1 System 250 and a modified cardioplegia heat exchanger. Fluids tested were crystalloid, red cells diluted with 200 ml, 0.9% saline, and undiluted red cells. The volume of fluid and outlet temperatures (point where i.v. tubing would be attached to the patient) were measured for each fluid and compared among warmers for each flow rate condition. For pressure driven infusion of red cells and crystalloid, the System 250, and modified heat exchanger delivered warmer fluids (33-35 degrees C) at higher flow rates (160-740 ml.min-1) than the Astotherm and Flotem (23-31 degrees C, 44-268 ml.min-1, P < 0.05). For gravity driven infusion, the System 250 delivered the warmest fluids (33-36 degrees C, P < 0.05) compared with the modified heat exchanger (29-35 degrees C), Astotherm (26-32 degrees C) and Flotem (26-27 degrees C). In conclusion, the modified heat exchanger and System 250 were moderately effective (outlet temperature > 32 degrees C) in warming crystalloid and red cells at pressure driven flow rates. Only the System 250 warmed red cells > 35 degrees C at gravity driven flow rates. The Flotem and Astotherm were not effective in warming rapidly infused solutions. None of the warmers tested was able to deliver fluids at normothermia (> 36.5 degrees C).

Evaluation of different methods of securing intravenous catheters: measurement of forces during simulated accidental pullout.

The purpose of the study was to compare the relative effectiveness of several combinations of tapes and taping methods with respect to the force required to pull out intravenous catheters. A simulated forearm model consisting of a section of firm PVC pipe was used for the first and second series of experiments. In the third experiment, one method of taping catheters was compared in the PVC model and in volunteers. Pullout forces were measured with a force transducer and recorded on paper. In the first experiment, catheters secured with Curity tape resisted pullout to a greater extent than those with Transpore tape and provided approximately twice the force advantage (P < 0.05). In the second experiment using Curity tape, minimum forces to dislodge the catheters were (means +/- SD) 53 +/- 13, 82 +/- 13, 113 +/- 29, 124 +/- 24, 176 +/- 29 and 141 +/- 46 N, for methods 1-6, respectively. In the third series, the minimum pullout forces were higher for Curity than with Transpore tape for both the human and simulated PVC forearm surfaces (63 +/- 11 and 55 +/- 12 N vs 52 +/- 7 and 44 +/- 12 N, P < 0.01), and the pullout forces were higher for the simulated vs. the human skin surface for both tape types (P < 0.01). Compared with Curity tape, Transpore tape was more likely to fail by tape fracture in both the simulated and human skin surfaces (P < 0.05). The data suggest that there are important differences in pullout forces and mechanisms of dislodgement depending on taping method and tape type.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of tape type and of skin preparation on the force required to dislodge angiocatheters.

The study evaluated the effects of different techniques used to secure intravenous (i.v.) catheters. An angiocatheter attached to standard i.v. tubing was taped to human forearm using a standard taping method. A calibrated piezoelectric force transducer was attached to the i.v. tubing. The force applied along the longitudinal axis to pull out the taped catheter was measured and recorded on paper. Three tape types, Curity, Leukopor and Transpore, were evaluated alone, with benzoin skin pretreatment and with mastisol pretreatment. A randomized 3 x 3 block design with 20 replications per block was utilized, and a total of 180 pullout tests were performed on two adult volunteers. Without pretreatment, the forces required to dislodge catheters were (means +/- SEM) 46 +/- 2, 37 +/- 2 and 38 +/- 2 Newtons for Curity, Leukopor and Transpore tape, respectively. Corresponding values for mastisol pretreatment (64 +/- 1, 64 +/- 3 and 52 +/- 3 Newtons) were greater (P < 0.05) for each tape compared with benzoin (54 +/- 3, 53 +/- 2 and 40 +/- 2 Newtons) and no pretreatment. The most frequent failure mode for Transpore tape was by tape fracture, for Curity tape was by separation from the skin of tape and catheter as a single unit, and for Leukopor tape was by catheter separation while tape remained attached to skin (P < 0.001). The data suggest that the application of mastisol prior to taping i.v. catheters with Curity or Leukopor tape helps to minimize the risk of accidental dislodgement.