Alfred C. Pinchak

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.

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.

Effect of injection site on circulation times during cardiac arrest.

Cardiopulmonary resuscitation requires effective, prompt drug administration. In order to analyze Advanced Cardiac Life Support (ACLS) recommendations for site of drug administration, we studied dye circulation times after central, femoral, and peripheral venous injection during both closed and open chest CPR using a canine arrest model. Measurements of circulation times were made after injection of indocyanine green dye at femoral, central, and peripheral venous sites. Circulation times during closed chest CPR were 62.7 +/- 19.6 sec after central injection, 86.6 +/- 23.5 sec after femoral injection, and 93.6 +/- 17.9 sec after peripheral injection (p less than .001). During closed chest CPR, peak dye concentration after central injection was significantly higher than that after peripheral injection (4.0 +/- 1.3 vs. 3.1 +/- 0.8 mg/L, p less than .01). Circulation times were significantly shorter during open chest CPR with times again shortest after central injection. This animal model suggests that prompt drug delivery during CPR is enhanced by central venous injection of medication. There appears to be no advantage in femoral over peripheral injection.

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

We evaluated whether warming IV fluids resulted in less hypothermia (core temperature <35.5[degree sign]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[degree sign]C or control (room temperature fluids at approximately 21[degree sign]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[degree sign]C vs 36.2 +/- 0.1[degree sign]C; P < 0.05). More patients had final core temperature <35.5[degree sign]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 IV fluid at body temperature had significantly higher core temperatures during and after outpatient gynecological surgery compared with women who received IV fluids at the temperature of the operating room. (Anesth Analg 1998;87:37-41)

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 Trademark, BairHugger Registered Trademark, 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 Trademark 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 Registered Trademark, 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 Trademark at 42 degrees C, 29.2 and 24.2 degrees C for BairHugger Registered Trademark, 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 Trademark at 42 degrees C was effective at slow and moderate flow, whereas the FW537 was effective only at rapid flow. (Anesth Analg 1996;82:517-24)

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.

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.

Randomized Prospective Comparison of Forced Air Warming Using Hospital Blankets versus Commercial Blankets in Surgical Patients

Background The purpose of this study was to evaluate the efficacy of an experimental approach to forced air warming using hospital blankets or a Bair Hugger warming unit (Augustine Medical Inc., Eden Prairie, MN) to create a tent of warm air. Methods Adult patients undergoing major surgery were studied. Patients were randomized to receive forced air warming using either a commercial Bair Hugger blanket (control group, n = 44; set point, 43°C) or standard hospital blankets (experimental group, n = 39; set point, 38°C). Distal esophageal temperatures were monitored. Patients were contacted the following day regarding any problems with the assigned warming technique. Results Surface area covered was 36 ± 12% (mean ± SD) in the experimental group and 40 ± 10% in the control group. Final temperatures at the end of surgery were similar between groups: experimental, 36.2 ± 0.6°C; control, 36.4 ± 0.7°C. A similar number of patients had esophageal temperature less than 36°C at the end of surgery in both groups (experimental, 12 of 39 [31%]; control, 12 of 44 [27%]). The majority of patients were satisfied with their anesthetic and warming technique: experimental, 38 of 39 patients; control, 44 of 44 patients. There were no thermal injuries. Conclusions Standard hospital blankets heated to 38°C forced air were equally as effective as commercial blankets heated with forced air at 43°C. However, based on concerns expressed by the manufacturer, this experimental technique should not be used until further safety evaluation has been undertaken.

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 iv 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° C) at higher flow rates (160–740 ml · min− 1) than the Astotherm and Flotem (23–31° C, 44–268 ml · min− 1, P< 0.05). For gravity driven infusion, the System 250 delivered the warmest fluids (33–36° C, P < 0.05) compared with the modified heat exchanger (29–35°C), Astotherm (26–32°C) and Flotem (26–27° C). In conclusion, the modified heat exchanger and System 250 were moderately effective (outlet temperture >32°C) in warming crystalloid and red cells at pressure driven flow rates. Only the System 250 warmed red cells >35° 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° C).RésuméCe travail évalue la capacité de réchauffement et les débits produits par quatre appareils de réchauffement destinés à la perfusion sous pression et à la perfusion par gravité. Les réchauffeurs sont l’Astotherm, le Flotem IIe, le Level 1 System 250 et une échangeur de chaleur de cardioplégie modifié. Les liquides étudiés sont les cristalloïdes, des hématies rouges dilués avec 200 ml, du physiologique 0,9% et des hématies non diluées. Le volume de liquide et la température à la sortie (au point d’attache de la tubulure au patient) sont mesurés pour chacun des liquides et comparés entre les réchauffeurs pour chacun des débits obtenus. Pour la perfusion sous pression des hématies et des cristalloïdes, le System 250 et l’échangeur de chaleur modifié fournissent des liquides plus chauds 03–35° C) à plus haut dédits (160–740 ml · min− 1, P < 0,05) que l’Asthotem et le Flotem (23–31°C, 44–268 ml · min− 1, P < 0,05). Pour les perfusions sous gravité, le System 250 fournit les liquides les plus chauds 33–36° C, P< 0,05) comparativement à l’échangeur modifié (29–35° C), l’Astotherm (26–32°C) et le Flotem (26–27°C). En conclusion, l’échangeur de chaleur modifié et le System 250 sont moyennement efficace (température à la sortie >32° C) pour réchauffer les cristalloïdes et les hématies à des débits contrôlés par la pression. Seul le System 250 réchauffe les hématies à plus de 35°C à des débits contrôlés par la gravité. Le Flotem et l’Astotherm sont inefficaces pour réchauffer des solutions perfusées rapidement. Aucun des réchauffeurs essayés ne fournit de liquides normothermiques (>36,5°C).

A comparison of venous blood gases during cardiac arrest

Previous reports have advocated the use of mixed venous blood gases to estimate arterial pH and as a reflection of tissue acid-based balance. However, true mixed venous samples are difficult to obtain during cardiac arrest as they require a pulmonary artery catheter. The purpose of this study was to determine whether central or femoral venous samples could be used in place of pulmonary artery samples. Blood gases from these sites were drawn at intervals during experimental cardiac arrest in dogs. The PO2, PCO2, and pH from the pulmonary artery samples were strongly correlated with those from the central venous (r = .93, .99, and .99, respectively) and from the femoral venous samples (r = .73, .93, and .97, respectively). There were no significant differences in the pulmonary artery, central, or femoral venous gases. This animal model suggests that femoral and central venous samples mirror true mixed venous blood gases from the pulmonary artery and could be used in their place.