Heat transfer coefficient: Medivance Arctic Sun Temperature Management System vs. water immersion.

BACKGROUND AND OBJECTIVE: To improve heat transfer, the Medivance Arctic Sun Temperature Management System (Medivance, Inc., Louisville, CO, USA) features an adhesive, water-conditioned, highly conductive hydrogel pad for intimate skin contact. This study measured and compared the heat transfer coefficient (h), i.e. heat transfer efficiency, of this pad (hPAD), in a heated model and in nine volunteers' thighs; and of 10 degrees C water (hWATER) in 33 head-out immersions by 11 volunteers. METHODS: Volunteer studies had ethical approval and written informed consent. Calibrated heat flux transducers measured heat flux (W m-2). Temperature gradient (DeltaT) was measured between skin and pad or water temperatures. Temperature gradient was changed through the pad's water temperature controller or by skin cooling on immersion. RESULTS: The heat transfer coefficient is the slope of W m-2/DeltaT: its unit is W m-2 degrees C-1. Average with (95% CI) was: model, hPAD = 110.4 (107.8-113.1), R2 = 0.99, n = 45; volunteers, hPAD = 109.8 (95.5-124.1), R2 = 0.83, n = 51; and water immersion, hWATER = 107.1 (98.1-116), R2 = 0.86, n = 94. CONCLUSION: The heat transfer coefficient for the pad was the same in the model and volunteers, and equivalent to hWATER. Therefore, for the same DeltaT and heat transfer area, the Arctic Sun's heat transfer rate would equal water immersion. This has important implications for body cooling/rewarming rates.

Anesthesia through a novel retrobulbar catheter provides perioperative pain control for 24 h after pars plana vitrectomy.

PURPOSE: The purpose of this study was to assess the retrobulbar catheter technique for perioperative pain control in pars plana vitrectomy. METHODS: One hundred consecutive pars plana vitrectomies (duration 20-220 minutes) in 88 patients (age range 37-88 years) were performed by the same surgeon under retrobulbar anesthesia using a commercially available retrobulbar needle. Initially, 7 ml of mepivacaine 2% were injected, a 28-gauge flexible catheter was introduced into the retrobulbar space and the needle was withdrawn. The catheter was removed 24 h after surgery. Intraoperatively and postoperatively, the patients were asked to rate pain using a numerical scale from 0 to 10. When pain was more than grade 3, 2 ml of a local anesthetic were re-injected through the catheter. RESULTS: A first re-injection was given intraoperative/y 53.0 +/- 34.6 minutes after the start of surgery during 35/100 procedures, and second and third injections were needed during 12 /100 and 4/100 procedures, respectively. The first postoperative re-injection was given 3.9 +/- 1.5 hours after the start of surgery in 54 procedures, and second and third injections were carried out in 35/100 and 10/100 procedures respectively. CONCLUSIONS: The results suggest that a temporary indwelling retrobulbar catheter allows long-lasting titratable local anesthesia during pars plana vitrectomy and titratable postoperative analgesia.

Intramuscular versus surface electromyography of the diaphragm for determining neuromuscular blockade.

We determined the neuromuscular blockade of 0.2 mg. kg(-1) mivacurium at the diaphragm by using two new methods of electromyographic (EMG) monitoring and compared it with acceleromyography of the orbicularis oculi (OO) and the corrugator supercilii (CS) muscle. After the induction of anesthesia in 15 patients undergoing gynecologic laparoscopic surgery, evoked EMG responses at the diaphragm were obtained by using skin electrodes at the back of the patient, placed lateral to T12/L1 or L1/L2, and a laparoscopically applied wire electrode inserted into the dorsolateral portion of the diaphragm. Acceleromyography at the right OO and the left CS was performed. The facial and phrenic nerves were stimulated transcutaneously (onset: every 10 s, offset: every 15 s, single twitch stimulation). Lag and onset time, peak effect, and clinical duration (time to reach 75% of control value and time to reach 90% of control value) were measured and the results were compared by using analysis of variance; P < 0.05 showed significant difference. Pearson's correlation test and the Bland-Altman test were used to compare the two diaphragmatic monitoring methods. Mean peak effects of >98% were reached at all sites. Onset times at diaphragm (skin, IM) were significantly (P < 0.005) shorter than at the CS or OO (100 +/- 14 s and 98 +/- 16 s vs 147 +/- 39 s, 185 +/- 38 s) without being statistically different between OO and CS. There was a good correlation of lag, onset time, time to reach 75% of control value, and time to reach 90% of control value (r = 0.8, 0.9, 0.8, and 0.75; P < 0.01) between the two diaphragmatic methods. Mean difference and limits of agreements are -2 +/- 15 s, 1 +/- 21 s, -1 +/- 2.3 min, and -2 +/- 3.4 min. We showed a shorter onset and clinical duration at the diaphragm in comparison with CS and OO. Two methods of EMG of the diaphragm correlated well and showed good comparability. The novel method of surface diaphragmatic EMG at the patient's back may be useful during routine clinical anesthesia.

Indwelling temporary retrobulbar catheter for long-lasting titratable local anesthesia.

OBJECTIVE: To evaluate an indwelling temporary retrobulbar catheter for repeatable injections of local anesthetics for long-lasting and titratable retrobulbar anesthesia in intraocular surgery. PARTICIPANTS: The prospective clinic-based study included 153 patients who underwent vitreoretinal surgery (n=111) or buckling procedures with cryocoagulation (n=34). The mean duration of surgery was 84.7 +/- 49.5 minutes (range, 25-310 minutes). Using commercially available retrobulbar needles with a diameter of 0.60 or 0.80 mm and a length of 38 mm, 5 mL of 2% mepivacaine hydrochloride was injected. Through the same needle, a 28-gauge commercially available flexible catheter was introduced into the retrobulbar space. The needle was withdrawn and the catheter was fixed. When the patients started to feel pain during surgery, 2 mL of mepivacaine hydrochloride was reinjected through the catheter. RESULTS: Ten to 240 minutes after the start of the operation, 96 patients needed an intraoperative reinjection of mepivacaine after which they felt comfortable again. Forty-two patients needed a second reinjection of mepivacaine 30 to 270 minutes after the start of the operation, and 13 patients needed a third reinjection 45 to 145 minutes after the start of surgery. Removal of the catheter after surgery was unremarkable. No infections were observed. Microbiologic examination results of the catheter tip were negative for organisms. Diplopia or other motility problems were not detected. Introduction and fixation of the catheter took less than 5 minutes in all patients. CONCLUSIONS: An indwelling temporary retrobulbar catheter for repeatable intraoperative injections of local anesthetics is simple, effective, and useful, and in comparison with general anesthesia, it is a time-saver for long-lasting and titratable local anesthesia in intraocular surgery. Arch Ophthalmol. 2000;118:996-1000

Determination of eicosanoid and cytokine production in salvaged blood, stored red blood cell concentrates, and whole blood.

STUDY OBJECTIVE: To determine the production of the eicosanoids prostaglandin 2 (PGE2) and thromboxane 2 (TxB2) and the cytokines interleukin 1 beta (IL-1-beta) and interleukin 6 (IL-6) in whole blood (WB), unfiltered red blood cell (RBC), and filtered RBC concentrates, and salvaged blood. DESIGN: Prospective study. SETTING: University hospital of Erlangen. PATIENTS: 32 healthy volunteers and 14 ASA physical status I, II, and III radical prostatectomy patients (mean age 65 yrs). INTERVENTIONS: Sixteen WB units and 16 RBC units (divided into 16 filtered and unfiltered units each) were taken from 32 volunteers. Fourteen salvaged RBC units were obtained from the 14 radical prostatectomy patients. Sixteen WB units were stored for 35 days. From the 16 WB donations, RBC concentrates (PAGGS-M) were prepared. The RBC concentrates were halved, one half had its leukocytes removed at day 0; both halves were stored for 49 days. Salvaged blood (n = 14) was stored up to 2 hours during surgery and then retransfused. MEASUREMENTS AND MAIN RESULTS: Immediately at the start of the study, in all blood units (WB, RBC filtered, and RBC unfiltered units) at days 0 and 21, and at the end of the storage period (WB: 35 days, RBC concentrates: 49 days) and in the salvaged RBC units, the following parameters were measured: PGE2, TxB2, IL-1-beta, IL-6, hematocrit, platelet number, leukocytes, blood volume, and hemoglobin. During storage, different levels of PGE2, TxB2, IL-1-beta, IL-6 for WB, filtered RBC concentrates, and unfiltered RBCs were found. The higher levels of PGE2, TxB2, IL-1-beta, and IL-6 were found in the WB and RBC salvaged units than the filtered RBCs or unfiltered RBC units. There was no statistically significant difference between WB and salvaged RBCs. Higher levels of leukocytes and platelets were found in WB units and salvaged RBCs as compared to filtered or unfiltered RBCs. CONCLUSIONS: The eicosanoid and cytokine levels in the salvaged, filtered RBC, unfiltered RBC, and WB units stayed within physiological limits, suggesting that these levels do not contribute to the risk of nonhemolytic, immunomodulated transfusion reactions, even in massive transfusions.

Postoperative analgesia by reinjections of local anesthetic through an indwelling retrobulbar catheter.

PURPOSE: To evaluate an indwelling retrobulbar catheter for repeatable postoperative retrobulbar injections of local anesthetics for titratable analgesia after intraocular surgery. METHODS: The prospective study included all 124 patients (124 eyes) who consecutively underwent retinal or cyclocryocoagulation (n = 22), pars plana vitrectomy, or retinal detachment surgery (n = 102), and who were operated on by the same surgeon with local anesthesia within a period of 12 months. Using commercially available retrobulbar needles with a diameter of 0.60 mm or 0.80 mm and a length of 38 mm, 5 ml of mepivacaine 2% with hyaluronidase were injected. Through the same needle, a 28-gauge commercially available flexible catheter was introduced into the retrobulbar space, the needle was withdrawn, and the catheter was fixed in place. When the patients started to feel pain after surgery, 2 ml of mepivacaine 2% or 2 ml of bupivacaine 0.75% were reinjected through the catheter. The catheter was removed 24 to 72 hours after surgery. RESULTS: Because of increasing pain in the postoperative period, 93 patients (93 of 124, or 75%) received a reinjection 4.2+/-2.0 hours after the preoperative injection. Seventy patients received a second reinjection after an additional 2.7+/-1.9 hours, and 42 patients received a third reinjection 3.1+/-2.0 hours later. After each reinjection, the patients became pain free. Removal of the catheter after surgery was unremarkable. CONCLUSIONS: An indwelling retrobulbar catheter for repeatable postoperative injection of short-acting local anesthetics is useful and effective for titratable postoperative analgesia after intraocular surgery, and it allows patients to avoid the side effects of systemic analgesics and sedatives.

[Titration of intraoperative anesthesia and postoperative analgesia]. / Titrierbare intraoperative Anästhesie und postoperative Analgesie.

PURPOSE: To evaluate a temporary retrobulbar catheter for local anesthesia in intraocular surgery and for postoperative analgesia after intraocular surgery. PATIENTS AND METHODS: The study included 40 patients undergoing pars-plana vitrectomy (n = 24) or cyclocryocoagulation (n = 16). After a retrobulbar injection through a 23 G needle, a commercially available 28 G flexible catheter was inserted through the needle. As soon as the patients complained about pain during or up to 24 hours after surgery, local anesthetics were injected through the catheter. RESULTS: Repetitive injections of anesthetics were necessary in 13 patients during pars plana vitrectomy. Starting about 2 hours after surgery, 13 patients after pars-plana vitrectomy and all patients who had undergone cyclocryocoagulation received up to 6 re-injections (every 1.5-5 hours). After all re-injections, the patients became pain-free within two minutes. The catheter was removed after 24 hours. CONCLUSIONS: The results suggest that a temporary insertion of a catheter into the retrobulbar space allows repetitive application of local anesthetics thus leading to a titrable local anesthesia and postoperative analgesia in intraocular surgery.