小腿穿支血管筋膜蒂皮瓣修复下肢软组织缺损

目的:探讨小腿穿支血管筋膜蒂皮瓣转移的手术方法和临床效果.方法:1998年5月至2009年1月临床应用带小腿内、后、前外、后外侧穿支血管的筋膜蒂皮瓣邻近转位,对下肢皮肤软组织缺损创面进行修复共62例,男50例,女12例;年龄7～78岁.其中应用带胫后动脉穿支的小腿内侧筋膜蒂皮瓣23例,带腓动脉终末穿支小腿前外侧筋膜蒂皮辩9例,带腓动脉穿支腓肠神经营养血管筋膜蒂皮瓣22例,带腘外侧动脉小腿后外侧筋膜蒂皮瓣8例.结果:除2例术后皮辩远端表皮坏死结痂,1例皮瓣远端部分皮肤坏死行Ⅱ期植皮,其余皮瓣均完全成活.随访1个月～3年,皮瓣外观满意,功能良好.结论:小腿部单个穿支血管供血面积有限,应用带穿支血管营养血管链的筋膜蒂度瓣可扩大小腿皮瓣的裁取面积,保证皮瓣的血供及回流.     

小腿内侧逆行筋膜蒂皮瓣修复胫前踝足跟部软组织缺损

目的 探讨采用小腿内侧逆行筋膜蒂皮瓣修复胫前踝足跟部软组织缺损的临床疗效.方法 小腿中下段及踝足跟部软组织缺损的23例患者,其中小腿下段胫前8例,足跟部11例,足背部4例,软组织缺损面积为7 cm×5 cm～18 cm×10 cm,均采用小腿内侧筋膜蒂皮瓣逆行修复,皮瓣切取面积为12 cm×6 cm～23 cm×12 cm,逆行蒂宽4 cm以上.结果 随访4～17个月,皮瓣均成活,5例皮瓣远端部分坏死,所有皮瓣质地优良,外形恢复满意,患肢功能恢复满意.结论 小腿内侧逆行筋膜蒂皮瓣切取面积大,血供可靠,操作简单,不损伤主干血管,适合修复小腿中、下段及足踝部的皮肤软组织缺损创面,是临床治疗下肢较大面积软组织缺损安全有效的方法之一.     

以远端穿支血管为蒂的皮神经营养血管逆行皮瓣修复小腿和足踝部软组织缺损

目的 探讨以远端穿支血管为蒂的皮神经营养血管逆行皮瓣修复小腿和足踝部软组织缺损的皮瓣选择,技术要点和临床疗效.方法 采用以腓动脉穿支为远端蒂的腓肠神经营养血管逆行皮瓣修复小腿下端、足跟负重部与足踝前侧或外侧创面16例,以胫后动脉穿支为远端蒂的隐神经营养血管逆行皮瓣修复足跟内侧创面6例,以胫前动脉穿支为远端蒂的腓浅神经营养血管逆行皮瓣修复足踝前侧或内侧创面3例.创面面积3.0 cm×3.5 cm～8.5cm×9.0cm.结果 所有皮瓣均存活,2例远端静脉回流障碍,经换药后痊愈.1例皮瓣远端伤口裂开,重新缝合后痊愈.25例获随访8个月至5年,发现皮瓣外形满意,具有保护性感觉,无磨损破溃,患者穿鞋行走正常.结论 以腓动脉、胫前动脉或胫后动脉穿支为远端蒂的神经营养血管皮瓣血供可靠,方法简单,不牺牲主干血管,是修复小腿和足踝部软组织缺损的良好方法.避免皮瓣张力是保证皮瓣成活的关键.     

小腿穿支血管筋膜蒂皮瓣修复小儿足踝部软组织缺损

目的探讨小腿穿支血管筋膜蒂皮瓣修复小儿足踝部软组织缺损的临床疗效。方法 2012年5月-2015年1月,采用小腿穿支血管筋膜蒂皮瓣修复小儿足踝部软组织缺损12例。足踝部软组织缺损面积3.5 cm×5.0 cm～7.0 cm×15.0 cm,均伴有不同程度的肌腱或骨骼外露。带胫后动脉穿支的小腿内侧筋膜蒂皮瓣7例,带腓动脉外踝后上穿支的筋膜蒂皮瓣4例,带胫后动脉穿支的小腿内侧筋膜蒂皮瓣及带腓动脉外踝后上穿支的筋膜蒂皮瓣1例。结果术后12例皮瓣均成活,其中2例皮瓣皮缘远端少许坏死,经换药后愈合;12例获随访,随访时间3～18个月,平均8.9个月;皮瓣血运良好,无臃肿,外形满意,供区愈合良好;患肢功能良好。结论小腿穿支血管筋膜蒂皮瓣修复小儿足踝部软组织缺损操作简单,疗效可靠,是修复小儿足踝部软组织缺损理想的治疗方法之一。     

儿童胫后动脉穿支蒂隐神经营养皮瓣的临床应用

目的探讨儿童胫后动脉穿支蒂隐神经营养血管蒂岛状皮瓣修复足及小腿皮肤软组织缺损的临床应用及疗效。方法在小腿内侧以胫后动脉内踝上穿支蒂隐神经营养筋膜蒂设计岛状皮瓣修复足及小腿皮肤软组织缺损11例。皮瓣面积4.5cm×5.0cm～14.0cm×5.0cm,在小腿内侧设计。结果 9例皮瓣全部成活,2例皮瓣远端部分坏死。术后皮瓣质地好,外形美观,疗效满意。结论该皮瓣设计灵活,血运可靠,切取方便,不损伤胫后动脉,是修复足及小腿皮肤软组织缺损的理想皮瓣。     

带蒂皮瓣治疗小腿和足踝部皮肤软组织缺损

目的探讨小腿和足踝部皮肤软组织缺损的手术方法及其疗效评价。方法1997年6月至2005年12月,43例小腿及足踝部皮肤软组织缺损的患者,男38例,女5例;年龄7～63岁,平均35岁;皮瓣面积4cm×3cm～25cm×15cm。采用9种带蒂的肌皮瓣和筋膜皮瓣进行治疗:(1)腓肠肌内、外侧头肌皮瓣带蒂转移修复小腿中上1/3合并膝关节前及内侧皮肤软组织缺损2例;(2)小腿前内侧交腿皮瓣修复小腿中段胫前皮肤软组织缺损2例;(3)带隐神经小腿内侧交腿皮瓣修复前足足底缺损1例;(4)带胫后动脉小腿内侧逆行岛状皮瓣修复足背部皮肤软组织缺损1例;(5)小腿内侧远端蒂筋膜皮瓣修复小腿中下1/3胫前皮肤软组织缺损2例;(6)腓肠神经营养血管蒂逆行岛状皮瓣修复小腿中下1/3、踝部及足跟皮肤软组织缺损17例;(7)隐神经营养血管蒂逆行岛状皮瓣修复小腿中下1/3、踝部及足背皮肤软组织缺损14例;(8)外踝上动脉逆行岛状皮瓣修复足背皮肤软组织缺损2例。(9)足内侧远端带蒂岛状筋膜皮瓣修复第一跖骨头处皮肤软组织缺损2例。结果43例皮瓣中有37例术后全部成活,创面一期愈合,1例皮瓣浅层坏死,5例皮瓣远端边缘少许坏死,经短期换药后愈合。所有病例均得到随访,皮瓣全部良好。结论治疗小腿和足踝部皮肤软组织缺损应严格掌握手术适应证,合理选择皮瓣种类。腓肠神经和隐神经营养血管蒂岛状皮瓣是较理想的修复小腿及足踝部软组织缺损的材料。     

小腿筋膜皮瓣及小腿内侧逆行轴形皮瓣在下肢创伤修复时的选择及评估

目的:探讨两种小腿皮瓣(小腿筋膜皮瓣及小腿内侧逆行轴形皮瓣)在下肢创伤后皮肤软组织缺损修复时的选择及评估。方法:①在小腿设计局部随意筋膜皮瓣,皮瓣大小范围4cm×6cm～7cm×15cm,转移修复同侧或对侧小腿皮肤软组织缺损并骨外露;②以胫后动脉内踝上发出的皮动脉穿支为轴,在小腿内侧设计逆行轴形皮瓣,皮瓣大小范围4cm×12cm～6cm×15cm,转移修复同侧或对侧足底、踝部、小腿皮肤软组织缺损并肌腱或骨外露。结果:临床共选用11个皮瓣,其中6例为筋膜皮瓣,5例为小腿内侧逆行轴形皮瓣,修复同侧或对侧下肢皮肤软组织缺损并肌腱或骨外露。11例皮瓣术后均成活良好,创面修复效果良好,随访6～12个月,伤肢外形及功能恢复满意。结论:小腿筋膜皮瓣,设计灵活,切取便利,不损伤主要血管,血供丰富,尤其在局部主要血管受损时是修复下肢严重创伤的有效方法之一。小腿内侧逆行轴形皮瓣可切取皮瓣距离长,面积大,血供恒定可靠,成活率高,是修复足底、踝部、小腿严重创伤的最佳选择。此两种皮瓣的应用应针对小腿创面的部位、面积及其创伤特点进行合适的选择,可达到满意的修复效果。     

腓肠内侧动脉穿支皮瓣修复小腿中上段软组织缺损

目的 探讨应用腓肠内侧动脉穿支血管皮瓣带蒂转移修复小腿中上段皮肤软组织缺损的临床效果. 方法 2006年5月至2012年8月,对小腿中上段皮肤软组织缺损患者26例,创面面积为5 cm×3 cm～12cm×8cm.均应用同侧腓肠内侧动脉穿支血管皮瓣带蒂转移修复.皮瓣前内界为胫骨的内后缘,后外侧界为小腿后正中纵轴线,以腘皱褶中点至内踝中点连线为轴设计皮瓣,皮瓣面积为6 cm×4 cm～13 cm×9 cm. 结果 术后26例皮瓣全部成活.术后随访6～18个月,皮瓣质地柔软,富有弹性,不臃肿,供区无明显功能障碍,行走时步态基本正常. 结论 应用腓肠内侧动脉穿支皮瓣带蒂转移修复小腿中上段皮肤软组织缺损临床效果佳,该皮瓣血供丰富,血管解剖恒定,皮瓣质地良好,供区无明显功能障碍,故不失为修复小腿中上段皮肤软组织缺损的一种较好的选择.     

改良小腿内侧筋膜蒂皮瓣的临床应用和筋膜蒂位置分区的研究

目的 讨论在小腿不同分区内改良小腿内侧筋膜蒂皮瓣的设计及临床效果. 方法 自2005年1月至2008年2月,将小腿均分为三个区,按皮瓣筋膜蒂位置的分区不同分别采用逆行或顺行的改良小腿内侧筋膜蒂皮瓣修复膝前、小腿及足踝部软组织缺损45例.皮瓣面积最大25.0 cm×10.0cm,最小5.0 cm×3.0 cm. 结果 43例皮瓣完全成活,创面一期愈合;小腿上1/3内有2例皮瓣远端部分坏死,经换药后愈合.术后随访4～20个月,皮瓣颜色及质地好,外形及功能恢复满意. 结论 改良小腿内侧筋膜蒂皮瓣设计灵活、切取简单,不牺牲主干血管,血供可靠,可根据皮瓣筋膜蒂位置的不同选择合适皮瓣,是一种修复下肢软组织缺损的理想皮瓣.     

穿支皮瓣移植在手指创面修复中的应用

目的 探讨穿支皮瓣游离移植修复手指皮肤软组织缺损的设计和手术技巧.方法 切取小腿前外侧、小腿内侧下部、小腿外侧血管穿支皮瓣以及远段骨间背血管蒂穿支皮瓣,移植修复手指小创面13例.结果 13例皮瓣全部存活,受区与供区的功能、外观均良好.结论 在肢体部位以皮穿支或轴型血管为蒂设计穿支皮瓣,游离移植修复手指创面,患者痛苦小、损伤小,创面能获得满意覆盖.这为手外伤修复提供了一种新的选择,对术者也提出了更高的要求.     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Is the recovery profile of mivacurium independent of the rate of decay of its plasma concentration in patients with normal plasma cholinesterase activity?

Background: The duration of action of muscle relaxants is poorly correlated to the rate of decay of their plasma concentration. The plasma concentration of mivacurium may rapidly decrease below its active concentration because of the extensive hydrolysis of mivacurium. By inflating a tourniquet on one upper limb for 3 min after the administration of atracurium, mivacurium or vecuronium, we studied the influence of the initial decline of their plasma concentration on their effect. Methods: In 50 patients anaesthetised with thiopental, isoflurane and fentanyl, the effect of bolus doses of 0.15 or 0.25 mg . kg^?1 mivacurium (MIV 15, MIV 25), 0.3 or 0.5 mg . kg^?1 atracurium (ATR 30, ATR 50) and 0.06 or 0.1 mg . kg^?1 vecuronium (VEC 06, VEC 10) were measured on both arms (evoked response of the adductor pollicis to train-of-four stimulation every 12 s), a tourniquet being applied on one arm just before and during 3 min after the muscle relaxant bolus. Results: Tourniquet inflation of 3 min almost abolished the neuromuscular effect of mivacurium. In the vecuronium groups and in the ATR 50 group, tourniquet inflation did not modify the maximum degree of depression of the twitch response. Also, the duration of action of vecuronium was unaffected by the tourniquet. In the ATR 30 group, times to return of the twitch response to 25% (duration 25%) and 75% (duration 75%) of control response were significantly shorter in the cuffed arm, 23 min vs 27 min, and 41 min vs 45 min, respectively. In the ATR 50 group, only duration 25% was significantly shorter in the cuffed arm (41 min vs 45 min). Conclusion: The results suggest that the rate of decline of the plasma concentration of mivacurium is so rapid, that a very low and almost clinically ineffective concentration is present as soon as 3 min after its administration. The results also indicate that the recovery from a mivacurium-induced neuromuscular blockade is not influenced by the rate of decay of its plasma concentration in patients with genotypically normal plasma cholinesterase.     

Membranes in Artificial Organs

Abstract: Membrane processes play a pivotal and enabling role in modern replacement therapy for acute and chronic organ failure and in the management of immunologic diseases. In fact, virtually all contemporary extracorporeal blood purification methods employ membrane devices, and the next generation of artificial organs and tissue engineering therapies are almost certain to be similarly grounded in membrane technology. In this short essay, we comment on the similarities and differences among synthetic membranes and their natural counterparts and also provide a critical overview of the demographics and technology of hemodialysis, hemofiltration, apheresis, oxygenation, and emerging membrane technologies and applications.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.