Biomedical subjects

D I Sessler

Publications and source records attributed to D I Sessler.

At least 19 recordsLinked to original sources

PubMed2007

Autonomic effects of epidural and intravenous fentanyl.

BACKGROUND: We tested the hypothesis that there is greater suppression of autonomic reflexes during general anaesthesia when fentanyl is administered epidurally than when it is given intravenously. METHODS: Ten volunteers were anaesthetized with desflurane. Noxious stimuli of variable intensity were then delivered by tetanic electrical stimuli. Heart rate, arterial pressure, and pupillary dilation in response to these stimuli defined nociception. Seven of these volunteers participated twice using a crossover design: they received i.v. fentanyl on one study day and epidurally on the other. Autonomic responses to alternative tetanic stimuli at L4 and C5 dermatomes were measured every 5 min for 3 h after fentanyl administration. RESULTS: After a brief redistribution period, plasma fentanyl concentrations were virtually identical on both days. After stimulation of the L4 dermatome only, block of pupillary reflex dilation was greater by 47 (22)% after epidural fentanyl compared with i.v. fentanyl. Time to maximal depression of reflex dilation after L4 stimulation was 41 (13) min. Arterial pressure and heart rate decreased after fentanyl by either route but there were no differences observed between L4 and C5 stimulations. CONCLUSION: We conclude that during general anaesthesia, epidural fentanyl enhances antinociception by a spinal mechanism which can be detected by pupillary dilation but not by changes in arterial pressure or heart rate.

Adult↗

PubMed2006

Tissue oxygenation response to mild hypercapnia during cardiopulmonary bypass with constant pump output.

BACKGROUND: Tissue oxygenation is the primary determinant of wound infection risk. Mild hypercapnia markedly improves cutaneous, subcutaneous (s.c.), and muscular tissue oxygenation in volunteers and patients. However, relative contributions of increased cardiac output and peripheral vasodilation to this response remains unknown. We thus tested the hypothesis that increased cardiac output is the dominant mechanism. METHODS: We recruited 10 ASA III patients, aged 40-65 yr, undergoing cardiopulmonary bypass for this crossover trial. After induction of anaesthesia, a Silastic tonometer was inserted s.c. in the upper arm. S.C. tissue oxygen tension was measured with both polarographic electrode and fluorescence-based systems. Oximeter probes were placed bilaterally on the forehead to monitor cerebral oxygenation. After initiation of cardiopulmonary bypass, in random order patients were exposed to two arterial CO(2) partial pressures for 30 min each: 35 (normocapnia) or 50 mm Hg (hypercapnia). Bypass pump flow was kept constant throughout the measurement periods. RESULTS: Hypercapnia during bypass had essentially no effect on Pa(CO(2)) , mean arterial pressure, or tissue temperature. Pa(CO(2)) and pH differed significantly. S.C. tissue oxygenation was virtually identical during the two Pa(CO(2)) periods [139 (50-163) vs 145 (38-158), P=0.335] [median (range)]. In contrast, cerebral oxygen saturation (our positive control measurement) was significantly less during normocapnia [57 (28-67)%] than hypercapnia [64 (37-89)%, P=0.025]. CONCLUSIONS: Mild hypercapnia, which normally markedly increases tissue oxygenation, did not do so during cardiopulmonary bypass with fixed pump output. This suggests that hypercapnia normally increases tissue oxygenation by increasing cardiac output rather than direct dilation of peripheral vessels.

Adult↗

PubMed2006

Patient-controlled epidural analgesia: the role of epidural fentanyl in peripartum urinary retention.

BACKGROUND: Urinary bladder function is impaired during labor and delivery, predisposing to urinary retention. The effect of low-dose epidural opioid on bladder function remains unclear. We tested the hypothesis that adding low-dose fentanyl to epidural ropivacaine for patient-controlled labor analgesia does not promote urinary retention. METHODS: Laboring women who requested patient-controlled epidural analgesia were randomly assigned in a double blind study to 0.2% ropivacaine (R-group, n=100) or 0.2% ropivacaine with fentanyl 2 microg/mL (RF-group, n=98). Urinary bladder distension was assessed clinically every hour. The post-void residual urine volume was measured by ultrasonography. Urine volume exceeding 100 mL was drained by catheterization. Bladder volume of > or =300 mL, as determined by catheterization was considered as evidence of urinary retention. RESULTS: Thirty percent of the patients in each group developed urinary retention during labor. There was no statistically significant difference between the groups. There was an excellent correlation between bladder volume as estimated by ultrasonography and that by catheterization: catheterization volume=0.93 x ultrasound volume + 25; r(2)=0.83. The bias (mean error) was -1+/-99 mL and the precision (average absolute error) between the ultrasound estimate and actual bladder volume determined by catheterization was 58+/-79 mL. CONCLUSION: Addition of fentanyl to patient-controlled epidural analgesia did not increase the risk of urinary retention. Ultrasound measurements were effective and reliable in assessing urinary bladder volumes during labor.

Adult↗

PubMed2005

Magnesium sulphate only slightly reduces the shivering threshold in humans.

BACKGROUND: Hypothermia may be an effective treatment for stroke or acute myocardial infarction; however, it provokes vigorous shivering, which causes potentially dangerous haemodynamic responses and prevents further hypothermia. Magnesium is an attractive anti-shivering agent because it is used for treatment of postoperative shivering and provides protection against ischaemic injury in animal models. We tested the hypothesis that magnesium reduces the threshold (triggering core temperature) and gain of shivering without substantial sedation or muscle weakness. METHODS: We studied nine healthy male volunteers (18-40 yr) on two randomly assigned treatment days: (1) control and (2) magnesium (80 mg kg(-1) followed by infusion at 2 g h(-1)). Lactated Ringer's solution (4 degrees C) was infused via a central venous catheter over a period of approximately 2 h to decrease tympanic membrane temperature by approximately 1.5 degrees C h(-1). A significant and persistent increase in oxygen consumption identified the threshold. The gain of shivering was determined by the slope of oxygen consumption vs core temperature regression. Sedation was evaluated using a verbal rating score (VRS) from 0 to 10 and bispectral index (BIS) of the EEG. Peripheral muscle strength was evaluated using dynamometry and spirometry. Data were analysed using repeated measures anova; P<0.05 was statistically significant. RESULTS: Magnesium reduced the shivering threshold (36.3 [SD 0.4] degrees C vs 36.6 [0.3] degrees C, P = 0.040). It did not affect the gain of shivering (control, 437 [289] ml min(-1) degrees C(-1); magnesium, 573 [370] ml min(-1) degrees C(-1); P=0.344). The magnesium bolus did not produce significant sedation or appreciably reduce muscle strength. CONCLUSIONS: Magnesium significantly reduced the shivering threshold. However, in view of the modest absolute reduction, this finding is considered to be clinically unimportant for induction of therapeutic hypothermia.

Adolescent↗

PubMed2005

Clonidine produces a dose-dependent impairment of baroreflex-mediated thermoregulatory responses to positive end-expiratory pressure in anaesthetized humans.

BACKGROUND: Perioperative hypothermia is common and results from anaesthesia-induced inhibition of thermoregulatory control. Hypothermia is blunted by baroreceptor unloading caused by positive end-expiratory pressure (PEEP), and is mediated by an increase in the vasoconstriction threshold. Premedication with clonidine impairs normal thermoregulatory control. We therefore determined the effect of clonidine on PEEP-induced hypothermia protection. METHODS: Core temperature was evaluated in patients undergoing combined general and epidural anaesthesia for lower abdominal surgery. They were assigned to an end-expiratory pressure of zero (ZEEP) or 10 cm H(2)O PEEP. The PEEP group was divided into three blinded subgroups that received placebo (Cl-0), clonidine 150 microg (Cl-150) and clonidine 300 microg (Cl-300) respectively. Placebo or clonidine was given orally 30 min before surgery. We evaluated core temperature and thermoregulatory vasoconstriction. We also determined plasma epinephrine, norepinephrine, angiotensin II concentrations and plasma renin activity. RESULTS: Core temperature after 180 min of anaesthesia was 35.1 (0.4) degrees C in the ZEEP group. PEEP significantly increased final core temperature to 35.8 (0.5) degrees C (Cl-0 group). Clonidine produced a linear, dose-dependent impairment of PEEP-induced hypothermia protection: final core temperatures were 35.4 (0.3) degrees C in the Cl-150 group and 35.0 (0.6) degrees C in the Cl-300 group. Similarly, clonidine produced a linear and dose-dependent reduction in vasoconstriction threshold: Cl-0, 36.4 (0.3) degrees C; Cl-150, 35.8 (0.3) degrees C; Cl-300, 35.4 (0.6) degrees C. Plasma norepinephrine, angiotensin II concentrations and renin activity were consistent with the thermoregulatory responses. CONCLUSION: Baroreceptor unloading by PEEP normally moderates perioperative hypothermia. However, clonidine premedication produces a linear, dose-dependent reduction in this benefit.

Adrenergic alpha-Agonists↗

PubMed2005

Comparison of the intubating laryngeal mask airway and laryngeal tube placement during manual in-line stabilisation of the neck.

We compared the placement of the laryngeal tube (LT) with the intubating laryngeal mask airway (ILMA) in 51 patients whose necks were stabilised by manual in-line traction. Following induction of anaesthesia and neuromuscular blockade, the LT and ILMA were inserted consecutively in a randomised, crossover design. Using pressure-controlled ventilation (20 cmH(2)O inspiratory pressure), we measured insertion attempts, time to establish positive-pressure ventilation, tidal volume, gastric insufflation, and minimum airway pressure at which gas leaked around the cuff. Data were compared using Wilcoxon signed-rank tests; p < 0.05 was considered significant. Insertion was found to be more difficult with the LT (successful at first attempt in 16 patients) than with the ILMA (successful at first attempt in 42 patients, p < 0.0001). Time required for insertion was longer for the LT (28 [23-35] s, median [interquartile range]) than for the ILMA (20 [15-25] s, p = 0.0009). Tidal volume was less for the LT (440 [290-670] ml) than for the ILMA (630 [440-750] ml, p = 0.013). Minimum airway pressure at which gas leak occurred and incidence of gastric insufflation were similar with two devices. In patients whose necks were stabilised with manual in-line traction, insertion of the ILMA was easier and quicker than insertion of the LT and tidal volume was greater with the ILMA than the LT.

Adult↗

PubMed2004

Intubating laryngeal mask airway allows tracheal intubation when the cervical spine is immobilized by a rigid collar.

BACKGROUND: An intubating laryngeal mask airway (ILMA) facilitates tracheal intubation with the neck in neutral position, which is similar to the neck position maintained by a rigid cervical collar. However, a cervical collar virtually obliterates neck movement, even small movements that normally facilitate airway insertion. We therefore tested the hypothesis that the ILMA will allow tracheal intubation even in patients wearing a rigid cervical collar. METHODS: We performed blind tracheal intubation via an ILMA under general anaesthesia in 50 patients with a rigid Philadelphia collar in place undergoing cervical spine surgery and 50 general surgical patients. Time required for intubation, intubation success rate, and numbers and type of adjusting manoeuvres used were recorded. RESULTS: Inter-incisor distance was significantly smaller (4.1 (0.8) vs 4.6 (0.7) cm, mean (sd), P<0.01) and Mallampati scores were significantly greater (P<0.001) in the patients with collars. ILMA insertion took longer (30 (25) vs 22 (6) s), more patients required two insertion attempts (15 vs 3; P<0.005), and ventilation adequacy with ILMA was worse (P<0.05) in collared patients. However, there were no significant differences between the collars and control patients in terms of total time required for intubation (60 (41) vs 50 (30) s), number of intubation attempts, overall intubation success rate (96 vs 98%), or the incidence of intubation complications. CONCLUSIONS: Blind intubation through an ILMA is thus a reasonable strategy for controlling the airway in patients who are immobilized with a rigid cervical collar.

Adolescent↗

PubMed2004

Block-dependent sedation during epidural anaesthesia is associated with delayed brainstem conduction.

BACKGROUND: Neuraxial anaesthesia produces a sedative and anaesthetic-sparing effect. Recent evidence suggests that spinal cord anaesthesia modifies reticulo-thalamo-cortical arousal by decreasing afferent sensory transmission. We hypothesized that epidural anaesthesia produces sensory deafferentation-dependent sedation that is associated with impairment of brainstem transmission. We used brainstem auditory evoked potentials (BAEP) to evaluate reticular function in 11 volunteers. METHODS: Epidural anaesthesia was induced with 2-chloroprocaine 2%. Haemodynamic and respiratory responses, sensory block level, sedation depth and BAEP were assessed throughout induction and resolution of epidural anaesthesia. Sedation was evaluated using verbal rating score (VRS), observer's assessment alertness/sedation (OAA/S) score, and bispectral index score (BIS). Prediction probability (PK) was used to associate sensory block with sedation, as well as BIS with other sedation measures. Spearman's rank order correlation was used to associate block level and sedation with the absolute and interpeak BAEP latencies. RESULTS: Sensory block level significantly predicted VRS (PK=0.747), OAA/S score (PK=0.748) and BIS. BIS predicted VRS and OAA/S score (PK=0.728). The latency of wave III of BAEP significantly correlated with sedation level (rho=0.335, P<0.01) and sensory block (rho=0.394, P<0.01). The other BAEP parameters did not change during epidural anaesthesia. Haemodynamic and respiratory responses remained stable throughout the study. CONCLUSIONS: Sedation during epidural anaesthesia depends on sensory block level and is associated with detectable block-dependent alterations in the brainstem auditory evoked responses. Sensory deafferentation may reduce CNS alertness through mechanisms related to brainstem neural activity.

Adult↗

PubMed2004

Nitrous oxide increases the incidence of bowel distension in patients undergoing elective colon resection.

BACKGROUND: Nitrous oxide rapidly inflates gas-filled spaces such as the intestines; but whether the resulting bowel distension is clinically important remains unclear. We therefore tested the hypothesis that nitrous oxide produces clinically important bowel distension. METHODS: Patients scheduled for colon resection were anesthetized with isoflurane and 35% oxygen and randomly assigned to 65% nitrous oxide (n = 175) or 65% nitrogen in air (n = 169). At the end of surgery, blinded surgeons rated the degree of bowel distension as none, mild, moderate, or severe. Patients reported pain, and nausea and vomiting (PONV) 2 h after surgery. Data are reported as means (SD). P < 0.05 was statistically significant. RESULTS: Morphometric and demographic data were similar in the groups. The duration of surgery was 3.0 (1.2) h in the nitrous oxide group and 3.4 (1.5) h in the air group (P = 0.017). Postoperative self-reported pain scores (visual analog scale, 0-100 mm) were greater in the nitrous oxide group (43 [30] mm) than in the air group (35 [31] mm, P = 0.018). Although the incidence of PONV was similar in the groups, VAS scores for nausea were significantly greater in the nitrous oxide group (P = 0.040). Moderate-to-severe bowel distension was observed in 23% of nitrous oxide patients, but in only 9% of patients in the air group (P < 0.001). The number-needed-to-harm for moderate or severe bowel distension from nitrous oxide was thus seven. CONCLUSIONS: Our results suggest that avoiding nitrous oxide administration during prolonged bowel operations will minimize bowel distension and possibly reduce postoperative pain related to it.

Adolescent↗

PubMed2004

Pethidine and skin warming to prevent shivering during endovascular cooling.

We tested the efficacy of pethidine and cutaneous warming to prevent shivering during percutaneous cooling in unanaesthetized patients. Ten patients scheduled for cranial neurosurgery received pethidine infusion and skin warming. The Setpoint internal heat-exchanging catheter was inserted and cooling to 33.5 degrees C was started. Clonidine and chlorpromazine were given as "rescue medication" to treat shivering. General anaesthesia was planned to be induced after cooling was complete. Rewarming was initiated at dural closure. Three patients successfully completed the protocol, cooling to 33.8 degrees C at a median rate of 3.6 (range: 3.4-3.8) degrees C/h. Two patients cooled to 33.8 degrees C but required treatment for shivering (cooling rate: 2.9 [2.8-3.1] degrees C/h). Four patients failed to cool adequately because of refractory shivering (cooling rate: 20 [1.5-2.9] degrees C/h). One patient did not shiver and yet failed to cool adequately (cooling rate: 0.76 degrees C/h). Rewarming was at a rate of 26 (1.2-4.3) degrees C/h. There were no significant complications arising from catheter placement. The combination of skin warming and pethidine was not reliable enough to be recommended for use during endovascular cooling in unanaesthetized patients.

Adult↗

PubMed2003

Blood pressure response to thermoregulatory vasoconstriction during isoflurane and desflurane anesthesia.

BACKGROUND: Mild perioperative hypothermia produces morbid cardiac outcomes that may result from sympathetically induced hypertension. However, volatile anesthetics produce vasodilatation that may reduce the hemodynamic response to hypothermia. We tested the hypothesis that the volatile anesthetics isoflurane and desflurane blunt the normal cold-induced hypertensive response. METHODS: We analyzed prospective data from three analogous studies: 1) 10 volunteers given desflurane (2.6 volume percentage) maintained in left-lateral position; 2) nine volunteers without anesthesia or anesthetized with various doses of desflurane; and 3) eight volunteers given various concentrations of isoflurane. Mean skin temperature was reduced to 31 C, which decreased core body temperature and triggered thermoregulatory vasoconstriction. Mean arterial pressures were determined before and after hypothermia provoked intense thermoregulatory vasoconstriction. RESULTS: The hemodynamic responses to thermoregulatory vasoconstriction were similar without anesthesia and at all concentrations of desflurane and isoflurane. On average, mean arterial pressure increased 14 (SD = 5) mmHg with and without anesthesia. CONCLUSION: We conclude that thermoregulatory vasoconstriction significantly increases arterial pressure with or without isoflurane or desflurane anesthesia.

Anesthesia, General↗

PubMed2003

A new system to target the effect-site during propofol sedation.

BACKGROUND: We evaluated a new, integrated, covariate-adjusted, target-controlled infusion system during sedation with propofol combined with 50% nitrous oxide (N2O) and with propofol only (Air). METHODS: The protocol consisted of sequential 15-minute cycles in 20 volunteers. After a 15-minute control period, propofol was infused to an initial target effect-site concentration of 0.25 microg x ml-1 (N2O) or 1.5 microg x ml-1 (Air). Subsequently, the target effect-site concentration was increased by 0.25 (N2O) or 0.5 microg x ml-1 (Air) for 15 min This sequence was continued until the volunteers lost consciousness as defined by an Observer's Assessment Alertness/Sedation (OAA/S) score = 2. RESULTS: Venous plasma propofol concentrations at the beginning(9 elapsed minutes) and end(15 elapsed minutes) of the pseudo-steady state period differed by only 0.00 +/- 0.16 microg x ml-1 (P = 0.78) during the N2O and 0.00 +/- 0.25 microg x ml-1 (P = 0.91) during the Air trial. OAA/S scores and bispectral index values, as surrogate measures of pharmacodynamic effect, were not different during this time in either trial. The median(25th, 75th percentiles) of the median performance error (%) was -13 (-24, -1) during the N2O and -18 (-26, -9) during the Air trial. The median absolute performance error (%) was 17 (10, 24) in the N2O and 22 (12, 28) in Air trial. The divergence (%/h) was -10 (-26, 4) in the N2O and 14 (-21, 26) in Air trial. The wobble was 7 (5, 10) in the N2O and 6 (4, 8) in the Air trial. CONCLUSIONS: When tested with venous blood samples, our TCI system for propofol, using a covariate-adjusted, integrated pharmacokinetic model to target effect-site concentrations, demonstrated a clinically acceptable accuracy and stability during mild to moderate sedation.

Adult↗

PubMed2003

Automated responsiveness test and bispectral index monitoring during propofol and propofol/N2O sedation.

BACKGROUND: Sedation practice, especially when non-anaesthesia personnel are involved, requires efficient anaesthetic depth monitoring. Therefore, we used prediction probability (PK) to evaluate the performance of the bispectral index (BIS) of the EEG and automated responsiveness test (ART) to predict sedation depth and loss of subject's responsiveness during propofol sedation, with and without N2O. METHODS: Twenty volunteers were studied during propofol administration with (N2O) and without (Air) N2O. The protocol consisted of sequential 15-min cycles. After a control period, propofol was infused to a target effect-site concentration of 0.25 microg/ml (N2O) or 1.5 microg/ml (Air), which was subsequently increased by 0.25 or 0.5 microg/ml, respectively, until loss of responsiveness was detected by loss of response to command [observer's assessment of alertness/sedation (OAA/S) score <or= 2]. RESULTS: Deeply sedated patients did not respond to ART indicating that the sensitivity was 1.0 with or without N2O. The specificity of ART was 0.24 with Air and 0.98 with N2O. The BIS was better than ART in predicting OAA/S score (PK = 0.84 vs. 0.77) and loss of responsiveness (PK = 0.87 vs. 0.69) during the Air trial. Nitrous oxide decreased the performance of BIS in predicting OAA/S score (PK = 0.76), but increased the performance of ART to predict loss of responsiveness (PK = 0.85). CONCLUSION: BIS and ART comparably predict sedation and loss of responsiveness. However, ART, because of its resistance to false-normal responses, might prove to be more useful on an individual patient basis - especially in the presence of agents that impair BIS sensitivity.

Adult↗

PubMed2003

Effect of intra-operative end-tidal carbon dioxide partial pressure on tissue oxygenation.

Postsurgical infection risk is correlated with subcutaneous tissue oxygenation. Mild hypercapnia augments cutaneous perfusion. We tested the hypothesis that peripheral tissue oxygenation increases as a function of arterial PCO2 in surgical patients. Twenty patients were randomly assigned to intra-operative end tidal PCO2 of 3.99 (control) or 5.99 kPa (hypercapnia). All other anaesthetic management was per protocol. Tissue oxygen partial pressure, transcutaneous oxygen tension, cerebral oxygen saturation, and cardiac output were measured. Mean (SD) subcutaneous tissue oxygen tension was 8.39 (1.86) kPa in control and 11.84 (2.53) kPa hypercapnia patients (p = 0.014). Cerebral oxygen saturation was 55 (4)% for control vs. 68 (9)% for hypercapnia (p = 0.004). Neither cardiac index nor transcutaneous tissue oxygen tension differed significantly between the groups. Mild intra-operative hypercapnia increased subcutaneous and cerebral oxygenation. Increases in subcutaneous tissue oxygen partial pressure similar to those observed in patients assigned to hypercapnia are associated with substantial reductions in wound infection risk.

Adult↗

PubMed2003

Prediction of difficult laryngoscopy in obese patients by ultrasound quantification of anterior neck soft tissue.

In 50 morbidly obese patients, we quantified the soft tissue of the neck from the skin to the anterior aspect of the trachea at the vocal cords using ultrasound. Thyromental distance, mouth opening, limited neck mobility, modified Mallampati score, abnormal upper teeth, neck circumference and sleep apnoea were assessed as predictors of difficult laryngoscopy. Of the nine (18%) cases of difficult laryngoscopy, seven (78%) had a history of obstructive sleep apnoea, compared with two of the 41 patients (5%) in whom laryngoscopy was easy (p < 0.001). Patients in whom laryngoscopy was difficult had more pretracheal soft tissue (mean (SD) 28 (2.7) mm vs. 17.5 (1.8) mm; p < 0.001) and a greater neck circumference (50 (3.8) vs. 43.5 (2.2) cm; p < 0.001). None of the other predictors correlated with difficult laryngoscopy. We conclude that an abundance of pretracheal soft tissue at the level of the vocal cords is a good predictor of difficult laryngoscopy in obese patients.

Adult↗

PubMed2003

Effect of postoperative skin-surface warming on oxygen consumption and the shivering threshold.

Cutaneous warming is reportedly an effective treatment for shivering during epidural and after general anaesthesia. We quantified the efficacy of cutaneous warming as a treatment for shivering. Unwarmed surgical patients (final intra-operative core temperatures approximately 35 degrees C) were randomly assigned to be covered with a blanket (n = 9) or full-body forced-air cover (n = 9). Shivering was evaluated clinically and by oxygen consumption. Forced-air heating increased mean-skin temperature (mean (SD) 35.7 degrees C (0.4) vs. 33.2 degrees C (0.8); p < 0.0001) and lowered core temperature at the shivering threshold (35.7 degrees C (0.2) vs. 36.4 degrees C(0.2); p < 0.0001). Active warming improved thermal comfort and significantly reduced oxygen consumption from 9.7 (4.4) ml x min(-1) x kg(-1) to 5.6 (1.9) ml x min(-1) x kg(-1) (p = 0.038). However, the duration of shivering was similar in the unwarmed (37 min (11)) and active warming (36 min (10)) groups. Core temperature contributed about four times as much as skin temperature to control of shivering. Cutaneous warming improved thermal comfort and reduced metabolic stress in postoperative patients, but did not quickly obliterate shivering.

Adolescent↗

PubMed2003

Supplemental oxygen does not reduce postoperative nausea and vomiting after thyroidectomy.

BACKGROUND: Supplemental intra-operative oxygen 80% halves the incidence of nausea and vomiting after open and laparoscopic abdominal surgery, perhaps by ameliorating intestinal ischaemia associated with abdominal surgery. It is unlikely that thyroid surgery compromises intestinal perfusion. We therefore tested the hypothesis that supplemental perioperative oxygen does not reduce the risk of postoperative nausea and vomiting (PONV) after thyroidectomy. METHODS: One hundred and fifty patients undergoing thyroidectomy were given sevoflurane anaesthesia. After induction, patients were randomly assigned to the following treatments: (i). 30% oxygen, (ii). 80% oxygen, or (iii). 30% oxygen with droperidol 0.625 mg. RESULTS: The overall incidence of nausea during the first 24 h after surgery was 48% in the patients given oxygen 30%, 46% in those given oxygen 80%, and 22% in those given droperidol (P=0.004). There were no significant differences between the oxygen 30% and 80% groups in incidence or severity of PONV, the need for rescue antiemetics, or patient satisfaction. Droperidol significantly shortened the time to first meal. CONCLUSIONS: Supplemental oxygen was ineffective in preventing nausea and vomiting after thyroidectomy, but droperidol reduced the incidence.

Adult↗

PubMed2003

Nitrous oxide decreases shivering threshold in rabbits less than isoflurane.

BACKGROUND: Comparable minimum alveolar concentration (MAC) fractions of volatile anaesthetics produce similar thermoregulatory impairment. Nitrous oxide, however, decreases the vasoconstriction threshold less than sevoflurane or isoflurane. We tested the hypothesis that nitrous oxide also decreases shivering threshold less than isoflurane alone or in combination. METHODS: Twenty-four rabbits were assigned randomly to one of three 0.3 MAC anaesthetic regimens: (i) nitrous oxide 69%; (ii) nitrous oxide 35% and isoflurane 0.3%; or (iii) isoflurane 0.6%. Body temperature was lowered by perfusing 10 degrees C water through a U-shaped thermode positioned in the colon. Shivering was evaluated by inspection. RESULTS: The rabbits anaesthetized with nitrous oxide alone shivered at 37.0 (0.5) degrees C (P<0.01 vs other groups). In those given the nitrous oxide and isoflurane combination, the shivering threshold was 36.4 (0.5) degrees C and that in the isoflurane group was 35.9 (0.4) degrees C. CONCLUSION: This study indicates that nitrous oxide reduces the shivering threshold less than isoflurane.

Anesthetics, Inhalation↗