Samar K. Taha

Preoxygenation: Comparison of Maximal Breathing and Tidal Volume Breathing Techniques

BACKGROUND Preoxygenation with tidal volume breathing for 3-5 min is recommended by Hamilton and Eastwood. This report compares tidal volume preoxygenation technique with deep breathing techniques for 30-60 s. METHODS The study was conducted in two parts on patients undergoing elective coronary bypass grafting. In the first group (n = 32), each patient underwent all of the following preoxygenation techniques: the traditional technique consisting of 3 min of tidal volume breathing at an oxygen flow of 5 l/min; four deep breaths within 30 s at oxygen flows of 5 l/min, 10 l/min, and 20 l/min; and eight deep breaths within 60 s at an oxygen flow of 10 l/min. The mean arterial oxygen tensions after each technique were measured and compared. In the second group (n = 24), patients underwent one of the following techniques of preoxygenation: the traditional technique (n = 8), four deep breaths (n = 8), and eight deep breaths (n = 8). Apnea was then induced, and the mean times of hemoglobin desaturation from 100 to 99, 98, 97, 96, and 95% were determined. RESULTS In the first group of patients, the mean arterial oxygen tension following the tidal breathing technique was 392+/-72 mm Hg. This was significantly higher (P<0.05) than the values obtained following the four deep breath technique at oxygen flows of 5 l/min (256+/-73 mm Hg), 10 l/min (286+/-69 mm Hg), and 20 l/min (316+/-67 mm Hg). In contrast, the technique of eight deep breaths resulted in a mean arterial oxygen tension of 369+/-69 mm Hg, which was not significantly different from the value achieved by the traditional technique. In the second group of patients, apnea following different techniques of preoxygenation was associated with a slower hemoglobin desaturation in the eight-deep-breaths technique as compared with both the traditional and the four-deep-breaths techniques. CONCLUSION Rapid preoxygenation with the eight deep breaths within 60 s can be used as an alternative to the traditional 3-min technique.

Nasopharyngeal oxygen insufflation following pre-oxygenation using the four deep breath technique

This paper evaluates the effectiveness of nasopharyngeal oxygen insufflation following preoxygenation using the four deep breath technique within 30 s, on the onset of haemoglobin desaturation during the subsequent apnoea. Thirty ASA I or II patients were randomly allocated to one of two groups. In the study group (n = 15), pre‐oxygenation was followed by insufflation of oxygen at a flow of 5 l.min−1 via a nasopharyngeal catheter commenced at the onset of apnoea. In the control group, pre‐oxygenation was not followed by nasopharyngeal oxygen insufflation (n = 15). In the control group, Spo2 fell to 95% within a mean (SD) apnoea time of 3.65 (1.15) min, whereas in the study group, Spo2 was maintained in all patients at 100% throughout the 6 min of apnoea, at which point apnoea was terminated and positive pressure ventilation commenced. We conclude that nasopharyngeal oxygen insufflation following pre‐oxygenation using the four deep breath technique can delay the onset of haemoglobin desaturation for a significant period of time during the subsequent apnoea.

Supplementation of pre-oxygenation in morbidly obese patients using nasopharyngeal oxygen insufflation

During apnoea following induction of anaesthesia, morbidly obese patients may suffer a rapid decrease in oxygen saturation. This study compares pre‐oxygenation alone with pre‐oxygenation followed by nasopharyngeal oxygen insufflation on the onset of desaturation occurring during the subsequent apnoea. A randomised controlled trial was performed in 34 morbidly obese patients undergoing gastric bypass or gastric band surgery. Seventeen patients received nasopharyngeal oxygen supplementation following pre‐oxygenation (Study group, body mass index = 41.8 (6.9) kg.m−2), and the other 17 patients received pre‐oxygenation alone (Control group, body mass index = 42.7 (5.4) kg.m−2). Time from the onset of apnoea until Spo2 fell to 95% was compared between the two groups with a cut‐off of 4 min. In the control group, the Spo2 fell from 100% to 95% during the subsequent apnoea in 145 (27) s, with a significantly negative correlation (r2 = 0.66, p < 0.05) between the time to desaturation to 95% and the body mass index. In the study group, the Spo2 was maintained in 16 of 17 patients at 100% for 4 min when apnoea was terminated. In conclusion, nasopharyngeal oxygen insufflation following pre‐oxygenation in morbidly obese patients delays the onset of oxyhaemoglobin desaturation during the subsequent apnoea.

Propofol is superior to thiopental for intubation without muscle relaxants

PurposeTo compare intubating conditions and cardiovascular changes following induction of anesthesia and tracheal intubation in patients receiving either lidocaine-remifentanil-propofol or lidocaine-remifentanil-thiopental prior to induction.MethodsIn a randomized, double-blind study 76 healthy adult patients were assigned to one of two groups: lidocaine 1.5 mg kg-1, remifentanil 2μg kg-1 and propofol 2 mg kg-1 (Group P) or lidocaine 1.5 mg kg-1, remifentanil 2μg kg-1 and thiopental 5 mg kg-1 (Group T). Ninety seconds after the administration of the hypnotic agent, laryngoscopy and tracheal intubation were attempted. Intubating conditions were assessed as excellent, good or poor on the basis of ease of ventilation, jaw relaxation, position of the vocal cords, and patient’s response to intubation and slow inflation of the tracheal cuff. The mean arterial pressure (MAP) and heart rate (HR) were measured 45 sec after hypnotic agent administration, immediately after tracheal intubation, two and five minutes after intubation.ResultsExcellent intubating conditions were obtained in 84% of Group P patients and 50% of Group T patients (P < 0.05). The percentage decrease from baseline MAP was significantly higher in Group P than in Group T postinduction (27.4% ± 1 1.6 vs 21.8% ± 10.0) and immediately postintubation (19.0% ± 16.7 vs 11.2% ± 14.9). The percentage change from baseline HR was significantly higher in Group Pthan in Group T postinduction (13.8% ± 9.7 vs 0.5% ± 12.4), immediately postintubation (8.7% ± 13.7 vs 2.1% ± 13.1), and two minutes postintubation (7.04% ± 14.3 vs 3.5% ± 14.3).ConclusionLidocaine-remifentanil-propofol is superior to lidocaine-remifentanil-thiopental for tracheal intubation without muscle relaxants. However, it induces more hypotension and bradycardia.RésuméObjectifComparer les conditions d’intubation et les changements cardiovasculaires suivant l’induction de l’anesthésie et l’intubation endotrachéale chez les patients qui reçoivent un mélange de lidocaïne-rémifentanil-propofol ou de lidocaïne-rémifentanil-thiopental avant l’induction.MéthodeLors d’une étude randomisée et en double aveugle, 76 adultes sains répartis en deux groupes ont reçu : 1,5 mg kg-1 de lidocaïne, 2 μg kg-1 de rémifentanil et 2 mg kg-1 de propofol (Groupe P) ou 1,5 mg kg-1 de lidocaïne, 2 μg kg-1 de rémifentanil et 5 mg kg-1 de thiopental (Groupe T). La laryngoscopie et l’intubation endotrachéale ont été tentées 90 s après l’administration de l’agent hypnotique. Les conditions d’intubation ont été évaluées comme excellentes, bonnes ou pauvres fondées sur la facilité à ventiler, le relâchement de la mâchoire, la position des cordes vocales et la réaction du patient à l’intubation et au gonflement lent du ballonnet trachéal. La tension artérielle moyenne (TAM) et la fréquence cardiaque (FC) ont été mesurées 45 s après l’administration de l’agent hypnotique, immédiatement après l’intubation endotrachéale, deux et cinq minutes après l’intubation.RésultatsDes conditions d’intubation excellentes ont été obtenues chez 84 % des patients du Groupe P et 50 % du Groupe T (P < 0,05). La TAM a été significativement réduite par rapport aux mesures de base, davantage dans le Groupe P que dans le Groupe T après l’induction (27,4 % ± 11,6vs21, 8% ± 10,0) et immédiatement après l’intubation (19,0 % ± 16,7 vs 11,2% ± 14,9). La FC a été modifiée par rapport aux mesures de base, plus dans le Groupe P que dans le Groupe T après l’induction (13,8 % ± 9,7 vs 0,5 % ± 12,4), immédiatement après l’intubation (8,7 % ± 13,7 vs 2,1 % ± 13,1) et deux minutes après l’intubation (7,04% ± 14,3 vs 3,5% ± 14,3).ConclusionLe mélange de lidocaïne-rémifentanil-propofol est supérieur à celui de lidocaïne-rémifentanil-thiopental pour l’intubation endotrachéale sans myorelaxants. Cependant, il induit plus d’hypotension et de bradycardie.

A randomized trial comparing colloid preload to coload during spinal anesthesia for elective cesarean delivery.

BACKGROUND: Hypotension after spinal anesthesia for cesarean delivery is common. Previous studies have demonstrated that a crystalloid fluid “coload” (rapid administration of a fluid bolus starting at the time of intrathecal injection) is superior to the conventional crystalloid preload (fluid administered before the intrathecal injection) for preventing hypotension. Colloid preload provides a sustained increase in central blood volume. We hypothesized that, in contrast to crystalloid, a colloid preload may be more effective than colloid coload for reducing the incidence of spinal anesthesia-induced hypotension. METHODS: In this double-blind study, 178 patients were randomly assigned to receive a preload of 500 mL of hydroxyethyl starch over a period of 15–20 min before initiation of spinal anesthesia (n = 90) or an identical fluid bolus of hydroxyethyl starch starting at the time of identification of cerebrospinal fluid (n = 88). Vasopressors (ephedrine or phenylephrine) were administered if systolic arterial blood pressure decreased less than 80% of the baseline pressure and <100 mm Hg, or with smaller decreases in blood pressure if accompanied by nausea, vomiting, or dizziness. The primary outcome was the incidence of hypotension (defined as the administration of at least one dose of vasopressor). RESULTS: There was no significant difference between the groups in the incidence of hypotension (68% in preload group and 75% in coload group, 95% confidence interval of difference −6%–20%; P = 0.28), doses of ephedrine and phenylephrine, and number of vasopressor unit doses. The incidence of severe hypotension (systolic blood pressure <80 mm Hg) was 16% in the preload group and 22% in the coload group (P = 0.30). There were no differences in the incidence of nausea and/or vomiting, or neonatal outcome between the groups. CONCLUSION: There was no difference in the incidence of hypotension in women who received colloid administration before the initiation of spinal anesthesia compared with at the time of initiation of anesthesia. Both modalities are inefficient as single interventions to prevent hypotension.

Effect of suxamethonium vs rocuronium on onset of oxygen desaturation during apnoea following rapid sequence induction

This study investigates the effect of suxamethonium vs rocuronium on the onset of haemoglobin desaturation during apnoea, following rapid sequence induction of anaesthesia. Sixty patients were randomly allocated to one of three groups. Anaesthesia was induced with lidocaine 1.5 mg.kg−1, fentanyl 2 μg.kg−1 and propofol 2 mg.kg−1, followed by either rocuronium 1 mg.kg−1 (Group R) or suxamethonium 1.5 mg.kg−1 (Group S). The third group received propofol 2 mg.kg−1 and suxamethonium 1.5 mg.kg−1 only (Group SO). The median (IQR [range]) time to reach SpO2 of 95% was significantly shorter in Group S (358 (311–373 [215–430]) s) than in Group R (378 (370–393 [366–420]) s; p = 0.003), and shorter in Group SO (242 (225–258 [189–370]) s) than in both Group R (p < 0.001) and Group S (p < 0.001). When suxamethonium is administered for rapid sequence induction of anaesthesia, a faster onset of oxygen desaturation is observed during the subsequent apnoea compared with rocuronium. However, time to desaturation is prolonged whenever lidocaine and fentanyl precede suxamethonium.

Haloperidol vs. ondansetron for the prevention of postoperative nausea and vomiting following gynaecological surgery

Background and objective: Ondansetron is widely used for the prophylaxis of postoperative nausea and vomiting, while haloperidol is an antiemetic that lacks recent data on efficacy and adverse effects. Methods: In this prospective, randomized, double‐blinded study involving 93 females undergoing gynaecological procedures under general anaesthesia, we compared the efficacy and adverse effects of prophylactic haloperidol 1 mg intravenous and ondansetron 4 mg intravenous vs. placebo. Results: During the overall observation period (0–24 h), in the haloperidol, ondansetron and placebo groups respectively, the incidence of nausea and/or vomiting was 40.7% (11/27), 48.2% (13/27) and 55.5% (15/27), and the need of rescue antiemetics was 22.2% (6/27), 44.4% (12/27) and 40.7% (11/27), with P values >0.05 among the three groups. During the early observation period (0–2 h), in the haloperidol, ondansetron and placebo groups respectively, the incidence of nausea and/or vomiting was 13.7% (4/29), 26.6% (8/30) and 43% (13/30), and the need for rescue antiemetics was 6.8% (2/29), 26.6% (8/30) and 36.6% (11/30). Between haloperidol and placebo groups, the P value was 0.04 for nausea and/or vomiting, and was 0.01 for rescue antiemetics, in addition to lower nausea scores (P = 0.03). During the late observation period (2–24 h), no significant difference was shown among the three groups. Conclusion: The prophylactic administration of 1 mg intravenous haloperidol or 4 mg ondansetron, in female patients undergoing gynaecological surgery, did not improve the overall incidence of nausea and/or vomiting vs. placebo. However, haloperidol 1 mg proved to be an effective antiemetic in the early observation period without significant adverse effects.

A randomized controlled trial of variable rate phenylephrine infusion with rescue phenylephrine boluses versus rescue boluses alone on physician interventions during spinal anesthesia for elective cesarean delivery.

BACKGROUND:Phenylephrine infusion is used to reduce hypotension during spinal anesthesia for cesarean delivery. A prophylactic fixed rate infusion regimen may not improve hemodynamic control; a variable rate regimen adjusted in response to changes in arterial blood pressure and heart rate may allow more accurate maintenance of baseline blood pressure. We hypothesized that a combination of crystalloid solution coload with a variable rate phenylephrine infusion and phenylephrine rescue boluses may be associated with fewer physician interventions needed to maintain maternal systolic blood pressure within 20% of baseline and greater hemodynamic stability than crystalloid solution coload with phenylephrine rescue boluses alone. METHODS:In this prospective, double-blind study, 80 patients received a coload with 15 mL/kg lactated Ringer’s solution immediately after the initiation of spinal anesthesia. Patients were randomized to receive a prophylactic variable rate phenylephrine infusion starting at 0.75 &mgr;g/kg/min (group P) or infusion of normal saline (group S). Maternal systolic blood pressure was maintained within 20% of baseline with rescue phenylephrine boluses using a preset algorithm. During the predelivery period, the number of physician interventions (primary outcome), hemodynamic performance, nausea/vomiting, and umbilical cord blood gas values were compared between the groups. RESULTS:One patient from group S was excluded due to protocol violation. Therefore, group P included 40 patients and group S 39 patients. The median (range) number of physician interventions needed to maintain maternal hemodynamics within the target range (0 [0–6] vs 3 [0–9], difference in median: 3, 95% confidence interval of difference: 2–4) and incidence of hypotension (8/40 [20%] vs 35/39 [90%]) were lower in group P compared with group S (P < 0.001). Group P had a higher incidence of hypertension compared with group S (6/40 [15%] vs 0/39 [0%], P = 0.026). The median performance error was closer to baseline (P < 0.001) with a smaller median absolute performance error (P = 0.001) in group P versus group S. In group P, 4/40 (10%) patients had nausea/vomiting compared with 17/39 (44%) in group S (P = 0.001). The number needed to treat was 1.4 women to prevent 1 case of hypotension, and 3 women to prevent 1 case of nausea/vomiting; the rate of hypertension was 1 case per 6.7 women treated. Neonatal outcomes were not different between the 2 groups. CONCLUSION:Prophylactic variable rate phenylephrine infusion and rescue phenylephrine bolus dosing is more effective than relying on rescue phenylephrine bolus dosing with respect to limiting clinician workload and maternal symptoms during spinal anesthesia for cesarean delivery.

A comparison of sevoflurane-propofol versus sevoflurane or propofol for laryngeal mask airway insertion in adults.

In a prospective, randomized study, we investigated the incidence of successful insertion of laryngeal mask airway (LMA) at the first attempt and the incidence of side effects after LMA insertion using the combination of sevoflurane and propofol as compared with either sevoflurane or propofol alone for induction of anesthesia. Eighty-three unpremedicated ASA physical status I–II patients were anesthetized with a single vital capacity breath (VCB) of sevoflurane 8% supplemented with IV propofol 1.5 mg/kg, a single VCB of sevoflurane 8%, or IV propofol 3 mg/kg. The coinduction technique was associated with the most frequent incidence of successful LMA insertion at the first attempt (93.5%) than either sevoflurane alone (46%) or propofol alone (61.5%) (P < 0.001). Propofol-induced induction of anesthesia allowed the fastest insertion of LMA and was associated with the least frequent incidence of postoperative nausea and vomiting. However, this advantage of propofol was offset by a frequent incidence of pain on injection (69%) and the occurrence of movements during insertion of the LMA (50% in the propofol group versus 19% and 26% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.05), as well as a more frequent incidence of apnea (84% in the propofol group versus 7% and 16% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.001). The report shows that induction of anesthesia with sevoflurane-propofol combined provides a frequent incidence of successful LMA insertion at the first attempt that is associated with an infrequent incidence of apnea.

Does ondansetron or granisetron prevent subarachnoid morphine-induced pruritus after cesarean delivery?

BACKGROUND: We compared the efficacy of granisetron and ondansetron for the prevention of subarachnoid morphine-induced pruritus after cesarean delivery. METHODS: The incidence of pruritus was assessed in parturients who were randomly allocated into Group G (granisetron 3 mg IV, n = 45), Group O (ondansetron 8 mg IV, n = 42), and Group S (saline IV, n = 42). RESULTS: The incidence of pruritus was not significantly different among the 3 groups (86.6% in Group S, 83.3% in Group O, and 88% in the Group G). CONCLUSION: Neither prophylactic ondansetron nor granisetron reduced the incidence of subarachnoid morphine-induced pruritus when compared with the saline group.