Adverse ventilatory strategy causes pulmonary-to-systemic translocation of endotoxin

Accumulating evidence strongly suggests that ventilatory strategy has an important impact on development of lung injury and patient outcome. Adverse ventilatory strategies have been shown to cause release of pulmonary-derived cytokines and may permit bacterial translocation from the lung to the systemic circulation. Because endotoxin is a potent and clinically important stimulant of cytokine-mediated systemic inflammatory responses that can lead to multiorgan failure, we investigated the effects of ventilatory strategy on lung-to-systemic translocation of endotoxin. We studied the effects of protective (tidal volume [VT] 5 ml. kg(-)(1), positive end-expiratory pressure [PEEP] 10 to 12.5 cm H(2)O) versus nonprotective (VT 12 ml. kg(-)(1), PEEP zero) ventilatory strategy on translocation of endotracheally instilled endotoxin. Anesthetized New Zealand White rabbits were subjected to saline lung lavage, and 32 were randomized to one of four groups: PS (protective ventilation + instilled saline); PE (protective ventilation + instilled endotoxin); NS (nonprotective ventilation + instilled saline); NE (nonprotective ventilation + instilled endotoxin), and ventilated for 3 h. Plasma endotoxin levels increased significantly in the NE group, and remained low and unchanged in the other groups. Peak levels of plasma tumor necrosis factor-alpha (TNF-alpha) were higher in NE versus other groups. Pa(O(2)) and mean arterial pressure (Pa) were lowest, and requirement for pressor and bicarbonate support greatest, in the NE group. Finally, plasma endotoxin levels were significantly greater in eventual nonsurvivors than survivors. These data provide convincing evidence for pulmonary translocation of lung-derived endotoxin. This translocation depends on ventilatory strategy, and suggests a pathophysiologic link between ventilatory strategy and outcome.

Oliguria during corrective spinal surgery for idiopathic scoliosis: the role of antidiuretic hormone

Patients undergoing surgery for idiopathic scoliosis were studied to determine the incidence and aetiology of oliguria during the perioperative period and to evaluate the efficacy of low dose dopamine in preventing its occurrence. Thirty patients, aged 6-18 years undergoing elective surgery were studied. Anaesthesia was standardized. Patients were randomized to receive either dopamine infusion (3 micrograms.kg-1.min-1) (Group A) (n = 15) or dextrose infusion (control) (Group B) (n = 15). Serum and urinary electrolytes and osmolalities and serum antidiuretic hormone (ADH) concentrations were measured. Urine output and haemodynamic parameters were recorded. Intraoperative oliguria occurred in 7% of patients in Group A and 47% in Group B (P < 0.05). Postoperative oliguria occurred in 20% of patients in Group A and 47% in Group B (P > 0.05). Urine and serum biochemical analysis revealed a statistically significant decrease in serum sodium and osmolality (P < 0.005) and an increase in urinary sodium and osmolality in both groups. Serum ADH concentrations were increased in both groups (P < 0.05), returning to baseline 18 h postoperatively. We conclude that oliguria during corrective spinal surgery occurs in association with excess ADH secretion as opposed to perioperative hypovolaemia. Dopamine increases urine output in the perioperative period but does not prevent the release of ADH and its subsequent biochemical effects.

Morbidity outcome in patients with hypertrophic obstructive cardiomyopathy undergoing cardiac septal myectomy: early-extubation anesthesia versus high-dose opioid anesthesia technique

OBJECTIVE

Anesthetic management of patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing septal myectomy is challenging. The morbidity outcome of early-extubation anesthesia (EEA), or fast tracking, versus high-dose opioid (HDO) anesthesia was studied.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred seventy-five cardiac septal myectomy patients (EEA, n = 53; HDO, n = 122).

INTERVENTIONS

EEA technique consisted of low-dose fentanyl, 10 to 15 microg/kg; propofol infusion; midazolam; and inhalation agent. HDO technique consisted of fentanyl, 50 to 100 microg/kg, and benzodiazepines, with or without an inhalation agent. Demographic data, preoperative symptoms, and data on anesthesia management and postoperative complications were recorded.

MEASUREMENTS AND MAIN RESULTS

There were no differences between the groups (EEA v HDO, respectively) regarding age, sex, preoperative symptoms (dyspnea, 89% v 79%; palpitations, 28% v 26%; angina, 47% v 61%; syncope, 47% v 41%), redo surgery, or combined surgery. Mean +/- standard deviation time to tracheal extubation was 7.2 +/- 5.3 hours in EEA versus 19.4 +/- 10.5 hours in HDO patients (p < 0.0001). Intensive care unit (ICU) stay was significantly shorter in EEA versus HDO patients (2.2 v 3.0 days; p < 0.005), with the trend toward earlier hospital discharge (9.7 v 11.3 days; p = 0.09). There was a high requirement for temporary pacing in both groups immediately postoperatively (EEA, 60% v HDO, 48%; p > 0.08). Permanent pacemaker insertion postoperatively was required in 7 of 53 patients (13%) in the EEA group and 11 of 122 patients (9%) in the HDO group (p > 0.25). Atrial arrhythmias occurred postoperatively in 25% of EEA patients versus 34% of HDO patients (p > 0.08).

CONCLUSION

EEA facilitates earlier tracheal extubation by 12 hours in patients with HOCM undergoing septal myectomy, significantly shortening ICU stay by 1 day without increasing perioperative cardiac morbidity or mortality.

Hypercapnic acidosis may attenuate acute lung injury by inhibition of endogenous xanthine oxidase

Relative hypoventilation, involving passively-or "permissively"-generated hypercapnic acidosis (HCA), may improve outcome by reducing ventilator-induced lung injury. However, the effects of HCA per se on pulmonary microvascular permeability (Kf,c) in noninjured or injured lungs are unknown. We investigated the effects of HCA in the isolated buffer-perfused rabbit lung, under conditions of: (1) no injury; (2) injury induced by warm ischemia-reperfusion; and (3) injury induced by addition of purine and xanthine oxidase. HCA (fraction of inspired carbon dioxide [FICO2] 12%, 25% versus 5%) had no adverse microvascular effects in uninjured lungs, and prevented (FICO2 25% versus 5%) the increase in Kf,c following warm ischemia-reperfusion. HCA (FICO2 25% versus 5%) reduced the elevation in Kf,c, capillary (Pcap), and pulmonary artery (Ppa) pressures in lung injury induced by exogenous purine/xanthine oxidase; inhibition of endogenous NO synthase in the presence of 25% FICO2 had no effect on Kf,c, but attenuated the reduction of Pcap and Ppa. HCA inhibited the in vitro generation of uric acid from addition of xanthine oxidase to purine. We conclude that in the current models, HCA is not harmful in uninjured lungs, and attenuates injury in free-radical-mediated lung injury, possibly via inhibition of endogenous xanthine oxidase.

Repair of ventricular septal defect in a child with severe pulmonary hypertension--response to inhaled nitric oxide

Nitric oxide (NO), was administered successfully, to a child with severe pulmonary hypertension, following surgical repair of a large ventricular septal defect. Inhalation of NO, 20-25 parts per million (ppm) was continued for 24 h, resulting in mean pulmonary artery pressure (PAP) of 25 mmHg and permitting a reduction in both ventilatory and inotropic support. Weaning of NO was commenced. At 5 ppm, administration was discontinued. An immediate and dramatic increase in PAP occurred. A similar pattern resulted on further attempts, demonstrating the extreme sensitivity of the pulmonary vasculature to the effects of inhaled low dose NO and the selectivity of the response.

Primary congenital pulmonary hypoplasia--genetic component to aetiology

Primary congenital pulmonary hypoplasia, defined as congenital pulmonary hypoplasia occurring in the absence of other congenital anomalies, is an exceedingly rare condition of unknown aetiology. We report on two cases that presented as severe progressive respiratory failure immediately after birth in siblings of a consanguinous marriage, and we postulate that a genetic aetiology may be responsible for the arrest of lung maturation in utero. The possibility of a genetic component to the aetiology has not been previously documented in the literature.

Humidification reduces coughing and breath-holding during inhalation induction with isoflurane in children

PURPOSE

Inhalation induction using isoflurane is associated with airway irritability, coughing, breath-holding and laryngospasm. These complications are more common in children. This study was designed to determine if humidification of isoflurane in oxygen/nitrous oxide would reduce respiratory complications and hypoxic episodes at induction.

METHODS

Fifty-nine unpremedicated children, aged three months to 12 yr, were enrolled in the study and randomised to receive either humidified isoflurane (n = 27, Group A), or non-humidified isoflurane (n = 32, Group B). All inductions of anaesthesia were with isoflurane 4% in 50% oxygen/nitrous oxide. Subjects were observed for the occurrence of breath-holding, coughing, laryngospasm, bronchospasm, secretions, and hiccoughs. The severity of each complication was graded on a scale of 0-3. The need to administer 100% oxygen and/or succinylcholine was also identified.

RESULTS

Coughing (33% vs 53%) was more frequent in Group B (P < 0.05). Coughing severity scores (13 vs 36) and breath-holding severity scores (8 vs 19) were also greater in Group B (P < 0.05). A change in FIO2 was required more frequently in Group B (4% vs 16%). Although there was a high incidence of laryngospasm in both groups (52% vs 59%), no other differences were identified, breath-holding (26% vs 31%), secretions (30% vs 31%), hiccough (11% vs 12.5%) (P > 0.05).

CONCLUSION

Humidification of inspired isoflurane reduces the frequency and severity of coughing, the severity of breath-holding, and the need to increase supplemental inspired oxygen concentration, when isoflurane is used for inhalation induction of anaesthesia in children. Humidification has no effect, however, on the frequency and severity of laryngospasm, or on the frequency of occurrence of arterial oxygen desaturation.

Analgesia after otoplasty: regional nerve blockade vs local anaesthetic infiltration of the ear

PURPOSE

Children scheduled to undergo otoplasty experience severe pain postoperatively. Nausea and vomiting is also a problem. This study was designed to compare two analgesic techniques (i) regional nerve blockade (ii) local anaesthetic infiltration, with respect to quality and duration of analgesia, opioid requirements and the incidence of postoperative nausea and vomiting (PONV).

METHODS

Forty three children, ASA I-II, aged 3-15 yr, were studied and followed for 24 hr postoperatively. Patients were randomised into two groups. Patients in Group A received local infiltration with lidocaine 1% with adrenaline 1:200,000 0.4 ml.kg-1 (n = 21). Patients in Group B (n = 22) received nerve blockade, bupivacaine 0.5%, 0.4 ml.kg-1. No other form of analgesia was used intraoperatively. Quality and duration of analgesia were assessed using pain and sedation scores recorded by a blinded observer at 0, 5, 10, 15, 30, 45 min with Recovery Room, and at 0, 30, 60, 90, 120, 180, 240, 360, 480 min on the ward. Pain score > 6 was treated with fentanyl 1 microgram.kg-1 iv (recovery) and morphine 0.2 mg.kg-1 im or mefenamic acid 8 mg.kg-1 po on the ward. Time to first supplemental analgesia was noted. Mean duration of analgesia was 8.6 (1.1-24) hr, Group A and 10.5 (1.3-24) hr, Group B (P > 0.7). 24% per cent of children (Group A) and 27% (Group B) required no supplemental analgesia (P > 0.6). The degree of pain control resulted in a low requirement for opioids, Group A: 24%, Group B: 14% (P:NS). The overall incidence of PONV was 43% (Group A) and 36% (Group B) (P:NS): PONV correlated with opioid use. There were no differences between the groups with regard to pain/sedation scores, quality/duration of analgesia, opioid requirements and incidence of PONV.

CONCLUSION

Both techniques provided excellent postoperative analgesia. Lidocaine 1% infiltration (adrenaline 1:200,000) has the added advantage of improving surgical field and haemostasis. Thus, we advocate use of the simpler technique.

Premedication for ambulatory surgery in preschool children: a comparison of oral midazolam and rectal thiopentone

Seventy five ASA 1 and 2 children, aged between six months and five years were randomized to receive oral midazolam 0.5 mg.kg-1, rectal thiopentone 35 mg.kg-1 or no premedication to compare the safety and efficacy of, and parental attitudes to, both premedicants. Cardio-respiratory variables were from the time of premedication to awakening from anaesthesia. In addition, anxiety and sedation scores and patients' acceptance of both premedicant and mask at induction, were all recorded using four-point rating scales. Times to recovery and discharge, and parental satisfaction with the premedication their child had received were also recorded. Children receiving rectal thiopentone had higher sedation scores and were more accepting of the mask than were the other two groups (P < 0.001). Their acceptance of the premedication was similar to that of the midazolam group. Times to spontaneous eye opening and discharge were longer in the thiopentone group (P < 0.005). Parental preoperative satisfaction rating was higher for thiopentone, but not midazolam, than no premedication (P < 0.05). When asked their premedication preferences for subsequent general anaesthetics, a higher proportion of parents whose children were not premedicated requested an alternative regimen (P < 0.01). In conclusion the study found that premedication with rectal thiopentone provided superior induction characteristics to oral midazolam, but with a longer recovery period.