Improved ventilation-perfusion matching with increasing abdominal pressure during CO(2) -pneumoperitoneum in pigs

Effect of ultrasound-guided lung recruitment manoeuvre on perioperative atelectasis during laparoscopy in young infants: A randomised controlled trial

BACKGROUND

Pneumoperitoneum is a risk factor for perioperative atelectasis in infants. This research aimed to investigate whether lung recruitment manoeuvres guided by ultrasound are more effective for young infants (<3 months) during laparoscopy under general anaesthesia.

METHODS

Young infants (<3 months) undergoing general anaesthesia during laparoscopic surgery (>2 h) were randomised to either conventional lung recruitment (control group) or ultrasound-guided lung recruitment (ultrasound group) once per hour. Mechanical ventilation was started with a tidal volume of 8 mL·kg-1, positive end-expiratory pressure of 6 cm H2O and 40% inspired oxygen fraction. Lung ultrasound (LUS) was performed four times (T1 was performed 5 min after intubation and before pneumoperitoneum set, T2 was performed after pneumoperitoneum, T3 was performed 1 min after surgery, and T4 was performed before being discharged from post-anaesthesia care unit [PACU]) in each infant. The primary outcome was the incidence of significant atelectasis at T3 and T4 (defined by LUS consolidation score ≥ 2 in any region).

RESULTS

62 babies were enrolled in the experiment and 60 infants were included in the analysis. Before the recruitment, atelectasis was similar between infants randomised to the control or ultrasound group at T1 (83.3% vs 80.0%; P = 0.500) and T2 (83,3% vs 76.7%; P = 0.519). The incidence of atelectasis at T3 and T4 were lower in the ultrasound group (26.7% and 33.3%), compared with infants randomised to conventional lung recruitment (66.7% and 70%) (P = 0.002; P = 0.004; respectively).

CONCLUSIONS

Ultrasound-guided alveolar recruitment reduced the perioperative incidence of atelectasis in infants <3 months during laparoscopy under general anaesthesia.

Healthy nonobese bitches maintain acceptable spontaneous ventilation during laparoscopic ovariectomies

OBJECTIVE

To determine whether end-tidal CO2 (Petco2), tidal volume (Vt), inspiratory minute volume (i), and respiratory rate (RR) remain within reference limits for spontaneously breathing dogs undergoing laparoscopic ovariectomy; characterize changes in these variables over time; and record the proportion of dogs requiring mechanical ventilation on the basis of predetermined criteria.

ANIMALS

22 client-owned dogs.

PROCEDURES

Between January and June 2019, dogs were anesthetized for abdominal insufflation (CO2; 10 mm Hg) and laparoscopic ovariectomy. Respiratory variables (Petco2, Vt, i, and RR) were recorded at 5 time points: preinsufflation (T2), immediately after insufflation (T3), immediately after first ovary extraction (T4), immediately after second ovary extraction (T5), and after abdominal deflation (T6). Results for variables were assessed to identify differences with reference limits and between time points.

RESULTS

At all time points (T2 to T6), Petco2 was within or above the reference limit, Vt was below or within reference limits, and i was either within or above reference limits. Significant temporal changes were detected in all recorded parameters. One dog had to be ventilated prior to abdominal insufflation due to inappropriately low Vt (< 6 mL/kg) and was excluded from further analysis. One of the 21 remaining dogs required rescue ventilation.

CLINICAL RELEVANCE

Following insufflation, there was a tendency toward inadequate ventilation over time characterized by increased Petco2. Twenty of 21 dogs maintained Petco2 within tolerance via a mild increase in RR and did not require assisted ventilation. Dogs undergoing short surgeries may not require assisted ventilation. Clinicians are advised to monitor for hypercapnia and be prepared to assist ventilation if required.

Lung ultrasound score to determine the effect of fraction inspired oxygen during alveolar recruitment on absorption atelectasis in laparoscopic surgery: a randomized controlled trial

Background

Although the intraoperative alveolar recruitment maneuver (RM) efficiently treats atelectasis, the effect of Fio₂ on atelectasis during RM is uncertain. We hypothesized that a high Fio₂ (1.0) during RM would lead to a higher degree of postoperative atelectasis without benefiting oxygenation when compared to low Fio₂ (0.4).

Methods

In this randomized controlled trial, patients undergoing elective laparoscopic surgery in the Trendelenburg position were allocated to low- (Fio₂ 0.4, n = 44) and high-Fio₂ (Fio₂ 1.0, n = 46) groups. RM was performed 1-min post tracheal intubation and post changes in supine and Trendelenburg positions during surgery. We set the intraoperative Fio₂ at 0.4 for both groups and calculated the modified lung ultrasound score (LUSS) to assess lung aeration after anesthesia induction and at surgery completion. The primary outcome was modified LUSS at the end of the surgery. The secondary outcomes were the intra- and postoperative Pao₂ to Fio₂ ratio and postoperative pulmonary complications.

Results

The modified LUSS before capnoperitoneum and RM (P = 0.747) were similar in both groups. However, the postoperative modified LUSS was significantly lower in the low Fio₂ group (median difference 5.0, 95% CI 3.0–7.0, P < 0.001). Postoperatively, substantial atelectasis was more common in the high-Fio₂ group (relative risk 1.77, 95% CI 1.27–2.47, P < 0.001). Intra- and postoperative Pao₂ to Fio₂ were similar with no postoperative pulmonary complications. Atelectasis occurred more frequently when RM was performed with high than with low Fio₂; oxygenation was not benefitted by a high-Fio_2.

Conclusions

In patients undergoing laparoscopic surgery in the Trendelenburg position, absorption atelectasis occurred more frequently with high rather than low Fio₂. No oxygenation benefit was observed in the high-Fio₂ group.

Trial registration

ClinicalTrials.gov, NCT03943433. Registered 7 May 2019,

Neuromuscular blockade of atracurium in permissive hypercapnic versus normocapnic swine undergoing laparoscopy

Neuromuscular blocking agents (NMBAs) are commonly used in experimental laparoscopy in swine undergoing carbon dioxide pneumoperitoneum. Hypercapnia may be present and may prolong NMBAs’ pharmacologic activity. The aim of this study is to evaluate the effect of permissive hypercapnia on the neuromuscular blockade of atracurium in swine. Six Large White swine weighing 30.5 ± 1.6 kg were sedated with intramuscular ketamine and medetomidine, after which anaesthesia was induced with propofol and maintained with sevoflurane. Atracurium 0.4 mg/kg was administered intravenously and the neuromuscular block monitored by acceleromyography during normocapnic and hypercapnic conditions (PaCO₂ range 35–45 mmHg and 60–70 mmHg, respectively). Onset time and time to reach a train of four ratio (TOFR) of 0.7 and 0.9 were recorded. Cardiorespiratory parameters, electrolytes and acid-base status were measured under both conditions. Onset time was similar between the two conditions. Time to reach a TOFR of 0.7 and 0.9 (duration of the neuromuscular block) was longer in hypercapnic compared to normocapnic animals being 1325 ± 300 vs 855 ±111 (p = 0.002) and 1823 ± 434 vs 1218 ± 210 seconds (p = 0.005), respectively. Three hypercapnic swine had a TOF count of 2 and 1 instead of a count of 4 with fade. Permissive hypercapnia was associated with a decrease in pH from 7.444 ± 0.039 to 7.257 ± 0.025 (p < 0.001). No differences were observed for heart rate, end-tidal concentration of sevoflurane, body temperature and arterial haemoglobin saturation. Nonetheless, hypercapnic swine had a statistically significant increase in mean arterial pressure (p = 0.020) and plasma potassium concentration (p = 0.003). The values of PaCO₂ achieved during hypercapnia were well tolerated in swine undergoing CO₂ pneumoperitoneum for laparoscopy. Permissive hypercapnia increased the duration of the atracurium effect and caused an increase in the intensity of the neuromuscular block in few swine.

Preserved oxygenation in obese patients receiving protective ventilation during laparoscopic surgery: a randomized controlled study

BACKGROUND

Venous admixture from atelectasis and airway closure impedes oxygenation during general anaesthesia. We tested the hypothesis that continuous positive airway pressure (CPAP) during pre-oxygenation and reduced fraction of inspiratory oxygen (FIO2 ) during emergence from anaesthesia can improve oxygenation in patients with obesity undergoing laparoscopic surgery.

METHODS

In the intervention group (n = 20, median BMI 41.9), a CPAP of 10 cmH2 O was used during pre-oxygenation and induction of anaesthesia, but no CPAP was used in the control group (n = 20, median BMI 38.1). During anaesthesia, all patients were ventilated in volume-controlled mode with an FIO2 of 0.4 and a positive end-expiratory pressure (PEEP) of 10 cmH2 O. During emergence, before extubation, the control group was given an FIO2 of 1.0 and the intervention group was divided into two subgroups, which were given an FIO2 of 1.0 or 0.31. Oxygenation was assessed perioperatively by the estimated venous admixture (EVA).

RESULTS

The median EVA before pre-oxygenation was about 8% in both groups. During anaesthesia after intubation, the median EVA was 8.2% in the intervention vs. 13.2% in the control group (P = 0.048). After CO2 pneumoperitoneum, the median EVA was 8.4% in the intervention vs. 9.9% in the control group (P > 0.05). One hour post-operatively, oxygenation had deteriorated in patients given an FIO2 of 1.0 during emergence but not in patients given an FIO2 of 0.31.

CONCLUSIONS

A CPAP of 10 cmH2 O during pre-oxygenation and induction, followed by PEEP after intubation, seemed to preserve oxygenation during anaesthesia. Post-operative oxygenation depended on the FIO2 used during emergence.

Influence of abdominal pressure on respiratory and abdominal organ function

PURPOSE OF REVIEW

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been realized as severe complications in the intensive care patient. Laparoscopic surgery in older and more obese patients increases the risk of IAH and ACS.

RECENT FINDINGS

The incidence of IAH may be larger than thought of being approximately one-third of mechanically ventilated intensive care patients. In shock/trauma, three-fourths of all patients may suffer from IAH. Kidney and liver may dysfunction and the gut barrier may be impeded, permitting spread of inflammation to other organs. IAH and ACS have an impact on respiratory mechanics and may impede ventilation and require higher ventilation pressures than under normal conditions. Prone position and alternating (asynchronous) ventilation may moderate the IAH. In addition, surgical decompression should be considered.

SUMMARY

In view of the frequent occurrence of IAH in intensive care, the need of better understanding of the mechanisms behind IAH is a prerequisite for better treatment. Respiratory mechanics are affected but may also indicate routes of ventilatory treatment to lower IAH.